UHF Sensor for Partial Discharge Testing

UHF or ultra high frequency testing is one of the most powerful and versatile methods for partial discharge detection in open air switchyards. By using the UHF receiver, the UltraTEV Plus 2 (UTP2) is able to detect partial discharge sources in the UHF band. UHF testing can be utilized as a first pass safety tool for substation entry or as a surveying tool to pinpoint individual sources of partial discharge. This article will discuss the operation of UHF measurement equipment, the best applications for it, and its benefits over other PD detection methods.

What is UHF?

Ultra high frequency is the designation for radio frequencies in the range between 300 megahertz and 3 gigahertz. UHF is used in digital television broadcasting, mobile phone networks, Bluetooth network devices, and our focus, partial discharge detection. The UHF receiver for the UTP2 operates between 5 MHz and 3 GHz, it offers narrowband and wideband modes, in wideband mode the full bandwidth of the signal is received by the UTP2 at all times. In narrowband mode, the UTP2 operates around a central adjustable frequency. The receiver can be used with either a directional antenna or an omni-directional whip antenna, the whip antenna is good to quickly detect if there are any partial discharge signals present in the switchyard while the directional antenna is used to find the discharging equipment.

UHF Sensor Applications for PD Testing

As mentioned in the introduction, UHF testing is particularly useful for outdoor switchyards. UHF is an online test method, so no equipment needs to be taken out of service to perform the measurements. The antenna is compact and specially designed for safe use inside electrical switchyards. It can detect both surface and internal discharge so only one test is needed to find any sources of discharge within the switchyard. The long range of UHF allows it to perform tests without breaking the safety clearances of assets. UHF ignores corona, which is quite common in open terminal switchyards. It can also ignore other background interference by detecting noisy frequency bands and adjusting the center operating frequency to a quieter range.  UHF offers a fast all-in-one method for partial discharge testing in outdoor switchyards.

Benefits of UHF Sensor for PD Testing

UHF offers benefits in both internal and surface discharge detection. Compared to TEV, UHF does not need to make contact with the asset being tested so instead of having to place a sensor on the base of each asset a much faster sweep can be performed. TEV signals also tend to propagate between equipment, the UHF antenna will only detect the original source while TEV tests could detect PD signals on an asset adjacent to the one that is discharging. Compared to ultrasonic, UHF offers an effective range of over 100 meters in ideal conditions while an ultrasonic dish has a typical effective range of only 20 meters. UHF is also able to detect both internal and surface discharge while ultrasonic can only detect surface discharge. UHF is also able to ignore corona while ultrasonic cannot. This is because UHF is measuring in a much higher frequency range. Since the partial discharge frequency components of corona into air decay rapidly above 250 MHz any measurements performed above this frequency will not detect the signals from the corona activity.

These unique properties of UHF measurement make it the ideal choice for PD detection in outdoor switchyards.  

Checkout the UltraTEV Plus 2 (UTP2)

To learn more about UHF partial discharge testing watch this recorded webinar below “How To Use UHF”