(1) External factors refer to peripheral causes, environment, and human-induced ground faults in transformer cores, including:
(1) Insufficient care must be taken in the installation and installation of the transformer on the site. Metal foreign objects such as nuts and iron chips are left inadvertently to cause the multi-point grounding of the dry-type transformer core.
(2) Insulation materials such as dry-type transformer iron core insulation clamps and iron-core insulation cores are used to reduce the insulation performance of the iron core due to condensation or moisture, resulting in low-resistance multi-point grounding of the iron core;
(3) The magnetic flux leakage of the core during operation of the transformer causes weak magnetic properties in the nearby space, which attracts the surrounding metal powder and dust. If there is no maintenance and cleaning for a long time, multipoint grounding of the iron core may occur;
(2) Intrinsic factors refer to multiple grounding faults in the transformer core caused by defects in the internal insulation material of the transformer or improper product design and installation processes.
The Because the intrinsic factors of multi-point grounding of the dry-type transformer core are hidden problems, it is not easy to find the factory or on-site inspection. Therefore, it is more necessary to rationally and seriously determine the fault and solve the problem.
For dry-type transformers that have been decommissioned for a long time or have not been sealed, due to moisture or condensation, especially in southern weather and offshore areas, the multi-point earth fault of the iron core is caused by external factors. In this case, due to the dampness of the iron core insulating material, the insulation performance is reduced and the failure is caused.
The processing method may use multiple sun lamps to bake the clips, and use the sun lamp to heat the clips to heat the insulators between the cores and the clips to evaporate their own water, but the time required is longer; or conditions If allowed, baking can be done using the no-load method.
