Partial Discharge Surveys | EA Technology
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Partial Discharge Surveys

Knowing and understanding the condition of your power assets is vital in controlling the risks presented to your business, allowing your asset managers to plan and schedule your maintenance programme around actual asset condition rather than presumptions and set time intervals.

EA Technology’s Partial Discharge (PD) surveys are available worldwide, using our market-leading instruments. They are conducted by qualified personnel, who are expert at analysing the results to provide you with valuable reports on the condition of your assets. Our experts will provide you with an easy to understand, ‘traffic light’ status report which contains clear recommendations for managing your power assets based on their condition.

Why measure PD activity?

Put simply: Because 85% of disruptive substation failures are PD related. Once you have PD present, it will always increase and if left will inevitably cause a failure which may be sudden and catastrophic. PD is the most reliable indicator of the condition of insulation within live assets.


  • Prevent PD-related defects developing into failures and outages
  • Collect valuable information on the health of assets and risks of them failing
  • Enhance planning of maintenance and replacements, based on measured condition
  • Improve network safety and reliability
  • All testing is non-intrusive
  • Comply with Health and Safety Executive’s HSG 230 (Health and Safety Guidelines Keeping Electrical Switchgear Safe)


  • Use of the latest instruments for detecting, measuring, locating, monitoring, recording and analysing PD activity
  • Expert engineers, backed by EA Technology’s 50+ years expertise in PD
  • Clear reports and recommendations on how to use PD survey results
  • Instruments measure Ultrasonic activity, Transient Earth Voltages (TEVs) and in some cases Radio Frequency (RF) emissions
  • Reliable, independent reporting using our database of 20,000+ test results to give you the most accurate conclusions

Scope of PD Surveys

PD surveys can be carried out on indoor metal clad switchgear, most types of outdoor switchgear and the cable termination boxes of transformers. Other methods must be utilised to detect PD in cables or the windings of transformers/motors, but EA Technology can also provide these services in many cases if so desired. PD surveys can be delivered as part of a larger package of condition assessment measures, such as oil sampling of transformers for dissolved gas analysis purposes and trip profiling of circuit breakers.

Handheld instrument surveys

Using instruments manufactured by EA Technology, we can detect partial discharge activity via the emissions of ultrasound, TEV and/or RF associated with the phenomena. This service provides a snapshot of an asset’s condition at a point in time, and has been used to great effect in reducing catastrophic failures and network outages by customers all over the world for more than 20 years. Our technical staff attend site and complete the survey on the desired part of your network. Later they will provide a detailed written report of the results, the conclusions that can be drawn and our recommendations on how to address issues or manage the assets.

Temporary installations of monitoring equipment

Where issues have been identified during a handheld survey, where intermittent PD activity is suspected or if an asset is of a critical nature, the use of a monitoring system that is installed for a short period (typically 1-2 weeks) may be advised. The UltraTEV Monitor™ continuously measures and records PD activity (both TEV and ultrasonic) and allows detailed analysis of the data. Ambient temperature and relative humidity are also recorded, as these can strongly influence the level of surface discharge activity if it is present. Finally, this method can also be used where there are high levels of radio frequency background interference (caused by variable speed drives, uninterruptable power supplies, etc.) to differentiate between noise and discharge.

Specialist survey work

If corona activity is suspected on components such as arching horns, we can deploy a Corona Camera. This instrument captures the ultra violet light emitted by corona activity and overlays it onto an image in the visible spectrum. It is also possible for us to measure partial discharge directly by energising a component’s phase conductors using a low-current test supply and applying special test equipment. However, this is in a laboratory environment and requires the equipment to be transported to our site in Capenhurst, UK: such an approach is only suitable in rare circumstances.

We can also provide a custom solution to help in diagnosing a problem and provide advice on how best to proceed; this is often a combination of several of our products and services backed up by our experience in consultancy.

David Harding
Business Development Manger

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