Real-time visualisation of capacitive and depolarisation discharge after DC insulation testing for improved safety, accuracy, and productivity

DC insulation resistance (IR) testing is widely used in the high-voltage (HV) industry. There are inherent safety implications and test standards such as IEEE 43, IEEE 95, and IEEE C57.152 specify discharge procedures, but with rather vague wording (e.g. “until the absorbed charge is completely dissipated” – but not defining “completely”), and if the only simplistic method is to leave the discharging/grounding/earthing wire connected for a long time, then this can reduce productivity, and lead to dubious unsafe actions (IEEE 62.2: “absence of voltage shall be confirmed with the test specimen ungrounded”). Shorter discharge can affect accuracy of the next test. Improvement of the quantification of discharge processes is long overdue in the HV industry. Theoretical and laboratory procedures are used for research purposes, but an industrial solution is still missing. To rectify this shortcoming, we propose a reliable solution, which is sound from the safety viewpoint as well as metrologically consistent. The proposed technique was already tested on real HV assets and thus already proven to work reliably in the field. The experimental users found it intuitive to use, seeing the direct impact on their safety / accuracy / productivity, as well as having an educational outcome of the involved physics behind the processes of discharge of capacitance and discharge of depolarisation currents (dual discharge).