Generally speaking, the temperature allowed by the dry type transformer is related to the heat resistance grade of the insulating material used. Usually, when the Dry type transformer uses F and H class insulation materials, the allowable temperature rise of F class is 100K and the maximum allowable temperature is 155 ° C, and the allowable temperature rise of H class is 125K and the maximum allowable temperature is 180 ° C.
The heat resistance grade of the insulation system is the decisive factor of the maximum allowable temperature of the transformer
The insulation materials used in the insulation system of electrical equipment mainly include class A, class E, class B, class F, class H, class C and other levels, and the main heat resistance level is different as follows:
When class A insulation materials are used, the maximum temperature rise should be less than 60K when the limit operating temperature is 105 ° C;
When the E class insulation material is used, the maximum temperature rise should be less than 75K when the limit working temperature is 120℃;
When the B-class insulation material is used, the maximum temperature rise should be less than 80K when the limit working temperature is 130℃;
When the F-class insulation material is used, the maximum temperature rise should be less than 100K when the limit working temperature is 155 ° C;
When the H-class insulation material is used, the maximum temperature rise should be less than 125K when the limit working temperature is 180℃;
When the C-class insulation material is used, the maximum temperature rise should be less than 150K when the limit operating temperature is 220 ° C.
Because the coil insulation of Dry type transformers is usually F and H class insulation materials, the maximum absolute normal temperature is not allowed to exceed 155 ° C and 180 ° C. If the winding temperature of the dry type transformer is too high, it will cause its insulation aging to accelerate, which will affect the service life or short-circuit, fire and other faults, so from the point of view of the hot spot temperature alone, the lower the operating temperature of the transformer, the better, in order to prevent the abnormal operating temperature, the need for strict inspection or monitoring in use.
Cast resin type transformer
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Winding temperature appreciation is an important index to judge whether the transformer temperature is too high
In fact, the ambient temperature of the Dry type transformer operation changes throughout the year, so in the case of the same load, the absolute temperature in summer is often higher, and the absolute temperature in winter is often lower, so the management, on the one hand, should pay attention to whether the highest absolute temperature value of its winding exceeds the standard (especially in summer), on the other hand, It is also important to pay attention to another important temperature indicator, that is, whether its temperature rise is abnormal.
From the maximum temperature rise limit of the dry type transformer, the temperature rise is not allowed to exceed 100K when using F-class insulation materials, and the temperature rise is not allowed to exceed 125K when using H-class insulation materials. For a specific dry-type transformer, the relevant specified value of the rated temperature rise can be found, which is related to the ambient temperature. The rated temperature rise refers to the difference between the temperature of a certain part and the temperature of the external cooling medium (cooling air temperature or cooling water temperature) when the transformer is working under the rated load, in K. For example, a Dry type transformer rated temperature rise of 90 ° C, under the rated load and 40 ° C ambient temperature (hot summer), its maximum temperature is 130 ° C (90 ° C +40 ° C); If the ambient temperature is low (in cold winter), such as 10 ° C, then the maximum temperature of the transformer is 100 ° C (90 ° C +10 ° C). When the temperature rise is too high, it is necessary to start the cooling system for cooling, or carry out appropriate load reduction management. When the continuous abnormal temperature rise occurs, the cause of the abnormal temperature rise should be investigated and the corresponding treatment should be carried out.
Dry type distribution transformer
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