Method for testing the insulation resistance of iron core of power transformer

When the iron core has an external lead line, it can be measured when the Transformer is out of power; The iron core has no external lead line and can only be measured during overhaul. 2500V insulated resistance meter for measurement(1000V insulated resistance meter for old Transformers). If the core has a ground line, it can also be judged whether the core is grounded at multiple points under the operating conditions. The current value of the earth line outside the core is measured by a pincer current meter; It can also be connected to a human current meter. When the iron core insulation is in good condition, the current is very small. Once multiple points are grounded, the iron core pole flux is equivalent to a short route loop, and there is a circulation in the turn. The size of the circulation depends on the relative position of the fault point and the normal connection location, that is, the number of encircling flux in the short route turn is related to the load of the transformer belt.