POWER SYSTEM FAULT LOCATION AND IDENTIFICATION USING RELEVANCE VECTOR MACHINE

Abstract

In an electric power system there always exists a possibility of disturbance and fault. In order to maintain the stability of the system, faults on transmission lines need to be detected, classified, located accurately and cleared as fast as possible. Faults occurring on a transmission line can be classified into symmetrical and unsymmetrical faults. A symmetrical fault is a balanced fault with the sinusoidal waves being equal about their axes, and represents a steady state condition. An unsymmetrical fault displays a d.c. offset, transient in nature and decaying to the steady state of the symmetrical fault after a period of time. In transmission line faults, roughly 5% are symmetric and rest are unsymmetrical in nature. Common types of asymmetric faults and their causes • Line-to-line fault(LL)- a short circuit between lines, caused by ionization of air, or when lines come into physical contact, for example due to a broken insulator. • Line-to-ground fault(LG)- a short circuit between one line and ground, very often caused by physical contact, for example due to lightning or other storm damage. • Double line-to-ground fault (LLG)- two lines come into contact with the ground (and each other), also commonly due to storm damage. In the normal operating conditions, the system is in balanced condition and hence can be represented as an equivalent single phase system. However, a fault can cause the system to become unbalanced. LG, LL, and LLG faults cause the system to become unsymmetrical. The single-phase equivalent system method of analysis cannot be applied to such unsymmetrical systems. The method of symmetrical components uses a transformation to convert phase components into symmetrical components. This transformation represents an unbalanced three-phase system by a set of three balanced three-phase systems.