Tests on the on-load tap changer (OLTC)
WHY DO WE PERFORM OLTC TEST? The on-load tap changer (OLTC) is the only moving part in a typical power transformer, it permits tap changing and regulating voltage without affecting the network operation. This frequently movements between transformer taps makes the OLTC components the most vulnerable, which implies regular testing and maintenance. On the other hand, by using a conventional static winding resistance measurement, it is hard to detect any anomalies during the switching process because of the fast movements of the OTLC’s switches (40-60 ms). Many mechanical parts are not easily accessible for inspection, and it is recommended to perform additional tests to establish the OLTC condition. Usually, winding resistance measurements are performed on offline power transformers. In [...]