Partial Discharge (PD) Surveys are crucial for network operators to minimise the risk of erosion in insulation failure resistance in transformers, switchgear, generators, and other electrical equipment. But monitoring assets for PD isn’t straightforward: there are a number of factors that can interact including issues with site practices at installation for example. In addition, if the fault falls below certain levels it may not flag any actions.
Non-invasive, accurate online partial discharge (PD) surveys in MV and HV substations therefore are key and being able to measure PD activity at frequencies above those of common disturbances is crucial for substation management. Accurate and dependable results can be delivered for a wide range of assets, including cable-end terminations, surge arrestors, voltage transformers and isolators.
In this regard dual-channel capability that allows for direct comparison of the results obtained from two types of UHF sensors or from two phases ensures the most comprehensive measurements. It is also beneficial for solutions to include functionality that has in addition to its primary UHF functionality, RF PD measurements.
High bandwidth operation at UHF, in conjunction with phase resolved partial discharge (PRPD) pattern display facilities enables discrimination between different types of defect. This is an important benefit as it means, for example, that corona and surface discharges can be readily distinguished from dangerous internal partial discharge events that suggest a need for immediate further investigation.
Megger’s UHF Partial Discharge Detector offers this kind of functionality and in is supplied with a dipole antenna for UHF surveying. Inductive (HFCT) and capacitive (TEV) sensors for making measurements on MV cables and switchgear are available as optional extras. A UHF PD coupling sensor can also be supplied, so the instrument can be used to carry out detailed and precise measurements on HV components such as terminations. As an additional benefit, this sensor is suitable for systems rated at up to 500 kV.