Fault diagnosis of 3/2 Breaker Scheme in substation based on Petri net

In substations of power system, 3/2 Breaker Scheme are used commonly. Its protective relay configuration is complex, There is a lot of information when the fault occurs, especially when the protective relays and circuit breakers fail to work, how to determine the fault element is particularly intricate. In view of features of 3/2 Breaker Scheme Fault Diagnosis, this paper put forwards a new fault diagnosis method based on fault associated tree. In this new fault diagnosis method, the fault associated tree is defined to describe the time-space properties logic according to the relay protection logic's cooperation, which is created for every possible fault primary component according breaker-primary component association. Then the action priority of protections and breakers are sorted according to their priorities and mapped to the dynamic model of the Petri net, which avoid the rings of 3/2 Breaker Scheme. The proposed model could not only estimate the fault section, but also identify the malfunctioned Protective Relays and Circuit Breakers as well as the missing and/or false alarms. The simulation results given in this paper illustrate that this fault diagnosis method can make a rapid diagnosis and give the accurate evaluation about the 3/2 Breaker Scheme faults.

I. Introduction

Usually in switchgears, when there are more then 6 lines, Power distribution unit has an important position in the system, it is advised to use the 3/2 Breaker Scheme, where each of the two components (lines, power) with 3 sets of circuit breakers are in series to connect to two buses, as shown in Fig. 1. Figure 1. Diagram of 3/2 Connection Mode