Research On Application Strategy Of Improving Operation Reliability Of Standby Automatic Switching Device In Zoucheng Power Grid

The automatic switching on device of standby power supply is the key equipment to improve the power supply reliability of power grid,and one of its action logic is bus voltage loss.With the large-scale integration of distributed generation,the power flow of distribution network changes.Since the distributed generation can support the bus without loss of voltage after system failure,the standby automatic switching is refused to operate,and the power supply reliability of the system cannot be guaranteed.Moreover,due to the variety of the main connection line type of the terminal substation,improper locking mode or starting conditions may lead to the failure of standby automatic switching on and the extension of power outage scope.Therefore,this paper studies the impact of distributed generation access on standby automatic switching,and proposes improvement strategies to ensure the reliability of power supply and provide high-quality power supply service for users.On the basis of systematic study on the working principle of the standby power supply automatic switching system,the defects of the standby automatic switching mode under the conditions of internal bridge connection and single bus section connection in Zoucheng power grid are analyzed.Among them,when the main transformer protection acts,the improper locking mode of the internal bridge connection may lead to the power loss of the whole substation.When the bus voltage is lost,the standby automatic switch with single bus section connection can not distinguish the line fault from the bus fault,which leads to the risk that the standby power supply may fail.In view of these two situations,the action logic of standby automatic switching is improved,and the corresponding simulation model is established for verification.With the distributed generation access to the distribution network,the original passive attribute of the distribution network is changed.For the situation that the no voltage condition can not be satisfied and the automatic bus transfer equipment can not operate due to DG access,this paper proposes an improved strategy for the automatic bus transfer equipment to be switched on simultaneously with DG After the regional distribution network enters the island state,the condition of synchronous closing is created according to the relationship between DG output and load.In this way,the automatic bus transfer equipment can be switched on at the same time with the cooperation of the synchronization device and the low frequency load shedding device.When the output of DG is greater than the load,the stability of voltage and frequency can be realized by DG control system,and the conditions of synchronous closing can be met.When the output of DG is less than the load,part of the load should be cut off to make it meet the automatic switch conditions of the same period as much as possible.Then the synchronization device captures the closing point of the synchronization.The switch on command is output to the automatic bus transfer equipment,and the automatic bus transfer equipment closes the emergency generator switch.If the synchronization is not successful or the load that can be removed is less than the load to be cut off within the specified time,the DG will be cut off and then the logic judgment and action process of conventional automatic bus transfer equipment will be reentered.Finally,a simulation model is built in MATLAB/Simulink to verify the improved automatic bus transfer equipment mode based on main connection type and distribution network with DG The simulation results show that the improved automatic bus switch can eliminate the defects of internal bridge connection and single bus section connection.Moreover,it can realize the function of synchronous closing automatic bus transfer equipment with DG,and improve the reliability of the equipment.