This paper presents a new algorithm suitable for calculating impedances from digitized voltages and currents sampled at a relay location. Each input is assumed to be composed of a decaying d.c. component and components of the fundamental and harmonic frequencies. Parameters of a digital filter determined by using the least error squares approach are then used to compute the real and imaginary components of the voltage and current phasors. Impedances as seen from a relay location are then calculated. The proposed algorithm was tested using the fault data recorded at the Regina South switching station of the Saskatchewan Power Corporation; some of the test results are included.

A New Algorithm for Digital Impedance Relays

The use of digital techniques to adapt transmission system protection and control to real-time power system changes is investigated. The discussion covers transmission system protection philosophy, transmission line protection, relay settings, transformer protection, and automatic reclosing. The tradeoff between dependability and security is examined, as well as the various conflicting criteria embodied in transmission line protection. Adaptive strategies that minimize the compromises required and thereby optimize system performance are presented. >

Adaptive transmission system relaying

This paper describes a fault direction discriminator that uses an artificial neural network (ANN) for protecting transmission lines. The discriminator uses various attributes to reach a decision and tends to emulate the conventional pattern classification problem. An equation of the boundary describing the classification is embedded in the multilayer feedforward neural network (MFNN) by training through the use of an appropriate learning algorithm and suitable training data. The discriminator uses instantaneous values of the line voltages and line currents to make decisions. Results showing the performance of the ANN-based discriminator are presented in the paper and indicate that it is fast, robust and accurate. It is suitable for realizing an ultrafast directional comparison protection of transmission lines. >

Design, implementation and testing of an artificial neural network based fault direction discriminator for protecting transmission lines

A comparative study of algorithms for digital differential protection of power transformers is reported. The mathematical basis for each algorithm is described. The algorithms are compared as to their speed of response, computational burden and capability to distinguish between an inrush and transformer internal fault. >

A state-of-the-art review of transformer protection algorithms

A recursive algorithm suitable for microprocessor-based power system relaying and measurement applications is described. The algorithm is designed using the least error squares (LES) curve fitting technique. The mathematical background for the nonrecursive least error squares algorithm is extended to form a recursive algorithm. A method for including decaying DC and harmonic frequencies in the algorithm is described. Sample studies are presented to demonstrate the performance of the developed algorithm. The recursive LES (RLES) algorithm is shown to be computationally efficient and does not require the time constant of decaying DC and statistical information concerning the signal. It is shown that a 12-RLES algorithm can be used for implementing transformer differential protection. >

A recursive least error squares algorithm for power system relaying and measurement applications

An experimental general-purpose process-control digital computer system provides high-speed phase-and ground-distance fault protection of one 230 kV transmission line. The stored program performs all of the relaying functions using the output of an analog-to- digital converter which reads the instantaneous value of the power- system currents and voltages. Model line tests described in a companion paper (II -Test Results) form the basis for preliminary performance evaluation. An automatic oscillograph and diagnostic programs will allow a study of field performance.

G. B. Gilcrest

Papers

High-Speed Distance Relaying Using a Digital Computer I - System Description