Design of intelligent on-load tap changer controlled by permanent magnetic actuator

Traditional mechanical OLTC has some disadvantages while changing the taps, such as causing arc, switching slowly, having high malfunction rate. This paper proposed a kind of intelligent OLTC which equips with vacuum interrupters controlled by permanent magnetic actuators (PMA) as its switching parts. In this paper, the overall structure and electrical circuit scheme of the OLTC were designed on the basis of the simulation results under different circuit conditions. The type of vacuum interrupter and the transition resistance was theoretically analyzed and calculated. Furthermore, the hardware design and software development of intelligent OLTC controller were completed based on digital signal processor (DSP). An experimental prototype of intelligent OLTC has been developed, in which the controller takes power from the secondary side of transformer and the rectifier circuit has been used to recharge the capacitor array which acts as the power source of PMA. The capacitor-charging circuit, voltage and current measurement circuit, PMA-driving circuit and overvoltage absorption circuit were designed. The power supply module of the controller had been allocated systematically, so that the supply side of the controller and the main circuit of OLTC were electrical isolated. Finally, the switching experiments have been carried out for verifying the functions of the OLTC prototype. The results indicated that the intelligent OLTC prototype can switch off the circuit current precisely around the current zero point, and adjust the taps' positions of transformer automatically to complete the voltage regulating task. Moreover, it has the advantages of simple structure, satisfies the requests of miniaturization and intellectualization.