A DRM technique for OLTC testing by the transformer secondary winding DC voltage curve

. The dynamic resistance measurement (DRM) method was developed as a supplementary for testing the transformer on-load tap changer (OLTC) and has become popular in recent years. The DRM method has proven to be an effective method for early detecting potential faults in tap changers. The traditional DRM method is based on a DC current being injected through a transformer winding and a tap changer as it moves from the tap to tap. The measurements are carried out in the tested transformer winding under shorted secondary winding. The article presents a new conception of the DRM method, where the OLTC condition is tested by a voltage curve, that is logged on the no-load secondary transformer winding.