Rated operation mode of transformer

1. When the voltage of the transformer is lower than the rated voltage of the transformer, it has no great influence on the transformer, only reduces the output of the transformer, the increase of transformer core loss and reactive power loss has an effect on transformer insulation. Voltage deviation of 0.5% . When the primary voltage of the transformer is within 5% of the rated taxi, the secondary side can be operated with rated power. 2, the heating and cooling of the transformer, the loss of electric energy in the winding and the iron core are all converted into heat, which makes the temperature of each part of the transformer rise, and the temperature rise of each part is not uniform. Heat transfer process: Heat from the winding and iron core to the transformer oil, the heat of the hot oil through the radiator to the surrounding air. The characteristics of the heat dissipation process: The heat generated by the iron core, high-voltage winding and low-voltage winding are all transferred to the oil; during the whole heat dissipation process, the temperature difference of each part is large, and the temperature of the winding is the highest; Forced oil circulation air-cooling or forced oil circulation water-cooling, more capacity of guided cooling, in the high and low pressure winding inside the set of a certain oil, can greatly improve the heat dissipation efficiency.

　　3. The transformer's allowable temperature and temperature rise, the transformer's allowable temperature depends on the insulation material. Oil-immersed transformers are paper and oil-insulated. When the highest temperature of transformer winding is 98 °c, the useful life is 20-30 years. In actual operation, the highest temperature of winding is less than 98 °C, and the service life of transformer can exceed 30 years. When the transformer is running, the temperature of winding and top layer oil should be monitored. Transformer overtemperature protection configuration, over the low temperature setting alarm signal, when the temperature over the high temperature setting trip. 4, transformer overload capacity, transformer normal operation, the daily load curve load rate is less than 1. According to the principle of equivalent aging, the specified service life of transformer can be obtained as long as the life of over-loss and the life of under-loss can be compensated each other. The normal overload capacity of transformer is based on the principle of not sacrificing normal life. The following conditions are satisfied: (1) during the overload period, the temperature at the hottest point of the winding shall not exceed 140 °C, and the oil temperature in the upper layer shall not exceed 95 °c; (2) the maximum overload of the transformer shall not exceed 50% of the rated load when the system fails, the first task is to try to ensure uninterrupted power supply, while the aging of the transformer insulation is secondary, the accident overload is at the expense of the life of the transformer. The insulation aging rate is allowed to be much higher than under normal overload. Accident Overload also known as first aid load, is in a shorter period of time, so that the transformer with some more load, for urgent use. In order to ensure the reliability, when the allowable value of the transformer accident overload is determined, the temperature at the hottest point of the winding should not exceed 140 °C and the load current should not exceed twice the rated value.