Partial Discharge (PD) testing and monitoring for oil filled and dry type transformers

On-line PD Testing and Monitoring of Transformers

Partial Discharges can occur at various points in transformer insulation. In oil filled transformers, sources of PD include gas bubbles in oil, voids or gaps in paper or pressboard insulation, in addition to PD in bushings and tap-changers. In dry type transformers, sources of PD include voids in insulation and surface tracking. By PD testing and monitoring, the development of underlying defects can be detected and insulation condition assessed.


High frequency current transformers (HFCT) attached to the power cables. and transient earth voltage (TEV) sensors attached to metal-clad housing. Bushing tap sensors can be attached to voltage or test taps points.

Test Equipment

In-depth diagnostic spot testing on in-service assets using the HVPD Kronos® Spot Tester using portable or pre-installed sensors.

Monitoring Systems

Continuous monitoring of complete electrical networks using our HVPD Kronos® On-line PD Monitoring System.

Test Services

Comprehensive range of test services for on-line and off-line condition assessment, including offline turnaround service and reactivation services.