Conventional UHF partial discharge monitoring requires a direct coupling point: a dielectric window on a GIS compartment or a built-in port. But much of the world’s switchgear – distribution panels, ring main units and medium-voltage switchboards – has no such port, and opening the enclosure to add one is not practical for retrofit projects. The spatial UHF method solves this by monitoring the UHF signal that leaks into the space around the equipment. This article explains spatial UHF monitoring and the HUWOR HMJ1010-WGK.
What spatial UHF monitoring does
A discharge inside a switchgear panel produces an electromagnetic wave. Some of that wave escapes through gaps, cable entries, vents and non-metallic parts of the enclosure and radiates into the surrounding room. A spatial UHF sensor – installed on the wall of the switchgear room, on a stand, or on the surface of the equipment – picks up this radiated signal.
The advantage of the spatial approach is that it detects internal discharge without any modification of the switchgear: no panel needs to be opened, no dielectric window is required, and the installation is done while the equipment remains energised. The sensor measures the ultra-high-frequency band, which suppresses most of the low-frequency electrical noise in the room.
The HMJ1010-WGK at a glance
The HUWOR HMJ1010-WGK is an intelligent spatial UHF partial discharge sensor designed to monitor UHF PD signals within specific environments such as high-voltage distribution rooms and ring main units. According to the published specification, the frequency range is 300-1500 MHz, the standard UHF band used for PD detection. The sensor is typically installed on the room wall or on the equipment surface and connects to the online monitoring platform.
Because a spatial sensor observes a volume rather than a single compartment, it is best applied where the equipment is enclosed and the discharge source is within a few metres of the sensor. For a room of RMUs or a row of panels, one or two spatial sensors can provide area-level coverage that complements per-panel sensors.
How spatial UHF fits a monitoring architecture
A complete switchgear room monitoring solution often combines three layers:
- Per-panel sensors (TEV or combined TEV/ultrasonic) for individual panel trending
- Spatial UHF sensors for area-level detection of internal discharge that TEV may miss
- A multi-channel unit to acquire all signals and present them on one platform
The spatial UHF layer adds a detection method that is independent of the panel earthing path, so a discharge that is electrically quiet on the TEV path is still caught by the radiated UHF signal.
Using spatial UHF in practice
In a distribution substation with several RMUs, the spatial sensor is positioned to see the whole bay. When the platform reports activity, the operator uses a handheld detector to localise the source inside the bay, then schedules the maintenance. In a GIS building where external UHF sensors are fitted to the compartments, a spatial sensor at the room level adds a check on the parts of the installation that have no direct coupling point.
Summary
Spatial UHF monitoring brings UHF sensitivity to equipment that has no internal port, detecting the radiated 300-1500 MHz PD signal within switchgear rooms and RMU bays without any modification of the panels. The HMJ1010-WGK provides this capability as a surface or stand-mounted sensor feeding the monitoring platform. HUWOR supplies the sensor with OEM/ODM support. Contact the HUWOR sales team for a room-level monitoring layout.