Simulation Of Relay Protection In The Complex UHV Power Grid

1000kV ultra-high voltage(UHV) transmission is an attractive technology in whichthe demand of long-distance and large-capacity,and resource allocation optimization couldbe achieved by further development. In China,FACTS is a popular technology.Theadvantages of FASTS include transmission ability and system transient stability.As anessential content in the FACTS element, thysistor controllable series compensation (TCSC)has been applied in EHV transmission lines step by step.Although TCSC hascomprehensive advantages, it brings adverse effect to the line-protectionTo study the effects of UHV transmission line protection by TCSC,thepaper established the equivalent model of UHV transmission line.The paper alsoestablishes the transient simulation platform of the TCSC network，studies MOV highcurrent protection and further analyzes the characteristics of differential protection anddistance protection. Especially it is analyzed in detail that the influence of the UHV linedistance protection is caused by TCSC. The scope of distance protection may be narrowedwhen the impedance relay is on the side of the series compensation,and the line distanceprotection may appear the phenomenon of transient maloperation. When the distanceprotection is installed in the the side of the series compensation, it may appear the conditionof the reverse maloperation.To work out the problem of the distance protection in series compensated lines，a newdistance protection theory is proposed from a new perspective in this paper. The newmethod based on R-L differential equation algorithm. In transmission line based on π model,on the basis of calculating and reconstruct the fault point voltage, through the same lowpassfilter, using the algorithm of solution of differential equation, the iteration calculation range,we can quickly judge the fault zone on the basis of the discrete degree of fault distanceresults. The effectiveness of the new method is tested through the simulationexperiment,which overcomes the issues of protection range and misoperation in traditional.In additional, the summaries are pointed out and the direction of future research areindicated in the end of the paper.