This document summarizes a literature study on the condition of tertiary bushings in interbus transformers and alternative protection schemes. It discusses how directly earthing the delta-connected tertiary winding raises the voltage stress on bushings, potentially reducing their lifetime. Online monitoring data is presented showing abnormalities in bushing parameters like tan δ. Literature suggests continuously operating bushings at 1.571 times rated voltage could reduce lifetime to around 2.5 years. The document evaluates direct earthing and floating schemes for protecting the tertiary winding.
�The sample calculations shown here illustrate steps involved in calculating the relay settings for generator protection.
�Other methodologies and techniques may be applied to calculate relay settings based on specific applications.
The protections of generator are the most complex and elaborate due to the following reasons: Generator is a large machine, connected to bus-bars. It is accompanied by unit transformers, auxiliary transformers and a bus system. ... The protection of generator should be co-ordinate with associated equipment's.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
Current Transformer and Potential TransformerRidwanul Hoque
One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.
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
Tan delta is the insulation power factor & is equal to the ratio of power dissipated in the insulation in watts to the product of effective voltage & current in volt ampere when tested under sinusoidal voltage.
Long & Short Interruptions: Interruptions – Definition – Difference between failures,
outage, Interruptions – causes of Long Interruptions – Origin of Interruptions – Limits for the
Interruption frequency – Limits for the interruption duration – costs of Interruption –
Overview of Reliability evaluation to power quality, comparison of observations and
reliability evaluation.Short interruptions: definition, origin of short interruptions, basic principle, fuse saving,
voltage magnitude events due to re-closing, voltage during the interruption, monitoring of
short interruptions, difference between medium and low voltage systems. Multiple events,
single phase tripping – voltage and current during fault period, voltage and current at post
fault period
Frequency response analysis (FRA) method has been proven to detect the transformer winding damage. However, there is no practical study which investigates the damages on transformer tap changer even though it has a high failure rate. Hence, this paper investigates normal and faulty transformer tap changer using FRA. The FRA measurements conducted using four different test configurations. Also, normal tap changer, pitting and coking tap changer contact were investigated. In addition to FRA measurement, winding resistance measurement has been conducted. The transformer turn ratio measurement also conducted to identify the taps positions. This study results significant to understand the effect of pitting and coking tap changer on the transformer frequency response. The results showed that pitting has a slight influence on the frequency response. However, coking shows a huge variation in low-frequency response. This effect observed during the winding resistance measurement.
�The sample calculations shown here illustrate steps involved in calculating the relay settings for generator protection.
�Other methodologies and techniques may be applied to calculate relay settings based on specific applications.
The protections of generator are the most complex and elaborate due to the following reasons: Generator is a large machine, connected to bus-bars. It is accompanied by unit transformers, auxiliary transformers and a bus system. ... The protection of generator should be co-ordinate with associated equipment's.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
Current Transformer and Potential TransformerRidwanul Hoque
One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.
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
Tan delta is the insulation power factor & is equal to the ratio of power dissipated in the insulation in watts to the product of effective voltage & current in volt ampere when tested under sinusoidal voltage.
Long & Short Interruptions: Interruptions – Definition – Difference between failures,
outage, Interruptions – causes of Long Interruptions – Origin of Interruptions – Limits for the
Interruption frequency – Limits for the interruption duration – costs of Interruption –
Overview of Reliability evaluation to power quality, comparison of observations and
reliability evaluation.Short interruptions: definition, origin of short interruptions, basic principle, fuse saving,
voltage magnitude events due to re-closing, voltage during the interruption, monitoring of
short interruptions, difference between medium and low voltage systems. Multiple events,
single phase tripping – voltage and current during fault period, voltage and current at post
fault period
Frequency response analysis (FRA) method has been proven to detect the transformer winding damage. However, there is no practical study which investigates the damages on transformer tap changer even though it has a high failure rate. Hence, this paper investigates normal and faulty transformer tap changer using FRA. The FRA measurements conducted using four different test configurations. Also, normal tap changer, pitting and coking tap changer contact were investigated. In addition to FRA measurement, winding resistance measurement has been conducted. The transformer turn ratio measurement also conducted to identify the taps positions. This study results significant to understand the effect of pitting and coking tap changer on the transformer frequency response. The results showed that pitting has a slight influence on the frequency response. However, coking shows a huge variation in low-frequency response. This effect observed during the winding resistance measurement.
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.
Analysis and mitigation of unbalance due to load in distribution system by us...eSAT Journals
Abstract Distribution network losses can vary significantly depending on the load unbalance. Here, an analysis of distribution system losses is presented that considers load unbalance and the effect of explicitly represented neutral wire. A general power flow algorithm for three-phase four-wire radial distribution networks, based on the current summation backward-forward technique is applied. Loss analysis results obtained from three-phase four-wire medium and low voltage test feeders with unbalanced load scenarios are presented and discussed an active power filter is designed, simulated, implemented, and tested. It can work in different modes: active power filtering, power factor correction, and load unbalance compensation. It is based on a current controlled voltage-source inverter with fixed carrier PWM. The control algorithm generates the source reference currents based on the controlled DC link voltage. The dimensioning criteria of the inductive and capacitive power components are discussed. The implementation is validated with simulated and experimental results obtained in a 5 kVA prototype. Keywords: distribution networks, losses, load unbalance, power flow
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.
Wind parks are made up of a large number of
saturable inductances (power transformers, inductive voltage
transformers (IVTs)), as well as capacitors (cables, wind turbine
harmonic filters, capacitor voltage transformers (CVTs), voltage
grading capacitors in circuit-breakers). Therefore, they may
present scenarios in which ferroresonance occurs. This paper
presents the scenarios that can lead to ferroresonant circuits in
doubly fed induction generator (DFIG) based wind parks.
An inclination towards renewable energy resources has been increased due to the requirement of clean environment and to satisfy the increasing power demand for the long run. A grid connected system requires the availability of a transformer in its power conversion stages that provides galvanic isolation between the grid and the power system. But inclusion of transformer results in making the system bulky and more expensive. In this paper different transformer-less PV inverter topologies are analyzed by comparing their efficiency, leakage current and THD of load current using MATLAB/Simulink environment. In order to achieve maximum power, maximum power point tracking (P&O algorithm) is used. From the simulation results, modified HB-ZVR is found to have minimum leakage current and constant common mode voltage with higher efficiency. Also, the hardware results are obtained for modified HB-ZVR topology.
A new closed loop AC to DC ĈUK converter is presented in this paper. The conventional ĈUK AC to DC converter has no feedback circuit. Thereby, the output voltage of the converter changes while changing the load. The proposed closed loop converter can regulate voltage with the variation of load over a wide range. Moreover, the power factor and Total Harmonic Distortion (THD) of the supply side current found quite satisfactory from this closed loop ĈUK converter. The converter operates in four steps with a different combination of voltage polarities and switching states. The feedback path consists of a voltage control loop and a current control loop. The closed loop ĈUK converter in this study is compared with the open loop version. Additionally, the comparison is made with the conventional converter of the same topology. The effectiveness in terms of power factor and THD of the proposed converter is verified using simulation results.
Transformerless Topology for Grid-Conected Inverters With Unipolar PWM ControlIJERA Editor
Most of the PV systems are designed with transformer for safety purpose with galvanic isolation. However, the transformer is big, heavy and expensive. Also, it reduces the overall frequency of the conversion stage. Generally PV inverter with transformer is having good efficiency. To overcome these problems, transformer less PV system is introduced. It is smaller, lighter, cheaper and higher in efficiency. However, dangerous leakage current will flow between PV array and the grid due to the stray capacitance. There are different types of configurations available for transformer less inverters like H5, H6, HERIC, and Dual paralleled buck inverter. But each configuration is suffering from its own disadvantages like high conduction losses, shoot-through issues of switches, dead-time requirements at zero crossing instants of grid voltage to avoid grid shoot-through faults and MOSFET reverse recovery issues. The main objective of the proposed transformer less inverter is to address two key issues: One key issue for a transformer less inverter is that it is necessary to achieve high efficiency compared to other existing inverter topologies. Another key issue is that the inverter configuration should not have any shoot-through issues for higher reliability.
A Three Level Single Stage PFC Converter for Variable Power Applicationspaperpublications3
Abstract: AC/DC power converters are required to operate with high power factor (PF) and low total harmonic distortion (THD) for improved grid quality and full capacity utilization of the transmission lines. Passive PF correction (PFC) circuits consist of inductive and capacitive filters followed by a diode bridge. They provide the simplest way of achieving high PF with high efficiency; however, they require low line frequency filters which are bulky and heavy. This work presents a new single stage three level isolated AC/DC PFC converter for high DC link voltage low-power applications achieved through an effective integration of AC/DC and DC/DC stages where all of the switches are shared between two operations. With the converter and switching scheme, input current shaping and output voltage regulation can be achieved simultaneously without introducing additional switches or switching actions. Due to the flexible DC link voltage structure, high power factor can be achieved at high line voltage. The performance of the single stage PFC converter is simulated in MATLAB/SIMULINK environment.
Keywords: Power Factor (PF), DC Link Voltage, Power Factor Correction Circuits (PFC).
Title: A Three Level Single Stage PFC Converter for Variable Power Applications
Author: Litty Joseph, Prof. Neetha John, Prof. Emmanuel Babu P
ISSN 2349-7815
International Journal of Recent Research in Electrical and Electronics Engineering (IJRREEE)
Paper Publications
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
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.
Control of grid connected inverter system for sinusoidal current injection wi...ijiert bestjournal
The control strategy for the grid connected inverter (GCI) during abnormal conditions like voltage sag,swell and line to ground fault has been presented. The strategy adopted here operates even during faulty conditions,unlike the conventional controller which fails to operate during fault y conditions. The Multi-Reference Frame (MRF) PI Controller is used for this purpose. In order to study the D ynamic Performance of the system,it is simulated in Matlab Simulink environment. The overall system is simulated for normal condition that is without the presence of fault,and with the presence of fault. The performance is also studied during abnormal conditions of the grid and its results are analyzed. The simulat ion results exhibit improved performance of the system during normal as well as abnormal conditions.
This work presents investigation of passive filter performance on three-phase inverter with 180° conduction mode. The simulation model of the inverter is developed by using MATLAB/Simulink. The power circuit used Insulated Gate Bipolar Transistor (IGBT) as switching device. The inverter is controlled by using bipolar Sinusoidal Pulse Width Modulation (SPWM) technique. The IGBT was set to 25 kHz for switching frequency (fs). Three types of passive filters which are LC, RC and PI filters are used to investigate the ability to remove the unwanted signal that occurred on the inverter. The result is analyzed based on the performances of output filter in term of Total Harmonic Distortion in voltage (THDv), current (THDi), shape of output voltage and current. The THD must be less than 5% at rated inverter output voltage or current by referring to IEC 61727 Standard. The passive filter is modeled in MATLAB/Simulink environment to study the characteristics and performance of the filters.
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Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
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