DISTANCE PROTECTION SCHEME WITH SSSC

Abstract

During the last decade, a number of control devices called "Flexible AC Transmission Systems" (FACTS) technology have been proposed and implemented. FACTS devices can be used for power flow control, voltage regulation, enhancement of transient stability and damping of power oscillations. FACTS devices can be used as a series controller, shunt controllers or as a combination of both. With the introduction of high power GTO (Gate Turn-off Thyristor), IGBT (Insulated Gate Bipolar Transistor), etc. the VSI (Voltage Source Inverter) has been implemented using these switching devices. These generate or absorb reactive power without using AC capacitor or reactor banks. SSSC (Static Synchronous Series Compensator) is based on VSI. As SSSC has fast response and its functional characteristics and control system introduce dynamic changes during fault conditions in a transmission line it is important that distance relays perform correctly irrespective of such dynamic changes introduced during fault. This demands for correct classification of fault as fast as possible. There are many ways with which the type of fault and its location can be identified. Out of the methods used for classification of fault the most widely used methods are: • ANN (Artificial Neural Network)-based approach. • Expert system based approach. • Fuzzy and fuzzy neural network based approach. • Statistical approach for fault zone identification. This report mainly focuses on fault zone identification using statistical approach, fault classification using automated fuzzy logic approach and finally first zone protection using traditional approach. The performance of the algorithms developed in this thesis has been carried out on the same sample power system. The proposed methodologies has been tested on 300 km, 400 kV SSSC compensated transmission line, SSSC being placed at the midpoint. Various system parameters have been varied to generate almost 40,000 test cases excluding the training case.