Real-Time Monitoring And Assessment Of Circuit Breaker Operations

Abstract

Circuit breakers (CBs) are very important elements in the power system. They are used to switch other equipment in and out of service. Circuit breakers need to be reliable since their incorrect operation can cause major issues with power system protection and control.

Today’s practice in monitoring circuit breaker operation and status in real time is reduced to the use of Remote Terminal Units (RTUs) of Supervisory Control and Data Acquisition (SCADA) system to assess CB status. More detailed information about the control circuit performance may be obtained by CB test equipment typically used for maintenance diagnostics.

This paper addresses two important issues:

1. How improved CB monitoring may be implemented in real-time, and
2. What would be the benefits of such an implementation.

The paper is devoted to description of a prototype implementation of a real-time CB monitoring system.

The system consists of a new CB monitoring data acquisition IED that is located at circuit breaker and captures detailed information about its operation in real-time. The CB files are transferred to the concentrator PC where the application software performs automated analysis and makes an assessment about the operational status of the breaker.

The software is based on signal processing and expert system processing. Application example using actual field data is discussed.

Introduction

System wide real-time monitoring of circuit breaker operation and statuses currently is implemented using Remote Terminal Units (RTUs) of Supervisory Control and Data Acquisition (SCADA) system.

Based on detected voltage levels on circuit breaker contacts, these units are providing information on final statuses of the circuit breakers such as “OPEN” or “CLOSE”. The transitions in time of control signals, such as Trip or Close Initiate, X and Y coil currents, Control and Yard DC voltages, Closing Coil and others, used by protection and maintenance engineers for evaluation of CB performance cannot be monitored using RTU and SCADA approach.

The system for real-time monitoring and analysis of circuit breaker operations described in this paper is an extension of widely used portable circuit breaker testing device concept [2]. The traditional testing devices are temporally connected to the circuit breaker’s control circuit to record analog and digital signals.

The operator opens and closes the circuit breaker each time the test is performed and data are recorded. The traditional analysis is done manually by overlaying traces from a “good” case recorded earlier and making a judgment of how different the new case is.

The paper ends with some conclusions, acknowledgments and a list of references.