Research On Operation Strategy Of High Reliability Distribution Network Automation

Distribution network is an important link between power users and generation and transmission,If it fails,it will lead to partial power failure in the distribution network,and even the whole network will be cut off,It cause much inconvenience and economic losses to the production and life of power consumers.The demand for power supply reliability of high and new technology industrial development zone is higher,Voltage fluctuations and short time blackouts will cause huge losses.This paper summarizes and explores the practical experience of distribution network operation in one High-tech Industrial Development Zone,It is pointed out that only with the transformation of power grids to realize distribution automation in distribution networks,In order to provide high-quality electric power for the vast number of power users.At present,current differential and voltage-current modes are the main operation strategies of conventional distribution automation.In this paper,the action principle is studied separately,and the engineering design method is summarized according to the actual operation.Combined with fixed value calculation,the action strategy of typical model grid is studied.Finally,the effect of the action strategy is verified by the actual operation line.The advantage of the current stage difference strategy is simple and effective,and it is not easy to make mistakes.The disadvantage is that too many automatic switches in the main line cascade can not cooperate through the stage difference,resulting in protection mismatch and can not achieve self-healing.Voltage and current mode strategy overcomes the shortcomings of current stage difference strategy,solves the problem of too many trunk cascades can not cooperate,and can achieve self-healing,but the logic is complex,and the operation is prone to misoperation and rejection.Based on long-term operation experience,the operation strategy of intelligent distributed double-loop network is summarized to solve the problems of current stage difference and voltage-current mode.The first feature of the strategy is the optimized double-loop network structure,that is,the buses of two different substations each send out two routes to the contact points.In order to ensure the operation of N-2,the contact points are set as "well-shaped".The second feature is that the main line of each circuit is divided into several sections.Each section is equipped with an automation switch.The two adjacent automation switches communicate with each other through optical fibers to form optical fiber differential protection,which ensures that the automation switch of the main line can selectively isolate faults and solves the problem of current differential strategy,that is,too many trunk lines in series lead to the loss of the automation switch.Selectivity;The third feature is the operation of the ring network,which minimizes the user's perception of short-term power outages when isolating faults.The disadvantage of this strategy is that it relies on optical fiber communication.Once the optical fiber is destroyed,the differential protection will fail.Therefore,two optical fiber channels are usually needed.Through demonstration,the action strategy of intelligent distributed double-loop network is superior to current differential action strategy and voltage current action strategy in fast locating and isolating faults,automatic power transfer in non-fault area and reducing power outage of users.