Matlab/Simulink based dynamic simulation system for distance protection

To observe the inner operating process of distance protection, a Matlab/Simulink based dynamic simulation system for microprocessor-based distance protection is designed in this pa- per. As a modularized design, the simulation system is composed of several modules such as fault transient calculation, startup, Fourier algorithm, phase selection, impedance computing and im- pedance comparison etc. Some typical simulation cases, which focus on the main factors affect- ing distance relay's operation, have been simulated with the system. Simulation results show that the system is able to demonstrate the dynamic behaviors of distance protection under different op- erating conditions.     

Vector shift method for islanding detection based on simulation test

Vector shift (VS) is one of the typical methods used for islanding detection in distributed generations. This paper investigates the impact of both the active power imbalance and load variation on VS method. The investigation was conducted via simulation test in the power system dynamic simulation laboratory of Shandong University. The results show that it will take longer time for the VS relay to detect islanding state with the decrease of active power imbalance. In some cases, the vector shift angle is smaller than the setting and VS method would not be able to detect islanding state. In addition, the performance of VS method is impacted by the load variation in normal operation in which the distributed generator is operated in parallel with the main grid. The simulation results show that VS method would cause nuisance tripping if the load changes sharply. It can be summarized that VS method would be unable to reliably discriminate islanding state and normal system disturbances in some cases.     

Fast fault isolation and restoration of looped MV network

A new fault isolation and restoration technique employing local Ethemet network for the looped MV circuit is presented. It can isolate all short circuit faults in the loop within 300 ms and restore the supply of healthy sections in less than 1.2 s. A reliable fault location method of isolating the single phase-to-ground fault （SPGF） in the non-effectively earthed network, which makes use of the fault generated transient signals, is also proposed. And the method locates the SPGF by examining transient zero-mode current correlation, which is not influenced by the neutral grounding mode and need no additional device. Laboratory test and simulation results show the proposed techniques are feasible, and significantly improve the supply reliability.