New Load Shedding Method for Dealing with Critical Conditions of Smart Network Caused by Fault-Induced Delayed Voltage Recovery

The phenomenon of Fault-Induced Delayed Voltage Recovery (FIDVR) appears in networks with high penetration of induction motor loads because the increase in requested reactive powers of motor loads after clearing the fault prevents the rapid return of the bus voltage to the pre-fault level. Load shedding is one of the effective ways to deal with the FIDVR phenomenon, which causes the amount of demand to approach the production of reactive power. In this paper, a wide-area load-shedding method is presented, which performs based on network conditions and loads. Since the introduced indicators for determining the locations and amounts of loads to be shed are based on the values of bus voltages, loads currents, and network impedance matrix; therefore, the proposed method can effectively shed the loads and deal effectively with FIDVR. The voltage estimation process is an important tool to predict the voltages at future moments and is defined based on the modified Gauss-Seidel load flow and the three-order model of the induction motor. This tool enables the proposed method to understand the effect of applying load shedding on voltage recovery and prevents the application of unnecessary ones

Optimal coordination of directional overcurrent relays considering non-standard curves and multiple network topologies using tlbo-lp

In this article, Directional Over-current Relay (DOCR) Coordination was performed considering various network topologies and the non-standard curve for the overcurrent relay. In practice, usually the network topology changes by switching lines and the overcurrent relay coordination might be removed. The purpose of this article is to maintain relay coordination while the network topology is changed and to get the best setting and reduce the operating time of relays. For coordinating and setting overcurrent relays, a hybrid TLBO method was used which combined Teaching-Learning Based Optimization (TLBO) and LP. Four variables were used to set overcurrent relays and the algorithm obtained specific settings for each relay. The proposed algorithm was also compared with the conventional methods. The results show that the TLBO-LP method and using non-standard curve will improve the operating time of overcurrent relay, increase coordination between them and maintain the DOCR coordination by changing the network topology and switching line