AN IMPROVED FAULT LOCATION ON POWER SYSTEM TRANSMISSION LINES USING FUZZY LOGIC APPROACH

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Abstract

The problem of Electricity are enormous and can never be treated completely until the fault department (maintenance) are improved upon for urgent and rapid response to line faults. The present protection scheme only isolates the lines in the event of faults, define the fault, but leaves no proper information about the location of the fault. Faults must occur on both the transmission and distribution lines but, the problem is how fast can the fault be cleared when the maintenance team have to patrol the lines (ie from pole to pole and from tower to tower) looking for the fault(s). in this research, fault location based fuzzy logic is developed. The proposed fuzzy logic based technique has less computation complexity. Real transmission system parameters of 400 kV Wardha – Aurangabad transmission line, India (400 km) with 40% compensation at one end are implemented for this research. Percent absolute error is calculated for performance evaluation of the proposed method. Large numbers of test cases are generated which provide complete distance protection scheme giving quite accurate results with percent absolute errors mostly within 2.75% demonstrating more accuracy as compared to previous fuzzy based fault location schemes, least complexity and robustness of the proposed technique.

CHAPTER ONE

INTRODUCTION

1.1     Background to the study

The reliable operation of large power systems with small stability margin is highly dependent on systems and protection devices. The application of microprocessor based (numeric) relaying protection has improved performance over time but, this has not led to a major impact on speed, sensitivity, and selectivity of primary protective relays. However decision making based on elements of artificial intelligence (AI) can, in my view, lead to a major impact in the aforementioned especially as quick fault removal in lines maintenance is concerned here.

Series compensation is majorly applied in modern power system for achieving maximum power utilization of existing transmission system and improving the overall performance of transmission systems. Series compensation comprises of capacitor bank protected by a metal oxide varistor (MOV) and a spark-gap arrangement. The nonlinear behavior of such series capacitors and its protection equipment during fault disturbances influences the current and voltage signals. This in turn creates problems to relay operations. Accurate detection, classification and accurate location of faults on a transmission line are crucial for relaying decision, removal of faulty sections in the system and quick repair for availability of power supply.  Peterson (2017) classified the faults correctly but lacked to give fault distance. If fault location cannot be recognized quickly then it produces prolonged line outage, rigorous economic losses may happen and reliability of service may be at big jeopardy. Looking at the mentioned protection issues faced by the existing protection schemes due to series compensation, there is a strong inspiration to develop a novel all-inclusive relaying scheme for series compensated transmission lines.

Support vector machine analysis was used as an effective method in fault identification, classification and fault section identification with distance estimation in Gururajapathy et.al,. (2016) But maximum error found in distance estimation was 30%. Also, they require a cumbersome effort for training the network to achieve a better performance under various load conditions. A bibliographical survey of effect of series compensation on transmission line protection with relevant background and various protection methodologies for series compensated line is presented in the work of Mfonyl (2014). To the best of the knowledge of the authors, no scheme has been given yet using fuzzy logic for fault phase classification and fault location in a fixed series compensated line. Majorly, fuzzy logic is used with techniques like ANN, SVM or Wavelet for fault classification purpose. There are very few schemes using fuzzy logic as a fault locator presented in Francesco (2009) for uncompensated lines and Bravo (2015) for series compensated transmission lines. Wide area measurement system, traveling wave modal etc. are also gaining popularity in transmission line protection area.

This paper implements the application of fuzzy logic for estimation of fault distance in a two bus single circuit 400 kV transmission line with FSC located at one end. All the ten types of internal shunt faults using only one terminal data, i.e. mainly capacitor voltage drop signals from relaying end have been considered as inputs to fuzzy logic system. These input signals are taken over only one cycle window from the occurrence of fault which makes this technique fast. The effects of varying internal fault type, fault location, FIA and fault resistance have been verified. The proposed technique can classify faults including single-phase to ground, two-phase and three-phase faults with high accuracy in a broad range of system post-fault loading circumstances.

This study implements the application of fuzzy logic for estimation of fault distance in a two bus single circuit 400 kV transmission line with FSC located at one end. All the ten types of internal shunt faults using only one terminal data, i.e. mainly capacitor voltage drop signals from relaying end have been considered as inputs to fuzzy logic system. These input signals are taken over only one cycle window from the occurrence of fault which makes this technique fast. The effects of varying internal fault type, fault location, FIA and fault resistance have been verified. The proposed technique can classify faults including single-phase to ground, two-phase and three-phase faults with high accuracy in a broad range of system post-fault loading circumstances.