Design and fabrication of humidity sensor for condition monitoring of breather of transformer

摘要

Due to the cyclic loading of the transformer the ambient air flow through the conventional dehydrating breather. Ambient air contains moisture and due to the poor conditions of the breather, it leads to deteriorate the insulation life of the transformer. In the proposed work, a capacitive parallel plate relative humidity sensor for monitoring moisture inside the breather has been designed. The sensing film between the parallel plates of the sensor is of porous hexagonal ordered structure. It was grown through the anodization of aluminium (Al) by electrochemical fabrication method. Moisture inside the breather was monitored with the help of designed sensor. A phase detection electronics circuit for converting the capacitor change of sensor into the voltage signal was designed. The designed sensor was used in estimating the dehydrating efficiency of 0.5 kg breather used in < 200 kVA transformer for the duration of 44 days. During this period, the steady state response of the moisture inside the breather was also analyzed. With the help of designed sensor and phase detection electronics circuit, the condition monitoring of the breather of the transformer will be possible and reduces the visual inspections of the degree of moisture inside the breather.