Research On Full Capacitance Restrain Method And Experiment For Distribution Transformer Zero Sequence And Negative Sequence Current

With the rapid development of national economy and production technology, thepower system has become diversified and complicated, the distribution transformersoperation is generally unbalance caused by a large number of unbalanced loads. Basedon static reactive power compensation technology, this paper presented an fullcapacitance compensation method for zero sequence and negative sequence current bymultistep optimization and reactive power compensation, and developed a dynamicgovernance experimental device to restrain zero sequence and negative sequence current,improve power factor and reduce distribution transformer loss for the safety andstability of distribution transformer operation. In this paper, the main research is shownas follows:1) Based on the basic principle and normal method for zero sequence and negativesequence current restrain, this paper considered the harm of inductance andovercompensation, explored the effect of zero sequence and negative sequence current,power factor and loss caused by the reactive power compensation, presented a fullcapacitance restrain method for zero sequence and negative sequence current, built asimulation model of distribution transformer to verify the method’s feasibility.2) Based on full capacitance restrain method for zero sequence and negativesequence current, considering live environment, this paper developed a dynamicgovernance experimental device which can gather and display power quality data,calculate the capacity of reactive power compensation, controll the capacitorcompensation automatically, accomplish wireless data-transmission and so on, to reducethe harm of zero sequence and negative sequence current.3) Based on MpLab, this paper introduced the programme of compensatiioncontrol unit, including data extraction and judging subprogram, zero sequence andnegative sequence current restrain algorithm subprogram, GPRS communicationsubprogram. Based on VC++2010and MySQL5.0, this paper introduced a software tomonitor distribution transformer and reactive power compensation equipment online,which has a favorable operation interface for ease of operation4) The result of laboratory experiment proved the effectiveness of the method andthe reliability of the device. The result of field experiment proved the experimentaldevice can calculate capacitance compensation based on real-time loads, control theswitching of capacitor automatically, to restrain zero sequence and negative sequence current, increase power factor, for reducing the loss and solve the harm caused by zerosequence and negative sequence current.