Partial discharge measurements only have meaning if they are comparable – this year’s reading against last year’s, one switchgear panel against its neighbour, one engineer’s survey against the next. That comparability rests on calibration. A PD detector that drifts out of calibration produces confident-looking numbers that quietly lose their value, and trend-based maintenance – the whole point of the programme – silently degrades.
Why calibration matters
Comparability across time
Predictive maintenance alarms on change. If the instrument’s gain or measurement chain drifts, a rise in readings may be the instrument, not the asset – triggering false alarms or masking real trends.
Comparability across instruments
Utilities running several detectors, or contractors comparing survey results, need measurements to mean the same thing on every instrument.
Defensible records
Where PD data feeds maintenance decisions or handover records, a documented calibration state supports the credibility of the record.
What calibration covers
- Sensor verification – the sensor’s response is checked against a known reference.
- Measurement chain – amplifier gain, filtering and display accuracy are verified across the instrument’s range.
- Battery and hardware state – checked so calibration holds under field conditions.
- Certificate and traceability – each calibration produces a record linking the instrument to a reference standard.
Practical calibration schedules
- Annual calibration – the common interval for PD detectors in regular use, aligned with the utility’s inspection calendar.
- After repair or impact – any event that could affect the measurement chain triggers a re-check.
- Before critical campaigns – a verification pass before a major survey programme protects the campaign’s data quality.
What to require from your supplier
- Defined calibration procedure – the manufacturer documents how calibration is performed and what it verifies.
- Calibration support options – return-to-factory service, or locally available calibration for utilities that need it in-region.
- Clear calibration indicators – self-test or calibration-due indication on the instrument, so drift is caught early.
- Documentation – calibration instructions in the manual, with records kept per instrument.
Calibration as part of the programme
Fold calibration into the maintenance plan: each instrument has a calibration due date in the register, and the annual calibration cycle runs alongside the inspection cycle. The cost is small; the value is that every reading in the database means the same thing.
About HUWOR
Zhuhai Huawang Technology Co., Ltd. (HUWOR) manufactures PD detection instruments with defined calibration procedures, self-test capability and calibration support, supplied worldwide with OEM/ODM options and application guidance. Contact the HUWOR sales team for calibration arrangements for your instruments.