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.
SYSTEM NEUTRAL EARTHING
-DEFINITION OF SYSTEM EARTHING
-Comparative Performance For Various Conditions Using Different Earthing Methods
-EQUIPMENT SIZING
- APPENDIX FOR TYPICAL EARTHING TRANSFORMER SIZING
- APPENDIX GIVING GUIDELINE FOR SIZING OF COMMON BUS CONNECTED MEDIUM RESISTANCE EARTHING
The document presents information on harmonic reduction in inverter output voltage. It defines harmonics as integral multiples of a fundamental frequency that result in a distorted waveform when added together. Common sources of harmonics are identified as lighting ballasts, UPS systems, AC drives, and DC drives. Methods for attenuating harmonics discussed include inductive reactance, passive filters, active filters, 12-pulse and 18-pulse rectifiers, PWM, transformer connections, stepped wave inverters, and multilevel inverters. The document recommends limits on voltage and current distortion set by IEEE 519 and compares harmonic reduction performance of different converter and inverter configurations.
Switchgear and protection lecture 2 type of circuit breakers and applicationsanuphowlader1
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow.
Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
https://www.youtube.com/channel/UC2SvKI7eepP241VLoui1D5A
This document provides information about substations, including:
1. Substations are facilities used to change characteristics of electric power supply like voltage, frequency, or converting AC to DC. They are located between generation/transmission and distribution.
2. Substations are classified by their function (transformer, switching, power factor correction etc.) and construction (indoor, outdoor, underground etc.).
3. Key equipment in substations includes transformers, busbars, circuit breakers, insulators, and protection devices. Instrument transformers like PTs and CTs are also used.
4. Distribution systems distribute power from substations to consumers using feeders, distributors, and service mains. Distribution systems are classified by supply type
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
SYSTEM NEUTRAL EARTHING
-DEFINITION OF SYSTEM EARTHING
-Comparative Performance For Various Conditions Using Different Earthing Methods
-EQUIPMENT SIZING
- APPENDIX FOR TYPICAL EARTHING TRANSFORMER SIZING
- APPENDIX GIVING GUIDELINE FOR SIZING OF COMMON BUS CONNECTED MEDIUM RESISTANCE EARTHING
The document presents information on harmonic reduction in inverter output voltage. It defines harmonics as integral multiples of a fundamental frequency that result in a distorted waveform when added together. Common sources of harmonics are identified as lighting ballasts, UPS systems, AC drives, and DC drives. Methods for attenuating harmonics discussed include inductive reactance, passive filters, active filters, 12-pulse and 18-pulse rectifiers, PWM, transformer connections, stepped wave inverters, and multilevel inverters. The document recommends limits on voltage and current distortion set by IEEE 519 and compares harmonic reduction performance of different converter and inverter configurations.
Switchgear and protection lecture 2 type of circuit breakers and applicationsanuphowlader1
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow.
Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
https://www.youtube.com/channel/UC2SvKI7eepP241VLoui1D5A
This document provides information about substations, including:
1. Substations are facilities used to change characteristics of electric power supply like voltage, frequency, or converting AC to DC. They are located between generation/transmission and distribution.
2. Substations are classified by their function (transformer, switching, power factor correction etc.) and construction (indoor, outdoor, underground etc.).
3. Key equipment in substations includes transformers, busbars, circuit breakers, insulators, and protection devices. Instrument transformers like PTs and CTs are also used.
4. Distribution systems distribute power from substations to consumers using feeders, distributors, and service mains. Distribution systems are classified by supply type
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
Protection of transmission lines (distance)Rohini Haridas
This gives idea about necessity of protection of transmission line and protection based on time grading as well as on current grading. Also includes three step distance protection of transmission line
Disadvantages of corona, radio interference, inductive interference between p...vishalgohel12195
Disadvantages of corona, radio interference, inductive interference between power and communication lines
Introduction
Disadvantages of corona.
Radio interference.
Inductive interference between power and communication lines
This document provides information on a Power System Protection course taught at Vivekanandha College of Engineering for Women. The syllabus covers 5 units: introduction to protection schemes, relay operating principles and characteristics, apparatus protection, theory of circuit interruption, and circuit breakers. It lists textbooks and presents details on each unit, including topics like relay types, transformer/generator/motor protection, arc phenomena, and different circuit breaker types. The last section provides references for textbooks, websites, and presentations on related topics.
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Reactive power is necessary to maintain adequate voltage levels to transmit active power across transmission systems. It is required for system reliability and to prevent voltage collapse. Voltage is controlled by managing the production and absorption of reactive power on the system. Both insufficient reactive power and excessive reactive power can cause voltage issues and equipment problems if voltage is not properly regulated. Reactive power reserves are also required to maintain voltage stability under contingency events like generator or transmission line outages.
This document discusses the selection of circuit breakers. It begins by defining a circuit breaker as a protective device that is used to automatically open the faulty part of a power system during a fault. There are two main factors considered when selecting a circuit breaker: 1) its normal working power level and fault level ratings, which are specified by the rated interrupting current or MVA, and 2) its momentary current and speed ratings. The momentary current rating must be higher than the maximum current during fault conditions, while the speed rating depends on transient fault currents and specified cycles. Multiplying factors are used to determine the circuit breaker's short circuit interrupting current from fault analysis calculations.
This document discusses fault level calculations in electric power systems. It explains that fault level calculations are necessary to select protective devices, circuit breakers, and equipment that can withstand short circuit currents. The document outlines the procedure for calculating fault levels, which involves representing the system with a single line diagram, choosing a base MVA, calculating per unit reactances, determining the equivalent reactance to the fault point, and using formulas to calculate fault MVA and current. It also discusses how current limiting reactors can be used to insert additional reactance and reduce short circuit currents to match circuit breaker ratings.
This document discusses short circuit calculations for electrical systems. It explains that short circuits can be caused by insulation failures, flashovers, physical damage or human error. Symmetrical and asymmetrical faults are described. Short circuit calculations should be performed at protective devices to determine device ratings and settings, cable sizes, and motor starting capabilities. A 6-step process for short circuit calculations is outlined, involving drawing diagrams, applying a power base, calculating impedances, and determining fault currents. Equations for converting three-phase values to single-phase are provided. An example cable calculation and fault current determination is shown.
The document discusses the internal connections of three-phase induction motors. It explains that three-phase motors have coils connected to form three separate winding phases with an equal number of coils in each phase. The phases can be connected in either a wye or delta configuration. It also describes how dual-voltage motors can be connected externally for either a higher or lower voltage by connecting the coil groups in series or parallel, respectively. Ball bearings are discussed as having advantages for electric motors like withstanding high speeds and allowing for smaller air gaps.
The document discusses capacitive voltage transformers (CVTs). It describes CVTs as devices that step down extra high voltage signals for metering and protection purposes. CVTs consist of capacitors that divide the transmission line voltage, with an inductive element to tune the device to line frequency and a voltage transformer to further step down the voltage. CVTs are more economical than wound transformers for voltages over 100kV. CVTs can also be used for power line carrier communications and provide insulation between high and low voltage circuits.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
the ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.
High Voltage Direct Current technology has certain characteristics which
make it especially attractive for transmission system applications. HVDC
transmission system is useful for long-distance transmission, bulk power delivery and
long submarine cable crossings and asynchronous interconnections. The study of
faults is essential for reasonable protection design because the faults will induce a
significant influence on operation of HVDC transmission system. This paper provides
the most dominant and frequent faults on the HVDC systems such as DC Line-to-
Ground fault and Line-to-Line fault on DC link and some common types of AC faults
occurs in overhead transmission system such as Line-to-Ground fault, Line-to-Line
fault and L-L-L fault. In HVDC system, faults on rectifier side or inverter side have
major affects on system stability. The various types of faults are considered in the
HVDC system which causes due to malfunctions of valves and controllers, misfire
and short circuit across the inverter station, flashover and three phase short circuit.
The various faults occurs at the converter station of a HVDC system and
Controlling action for those faults. Most of the studies have been conducted on line
faults. But faults on rectifier or inverter side of a HVDC system have great impact on
system stability. Faults considered are fire-through, misfire, and short circuit across
the inverter station, flashover, and a three-phase short circuit in the ac system. These
investigations are studied using matlab simulink models and the result represented in
the form of typical time responses.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
1) The internal generated voltage (EA) in a synchronous generator is different from the output voltage (Vφ) due to armature reaction, self-inductance, and resistance of the stator coils.
2) Armature reaction, caused by the distortion of the air-gap magnetic field by the stator current, is the largest effect. It can be modeled by an inductor in series with EA.
3) The full equivalent circuit model of a 3-phase synchronous generator includes a DC power source for the rotor field, and a per-phase equivalent circuit with EA in series with resistance and inductance to represent the combined effects of armature reaction and self-inductance.
This document is a final year project presentation on Static VAR Compensator (SVC). It discusses Flexible AC Transmission Systems (FACTS) which use power electronics to control power flow and increase transmission capacity. SVCs in particular provide fast reactive power support to control voltage and improve stability. Different types of SVC are described including series and shunt compensators using thyristor controlled capacitors and reactors. Mechanically Switched Capacitors are also discussed as a type of shunt compensator. The project layout and applications of SVC systems for transmission systems are outlined.
The document discusses power quality and various power quality disturbances including voltage sag, swell, micro and long interruptions, voltage spikes, unbalance, harmonics distortion, and voltage fluctuations. It defines each disturbance, provides examples of common causes and potential consequences on equipment. Maintaining good power quality is important for the proper functioning of modern electronic devices that have become more sensitive to voltage and current deviations from ideal sine waves. Poor power quality can result in equipment damage and malfunctions as well as economic losses.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
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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.
Protection of transmission lines (distance)Rohini Haridas
This gives idea about necessity of protection of transmission line and protection based on time grading as well as on current grading. Also includes three step distance protection of transmission line
Disadvantages of corona, radio interference, inductive interference between p...vishalgohel12195
Disadvantages of corona, radio interference, inductive interference between power and communication lines
Introduction
Disadvantages of corona.
Radio interference.
Inductive interference between power and communication lines
This document provides information on a Power System Protection course taught at Vivekanandha College of Engineering for Women. The syllabus covers 5 units: introduction to protection schemes, relay operating principles and characteristics, apparatus protection, theory of circuit interruption, and circuit breakers. It lists textbooks and presents details on each unit, including topics like relay types, transformer/generator/motor protection, arc phenomena, and different circuit breaker types. The last section provides references for textbooks, websites, and presentations on related topics.
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Reactive power is necessary to maintain adequate voltage levels to transmit active power across transmission systems. It is required for system reliability and to prevent voltage collapse. Voltage is controlled by managing the production and absorption of reactive power on the system. Both insufficient reactive power and excessive reactive power can cause voltage issues and equipment problems if voltage is not properly regulated. Reactive power reserves are also required to maintain voltage stability under contingency events like generator or transmission line outages.
This document discusses the selection of circuit breakers. It begins by defining a circuit breaker as a protective device that is used to automatically open the faulty part of a power system during a fault. There are two main factors considered when selecting a circuit breaker: 1) its normal working power level and fault level ratings, which are specified by the rated interrupting current or MVA, and 2) its momentary current and speed ratings. The momentary current rating must be higher than the maximum current during fault conditions, while the speed rating depends on transient fault currents and specified cycles. Multiplying factors are used to determine the circuit breaker's short circuit interrupting current from fault analysis calculations.
This document discusses fault level calculations in electric power systems. It explains that fault level calculations are necessary to select protective devices, circuit breakers, and equipment that can withstand short circuit currents. The document outlines the procedure for calculating fault levels, which involves representing the system with a single line diagram, choosing a base MVA, calculating per unit reactances, determining the equivalent reactance to the fault point, and using formulas to calculate fault MVA and current. It also discusses how current limiting reactors can be used to insert additional reactance and reduce short circuit currents to match circuit breaker ratings.
This document discusses short circuit calculations for electrical systems. It explains that short circuits can be caused by insulation failures, flashovers, physical damage or human error. Symmetrical and asymmetrical faults are described. Short circuit calculations should be performed at protective devices to determine device ratings and settings, cable sizes, and motor starting capabilities. A 6-step process for short circuit calculations is outlined, involving drawing diagrams, applying a power base, calculating impedances, and determining fault currents. Equations for converting three-phase values to single-phase are provided. An example cable calculation and fault current determination is shown.
The document discusses the internal connections of three-phase induction motors. It explains that three-phase motors have coils connected to form three separate winding phases with an equal number of coils in each phase. The phases can be connected in either a wye or delta configuration. It also describes how dual-voltage motors can be connected externally for either a higher or lower voltage by connecting the coil groups in series or parallel, respectively. Ball bearings are discussed as having advantages for electric motors like withstanding high speeds and allowing for smaller air gaps.
The document discusses capacitive voltage transformers (CVTs). It describes CVTs as devices that step down extra high voltage signals for metering and protection purposes. CVTs consist of capacitors that divide the transmission line voltage, with an inductive element to tune the device to line frequency and a voltage transformer to further step down the voltage. CVTs are more economical than wound transformers for voltages over 100kV. CVTs can also be used for power line carrier communications and provide insulation between high and low voltage circuits.
Static relays use electronic components like semiconductors instead of mechanical parts to detect faults and operate. They have components like rectifiers to convert AC to DC, level detectors to compare values to thresholds, and amplifiers and output devices to trigger trips. The document discusses the components, types, and applications of various static relays like overcurrent, directional, differential, distance and instantaneous relays used in power system protection.
the ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.
High Voltage Direct Current technology has certain characteristics which
make it especially attractive for transmission system applications. HVDC
transmission system is useful for long-distance transmission, bulk power delivery and
long submarine cable crossings and asynchronous interconnections. The study of
faults is essential for reasonable protection design because the faults will induce a
significant influence on operation of HVDC transmission system. This paper provides
the most dominant and frequent faults on the HVDC systems such as DC Line-to-
Ground fault and Line-to-Line fault on DC link and some common types of AC faults
occurs in overhead transmission system such as Line-to-Ground fault, Line-to-Line
fault and L-L-L fault. In HVDC system, faults on rectifier side or inverter side have
major affects on system stability. The various types of faults are considered in the
HVDC system which causes due to malfunctions of valves and controllers, misfire
and short circuit across the inverter station, flashover and three phase short circuit.
The various faults occurs at the converter station of a HVDC system and
Controlling action for those faults. Most of the studies have been conducted on line
faults. But faults on rectifier or inverter side of a HVDC system have great impact on
system stability. Faults considered are fire-through, misfire, and short circuit across
the inverter station, flashover, and a three-phase short circuit in the ac system. These
investigations are studied using matlab simulink models and the result represented in
the form of typical time responses.
Unit 04 Protection of generators and transformers PremanandDesai
The document discusses faults and protection methods for alternators and transformers. For alternators, common faults include failure of the prime mover, field failure, overcurrent, overspeed, overvoltage, and unbalanced or stator winding faults. Differential and inter-turn protection are described. For transformers, faults include open circuits, overheating, and winding short-circuits. Buchholz devices, earth fault relays, overcurrent relays, and differential systems provide protection. Earth fault protection for transformers uses a core-balance leakage scheme.
1) The internal generated voltage (EA) in a synchronous generator is different from the output voltage (Vφ) due to armature reaction, self-inductance, and resistance of the stator coils.
2) Armature reaction, caused by the distortion of the air-gap magnetic field by the stator current, is the largest effect. It can be modeled by an inductor in series with EA.
3) The full equivalent circuit model of a 3-phase synchronous generator includes a DC power source for the rotor field, and a per-phase equivalent circuit with EA in series with resistance and inductance to represent the combined effects of armature reaction and self-inductance.
This document is a final year project presentation on Static VAR Compensator (SVC). It discusses Flexible AC Transmission Systems (FACTS) which use power electronics to control power flow and increase transmission capacity. SVCs in particular provide fast reactive power support to control voltage and improve stability. Different types of SVC are described including series and shunt compensators using thyristor controlled capacitors and reactors. Mechanically Switched Capacitors are also discussed as a type of shunt compensator. The project layout and applications of SVC systems for transmission systems are outlined.
The document discusses power quality and various power quality disturbances including voltage sag, swell, micro and long interruptions, voltage spikes, unbalance, harmonics distortion, and voltage fluctuations. It defines each disturbance, provides examples of common causes and potential consequences on equipment. Maintaining good power quality is important for the proper functioning of modern electronic devices that have become more sensitive to voltage and current deviations from ideal sine waves. Poor power quality can result in equipment damage and malfunctions as well as economic losses.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
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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.
2.Ourside.vip.Power quality improvement using dynamic voltage restorer.pdfssuser3793c8
This document discusses a study on using a Dynamic Voltage Restorer (DVR) to improve power quality by mitigating voltage distortions. The DVR injects voltages into the distribution line to maintain the voltage profile and ensure a constant load voltage. Simulations were conducted using MATLAB/Simulink to show the effectiveness of the DVR-based strategy in smoothing distorted voltages caused by 3rd and 5th harmonic distortions. The results show that the DVR reduced the total harmonic distortion from around 18% to less than 4% when 3rd harmonics were inserted, and from around 23% to less than 4% when 5th harmonics were inserted.
An Overview of Harmonic Sources in Power SystemIOSR Journals
This document discusses the various sources of harmonics in power systems. It defines harmonics as multiples of the fundamental power system frequency that distort voltages and currents. The main sources described include transformers, rotating machines, power converters such as large and medium power converters and variable frequency drives, fluorescent lamps, and arcing devices like electric arc furnaces. Power converters are identified as the most widespread source due to their use of electronic switching to rectify and vary AC power frequencies and voltages. The impacts of increasing non-linear loads on power quality are also noted.
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
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.
Introduction
Power systems globally are experiencing a transition towards decarbonisation of electricity production through large-scale deployment of renewable energy sources (RES), which are gradually displacing conventional thermal plant. This changing environment is seeing a proliferation of power electronic converters connecting at all voltage levels in power systems, namely RES, FACTS devices, HVDC systems, domestic load, etc. These devices are highly non-linear and emit harmonics at the point of connection, but also modify pre-existing harmonics in the network. In addition, increased installation of HVAC cables is creating system resonances at frequencies close to the characteristic emissions from these non-linear devices. As a result, many power systems are already experiencing an increase in harmonic distortion. Power quality issues associated with harmonics in power systems are becoming more pronounced and are driving a new focus towards the need to undertake detailed analysis at the planning stages in order to ensure adherence to statutory limits.
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Harmonic analysis procedure
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www.etasr.com Mekhamer et al.: Design Practices in Harmonic Analysis Studies Applied to Industrial Electrical …
Design Practices in Harmonic Analysis Studies
Applied to Industrial Electrical Power Systems
S. F. Mekhamer
Faculty of Engineering,
Ain Shams University
Cairo, Egypt
saidfouadmekhamer@yahoo.com
A. Y. Abdelaziz
Faculty of Engineering,
Ain Shams University
Cairo, Egypt
almoatazabdelaziz@hotmail.com
S. M. Ismael
Electrical Engineering Division,
ENPPI
Cairo, Egypt
shriefmohsen@enppi.com
Abstract—Power system harmonics may cause several problems,
such as malfunctions of electrical equipment, premature
equipment failures and plant shutdowns. Accordingly, mitigation
of these harmonics is considered an important target especially
for industrial applications where any short downtime period may
lead to great economic losses. Harmonic analysis studies are
necessary to analyze the current and voltage harmonic levels and
check if these levels comply with the contractual or international
standard limits. If the studies reveal that the preset limits are
exceeded, then a suitable harmonic mitigation technique should
be installed. Harmonic analysis studies in the industrial electrical
systems are discussed in many references. However, a
comprehensive procedure for the steps required to perform a
harmonic study is rarely found in the literature even though it is
strongly needed for design engineers. This paper provides a
comprehensive procedure for the steps required to perform a
harmonic study in the form of a flowchart, based on industrial
research and experience. Hence, this paper may be considered as
a helpful guide for design engineers and consultants of the
industrial sector.
Keywords-harmonic analysis study; distortion; point of
common coupling (PCC); variable frequency drive (VFD);
resonance
I. INTRODUCTION
Due to the dramatic increase in the usage of nonlinear loads
in industrial applications (mainly regarding Variable Frequency
Drives or VFDs), the power system harmonics problems has
gain in significance, representing a big obstacle against the
wide application of VFDs although they enhance system
efficiency and provide great energy saving. The power system
harmonics cause many harmful effects including:
Overheating of generators, motors, transformers, and
power cables that lead to early equipment failures
Failure of capacitor banks
Nuisance tripping to protection relays
Interference to communication systems and sensitive
electronic devices
Accordingly, the mitigation of the power system harmonics
is of great importance in industrial electrical systems in order to
increase system reliability, enhance operation economics, avoid
unwanted equipment failure and process downtimes [1].
Nowadays, industrial electrical systems contain a valuable
amount of nonlinear loads. Accordingly, power system studies
for industrial plants should contain harmonic analysis studies
beside short circuit, load flow and motor starting studies. The
harmonic analysis studies for the industrial systems are
discussed in [2], but the author did not focus on the guidelines
of the harmonic study. Also the authors did not introduce the
various international standards that set the limits of the
harmonic distortions.
The goals of this paper can be summarized as follow:
1. To highlight the purpose of a harmonic analysis study
2. To highlight some guidelines for harmonic analysis studies
3. To provide a comprehensive description of the procedure
required to perform a harmonic study
4. To introduce the international standards limits for the
harmonic distortions
II. PURPOSE OF A HARMONIC ANALYSIS STUDY
Nowadays, the applications of the nonlinear loads in the
industrial plants grow rapidly and the percentage of these loads
may be in the range of 30% to 50% of the total plant load.
Accordingly, the effects of harmonics within the electrical
system and their impact on the electric utility and neighboring
plants should be examined to avoid equipment damage and
plant shutdowns. The following cases may necessitate
performing a harmonic study [3]:
1. During the design stage of a project, if the amount of the
nonlinear loads exceeds 25% of the total loads on a bus or
a system, a harmonic analysis study is required to check
the compliance with the contractual/ international
harmonic limits
2. To solve harmonic-related problems such as failure of
electrical equipment or malfunction of protective relays
3. If an existing plant is going to be expanded and a
significant amount of nonlinear loads is going to be added,
then a harmonic analysis study is required to verify the
plant performance after the addition of these loads
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4. If a capacitor bank is installed in any electrical networks
that contain many nonlinear loads, then a harmonic
analysis is required to check the possibility of resonance
occurrence
III. GUIDELINES FOR HARMONIC ANALYSIS STUDIES
A. Harmonic Sources
All nonlinear loads are defined also as harmonic sources, as
clearly shown in Figure 1, because they draw non-sinusoidal
currents when a sinusoidal voltage is applied. The nonlinear
load acts as a source of harmonic currents in power system,
thus causing voltage distortions at the various system buses due
to the harmonic voltage drops across the system impedances.
Fig. 1. Effect of a nonlinear load on the current waveform
To perform a harmonic study, the design engineer must
identify the available harmonic sources and the harmonic
currents generated by these harmonic sources. There are three
options available for the design engineer to determine the
harmonic currents, as described below:
a. To measure the generated harmonics from each harmonic
source (time-consuming option, applicable only in case of
existing plants)
b. To calculate the generated harmonic currents by using
suitable mathematical analysis (may require extensive
manual and time-consuming calculations)
c. To use typical values based on computerized softwares
libraries or based on the available data from the nonlinear
load's manufacturer
Practically, options (a) and (c) are the most used options
and provide reasonable results.
The following are the main sources of harmonics in
industrial applications [4]:
1) Saturable Magnetic equipment:
There are various saturable magnetic equipment that cause
harmonic problems such as:
a. Rotating machines, rotating machines like induction
motors may act as sources of the third harmonic currents
when they are operating in abnormal or overloaded
conditions.
b. Ballasts of discharge lamps, the discharge lamps like
mercury vapor, high-pressure sodium and fluorescent
lamps are dominant sources of the third harmonic
currents.
c. Transformer harmonics, transformers create harmonics
when they are overexcited. In addition, the transformer
inrush currents may contain some even harmonics, but the
duration is rather limited.
d. Generator harmonics, voltage harmonics are created from
the synchronous generators due to the non-sinusoidal
distribution of the flux in the air gap. Selection of suitable
coil-span factor (called also pitch factor) can significantly
reduce the voltage harmonics from the generators.
2) Power Electronic Devices:
There are various power electronic devices that cause harmonic
problems such as:
a. Variable Frequency Drives (VFDs) used in fans and
pumps
b. Switched mode power supplies (SMPS), used in
instruments and personal computers
c. High voltage DC transmission stations (HVDC)
d. Static VAR compensators
e. Uninterruptable power supply systems (UPS)
f. Battery charger systems
g. Flexible AC transmission systems (FACTS)
h. AC and DC arc furnaces in steel manufacturing plants
B. Resonance
The inductive reactance increases as the frequency increases as
follow:
LFXL ...2
where:
XL: Inductive reactance
F : System frequency
L : Inductance
While the capacitive reactance decreases as the frequency
increases as follows:
)...2 CF(/1XC
where:
XC: Capacitive reactance
C : Capacitance
Due to the opposite characteristics of the inductive and
capacitive reactances, there must be a frequency at which XL
equals XC. This condition of equal and opposite reactances is
called “resonance”. Most of the power system elements are
inductive. Accordingly, the presence of shunt capacitors used
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for power factor correction or harmonic filtering can increase
the probability of resonance occurrence. There are two types of
resonance, the series resonance and the parallel resonance. The
harmful effect of the series resonance may be the flow of
excessive harmonic currents through the network elements.
These excessive currents cause nuisance tripping to the
protection relays, overheating of cables, motors, and
transformers and premature failure to the electrical equipment.
The harmful effect of the parallel resonance may be the
presence of excessive harmonic voltages across the network
elements. These excessive harmonic voltages cause dielectric
breakdown of the electrical equipment’s insulation [3].
1) Series Resonance:
The series resonance occurs when an inductor and a
capacitor are connected in series and they resonate together at a
certain resonance frequency. An example of the series resonant
circuit is shown in Fig. 2. This AC circuit is said to be in
resonance when the inductive reactance XL is equal to the
capacitive reactance XC.
Fig. 2. AC circuit representing an example for the series resonance
2) Parallel Resonance:
The parallel resonance occurs when an inductor and a
capacitor are connected in parallel and they resonate together at
a certain resonance frequency. There are many forms of
parallel resonant circuits. A typical parallel resonant circuit is
shown in Figure 3. This circuit is said to be in parallel
resonance when XL=XC similar to the series resonance.
Fig. 3. AC circuit representing an example for the parallel resonance
C. Tools of performing a harmonic analysis study:
The harmonic analysis study can be performed by any of the
following tools:
a. Manual calculations, which are limited to small-size
networks since they are very complicated and susceptible
to errors.
b. Field measurements, which are often used as a
verification of the design, or as a preliminary diagnosis of
a field problem.
c. Digital computer simulations, which nowadays are the
most convenient and economical method for analyzing
system harmonics
D. Power System Modeling:
At the presence of harmonics, the electrical system
elements models must be updated to encounter for the presence
of higher frequencies in the system rather than the power
frequency (50 Hz or 60 Hz). Details for electrical system
elements models under harmonics distortions can be found in
[3].
E. Types of Analyses Performed during the Harmonic
Analysis:
There are two main types of analyses that could be performed
during harmonic analysis [2]:
a. Current and voltage distortion analysis, in which the
individual and total current and voltage harmonic
distortions are calculated at the various buses then the
results are compared with the relevant contractual limits.
b. Impedance versus frequency analysis, in which a plot of
the system impedance at various buses is plotted against
the frequency. This analysis is important in predicting the
system resonances prior to energizing the electrical
system. A peak in the impedance plot indicates a parallel
resonance while a valley in the impedance plot indicates a
series resonance.
IV. STEPS OF PERFORMING A HARMONIC ANALYSIS STUDY
If a harmonic analysis study is required to be performed
due to any of the cases described in section (II), the following
steps should be followed:
a. Obtain the electrical system one-line diagram and
highlight the available nonlinear loads, capacitor banks
and medium voltage cables of long length within the
industrial system.
b. Highlight the point of common coupling (PCC) which is
the point that connects the industrial network with the
utility or with the neighboring plant.
c. Highlight the in-plant system buses that are expected to be
affected from harmonic distortions.
d. Gather the harmonics-related data of all nonlinear loads
within the plant.
e. Obtain, from the utility company, the relevant data of
current and voltage harmonics at the contractual PCC
including the minimum and maximum short circuit fault
levels and the permissible limits on voltage and current
harmonics because the allowable harmonic limits vary
from country to country.
f. Model the electrical network using any of the
commercially available softwares such as the electrical
transient analyzer program (ETAP).
g. Perform the harmonic analysis for the electrical network
at the various possible operating scenarios.
h. Check the individual and total voltage and current
distortion levels at the interested system buses and at the
PCC.
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i. Check the harmonic frequency spectrum, which is a plot
of each individual harmonic value with respect to the
fundamental value versus frequency.
j. If the harmonic distortion results exceed the allowable
limits, select an appropriate harmonic mitigation solution
and the optimum insertion point for that solution. Further
details about this point are introduced in section (V).
k. Re-perform the harmonic analysis study after adding the
harmonic mitigation technique to ensure compliance with
the contractual / international harmonic limits.
An extensive literature review over the past twenty years
leads to the fact that there is no single article that summarizes
the steps required to perform a harmonic analysis study even
though the importance of this procedure for the design
engineers. The comprehensive flowchart presented in Figure 4
provides this novel helpful approach.
V. SELECTION OF THE HARMONIC FILTER'S INSERTION POINT
Even if the design engineer selects the optimum harmonic
mitigation technique for his plant, among the available
harmonic mitigation solutions in the market [5], then the filter
insertion point should be studied carefully as it greatly affects
system performance [6]. As shown in Figure 5, the possible
filter insertion points can be classified into three categories as
follow:
A. Local Harmonic Mitigation
In this mode of mitigation, the shunt type (passive or
active) harmonic filter is directly connected to the nonlinear
load terminals. This mode is efficient if the number of
nonlinear loads is limited and the power of each nonlinear load
is significant compared to the total plant power. Circulation of
harmonic currents in the electrical network is avoided, thus the
harmonic impact on the upstream network elements is
minimized.
B. Semi-Global Harmonic Mitigation
In this mode of mitigation, the shunt type (passive or
active) harmonic filter is connected to the input of the LV sub-
distribution switchboard. Accordingly, the filter treats several
sets of nonlinear loads. This type of compensation is ideal in
presence of multiple nonlinear loads each having low rated
power. A practical example of this mode is found in
commercial buildings where a harmonic filter may be found on
each floor of the building.
C. Global Harmonic Mitigation
This mode of mitigation is more concerned with meeting
the contractual harmonic limits at the (PCC) than the reduction
of the in-plant harmonics. The major drawback of this
mitigation mode is that the harmonic currents are allowed to
circulate in the electrical network. Thus, the various electrical
elements within the plant will be subjected to harmful
harmonic impact.
VI. INTERNATIONAL HARMONIC STANDARDS
The purpose of imposing strict limits on the harmonics
emissions is to ensure that the current and voltage distortions at
the PCC are kept sufficiently low. Thus, the other customers
connected at the same point are not disturbed. The international
standards related to harmonic distortion limits can be classified
as follows:
A. Standards specifying limits for individual nonlinear
equipment
IEC 61000-3-2 [7], which specifies the current harmonic
limits for low voltage equipment that has an input current
less than 16 A.
IEC 61000-3-12 [8], which specifies the current harmonic
limits for an equipment that has an input current between
16A and 75A
IEC 61800-3 [9],which specifies the electro-magnetic
compatibility (EMC) requirements of the adjustable speed
drive systems
As noticed, the above standards are for small rating and low
voltage harmonic loads only. In addition, the above standards
do not set limits on the overall distribution network.
B. Standards specifying limits for electrical networks
IEEE 519-1992 [10], this document introduces many
useful recommended practices for harmonics control in
electrical networks. This document is widely used in the
industrial sector and many consultants/clients use the
limits indicated in it as contractual limits within their
specifications.
IEC 61000-3-6 [11], this specification performs an
assessment of the harmonic emission limits for distorting
loads in medium voltage and high voltage power systems.
Up till now, this specification is not widely used in the
industrial sector because it is rather new (punlished in
2008).
British engineering recommendation G5/4-1 [12], this
document provides some helpful engineering
recommendations for establishing the allowable harmonic
limits of the voltage distortions in the United Kingdom.
VII. IEEE 519-1992 HARMONIC LIMITS
A. Harmonic current distortion limits
Harmonic current distortion limits are introduced in the
IEEE 519-1992. A summary of these current harmonic limits is
shown in Table I. Setting limits for the current harmonic levels
protects the utility company and the other utility consumers
connected on the same feeder.
where:
ISC : maximum short circuit current at PCC
I1 or IL: maximum demand load current (fundamental
frequency component) at PCC
5. ETASR - Engineering, Technology & Applied Science Research Vol. 3, No. 4, 2013, 467-472 471
www.etasr.com Mekhamer et al.: Design Practices in Harmonic Analysis Studies Applied to Industrial Electrical …
Yes
No
No
New plant
Existing plant
Harmonic analysis is
not required
End
Existing or
new plant
1. Gather all the required
data about the existing
harmonic sources.
2. Make a survey about the
harmonic related
.problems within the plant
3. Define the PCC.
4. Perform site harmonic
measurements at the PCC
and at the system buses
that contain the major
nonlinear loads.
1. Define the harmonic sources within the
plant.
2. Define the ratio of the nonlinear loads with
respect to the total plant loads as follow:
Ratio = nonlinear loads (KVA) / total plant
loads (KVA
Ratio of nonlinear
loads with respect
to the total plant
loads ≥ 25%
Harmonic Analysis is required. Perform the following steps:
1. Obtain the electrical system one-line diagram and highlight the available nonlinear loads, capacitor
banks and long medium voltage cables within the industrial system.
2. Highlight the point of common coupling (PCC).
3. Highlight the in-plant system buses (or switchgears) that are foreseen to be affected from harmonic
distortions.
4. Gather the required equipment data, ratings and the harmonics related data of all the plant
nonlinear loads.
5. Obtain, from the utility company, the relevant data of current and voltage harmonics at the
contractual PCC including the minimum and maximum short circuit fault levels and the
permissible limits on voltage and current harmonics.
6. Model the electrical network using any of the commercially available softwares such as the
electrical transient analyzer program (ETAP).
7. Perform the harmonic analysis for the electrical network at the various possible operating
scenarios.
8. Check the individual and total voltage and current distortion levels at the interested system buses
and the PCC to ensure compliance with the contractual / international harmonic limits.
Voltage and current
harmonic levels
exceed the allowable
C
1. Evaluate the results of the harmonic
study then select the optimum
technical and economic harmonic
mitigation technique.
2. Select the optimum insertion point
for the selected harmonic
mitigation technique.
3. For a new plant, Implement the
selected harmonic mitigation
technique in the network model
then re-perform the harmonic
analysis study.
4. For an existing plant, model
electrical network of the plant after
adding the selected harmonic
mitigation technique then perform
the harmonic analysis study.
End
C
Start
Yes
Fig. 4. A comprehensive procedure for the steps required to perform a harmonic analysis
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Fig. 5. Various insertion points for the harmonic filters
It should be noted that all the power generation equipment
are limited to these values of current distortion, regardless of
the actual ISC/I1 ratio. The ratio ISC/IL is the ratio of the short
circuit current available at the (PCC) to the maximum
fundamental load current. It is recommended that the load
current (IL) be calculated over any (15) or (30) min period and
then averaged over the next (12) month period.
TABLE I. HARMONIC CURRENT DISTORTION LIMITS FOR GENERAL
DISTRIBUTION SYSTEMS (SYSTEM VOLTAGES: FROM 120V TO 69 KV)
Odd harmonic order h (%)
Individual current harmonic distortion (%)ISC / I1
h < 11 11 ≤ h < 17 17 ≤ h < 23 23 ≤ h <35 h ≥ 35
Total
harmonic
distortion
THDI %
< 20 * 4 2 1.5 0.6 0.3 5
20-50 7 3.5 2.5 1 0.5 8
50-
100
10 4.5 4 1.5 0.7 12
100-
1000
12 5.5 5 2 1 15
>1000 15 7 6 2.5 1.4 20
B. Harmonic voltage distortion limits:
The IEEE 519-1992 defines the allowable voltage harmonic
limits at the PCC. Table II summarizes the limits for the low
voltage systems and Table III summarizes the limits for the
medium and high voltage systems.
Where:
Special systems: critical applications like hospitals and
airports
Dedicated systems: systems that contain only nonlinear
loads
It is important to highlight that the limits listed in Table III
should be used as system design values for normal operation
conditions (lasting more than one hour). For shorter operation
periods, during start-ups or unusual transient conditions, these
harmonic limits may be allowed to exceed by 50%.
TABLE II. HARMONIC VOLTAGE DISTORTION LIMITS FOR LOW VOLTAGE
DISTRIBUTION SYSTEMS (SYSTEM VOLTAGES: BELOW 1 KV)
Allowable voltage
THD
Special
systems
General
distribution
systems
Dedicated
systems
Voltage THD (%) 3% 5% 10%
TABLE III. HARMONIC VOLTAGE DISTORTION LIMITS FOR MEDIUM AND
HIGH VOLTAGE DISTRIBUTION SYSTEMS
Bus voltage
Individual voltage
harmonic distortion
(%)
Total voltage
harmonic
distortion (%)
69 kV and below 3 % 5 %
From 69 kV to 161 kV 1.5 % 2.5 %
161 kV and above 1 % 1.5 %
VIII. CONCLUSIONS
Harmonic analysis studies are necessary to analyze the
current and voltage harmonic levels within any industrial
electrical system and to check if these levels comply with the
contractual or international standard limits. This paper provides
a comprehensive approach for performing a harmonic study,
presented in the form of a flowchart. In addition, this paper
presents the current and voltage harmonic limits used in
industrial systems.
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