Intelligent control of on-load tap changer of transformer

The on-load tap changing transformer can maintain voltages at desired levels by changing the tapping in primary winding of the transformer according to the load. It plays an important role in smart distribution grid. The key part of on-load tap changing transformers is on-load tap changer (OLTC), which is a complex mechanical device. The diverter switch of OLTC is traditionally accomplished in the oil. The Oil will be stained by arcing during operation and must be consequently purified by an oil filter. In order to reduce the disadvantages of conventional oil switching OLTC, OLTC applied with vacuum switch is presented in this paper. This vacuum OLTC is driven by permanent magnetic actuator. The capacity and the switching reliability of the vacuum OLTC are remarkably enhanced. The electrical life as well as the maintenance interval of the OLTC has been extended. In consideration of the electromagnetic field on site, Programmable Logic Controller (PLC) is applied to the intelligent controller of OLTC. The action sequence of the vacuum diverter switch is programmed based on the structure of vacuum OLTC. The controller using PLC can greatly decrease the complexity of the OLTC control system and effectively improve the reliability and stability of the vacuum OLTC.