This article discusses a radio-frequency based method for detecting high-frequency circulating bearing currents in electric machines. The method has previously been used to detect discharge bearing currents, which produce energy bursts that can be detected. The article shows that the method can also detect circulating bearing currents, which were previously thought to involve purely resistive currents without discharges. Detecting these currents provides additional insight into when current conduction begins in the bearings. The results contribute to understanding the electric characteristics of bearings and the applicability of radio-frequency detection to all types of inverter-induced bearing currents.
This document summarizes several saliency-based soft sensor techniques for estimating the rotor position of permanent magnet synchronous machines (PMSMs) without using mechanical sensors. It describes the INFORM method, which estimates position from measured inductance variations caused by injected high-frequency currents. It also discusses estimating position from the difference in current peaks produced by injected positive and negative voltage pulses. Finally, it provides details on estimating position using a rotating high-frequency voltage injection and extracting information from the inverse component of the resulting stator currents.
The document is a report on a study tour to OPTCL (Odisha Power Transmission Corporation Limited) submitted by 4 students. It provides an overview of the tour activities including an interactive classroom session covering electrical power transmission and distribution systems. It then describes the field visit where students observed and learned about various transmission equipment such as capacitive voltage transformers, current transformers, wave traps, isolators, circuit breakers and surge arresters.
Design of Active Filter for Reducing Harmonic Distortion in Distribution Networkijtsrd
Power transmission and distribution systems are designed for operation with sinusoidal voltage and current waveform in constant frequency. Power electronic control devices due to their inherent non linearity draw harmonic and reactive power form the supply mains. The wide use power electronic equipment with linear load causes an increasing harmonics distortion in the ac mains currents. Harmonics component is a very serious and harmful problem in the distribution system. The main adverse effects of harmonic current and voltage on power system equipment are overheating, overloading, perturbation of sensitive control and electronic equipment, capacitor failure, communication interferences, process problem, motor vibration, resonances problem and low power factor. This paper describes the modelling of active filter with synchronous d q reference frame theory for harmonic compensation in distribution systems. The case study is carried out at Hlaingtharyar township distribution system. The model is implemented for harmonic analysis from simulation using a Matlab Simulink with the THD values obtained by practical measurement. Khine Zar Maw "Design of Active Filter for Reducing Harmonic Distortion in Distribution Network" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26663.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/26663/design-of-active-filter-for-reducing-harmonic-distortion-in-distribution-network/khine-zar-maw
A Performance Analysis of Statcom on Distance Protection RelayIJSRD
Legacy Transmission system protection schemes are mainly based on distance relaying. However, performance of distance relay is affected in presence of shunt Flexible AC Transmission System Devices (FACTS) like Static synchronous Compensator (STATCOM) which are mostly used to enhance the transferring capacity of transmission system. The study about the protection system like transmission protection by using Distance Relay Specially mho relay and its zone wise tripping characteristics. The detailed idea about FACTS, type of FACTS, Advantages of FACTS and application of FACTS. For various purpose like power handling capacity by injecting or absorbing reactive power. The STATCOM has adverse effect on protection like distance protection ,distance relay mal-function when STATCOM is connected to the Line, when STATCOM is in fault loop then have a great impact on relay tripping characteristics. Distance relay simulation in MATLAB plays an important role.
This document contains notes from a presentation on waveguides given to the Department of Telecommunication Engineering at the University of Engineering & Technology Peshawar, Mardan Campus. The presentation covered the history of waveguides, common types of waveguides including parallel plate, rectangular, circular and dielectric waveguides. It also discussed electromagnetic field configurations inside waveguides, possible modes of propagation including TEM, TE, TM and hybrid modes, and how the dimensions of a waveguide determine its operating frequency range.
The document summarizes key components and concepts in basic microwave engineering. It discusses waveguides and their operating frequencies based on dimensions. It also describes electric and magnetic fields in rectangular waveguides. Additional components summarized include coaxial to waveguide transitions, choke joints, coupling loops, phase shifters, junctions, tuners, mixers, isolators, circulators, directional couplers, and cavity resonators. Isolators, circulators, and directional couplers are multi-port devices that control the direction of signal propagation with differing levels of attenuation.
The document is a report on the design of a three phase shifter appliance. It includes chapters introducing the project and describing the need for automation in power systems. It lists the components used in the circuit diagram, including operational amplifiers, transistors, relays, zener diodes and other electrical components. The block diagram and circuit diagram are presented and key components like the comparator, zener diode, and p-n junction are described in detail.
This document summarizes several saliency-based soft sensor techniques for estimating the rotor position of permanent magnet synchronous machines (PMSMs) without using mechanical sensors. It describes the INFORM method, which estimates position from measured inductance variations caused by injected high-frequency currents. It also discusses estimating position from the difference in current peaks produced by injected positive and negative voltage pulses. Finally, it provides details on estimating position using a rotating high-frequency voltage injection and extracting information from the inverse component of the resulting stator currents.
The document is a report on a study tour to OPTCL (Odisha Power Transmission Corporation Limited) submitted by 4 students. It provides an overview of the tour activities including an interactive classroom session covering electrical power transmission and distribution systems. It then describes the field visit where students observed and learned about various transmission equipment such as capacitive voltage transformers, current transformers, wave traps, isolators, circuit breakers and surge arresters.
Design of Active Filter for Reducing Harmonic Distortion in Distribution Networkijtsrd
Power transmission and distribution systems are designed for operation with sinusoidal voltage and current waveform in constant frequency. Power electronic control devices due to their inherent non linearity draw harmonic and reactive power form the supply mains. The wide use power electronic equipment with linear load causes an increasing harmonics distortion in the ac mains currents. Harmonics component is a very serious and harmful problem in the distribution system. The main adverse effects of harmonic current and voltage on power system equipment are overheating, overloading, perturbation of sensitive control and electronic equipment, capacitor failure, communication interferences, process problem, motor vibration, resonances problem and low power factor. This paper describes the modelling of active filter with synchronous d q reference frame theory for harmonic compensation in distribution systems. The case study is carried out at Hlaingtharyar township distribution system. The model is implemented for harmonic analysis from simulation using a Matlab Simulink with the THD values obtained by practical measurement. Khine Zar Maw "Design of Active Filter for Reducing Harmonic Distortion in Distribution Network" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26663.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/26663/design-of-active-filter-for-reducing-harmonic-distortion-in-distribution-network/khine-zar-maw
A Performance Analysis of Statcom on Distance Protection RelayIJSRD
Legacy Transmission system protection schemes are mainly based on distance relaying. However, performance of distance relay is affected in presence of shunt Flexible AC Transmission System Devices (FACTS) like Static synchronous Compensator (STATCOM) which are mostly used to enhance the transferring capacity of transmission system. The study about the protection system like transmission protection by using Distance Relay Specially mho relay and its zone wise tripping characteristics. The detailed idea about FACTS, type of FACTS, Advantages of FACTS and application of FACTS. For various purpose like power handling capacity by injecting or absorbing reactive power. The STATCOM has adverse effect on protection like distance protection ,distance relay mal-function when STATCOM is connected to the Line, when STATCOM is in fault loop then have a great impact on relay tripping characteristics. Distance relay simulation in MATLAB plays an important role.
This document contains notes from a presentation on waveguides given to the Department of Telecommunication Engineering at the University of Engineering & Technology Peshawar, Mardan Campus. The presentation covered the history of waveguides, common types of waveguides including parallel plate, rectangular, circular and dielectric waveguides. It also discussed electromagnetic field configurations inside waveguides, possible modes of propagation including TEM, TE, TM and hybrid modes, and how the dimensions of a waveguide determine its operating frequency range.
The document summarizes key components and concepts in basic microwave engineering. It discusses waveguides and their operating frequencies based on dimensions. It also describes electric and magnetic fields in rectangular waveguides. Additional components summarized include coaxial to waveguide transitions, choke joints, coupling loops, phase shifters, junctions, tuners, mixers, isolators, circulators, directional couplers, and cavity resonators. Isolators, circulators, and directional couplers are multi-port devices that control the direction of signal propagation with differing levels of attenuation.
The document is a report on the design of a three phase shifter appliance. It includes chapters introducing the project and describing the need for automation in power systems. It lists the components used in the circuit diagram, including operational amplifiers, transistors, relays, zener diodes and other electrical components. The block diagram and circuit diagram are presented and key components like the comparator, zener diode, and p-n junction are described in detail.
This document discusses ferrite phase shifters. It begins by defining ferrites as magnetic materials used in microwave applications due to their electric and magnetic anisotropy. It then discusses three main types of ferrite phase shifters: latching ferrite phase shifters, dual mode ferrite phase shifters, and rotary field ferrite phase shifters. Latching ferrite phase shifters include twin toroid designs that induce a phase shift by modifying the transmission line propagation constant. Dual mode ferrite phase shifters convert signals to circular polarization to interact with a ferrite rod under a bias field, producing a phase shift. Rotary field ferrite phase shifters rotate a ferrite half-wave plate to produce a phase
PERFORMANCE OF LFAC TRANSMISSSION SYSTEM FOR TRANSIENT STATEijiert bestjournal
This paper deals with the transient performance of a low - frequency ac (20Hz) transmission system for a wind ramp event . The LFAC system is interconnected with the 50Hz grid with a Cycloconverter . The wind power from the offshore is in the form of dc,and is interconnected to the LFAC transmission line with a twelve - pulse thyristor inverter. The graphs of transient response of proposed system parameters are plotted. The circuit model of LFAC system is simulated in MATLAB/SIMULINK.
Corrosion detection under pipe supports using EMAT Medium Range Guided WavesInnerspec Technologies
Corrosion detection under pipe supports is a recurrent problem in petrochemical and other process industries, with limited inspection alternatives due to the lack of immediate access to the corroded area. Long-Range UT (LRUT) has been used for years to inspect inaccessible areas but the large blind zone, limited resolution, and complex interpretation makes it difficult to field for this application.
EMAT-generated Medium-Range UT (MRUT) addresses these limitations and provides a robust and proven solution to the problem. EMAT is a non-contact technique that can generate guided waves without couplant or pressure, and permits scanning the part with a single tranducer on parts without surface preparation. Using a single Shear Horizontal and Lamb wave transducer, EMAT MRUT provides excellent near field resolution (no blind zone) and it can detect defects ten times
smaller than LRUT. EMAT MRUT is easy to field, and requires limited training.
Innerspec Technologies will present the MRUT technique with special focus on practical examples of their experience in the field.
Visit www.innerspec.com
This document presents information on HVDC transmission and FACTS technology. It discusses the advantages and disadvantages of HVDC transmission, including its ability to transmit power over long distances with lower losses compared to AC transmission. It also introduces various FACTS controllers and their advantages in enhancing power flow control and transmission capacity. While FACTS can improve AC system utilization, HVDC may be less expensive for long distance overhead transmission or submarine cables. Both technologies are complementary with HVDC suitable for interconnecting unsynchronized AC systems and FACTS providing added benefits within AC networks.
This document discusses electromagnetic (EM) inspection methods for evaluating the integrity of offshore wire ropes. EM inspections can detect internal defects that are not visible, providing a safer alternative to visual inspection alone. Two EM methods are described: loss of metallic cross-sectional area inspection quantifies corrosion and wear, while localized-flaw inspection detects discontinuities like broken wires. Combined EM and visual inspections along with understanding rope deterioration allows for rational retirement decisions beyond wasteful statutory life policies.
Labview based rf characterization and testing of dual mode phase shiftereSAT Journals
Abstract R.F. characterization of C-band dual mode ferrite phase shifter cannot be done manually due to enormous and huge amount of data. So this paper provides the solution in term of automated procedure for testing of C-band DMPS in LabVIEW(Laboratory Virtual Instrument Engineering Workbench) software. Dual mode phase shifter is currently being used in phased array Radar and WLR (Weapon Locating Radar). The DMPS is in production to realize the exorbitant demand of these radars. The desirable characteristic of phase shifter for phased array radar as differential phase shift, insertion loss, return loss, Hi-low phase difference, insertion phase, Rx-Tx phase can be measured with high accuracy. The output can be presented in any desirable form such as concluded summary form, graphical form and in excel sheet for future reference purposes. Key words – Dual mode phase shifter, LabVIEW, GPIB, VNA, Hi-Low phase difference, Command generator
1. The document discusses various types of equipment and accessories used in power transmission systems including transmission lines, conductors, insulators, busbars, isolators, cross-arms, lightning arrestors, circuit breakers, and transformers.
2. It classifies transmission lines based on length and voltage into short, medium, and long lines and describes common types of line supports including wooden poles, steel poles, RCC poles, and lattice steel towers.
3. The document provides details on conductors such as ACSR and AAAC, insulator types including pin, suspension, and strain, and circuit breaker types such as oil, air blast, SF6, and vacuum.
Power Swing Phenomena and Comparative Study of Its Detection on Transmission ...ijsrd.com
Power systems are subject to a wide range of small or large disturbances during operating conditions. Small changes in loading conditions occur continually. The power system must adjust to these changing conditions and continue to operate satisfactorily and within the desired limits of voltage and frequency. The power system should be designed to survive larger types of disturbances, such as faults, loss of a large generator, or line switching. Certain system disturbances may cause loss of synchronism between a generator and rest of the utility system, or between interconnected power systems of neighboring utilities. If such a loss of synchronism occurs, it is imperative that the generator or system areas operating asynchronously are separated immediately to avoid widespread outages and equipment damage. Here it is described to distinguish between power swing and real fault. It is also discussed recent enhancements in the design of out of step tripping and blocking protection functions that improve the security and reliability of the power system. In addition to that the behavior of distance relay element during power swing and during fault is simulated using MATLAB and SIMULINK simulations.
The document discusses Mohd Abdul Sohail's seminar on high voltage direct current (HVDC) transmission. It introduces HVDC, describes the basic principles and components of HVDC systems. The document compares the cost of HVDC to HVAC transmission and lists several advantages of HVDC, such as its ability to transmit electricity over long distances and interconnect separate power grids. It also notes some disadvantages of HVDC, such as higher costs and need for more maintenance of insulators. The objectives of HVDC control systems are to ensure efficient, stable and flexible operation during normal and abnormal conditions.
This document provides an overview of transmission line theory and microwave transmission lines. It discusses the lumped element circuit model used to model transmission lines and the concept of wave propagation in transmission lines. It also covers different types of transmission lines including microstrip lines, waveguides, and coaxial cables. Key transmission line parameters are defined, such as characteristic impedance, cut-off frequency, and electromagnetic mode. Specific modes and characteristics are described for microstrip lines and rectangular waveguides.
Simulation and analysis of HVDC on MATLAB and PSCADVishal Bhimani
This document describes simulations of an HVDC transmission system using MATLAB and PSCAD software. It discusses simulating an HVDC transmission line on MATLAB, including the dynamic model, block diagram and simulation diagram. It also discusses simulating three-phase harmonic filters and locating faults on an HVDC light electrode line using PSCAD. The document provides details on the type of HVDC links, components, and advantages of HVDC simulation. It aims to introduce how HVDC systems work through various simulations of transmission lines, fault detection, harmonic control and more.
The document discusses the key components of power distribution systems, focusing on distribution substations, the primary distribution system, and secondary distribution. It notes that distribution systems receive power from transmission systems and supply power to customers at lower voltages. The main components include distribution substations for voltage transformation and switching/protection, primary feeders that distribute power radially or in loops, and secondary laterals that supply individual customers.
Fundamentals of microwave communication system and radar systemssabesh chaudhary
This presentation educates about the basics of microwave engineerinng and RADAR engineering which must be valuable for the students of Engineering (EEE, ECE Aeronautical Engg. etc) to get the insight of related subjects.
Analysis of SVPWM for Inverter fed DTC of Induction motor DriveIJSRED
This document analyzes and compares space vector pulse width modulation (SVPWM) and sinusoidal pulse width modulation (SPWM) for controlling an induction motor drive using direct torque control (DTC). It finds that SVPWM reduces harmonic content in voltages and currents compared to SPWM, allowing for higher output voltage. The document simulates an induction motor drive using SVPWM and proportional-integral control in MATLAB/Simulink. The results show SVPWM provides improved torque waveform quality over SPWM and DTC with a PI controller alone.
Monitoring and Control of Power System Oscillations using FACTS/HVDC and Wide...Power System Operation
Power oscillations are a growing concern among power system operators worldwide. Traditionally, the
main countermeasure against dangerous power oscillations has been the installation of power system
stabilizers (PSS). Essentially, the potential for inter-area power oscillations depends on the strength of
the tie lines between different areas and the load on the ties. From a European perspective, with the
anticipated integration of remote renewable energy sources such as offshore wind power from the
North-sea region and solar power from southern Europe or Africa, we can expect the average
transmission distances to grow and consequently also tie line flows. Unless tie lines are also reinforced
we expect more oscillation events in the European grid in the future.
From an operational point of view, it is of high priority to be able to estimate the damping of
oscillatory modes reliably in real-time in order to take appropriate and timely measures in case
damping becomes poor. Recent developments in wide-area phasor monitoring have resulted in a new
power oscillation monitoring algorithm that uses multiple measurements from different locations in
the grid. An equivalent system model of the power grid is estimated in real-time and based on this
model, the damping and frequency as well the activity of oscillatory modes can be determined from
ambient process variations. As basis for this, a wide-area measurement system (WAMS) can provide
time synchronized signals from phasor measurement units (PMUs) that can measure voltage, current
and frequency with adequate accuracy and resolution in time. This paper shows results from pilot
operation of the new application at swissgrid, including recordings from an actual and representative
event in the continental ENTSO-E interconnected power system. This example demonstrates the
performance of the new application as well as provides information about the oscillatory modes
present in the continental ENTSO-E system today.
• Introduction: VSC-HVDC connections
• VSC-HVDC structure and controller
• VSC-HVDC connected OWF frequency control
- Control strategy
- Simulation results
• VSC-HVDC interconnector frequency control
- Control strategy
- Simulation results
• Conclusion and future works
Transformer-Less UPFC for Wind Turbine ApplicationsIJMTST Journal
In this paper, an innovative technique with a new concept of transformer-less unified power flow controller
(UPFC) is implemented. The construction of the conventional UPFC that consists of two back-to-back inverters
which results in complexity and bulkiness which involves the transformers which are complication for
isolation & attaining high power rating with required output waveforms. To reduce a above problem to a
certain extent, a innovative transformer-less UPFC based on less complex configuration with two cascade
multilevel inverters (CMIs) has been proposed. Unified power flow controller (UPFC) has been the most
versatile Flexible AC Transmission System (FACTS) device due to its ability to control real and reactive power
80w on transmission lines while controlling the voltage of the bus to which it is connected. UPFC being a
multi-variable power system controller it is necessary to analyze its effect on power system operation. The
new UPFC offers several merits over the traditional technology, such as Transformer-less, Light weight, High
efficiency, Low cost & Fast dynamic response. This paper mainly highlights the modulation and control for
this innovative transformer-less UPFC, involving desired fundamental frequency modulation (FFM) for low
total harmonic distortion (THD), independent active and reactive power control over the transmission line,
dc-link voltage balance control, etc. The unique capabilities of the UPFC in multiple line compensation are
integrated into a generalized power flow controller that is able to maintain prescribed, and independently
controllable, real power & reactive power flow in the line. UPFC simply controls the magnitude and angular
position of the injected voltage in real time so as to maintain or vary the real and reactive power flow in the
line to satisfy load demand & system operating conditions. UPFC can control various power system
parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the
power system reliability has not been addressed sufficiently yet. Cascade multilevel inverters has been
proposed to have an overview of producing the light weight STATCOM’s which enhances the power quality at
the output levels.When the multilevel converter is applied to STATCOM, each of the cascaded H-bridge
converters should be equipped with a galvanically isolated and floating dc capacitor without any power
source or circuit. This enables to eliminate a bulky, heavy, and costly line-frequency transformer from the
cascade STATCOM. When no UPFC is installed, interruption of either three-phase line due to a fault reduces
an active power flow to half, because the line impedance becomes double before the interruption. Installing
the UPFC makes it possible to control an amount of active power flowing through the transmission system.
Results has been shown through MATLAB Simulink
This document discusses vector control of an 8/6 switched reluctance motor (SRM) using a fuzzy logic controller (FLC). It begins with an introduction to SRM and discusses its construction, operating principle, and mathematical model. It then describes the use of direct torque control (DTC) to regulate the motor's torque output within a hysteresis band by controlling stator flux linkage and speed. The document outlines the development of an FLC for SRM speed control, including defining membership functions and fuzzy rules. Simulation results show waveforms for motor torque, speed, and current outputs indicating speed regulation and low torque ripple. The summary concludes the FLC provides accurate SRM control with fast torque/flux response and lower sampling time
This document discusses ultrasonic motors. It begins with an introduction describing how ultrasonic motors were developed and their advantages over traditional motors at small scales. It then covers key topics such as piezoelectricity, poling, basic principles of operation, construction, types including standing wave and traveling wave motors, driver circuits, control techniques, applications, and advantages/disadvantages. In summary, the document provides an overview of ultrasonic motors, how they work using piezoelectric effects, their construction and operating principles, examples of different types, and their applications and benefits.
This document provides information about RF and microwave engineering:
1. It defines radio frequency as any electromagnetic wave frequency between 3KHz to 300GHz, which includes frequencies used for communications and radar signals. Microwaves are defined as electromagnetic waves between 300MHz to 300GHz.
2. Microwave engineering deals with the design of communication, navigation, and other systems that operate in the microwave frequency range. Key applications discussed include microwave ovens, radar, satellite communication, and TV.
3. Analysis of microwave circuits differs from low frequency circuits as the physical length of components is larger than signal wavelengths. S-parameters are used to relate the amplitude of scattered waves to incident waves in microwave circuit analysis.
Quotes by jm barrie, charles dickens, joseph campbell, margaret mitchell, fri...quoteallthethings
This document promotes a website that shares quotes from famous figures throughout history. The website is called quoteallthethings.com and encourages following them on various social media platforms like Google+, Facebook, Twitter, and Pinterest to access more quotes.
Miguel de Cervantes fue un escritor español conocido principalmente por haber escrito la novela Don Quijote de la Mancha, considerada la primera novela moderna y una de las mejores obras de la literatura universal. El documento presenta varios extractos y frases célebres de Don Quijote que describen al personaje principal, Don Quijote, y su filosofía como caballero andante.
This document discusses ferrite phase shifters. It begins by defining ferrites as magnetic materials used in microwave applications due to their electric and magnetic anisotropy. It then discusses three main types of ferrite phase shifters: latching ferrite phase shifters, dual mode ferrite phase shifters, and rotary field ferrite phase shifters. Latching ferrite phase shifters include twin toroid designs that induce a phase shift by modifying the transmission line propagation constant. Dual mode ferrite phase shifters convert signals to circular polarization to interact with a ferrite rod under a bias field, producing a phase shift. Rotary field ferrite phase shifters rotate a ferrite half-wave plate to produce a phase
PERFORMANCE OF LFAC TRANSMISSSION SYSTEM FOR TRANSIENT STATEijiert bestjournal
This paper deals with the transient performance of a low - frequency ac (20Hz) transmission system for a wind ramp event . The LFAC system is interconnected with the 50Hz grid with a Cycloconverter . The wind power from the offshore is in the form of dc,and is interconnected to the LFAC transmission line with a twelve - pulse thyristor inverter. The graphs of transient response of proposed system parameters are plotted. The circuit model of LFAC system is simulated in MATLAB/SIMULINK.
Corrosion detection under pipe supports using EMAT Medium Range Guided WavesInnerspec Technologies
Corrosion detection under pipe supports is a recurrent problem in petrochemical and other process industries, with limited inspection alternatives due to the lack of immediate access to the corroded area. Long-Range UT (LRUT) has been used for years to inspect inaccessible areas but the large blind zone, limited resolution, and complex interpretation makes it difficult to field for this application.
EMAT-generated Medium-Range UT (MRUT) addresses these limitations and provides a robust and proven solution to the problem. EMAT is a non-contact technique that can generate guided waves without couplant or pressure, and permits scanning the part with a single tranducer on parts without surface preparation. Using a single Shear Horizontal and Lamb wave transducer, EMAT MRUT provides excellent near field resolution (no blind zone) and it can detect defects ten times
smaller than LRUT. EMAT MRUT is easy to field, and requires limited training.
Innerspec Technologies will present the MRUT technique with special focus on practical examples of their experience in the field.
Visit www.innerspec.com
This document presents information on HVDC transmission and FACTS technology. It discusses the advantages and disadvantages of HVDC transmission, including its ability to transmit power over long distances with lower losses compared to AC transmission. It also introduces various FACTS controllers and their advantages in enhancing power flow control and transmission capacity. While FACTS can improve AC system utilization, HVDC may be less expensive for long distance overhead transmission or submarine cables. Both technologies are complementary with HVDC suitable for interconnecting unsynchronized AC systems and FACTS providing added benefits within AC networks.
This document discusses electromagnetic (EM) inspection methods for evaluating the integrity of offshore wire ropes. EM inspections can detect internal defects that are not visible, providing a safer alternative to visual inspection alone. Two EM methods are described: loss of metallic cross-sectional area inspection quantifies corrosion and wear, while localized-flaw inspection detects discontinuities like broken wires. Combined EM and visual inspections along with understanding rope deterioration allows for rational retirement decisions beyond wasteful statutory life policies.
Labview based rf characterization and testing of dual mode phase shiftereSAT Journals
Abstract R.F. characterization of C-band dual mode ferrite phase shifter cannot be done manually due to enormous and huge amount of data. So this paper provides the solution in term of automated procedure for testing of C-band DMPS in LabVIEW(Laboratory Virtual Instrument Engineering Workbench) software. Dual mode phase shifter is currently being used in phased array Radar and WLR (Weapon Locating Radar). The DMPS is in production to realize the exorbitant demand of these radars. The desirable characteristic of phase shifter for phased array radar as differential phase shift, insertion loss, return loss, Hi-low phase difference, insertion phase, Rx-Tx phase can be measured with high accuracy. The output can be presented in any desirable form such as concluded summary form, graphical form and in excel sheet for future reference purposes. Key words – Dual mode phase shifter, LabVIEW, GPIB, VNA, Hi-Low phase difference, Command generator
1. The document discusses various types of equipment and accessories used in power transmission systems including transmission lines, conductors, insulators, busbars, isolators, cross-arms, lightning arrestors, circuit breakers, and transformers.
2. It classifies transmission lines based on length and voltage into short, medium, and long lines and describes common types of line supports including wooden poles, steel poles, RCC poles, and lattice steel towers.
3. The document provides details on conductors such as ACSR and AAAC, insulator types including pin, suspension, and strain, and circuit breaker types such as oil, air blast, SF6, and vacuum.
Power Swing Phenomena and Comparative Study of Its Detection on Transmission ...ijsrd.com
Power systems are subject to a wide range of small or large disturbances during operating conditions. Small changes in loading conditions occur continually. The power system must adjust to these changing conditions and continue to operate satisfactorily and within the desired limits of voltage and frequency. The power system should be designed to survive larger types of disturbances, such as faults, loss of a large generator, or line switching. Certain system disturbances may cause loss of synchronism between a generator and rest of the utility system, or between interconnected power systems of neighboring utilities. If such a loss of synchronism occurs, it is imperative that the generator or system areas operating asynchronously are separated immediately to avoid widespread outages and equipment damage. Here it is described to distinguish between power swing and real fault. It is also discussed recent enhancements in the design of out of step tripping and blocking protection functions that improve the security and reliability of the power system. In addition to that the behavior of distance relay element during power swing and during fault is simulated using MATLAB and SIMULINK simulations.
The document discusses Mohd Abdul Sohail's seminar on high voltage direct current (HVDC) transmission. It introduces HVDC, describes the basic principles and components of HVDC systems. The document compares the cost of HVDC to HVAC transmission and lists several advantages of HVDC, such as its ability to transmit electricity over long distances and interconnect separate power grids. It also notes some disadvantages of HVDC, such as higher costs and need for more maintenance of insulators. The objectives of HVDC control systems are to ensure efficient, stable and flexible operation during normal and abnormal conditions.
This document provides an overview of transmission line theory and microwave transmission lines. It discusses the lumped element circuit model used to model transmission lines and the concept of wave propagation in transmission lines. It also covers different types of transmission lines including microstrip lines, waveguides, and coaxial cables. Key transmission line parameters are defined, such as characteristic impedance, cut-off frequency, and electromagnetic mode. Specific modes and characteristics are described for microstrip lines and rectangular waveguides.
Simulation and analysis of HVDC on MATLAB and PSCADVishal Bhimani
This document describes simulations of an HVDC transmission system using MATLAB and PSCAD software. It discusses simulating an HVDC transmission line on MATLAB, including the dynamic model, block diagram and simulation diagram. It also discusses simulating three-phase harmonic filters and locating faults on an HVDC light electrode line using PSCAD. The document provides details on the type of HVDC links, components, and advantages of HVDC simulation. It aims to introduce how HVDC systems work through various simulations of transmission lines, fault detection, harmonic control and more.
The document discusses the key components of power distribution systems, focusing on distribution substations, the primary distribution system, and secondary distribution. It notes that distribution systems receive power from transmission systems and supply power to customers at lower voltages. The main components include distribution substations for voltage transformation and switching/protection, primary feeders that distribute power radially or in loops, and secondary laterals that supply individual customers.
Fundamentals of microwave communication system and radar systemssabesh chaudhary
This presentation educates about the basics of microwave engineerinng and RADAR engineering which must be valuable for the students of Engineering (EEE, ECE Aeronautical Engg. etc) to get the insight of related subjects.
Analysis of SVPWM for Inverter fed DTC of Induction motor DriveIJSRED
This document analyzes and compares space vector pulse width modulation (SVPWM) and sinusoidal pulse width modulation (SPWM) for controlling an induction motor drive using direct torque control (DTC). It finds that SVPWM reduces harmonic content in voltages and currents compared to SPWM, allowing for higher output voltage. The document simulates an induction motor drive using SVPWM and proportional-integral control in MATLAB/Simulink. The results show SVPWM provides improved torque waveform quality over SPWM and DTC with a PI controller alone.
Monitoring and Control of Power System Oscillations using FACTS/HVDC and Wide...Power System Operation
Power oscillations are a growing concern among power system operators worldwide. Traditionally, the
main countermeasure against dangerous power oscillations has been the installation of power system
stabilizers (PSS). Essentially, the potential for inter-area power oscillations depends on the strength of
the tie lines between different areas and the load on the ties. From a European perspective, with the
anticipated integration of remote renewable energy sources such as offshore wind power from the
North-sea region and solar power from southern Europe or Africa, we can expect the average
transmission distances to grow and consequently also tie line flows. Unless tie lines are also reinforced
we expect more oscillation events in the European grid in the future.
From an operational point of view, it is of high priority to be able to estimate the damping of
oscillatory modes reliably in real-time in order to take appropriate and timely measures in case
damping becomes poor. Recent developments in wide-area phasor monitoring have resulted in a new
power oscillation monitoring algorithm that uses multiple measurements from different locations in
the grid. An equivalent system model of the power grid is estimated in real-time and based on this
model, the damping and frequency as well the activity of oscillatory modes can be determined from
ambient process variations. As basis for this, a wide-area measurement system (WAMS) can provide
time synchronized signals from phasor measurement units (PMUs) that can measure voltage, current
and frequency with adequate accuracy and resolution in time. This paper shows results from pilot
operation of the new application at swissgrid, including recordings from an actual and representative
event in the continental ENTSO-E interconnected power system. This example demonstrates the
performance of the new application as well as provides information about the oscillatory modes
present in the continental ENTSO-E system today.
• Introduction: VSC-HVDC connections
• VSC-HVDC structure and controller
• VSC-HVDC connected OWF frequency control
- Control strategy
- Simulation results
• VSC-HVDC interconnector frequency control
- Control strategy
- Simulation results
• Conclusion and future works
Transformer-Less UPFC for Wind Turbine ApplicationsIJMTST Journal
In this paper, an innovative technique with a new concept of transformer-less unified power flow controller
(UPFC) is implemented. The construction of the conventional UPFC that consists of two back-to-back inverters
which results in complexity and bulkiness which involves the transformers which are complication for
isolation & attaining high power rating with required output waveforms. To reduce a above problem to a
certain extent, a innovative transformer-less UPFC based on less complex configuration with two cascade
multilevel inverters (CMIs) has been proposed. Unified power flow controller (UPFC) has been the most
versatile Flexible AC Transmission System (FACTS) device due to its ability to control real and reactive power
80w on transmission lines while controlling the voltage of the bus to which it is connected. UPFC being a
multi-variable power system controller it is necessary to analyze its effect on power system operation. The
new UPFC offers several merits over the traditional technology, such as Transformer-less, Light weight, High
efficiency, Low cost & Fast dynamic response. This paper mainly highlights the modulation and control for
this innovative transformer-less UPFC, involving desired fundamental frequency modulation (FFM) for low
total harmonic distortion (THD), independent active and reactive power control over the transmission line,
dc-link voltage balance control, etc. The unique capabilities of the UPFC in multiple line compensation are
integrated into a generalized power flow controller that is able to maintain prescribed, and independently
controllable, real power & reactive power flow in the line. UPFC simply controls the magnitude and angular
position of the injected voltage in real time so as to maintain or vary the real and reactive power flow in the
line to satisfy load demand & system operating conditions. UPFC can control various power system
parameters, such as bus voltages and line flows. The impact of UPFC control modes and settings on the
power system reliability has not been addressed sufficiently yet. Cascade multilevel inverters has been
proposed to have an overview of producing the light weight STATCOM’s which enhances the power quality at
the output levels.When the multilevel converter is applied to STATCOM, each of the cascaded H-bridge
converters should be equipped with a galvanically isolated and floating dc capacitor without any power
source or circuit. This enables to eliminate a bulky, heavy, and costly line-frequency transformer from the
cascade STATCOM. When no UPFC is installed, interruption of either three-phase line due to a fault reduces
an active power flow to half, because the line impedance becomes double before the interruption. Installing
the UPFC makes it possible to control an amount of active power flowing through the transmission system.
Results has been shown through MATLAB Simulink
This document discusses vector control of an 8/6 switched reluctance motor (SRM) using a fuzzy logic controller (FLC). It begins with an introduction to SRM and discusses its construction, operating principle, and mathematical model. It then describes the use of direct torque control (DTC) to regulate the motor's torque output within a hysteresis band by controlling stator flux linkage and speed. The document outlines the development of an FLC for SRM speed control, including defining membership functions and fuzzy rules. Simulation results show waveforms for motor torque, speed, and current outputs indicating speed regulation and low torque ripple. The summary concludes the FLC provides accurate SRM control with fast torque/flux response and lower sampling time
This document discusses ultrasonic motors. It begins with an introduction describing how ultrasonic motors were developed and their advantages over traditional motors at small scales. It then covers key topics such as piezoelectricity, poling, basic principles of operation, construction, types including standing wave and traveling wave motors, driver circuits, control techniques, applications, and advantages/disadvantages. In summary, the document provides an overview of ultrasonic motors, how they work using piezoelectric effects, their construction and operating principles, examples of different types, and their applications and benefits.
This document provides information about RF and microwave engineering:
1. It defines radio frequency as any electromagnetic wave frequency between 3KHz to 300GHz, which includes frequencies used for communications and radar signals. Microwaves are defined as electromagnetic waves between 300MHz to 300GHz.
2. Microwave engineering deals with the design of communication, navigation, and other systems that operate in the microwave frequency range. Key applications discussed include microwave ovens, radar, satellite communication, and TV.
3. Analysis of microwave circuits differs from low frequency circuits as the physical length of components is larger than signal wavelengths. S-parameters are used to relate the amplitude of scattered waves to incident waves in microwave circuit analysis.
Quotes by jm barrie, charles dickens, joseph campbell, margaret mitchell, fri...quoteallthethings
This document promotes a website that shares quotes from famous figures throughout history. The website is called quoteallthethings.com and encourages following them on various social media platforms like Google+, Facebook, Twitter, and Pinterest to access more quotes.
Miguel de Cervantes fue un escritor español conocido principalmente por haber escrito la novela Don Quijote de la Mancha, considerada la primera novela moderna y una de las mejores obras de la literatura universal. El documento presenta varios extractos y frases célebres de Don Quijote que describen al personaje principal, Don Quijote, y su filosofía como caballero andante.
Honda y Suzuki son dos importantes marcas japonesas de motocicletas. Suzuki en particular es conocida por su modelo Hayabusa, una motocicleta deportiva muy potente y veloz que es popular para realizar modificaciones y ajustes de rendimiento, conocidos como "tuning", entre los entusiastas de las motos japonesas.
Quotes by lisa schroeder, jeffrey eugenides, jarod kintz, rick riordan, hl me...quoteallthethings
Quotes by lisa schroeder, jeffrey eugenides, jarod kintz, rick riordan, hl mencken, lisa schroeder, charles dickens, jane austen, maggie stiefvater, jarod kintz
A food chain shows direct feeding relationships between plants and animals, beginning with a plant and ending with an animal. A food web depicts the interconnected food chains within an ecosystem, showing the relationships between producers like plants, primary consumers like herbivores, secondary consumers like carnivores, and tertiary consumers at the top of the food chain. The document defines key terms like producers, primary consumers, secondary consumers, omnivores, and tertiary consumers to explain trophic levels and energy transfer through food chains and webs.
Honda y Suzuki son dos importantes marcas japonesas de motocicletas. Suzuki en particular es conocida por su modelo Hayabusa, una motocicleta deportiva muy potente y veloz que es popular para ser modificada y mejorada, o "tuning", por entusiastas motociclistas japoneses.
We have launched Do-It-Yourself crown molding system, with years of wood working experience. This home decoration system is a simple and inexpensive alternatives to quickly dress up your home; and provide a beautiful look that you have always wanted.
Aziz Global Trading is a manufacturer and exporter of interior decorative and utility products based in India. They produce a wide range of decorative lanterns, indoor lanterns, designer lanterns, and other home goods. The company was founded in 2012 and has a manufacturing facility equipped with high-end machines. They source raw materials from reputed vendors and have stringent quality control processes to produce durable, trendy products for the hospitality and home industries.
The document summarizes the history of US legislation authorizing wiretapping and electronic surveillance. It discusses that wiretapping was originally a felony but was ruled legal by the Supreme Court in 1928. The Omnibus Crime Control and Safe Streets Act of 1968, also known as the Wiretap Act, prohibited unauthorized wiretapping but established procedures for law enforcement to obtain warrants. The Electronic Communications Privacy Act of 1986 extended these protections to electronic communications. The USA PATRIOT Act, passed after 9/11, expanded the surveillance capabilities of law enforcement and intelligence agencies.
Quotes by shannon hale gena showalter neil gaiman elisabeth kubler ross rober...quoteallthethings
Quotes by shannon hale gena showalter neil gaiman elisabeth kubler ross robert a heinlein john irving markus zusak shannon hale langston hughes jeaniene frost
The document proposes a robotic system for military purposes that can be remotely controlled and monitored. It consists of a transmitter unit with control switches and a receiver unit mounted on a robot. The robot is equipped with a wireless camera, metal detector, and bomb detector. It uses an AT89S52 microcontroller and Zigbee wireless technology to allow two-way communication and control between the user and robot from a remote location. The system aims to provide remote surveillance and manipulation capabilities to help in warfare and other military operations.
Quotes by david mitchell, richelle mead, jennifer l armentrout, jarod kintz, ...quoteallthethings
Quotes by david mitchell, richelle mead, jennifer l armentrout, jarod kintz, jonathan safran foer, bram stoker, tahereh mafi, chuck palahniuk, sherrilyn kenyon, helen keller
This document provides an overview of optimization techniques. It begins with an introduction to optimization and examples of optimization problems. It then discusses the historical development of optimization methods. The document categorizes optimization problems into convex, concave, and subclasses like linear programming, quadratic programming, and semidefinite programming. It also covers advanced optimization methods like interior point methods. Finally, the document discusses applications of convex optimization techniques in fields such as engineering, finance, and wireless communications.
OPTIMIZATION TECHNIQUES
Optimization techniques are methods for achieving the best possible result under given constraints. There are various classical and advanced optimization methods. Classical methods include techniques for single-variable, multi-variable without constraints, and multi-variable with equality or inequality constraints using methods like Lagrange multipliers or Kuhn-Tucker conditions. Advanced methods include hill climbing, simulated annealing, genetic algorithms, and ant colony optimization. Optimization has applications in fields like engineering, business/economics, and pharmaceutical formulation to improve processes and outcomes under constraints.
This document discusses the use of passive harmonic trap filters called HarmonicGuard filters to meet IEEE 519-1992 harmonic limits. It provides an overview of IEEE 519-1992, which sets limits for both voltage and current harmonics. The document explains key terms used in IEEE 519-1992, particularly Point of Common Coupling (PCC), which is important for determining the proper harmonic limits. It also presents examples to illustrate how to interpret the harmonic limits in IEEE 519-1992 based on the PCC location and other factors.
IRJET- Design a Fuzzy Distance Relay Including STATCOM EffectsIRJET Journal
This document discusses how the presence of a STATic synchronous COMpensator (STATCOM) can negatively impact the performance of a distance relay used to protect transmission lines. The authors use MATLAB/PSAT to model a sample power system with a transmission line protected by a distance relay. They simulate faults on the line with and without a STATCOM present and observe how the STATCOM causes issues like under-reach and over-reach for the relay. To address this, they propose designing a new fuzzy logic-based distance relay that accounts for the effects of STATCOM compensation to more accurately detect faults.
Fault identification in transformer windingeSAT Journals
This document discusses fault identification in transformer windings during impulse testing. It presents an analysis of transformer winding current waveforms using both time-domain and frequency-domain (Fast Fourier Transform) methods to classify insulation failures. Simulation results are shown for a range of distribution transformer models with different fault types created at various locations. The proposed approach is applied to an analog model of a 12kVA single-phase transformer, with faults detected by analyzing the neutral currents under applied low voltage impulses.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document reviews approaches for detecting high impedance faults (HIFs) in electric distribution systems from 1960 to 2008. It surveys over 225 papers and classifies detection methods. Early approaches relied on measuring phase or neutral current/voltage, but HIFs produce low currents that conventional protection cannot detect. Later approaches analyze signal characteristics like low-order harmonics, sub-harmonics, high-frequency content, and randomness to identify HIFs. Feature extraction methods are needed due to time-varying nature of HIF signals. The review concludes by comparing methods and providing tables/graphs of each approach's frequency over time.
Inrush current reduction in three phase power transformer by using prefluxing...IAEME Publication
This document discusses reducing inrush current in power transformers. It begins by introducing transformers and explaining that inrush current can be up to 10 times the nominal current and cause issues. One method to reduce inrush current is point-on-wave switching, which controls energization based on residual flux. However, measuring residual flux is difficult. The paper proposes a prefluxing technique which sets the initial flux in the transformer before energization using controlled switching. It models a 300MVA, 11/400kV transformer in MATLAB and compares inrush current reduction using point-on-wave switching and prefluxing. The aim is to minimize the peak inrush current and reach steady state current faster.
This document discusses power quality issues related to harmonics. It covers:
- The causes of harmonics from non-linear loads like switched mode power supplies, electronic ballasts, variable speed drives, and UPS units.
- The effects of harmonic currents within electrical systems, including neutral conductor overheating, transformer overheating, circuit breaker tripping, and capacitor stress.
- Harmonic voltages can also cause problems like voltage distortion, issues with induction motors, and zero-crossing noise.
- Harmonic currents on the supply system can also cause problems that require separate solutions from those used within an installation.
The document provides an outline of harmonics and multilevel inverters. It discusses how harmonics are generated from inverter-based renewable energy systems and the impacts of harmonics on power systems. It then describes different multilevel inverter topologies that can be used to reduce harmonics, including diode clamped, flying capacitor, and cascaded H-bridge inverters. The diode clamped and flying capacitor topologies use capacitors to generate multiple voltage levels at the output, while the cascaded H-bridge connects individual H-bridge inverters in series to synthesize a stepped waveform. Multilevel inverters are said to reduce harmonic distortion and switching losses compared to traditional two-level inverters.
Lightning protection for overhead distribution linesGilberto Mejía
This document summarizes techniques for lightning protection of overhead power distribution lines. It discusses the types of lightning overvoltages that can occur on medium voltage (MV) and low voltage (LV) networks from direct strikes and indirect strikes. Direct strikes can cause overvoltages over 2000kV, far exceeding insulation levels and causing flashovers. Indirect strikes have lower but still significant voltages and are more common. The document reviews methods to mitigate these overvoltages, including increasing insulation, using grounded shield wires, and installing surge arresters. Shield wires and arresters are most effective at reducing faults from direct strikes, while all methods help reduce faults from indirect strikes.
Third harmonic current minimization using third harmonic blocking transformernooriasukmaningtyas
Zero sequence blocking transformers (ZSBTs) are used to suppress third harmonic currents in 3-phase systems. Three-phase systems where singlephase loading is present, there is every chance that the load is not balanced. If there is zero-sequence current due to unequal load current, then the ZSBT will impose high impedance and the supply voltage at the load end will be varied which is not desired. This paper presents Third harmonic blocking transformer (THBT) which suppresses only higher harmonic zero sequences. The constructional features using all windings in single-core and construction using three single-phase transformers explained. The paper discusses the constructional features, full details of circuit usage, design considerations, and simulation results for different supply and load conditions. A comparison of THBT with ZSBT is made with simulation results by considering four different cases
This document presents a technique for locating faults on double circuit transmission lines using wavelet transform and wavelet modulus maxima. The technique uses traveling wave theory and modal decomposition to transform coupled three-phase voltages and currents into independent modal components. Wavelet analysis is then used to obtain the wavelet transform coefficients of each modal component. The time difference between wavelet modulus maxima peaks of the modal components indicates the fault location. Simulation results demonstrate the validity of the technique for various fault types, locations, resistances, and inception angles. The technique can accurately locate faults using data from a single line terminal.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
White Paper_Induction Motor Dynamics of Fast Bus Transfer_Rev0_26 Dec 2016Daniel Lang, P.Eng.
Daniel Lang, P.Eng. discusses various methods for supervised open transition bus transfer to maintain continuity of critical industrial loads during power source switching. There are two main categories of bus transfer - closed transition (parallel) and open transition. Open transition methods aim to minimize transient torque on induction motors during transfer by interrupting the original source before connecting the new source. Supervised open transition methods like fast, in-phase, and residual voltage transfers monitor conditions to safely reconnect motors before their terminal voltage and phase decay too much from the alternate source. Proper bus transfer supervision is needed to prevent catastrophic damage to motors from excessive transient torque during re-energization.
Cost savings by low-loss distribution transformers in wind power plantsLeonardo ENERGY
Highlights:
* National governments should promote energy-efficient components and provide incentives for energy-efficient measures.
* A European specification for a range of energy-efficient transformers is needed.
* The feasibility to get one EU specification should be studied.
Energy-efficient transformers should be promoted through education of customers.
* An energy-efficient transformer should be given a sensational name.
Protection of 3-Phase Induction Motor Fed from 3-Phase Inverter Using Rogowsk...IRJET Journal
This document presents a technique for protecting an induction motor fed from a three-phase inverter using a Rogowski coil current transducer. The proposed method uses a Rogowski coil to measure the current passing through the inverter switches (IGBTs) in order to protect the switches from overcurrent. The Rogowski coil design and current measurement principle are described. Simulation results using PSIM software show that the Rogowski coil can accurately measure currents and provide protection for the IGBT switches in the inverter system.
Protection of 3-Phase Induction Motor Fed from 3-Phase Inverter Using Rogowsk...IRJET Journal
This document presents a technique for protecting an induction motor fed from a three-phase inverter using a Rogowski coil current transducer. The proposed method uses a Rogowski coil to measure the current passing through the inverter switches (IGBTs) in order to protect the switches from overcurrent. The Rogowski coil design and current measurement principle are described. Simulation results using PSIM software show that the Rogowski coil can accurately measure currents and provide protection for the IGBT switches in the inverter system.
FUNDAMENTALS OF HARMONIC AND APPLIED HARMONICS UNIT 3.pdfMURTHYVENKAT2
This document discusses fundamentals of harmonics and applied harmonics. It defines total harmonic distortion (THD) as a measure of the effective value of harmonic components in a distorted waveform relative to the fundamental. Total demand distortion (TDD) is THD referred to peak demand load current rather than the fundamental. Harmonic distortion is caused by nonlinear devices where current is not proportional to voltage. Common harmonic sources are switch-mode power supplies, fluorescent lighting with magnetic ballasts, adjustable speed drives, DC and AC power converters, arcing devices, and saturable devices like transformers.
This document provides guidelines for performing harmonic analysis studies in industrial electrical power systems. It begins by describing the purpose of harmonic analysis studies, which is to analyze harmonic levels and ensure they comply with standards to avoid equipment issues. It then outlines the main guidelines engineers should follow, including identifying harmonic sources like VFDs and resonance conditions. Finally, it introduces international standards that set limits for harmonic distortions. The guidelines are presented as a comprehensive procedure to help engineers properly conduct harmonic studies.
The document discusses power system harmonics, which are non-sinusoidal currents and voltages that can negatively impact power systems. It defines linear and non-linear loads, explaining that non-linear loads produce harmonic currents. These currents flow through system impedances and result in distorted voltages. Passive and active harmonic mitigation techniques are used to reduce harmonics. Passive techniques include adding series reactors, tuned filters, and using higher pulse converters. Tuned filters divert harmonic currents through a low impedance path. Higher pulse converters like 12-pulse and 24-pulse configurations reduce harmonics by using phase shifting transformers. The document provides detailed explanations and diagrams of various passive harmonic filters and higher pulse converters.
Control of Saturation level in the magnetic core of a welding transformer by ...IJERA Editor
The objective of this paper is to analyse the performances of two controllers such as Hysteresis control (HC) and proportional integral (PI) control to control saturation level in the magnetic core of a welding transformer in a middle-frequency direct current (MFDC) resistance spot welding system(RSWS). It consists of an input converter, welding transformer, and a full-wave rectifier mounted at the transformer secondary. The unequal ohmic resistances of the two transformer’s secondary circuits and the different characteristics of the diodes of output rectifier certainly lead to the magnetic core saturation which, consequently, causes the unwanted spikes in the transformer’s primary current and over-current protection switch-off. The goal is to analyse the performance of both controllers in terms of transients, total harmonic distortion(THD) and variations in primary current and flux in the magnetic core of a welding transformer of highly nonlinear system of RSWS. The simulation study has been done in Matlab/Simulink environment and presented performance analysis. The responses shows that from the aforementioned aspects, proportional integral Controller is the better choice for controlling the saturation level in magnetic core of a welding transformer which is widely used in automobile industry welding system.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
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Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
BÀI TẬP BỔ TRỢ TIẾNG ANH 8 CẢ NĂM - GLOBAL SUCCESS - NĂM HỌC 2023-2024 (CÓ FI...
On radio frequency
1. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/TIA.2013.2296626, IEEE Transactions on Industry Applications
On Radio-Frequency Based Detection of High-Frequency Circulating
Bearing Current Flow
Annette Muetze
Graz University of Technology
8010 Graz, Austria
muetze@tugraz.at
Ville Niskanen
Lappeenranta University
53850 Lappeenranta, Finland
ville.niskanen@lut.fi
Abstract—The possibility of bearing damage caused by
inverter-induced bearing currents in modern variable-speed drive
systems has been well recognised today. Further research is
needed to develop appropriate non-intrusive methods for detection and monitoring of such currents. A radio-frequency based
non-destructive method has been applied to detect discharge
bearing currents. The method is understood to work on the
energy that is radiated in the electric field during the bearing
discharge event. We show that the method is also applicable to
high-frequency circulating bearing currents that have so far been
associated with ohmic bearing characteristics and no discharges
occurring. The analysis and understanding of the applicability
of the method to detect such currents also contributes to further
understanding of the electric characteristics of the bearing,
notably the moment the current conduction begins.
CM
DE
HF
HV
LV
MV
NDE
PD
PE
RF
N OMENCLATURE
Common mode.
Drive-end.
High frequency.
High voltage.
Low voltage.
Medium voltage.
Nondrive-end.
Partial discharge.
Protective earth.
Radio frequency.
I. M OTIVATION
Jero Ahola
Lappeenranta University
53850 Lappeenranta, Finland
jero.ahola@lut.fi
additional cost, and a trade-off has to be made between the
per-default application of a mitigation technique and further
analysis of the bearing currents occurring within a system. The
choice will depend on the overall system, its configuration and
cost, and the application.
It is desirable to further reduce the additional cost and
risk associated with such parasitic currents. Development and
research on bearing current monitoring and diagnosis as well
as on the current-conduction and damage mechanisms within
the bearing will all contribute to this aim.
Today, mostly intrusive techniques are applied to measure
such bearing currents: Commonly, an electrically insulating
layer is introduced into the current path. This electrical insulation is then shortened with a small wire, and the current
flow through the wire measured. Such a method is not suitable
for wide-spread cost-effective application in the field. Furthermore, the measurement circuit affects the measured currents.
While models to conclude on the current flow in the respective
system before modification are available (e.g. [18]), they
only reflect the existing understanding and thus have limited
applicability to enhance the understanding of the current flow
mechanism. Thus, non-destructive methods for the detection
and monitoring of inverter-induced bearing currents may be
considered a great asset towards an even better understanding
of such current flow and possible damage.
A. Bearing Current Research, Monitoring, and Diagnosis
B. Non-intrusive Detection of Inverter-Induced Bearing Currents Under all Operating Conditions
The possibility of bearing damage caused by inverterinduced bearing currents in modern variable-speed drive systems has been well recognised today. Different authors have
described the cause-and-effect chains, allowing the selection
of appropriate mitigation techniques (e.g. [1]–[11]). Notably,
distinction between (a) discharge bearing currents, that are
directly related to the high-frequency (HF) common-mode
(CM) voltage, and (b) HF circulating current that are caused
through inductive coupling by the HF stator CM current and
that are thus more prevalent with machines with larger frame
sizes, is important.
The mitigation techniques are frequently applied as preventative measures to avoid bearing failure. Common approaches
include different types of filters and chokes, inverter modulation schemes that minimize the CM voltage, electrostatic
shielding, slip and shaft grounding rings, and insulated or
hybrid bearings (e.g. [6]–[17]). These techniques come with
A radio-frequency (RF) based non-intrusive method to detect discharge bearing currents has been presented and used
to evaluate and further understand the occurrence of discharge
currents [19]–[21]. The method is based on the understanding
of an electric machine as a spark gap transmitter with some
of the energy stored within the bearing and machine (notably
air gap) before the discharge being emitted as an RF signal.
In contrast to these discharges occurring with discharge
bearing currents, the bearings have so far been understood
to have ohmic properties in the case of HF circulating bearing
currents. Based on this understanding, such currents can
thus not be detected with an RF based method that detects
the electric field in the frequency range radiated from any
discharge, because of the lack of occurrence of a discharge
and subsequent release of energy that can be radiated outside
of the bearing. Note that this possibility of detection is not
related to the maximum amplitude of the bearing current. (HF
0093-9994 (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See
http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
2. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/TIA.2013.2296626, IEEE Transactions on Industry Applications
circulating bearing currents generally have larger amplitudes
than discharge currents.)
To the best of the authors’ knowledge, systematic detection
of flow of HF circulating currents with an RF technique
and occurrence of a discharge along with such currents to
be detected have yet to be shown. Such work would both
show that bearing currents under all operating conditions–i.e.
all types of bearing currents–can be detected using an RF
technique and provide further insight into the moment the
current conduction begins.
vCM
iCM
3
3
-0.6
-0.6
vb
3
-0.6
ib
3
-0.6
II. C ONTRIBUTION
AND
O RGANIZATION
OF
Discharge of voltage
across the bearing
We show that HF circulating bearing currents, too, can
be detected using an RF based non-intrusive method. This
is in contrast to the common understanding of purely ohmic
bearing characteristics when such currents flow. It closes the
gap that only some types of bearing currents have been
shown to be detectable through this technique, and allows RF
based detection of inverter-induced bearing currents under all
operating conditions.
Analyzing HF circulating bearing currents further, we
present results from investigations of the switching instant
during which the HF voltage between the two bearings increases, the bearing lubrication film cannot maintain electrically insulating properties, and HF circulating currents start to
flow. The understanding of the applicability of the RF based
method is tightly coupled with further findings on the electric
characteristics of the bearing, notably the moment the current
conduction begins: We have observed instantaneous capacitive
behavior of the bearings already at low rotational speed and
discharges that can be associated with the subsequent flow of
HF circulating currents.
Experimental results with supporting theoretical considerations are given (Sections V–VIII) following short reviews of
the two HF bearing current mechanisms referred to above, the
RF based method, the test setup and an overview of the types
of tests carried out (Sections III and IV).
ib mirrors iCM
Discharge Bearing
Currents
PAPER
HF circ. Bearing
Currents
Fig. 1. Comparison of discharge and HF circulating bearing current mechanisms: discharge of capacitively coupled CM voltage across the bearing versus
inductive coupling; vCM : CM voltage, iCM : CM current, vb : voltage across
bearing, ib : bearing current.
2) HF circulating bearing currents are caused by inductive
coupling through the HF stator CM current (Figs. 2 and
3). In contrast to the discharge currents, the circulating
currents occur the moment a switching event takes place.
The frequencies of these currents are typically in the
range of a few hundred kilohertz, with the first halfperiod of the oscillation sometimes reaching one to two
megahertz. In general, it is understood that the voltage in
the loop driving the HF circulating current leads to the
bearing lubricating film being “punctured”, the bearing
shows ohmic behavior, and the bearing resistance is
so small that it is usually neglected in the proposed
equivalent circuits.
stator core
stator frame
F0
stator winding
end shield
ib
III. R EVIEW OF HF B EARING C URRENTS AND RF BASED
B EARING C URRENT D ETECTION
A. Review of HF Bearing Currents
The nonzero HF CM voltage at the output of modern
fast-switching inverters typically changes with every inverter
switching instant and arrives at the motor terminals with a high
dv/dt, where it interacts with the HF machine impedance.
Discharge bearing currents are directly caused by the HF
CM voltage, HF circulating bearing currents–which are in the
focus of this paper–by the HF CM current that flows as a result
of this interaction (Fig. 1) (e.g. [1]–[11]):
1) Discharge bearing currents result from the stator winding
HF CM voltage charging the bearings via a capacitive
voltage divider, and occur–statistically distributed–as
discharge current pulses (of up to a few amp` res) when
e
the threshold voltage of the bearings (that depends on
the operating conditions and typically is in the range of
a few up to some tens of volts) is exceeded.
bearing
shaft
rotor core
Fig. 2. Path of HF circulating bearing current [22].
Common mode
current
20 A/Div
Bearing currents
(NDE)
(DE)
5 A/Div
1 ms/Div
Fig. 3. Measured HF circulating bearing currents, induction motor, frame
size 400 mm, 500 kW rated power, motor speed n = 3000 rpm, bearing
temperature θb ≈ 70°C [22].
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3. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
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B. Review of RF Based Bearing Current Detection
The RF based bearing current detection works similarly to
partial discharge (PD) detection in the insulation of electric
machines. This technique has mainly been developed to determine the quality and state of the insulation and prevent its
premature ageing and failure (for a comprehensive reference,
see [23]). While such techniques have long been established
for form-wound high-voltage (HV) and medium-voltage (MV)
machines, with many devices commercially available (e.g.
[24]–[27]), the increased use of power-electronics converters
has also led to such techniques being developed for detection
of PD in random-wound, low-voltage (LV) windings (e.g.
[28]–[32]). Earlier techniques, notably for the HV and MV
machines were designed for offline application, with the rotor
removed to increase the confidence in the signals, but methods
for online detection have found recent interest, notably in the
context of PD occurring with converter-fed, LV machines.
As for discharge bearing currents, it has been shown that
a fraction of the energy released during the discharge is
radiated outside from the electric motor and can be detected
as RF electric field measurement by appropriate equipment
[19], [20]. In this case, the machine itself operates as a spark
gap transmitter. The characteristics of the RF radiation (e.g.
power, frequency range, radiation pattern) are determined by
the characteristics of the electrical discharge and those of the
electric machine as the transmitting antenna. The frequency
band of the radiation has been determined to be 90−400 MHz;
the machine shaft end has been shown to play a key role in
the transmitting characteristics [33], and the radiated power,
even though small, is sufficiently large to be detected.
Any antenna tuned to detect electric fields in the identified
frequency range may be used for this technique, although
an antenna with directivity is highly recommended since it
reduces possible effects of external interferences. A device
based on a similar principle can be obtained on the market,
too, [34]. Note that this device detects RF emissions above a
certain threshold. (Determined at 10 mV within our laboratory
tests with a 50 Ω load.) In contrast to direct detection with an
RF antenna, it thus does not provide any further insight into
the strength of the emitted RF signal. Note also that many of
the commercially available devices to detect PD in HV and
MV windings are not suitable for the purpose of detecting
bearing currents, since they are operating in a much higher
frequency range of a few gigahertz.
IV. T EST S ETUP
A. Drive Systems
Two drives with two different power levels and thus frame
sizes are used for the experiments. Both are 230/400 V, 50 Hz,
∆-connected, 4-pole induction motors operated by three-phase
400V, 50 Hz inverters. The two motors and inverters are
referred to as motors MA-15 and MB-75 as well as inverters
IA-15 and IB-75 respectively. MA-15 is a 160 mm frame
size 15 kW, MB-75 a 280 mm frame size 75 kW machine. The
two 400 V inverters are rated at 14.8 A and 82 A respectively.
The smaller inverter is operated at 4 kHz (scalar control,
constant switching frequency), the larger one at 3 kHz (direct
torque control, average switching frequency). Both machines
are grounded through the PE conductor of the motor cable
only. Bearing temperatures during operating were in the range
of ≈ (25 . . . 65)°C.
In order for the bearing currents to be measured, the
bearings of the example case machines are insulated towards
the housing using an electrically insulating layer of 5 mm
thickness applied around the outer bearing race that was shortened with a short wire. As discussed above, this technique is
intrusive and will slightly alter the HF current flow when compared to the unmodified case. Using the techniques presented
in [18], this influence is estimated to reduce the amplitudes
of the HF circulating bearing currents by (-10 . . . 15)% for
MB-75, and by up to 25% for MA-15.
B. Measurement Equipment
The measurement equipment included an EMCO 93148
antenna that has a bandwidth of 200 MHz to 2 GHz and that
was placed at approximately one meter distance from the
motor, pointing towards the motor shaft, a Textronix TDS7140
oscilloscope with a bandwidth of 1 GHz and a maximum sampling rate of 10 GS/s, and an RF bandpass filter Mini-Circuits
BHP100+ with a bandwidth of 90−400 MHz (input impedance
set to 50 Ω). The HF bearing currents on the nondrive-end
(NDE) and drive-end (DE) sides were measured either with
Tektronix TCP202 50 MHz passive (measurements shown in
Figs. 6(a), 6(b), 7(a), 7(b), 9–12) or R&S ZC20 50 MHz
active current probes (measurements shown in Figs. 6(c), 6(d),
7(c), 7(d), 8(a)–8(c)); the voltage across the bearings with
a Tektronix P5210 50 MHz high voltage differential probe
(Figs. 4 and 5). The HF CM currents were measured using an
R&D EZ-17 100 MHz passive current probe. Bearing temperatures were measured using an AZ8868 infrared thermometer
between the shaft and the motor end shield.
C. Types of Tests
Four types of tests are carried out:
I. HF circulating bearing current flow “as is”: The electric
machine is operated at low rotational speed and the
HF circulating bearing currents–if flowing–are detected.
(Section V.)
II. Generation of increased HF circulating bearing current
flow: The NDE bearing and its insulation are shortened
to decrease the impedance of the path of the circulating current. This additional measure decreases the HF
impedance in the path of the HF circulating currents and
the thus the likeliness for these to occur at increased
rotational speed and/or low bearing temperatures. (Section VI.)
III. Bearing currents due to rotor ground currents: The NDE
bearing insulation was again left open. The machine
was grounded via the rotor, i.e. the stator grounding
connection eliminated and the rotor connected to ground
with the help of a sleeve made from the tinned copper
braid of the coaxial shield of the supply cable. In
this configuration, any HF CM current would return to
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4. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
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bearing was externally supplied with a HF voltage within
the frequency range typical for HF circulating bearing
currents using the HF signal generator. (Section VIII.)
For all types of tests, the HF bearing currents, voltage, and
impedance, and RF emission/detection properties are analyzed.
V. R ESULTS I: HF C IRCULATING B EARING C URRENT
F LOW “A S I S ”
A. Experimental Results with Motor MA-15
Because of its small frame size, in line with the scaling laws
for inverter-induced bearing currents, only discharge bearing
currents occurred in this first type of tests and thus measurement results obtained with this machine are not discussed in
this section.
B. Experimental Results with Motor MB-75
Fig. 4. Measurement setup of motor MA-15 (15 kW).
Fig. 5. Measurement setup of motor MB-75 (75 kW).
ground via the rotor grounding connection, thereby passing the DE bearing current. Since HF circulating bearing
currents are generated through inductive coupling of the
HF CM current, these bearing currents have the same
waveforms as HF circulating bearing currents, but larger
amplitudes. (Section VII.)
IV. External supply of HF bearing currents using a Hameg
HM8131-2 15 MHz signal generator: The NDE bearing
insulation was left open: In this configuration, any current flow across the NDE bearing is negligible. The DE
With this machine, HF circulating bearing currents
occurred–along with discharge bearing currents–up to slightly
above 200 rpm rotational speed for lower bearing temperatures
in the range of some (20 . . . 30)°C. Above, only discharge
bearing currents were observed. Maximum amplitudes of
these HF circulating bearing currents reached up to 1.2 A
for 100 rpm. For elevated bearing temperatures above 60°C,
very small HF circulating bearing currents of a few hundred
milliamp` res could be observed up to even 3000 rpm. The
e
HF CM current was measured to approximately 10 A. The
frequency of the HF CM and the bearing currents was in the
range of 1 MHz. As the bearing voltages and currents were
measured, too, the bearing current type could be verified for
any bearing currents detected through the non-intrusive RF
based method.
Conventionally, the HF circulating bearing current has been
understood to flow through the bearing that has mainly ohmic
behavior. During such purely ohmic behavior, there would be
an energy conversion due to ohmic loss within the bearing, but
no energy release as a result of a discharge. However, as shown
in Figs. 6(a)–6(d), also such HF circulating bearing currents
can be detected through the RF based method: The measured
HF bearing currents through the NDE and DE bearings have
the same waveforms and amplitudes and opposite signs, which
is a clear indicator of HF circulating bearing currents. The
moment the currents start to flow, an RF current pulse is
detected. This important finding will be further analyzed
below.
C. Analysis
The detected RF pulse indicates that some energy has been
released and radiated outside the machine the moment the
individual current has started to flow. A detailed consideration
of the voltages measured across the NDE and the DE bearings
shows a relatively steep voltage rise notably in one of the two
bearings (Figs. 6(a) and 6(b): NDE bearing, Figs. 6(c) and
6(d): DE bearing) the moment the current starts to flow. The
voltage and current waveforms are not fully proportional as
one would expect for purely ohmic behavior.
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5. Voltage [V]
Voltage [V]
Current [A]
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/TIA.2013.2296626, IEEE Transactions on Industry Applications
1
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(a) 100 rpm rotational speed and ≈ 30°C bearing temperature.
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(b) 100 rpm rotational speed and ≈ 30°C bearing temperature.
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(c) 400 rpm rotational speed and ≈ 55°C bearing temperature.
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We interpret this as follows: The moment the voltage in the
loop increases, the bearing lubricating film still has electrically
insulating properties. A certain voltage is required for the film
to lose these insulating properties. At a certain threshold, the
bearing(s) start(s) to conduct. In the case of discharge bearing
currents, the energy stored across the bearing(s) is released
instantaneously. In the present case of HF circulating bearing
currents some of this energy is absorbed by the change of the
electrical properties of the bearing. This reduces the bearing
impedance further whereby part of the energy is released and
radiated through the electric machine antenna structure.
With HF bearing currents–in contrast to the case with
discharge bearing currents–both bearings are required to have
electrically conducting properties. As observed in Figs. 6(a)–
6(d), the establishment of the current conducting path might
not be uniformly distributed across the two bearings: One
bearing might first suffer from a steeper voltage rise and
the subsequent voltage breakdown (thereby also releasing
energy that is eventually radiated through the machine antenna
structure) than the other. Note also that, depending on the
drive, some CM capacitive coupling might exist additionally.
Such voltage would add to the differential voltage induced by
the CM current generated HF flux, increasing the latter across
the one and decreasing it across the other bearing before the
HF circulating bearing current flow begins.
The energy released has been computed from the energy
stored in the total capacitance (two bearing capacitances and
one rotor-to frame capacitances) (eqs. (2) and (3) in [20], see
Appendix). The calculated values range between 10 and a few
100 nJ. This is within the lower part of the range of energies
released in the case of discharge bearing currents (between a
few and a few thousands of nanojoules). The latter explains
that the RF signals detected in the case of discharge bearing
currents were typically in the order of 10 mV, whereas those
to detect HF circulating bearing currents were rather in the
range of a few millivolts.
Comparing Figs. 6(a) and 6(b), both show the relatively
steep voltage rise the moment the current starts to flow. The
detected RF pulse is larger for Fig. 6(b) where the voltage rises
faster and higher. However, note that the maximum bearing
current is larger in Fig. 6(a), indicating that the amplitudes of
the bearing current and of the RF pulse might not be strongly
related. The detected HF circulating bearing currents shown in
Figs. 6(c) and 6(d) occur not only at much higher rotational
speed, but also significantly higher bearing temperatures. Here,
much less voltage builds up before the current conducting path
is established resulting in much smaller emitted RF signals.
Voltage [V]
Time (us)
x 10
2
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VI. R ESULTS II: I NCREASED HF C IRCULATING B EARING
C URRENT F LOW
RF
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(d) 1500 rpm rotational speed and ≈ 65°C bearing temperature.
Fig. 6. Motor MB-75 and inverter IB-75: HF circulating bearing current
detected through non-intrusive RF based method; measured currents, voltages
and RF signals.
A. Experimental Results with Motor MA-15
Some flow of HF circulating bearing currents in the smaller
machine could be generated through the decreased impedance
of the bearing current path. With this machine, the preliminary
findings were obtained that indicated the applicability of the
method and that led to further research on the larger machine.
For this reason they are also briefly mentioned in this paper.
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6. VII. R ESULTS III: ROTOR G ROUND C URRENTS
A. Experimental Results with Motor MA-15
With the machine grounded via the rotor instead of the
stator, and the NDE bearing fully insulated, the total HF CM
current of about 8 A and close to 1.5 MHz flows through the
DE bearing (Fig. 8). Here again, similar to the case of “true”
HF circulating bearing currents, the currents flow through
the bearing only after the current conducting path has been
established what brings along an emission of an RF pulse.
Voltage [V]
Voltage [V]
Current [A]
Voltage [V]
Voltage [V]
Current [A]
Voltage [V]
The maximum amplitudes of the HF bearing currents at
very low rotational speed do not increase as the NDE bearing
is shortened, indicating that the influence of the bearing
impedance at this speed, and once HF circulating bearing
currents are flowing, is negligible. However, for a given temperature level, the maximum speed up to which HF circulating
bearing currents were found increased almost by a factor
of two, supporting the understanding that the role of the
bearing impedance increases with increasing motor speed as
the thickness of the lubricating film increases.
Even as the occurrence of the HF circulating bearing currents themselves does increase towards higher rotational speed
and lower bearing temperatures, the detection of these currents
through the RF based method is more difficult with the NDE
bearing shortened. The lack of contribution of radiated energy
from the NDE bearing towards the radiated signal may be
interpreted as one factor contributing to this observed behavior.
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C. Analysis
-1
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x 10
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Current [A]
Maximum amplitudes of the HF circulating bearing currents
reached again up to 1.2 A for 100 rpm and lower bearing temperatures in the range of some (20 . . . 30)°C. Also, very small
HF circulating bearing currents of a few hundred milliamp` res
e
could be observed up to even 3000 rpm for elevated bearing
temperatures above 60°C.
Figs. 7(a)–7(d) show RF based detections of HF circulating
bearing currents 150, 300, 900, and 2000 rpm respectively.
Again, the measured HF bearing currents through the NDE
and DE bearings have the same waveforms and amplitudes
and opposite signs, and an RF current pulse is detected the
moment the currents start to flow.
Inde
Ide
0
(a) 150 rpm rotational speed and ≈ 30°C bearing temperature.
Voltage [V]
B. Experimental Results with Motor MB-75
1
2
Voltage [V]
However, these currents are much more rare with the small
machine, and the energies released were often found to be
so low that RF based detection was difficult. They will thus
not be discussed any further. However, we would like to point
out that this limitation does not impede on the practicability
of the proposed method: With HF circulating bearing currents
typically not occurring with machines with small frame sizes,
but if suffering from HF bearing currents, being put at risk due
to discharge bearing currents, there is no need to detect HF
circulating bearing currents with such machines, and detection
of discharge bearing currents through the RF method has been
well proven.
Current [A]
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/TIA.2013.2296626, IEEE Transactions on Industry Applications
1
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(d) 2000 rpm rotational speed and ≈ 30°C bearing temperature.
Fig. 7. Motor MB-75 and inverter IB-75, NDE bearing shortened: HF
circulating bearing current detected through non-intrusive RF based method;
measured currents, voltages and RF signals.
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7. 2
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Icom [A]
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(a) Measured bearing current, bearing voltage, and RF signal.
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Angle of Zb [deg]
Vb [V]
Ib [A]
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(a) 900 rpm rotational speed and ≈ 35°C bearing temperature.
10
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Vb [V]
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10.1109/TIA.2013.2296626, IEEE Transactions on Industry Applications
0
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(b) Computed bearing impedance.
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Fig. 9. Motor MA-15 and inverter IA-15, external HF voltage supply of DE
bearing: measured currents, voltages and RF signals and computed bearing
impedance for 300 kHz HF supply voltage, 210 rpm rotational speed, and
≈ 30°C bearing temperature; computed bearing capacitance during capacitive
behavior Cb = 0.21 nF.
8
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(b) 1800 rpm rotational speed and ≈ 50°C bearing temperature.
10
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(c) 3000 rpm rotational speed and ≈ 50°C bearing temperature.
Fig. 8. Motor MA-15 and inverter IA-15: Bearing currents due to rotor
ground currents detected through non-intrusive RF based method; measured
currents, voltages, and RF signals.
technique, as the current flow is preceded by the establishment
of a current conducting path that comes along with a change
of the current conducting properties of the bearing and the
emission of an RF pulse.
VIII. R ESULTS IV: E XTERNAL S UPPLY
C URRENTS
OF
HF B EARING
A. Reasoning
For the larger machine, too, bearing currents due to rotor
ground currents with waveforms equivalent to HF circulating
bearing currents could be obtained and detected with the RF
based method. In these cases, the total HF CM current of about
10 A would flow through the DE bearing. (Additional figures
would not add more value and are thus omitted for reasons of
space.)
These tests were carried out to further understand the reason
for the observed behavior. Emphasis was placed on operation
at low rotational speed of a few hundred revolutions per minute
where HF circulating bearing currents are more prevalent and
electrically insulating behavior of the bearing followed by a
discharge occurring within the bearing is less expected. Note
also that even at 1 MHz, the impedance provided by the 5 mm
think electrically insulating layer is in the order of several
kiloohms which is at least by a factor of 103 larger than the
one of the bearing current path. Thus, any current flow across
the NDE bearing is negligible.
C. Analysis
B. Experimental Results with Motor MA-15
With respect to the current conduction mechanism, bearing
currents due to rotor ground currents and HF circulating
bearing currents are very similar, since both are directly related
to the waveform of the HF CM current. Thus, the currents
flowing in this type of test can, too, be detected through the RF
The bearing may form a capacitive film even at low
rotational speed. However, the capacitive behavior does not
exist constantly but changes to ohmic behavior. For example,
Figs. 9 and 10 show the measured DE bearing currents and
voltages, the detected RF signals, as well as the computed
B. Experimental Results with Motor MB-75
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10
0
Ib [A]
-10
0
1
100
150
200
Time (us)
250
300
350
400
0
-10
0
0
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Time (us)
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Time (us)
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-0.2
0
|Zb| [ohm]
|Zb| [ohm]
50
100
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Time (us)
250
300
350
250
300
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400
50
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Time [µs]
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10
2
400
0
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Time (µs)
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Time (µs)
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100
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0
-100
0
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Time (us)
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(b) Computed bearing impedance.
Angle of Zb [deg]
Angle of Zb [deg]
200
Time [µs]
(a) Measured bearing current and bearing voltage.
2
0
150
0
(a) Measured bearing current, bearing voltage, and RF signal.
10
100
400
0
-10
0
50
0.2
50
Ib [A]
-1
0
10
RF [mV]
50
Ub [V]
Vb [V]
10
0
-50
-100
0
(b) Computed bearing impedance.
Fig. 10. Motor MA-15 and inverter IA-15, external HF voltage supply of DE
bearing: measured currents, voltages and RF signals and computed bearing
impedance for 300 kHz HF supply voltage, 300 rpm rotational speed, and
≈ 30°C bearing temperature; computed bearing capacitance during capacitive
behavior Cb = 0.38 nF.
bearing impedances for 300 kHz HF supply voltage and 210
as well as 300 rpm rotational speed: Over a certain time of
some tens of microseconds, the bearing impedance increases
slightly, before it turns mainly capacitive again. Fig. 10 also
shows how such a mode change can occur for only a very
short moment: Following the discharge and change to ohmic
behavior at 30 µs, the impedance increases and turns capacitive
again at around 100 µs, but returns to resistive mode already
after a short time of a few µs.
C. Experimental Results with Motor MB-75
Similar results are obtained for the larger machine as for
the smaller machine: Again, the bearing may form a capacitive
film even at low rotational speed. As in the case of the smaller
machine, the capacitive behavior does not exist constantly and
also changes to ohmic behavior. In contrast to the case of
the smaller machine, states with less pronounced behavior,
i.e. capacitive or resistive, in which phase angles in the order
of -45° are observed, too. Figs. 11 and 12 show again the
measured DE bearing currents and voltages as well as the
computed bearing impedances for 300 kHz HF supply voltage
and 210 as well as 300 rpm rotational speed, now for the larger
machine.
Fig. 11. Motor MB-75 and inverter IB-75, external HF voltage supply of DE
bearing: measured currents and voltages and computed bearing impedance for
300 kHz HF supply voltage, 210 rpm rotational speed, and ≈ 30°C bearing
temperature; computed bearing capacitance during capacitive behavior Cb =
1.7 nF.
to this capacitive mode, the resistive mode expected from
the conventional understanding occurs. The transitions are
not always instantaneous (when compared to the time scale,
i.e. taking place within a few microseconds.) A change from
resistive to capacitive mode may for example be preceded by
a slight increase in the bearing impedance before a rather
steep change to capacitive behavior occurs. The transitions
are significantly less distinct for the larger machine. Bearing
temperature as well as voltage applied across the bearing
are expected to influence the bearing impedance behavior,
too. Their analysis is subject of further research and not
within the scope of this paper. Further results on the bearing
impedance properties–notably the observed “mode change
behavior”–have been presented in [35]. While such further
research is required to fully understand the observed behavior
of the bearing impedance, the results shown in this paper
illustrate that some capacitive mode may exist the moment HF
circulating bearing currents begin to flow. This will eventually
allow such currents too, to be detected through the RF based
method. This is in contrast to the common understanding that
only in the case of discharge bearing currents discharges occur
within the bearing.
IX. C ONCLUSIONS
D. Analysis
For certain short time intervals, a bearing is observed to
form a capacitive film even at low rotational speed. In addition
Interpreting our observations in the context of HF circulating bearing currents, we postulate the following: For
“sufficiently” large HF circulating bearing currents and energy
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9. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
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understanding–the occurrence of some discharge.
Ub [V]
5
0
A PPENDIX
-5
50
100
150
200
Time [µs]
250
300
350
400
50
100
150
200
Time [µs]
250
300
350
400
Ib [A]
0.2
0
-0.2
0
|Zb| [ohm]
2
Angle of Zb [deg]
0
50
100
150
200
Time (µs)
250
300
Ctot = Crf + Cb,NDE + Cb,DE .
With the voltage across the bearing before the breakdown vb ,
the energy stored in these capacitances and the maximum
energy released during the discharge, Ec , is given by ([20],
eq. (3))
1
2
Ec = Ctot vb .
2
(a) Measured bearing current and bearing voltage.
10
Before a discharge occurs, energy is stored within the
two bearing capacitances, Cb,DE and Cb,NDE , and the rotorto-frame capacitance, Crf that are all connected in parallel.
These capacitances can be summarized in an equivalent total
capacitance, Ctot ([20], eq. (2)),
350
400
50
ACKNOWLEDGEMENT
Funding for the Open Access Publication was provided by
the Government of Styria.
0
-50
-100
0
R EFERENCES
50
100
150
200
Time (µs)
250
300
350
400
(b) Computed bearing impedance.
Fig. 12. Motor MB-75 and inverter IB-75, external HF voltage supply of DE
bearing: measured currents and voltages and computed bearing impedance for
300 kHz HF supply voltage, 300 rpm rotational speed, and ≈ 30°C bearing
temperature; computed bearing capacitance during capacitive behavior Cb =
8.5 nF.
stored in the circuit before these currents start to flow, the occurrence of these bearing currents, too, can to some extent be
detected using the proposed non-intrusive RF based method.
The energy release during a very short time–translating into
the radiating power–occurs as the current–driven by the HF
voltage in the loop of the HF circulating bearing current–
paths through the formerly electrically insulating lubricating
film of the bearing. This form of “penetration” brings along
some energy conversion as well as dissipation that radiates
via the machine acting as a transmitting antenna and can be
detected through the receiving antenna. When compared with
discharge bearing currents, the detected RF signals have lower
amplitudes – a few millivolts instead of some tens of volts.
This may be attributed by the smaller amount of energy stored
in the capacitances (two bearing capacitances and one rotorto-frame capacitance) before the breakdown occurs. Note also
that these energies are below the threshold level for bearing
current detection set in the commercially available device
determined in our laboratory (10 mV) ([34]).
It is also observed that–for certain short time intervals–a
bearing may form a capacitive film even at low rotational
speed; and that transitions between this capacitive mode and
the resistive mode expected from the conventional understanding occur. These modes and transitions might further
explain the possibility to detect HF circulating bearing currents through the RF based method that requires some form
of energy to be radiated as a result of–as per the current
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Annette Muetze (S’03-M’04-SM’09) is a full
professor at Graz University of Technology in
Graz, Austria, where she heads the Electric
Drives and Machines Institute. She received
the Dipl.-Ing. degree in electrical engineering from Darmstadt University of Technology,
Darmstadt, Germany and the degree in general
engineering from the Ecole Centrale de Lyon,
Ecully, France, both in 1999, and the Dr.
Tech. degree in electrical engineering from Darmstadt University of
Technology in 2004. Prior to joining Graz, she worked as an Assistant
Professor at the Electrical and Computer Engineering Department,
University of Wisconsin-Madison, Madison, US, and as an Associate
Professor at the School of Engineering of the University of Warwick
in the UK.
Ville Niskanen was born in Sotkamo, Finland
in 1984. He received the M.Sc. degree in electrical engineering from Lappeenranta University of Technology (LUT), Finland, in 2010.
He currently works as a junior researcher for
proactive maintenance of electrical equipment
at the Department of Electrical Engineering at
Lappeenranta University of Technology.
His main research interests are the diagnostics of electrical motor
driven systems.
Jero Ahola was born in Lappeenranta,
Finland in 1974. He received the M.Sc.
and D.Sc. degrees in electrical engineering
from Lappeenranta University of Technology,
in Finland, in 1999 and 200. He currently
works as a professor for energy efficiency
and preventive maintenance of electrical
equipment at the Department of Electrical
Engineering in Lappeenranta University of Technology. His main
research interests are diagnostics of electrical drive systems and
power line communications.
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