变压器在运行过程中，其铁芯以及夹件等金属部件均处在强电场之中，因为静电感应会在铁芯及金属部件上产生悬浮电位，而这一电位会对地放电，这当然是不行的，所以，铁芯以及其夹件等都必须正确和可靠地接地（只有穿心螺栓的除外）。
During the operation of transformer, its iron core and metal parts such as clamps are all in a strong electric field, because electrostatic induction will produce suspended potential on the iron core and metal parts, and this potential will discharge to the ground, which is certainly not feasible, so the iron core and its clamps must be grounded correctly and reliably (only through). Except for heart bolts.
而铁芯只允许一点接地，如果有两点或者多点接地，铁芯就会与接地点和大地构成了闭合的回路。变压器运行的时候，有磁通就会穿过此闭合回路，就会产生所谓的环流，引起铁芯的局部过热，甚至烧毁金属部件以及绝缘层。
The core only allows one point to be grounded. If there are two or more points to be grounded, the core will form a closed circuit with the grounding point and the earth. When the transformer is running, the magnetic flux will pass through the closed circuit, which will produce so-called circulation, cause the local overheating of the iron core, and even burn down the metal parts and insulation layer. _