Measuring moisture content in power transformers: hydro-Québec uses online monitoring sensors to evaluate condition of power transformers

摘要

Along-standing principle for ensuring insulation reliability is to maintain a clean, non-contaminated environment within the insulating system. For insulated cable, manufacturers strive to produce insulations that are homogeneous and free of voids and foreign materials. For the insulation system within a transformer, it is important to provide oils that are free of moisture and gases. Traditionally, utilities have assessed the dryness of inservice transformers by taking periodic measurements of water content in the oil. By inference, the collected information can help estimate the moisture content in the insulating paper of the windings. Excessive moisture significantly reduces not only the dielectric strength, but also the partial discharge inception level. Moisture also effects the generation of gas bubbles at high temperatures, which creates a significant threat to the dielectric integrity of the insulation structure.