Diagnosis of On-Load Tap Changer (OLTC) using dynamic resistance measurement

On Load Tap Changer (OLTC) is one of the important and most expensive sub-components in a power transformer. The fail operation of OLTC can cause catastrophic failure of in-service power transformers. Proper and adequate maintenance conducted on serviced aged OLTC can reduce the unexpected unavailability and failure rate of power transformer. Nowadays, several off-line and on-line diagnostic techniques have been used to diagnose the condition of load tap changer. These diagnostic results are important to determine the required maintenance on OLTC. In this paper, the condition of OLTC on in-service transformer was assessed using the dynamic resistance measurement. The results from new unit of OLTC installed in power transformer at the factory and on serviced aged OLTC were presented. The findings suggested that the technique is very promising in detecting problem associated with the contact wear and early stage of contact degradation in OLTC.