Electrocapacitive Air Gap Sensor With Parallel Coplanar Electrodes for Hydrogenerators Condition Monitoring Systems

In this paper proposed and investigated a capacitive sensor with parallel coplanar electrodes systems for measuring the air gap between the stator core bore and the rotor poles in a powerful hydroelectric generator. Air gap control is one of the key elements in condition monitoring hydrogenerators. Air gap sensor consists of a system of strip parallel coplanar high-potential and low-potential electrodes of equal width, between which grounded electrodes are placed. The electrodes that formed on a dielectric substrate. To reduce the impact of edge effects on the short sides of the high-potential electrodes, the length of the low-potential electrodes is chosen to be smaller than the length of the high-potential electrodes by an amount. The electrical capacity between the system of parallel-connected high-potential electrodes and the system of parallel-connected low-potential electrodes, which functionally depends on the size of the air gap, is measured. The conversion function of the sensor was determined analytically and with the help of crankcase modeling. A sample of the sensor intended for use on a capsule hydroelectric generator type SGK538/160-70M was obtained. Compared to analogues, the sensor has a higher measurement accuracy. A sensor or a system of sensors as part of a component for condition monitoring and diagnostic systems.