Series Compensated Line Pilot Protection Scheme Using Wavelet Transformation

Series capacitor compensation technology has been widely used in power systems due to its many kinds of functions such as increased transmission capability, enhanced the voltage and transient stability, regulating power flow flexibly, restraining low-frequency system oscillation and sub-synchronous resonance, etc. However, some phenomena such as voltage and/or current inversion, lower-fredquency transient components and sub-harmonic oscillations are issues related with series capacitors installation on transmission lines, thus have a serious impact on existing relay protection of transmission line.This thesis investigates the characteristic of series capacitor compensation equipment, analyses the associated voltage and current inversion phenomena, and their impact on traditional relay protection of transmission lines such as directional protection relaying, pilot protection schemes such as distance and line differential protection. An algorithm using power frequency fault components due to series capacitor compensation is discussed.A new approach for series compensated transmission line based on wavelet transformation is presented in the thesis. A 500kV GuangXi power system simulation model including fixed series capacitor (FSC) and thrister controlled series capacitor (TCSC) is constructed using the Real-Time Digital Simulator (RTDS). Various fault types presented in and out the protected line located before or after the vapacitor are simulated. Faulty current signals at the realying points on both sides of the series capacitor (SC) compensated line are discomposed based on wavelet transformation. The sign of wavelet transformation modulus maxima product is used to discriminate between internal faults and external faults. This new approach is proved to be fast , reliable, and simple, and what's more, it is not affected by TCSC dynamic characteristic.IEC 61850 is a global standard foster interoperability between devices and systems from different vendors, is the latest international standard about seamless communication networks and systems in substations published by International Electrotechnical Commission technical committees 57(IEC TC57). This thesis also studies the feasibility of using IEC 61850 for information exchange between relays located at both ends of the line, and discusses the communication mode of transmission line pilot protection using IEC 61850 technology.