OMICRON Magazine

PD magnitude Filter bandwidth BW: 50 … 150 MHz UHF sensor frequency response ~ 100 MHz ~ 12 GHz freq BW variable: < 20 MHz PD magnitude Variable center frequency freq Variable center frequency PD magnitude freq The measurable signal spectrum depends heavily on the situation. Due to the encapsulation of the GIS, the signalto-noise ratio can be quite good. However, with PD sensors closer to the outdoor bushings, outside disturbances can still be measured in specific signal frequency ranges. This can influence the measurement sensitivity, especially when only a simple broadband measurement is performed. Broadband measurement methods are quite common, but medium-band and narrowband measurement methods are more selective and robust against external noise. The variable narrowband measurement method, in particular, makes selecting frequency windows free of interference in onsite testing environments possible. Finding an optimal signal-to-noise ratio A suitable measurement frequency window can be identified by simply observing the input frequency spectrum in which a high signal-to-noise ratio (SNR) results in high measurement sensitivity. Suitable frequency windows with acceptable SNR can even be found under challenging conditions with high external noise levels. Therefore, you can improve PD measurement results onsite despite elevated levels of interference by using a frequency-­ selective PD measurement system that allows you to switch between different measurement modes, bandwidths, and center frequencies. Our UHF 800 PD measurement system allows you to select from various measurement modes – (a) broadband mode, (b) medium-band and (c) narrow-band modes with selectable measurement frequency and bandwidth. disturbance-free test environments, such as in a test lab, and require minimal setup effort. For disturbance-prone onsite test environments, medium-band and narrowband measurements with different bandwidth filters provide you with a more selective measurement. Therefore, they reject external noise and disturbances effectively. Test setup for PD detection and localization in a GIS Laptop or office computer with MPD Suite software UHF PD Sensor UHF PD Sensor OMICRON fiber-optic cable MCU2 OMICRON fiber-optic cable Optional: Sync via voltage from VT grounded grounded UHF PD Sensor VT UHF 800 RBP1 UHF 800 RBP1 UPG 620 22