Computation of Transients in EHV Systems (with Reference to High Speed Protective Systems)

Abstract

EHV systems, being characterised by high degree of interconnections, increased fault levels and large X/R ratios, insist on fast clearance of faults with high discriminating ability. When studying the shortest times in which reliable protection measurements have to be made, it is necessary to take into account the interaction between the primary system transients transmitted by transducers, the transients induced by these transducers themselves and their effects on the decision processes of the protection schemes. Digital computer simulation can give a degree of representation that goes well beyond that feasible with laboratory analogue modelling. The purpose of the present paper is to present the results of analysis of fault transients, current and potential transducer transients and inrush currents in power transformers for a typical 400 kV system,using direct integration technique based on Dommel’s method. The computed dynamic performances of a mho and a quadrilateral type distance relays are also presented.