The OLTC is the major mechanical moving device on a transformer. As with any mechanical device, movement equates to the wear of components over time and frequency of operation. The OLTC failure modes can be the same or segregated, depending on the type of testing or monitoring performed. Some failure modes can be detected with sensors and systems.
Implementing online monitoring for an OLTC is relatively easy. There is a mechanical operations counter on every OLTC. It records an event (cumulative) every time the OLTC operates. The tap position indicator on every OLTC is a mechanical device. It provides the current tap position and the ‘range of movement’ the mechanism has operated. The movement is recorded using resettable drag hands on the indicator.
