Use of directional overcurrent protection scheme for distributed generation systems

This paper proposes protection scheme of distributed generation systems based on adaptive directional overcurrent protections with inverse-time characteristics. First, protection of distributed generation system is compared with classical conception system and individual differences in protection settings are discussed. Proposed protection scheme is composed of individual protections connected by communication lines. These lines inform protections about the present network configuration and in the case of changes in protected system new protection setting is computed. Use of directional overcurrent protections with inverse-time characteristics allows us to create protection settings resistant to small variations in short-circuit currents. This paper describes protection coordination for an example of network configuration. For the correct setting of inverse-time characteristics, and also its validation, short-circuit conditions in every node of network are required, and program SimPoruchy 2.0 [1] was used. Program allows for quick and well-arranged output of short-circuit conditions of network and also for simulation of mentioned protection types.