Grounding Key Points and Electromagnetic Induction Systems of Transformer Core Laminations

Transformer Core Laminations and Grounding Key Points

During operation, transformer core laminations serve as the primary magnetic circuit. They are generally assembled by stacking hot-rolled or cold-rolled silicon steel sheets with a high silicon content and insulated surfaces coated with varnish. Together with the coils wound around them, they form a complete electromagnetic induction system. The power transmission capacity of a power transformer depends on the material and cross-sectional area of its iron core.

Grounding Key Points for Transformer Core Laminations

(1) Install a dedicated grounding lead wire for the yoke clamps. If the iron core accidentally contacts the upper clamp, causing a multi-point grounding fault, the fault current would otherwise circulate only internally between the core and the clamp, with no current flowing through the main core grounding lead. This could mislead maintenance personnel into believing that no fault has occurred. By installing this dedicated lead wire, any contact between the core and the clamp—regardless of the location—will create a detectable circuit through the two external grounding leads, ensuring that the grounding current can be accurately detected externally.

(2) Position the core grounding plate at the center of the yoke's cross-section. With this placement, regardless of where the insulating bolts of the yoke tie rods are located or where the accidental grounding point occurs, the induced voltage in the loop will be only 1/4 of the turn voltage. Consequently, the resulting grounding current will be limited to just a few amperes, which is significantly lower than when the grounding plate is placed in other positions.

(3) If site installation constraints require placing the core grounding plate in an alternative position, the insulating bolts of the yoke tie rods and the grounding plate should be positioned diagonally opposite to each other. This arrangement helps prevent the generation of excessive circulating currents.