Development and Research of Fault Location Algorithm for Double-End Feed Lines in the Multifunctional System

Overhead power transmission lines are the most damageable elements of the electric power system (EPS) [1] -[3]. An overhead power transmission line fault leads to interruption of power supply, lower quality and increased loss of electrical energy. To restore the normal operation of the EPS, reduce damage and costs, it is necessary to quickly and accurately locate the fault in overhead lines.The remote fault location (RFL) for overhead lines is an inherent function of modern substation automation systems. There are wide-spreading methods of fault location based on measurement of the emergency mode parameters (EMP) [4]. Power line currents and voltages obtained from primary converters are used as input information in the fault location methods based on EMP.These RFL methods and devices including the methods based on EMP can be subdivided into one-sided and two-sided measurement methods. The latter use the information from both sides of power lines and also use a special communication channel between the subsets of the devices for synchronized or asynchronized data exchange [2], [4], [5]. Double-end feed lines must be equipped with RFL devices based on two-sided measurement [4] These methods have smaller error in comparison with one-sided measurement methods and measurement distortion factors (e.g. value of transient resistance in fault location) affect them to a lesser extent.The advantages of RFL methods based on EMP including two-sided measurement methods (for instance, compared to pulse fault location methods) are simplicity of usage, absence of generating equipment, possibility of usage in every configuration of power lines [6-8]. At the same time the RFL methods based on measuring EMP, have large (about 10-20%) error caused primarily by error of measuring units (current and voltage sensors) [1], [9]Traditional electromagnetic sensors (current (CT) and voltage transformers (VT)) have limited frequency range and error caused by core saturation. Errors of CT and VT, especially in transient modes, can lead to large errors in measuring of the EMP, and cause failure or false operation of relay protection and automatic equipment.Improving of the accuracy of RFL methods has become possible with the invention of fundamentally new innovative converters: digital current and voltage transformers (DCT and DVT). Usage of digital current and voltage converters can significantly improve the accuracy of RFL due to their advantages [10] -[15]: high measurement accuracy (error of not more than 0.1% in current and voltage); wide frequency range of measurements, including direct current measurement; lack of saturation from short-circuit currents and an aperiodic component. A multi-functional system (MFS) based on digital measuring transformers [15] is under development at ISPU, comprising, among other things, new algorithms of relay protection, automation and fault location (FL) that fully implement the advantages of innovative converters.This article is devoted to the development and study of the RFL algorithm based on synchronized two-sided measurement of electrical quantities of emergency modes as part of the multi-functional system (MFS) based on DCT and DVT.