Two of the most productive tools in a live-line inspection toolkit are infrared thermography and acoustic imaging. Infrared finds temperature anomalies – loose connections, overloaded components and hot spots. Acoustic imaging localises sound sources – partial discharge, corona and gas leaks. A handheld instrument combining both lets one inspector cover a switchgear room or substation in a single pass, with both the thermal and the acoustic picture.
What each modality detects
Infrared thermography
- Loose or corroded connections – resistively heated joints on busbars, cables and terminations.
- Overloaded equipment – components running above normal temperature.
- Abnormal component behaviour – hot spots on transformers, fuses and cable boxes.
Acoustic imaging
- Partial discharge – surface discharge, tracking and corona produce airborne ultrasound that an acoustic camera localises as a visible hotspot on the sound image.
- Corona on outdoor equipment – visible and audible discharge on insulators, bushing and overhead terminations.
- Gas leaks – pressurised gas escaping from flanges and valves generates ultrasound that can be located from a distance.
Why combining them changes the inspection
Thermal and acoustic anomalies often point to different defects in the same equipment. A connection may run hot while a nearby insulator discharges acoustically; a switchgear panel may show no thermal sign yet emit clear partial discharge ultrasound. Inspecting with one instrument that shows both images in the same pass:
- Reduces the number of site visits and the exposure time near live equipment
- Improves the completeness of the defect list for a bay
- Produces visual evidence – the image itself – that supports the maintenance report
Building the inspection workflow
- Overview sweep – walk the switchgear room or substation in thermal mode to capture the temperature picture of all panels.
- Targeted acoustic scan – switch to acoustic mode on panels, bushing, terminations and joints to pick up discharge ultrasound.
- Cross-correlate – combine thermal and acoustic findings on the same bay; anomalies confirmed in both modes are prioritised.
- Document and trend – save images with location tags and compare them on the next patrol to separate stable conditions from progressing defects.
Instrument considerations
- Dual-modality or coupled workflow – combined handhelds reduce trips; paired single-mode instruments still work with a disciplined workflow.
- Frequency range – acoustic imaging that covers the partial discharge band (roughly 20-60 kHz) detects discharge reliably.
- Reporting software – exportable images with temperature and sound level data make the inspection report credible.
About HUWOR
Zhuhai Huawang Technology Co., Ltd. (HUWOR) manufactures infrared acoustic imaging instruments and a full range of live-line detection equipment, including PD detectors, SF6 leak detectors and cable test sets. The company supports utilities, service providers and OEM/ODM partners worldwide. Contact the HUWOR sales team for demonstrations and specifications.