1. The role of the transformer temperature controller
Nowadays, there are mainly two kinds of power transformers: oil-immersed transformer and dry-type transformer. Dry type transformers are widely used in power plants, power stations, substations, airports, railways, intelligent buildings, intelligent residential areas and other places because of their safety, fire resistance, no pollution, no maintenance, low loss, small release, long life and many other advantages. An outstanding advantage of three phase dry-type transformers is that their design life is generally more than 20 years, and the longer the life of the transformer, the lower its comprehensive cost. In fact, the safe operation and service life of the dry transformer largely depend on the safety and reliability of the transformer winding, and the winding temperature exceeds the insulation resistance temperature so that the insulation damage is one of the main reasons that the transformer can not work normally. Moreover, the service life of dry transformers generally ends because of the expiration of the "thermal life". In order to ensure the operation life of dry-type transformer, it is necessary to use temperature control system to monitor the temperature of transformer winding, and timely protection such as forced refrigeration or early warning.
2. Type of transformer temperature controller
2.1 Mechanical and electronic temperature measurement: mechanical temperature controller is generally an expansion temperature controller, which uses the oil packet as the sensing head and uses the principle of thermal expansion and contraction as the temperature measurement. Due to the large volume of the oil envelope, the installation is not convenient, so it is generally only used in oil-immersed transformers. Electronic thermostats generally use thermal resistors (such as Pt100, PTC, etc.) or thermocouples and other temperature measuring elements as sensors. Electronic thermostat is widely used in oil-immersed and dry-type transformers because of its high technology content, complete functions, high precision and easy operation.
2.2. From the installation method, it is divided into embedded and external: the embedded thermostat is generally installed directly on the transformer clamp (without shell products) or embedded in the transformer shell; The external thermostat is mounted on the wall (without housing products) or installed on the outer surface of the transformer housing. Because the dry transformer will produce a lot of heat, low frequency vibration and electromagnetic interference during operation, it has a great impact on the embedded thermostat installed on the clamp or embedded in the housing. It is well known that electronic components and dry transformers have a "thermal life", and this installation method greatly reduces the service life and reliability of the terperature control. The external thermostat is well protected because it is isolated from the environment.
