Noninvasive on-line condition monitoring of on load tap changers

The paper describes a condition monitoring and diagnostic monitoring system developed for power transformer on-load-tap-changers (OLTCs). The system has been installed in distribution substations to continuously monitor the operation of OLTCs on 33/11 kV power transformers. The field trials have demonstrated that the system can provide reliable indication regarding the actual condition of OLTC contacts. Also presented in the paper are the details about an industry survey on failure modes of commonly used OLTCs in Queensland electricity transmission and supply industries.