The service life of the transformer depends on its insulation aging degree, and winding temperature ( Especially the hottest part of the temperature) The aging of the insulating materials. So, are equipped with large and medium-sized transformer winding temperature monitoring device, namely the transformer winding thermometer. Transformer winding heat is produced by the load loss in the transformer. By P = I squared r load loss formula, the winding of fever and is proportional to the square of the current transformer. Because the transformer winding is immersed in the insulating oil, therefore, winding thermometer is on the basis of an oil temperature gauge, equipped with a current matcher, and an electric heating element, its principle diagram is shown below. The sensor of the thermometer which bulb in transformer oil tank top hole. When the transformer load is zero, winding is not hot, so the thermometer readings for transformer oil temperature; After the transformer on load, through current transformer output is proportional to the load current, the current matcher adjusted through the electric heating element embedded in the corrugated tube, the electric heating element fever. The heat generated by the electric heating element, the displacement in the elastic element increase. As a result of the elastic element displacement is determined by the transformer top oil mildly transformer load current, so in the design of winding temperature time, considering the current flows through the electric heating element ( The matcher secondary current) Produced by temperature indicating increment, it is akin to transformer winding temperature rise of oil to be tested. In this way, the temperature of the winding thermometer indicator is the transformer top oil temperature of oil and winding temperature rise, the sum of it reflects the hottest part of the transformer winding temperature being measured. Thermometer the oil hole in the shell welding in transformer tank top, and the transformer oil system is to isolate, but the heat conduction. When used in thermometer filled with thermal oil first insert the bulb, and then take out the bulb, pump small amount after the thermal oil ( Ensure all bulb stem long 95% can dip in oil) , and then back into the bulb and screw fixation. The purpose is to make a thermometer of the thermal oil expansion space, and guarantee of the thermometer good heat conduction, ensure accurate temperature measurement. In addition, the verifier is a kind of current commutation device, its role is to provide power for winding thermometer. The electric principle consists of current transformer input current, the current matcher after transformation, the winding thermometer inside the electric heating element provides an adjustable current, so as to achieve the purpose of simulating the hottest part of the temperature of transformer winding. Current verifier can be rough adjustment ( Adjust the K line end, namely changes) And fine tune ( Adjust potentiometer W, the diversion ratio with electric heating element) 。 In measurement of a complete set of equipment, electric heating element is the core of the equipment components, heating characteristics of because it can truly reflect the heating characteristics of transformer winding will directly affect the measurement result.