Power System Relaying Committee Research Articles

Advancements in Centralized Protection and Control Within a Substation

Smart-grid development focusing on renewable energy sources is changing power system characteristics at a time when utilities are also focusing on improving customer service and resiliency of the grid. All of these activities require renewed attention to safety, protection, and control strategies that take advantage of available technologies while promoting newer ones. To explore better utilization of present technologies and chart the development of next generation protection and control technologies, the IEEE Power System Relaying Committee formed a working group to prepare a report describing and analyzing state-of-the-art and emerging technologies for centralized protection and control within a substation. When appropriately applied, these novel practical technologies may significantly improve the reliability of protection and control systems and the power grid. This paper reviews the key advancements in centralized protection and control systems.

Current Transformer Saturation Effects on Coordinating Time Interval

The primary function of protective devices is to remove faulted equipment from the electrical system. It is typically very advantageous for these devices to isolate as small of a section of the electrical system as possible. Overcurrent protection is the most common protection function used, as faulted equipment typically results in a large short circuit current. When overcurrent protection is employed, the overcurrent protection is typically coordinated with time so that the devices closest to the fault will operate and isolate only that section of equipment before devices farther from the fault operate and isolate larger pieces of the system. These time overcurrent devices must also be coordinated with damage curves for equipment such as buses and cables to clear the fault before the overcurrent can cause damage to the equipment. This concept of time coordination of overcurrent is well understood, and there are general guidelines applied to account for measurement error and other inaccuracies. The reduced signal levels provided to relays due to current transformer (CT) saturation are normally not considered during coordination studies. This reduced signal level will result in slower than desired operation of protective relays. Feeder relays could trip slower than upstream devices, isolating more of the power system than intended, or could allow primary equipment to be damaged before tripping. This paper will review the concept of coordinating time overcurrent relays and then discuss the concept of loss of coordination associated with CT saturation. This paper will model CT saturation from actual installations using the IEEE Power System Relaying Committee CT Saturation Calculator tool. This model data will be used to estimate the performance of protective relays. This paper will discuss methods to improve the coordination of overcurrent relays when faced with significant CT saturation.

Wide‐area monitoring and control using the real time digital simulator and a synchrophasor vector processor

AbstractSeveral major blackouts in the past have shown the need for advanced wide‐area monitoring and control (WAMC) techniques. Advanced synchrophasor visualization and monitoring can be realized with time‐referenced power system data that are collected by phasor measurement units (PMUs) using synchronized clocks. Presently, PMUs are being deployed around the world at a rapid rate for various power system applications. When a necessary number of PMUs are installed at optimal locations throughout the network, the complete state of the system can be observed. PMUs take real‐time measurements to determine the state of the power system and can be used to enhance state estimation efficiency. With PMUs in place, there are many control and protection schemes that can be implemented successfully to take preventive and corrective actions. These remedial action schemes (RASs) are classified by the IEEE Power System Relaying Committee (PSRC) as system integrity protection schemes (SIPSs). This work involved the development of a real‐time hardware test bed in order to analyze the transient stability of a simulated power system by using synchrophasors to visualize system stress across a transmission line with and without load‐shedding schemes. The real time digital simulator (RTDS®) was used to model the power system in real time. PMUs, a satellite‐synchronized clock, and a synchrophasor vector processor (SVP) were used to test the synchrophasor application. Copyright © 2010 John Wiley & Sons, Ltd.

IEEE PSRC Report on Global Industry Experiences With System Integrity Protection Schemes (SIPS)

This paper is a summary of the IEEE Power System Relaying Committee report on the System Integrity Protection Schemes (SIPS) survey. The SIPS role is to counteract system instability, maintaining overall system connectivity, and/or to avoid serious equipment damage during major system events. The survey describes industry experiences with this category of protection schemes applied to protect the integrity of the power system. It is designed to provide guidance for SIPS users and implementers based on surveyed operating practices and lessons learned. The survey includes a global participation through the comprehensive effort of IEEE and CIGRE.

IEEE PSRC Report on Performance of Relaying During Wide-Area Stressed Conditions

This paper is a summary of the IEEE Power System Relaying Committee report. It describes the performance of protective relays during wide-area stressed power system conditions. First, the behavior of protection functions during dynamic operating conditions is described. Then, the lessons learned from studying recent wide area disturbances, as well as the operational history of protection performance during stressed system conditions, are analyzed. Finally, methods of implementing protective relay functions to prevent further propagation of system-wide disturbances are presented.

An Accurate Current Transformer Model Based on Preisach Theory for the Analysis of Electromagnetic Transients

This paper presents a new and accurate Current Transformer (CT) model for the analysis of electromagnetic transients, based on representation of core magnetization characteristics using the Preisach Theory. Unlike the existing CT models, the proposed model determines shapes of hysteresis minor loops independent of the hysteresis major loop. This results in a higher precision and more flexibility to fit the model hysteresis loops with the actual core material hysteresis loops of the CT. The proposed model has been implemented in the PSCAD/EMTDC software environment. As an application of the model, transient behavior of a CT due to a fault and its subsequent reclosure attempts is investigated and compared with the Electromagnetic Transients Program Reactor Type-96 based CT model and the IEEE Power System Relaying Committee CT model. Time-domain simulation studies show that the transient behavior of the CT is significantly different, if different hysteresis minor loop trajectories but the same hysteresis major loop are adopted. This paper concludes that both hysteresis major and minor loops must be represented to accurately simulate performance of a CT for the reported case studies.

Third Zone Revisited

Zone 3 of a step-distance protection scheme has been identified as one of the contributing causes of cascading failures in power systems. The National Electric Reliability Council (NERC) has issued rules, and the IEEE Power System Relaying Committee (PSRC) has discussed recommendations to reduce the undesirable operation of this component of the protection chain. It is the purpose of this paper to reexamine the application of zone 3, to describe situations where it can be properly utilized, where it can be removed without reducing the reliability of the system protection and, if used, how it can be modified or set. A table is presented for a variety of station designs and protection schemes including two common local backup relay systems and the associated application of a remote third zone. Finally, the concept of critical locations is introduced which can assist the relay engineer in determining if potential zone 3 undesirable operations are a serious threat to the system and help determine if the expense and difficulty of removing zone 3 or modifying the relay or its associated station is justified.

Developing IEEE 1613 standards for communications network in substations

The widespread use of multifunctional intelligent electronic devices (IEDs) with advanced communications capabilities has resulted in a new trend in substation automation systems, i.e. the implementation of high-speed peer-to-peer communications-based control schemes. The IEDs exchange messages over the substation local area network (LAN). A number of industry experts had observed that an unambiguous standard for network devices when installed in harsh environmental conditions in these substations did not exist. As a result, a task force (C2TF1) of the PES Substations Committee was formed. The task force C2TF1 adapts the four standards developed by Power System Relaying Committee (PSRC) for substation applications that do not involve protective relaying, which is now IEEE 1613 standard. They also chose to make the standard apply at the device, not system level. This paper presents the standard (IEEE 1613) developed by task force C2TF1 for communications networks in substation.

Correction to "A current-based solution for transformer differential protection-part II: relay description and evaluation"

In the above paper, a truncated and, therefore, incorrect biography of Stanley Zocholl was published. We publish the correct biography for Mr. Zocholl here. Stanley Zocholl (LF’95) received the B.S. and M.S. degrees in electrical engineering from Drexel University, Philadelphia, PA, in 1958 and 1973, respectively. He joined Schweitzer Enginering Laboratories in 1991 in the position of Distinguished Engineer. He was with ABB Power T&D Company Allentown (formerly ITE, Gould, BBC) since 1947, where he held various engineering positions, including Director of Protection Technology. He holds over a dozen patents associated with power system protection using solid state and microprocessor technology and is the author of numerous IEEE and protective relay conference papers. Mr. Zocholl is an IEEE Life Fellow and a member of the IEEE Power Engineering and Industry Applications Societies. He is also a member of the Power System Relaying Committee and past chair of the Relay Input Sources Subcommittee. His biography appears in Who’s Who in America. He received the Best Paper Award of the 1988 Petroleum and Chemical Industry Conference and the Power System Relay Committee’s Distinguished Service Award in 1991.

Parameter identification of power transformers thermal model via genetic algorithms

Abstract Recent studies by various authors have shown as the IEEE Transformer Loading Guide model and the more recent modified equations, proposed by the Working Group K3 of the IEEE ‘Power System Relaying Committee’, are lacking in accuracy in predicting the winding hottest-spot temperature of a power transformer in presence of overload conditions. This is mainly due to the deviation of the parameters of the thermal model of the power transformer in the presence of overload conditions. In the paper, a novel technique to identify the thermal parameters to be used for the estimation of the hot-spot temperature is presented. The proposed method is based on a genetic algorithm (GA) which, working on the load current and on the measured hot-spot temperature pattern, permits to identify a corrected set of parameters for the thermal model of the power transformer. Thanks to data obtained from the experimental tests, the GA based method is tested to evaluate the performance of the proposed method in terms of accuracy.

Discussion of "Mathematical models for current, voltage, and coupling capacitor voltage transformers" and closure

G. Swift comments on the paper by Working Group C-5 of the Systems Protection Subcommittee of the IEEE Power System Relaying Committee (see ibid., vol.15, no.1, 2000). The author points out an error in the article. The Working Group reply to the comments.

Adaptive Transformer Thermal Overload Protection

This paper is based on a report of the same title, prepared by Working Group K3 of the Substation Protection Subcommittee of the Power System Relaying Committee of the Power Engineering Society of the IEEE. The paper begins with background information on the causes, measurement techniques, and consequences of overheating in mineral-oil-immersed power transformers. Then techniques for adaptive transformer thermal overload protection based on the real-time solution of the transient heating equations are presented. An adaptive overcurrent protection implementation, and the related functional requirements, are discussed. The equations of Clause 7 of the 1995 IEEE Guide for Loading Mineral-Oil-Immersed Transformers are used in the analysis, with a slight modification to allow for continuously varying ambient temperature.

Adaptive transformer thermal overload protection

This paper is based on a report of the same title, prepared by Working Group K3 of the Substation Protection Subcommittee of the Power System Relaying Committee of the Power Engineering Society of the IEEE. The paper begins with background information on the causes, measurement techniques, and consequences of overheating in mineral-oil-immersed power transformers. Then techniques for adaptive transformer thermal overload protection based on the real-time solution of the transient heating equations are presented. An adaptive overcurrent protection implementation, and the related functional requirements, are discussed. The equations of Clause 7 of the 1995 IEEE Guide for Loading Mineral-Oil-Immersed Transformers are used in the analysis, with a slight modification to allow for continuously varying ambient temperature.

Neural diagnostic system for transformer thermal overload protection

Studies by various authors have shown that the IEEE Transformer Loading Guide model and the modified equations, proposed by the K3 Working Group of the IEEE Power System Relaying Committee, are lacking in accuracy in the prediction of the maximum winding hot-spot temperature of a power transformer in the presence of overload conditions. The result is a real winding hot-spot temperature greater than the predicted one. A novel technique to predict the maximum winding hot-spot temperature of a power transformer in the presence of overload conditions is presented. The proposed method is based on a radial basis function network (RBFN) which, taking in to account the load current, the top oil temperature rise over the ambient temperature and other meteorological parameters, permits recognition of the hot-spot temperature pattern. Data obtained from experimental tests allows the RBFN-based algorithm to be tested to evaluate the performance of the proposed method in terms of accuracy.

Fault and disturbance data requirements for automated computer analysis. Summary paper

This paper briefly describes the special publication, "Fault and Disturbance Data Requirements for Automated Computer Analysis", prepared by working group III of the Relaying Practices and Consumer Interface Protection Subcommittee of the IEEE Power System Relaying Committee. The publication describes the analysis objectives and the data necessary to facilitate automated analysis.

Digital Simulator Performance Requirements for Relay Testing

Working group F-8 "Digital Simulator Performance Requirements for Relay Testing" of the Relay Input Sources Subcommittee, Power System Relaying Committee, was formed in 1992 with the following assignment: "Investigate performance characteristics of digital simulators when generating electromagnetic transient program (EMTP) and digital fault recorder (DFR) based relay test waveforms. Write performance requirements specifications and prepare a paper describing the importance of the simulator performance characteristics." This paper presents the work accomplished by the working group in fulfilling its assignment.

Relay Performance Testing: a Power System Relaying Committee publication

This paper briefly describes the special publication "Relay Performance Testing" prepared by Working Group 113 of the Relaying Practices and Consumer Interface Protection Subcommittee of the IEEE Power System Relaying Committee. The salient features of the publication descriptions are included. New terms used in the publication are described for immediate reference of the readers.

Relay Performance Testing A Power System Relaying Committee Publication

This paper briefly describes the special publication Relay Performance Testing prepared by Working Group 113 of the Relaying Practices and Consumer Interface Protection Subcommittee of the IEEE Power System Relaying Committee. The salient features of the publication descriptions are included. New terms used in the publication are described for immediate reference of the readers.

Summary of "System protection and voltage stability"

This paper is a summary of "System Protection and Voltage Stability", a special publication prepared by Protection Aids to Voltage Stability Working Group of the Substation Protection Subcommittee of the IEEE Power System Relaying Committee. This summary describes the risk and mechanism of voltage collapse and suggests some operating, system upgrades, and protection solutions. Various undervoltage load shedding schemes are discussed, including actual or planned installations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A survey of optical channels for protective relaying practices and experience

The Optical Channels for Protective Relaying Working Group of the IEEE Power System Relaying Committee performed a survey of industry practices for applying optical channels, both planned and installed, for protective relaying communications. This report summarizes the sizes of the existing and planned optical fiber network, the types of construction, whether the relaying channels are on dedicated fiber or multiplexed with other services, experience, and maintenance practices. >