How to detect the state of trace moisture in transformer oil

Power transformer is not only one of the most important and expensive equipment in power system, but also one of the equipment that causes the most accidents in power system. Before the sudden fault of transformer occurs, the deterioration of insulation and latent fault will produce a series of effects and information such as light, electricity, sound, heat and chemical changes under the action of operating voltage. Therefore, both at home and abroad should not only do preventive maintenance based on preventive tests on a regular basis, but also have been studying predictive maintenance strategies based on online monitoring, so as to monitor and diagnose latent faults or defects online in real time or at regular intervals.

The evaluation of humidity in insulating materials is an important factor to ensure the reliability and service life of transformers.
The relative saturation of water in insulating oil needs to be standardized, because the humidity in insulating oil is closely related to the temperature change, and there is a certain temperature gradient in the transformer main box (usually the top temperature of the box is higher than the bottom temperature). To complete the standardization, the expert system analysis needs to infer the relative saturation percentage of the bottom. It can be obtained by using the temperature reported by the sensor and its sampling location.
This analysis assumes that the top temperature of the transformer is 10 ℃ higher than the bottom temperature. If a position other than the top or bottom is used as the sampling point, the temperature deviation must be specified. Through the relative saturation of humidity and the specific measurement temperature, the expert system will use a certain percentage of relative saturation as the calculation result of the insulation paper humidity. It must be noted that this calculation is only based on the results of a single measurement, and may not reflect the true humidity concentration of the insulating paper, especially after the transformer has just experienced severe temperature changes.