Research On The New Principle Of Single-pole Adaptive Reclosure

Operation experiences of power system shows that the faults occurred onoverhead lines are mostly transient. So automatic reclosure is widely used intransmission lines as one of the important methods for improving secure and reliableoperation of power system. But conventional autoreclosure's shortcoming is that itacts blindly entirely before reclosing and can't distinguish transient fault frompermanent fault. It will cause serious damage to power system. If fault could bejudged advanced before the operation of reclosure, That is to say, the reclosure couldoperation adaptively according to the characteristic of the fault, power system couldkeep working stable because of the avoidance of reclosing on permanent fault and thesubsequent impact on system.Firstly, the paper analyses the voltage algorithm of single-pole adaptive reclosure,and presents its theory, applying range and disadvantages. Then an new approachbased on the voltage at fault point to distinguish between transient and permanentfault in single pole reclosure is brought forward. Using electric data from both side oftransmission line and fault location, fault point voltage can obtained and comparedwith setting value. Because the magnitude of it is far big when transient fault happensthan that when permanent fault happens, this approach is able to work exactly andwon't be affected by transition resistance and length of the line.Compensation for capacitance along the transmission line by Shunt reactorswhich is used universally on EHV and UHV would have some effect on the operationof reclosure, so the rule of how to select the value of shunt reactors and neutralgrounding reactor, which exert an influence on recovery voltage, is introduced. Thereis a decaying periodic component besides the power frequency voltage and thenestification of them is beating wave, when single-pole transient fault happens ontransmission line with shunt reactors. The components of recovery voltage areanalyzed by complex frequency-domain analysis and emulate by PSCAD. A criterionfor distinguishing between transient and permanent fault is presented by measuringthe decaying periodic component of recovery voltage. A new algorithm is developedfor getting the magnitude of decaying periodic component of recovery voltage.