Research On Fault Feeder Selection For Single-phase Grounding Fault In Distribution Grid Based On CSVD Algorithm

In Chinese distribution network,neutral non-effective grounding type is widely used,including neutral indirectly grounding type and arc suppression coil grounding type,which is also called small current grounded system.There is a high possibility to have single-phase ground fault in distribution work,through big data statistics,these fault type accounts for⁸0%of total failure in distribution network.When single-phase ground fault occurs in three phase line system,since there is no loop formed between ground and transmission line,the fault current is relatively low,meanwhile the line voltages between the three-phase remains symmetric,the new rules provide the continued work time can be8 hours.Nevertheless,due to the voltage in non-fault phase relative to ground arises³times compared to the one in normal phase condition,this is very harmful for system security,long time operation in this fault condition can make the failure extend,resulting in line trip and power failure.Therefore,a rapid and reliable detection of the fault line become an important issue in distribution network for safe operation.Because of the fault situation in distribution network are very common,when the value of transition resistance and the type of neutral grounding are different,after fault detection the steady-state component is also quite different,which make the line selection method based on characteristics of steady-state components not very reliable.While the information of transient-state component are rather considerable,its amplitude is several times higher than the one in steady-state signal,which make it has a great advantage in line selection foundation.This paper based on phase mode transformation theory,through using of Karrenbauer matrix,and the phase domain system is transformed to amplitude domain without electromagnetic coupling system,based on the boundary conditions of single-phase ground fault,the independent 1^st order mode,2^nd order mode and 0 order mode are combined,the corresponding multiple compound mode contains transient-state component can be obtained for fault analysis,its simplified 0 order mode equivalent circuit can be used to get time domain expression of transient signal,which can be identify fault line fast and effectively.The analysis of transient component characteristics of single-phase ground fault in small current grounded system provide a theoretical foundation to research new fault line selection method.This paper using PSCAD software to simulate single-phase ground fault situation in distribution network,while analyzing transient state process,CSVD algorithm is used as criterion,the effect of noise and harmonic wave in circuit is eliminated,and the characteristic signal of transient-state zero order mode current which suitable for fault line selection is obtained;Through CSVD algorithm to transformation analysis of zero order mode transient-state current signal,the difference of transient signal corresponding to fault phase and non-fault phase is obtained,the similarity criterion of reconfiguration waveform and criterion based on traveling wave front polarity is proposed;Finally,through simulation single-phase ground fault under multiple condition,the zero order mode transient-state current signal is transformed and the characteristics is extracted through CSVD algorithm,using the proposed two fault line selection criterion the fault line is fast and accurate determined,which verified the correction of fault line selection method in this article.