Combination of the Methods of symmetrical components and Double Entry to Increase the Reliability of Digital Differential Relay Protection

Aleksandr L Kulikov,Boris V Papkov,Anton A Kolesnikov,Vladimir Ju Vukolov,N Voropai,R Lis,G Chang,A Kler,F.-J Lin

doi:10.1051/e3sconf/20186902016

Abstract

The method of symmetrical components is one of the main methods used to calculate asymmetric modes in electric power systems. To increase the reliability of digital differential relay protection in case of asymmetric faults, a combination of symmetric components and double entry methods is proposed. It is supposed to compile balance equations, to apply the theory of graphs and matrices, and the estimation of reliability indicators is carried out on the basis of the method of Markov chains. The obtained results allow to make a conclusion about the prospects of implementing a differential protection using the method of double entry and symmetrical components in the electrical networks.

Highlights

The method of symmetrical components is a main transformation that is applied in relay protection (RP) to determine ground faults and detect asymmetry [1]
Since each arc of the graph is reflected with the same weight in the matrices twice: as an arc, associated with the vertex directed to one matrix, and as the arc associated with the vertex directed from another matrix, in the case getting wrong values is the sum of incoming and outgoing currents in the two matrices becomes incorrect, but the total differential current of the whole network remains equal to zero
From the results of the calculation it follows that there is an increase reliability of the relay protection using the proposed method of organization of protection, absence of fault on the protected object: up to 1.5 times in the function of unreadiness and up to 4.5 times in the probability of failure-free operation; in case fault on the protected object mode up to 10.4 times in the function of unreadiness and up to 1.5 times in the probability of failure-free operation

Summary

Introduction

The method of symmetrical components is a main transformation that is applied in relay protection (RP) to determine ground faults and detect asymmetry [1]. One of its features is the universality and the ability to implement in decentralized and centralized protection, for example, in the centralized protection against ground faults [2]. As a development of the centralized modification of using the method of symmetric components, it is proposed to develop a differential current protection with the implementation of the methods of symmetric components and double entry to increase the reliability of electrical networks [3]. For all graph vertices with degree >1 compile equations in matrix form for the sum of the currents different sequences (positive, negative, zero) at the nodes. Mathematical calculations for the proposed approach are detailed in [3, 4]

Realization of proposed protection

Quantitative assessment of the reliability of the proposed protection

Mode 1: absence of fault on the protected object

Conclusions