Devising a new protection characteristic depending on voltage for power systems including distributed generation

Re-evaluation of protection systems is now a requisite for the reliable operation of power systems, regarding the structural changes over the last few years. Integration of distributed generations (DGs) connections and microgrid (MG) operation are among the most crucial factors that may pose a threat to protection systems. Fortunately, the emergence of digital relays enabled the opportunities for providing alternative approaches to standard ones as a remedy to mitigate the impact of recent changes. Taking the aforementioned facts into consideration, this study suggests an alternative method to the traditional protection approach in power systems. For this purpose, studies dealing with the protection issues induced by DG connections and MG operation in the literature were reviewed in detail and the indispensable features for constructing a non-standard characteristic were listed. A method was proposed so as to tackle with the protection problems, devising a non-standard characteristic and providing a dual characteristic protection approach. The method was tested on the IEEE 14 bus system regarding various DG scenarios and results were presented in comparison with the conventional protection approach using standard characteristics. Relay coordination problem was cast as an optimization problem and the problem was solved using genetic algorithms. The results showed that a more rapid protection may be achieved utilizing the proposed approach than by using the conventional protection strategy. Furthermore, it is also possible to provide reliable protection by ensuring protection coordination even when the power systems are exposed to the high penetration of DGs, using the proposed method.