Research On Key Technology Of Self-healing Of Low Voltage Busbar In 220kV Terminal Substation

Along with the rapid development of society,electric energy has become more and more important to industrial production,Internet,human activities and so on.Therefore,improving the reliability of grid constantly is the unchanging gaol for electric power industry.Now,some of 110kV substations and 220kV substations are designed to be the terminal substation,their main power supply is unique on the side of 220kV bus,which causes a great probability for the entire substation to be in no-voltage situation.Aiming at solving the voltage failure in Quqing 220kV terminal substation,a self-healing project for the loads on the side of 110kV bus is proposed in this paper.By the implement of self-healing project after voltage failure,the loads can get fast supply restoration.Considering the small-capacity hydro-power plant and the back up power supply on the side of 110kV bus,a self-healing system based on wide-area monitoring and control platform with intelligent device and communications network is constructed.The voltage failure situations on the side of 110kV bus discussed in this paper include:?two transformers operate in splitting mode,the main transformer trip;?only one transformers operates and trip;?two transformers operate and trip or the substation lose its main power supply.The first two cases can get fast restoration with the operation of BZT,but for the third case,the substation cannot avoid the loads to lose their power supply,meanwhile,the traditional load shedding method cannot prevent the loads to be over-sheded or less-sheded in a short time.After the voltage failure of the entire substation,a part of secondary loads need to be shedded to support small hydro-power plant operating continuely in island mode,the shedded loads can be restrored latterly by connecting the back up power supply.Two key technologies in self-healing scheme are discussed in the paper:one is topology identification technology base on full connectivity matrix,another is real-time unbalanced power control technology,the former is applied to discriminate the operation mode of small hydro-power plant,the later is applied to switch power supply scheme in a rapid and smooth way.The topology identification in power sysrem is applied to divided buses and electrical island,it is a basic function module for energy management system and distribution managemane system providing grid topology parameter information for flow calculation,state estimation,fault analysis and so on.On the base of reading lots of literature,this paper proposes a topology identification technology base on full connectivity matrix,monitoring the status of switch to identify the topological structure in substation.The topology identification technology is applied to discriminate the operation mode of small hydro-power plant.This technology is adapt to the switch topological structure in substation and can update in short time,it is applicable to a variety of operating mode.After the small hydro-power plant operating in island mode,in order to insure the power supply for first important load,the secondary loads need to be shedded to balance the active power.This paper proposes a fast real-time unbalanced power control technology to shed loads rapidly,make the small hydro-power plant operate stablely.The unbalanced power calculation is based on real-time monitor on loads and power supply,once the result of topology identification indicates the small hydro-power plant operating in island mode,the real-time unbalanced power control starts immediately to shed load according to the switch status,limit the unbalanced power into specified range.The real-time unbalanced power control technology can prevent the loads to be over-sheded or less-sheded.Finally,this paper proposes a loads shedding strategy based on analytic hierarchy process to control the unbalanced active power,moreover,this paper indicates the whole control ought to proceed within the max critical clearing time.