Studyon Zoning Strategy And Relay Protection In Black Start Of Hydropower Station

Black start is usually an important option for power system restoration after large accidents.Therefore,after establishing a reasonable recovery measure after large-scale accidents,it can effectively speed up the process of system recovery and reduce the outage cost to a certain extent.Otherwise,it may delay the progress of recovery,even expand the scope of the impact of the accident,and further cause more serious consequences,resulting in more losses.Usually,large scale complex power systems contain multiple self starting units(black start power).After large blackouts,partial parallel restoration of the system is carried out,which can speed up system recovery to a certain extent.It can reduce the power outage time of users to a certain extent,and reduce the impact of blackout on the national economy and people's life.Therefore,the proper partition operation for the system after blackout is very important to the recovery of the system.In addition,the key to successful black start is to make the recovery process in a predetermined controllable state,so reliable relay protection configuration is also important for the smooth start of black start.Based on the characteristics and requirements of the black start system,we simplify the system into an undirected-weight network according to a certain principle.The weight of the edge in the network equals the sum of reactance and susceptance of the transmission line.Determine the independent black start power node in the network as the initial cluster center and select the appropriate initial cluster radius for initial clustering.By analogy,all nodes are finally divided into different clusters.When the existing boundary nodes can not be divided,the module degree is calculated.The maximum module degree function is the best partition result.Finally,check the internal network topology and power flow constraints of each subsystem.If satisfied,it is the final partition.Otherwise,the boundary nodes will be redivided.The examples of the New England 39-bus system and 118-bus sysytem verify the feasibility and effectiveness of the algorithm.with dealing with the independent processing of multi-level long circuit in the process of black start,the distribution characteristics of the sequence voltage and the sequence current of the system under different operation modes are analyzed in detail.It proposes a fault identification method in this paper.The method selects likely fault buses by comparing buses sequence voltage.Then the fault identification method on comparison of amplitude and incidence matrix of sequence current calculated by sequence voltage and current and line parameter is proposed to judge the position.This algorithm needn't to setting again.It could be immune to various complex conditions and it can not be mistakenly operated when the over-voltage generated by the charging of the no-load line.This fault identification algorithm can be used as backup protection in the normal system and it also can be setted as main protection in the single supply mode of black-start system.