A Study of the Measurement Section of Digital Relay Protection Units

Abstract

The problem of the electric power systems (EPS) relay protection (RP) units’ adjustment, which does not correspond to the real operation conditions, was considered. It was found that the availability of the integral analysis of the key elements of different design RP units under the particular operation conditions is the basic condition for the problem solving, which is provided by the application of adequate RP mathematical models and modern EPS motivating factors. The existing EPS and RP modeling methods and tools were analyzed. On the basis of the RP detailed modeling concept, developed by the authors, the mathematical models of the complete diagram of the measurement sections of the digital differential transformer protection were developed for different types of intermediate transformers and low frequency filters. The comparative numerical analysis of their influence on the primary input signal was performed, including the analysis with consideration of nonlinearity of the measuring current transformer excitation characteristic. The theoretical and practical studies, presented in the paper, permit to define the requirements imposed on RP mathematical models, which will be used in the further studies aimed at developing a method for RP adequate adjustment.