Research On Relay Setting Coordination For County-level Distribution Power Grids

Relay is used to ensure the reliable running of the distribution power grid. Its correct operation is quite important. Thus the reliability, sensitivity, selectivity and speed of the operation are required, which can be obtained using proper relay setting coordination. From the current situation and characteristics of the distribution power grid in Zhuji, we introduced the regular protection principle of the distribution power grid, analyzed the examples based on the relay setting coordination and the effect of the small power grid on the regional power grid. The details include:In the first part, we introduced several protections in the distribution power grid in Zhuji, including three section type current-voltage protection, grounding distance protection and transformer protection. We discussed the principles of these protections and the setting coordination. We also gave the matters needed attention in the interaction of the setting coordination.In the second part, based on the theoretical analysis and the situation in Zhuji"s distribution power grid, we elaborated the use of the setting coordination with examples. We discussed the methods to deal with the protection mismatch due to the higher compression in the county-level power grid, T connections and the lack of the sensitivity due to the transfer between the levels when the power is transferred between the electric power substations. By analyzing the power loss due to the interconnection of the small power grid, we discussed the effect of the small power grid on the main protection and setting coordination and then presented a method to improve the protection configuration of the main distribution power grid.Based on the examples and the characteristics of the distribution power grid in Zhuji, the above two parts should be helpful to the flexible treatment in the setting coordination system.In the last part, we introduced the setting coordination software which is suitable to the local distribution power grid, including the design principle, function, various methods of manual interposal and flexible treatment to the regional distribution power grid.