PD for Switchgears & Transformers


Partial Discharge (PD) is an electrical phenomenon which causes insulation to deteriorate and frequently is the reason for breakdown of an insulation system resulting in failure of the equipment.

Partial Discharge can be described as an electrical pulse or discharge in a gas-filled void or on a dielectric surface of a solid or liquid insulation system. This pulse or discharge would partially bridge phase to ground insulation or phase to phase insulation in an electrical apparatus, thus causing the electrical equipment to fail.

Partial Discharges can occur for a number of different reasons. For example, PD can occur when high voltage structures have sharp projections, internal discharge can occur in voids and contact noise can occur if the ground connection to a bushing is poor.

Partial discharge in high voltage metal-clad switchgear can result in catastrophic failure of the individual plant and in some cases, of the substation (HV) plant. Conventional Partial Discharge Equipment is very expensive and difficult to use, and requires the equipment under test to be de-energised.

Through the use of modern techniques, it is now possible to detect and locate Partial Discharge with the equipment ON LINE, without the need to make direct connections to high voltage terminations, and hence, no necessity to shut down essential equipment.