Unconventional measurement technology in ultra high frequency (UHF) ranges (MHz to GHz) is commonly used for on-site PD testing. This has the added benefit that an online test (i.e., no need to shut off the equipment under test) can be conducted since the measurement method does not require galvanic coupling to the high voltage conductors. Stronger attenuation of distant signals allows for very favorable signal-to-noise ratios and locally selective PD tests.
UHF PD Sensor Models:
UHF passive sensor
UHF drain valve sensor for transformers
UHF bushing sensor for transformers