Partial Discharge (PD) Testing Services
Ensure the reliability of your HV assets
Partial Discharge: An Early Warning
Partial Discharge (PD) typically arises from imperfections or discontinuities in the insulation material such as voids, cracks, or delamination. PD is widely recognised as the most effective early-warning indicator of insulation degradation in HV and MV electrical assets. It signals the onset of incipient faults well before they develop into critical failures.
Although PD is initiated by electrical stress, its behaviour is also influenced by other operating and environmental factors such as load, temperature, humidity, and contamination. Because PD often precedes insulation failure, implementing a testing regiment enables asset managers to make informed, strategic decisions.
By understanding PD trends, organisations can:
Effective PD detection and analysis allows operators to shift from reactive to predictive asset management - extending asset life, enhancing reliability, and optimising budget allocation.
On-line PD testing is a non-intrusive diagnostic technique that evaluates insulation condition while equipment remains energised and in service. It enables detection of partial discharge activity under actual operational stresses such as voltage, temperature, humidity, and load, providing a realistic view of asset health.
By using pre-installed sensors or permanently installing sensors such as HFCTs and HVCCs, testing can be carried out without the need for an outage. With a sensor installation, online PD testing is ideal for routine spot checks across critical assets, especially where downtime is costly or logistically challenging.
Offline PD testing is performed with the equipment de-energised, typically during planned outages, commissioning, or factory acceptance testing. In this controlled environment, test voltages are applied and partial discharge inception and extinction values are measured. These parameters can be trended over time.
These tests are highly sensitive and repeatable, offering a detailed understanding of insulation performance. They are useful for detecting latent defects before energisation and assessing asset condition during scheduled maintenance.
PRPD patterns can be used to diagnose the type of insulation defect, for example for rotating machines assets, voids, delamination, slot, gap type discharges can be identified. This specificity allows maintenance activities to be targeted. This unlocks value from a condition-based maintenance program.
Monitra offer a full suite of offline testing for all MV & HV assets types conducted to the relevant industry standards including IEC 60270 and IEEE 43. These measurements are complimentary to PD testing:
PD testing can detect insulation defects in rotating machines, transformers, cables, switchgear
Monitra delivers a full suite of PD testing services, encompassing both online and offline methods. Our Kronos Spot Tester (KST) diagnostic test unit is flexible and can be used for substation testing, diagnostics and factory quality assurance. Compatible with a wide range of sensors including pre-installs, multi-asset testing can be performed with a single device.
Testing is tailored to your operational needs, whether as part of a commissioning process, during scheduled shutdowns, or as a periodic check on critical infrastructure. Our team interprets results in line with IEC 60270 and other relevant standards, providing clear, practical insight to guide maintenance strategies.
Working with Monitra helps you detect developing issues early, reduce the risk of unplanned failures, and make better-informed decisions about asset maintenance and replacement. Our approach supports condition-based maintenance programmes, helping extend asset life and optimise investment planning.
