High Voltage Testing & Commissioning

Partial Discharge Analysis

Partial Discharge Analysis on Rotating Machines

Partial discharge (PD) occurs in the stator insulation system of rotating machines, where local electric field stress exceeds the local electrical strength. Compared with other dielectric tests, the differentiating character of partial discharge measurements allows localized weak points of the insulation to be identified.

PD measurements based on IEC 60034-27 standards can be performed on motors and generators either on-line during regular load service operation or off-line by energizing each winding successively during standstill of the machine.

Generally, several different partial discharge sources are present and active within the stator winding insulation at the same time. The key to successful PD measuring in stator windings is the separation of parallel active PD sources and the distinction between harmful PD, normal PD occurrences and outer noise, inevitably present in industrial surroundings.

This is best achieved by synchronous, multi-channel partial discharge measurement. This separates internal PD sources from each other and from noise signals.  PD sources are evaluated individually within the stator winding.

Partial Discharge Analysis on Power Transformers

Partial discharges (PD), as defined by IEC 60270, are localized dielectric discharges in a partial area of a solid or liquid electrical dielectric insulation system under high-voltage field stress. Partial discharges in a transformer deteriorate its insulation and can lead to failure of the transformer.

Diagnostic PD measurements are recommended after conspicuous measured values, such as increased gas-in-oil values or after a failed PD measurement during acceptance tests.

With our testing systems, you can detect partial discharges already in their early stages or determine their source locations acoustically. This allows you to draw conclusions regarding the condition of the insulation. At the same time, further measures such as repair or additional diagnostic measurements can be initiated.