Key Points of Transformer Core Lamination Grounding and the Electromagnetic Induction System

The transformer core laminations serve as the primary magnetic path during operation. They are generally constructed by stacking hot-rolled or cold-rolled silicon steel sheets with a high silicon content and an insulating varnish coating. Together with the coils wound around them, the core and windings form a complete electromagnetic induction system. The power transmission capacity of a power transformer depends on the core material and its cross-sectional area.

Key Points for Grounding Transformer Core Laminations

(1) Install a separate grounding lead for the yoke clamping structure. If the core accidentally contacts the upper clamping structure, causing a multi-point grounding fault, the fault current will circulate only within the core and clamping structure. No current will flow through the core grounding lead, which could mislead personnel into believing that no fault exists. By installing this separate lead, a closed loop is formed via the two external grounding leads regardless of where the core contacts the clamping structure, allowing the grounding current to be accurately detected externally.

(2) Place the core grounding strap at the center of the yoke's cross-section. With this placement, regardless of the position of the yoke tie-rod insulation bolts or the location of the fault grounding point, the induced voltage in the loop will be only 1/4 of the turn voltage. Consequently, the grounding current will be limited to just a few amperes, which is significantly lower than when the grounding strap is placed in other locations.

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