Research On Detection Of Phase-to-phase Fault Failures In Smart Distribution Grid

Most of the existing fault power failures are caused by faults in the distribution network,so the fault handling technology of the distribution network is of great significance to improve the reliability of power supply.The development of Chinese power system is affected by the concept "think highly of generating side,look down on distribution side",and the protection scheme of the distribution network only emphasizes the security of the power grid itself and simplifies its protection configuration.Therefore,in the case of phase-to-phase faults in a conventional distribution network,the reclosure with a fixed time-limited is generally adopted,however it blindness may lead to an unsuccessful reclosing.Thus,it is necessary to study the fault-free identification before the reclosing of the power distribution network phase-to-phase fault,which is helpful to improve the fault self-healing ability of the distribution network under the smart grid.In this dissertation,a long line with shunt capacitors for distribution network is analyzed.The influence of the configuration of the shunt capacitor of the distribution network on the electrical characteristics obtained after tripping of the phase-to-phase fault breaker and the difference and vary of laws of the voltage/current amplitude characteristics of the shunt capacitor bank after the breaker trips in two types of phase-to-phase faults of the distribution network,that is,when the line has a transient fault between phases,the current decay rate of the shunt capacitance compensator is slow,and before the arc extinction,the arc loop resistance is small,after the arc extinction,the fault arc loop disappears,its equivalent resistance is theoretically infinite,and there is a sudden change in equivalent resistance of the arc loop before and after the arc extinguishing,while for a permanent fault,the current of the shunt capacitance compensator attenuates rapidly and greater the fault resistance,be the faster the attenuation,be the transition resistance of the fault loop after the trip continues to be a small value.Based on this,this dissertation studies the electrical characteristics of the shunt capacitor after the circuit breaker is tripped and proposes the method and criterion for identifying the two phase-to-phase fault properties using the current amplitude attenuation characteristics of the shunt compensation capacitor and the arc loop resistance characteristics.Using PSCAD/EMTDC and MATLAB softwares modeling,it analyzes that there is an electrical signal that can be used effectively for 200-300 ms after tripping for a line with shunt compensation capacitor bank.The results show that the theoretical analysis of this paper is correct and the method can use the electrical characteristics of the shunt capacitor of the distribution network after tripping.What's more,it can effectively identifythe fault state of non-high-resistance phase-to-phase faults before reclosing,and provides a useful theoretical basis for realizing adaptive reclosure of phase-to-phase faults and imporving the success rate of reclosure in distribution network.