Research On Single Phase To Earth Fault Location In Distribution Network

Along with fast development of DA(distribution automation)and distributed energy,increasingly importance has been attached to single phase to earth fault location in active distribution network.DA can obtain more information from distribution network though computer,communication and other technologies,which provides new effective means for small current earth fault location;however,access of DG(distributed generator)makes the distribution network structure more complex,and it is more difficult to locate small current earth fault in distribution network with DG.After deep analysis on the characteristics of small current earth fault in distribution network with DG,fault location principles using fault signal and based on DA technologies are studied in this paper.Major research works and conclusions are as follows:1)IEEE 34 bus benchmark model is built in PSCAD/EMTDC,and its validity is proved by comparing with IEEE published data.According to distribution network in china,neutral point grounding mode is changed.Wind turbine and wound generator are added to simulation model above,and several typical fault situations are simulated and discussed.2)Zero sequence current on fault line after single phase to earth fault is studied on different conditions of DG access.It found that,in system with DG whose neutral points are not connected to earth,when single phase to earth fault occurs,on the upstream side of fault point,zero sequence current flows from fault point to substation;on the downstream side of fault point,zero sequence current flows from fault point to the end of fault line.3)In consideration of unbalanced current in distribution system,fault location based on zero sequence current increment in distribution network with DG is proposed.By using transient signal and steady signal,zero sequence current increment was adopted,and criterion parameter and direction parameter were constructed with line voltage to realize fault location.4)Fault location based on zero sequence current similarity in distribution network with DG is proposed.Based on deep analysis on zero sequence current distribution with DG,new correlation coefficient criterion based on steady zero sequence current is constructed.Polarity of correlation coefficient when fault happens is adopted as location criterion to identify fault section.Data synchronization between all FTUs are solved by data window forward/backward translation.Single phase to earth fault location methods in this paper are all hardly affected by DG,fault initial phase angle and fault resistance.And these methods needs no more primary equipment.Simulation proves that they have reliable and precise location results.