OMICRON Magazine

Laptop or office computer with MPD Suite software

MCU2

Test setup for PD detection and localization in a GIS

OMICRON fiber-optic cable

UHF 800

UHF 800

OMICRON fiber-optic cable

grounded

grounded

Optional: Sync via voltage from VT

VT

RBP1

RBP1

UPG 620

UHF PD Sensor

UHF PD Sensor

UHF PD Sensor

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 measure ments with different bandwidth filters provide you with a more selective measurement. Therefore, they reject external noise and disturbances effectively.

The measurable signal spectrum depends heavily on the situation. Due to the encapsulation of the GIS, the signal to-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 vari able 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 identi fied 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 challeng ing 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.

Filter bandwidth

UHF sensor frequency response

PD magnitude

freq

~ 100 MHz

~ 12 GHz

BW: 50 … 150 MHz

PD magnitude

freq

Variable center frequency

BW variable: < 20 MHz

PD magnitude

freq

Variable center frequency

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.

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