Dynamic tap-changer testing, reactors and reactance

Dynamic resistance measurement (DRM) – a diagnostic technique that has recently been attracting a lot of attention due to its capability to detect On-load tap-changers (OLTC) problems – is discussed in this paper as applied to variable shunt reactors (VSR). Specific features in the current traces are explained. In addition, there is discussion of principles and DRM features as well as presentation of defect cases for reactance type of tap-changers tested using DRM methodology.