Development of support system for setting and coordination between protection relays
The opportunity for distributed generators to be connected to the power system has been increasing since the introduction of electricity deregulation. Moreover, a power system which has a new concept such as a micro-grid or a smart-grid is going to appear. The increase in the uncertainty of power flow and the power system operation under an irregular system configuration is supposed in such new power systems. And the sensitivity of a protection relay may decrease or a protection relay may miscoordinate with other protection relays. Under the above conditions, to prevent the fault expansion is required of the electric power utilities. From the background, the development of a program that can check the relay setting and the coordination between protection relay systems is desired. The development of "Support System for Setting and Coordination between protection relays" called SSSC was initiated in 2006, and it will be completed in 2011. SSSC has the following features; It enables us to check whether the protection relay is set as operate correctly against all of assumed system faults. It enables us to check automatically whether the coordination between the protection relays is proper as prevent the fault extension even if an unexpected condition occurs. It enables us to analyze the response of the protection relays in the power system where some apparatus with nonlinear characteristic is installed. This paper describes the prototype of the SSSC based on the dynamic analysis like Y-method. Furthermore, in this paper, the checking method of coordination between protection relays for short circuit fault, and the verification results of the prototype in the 6.6 kV model distribution system are described. 2010 The Institute of Electrical Engineers of Japan. protection relay,.