Design Of Self-Powered Relay With Time Overcurrent And Earth Protection

At present, the status and trend of relay technology is developed toward computerization, network, intelligence, protection and control measurements and data communications integration.However,according to the problem that the existing digital protection devices can not meet specific application requirements such as where power is needless, or where power can not be installed, or harsh outdoor applications, environment, a self-powered time overcurrent digital relay design is brought out in this paper. It can perfectly address the power supply from the second issue of the protection device which make the special occasions such as column switch or circuit breaker have a fully functional and reliable protection.At the first, this paper made a brief introduction on the development of relay protection at home and abroad and pointed out the merit and shortcoming of the existing protection devices. The existing computer protection algorithms is simply explained, with emphasis on the Fourier algorithm and least square algorithm. A detailed theoretical derivation of the Fourier algorithm and least squares algorithm was carried out and they were simulated using MATLAB. Then we analyzed the three sect current protection principle and its parameter adjustment. Finally, according to the system design requirements, proposed and implemented the specific hardware and software design of a self-powered relay. It can directly obtain circuit energy from current transformers with secondary which expanded the application of existing protection and had a practical significance for the follow-up protection device research.