Research on Transient Discharge Characteristics and Optimization Strategy of OLTC Change-over Selector

In order to limit the transient voltage between the change-over selector contacts, a tie-in resistor is connected between the middle of the regulating winding and the end of the main winding. If the value of tie-in resistor is not appropriate or the configuration is unreasonable, it will lead to discharge, gas production during polarity conversion and long-term overheating. Aiming at the above problems, this paper establishes a converter transformer simulation model, analyzes the development process of the transient discharge between the switch selector contacts during the polarity transition of the on load tap changer. The relationship between the transient voltage and the transformer structure parameter are obtained. And the variation rules of the recovery voltage and capacitive current between the contacts of the polarity transfer switch with different tie-in resistor values are analyzed. Finally, an optimization strategy for the selection and layout of the tie-in resistor is proposed to guide the more reasonable configuration of the tie-in resistor of the on load tap changer, considering the recovery voltage, capacitive current and oil tank heating between the contacts of the change-over selector.