Research Of New Protection Of Transformer Based On Correlation Coefficients Of Sampled Current Values And The Excitation Inductance

Transformer is one of major electric apparatuses in power system. It plays an importantrole in the transmission of power supply. Therefore, the research for new algorithm oftransformer protection with high performance, such as fast, reliable and sensible capabilities,isinhighlydemand.In this dissertation, the morphological filter is utilized as the filtering unit of thetransformerdifferential protection.Thecharacteristicsofthefaultsignalcanbepreserved andthe noise interferences are suppressed. Based on this, the dissertation presents a newtransformerdifferential protectioncriteriontodistinguish internal faults andexternal faults bycorrelation coefficients of sampled current values. Based on the previous research,thedissertation makes a deep analysis on the calculation of the equivalent instantaneousinductance of wye-delta connected transformer,A new algorithm of calculating theequivalent instantaneous inductance by virtual voltage and transformer protection differentialis creatively put forward, and besides, an new algorithm based on the difference of theequivalent instantaneous inductance between inrush currents and internal fault for thediscriminationbetweeninrushandfaultcurrentisproposed.In order to analyse and validate the protection,The hardware of relaydevice which cantestnewrelaytheoryisdevelopedbasedontheClanguage.