This document provides details on the design process for a Static Var Compensator (SVC). It discusses key considerations like load characteristics, environmental conditions, thyristor selection and operation, reactor arrangements, harmonic filtering, and simulation of fault conditions. The design process requires thorough investigation of parameters like thyristor ratings, triggering circuits, cooling requirements, and protection against overvoltages. Fault cases are simulated using PSCAD software to analyze maximum current and voltage stresses on thyristor valves and harmonic filters. Reactor design must also account for current harmonics levels.
The document describes various electrical checks and measurements that can be performed on stator windings to assess the condition of the insulation system. These include:
1) Polarization-depolarization current analysis to evaluate time constants and indices related to insulation quality and moisture sensitivity.
2) Capacitance and tan delta measurements at different voltages to assess delamination, corona protection, and non-linear insulation behavior.
3) Analysis of partial discharge patterns to identify the nature of discharges.
4) Non-linear insulation behavior analysis to understand the effects of aging.
The results of these tests are used to evaluate the insulation system and estimate the remaining life expectancy of the windings.
Edwin Newsletter on transformer failures on 13 October 2015Edwin Low
The document discusses transformer failures and their investigation. It provides details on transformer types, components, and typical tests conducted during failure analysis. Two specific failure cases are described:
1) A dry transformer in a wind turbine failed during commissioning due to a manufacturing defect - a conductive winding turn was displaced and overlapped another turn, causing arcing during energization.
2) An oil-filled transformer failed due to inadequate mechanical strength holding the winding turns. An external fault caused electromechanical forces, displacing windings and exposing conductors between turns, leading to arcing at multiple points. The root cause was a manufacturing defect in the winding assembly.
Algorithem Algorithem and Programme for Computation of Forces Acting on line ...CSCJournals
The correct design and selection of line supports is of great importance for successful operation and safety of transmission lines. For this purpose various forces acting on the line supports must be estimated for normal and abnormal conditions of operation. The author develops algorithm and programme for optimal calculation of these forces, which the line supports should withstand. The main programme MDFLS and fourteen subroutines are constructed for calculation the forces acting on the line supports. The subroutines (FSUS, FDES, and FCSTA) are for determining the forces from line conductors and (FGWSU, FSWDE, FSWSA) from ground wires at suspension, dead end and strain/angle line supports respectively. The other eight are subsidiary subroutines. The parameters of the conductors (homogenous or non homogenous) are found by DPMPN and DPMPH. The physical-mechanical properties of the conductor are calculated using PMPL. The specific loadings are determined by RLOLC. The sag-tension calculations are prepared by subroutines CSCT, CSOP and SEQS. Subroutine FSPCB is for calculation of forces due to broken conductor at suspension support in the section. The elaborated programmes are written in FORTRAN 90 and adopted for personal computer.
Ground faults in generator stator and field/rotor circuits are serious events that can lead to damage, costly repair, extended outage and loss of revenue.
This paper explores advances in field/rotor circuit ground fault and stator ground fault protection. These advanced protection strategies employ AC injection and other tactics to provide benefits in security, sensitivity and speed.
Busbar protection uses differential protection to isolate faults on the busbar. It works by comparing the current entering and leaving the busbar using CTs - any difference indicates an internal fault. Proper CT ratios and a stabilizing resistance are needed to restrain operation for external faults. PS class CTs are preferred over other classes due to more consistent accuracy. While busbar protection is important, it is currently not implemented in line at MRSS due to some unspecified reason.
The document discusses testing of electric motor insulation systems. It provides information on:
1) Common causes of insulation failure like thermal aging, contamination, and overvoltage spikes. Over 80% of failures start as turn-to-turn faults.
2) Motors can experience voltage spikes over 5 per unit during start-up due to switching transients. This is enough to cause insulation breakdown.
3) Once turns fuse due to failure, the motor will fail rapidly due to high induced currents burning through the winding.
Testing methods like megohm testing, polarization index testing, and surge testing can evaluate insulation strength and detect early failures. Maintaining strong insulation is important for motor reliability.
Solid State Fault Current Limiter for Improvement of Smart Grid PerformanceIRJET Journal
This document summarizes research on using a solid state fault current limiter (SSFCL) to improve the performance of smart grids. It presents a simulation model of an SSFCL that uses thyristors to limit fault current. The SSFCL model is tested in a simulated smart grid system including generation, transmission and distribution assets with a 10MVA wind farm. Simulation results show that during a three-phase fault, the SSFCL is able to reduce the fault current from 45kA to 0.4A, demonstrating its effectiveness in limiting fault current to improve smart grid performance and stability.
This document discusses electrical protection systems for power stations. It explains the need for protection against faults like overcurrent and earth faults to isolate faulty equipment quickly. Detection of faults is done by measuring changes in current and voltage using transformers and relays. Different types of protection relays and schemes are described to discriminate faults and provide backup protection for transformers, circuits, busbars and generators.
The document describes various electrical checks and measurements that can be performed on stator windings to assess the condition of the insulation system. These include:
1) Polarization-depolarization current analysis to evaluate time constants and indices related to insulation quality and moisture sensitivity.
2) Capacitance and tan delta measurements at different voltages to assess delamination, corona protection, and non-linear insulation behavior.
3) Analysis of partial discharge patterns to identify the nature of discharges.
4) Non-linear insulation behavior analysis to understand the effects of aging.
The results of these tests are used to evaluate the insulation system and estimate the remaining life expectancy of the windings.
Edwin Newsletter on transformer failures on 13 October 2015Edwin Low
The document discusses transformer failures and their investigation. It provides details on transformer types, components, and typical tests conducted during failure analysis. Two specific failure cases are described:
1) A dry transformer in a wind turbine failed during commissioning due to a manufacturing defect - a conductive winding turn was displaced and overlapped another turn, causing arcing during energization.
2) An oil-filled transformer failed due to inadequate mechanical strength holding the winding turns. An external fault caused electromechanical forces, displacing windings and exposing conductors between turns, leading to arcing at multiple points. The root cause was a manufacturing defect in the winding assembly.
Algorithem Algorithem and Programme for Computation of Forces Acting on line ...CSCJournals
The correct design and selection of line supports is of great importance for successful operation and safety of transmission lines. For this purpose various forces acting on the line supports must be estimated for normal and abnormal conditions of operation. The author develops algorithm and programme for optimal calculation of these forces, which the line supports should withstand. The main programme MDFLS and fourteen subroutines are constructed for calculation the forces acting on the line supports. The subroutines (FSUS, FDES, and FCSTA) are for determining the forces from line conductors and (FGWSU, FSWDE, FSWSA) from ground wires at suspension, dead end and strain/angle line supports respectively. The other eight are subsidiary subroutines. The parameters of the conductors (homogenous or non homogenous) are found by DPMPN and DPMPH. The physical-mechanical properties of the conductor are calculated using PMPL. The specific loadings are determined by RLOLC. The sag-tension calculations are prepared by subroutines CSCT, CSOP and SEQS. Subroutine FSPCB is for calculation of forces due to broken conductor at suspension support in the section. The elaborated programmes are written in FORTRAN 90 and adopted for personal computer.
Ground faults in generator stator and field/rotor circuits are serious events that can lead to damage, costly repair, extended outage and loss of revenue.
This paper explores advances in field/rotor circuit ground fault and stator ground fault protection. These advanced protection strategies employ AC injection and other tactics to provide benefits in security, sensitivity and speed.
Busbar protection uses differential protection to isolate faults on the busbar. It works by comparing the current entering and leaving the busbar using CTs - any difference indicates an internal fault. Proper CT ratios and a stabilizing resistance are needed to restrain operation for external faults. PS class CTs are preferred over other classes due to more consistent accuracy. While busbar protection is important, it is currently not implemented in line at MRSS due to some unspecified reason.
The document discusses testing of electric motor insulation systems. It provides information on:
1) Common causes of insulation failure like thermal aging, contamination, and overvoltage spikes. Over 80% of failures start as turn-to-turn faults.
2) Motors can experience voltage spikes over 5 per unit during start-up due to switching transients. This is enough to cause insulation breakdown.
3) Once turns fuse due to failure, the motor will fail rapidly due to high induced currents burning through the winding.
Testing methods like megohm testing, polarization index testing, and surge testing can evaluate insulation strength and detect early failures. Maintaining strong insulation is important for motor reliability.
Solid State Fault Current Limiter for Improvement of Smart Grid PerformanceIRJET Journal
This document summarizes research on using a solid state fault current limiter (SSFCL) to improve the performance of smart grids. It presents a simulation model of an SSFCL that uses thyristors to limit fault current. The SSFCL model is tested in a simulated smart grid system including generation, transmission and distribution assets with a 10MVA wind farm. Simulation results show that during a three-phase fault, the SSFCL is able to reduce the fault current from 45kA to 0.4A, demonstrating its effectiveness in limiting fault current to improve smart grid performance and stability.
This document discusses electrical protection systems for power stations. It explains the need for protection against faults like overcurrent and earth faults to isolate faulty equipment quickly. Detection of faults is done by measuring changes in current and voltage using transformers and relays. Different types of protection relays and schemes are described to discriminate faults and provide backup protection for transformers, circuits, busbars and generators.
There are three main aspects of power system protection: normal operation, prevention of electrical failures, and mitigation of failure effects. Protective relaying is one feature aimed at minimizing equipment damage and service interruptions when failures occur. Relays have evolved from electromechanical to static and digital types. Overcurrent protection is used for phase and earth faults, with inverse-time curves allowing coordination between relays. Adequate grading margins must be provided between relay operations.
Mr. Veerabrahmam from PRDC has spoken about the transformers failures and few of the case studies. Few failures and reasons for failures are also discussed.
Importance on switchgear, its teatings commesioning
saving on losses instad of using stat delta starter use of VFDs with same operation but savings in losses
This document discusses overcurrent circuit protectors, including the differences between current cutoffs and current limiters. It describes various types of overcurrent protectors such as fuses, circuit breakers, PPTCs, CPTCs, LFRs, and ECLs. It provides details on thermal, magnetic, and thermal-magnetic circuit breakers. The document discusses important parameters for selecting protectors such as agency approvals, physical size, current and voltage ratings. It also covers fuse design details such as elements, materials, and I-t curves.
This document summarizes a research paper that proposes two methods for diagnosing stator short circuit faults in brushless DC motors: Adaptive Neuro-fuzzy Inference System (ANFIS) and wavelet-based fault diagnosis. ANFIS is a neural network combined with fuzzy logic that can model nonlinear functions. It is applied to diagnose faults based on motor parameters. Wavelet transforms are also used to analyze motor current signals and detect characteristic fault frequencies indicating shorts. The paper presents the modeling of a BLDC motor and discusses common motor faults before detailing the proposed ANFIS and wavelet approaches.
Dynamic Analysis and Testing of on-load tap changerLeonardo Nicolini
The dynamic resistance measurement (DRM) was developed to analyze the switching process of on-load tap changers (OLTCs), which have a high failure rate of around 30%. DRM allows detection of issues like arcing contacts or switching interruptions by measuring the fast switching process. To properly analyze DRM results, it is important to know the OLTC type and construction. DRM analysis focuses on features of the current curve during switching, like amplitude, which indicates contact resistance, and timing, which may show mechanical problems. Proper test currents around 3-5A provide a stable measurement. Shorting the secondary side increases sensitivity. Switching direction and tap position can impact results due to differences in winding configuration.
We are leading supplier of Bus Differential System protection and breaker failure for re-configurable MV, HV, EHV multi-section busbars.
GE provides enhanced reliability through advanced protection for a wide range of bus protection applications. Our highly skilled technology teams understand bus bar principles and protection techniques, and use them to support bus protection solutions that can be applied to a vast array of applications.
Contact us for any Enquiry of the above product on: +91-9819614841, +91-9833686249
or mail us on info@dsgenterprises.in
Know more at:https://www.dsgenterprises.in/alstom--ge/bus-protection
The power system is protected through a zone protection scheme where the system is divided into sections, with each zone having one or more protective relays coordinated with the overall protection system. The zones are arranged to overlap so that no part of the system remains unprotected, and circuit breakers are located in the overlapped regions. Protective relaying schemes must be reliable, selective, and fast acting. Reliability ensures the relay will operate correctly, selectivity allows the relay to distinguish faults inside and outside its zone, and speed minimizes fault duration and equipment damage. Modern high-speed relays have operating times of 1-2 cycles while circuit breakers have interrupting times of 2.5-3 cycles, resulting in total clearing
The document discusses various protection schemes for generators. It describes (1) differential protection that protects the stator winding from internal faults, (2) rotor earth fault protection that protects the rotor winding, and (3) loss of excitation protection that protects the power system from instability if the generator loses its field excitation. Various other protections discussed include overcurrent, overvoltage, temperature, and reverse power protections. The document provides details on the operating principles and components of these various generator protection schemes.
Fieldbus is the name of a family of an open, all-digital, serial, two-way, non-proprietary industrial computer network protocol that connect sensors, motors, switches, valves, actuators, and alarms to a distributed control system and Human Machine Interface (HMI). Devices on a field network and supports a wide range of architectures, for both safe and hazardous area applications. Instruments in a manufacturing plant are connected to the network in a variety of topologies including, star, ring, daisy-chain, tree and branch networks. Analogous to how a computer LAN works, a Fieldbus network allows a controller to communicate with hundreds of analog and digital sensing points.
The document outlines various components of a power system protection system. It discusses the need for protection to maintain reliable power supply and minimize equipment damage. The key elements to be protected include generators, transformers, transmission lines, and busbars. Protection schemes for each element are then described, such as differential protection for generators and transformers, Buchholz relays for transformers, and distance and line differential protection for transmission lines.
Out of phase current switching in High Voltage Circuit BreakersAli Sepehri
Out-of-phase switching occurs when two power systems or a generator and power system are connected with a phase angle difference between their voltages. This causes out-of-phase currents that a circuit breaker must interrupt. The transient recovery voltage (TRV) under out-of-phase conditions has a very high peak but moderate rate of rise and current. Examples where out-of-phase switching may occur include accidentally connecting a generator at the wrong phase angle or two power systems losing synchronization due to a fault. Proper protection, synchronization, and circuit breaker design are needed to safely handle out-of-phase switching conditions.
Amplitude and phase comparators
Over current relays
Directional relays
Distance relays
Differential relay.
Static Relays: Comparison with electromagnetic relay
Classification and their description
Over current relays
Directional relay
Distance relays
Differential relay
Protective relays are used to isolate faults in electrical systems and protect equipment from damage. There are different types of relays including electromagnetic, solid-state, and microprocessor-based relays. Relays are used for motor protection including overload protection, locked rotor protection, and single phase/unbalance protection. Transformer protection includes gas and temperature monitoring as well as differential and ground fault protection. Generator protection includes differential, ground fault, and negative sequence protection to prevent phase unbalancing.
Example of Substation Maintenance & Assessment Audits for Training - Niels In...Niels Inderbiethen
This is a good example of an audit which explores all the substation attributes, equipment & maintenance requirements and is usually the basis for creating a professional site specific Training Manual which I then finalize with the client and prepare the documentation for formal training of any new staff to the plant, together with Regulations & ORHVS training. This documentation can then also be forwarded to the SETA & SAQA for formalization and educational points allocation. It also forms a critical part of any plants record keeping requirements and plant maintenance inspections and complies with regulatory and annual legislation of any mandatory records of status and investigations of equipment. - Please note that this document is only published to showcase my work - any use, distribution, copying or any other sort of media use is prohibited as the contents are owned by Siemens and the equipment is covered by patents and the report is covered by copyrights. I appreciate your commitment to this understanding.
This document discusses implementing a secure environment for Microsoft and Linux clients to access a heterogeneous network. It proposes designing a system that integrates information and centralizes network support to reduce costs and increase control. It describes security features of Microsoft ISA servers, such as firewalls and caching, and how they monitor traffic. It also discusses benefits of Linux file and FTP servers for centralized file storage, backup, and sharing over private and public networks. The purpose is to create a collaborative multi-platform network environment between Windows and Linux systems.
The document provides information about night photography techniques. It discusses planning night shoots by scouting locations during the day and considering lighting conditions. Moonlight, flashlights, and torchlights can be used to illuminate subjects. Long exposures require a tripod, cable release, low ISO, and painting subjects with light sources. Trial and error is needed to get correct exposures. Essential gear includes a camera with bulb mode, tripod, and light sources.
This document summarizes a research paper on generating random regions in a spatial cloaking algorithm to preserve location privacy. The paper proposes two algorithms - the first provides a direct list of locations ordered by proximity, while the second generates regions of different shapes to minimize the chances of a user's location being disclosed. Spatial cloaking techniques blur a user's exact location into a cloaked region to satisfy privacy requirements like k-anonymity. The paper presents a system model where users communicate directly with location-based services instead of through peers, and describes how queries are processed by the services to search for points of interest within cloaked regions.
IOSR Journal of Electronics and Communication Engineering(IOSR-JECE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of electronics and communication engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electronics and communication engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
There are three main aspects of power system protection: normal operation, prevention of electrical failures, and mitigation of failure effects. Protective relaying is one feature aimed at minimizing equipment damage and service interruptions when failures occur. Relays have evolved from electromechanical to static and digital types. Overcurrent protection is used for phase and earth faults, with inverse-time curves allowing coordination between relays. Adequate grading margins must be provided between relay operations.
Mr. Veerabrahmam from PRDC has spoken about the transformers failures and few of the case studies. Few failures and reasons for failures are also discussed.
Importance on switchgear, its teatings commesioning
saving on losses instad of using stat delta starter use of VFDs with same operation but savings in losses
This document discusses overcurrent circuit protectors, including the differences between current cutoffs and current limiters. It describes various types of overcurrent protectors such as fuses, circuit breakers, PPTCs, CPTCs, LFRs, and ECLs. It provides details on thermal, magnetic, and thermal-magnetic circuit breakers. The document discusses important parameters for selecting protectors such as agency approvals, physical size, current and voltage ratings. It also covers fuse design details such as elements, materials, and I-t curves.
This document summarizes a research paper that proposes two methods for diagnosing stator short circuit faults in brushless DC motors: Adaptive Neuro-fuzzy Inference System (ANFIS) and wavelet-based fault diagnosis. ANFIS is a neural network combined with fuzzy logic that can model nonlinear functions. It is applied to diagnose faults based on motor parameters. Wavelet transforms are also used to analyze motor current signals and detect characteristic fault frequencies indicating shorts. The paper presents the modeling of a BLDC motor and discusses common motor faults before detailing the proposed ANFIS and wavelet approaches.
Dynamic Analysis and Testing of on-load tap changerLeonardo Nicolini
The dynamic resistance measurement (DRM) was developed to analyze the switching process of on-load tap changers (OLTCs), which have a high failure rate of around 30%. DRM allows detection of issues like arcing contacts or switching interruptions by measuring the fast switching process. To properly analyze DRM results, it is important to know the OLTC type and construction. DRM analysis focuses on features of the current curve during switching, like amplitude, which indicates contact resistance, and timing, which may show mechanical problems. Proper test currents around 3-5A provide a stable measurement. Shorting the secondary side increases sensitivity. Switching direction and tap position can impact results due to differences in winding configuration.
We are leading supplier of Bus Differential System protection and breaker failure for re-configurable MV, HV, EHV multi-section busbars.
GE provides enhanced reliability through advanced protection for a wide range of bus protection applications. Our highly skilled technology teams understand bus bar principles and protection techniques, and use them to support bus protection solutions that can be applied to a vast array of applications.
Contact us for any Enquiry of the above product on: +91-9819614841, +91-9833686249
or mail us on info@dsgenterprises.in
Know more at:https://www.dsgenterprises.in/alstom--ge/bus-protection
The power system is protected through a zone protection scheme where the system is divided into sections, with each zone having one or more protective relays coordinated with the overall protection system. The zones are arranged to overlap so that no part of the system remains unprotected, and circuit breakers are located in the overlapped regions. Protective relaying schemes must be reliable, selective, and fast acting. Reliability ensures the relay will operate correctly, selectivity allows the relay to distinguish faults inside and outside its zone, and speed minimizes fault duration and equipment damage. Modern high-speed relays have operating times of 1-2 cycles while circuit breakers have interrupting times of 2.5-3 cycles, resulting in total clearing
The document discusses various protection schemes for generators. It describes (1) differential protection that protects the stator winding from internal faults, (2) rotor earth fault protection that protects the rotor winding, and (3) loss of excitation protection that protects the power system from instability if the generator loses its field excitation. Various other protections discussed include overcurrent, overvoltage, temperature, and reverse power protections. The document provides details on the operating principles and components of these various generator protection schemes.
Fieldbus is the name of a family of an open, all-digital, serial, two-way, non-proprietary industrial computer network protocol that connect sensors, motors, switches, valves, actuators, and alarms to a distributed control system and Human Machine Interface (HMI). Devices on a field network and supports a wide range of architectures, for both safe and hazardous area applications. Instruments in a manufacturing plant are connected to the network in a variety of topologies including, star, ring, daisy-chain, tree and branch networks. Analogous to how a computer LAN works, a Fieldbus network allows a controller to communicate with hundreds of analog and digital sensing points.
The document outlines various components of a power system protection system. It discusses the need for protection to maintain reliable power supply and minimize equipment damage. The key elements to be protected include generators, transformers, transmission lines, and busbars. Protection schemes for each element are then described, such as differential protection for generators and transformers, Buchholz relays for transformers, and distance and line differential protection for transmission lines.
Out of phase current switching in High Voltage Circuit BreakersAli Sepehri
Out-of-phase switching occurs when two power systems or a generator and power system are connected with a phase angle difference between their voltages. This causes out-of-phase currents that a circuit breaker must interrupt. The transient recovery voltage (TRV) under out-of-phase conditions has a very high peak but moderate rate of rise and current. Examples where out-of-phase switching may occur include accidentally connecting a generator at the wrong phase angle or two power systems losing synchronization due to a fault. Proper protection, synchronization, and circuit breaker design are needed to safely handle out-of-phase switching conditions.
Amplitude and phase comparators
Over current relays
Directional relays
Distance relays
Differential relay.
Static Relays: Comparison with electromagnetic relay
Classification and their description
Over current relays
Directional relay
Distance relays
Differential relay
Protective relays are used to isolate faults in electrical systems and protect equipment from damage. There are different types of relays including electromagnetic, solid-state, and microprocessor-based relays. Relays are used for motor protection including overload protection, locked rotor protection, and single phase/unbalance protection. Transformer protection includes gas and temperature monitoring as well as differential and ground fault protection. Generator protection includes differential, ground fault, and negative sequence protection to prevent phase unbalancing.
Example of Substation Maintenance & Assessment Audits for Training - Niels In...Niels Inderbiethen
This is a good example of an audit which explores all the substation attributes, equipment & maintenance requirements and is usually the basis for creating a professional site specific Training Manual which I then finalize with the client and prepare the documentation for formal training of any new staff to the plant, together with Regulations & ORHVS training. This documentation can then also be forwarded to the SETA & SAQA for formalization and educational points allocation. It also forms a critical part of any plants record keeping requirements and plant maintenance inspections and complies with regulatory and annual legislation of any mandatory records of status and investigations of equipment. - Please note that this document is only published to showcase my work - any use, distribution, copying or any other sort of media use is prohibited as the contents are owned by Siemens and the equipment is covered by patents and the report is covered by copyrights. I appreciate your commitment to this understanding.
This document discusses implementing a secure environment for Microsoft and Linux clients to access a heterogeneous network. It proposes designing a system that integrates information and centralizes network support to reduce costs and increase control. It describes security features of Microsoft ISA servers, such as firewalls and caching, and how they monitor traffic. It also discusses benefits of Linux file and FTP servers for centralized file storage, backup, and sharing over private and public networks. The purpose is to create a collaborative multi-platform network environment between Windows and Linux systems.
The document provides information about night photography techniques. It discusses planning night shoots by scouting locations during the day and considering lighting conditions. Moonlight, flashlights, and torchlights can be used to illuminate subjects. Long exposures require a tripod, cable release, low ISO, and painting subjects with light sources. Trial and error is needed to get correct exposures. Essential gear includes a camera with bulb mode, tripod, and light sources.
This document summarizes a research paper on generating random regions in a spatial cloaking algorithm to preserve location privacy. The paper proposes two algorithms - the first provides a direct list of locations ordered by proximity, while the second generates regions of different shapes to minimize the chances of a user's location being disclosed. Spatial cloaking techniques blur a user's exact location into a cloaked region to satisfy privacy requirements like k-anonymity. The paper presents a system model where users communicate directly with location-based services instead of through peers, and describes how queries are processed by the services to search for points of interest within cloaked regions.
IOSR Journal of Electronics and Communication Engineering(IOSR-JECE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of electronics and communication engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electronics and communication engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of mechanical and civil engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in mechanical and civil engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
The Commonwealth Fund 2015 International Health Care Policy Survey of Primary...Odyssey Recruitment
This study looks at primary care services in industrialised countries comparing access to the various systems. Switzerland and Germany have the best results with swift access to Family Physicians.
The document describes the Tree Based Itinerary Design (TBID) algorithm for wireless sensor networks. The TBID algorithm partitions the sensor network area around the processing element into concentric zones. It then constructs itineraries for multiple mobile agents to efficiently collect and aggregate data from the sensor nodes. The algorithm builds trees connecting sensors in each zone and determines low-cost traversal orders for the mobile agents. Experimental results show that the aggregation time increases as the number of sensors or zones increases, but decreases as more mobile agents are used.
The document summarizes a research paper on developing an automatic reconfiguration technique for large scale reliable storage systems using a membership service (MS) and database query service (dBQS). The MS monitors membership changes and dBQS automatically reconfigures the system. Two algorithms are developed for the MS and dBQS provides Byzantine fault tolerance. Experimental results show the MS can manage large systems and reconfigurations have low overhead.
This document discusses various soft computing techniques for iris recognition, specifically focusing on two neural network approaches: Competitive neural network Learning Vector Quantization (LVQ) and Adaptive Resonance Associative Map (ARAM). It provides an overview of iris recognition as a biometric method, summarizes preprocessing steps like localization, segmentation, and normalization of iris images. It also describes feature extraction and matching steps. Finally, it defines artificial neural networks and discusses how LVQ and ARAM can be used for pattern matching in iris recognition applications.
This document discusses a system called Nymble that allows servers to blacklist misbehaving anonymous users of anonymizing networks like Tor while still preserving the anonymity of blacklisted users. Nymble uses pseudonyms called nymbles that are computationally difficult to link, simulating anonymous access. However, servers can blacklist users by obtaining a seed to link future nymbles from that user, blocking them specifically. This allows servers to deny access to misbehaving anonymous users without knowledge of their IP addresses, addressing the problem where servers currently block all exit nodes of anonymizing networks in response to misuse.
Estimation of Metric Distance of Observations from the Average ScoreIOSR Journals
This document proposes a method to estimate the "metric distance" of observations from the average score in a population. Metric distance is defined as the number of subjects whose scores are lower or higher than a given subject's score relative to the average. Formulas are developed to calculate the metric distance and its variance for each subject. Hypothesis tests are proposed to test if a subject's metric distance is equal to a given value or to test if two subjects' metric distances are the same. The method is intended to help determine how many subjects are above or below average compared to a reference subject.
This document analyzes the growth and productivity of Indian sugar companies from 2001-2002 to 2010-2011. It finds that northern Indian sugar companies generally saw higher annual growth rates in key metrics like net worth, sales, profits, and raw materials consumption compared to southern companies, driven by better rainfall and irrigation. Regression analysis showed raw materials and other variables like capital and labor contributed 99% to a company's output. The study aims to help improve sugar industry productivity in India by analyzing productivity ratios and trends over time.
A Secure Model for Cloud Computing Based Storage and RetrievalIOSR Journals
This document proposes a secure model for cloud computing storage and retrieval that separates these functions between two cloud providers. Specifically, it suggests that one provider handle storage only, while another handles only encryption and decryption. This separation prevents both functions and access to the raw data from being handled by a single administrator, improving security. The model is demonstrated using a customer relationship management (CRM) service example. It also discusses establishing service level agreements between the involved parties to formalize their roles and responsibilities.
Focused Exploration of Geospatial Context on Linked Open DataThomas Gottron
Talk at IESD 2014 workshop in Riva del Garda (at ISWC).
Abstract The Linked Open Data cloud provides a wide range of different types of information which are interlinked and connected. When a user or application is interested in specific types of information under time constraints it is best to ex- plore this vast knowledge network in a focused and directed way. In this paper we address the novel task of focused exploration of Linked Open Data for geospatial resources, helping journalists in real-time during breaking news stories to find contextual geospatial information related to geoparsed content. After formalising the task of focused exploration, we present and evaluate five approaches based on three different paradigms. Our results on a dataset with 425,338 entities show that focused exploration on the Linked Data cloud is feasible and can be implemented at very high levels of accuracy of more than 98%.
The document discusses higher education in India and the ongoing debate around quantity versus quality. It notes that while India has greatly expanded access to higher education since independence, issues of quality, equity and inclusion remain challenges. The document examines some of the key issues facing higher education in India, including the complexity of the federal system, funding challenges, quality assurance, and meeting the demands of the knowledge economy. It recommends reforms to admission and evaluation processes, greater use of technology and collaboration between institutions, and continued policy reforms to improve the standard and competitiveness of higher education in India.
IOSR Journal of Mathematics(IOSR-JM) is an open access international journal that provides rapid publication (within a month) of articles in all areas of mathemetics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in mathematics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
IRJET- Study Over Current Relay (MCGG53) Response using Matlab ModelIRJET Journal
This document describes a study of overcurrent relay response using MATLAB modeling. It presents the design of a MATLAB GUI to model various overcurrent relay characteristics and determine relay parameters. The study then examines coordination of overcurrent relays on a system by determining the time multiplier setting, plug setting, and operating time of different relays to ensure selectivity without sacrificing sensitivity or fault clearance time. Simulation results show the operating times vary according to the relay characteristics, with extremely inverse having the shortest time followed by very inverse and standard inverse. Proper coordination of these relay characteristics is important for protection.
1. Custom power devices condition power for medium-voltage distribution systems between 1-38kV and over 500kVA to protect entire facilities.
2. Static VAR compensators, static shunt compensators, and static series compensators are types of custom power devices that regulate voltage and compensate for reactive power.
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Proposal Technique for an Static Var Compensator
1. IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)
e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 7, Issue 5 (Sep. - Oct. 2013), PP 01-07
www.iosrjournals.org
www.iosrjournals.org 1 | Page
Proposal Technique for an Static Var Compensator
1
V.N.Ganesh, 2
S.Periasamy, 3
D.Sivakumar,
EEE department, Assistant professor, SRM University,
EEE Department, Assistant professor, SRM University,
EEE Department, Assistant professor, SRM University,
Abstract: This paper deals with the preliminary design of an SVC, which is the most important part of the
design process, because any specific error in the preliminary design and specifications in requirements
documents may end up with great amount of money, labour and time loss. The following subjects have to be
investigated thoroughly in order to finalize the preliminary design of an SVC. In this paper the following
parameters like Single thyristor operation, Series thyristor operation, Single Piece / Two Pieces Reactor
Arrangements are considered for the design procedure and the fault cases simulated in PSCAD concerning
three phase connections.
I. Introduction
Power quality of the supply busbar is determined by field measurements. The standards concerning
power quality and SVCs should be investigated in order to define and consider any power quality issues.
Currently valid regulations for reactive energy limits and other power quality issues may differ from one
country to another.
1.1 Load Characteristics
Whenever a TCR based SVC project is initiated, it is necessary to define the load characteristics
clearly. The precise load characteristics are evaluated by using: Field measurement by data acquisition,
Monthly electrical energy bills. Flicker performance, shunt filter and reactor sizing depend on these variations.
If the load is varying slowly, the control system design does not have a great impact on the design. Duty cycle
and load unbalance also plays a significant role in the design. The negative sequence compensation is a
challenge in TCR design as mentioned in [1, 2]. The methodology of load identification is also advised in the
standards [3] for Transmission SVCs.
1.2 Project Requirements
The customers may require some flexible solutions because of the future plans for the enterprise that
the SVC is installed. Capacity of the plant may change so that a modular/flexible SVC may be required instead
of a fixed installation capacity.
1.3 Environmental and Operational Conditions
The following environmental conditions are needed to be considered for the robustness of the SVC
installation: Maximum and minimum values of ambient temperature, Humidity, Snow load, Pollution level
1.4 Design of the Power Stage
1.4.1 Single Thyristor Operation
The Thyristor is the “static switch” part of a TCR based SVC. The current flowing through the reactors
is adjusted by thyristor valves. They are connected back-to-back and may share the same snubber. Selection of
the thyristors and snubbers depends on many parameters. In order to verify the selection, a computer simulation
is appropriate. In Fig.1.1, a typical thyristor valve can be seen. A thyristor needs to be triggered into conduction,
therefore the electronic triggering circuit design is also important as well as the thyristor selection. Some failures
may occur if triggering circuit is not designed carefully. A detailed thyristor selection analysis can be found in
[5]. In order to be able to select the thyristors, the following information in thyristor data sheets, such as the one
in[6], should be investigated:
2. Proposal Technique For An Static Var Compensator
www.iosrjournals.org 2 | Page
Fig1.1 A typical back to back connected thyristor valve
1.5.2 Reverse Blocking Voltage and Off state
V
DRM
is the repetitive peak off state voltage and V
RRM
is the repetitive peak reverse voltage. V
DRM
and
V
RRM
can be different from each other according to the thyristor selected.
1.5.3 di/dt and dv/dt
During the triggering of the thyristor, the region of the gate connection carries the thyristor current and
then spreads over the whole wafer area. In order to avoid excessive dissipations during this operation, the
amplitude of this current should be limited. di/dt is defined for the switching instants, and once the conduction
starts, it is not limited to a specific value. Operating frequency, peak value of permissible on state current for
half sine wave, gate triggering current and the rate of rise of gate current are given in datasheets for the
definition of di/dt. If the dv/dt value defined by the producers is exceeded, the thyristor self triggers which lead
to a break down in the wafer. Therefore, dv/dt should be limited to a safe value by using passive devices such as
snubbers.
1.5.4 Cooling Method
Cooling method is selected according to the level of power dissipation and available resources. The
major cooling types are: Natural air cooling, Forced air cooling and Liquid based cooling (de-ionized water or
other coolant). Heatsink selection depends on the cooling method. The heatsinks carry the thyristor current;
therefore they are selected from good electrical and heat conducting materials, usually aluminum or copper.
1.5.5 Thermal Considerations
Theoretically, a TCR produces reactive power only. However in the practical implementation, there are
many sources of dissipation. In addition to the copper losses of reactor banks, thyristor stack is also source of
dissipation, not only because of the voltage drop on the thyristors, but also because of the passive elements
connected to the stack. The main sources of dissipation can be classified as: Thyristor losses (conduction,
switching and off state losses), Snubber losses, Equalizing resistor losses, Valve reactor losses (if present),
Protection circuit losses, Gate triggering circuit losses, Bus bar or cable losses
The method of calculating the thyristor valve losses are defined in [4] Annex C. In this standard,
however protection circuit, gate triggering circuit and bus bar losses are omitted in the calculation of thyristor
valve losses because in high power applications these issues are negligible. Therefore, thyristor valve total
power loss, P
valve
, is given in [4] as:
P
valve
= P
cvalve
+ P
Tsw
+ P
vd
+ P
sn
+ P
hyst
(1.1)
P
cvalve
is thyristor valve conduction losses, P
Tsw
is thyristor total switching losses, P
vd
is equalizing
losses, P
sn
is snubber circuit losses, and P
hyst
is reactor (hysteresis) losses. Prolonged thermal stress on the
thyristors is not desired. The effects of such thermal stress can lead to thermal fatigue, or an earlier failure of the
thyristor, which is discussed in [9].
1.5.6 Snubber Circuit
The series inductance of the circuit, combined with the rate of rise of the current, produces transient
voltage peaks across the thyristor terminals. If voltage exceeds the thyristor ratings, it may lead to the
destruction of the device permanently. Therefore, in order to dampen the voltage overshooting a parallel R-C
snubber circuit is connected as a general practice [1].
The snubber values are usually selected to keep the circuit response critically damped. Increasing the
damping level leads to more dissipation. A detailed snubber design can be found in [5].
3. Proposal Technique For An Static Var Compensator
www.iosrjournals.org 3 | Page
1.5.7 Triggering Circuit
Triggering circuits usually have dual tasks, primarily isolation and secondarily supplying the gate
current necessary to switch on the thyristor. The isolation can be achieved by magnetically or optically. Pulse
transformers suitable for transmitting high current and high frequency pulses are may be used for magnetic
isolation. In medium voltage applications pulses are usually transmitted to the gate by a ferrite core placed
around a single wire carrying the low voltage side current. There is isolation material around the primary
conductor.
Optical isolation is achieved through optical fibres (F/O). However triggering circuit with F/O requires
a gate energy circuit in order to be able to supply the current pulse necessary for the gate.
1.5.8 Overvoltage protection
Overvoltage in an SVC system usually occurs in a temporary fault condition such as a lightning surge.
Temporary overvoltage cases needs fast interaction and protection, therefore they are handled by the
overvoltage protection circuits which are usually placed in or near the thyristor triggering circuits. In a series
thyristor operation, equalizing resistor circuits or some of the series thyristors may breakdown. This may impose
overvoltages on the remaining of the valve circuit. Overvoltage protection triggers rest of the thyristors to
conduction thus protecting them against the overvoltage.
Breakover diodes (BOD), avalanche type diodes or metal oxide varistors (MOV) are used in
overvoltage protection circuits. Such implementations can be found in [7] with a BOD, and in [5] with a MOV.
Continuous operating voltages may sometimes rise above the standard levels defined in [8]. If such an
overvoltage occurs, the control system must react to this type of fault.
1.6 Series Thyristor Operation
Series thyristor operation requires additional design work. Connecting semiconductor devices in series
or in parallel requires special attention on voltage and current sharing. A failure in balancing the current or
voltage may lead to the failure of the whole stack.
Design and implementation of series operation of thyristors are discussed in [5]. The same
design is also used in the utilization of the ISDEMIR ladle furnace compensation system. In Fig.1.2 the series-
connected thyristors are seen. Cooling water flows through the heatsinks, not only cooling the thyristors but also
cooling the snubber circuits. The operation voltage of 6.3kV requires special attention to the insulation. The
distance between the high voltage switches and other equipment is selected by considering the safe values and
pulse transformers are placed at the back of the insulating separator thus avoiding flashovers to the control
circuit.
Fig.1.2 A thyristor stack which consists of series connected thyristors. (a): with antiparallel connected switches.
(b) with positive and negative thyristors grouped
1.7 Single Piece / Two Pieces Reactor Arrangement
In order to protect the Thyristor valves against a short circuit, the reactors can be divided into two series
reactors having the same total phase reactance. Connecting the Thyristor valves in between these series reactors
will limit the maximum fault currents. If one reactor is short circuited, the fault current will be limited. If phase
is short circuited, no fault current will flow through thyristors. In order to observe a total short circuit current,
each reactor placed on top of one another should be
separately short circuited, which has a very low probability in a TCR installation because of the geometry.
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Fig.1.3 Reactor arrangement; (a) Single piece, (b) two pieces
Several fault cases that can appear in a delta connected TCR are given in Fig. 1.4, 1.5 and 1.6. These
cases are simulated for a 1 kV 1,5 MVAr TCR + 0,75 kVAr Filtre installation with a short circuit 525 MVA .
Filters consist of three 5
th
harmonic and three 7
th
harmonic tuned filters at 1 kV side. A feature of PSCAD called
“Multirun” is used for multiple simulations. The results are given in Table 1.1. The worst case is found to be a
short circuit across the upper or lower piece of the reactor.
Fig.1.4 PSCAD Multirun (Multiple Simulation) for different fault types
Table.1.1. PSCAD Multirun simulation results
Cas
e
Maximum 5th
Harmonic Filter
Current (kA)
Maximum 5th
Harmonic Filter
Capacitor
Voltage (kV)
Maximum 7th
Harmonic Filter
Current (kA)
Maximum 7th
Harmonic Filter
Capacitor
Voltage (kV)
Maximum TCR
Line current
(kA)
Maximum TCR
Thyristor
current (kA)
1 0,4760 0,9582 0,4296 1,0245 26,7383 0,7590
2 0,1383 0,5457 0,0927 0,5009 33,7312 0,9013
3 0,1276 0,8337 0,0832 0,8152 27,5715 0,7833
4 0,2920 0,4659 0,2629 0,4559 39,4042 0,6918
5 0,1333 0,8257 0,0877 0,8005 1,4378 1,6126
6 0,1260 0,8171 0,0826 0,7959 1,7268 1,8834
7 0,1277 0,8336 0,0832 0,8151 1,0207 1,0602
8 0,1300 0,8090 0,0855 0,7799 2,5117 1,8673
9 0,1266 0,8253 0,0828 0,8054 1,1658 1,1886
10 0,1277 0,8336 0,0832 0,8151 1,0207 1,0602
11 0,1303 0,8294 0,0853 0,8070 1,0265 0,7659
12 0,1281 0,8252 0,0836 0,8029 1,2619 1,0690
Fig.1.5 Fault cases simulated in
PSCAD concerning three phase
connections
Fig.1.6 Fault cases simulated
in PSCAD concerning one
phase and two thyristor
terminal connections
belonging different phases
Fig.1.7 Fault cases simulated
in PSCAD concerning three
thyristor terminals belonging
different phases
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1.8 Reactor Design
Reactor design for the SVC TCR and shunt filters require special attention to current harmonics and
voltage harmonics levels because dissipations in the reactors may be higher than the standard shunt reactors.
The Standard IEC 289 [15] gives the definitions and suggestions for shunt reactors. IEEE standards [10-14] give
detailed information on reactors and their requirements. IEEE Std C57-120-1991 [14] contains the loss
calculations while [12] proposes the test procedures for reactors.
The following should be conducted by the customer to the manufacturer when a reactor is to be designed:
Standard (generally IEC 60289), air-cored / iron cored, Frequency, Rated voltage (line-line or phase, rms,
default IEC 38), Max.continuous operating voltage (kV), Rated inductance per phase (mH), Rated continuous
current (kA), Max. continuous current (kA), TDD, Short circuit power before reactor, Outdoor/indoor
installation, Insulation class, Cooling type, Maximum ambient temperature, Tuning frequency (If connected in
a shunt filter, Hz), Quantity and construction details (including terminal connections and mounting style such as
top-to-top or independent). The reactor ratings should be verified by a power system simulation tool. In the
simulation, worst case scenarios such as misfiring (where conduction per thyristor is longer than 180o) and short
circuits can be investigated. The manufacturers determine the minimum safe distance to other magnetic material
and closed loop conductors. These magnetic clearances around the reactor depend on the individual reactor
design and. should be taken into account in the layout of the overall system.
1.9 Harmonic Filter Design
The SVC topology is important in the decision for filtering. The complete SVC topology should be
selected before starting the frequency response analysis.
1.9.1 Frequency Response of the Filters
Thyristor controlled reactor (TCR) acts as a harmonic current source and produces its own odd
harmonic current components (3
rd
, 5
th
, 7
th
, 9
th
, 11
th
, etc.) for symmetrical triggering in the steady-state. However,
during control, firing angle will change from positive half-cycle to negative half-cycle resulting in production of
even harmonics (2
nd
, 4
th
, etc.). These even harmonics are taken as temporary overloads on filter reactors and
capacitors. In a delta connected TCR, triple harmonics do not appear in the line currents for symmetrical
triggering in the steady state. They will circulate through the delta connected reactor bank. However, in transient
state owing to control, unbalanced portion of triple harmonics will be reflected to the line side. These temporary
overloads on filter elements are taken into account by safety margins in the design. An important phenomenon
of TCR operation during firing angle control from positive half-cycle to negative half-cycle is the generation of
direct current component. This may move the magnetic operating point on the B-H characteristics of SVC
transformer and thyristor controlled reactors for the iron core case. Therefore, the linearity of TCR core is
essential for iron-core solution. Simulations should be carried out according to this assumption in order to find
out harmonic loadings on filter elements. Filter circuits can be designed according to the rules described in IEC
61642 [16]. The loads are taken as harmonic current sources in simulation, which inject 1.0 A rms at all
harmonic frequencies.
1.10 TCR Control
Thyristor controlled reactor is a variable susceptance that can be controlled by triggering delay of the
thyristor gate signals. The control system varies according to the desired method of TCR implementation. These
methods are discussed in the below section.
1.11 Control System Overview
Control system that is only designed for reactive power compensation is a simple controller that
calculates the necessary firing angle of each phase. It is also acceptable if all three phases are fired with the
same angle. This type of control achieves reactive power compensation; however it is capable of neither load
balancing nor voltage regulation. Control system design can easily be implemented by using proportional-
integral (PI) controller in such an SVC. This type of control can be seen in Fig.1.8. In order to be able to achieve
load balancing, the negative sequence of the load current must be removed entirely.
Reactive current component calculation and reactive power calculations can be evaluated by using 50
Hz averaging. This method will cause responses in the TCR because 50Hz averaging method will require time
to take the average value of the signal.
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Fig.1.8 Simple reactive power compensation by PI controller
Fig.1.9 Reactive power compensation with load balancing by PI controller
Fig.1.10 Flicker Compensation System with feed-forward and feed-back control
1.12 Thyristor Valve Control and Misfiring
Ideal TCR line currents are 90
o
displaced from the line voltage and they are symmetrical and balanced
if the firing delay angle is in the range of 90
o
-180
o
for positive half cycle and 270
o
-360
o
in the negative half
cycle. These are the safe operating regions of TCR, which are the 2
nd
and the 4
th
regions shown in Fig.1.11.
Whenever the conduction angle of a thyristor exceeds 180
o
, a DC current component exists. In a non-ideal TCR
which includes an internal resistor, the firing delay angle can be reduced below 90
o
. The exact angle can be
calculated from the inductive reactance and the resistance of the TCR.
Fig.1.11. Firing Delay Angle (α) versus TCR line voltage. The safe operating regions 2 and 4 of TCR are
marked and Unsafe operating regions 1and 3 are marked.
II. Conclusion:
From the implemented tests and procedure, it can be concluded that the design of SVC in
transmission lines offers controlling the power flow in an efficient manner. The TCR simulation for a 1 kV 1,5
MVAr TCR + 0,75 kVAr Filter installation with a short circuit 525 MVA was tested and shown in this paper
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using PSCAD “Multirun” simulator. In order to be able to achieve load balancing, the negative sequence of the
load current must be eliminated completely. Control system design can easily be implemented by using
proportional-integral (PI) controller in such an SVC.
References
[1] T.J.E. Miller, “Reactive Power Control In Electric Systems,”, John Wiley&Sons, 1982.
[2] J.Arrilaga, N.R. Watson, “Power System Harmonics”, Wiley, 1982
[3] “IEEE Guide for the Functional Specification of Transmission Static Var Compensators” IEEE Std 1031-1991)
[4] “IEEE Guide for the Functional Specification of Transmission Static Var Compensators” IEEE Std 1031-2000 (Revision ofIEEE
Std 1031-1991)
[5] M.V. Utalay, “Design and Implementation of a Medium Voltage Thyristor Controlled Reactor”, MSc. Thesis, METU, Jan.1996
[6] Semikron Power Electronics Catalogue,Semikron Inc. Germany, 10/1998.
[7] Lawatsch, H.M.; Vitins, J.; “Protection of thyristors against overvoltage with breakover diyotes”, IEEE Transactions on Industry
Applications Volume 24, Issue 3, May-June 1988 pp. 444 – 448
[8] TS 831, “Standard Voltages in THE Distribution Systems” , 1979
[9] “Effects of Temperature on Thyristor Performance” Application Note AN4870, Dynex Semiconductors, January 2000.
[10] ANSI/IEEE Std. C37.109, “IEEE Guide for the Protection of Shunt Reactors” 1988
[11] IEEE Std. C57-114, “IEEE Seismic Guide for Power Transformers and Reactors”, 1990
[12] IEEE Standard Requirements,Terminology, and Test Code for Shunt Reactors Rated Over 500 kVA, IEEE Std. C57.21-1990
[13] IEEE Std. C57-125, “IEEE Guide for Failure Investigation, Documentation,and Analysis for Power Transformers and Shunt
Reactors” 1991
[14] “IEEE Loss Evalution Guide for Power Transformers and Reactors” IEEE Std C57-120-1991
[15] IEC 60289 “Reactors”,1988
[16] IEC 61642 Industrial a.c. Networks Affected by Harmonics - Application of Filters and Shunt Capacitors