OLTC in-place check enables to conduct express diagnostics of the OLTC technical condition without opening the tank or OLTC removing. This check enables to obtain the contactor switchover diagrams for a wide range of switching devices (except reactor type ones) and conduct the OLTC condition evaluation based on the obtained diagrams, that gives the reasons to denote a defect nature and grounds for decisions related to repair of these on-load tap changers.
For example, for type RS, RNOA, etc., on-load tap changers the correctness of operation of the main and arcing contactor contacts, their condition (burned or not burned contact), current-limiting resistor integrity may be determined. For type RNTA – 35/320 on-load tap changers and in the analogous on-load tap changers, in which the contactor and selector are changed for a fine control circuit breaker, the main and arcing contacts, current-limiting resistor condition, as well as condition of surface of all fixed contacts of the circuit breaker, through which the moving contacts move, may be checked.
The application of in-place check mode based on the DRM method doesn’t require:
- Opening of the tank or hatch of the fault-free/faulty OLTC and oil drain;
- Additional money and labor costs for the OLTC diagnostics;
- Connection of additional elements or knowledge of resistances of current-limiting resistors of the checked on-load tap changer, since all fine adjustments to a certain OLTC are conducted automatically in the instrument.