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In this paper, conventional techniques to compute the phase angle between a voltage and a current waveform are applied to assess the directionality as it is necessary in ultra high speed directional relays. It is shown that with this type of relays the main difficulty stems from the fact that in order to compute the angle, a prior knowledge of the amplitudes of the superimposed voltage and current magnitudes is necessary. Therefore very fast algorithms have to be devised that would take into account anticipated values of these magnitudes in order to assure secure trips in the shortest possible time. Keywords: digital relaying, ultra-high speed directional relays, suppression of DC offset effects, protective relays

Conventional relays based on voltage peak detection exhibit serious shortcomings with respect to capacitor banks overvoltage protection. This paper presents a harmonic simulation case study, the purpose of which is to evaluate the performance of capacitor overvoltage relays in static var compensator (SVC) installation. The paper introduces the new concept of a computer based digital relay, designed to reduce the overprotection trend found in conventional relays. The major concern is to properly evaluate the time stresses applied on the capacitor according to the NEMA (ANSI/IEEE) standard.

This paper addresses the subject of reducing outage durations and autorestoration applications within the distribution substation. Employment of intelligent electronic devices (IEDs) can aid in the reduction of the fault duration time, and also it enhances the protection, control, and monitoring at the distribution level. Further, communication among these IEDs can provide faster autorestoration, remote data analysis, event recording, etc. Many recent issues related to distribution substation protection are discussed and techniques to address these issues using current technologies are proposed. [ABSTRACT FROM AUTHOR]