Protection Coordination in Networks with Renewable Energy Sources

The increased distributed generators (DGs) in distribution networks are causing protection coordination problems. Due to the many generation sources supplying the distribution network, the conventional protective devices have become insufficient to ensure the proper protection coordination in case of a fault.This dissertation illustrates the summary of the DGs’ influences and an overview of the approaches for selecting and coordinating the protection system with or without DGs. Two example networks have been used to demonstrate the specific coordinating methods and problems for an overcurrent-based scheme and a distance-based scheme with the help of the DIgSILENT PowerFactory software package. One example is a radial medium voltage network mainly protected by overcurrent (OC) relays, which has potential false tripping and blinding effects. Another one is a typical UK meshed distribution network which may suffer the under reaching for distance relays that occurs on the basis of the distance-based protection scheme. The protection system for each network will be used to prove the success of the derived settings and also the successful coordination of protective devices by discussing the time-overcurrent plot, R-X plot and time-distance plot. The proposed new protection schemes for these distribution networks have achieved the orderly protection operation in case of a fault, namely the appropriate protection coordination.