Automated analysis of digital relay data based on expert system

Modern digital protective relays generate various flies and reports which contain abundant data regarding fault disturbances and protection system operation. This paper presents an expert system based application for automated analysis of digital relay data. In this application, forward chaining reasoning is used to predict expected protection operation while backward chaining reasoning is employed to validate and diagnosis of actual protection operation. An EMTP/C++ based digital relay model with capability of insertion of user-defined errors and generation of files and reports is developed. The analysis capability of this application is tested using the relay model.

I. Introduction

With the development of computer and communication technologies, more and more intelligent electronic devices (IEDs) such as digital protective relays (DPRs), digital fault recorders (DFRs), sequence of event recorders (SERs) and remote terminal units (RTUs) of supervisory control and data acquisition systems (SCADAs) are used in power system substations. They supply abundant data related to monitoring, control and protection of power systems. By analysis of these data, very useful information can be generated for system operators, protection engineers and maintenance staff [1]. Sophisticated software tools are required to perform the analysis so that the benefits of these data can be maximized. Since the 80's, expert systems were proposed as a promising tool for analysis of power system data. Various expert system based applications such as DFR data analysis, alarm processing, and circuit breaker monitor data analysis have been reported in the literature [2], [3], [4]. However, most of these applications can not perform detailed analysis of protection system operation because they generally utilize data from DFRs, SERs and RTUs, which only contain limited information about protection system behavior.