??????????? ????? 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

A fundamental basis has been developed for the use of a time-shared stored-program digital computer to perform many of the electrical power-system protective-relay functions in a substation. Logic operations are given to detect a fault, locate it, and initiate the opening of the appropriate circuit breakers, whether the fault is in the station or on lines radiating from the station.

https://digitalcommons.njit.edu/cgi/viewcontent.cgi?article=2601&context=theses

Fault Protection with a Digital Computer

The principles of system protection and the proper selection, application, and coordination of components that may be required to protect industrial and commercial power systems against abnormalities that could reasonably be expected to occur in the course of system operation are presented in a in a simple, yet comprehensive, format. The principles presented apply to both new electrical system design and to the changing, upgrading, or expansion of an existing electrical distribution system.

IEEE Recommended Practice for Protection and Co-ordination of Industrial and Commercial Power Systems

This paper analyzes the problem of transformer differential protection. First, we review the concept of transformer differential protection. We then analyze magnetizing inrush, overexcitation, and current transformer (CT) saturation phenomena as possible causes of relay misoperation. Finally, we summarize the existing methods for discriminating internal faults from inrush and overexcitation conditions. In Part II of the paper we propose a new approach for transformer differential protection and describe the relay that is based on this approach.

A Current-Based Solution for Transformer Differential Protection. Part I: Problem Statement

A Transformer Differential Relay with Second-Harmonic Restraint

Up to the present time, the only data generally available to protection engineers for determining the performance of current transformers have been the ratio and phase-angle curves of the current transformers in question. More detailed analysis sis of important high-speed differential protection problems has shown that these data are hopelessly inadequate for the purpose of determining the performance of current transformers during the starting period when the current wave may be fully offset. If the time constant for decay of the d-c component exceeds 0.05 second, large errors of transformation may be expected if standard current transformers are used. While it is possible to make special designs that will not saturate because of the d-c component in the current,1 such designs are usually considerably oversize and expensive. Furthermore, space requirements and economy sometimes dictate that current transformers already installed be used if at all possible, even though it is known that their performance will be far from perfect. The problem then becomes one of determining the actual performance of existing current transformers, so that a suitable relay scheme may be chosen. It is the purpose of this paper to discuss the solution of this problem, and to present approximate methods of calculation not hitherto available. Attention is also given to the proper interpretation of the calculations with respect to relay operations, together with supporting test results.

Current Transformers and Relays for High-Speed Differential Protection, With Particular Reference to Offset Transient Currents

A scheme of bus protection offering advantages in simplicity, speed, and size uses linear couplers (air-core mutual reactances) in place of current transformers. This solves the troublesome problem of saturation and provides a linear relationship between secondary voltage and primary current. The coupler secondaries for a given bus are connected in a series loop with the relay. When the currents entering and leaving the bus are equal, the net induced voltage in the relay loop is zero. For a fault on the bus, however, the net induced voltage, proportional to the fault current, operates the relay. The problems are: 1. To utilize effectively the smaller available energy. 2. To build couplers of sufficiently equal mutual reactance and unaffected by stray fields. A toroidal coil solved the latter problem. Through tests have shown that the performance is strictly linear with respect to primary currnet, practically unaffected by the primary d-c transient, and thus can be calculated accurately and simply.

Linear Couplers for Bus Protection

A Study of Directional Element Connections for Phase Relays

THE PROBLEM of bus differential protection is receiving increased attention by relay engineers because of the serious consequences of a bus fault. Several cases of bus faults have recently occurred indicating that regardless of care used in the design of structures, some unexpected failure or accident may cause a disastrous outage. In spite of the many improvements that have been made in the protection of transmission lines in recent years, little attention has been given to the protection of station busses. This has been due partly to the impression that they were not particularly subject to faults and partly to the feeling that the protective relays would do more harm than good through incorrect tripping. Recent experiences, however, indicate that a bus fault, though of infrequent occurrence, can cause much greater damage and a longer outage period than many transmission line faults. Also, high-grade performance has been obtained when a bus protective scheme is properly installed with due consideration given to the many factors which might lead to faulty operation. The purpose of this paper is to discuss some of the important factors to be considered in bus differential protection and the operating characteristics and results of a field test on a new bus differential relay.

Considerations in Applying Ratio Differential Relays for Bus Protection

In the application of differential relays the need for a supervising relay which will detect the existence of a single-phase-to-ground fault condition to the exclusion of all others has frequently arisen. Heretofore, the only scheme available has been to utilize a relay energized by zero-sequence quantities. Generally, the relay has been energized by a current transformer connected in the station ground. Such a relay, however, will also detect the existence of a two-phase-to-ground fault and only partially solves the problem. The new relay described in this paper derives its operating force from the zero-sequence voltage at the bus and is restrained by the negative-sequence voltage at the bus. The addition of properly proportioned negative-sequence restraint provides the relay with a means of recognizing a single-phase-to-ground fault only. It is applicable on those systems where the zero-sequence impedance of the system exceeds the negative-sequence impedance by a reasonable margin.

W. K. Sonnemann

Papers

Current Transformers and Relays for High-Speed Differential Protection, With Particular Reference to Offset Transient Currents

Linear Couplers for Bus Protection

A Study of Directional Element Connections for Phase Relays

Considerations in Applying Ratio Differential Relays for Bus Protection

A New Single-Phase-to-Ground Fault-Detecting Relay