PartialDischargeMessungen

Partial discharge (PD) is a localized, brief electrical breakdown within an insulation system that does not bridge the gap between conductors. It typically occurs in gas-filled voids, cavities, or along interfaces inside solid insulation or at conductor-insulation boundaries under high-voltage stress. PD can be internal, occurring within voids or inclusions, or surface-related, occurring along the insulation surface under contamination or moisture.

PD arises when the local electric field exceeds the dielectric strength of the air or gas in a defect, causing a short-lived discharge that emits pulses of current, light, heat, and chemical byproducts. Repeated PD can lead to progressive insulation deterioration, erosion of material, moisture ingress, chemical aging, and, if unchecked, eventual complete breakdown of the insulation.

Detection and assessment of partial discharge rely on non-destructive testing and condition monitoring. PD activity is typically measured as pulse sequences in time and frequency domains using specialized sensors and recording equipment. The IEC 60270 standard defines methods for measuring apparent discharge and PD magnitude under applied voltage. Additional techniques include acoustic emission, ultrasonic sensing, and ultrahigh-frequency (UHF) sensing, which can aid localization and severity assessment.

Applications include quality control during manufacturing, and condition monitoring of high-voltage equipment such as transformers, cable systems, switchgear, and bushings. Interpretation of PD patterns helps distinguish defect types and estimate remaining insulation life. Mitigation focuses on eliminating voids, improving impregnation and moisture control, proper aging management, and targeted maintenance based on PD monitoring results.