A discharge locating probe for rotating machines

The Tennessee Valley Authority (TVA) probe permits location of partial discharge (PD) since it is sensitive to radio frequency signals produced by PD. However, the present TVA probe has limitations both in directionality and in providing quantitative measurements for comparison of different windings. The authors present the basic principles of detection of an improved TVA probe, known as the discharge locating (DL) probe, which was developed to be an evolutionary upgrade to the TVA probe. The principal features of the new device are very-high-frequency detection using a capacitive sensor and microprocessor-based signal processing. These features are intended to make the probe easier to use and less ambiguous in the interpretation of results. The coupling technique used permits significantly improved spatial resolution of the discharge source and immunity to radiated electrical interference. Field evaluation of the DL probe has generally been successful, with the results confirming theoretical and laboratory-based studies of the device