Zhan Rongrong

The delay optimization of circuit breaker failure protection based on the CT current tail truncation algorithm

Circuit breaker failure protection (CBFP) is a widely used back-up protection in electrical power system. To avoid maloperation, the CBFP needs a long delay to confirm the status of the circuit breaker, which means the cut off time will be long, sometimes too long to keep the stability of the power system. Therefore, it is very important to propose an optimized method to calculate the CBFP delay time for improving the stability of the system. A CT current tail truncation algorithm based on a CT tailing current-short circuit current criterion plane has been shown in this paper, which can truncate CT tailing current quickly and thereby shorten the delay of CBFP. Without special configuration of P level CT, this algorithm ensures the reliability and rapidity of CBFP, significantly reduces the risk of system operation, and has good economic benefits.

Construction of relay protection testing platform for distributed power access to distribution grid

This paper presents the impact of distributed generator (DG) accessing to distribution network on protective relaying at home and abroad, according to the current situation of experimental research analysis the necessity of test method research. Set up electromagnetic transient model of three common distributed power photovoltaic (PV), doubly-fed induction generators (DFIG) and permanent magnet synchronous generator (PMSG) on PSCAD/EMTDC platform; Set up physical model of three common distributed power photovoltaic (PV), doubly-fed induction generators (DFIG) and permanent magnet synchronous generator (PMSG) in dynamic simulation laboratory. Comparing simulation results of distributed generators electromagnetic transient model and physical model under the same fault conditions and control strategy, verified the validity of the laboratory physical model. On the basis of the physical model, construct dynamic test system to test protective relaying for distributed generators access to distribution network, which can realize closed loop for relay protection device from every manufacturer. At the same time test results laid the foundation for the improvement of the existing distributed power relay protection device and put forward the new principle of relay protection.