Partial discharge detection answers one question – is there discharge activity? – but maintenance teams need a second answer: where is it? Localisation turns a warning into a repair plan. The right localisation technique depends on the asset, because the physics of signal propagation differs completely between a GIS enclosure, a transformer tank, a cable and a switchgear panel.
Localisation by asset type
1. GIS: time-of-arrival with UHF
In GIS, UHF signals travel along the enclosure with little attenuation, so the time difference between sensors at different positions localises the source. Multiple sensors along a bay, with synchronised acquisition, place the discharge between sensor positions – often accurate to the compartment or insulator. This is the standard approach for GIS PD localisation.
2. Transformers: acoustic mapping
PD in a transformer produces acoustic emission that travels through oil to the tank wall. Mounting ultrasonic sensors at multiple tank positions and comparing arrival times and amplitudes localises the source in three dimensions – enough to direct a focused inspection or decide between repair and replacement. HFCT and electrical methods confirm activity; acoustics provide the location.
3. Cables: oscillating wave localisation
In cable PD testing with OWTS, the reflected PD pulse is measured and its distance computed from the propagation velocity – localising the defect to a cable section or joint position. The result is a PD map along the cable length, accurate enough to plan excavation or joint replacement.
4. Switchgear: panel-by-panel and multi-sensor comparison
For switchgear, localisation is typically panel-level: TEV readings per panel compared with room background, plus ultrasonic pointing to identify the compartment with discharge activity. Multi-channel systems can compare simultaneous signals across panels for better discrimination.
Multi-channel synchronised acquisition
Accurate localisation by time-of-arrival requires synchronised multi-channel acquisition – one time base across sensors. Multi-channel PD diagnosis systems provide this, supporting both GIS time-difference localisation and simultaneous multi-asset surveys in substations.
Choosing the localisation approach
- GIS bay – UHF sensors with synchronised acquisition and time-of-arrival analysis.
- Transformer – acoustic sensors on the tank, triangulated.
- Cable circuit – OWTS with reflection-based distance mapping.
- Switchgear panel – TEV panel survey plus ultrasonic compartment pointing.
From location to action
A located source supports the maintenance decision directly: a GIS compartment to inspect, a transformer region to test further, a cable joint to excavate, a switchgear panel to open. Localisation is what makes PD data actionable – and it is built into the measurement techniques rather than added afterwards.
About HUWOR
Zhuhai Huawang Technology Co., Ltd. (HUWOR) manufactures multi-channel PD diagnosis systems, UHF sensors, acoustic sensors and oscillating wave test sets that support PD source localisation across GIS, transformers, cables and switchgear, with OEM/ODM options and application guidance worldwide. Contact the HUWOR sales team for a localisation configuration.