What is Partial Discharge?

Partial Discharge (PD) is a small electrical discharge or spark within MV or HV insulation which gradually erodes the insulation. In time this erosion can lead to a “bridge” forming in the insulation, leading to a flashover. Partial discharge can affect most high voltage asset types including:

  • Cables and splices
  • transformers
  • bushings
  • switchgear
  • motors and generators.

At Megavar we have seen firsthand the damage that partial discharge (PD) can cause to HV assets. Partial Discharge Testing of electrical assets is a vitally important part of condition monitoring programs. Because partial discharge often occurs before the insulation fails, we can monitor it over time and assist our clients to make informed decisions about repairing or replacing equipment. Predictive diagnostics help our clients prioritise capital investments before unexpected outages occur.

What is Offline Testing?

Offline PD testing is performed with the equipment taken out of service and energised with a test voltage source (Hipot). The PD detection equipment is coupled to the Device Under Test (DUT) and has the advantage of being able to analyse the DUT at different stress levels. It enables the engineer to remove external noise sources, as the DUT is isolated from the network during the test, meaning that PD activity can be localised.

Our engineers are trained in the use of the Omicron MCC210 and MPD 600 to perform efficient regular inspections of all asset classes, including:

  • instrument transformers
  • bushings
  • Transformers
  • Cables
  • Air insulated switchgear
  • Vacuum switchgear
  • Gas-insulated switchgear
  • rotating machines.