Onload tap changer (OLTC) forms an integral part of the transformer contributing in great measure to its overall reliability. With the use of ester oils in transformers, it has become necessary to critically evaluate the performance of ester oil filled OLTC for its application in transformers. This paper details the capability evaluation through critical experiments conducted on ester oil filled OLTCs. The test chosen was the service duty test as per IEC 60214-1. Many properties and health parameters of the OLTC test samples were monitored before, during & after the critical service duty test of 50000 operations to ensure the adequacy of the performance. Based on the evaluation, the paper concludes that the ester oil filled OLTCs perform satisfactorily without any need for any major design modification or change of the assigned ratings of the OLTC. Tests were conducted on various OLTCs using selector switch operating principle and diverter switch operating principle.
Ester oil filled OLTC, Service duty test, Performance parameters of OLTC, Critical evaluation of ester filled OLTC, Performance comparison of mineral oil and ester oil filled OLTC
