Welcome toThe Partial Discharge Academy

Partial Discharge Detection

Partial Discharge activity is detectable as:
  • Electromagnetic emissions, in the form of radio waves, light and heat
  • Acoustic emissions, in the audible and ultrasonic ranges
  • Ozone and oxide of nitrogen gases
The latest Partial Discharge detection instruments use a combination of the sensors below, to ensure accuracy.

The most accurate and reliable techniques used for detecting and measuring Partial Discharge activity are:

Ultrasonic Sensors

These measure Partial Discharge activity in the form of ultrasonic emissions. They are particularly effective at measuring surface PD activity.

Transient Earth Voltage (TEV) Sensors

These measure Partial Discharge activity in the form of electromagnetic emissions and are principally used to measure PD activity inside enclosures.

Ultra High Frequency (UHF) Sensors

These measure Partial Discharge activity in the form of UHF radio waves. They are particularly effective at measuring internal PD activity, including discharges in gas insulated assets.

Detection of PD-related faults is based on the principle of determining whether Partial Discharge activity it is at a critical level.

Low levels of Partial Discharge activity are often present in assets at levels which may be considered acceptable i.e. non-critical, or unlikely to develop into failures in the short to medium term.

PD Fault Detection
Partial Discharge-related faults can be detected using simple, handheld instruments, or fixed sensors



Faults are often detected by testing to establish whether Partial Discharge activity exceeds critical thresholds:

LEVEL 1

Partial Discharge activity is not present or at sub-critical levels. Results provide assurance that PD-related faults are unlikely to be developing at present.

LEVEL 2

Partial Discharge activity is at a level which indicates that a fault is developing and requires further investigation or monitoring.

LEVEL 3

Partial Discharge activity is at a level which indicates that a fault is at an advanced stage of development. The fault is likely to cause imminent failure – and the asset may be energised to an extent that is a danger to personnel. This level of Partial Discharge activity indicates the need for immediate investigation and intervention.

Fault Prediction & Prevention

The prediction and prevention of faults is based on the principle that, once present, damage resulting Partial Discharge activity inevitably increases.

Measuring and plotting changes in Partial Discharge activity make it possible to predict with a high degree of accuracy when a fault is likely to develop into a failure. Managers can therefore take appropriate and timely action to rectify faults, as they develop and before they lead to outages.

The ability to predict the way in which Partial Discharge related faults develop is greatly enhanced by knowledge of how specific assets behave, once the process of deterioration has begun.

To obtain the most accurate predictions of failure requires:

  • Specialised Partial Discharge measurement instruments
  • The knowledge to interpret readings
  • An extensive database containing details of how specific assets deteriorate over time, in particular applications and environments