Laboratory Testing of a Sensor for Hydrogen Dissolved in Transformer Oil

A new device based on the electrochemical oxidation of hydrogen diffusing through a Teflon(R) membrane has been tested over a range of conditions in the laboratory. The device is aimed at measuring the hydrogen content of transformer oil in situ and on a continuous basis. The sensor consists of a metallic body screwed directly on the transformer in an appropriate opening and a second removable metallic casing that includes the electrochemical cell. This device was temperature cycled from -30 to 70°C. The diffusion of hydrogen from the bulk of the oil to the membrane is the slowest step and determines the resulting signal. Agitation of the oil is an important factor in the operation of the sensor; thermally induced convection as present in operating equipment is sufficient to improve the behavior of the sensor. A temperature compensating circuit was devised to eliminate the thermal factor from the observed signal; the results with this compensating circuit are presented.