A new integrated protection scheme for distributed generation systems

This paper presents a new integrated protection relay and its associated scheme for distributed generation systems. In the scheme, an integrated relay is responsible for the protection of both line sections associated with the substation bus. Based on conventional directional overcurrent protection technique, the basic principle of the new relay is to determine whether a fault is on the protected line section or not by detecting the operation of the remote circuit breaker on the protected line section, subsequently accelerated operation can be achieved. In addition to the conventional overcurrent protection, the relay developed consists of a number of new protection functions: the directional under voltage; the accelerated overcurrent and the accelerated directional under voltage protection. The paper presents the simulation results with respect to typical distributed generation systems. Results show that the relay and its associated protection scheme are able to not only significantly increase the speed of response of the conventional time grading based protection scheme for distributed generation system, but also provide features of integrated protection.