Power transformers play a critical role in power generation systems, and ensuring their reliable operation is essential for uninterrupted power delivery.

The insulation system of transformers is subjected to various stresses over time, leading to normal deterioration. This gradual process may result in localized weak areas with reduced dielectric strength, leading to partial discharge (PD) activity. Partial discharge is the occurrence of small electrical sparks within the insulation system, indicating potential problems caused by thermal, mechanical, electrical, environmental, and chemical processes. Detecting and monitoring PD through non-destructive methods, such as PD measurement, can help identify local defects in the insulation system and ensure the reliability of electrical equipment.

Understanding the causes and types of partial discharge is crucial in maintaining the integrity of transformers. PD can be categorized into corona-type and sparking-type discharges, occurring in different mediums such as oil and paper insulation. Defects such as delamination, voids, bubbles, metallic particles, moisture, bad connections, static electrification, and surface tracking can generate partial discharge in transformers. Identifying these defects through diagnostic measurements, both in the laboratory and on-site, allows for early recognition of insulation degradation, detection of incipient faults, and optimization of maintenance strategies.

The on-site testing of partial discharge poses challenges due to background noise from other equipment in proximity to the test object. Accurate and repeatable determination of partial discharge is essential, necessitating the use of consistent equipment for consecutive tests on the same unit. Establishing baseline parameters through initial PD testing after commissioning is crucial for reference and future monitoring. Further exploration of test methods and interpretation of partial discharge data is needed, emphasizing the delicate nature of on-site PD testing and the importance of reliable reference data.

To delve deeper into the complex world of partial discharge in transformers, we invite readers to explore the full paper by expert transformer consultant Corne Dames in the May edition of our magazine.