Analysis and identification of HVDS system faults using wavelet transforms

Abstract

Reliability and quality of power are some of the important tasks for a power system engineer. Transmission of electrical power through High Voltage Direct Current (HVDC) is becoming an established technology. Rapid advances are taking place in the field of HVDC transmission due to the fact that it possesses numerous advantages when compared to HVAC or EHVAC transmission. HVDC transmission has definite economic benefits when large blocks of power are to be transmitted over long distances. The satisfactory performance of the HVDC system is one of the necessary conditions to obtain uninterrupted power supply. However few faults in the HVDC system such as faults on the transmission line, faults in the converter transformer, faults on the ac side of inverter and rectifier may lead to the failure of the HVDC system. Thus, to ensure greater reliability the detection and fast clearance of faults in HVDC lines are indispensable. The major faults associated with HVDC transmission system are dc line to ground fault, faults on the ac side of the inverter, commutation failure at the inverter. The protection principle based on travelling wave theory provides the fastest protection. Long HVDC lines can be modeled using distributed elements. According to Travelling Wave Theory, when the fault occurs on the transmission line the voltage and current newlineii newlinetravelling waves appear on the line. The travelling waves generated will carry information related to the condition of the transmission system. In this work, the analysis and identification of HVDC system faults, different cases are studied. A standard model of 12-pulse HVDC system under the MATLAB environment is used for the simulation. The simulation model in which a 1000MW (500kV, 2kA) DC line is proposed to transmit power over a DC line of 300km from a 500kV, 5000MVA, 60Hz network to a 345kV, 10000MVA, 50Hz network. One of the major components in the HVDC system is the convertor transformer.