Fast fault section estimation in distribution substations using matrix-based cause-effect networks

A new method for estimating fault sections in power substations is proposed. In this paper the knowledge representation and inference procedures based on the cause-effect networks (CE-Nets) and rule matrix transformation techniques are presented. The matrix based inference procedures are proposed to estimate the possible fault sections through simple matrix operations by transforming the established CE-Nets into matrix forms. The method is superior to existing production systems in the inference speed and the process of implementation. By testing on a typical Taiwan Power Company's (Taipower) secondary substation, the experimental results show that the effectiveness of the proposed method even for the fault domains involving multiple faults and failure operations of protective devices. Moreover, it is easy to implement and transplant into different substations.

I. Introduction

With recent advances in computer and communication technologies, the computer-based Supervisory Control And Data Acquisition (SCADA) systems are increasingly used in the modern electric utility field. The ultimate goal for a power system is to supply a reliable and stable power to the customs. However, it is inevitable that disturbances such as lightning strokes, collisions and equipment failures will occur. In case of a fault does occur, it is imperative to restrict the impact of outages to the minimum and to restore the faulted facilities as quickly as possible. This requires the location and nature of the fault first be identified, which is the main issue of fault diagnosis in power systems. Taiwan Power Company (TPC) has implemented a Hierarchical Dispatch and Control System (HDCS) to meet the requirements of Taiwan's highly industrialized society in a better quality and higher reliability fashion. The HDCS is a three-level control system, which comprises a CDCS (Central Dispatch and Control System), six ADCSs (Area Dispatch and Control System) and nineteen DDCSs (Distribution Dispatch and Control System). In a DDCS control center, on average, the operator is responsible for more than fifteen unmanned secondary substations simultaneously. In normal operating conditions, operators can properly deal with various situations. Once faults appear, the operators may find it difficult to analyze the faults and take appropriate actions in the overwhelming alarm messages. This task become increasingly complex if multiple faults have occurred or some pieces of equipment have malfunctioned. Our research was motivated by the result of discussing with the operators in Keelung DDCS located in northern Taiwan. An opinion was expressed that a fault diagnosis tool ought to be developed as an operator's aid function in control center.