The safe operation and service life of dry-type transformer largely depends on the safety and reliability of transformer winding insulation. It is one of the main reasons that the transformer can not work normally because the winding temperature exceeds the insulation tolerance temperature, so it is very important to monitor and alarm the operation temperature of the transformer.

(1) Fan automatic control: temperature signal is measured by Pt100 thermistor embedded in the hottest part of low-voltage winding. With the increase of transformer load and operation temperature, when the winding temperature reaches 110 C, the system automatically starts the fan cooling; when the winding temperature is low to 90 C, the system automatically stops the fan.

(2) Overtemperature alarm and tripping: The temperature signals of windings or cores are collected by PTC non-linear thermosensitive resistance embedded in low voltage windings. When the temperature of transformer winding continues to rise, if the temperature reaches 155 C, the system outputs the overtemperature alarm signal; if the temperature continues to rise to 170 C, the transformer can not continue to operate, it is necessary to transmit the overtemperature trip signal to the secondary protection circuit, which should make the transformer trip quickly.

(3) Temperature display system: The temperature change value is measured by Pt100 thermistor embedded in low-voltage winding, and the temperature of each phase winding is displayed directly (three-phase inspection and maximum value display, and record the historical maximum temperature). The maximum temperature can be output by 4-20 mA analog quantity. If it needs to be transmitted to a remote computer (distance can reach 1200 m), it can be equipped with a computer interface and a transmitter, at most. At the same time, 31 transformers are monitored. The over-temperature alarm and trip of the system can also be operated by Pt100 thermistor signal, which further improves the reliability of the temperature control and protection system.