Abstract
Protective relay play the important part in the safety of power system, and switching power supply for relay protection is the mail functional modules for protective relay, power performance to a direct impact on the reliability of relay protection devices. In the power plant and transformer substations, the DC operation power is supplied from high frequency switching power supply (HF SPS) and uses bulky batteries as alternative power. The paper analyze the present situation development of high frequency switching power supply domestically and overseas, study and research the basal principle of HF SPS and its application in electric power system, then design HF SPS applied in electric power system. System exceptions, such as over-voltage, over-current, etc, are dealt with by carefully designed protection circuits. The reverse excitation circuit is applied for the power circuit. We get static outputs by using the methods of feedback and pulse-width modulation. Because the switching power supply for relay protection system, the switching mode power supply has many advantages: light weight, small physical size, high reliability, etc.
Key word switching power supply;relay protection; reverse excitation circuit