Current Limit of transformer lamination core and Selection of Sliding Wire Resistance

- Jun 28, 2019-

The transformer lamination core can measure the current on the grounding wire. It can be used on the grounding lead of the grounding bushing of the transformer core to measure the current on the lead with a clamp meter. When the transformer core is normally grounded, no current loop is formed. The current on the ground line is very small and is milliampere (generally less than 0.3A). When there is multi-point grounding, there is a short-circuit 匝 around the main magnetic flux of the iron core, and the circulating current flows in the 匝. The value depends on the relative position of the fault point and the normal grounding point, that is, the amount of magnetic flux surrounding the short-circuiting 匝. Generally up to tens of amps. By measuring the presence or absence of current in the ground lead, it is very accurate to determine whether there is a multi-point ground fault in the core.

The transformer lamination core has an external grounding wire. If the fault current is large, the grounding wire can be temporarily opened. However, monitoring must be intensified to prevent the core from appearing in a floating potential after the fault point disappears.

If the multi-point ground fault is unstable, a slip line resistor can be placed in the working ground wire to limit the current to less than 1A. The choice of the slip line resistance is the voltage measured by turning on the normal working ground line divided by the current on the ground line.

The transformer lamination core is chromatographed to monitor the gas production rate at the point of failure.