Temperature standard for dry-type transformers - How many degrees does the working temperature of the three-phase 10kV coil trip

Standard for three-phase temperature of dry-type transformers

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What is the normal temperature difference between the three phases of a dry-type transformer?

Due to the radiation heat transfer between phase B and phases A and C, and the relatively high temperature of phases A and C themselves, the temperature of phase B after radiation heat transfer is definitely higher. To prove this point, 1. Thermal calculation software such as ANSYS shows that the temperature of phase B is higher than that of phase A, and the temperature of phase C is about 10K; 2. Actual measurements, such as using an infrared temperature measuring instrument to scan the surface temperature of the winding, indicate that the temperature of phase B is higher than that of phase A, and the temperature of phase C is about 10K.

1. Dry transformation is not like oil transformation. Its heat dissipation medium is the surrounding air (the temperature field of oil transformation in the oil tank is relatively uniform). The air itself is greatly affected by the temperature of the transformer coil, and the temperature difference between coils is larger than that of oil transformation.

2. If it is a three-phase load balancing situation (you are a rectifier transformer, the three-phase load should be basically balanced). The temperature of the intermediate phase (B phase) is about 3-5 degrees higher than that of the other two phases. If the ventilation is not very good, there will be more.

3. If there is a difference of 20 degrees in basic three-phase balance, it is abnormal. At this point, you need to investigate the cause.

4. Firstly, eliminate the error of the temperature controller. Swap the position of the temperature probe.

5. The simplest way is to use infrared temperature measurement to measure the actual surface temperature of the telemetry coil.

Temperature standard for 10kV dry-type transformers

The working temperature rise of 10kV is around 70 ℃, and the summer is hot, so the overall temperature of 10kV transformer is below 120 ℃.

Working temperature standard for dry-type transformer coils

The surface temperature of the coil of a dry-type transformer shall not exceed 80 ℃ for Class B insulation level. When the ambient temperature is 35 ℃, the maximum allowable temperature shall not exceed 115 ℃. The temperature rise of Class F insulation level shall not exceed 100 ℃, and the maximum allowable temperature shall not exceed 135 ℃ when the ambient temperature is 35 ℃.

Standard for tripping temperature of dry-type transformers

The temperature rise of dry-type transformers shall not exceed 70 ℃, and excessive temperature will accelerate the aging of the internal insulation parts of the equipment. If it is necessary to adjust the ambient temperature during transformer operation, it can be controlled below 50 ℃. The general factory setting is to start the fan for heat dissipation at 90 ℃, to start the high temperature alarm at 120 ℃, and to trip at 160 ℃ ultra-high temperature.

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