Design of Self-supplying Power Source Applied in Digital Relay

At present, the vast majority of relay protection devices depends on a reliable on-site power supply to work. Its power supply of work and operation circuits require substation or distribution room to provide AC or DC power supply. This paper introduces a design of self-supply power source applied in digital relay. The energy is obtained directly from the power line by some tailor-made iron core current transformer (CT). The signal, output of the rectifier circuit, is the input signal of sampling circuit and can also charge energy storage capacitor at the same time. An integrated switching regulator changes voltage signal, terminal of the energy storage capacitor, into stable DC voltage signal, as the DC regulated power supply of digital relay. The approach can avoid the saturation problem of core coil when primary current change in a larger range by increasing the air gap in the core coil and introducing air-gap magnetic reluctance. So that the back-end circuit is significantly simplified and the reliability is improved. The power supply module can be used in relay protection of power system with 10 kV voltage level and above and on-line monitoring devices, which has a broad application prospects.