With the advent of Substation Computer Systems dedicated to protection, control and data logging functions in a Substation, it becomes possible to develop new applications which can utilize the processing power available within the substation. The microcomputer based Symmetrical Component Distance Relay (SCDR) described in the references cited at the end of this paper possesses certain characteristics which facilitate real-time monitoring of positive sequence voltage phasor at the local power system bus. With a regression analysis the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle. This paper describes the theoretical basis of these computations and describes results of experiments performed in the AEP power system simulation laboratory. Plans for future field tests on the AEP system are also outlined.

A New Measurement Technique for Tracking Voltage Phasors, Local System Frequency, and Rate of Change of Frequency

This text/reference presents a comprehensive, up-to-date account of computer relaying in power systems, based in part on the author's extensive experience in the field. Provides background material on current relaying practices, and covers the mathematical foundations for relaying algorithms. Each chapter contains helpful illustrations, examples, and problems.

Computer Relaying for Power Systems

??????????? ????? Stanley Horowitz H Power System Relaying May 13th, 2020 With emphasis on power system protection from the network operator perspective this classic textbook explains the fundamentals of relaying and power system phenomena including stability protection and reliability The fourth edition brings coverage up to date with important advancements in protective relaying due to significant changes in the conventional electric power system that will

Power System Relaying

The recent introduction of microprocessors into substations for protection and control makes it possible to measure positive sequence voltage phasors and positive sequence transmission line current phasors in real time. It is necessary to synchronize sampling clocks in various substations in order to put the phasors on a common reference. Techniques for synchronizing sampling along with a method for obtaining positive sequence phasors from samples are reviewed. Although it is possible to use these direct measurements in conventional state estimation algorithms, considerable advantage accrues if the state estimation is reformulated in terms of direct measurements of phasor voltages and currents. The resulting estimation algorithm involves an admittance like matrix with the sparsity of the admittance matrix. The new matrix is real rather than complex even for small X/R ratios for the lines. The algorithm requires no assumptions as to decoupling, flat voltage profiles, small resistance, etc. The algorithm converges in one step with the same amount of computation as one iteration of existing estimators. Examples are given for the IEEE 118 bus system.

State Estimlatjon with Phasor Measurements

Synchronized phasor measurements (PMU) were introduced in mid-1980s. Since then, the subject of wide-area measurements in power systems using PMUs and other measuring instruments has been receiving considerable attention from researchers in the field. This paper provides a historical overview of the PMU development. It is pointed out that the PMU is a direct descendant of the symmetrical component distance relay introduced in the late 1970s. From the early prototypes of the PMU built at Virginia Tech, a commercial product evolved which has been installed in the field at various locations around the world. Applications of PMU measurements to power system operation and control remains a very important subject for current research.

Synchronized phasor measurements-a historical overview

The paper derives the performance equation of a high speed distance relay which is based upon the theory of symmetrical components. A single equation is shown to be adequate for handling all types of faults which are likely to occur on a three-phase power system. Errors created by system loading and fault-path resistance are considered. A numerical example illustrates the principle of operation of the relay. The relay is especially suited to a digital computer based protection system.

Fundamental basis for distance relaying with symmetrical components

This paper describes the research and development work being done at the AEP Service Corp. on digital computer applications in EHV substations. Relaying of transmission lines and other power system equipment, station alarm monitoring and data logging, oscillography, and supervisory control functions are considered for possible computer implementation. A new algorithm for computing the impedance as seen from the terminals of a faulted transmission line is presented. Results obtained with the new algorithm for faults simulated with a model transmission line are included in the paper. Field experience obtained from operating a minicomputer in an EHV substation is also described.

A digital computer system for EHV substations: Analysis and field tests

This paper summarizes the newly developed concept of a Symmetrical Component Distance Relay (SCDR). Digital computer implementation of the SCDR and a micro computer based hardware system suitable for this task is described. Salient features of the relay algorithm are given, and laboratory tests of the SCDR program described. Field testing of the micro- computer based SCER is planned for the Spring of 1979.

A Microcomputer Based Symmetrical Component Distance Relay

This paper describes the field tests of a microcomputer based Symmetrical Component Distance Relay (SCDR). A brief review of the relay operating principle is followed by a description of the field tests conducted by staging faults on a 765 kV transmission line on the AEP system. Performance of SCDR during these tests is analyzed. A newly developed Ultra-High-Speed (UHS) mode of operation for the SCDR is presented, and the performance of the relay in the Ultra-High-Speed mode is illustrated with the data gathered during the field tests.

M. Ibrahim

Papers

Fundamental basis for distance relaying with symmetrical components

A digital computer system for EHV substations: Analysis and field tests

A Microcomputer Based Symmetrical Component Distance Relay

A Microcomputer Based Ultra-High Speed Distance Relay: Field Tests