Need help choosing the right current transformer ?

The insulation class of a current transformer refers to its rated operational voltage or, in other words, the maximum voltage that will be passing through the window of the transformer. Higher voltages need more insulation which will increase the overall size of the transformer.

BIL stands for Basic Insulation Level and refers to the maximum surge voltage the transformer can withstand. Surge voltages are much higher than operational voltages but only last for a very short time, a few microseconds at most.

A Hi-Pot or Dielectric Withstanding Voltage test verifies the integrity of the insulation. A voltage higher than normal operating voltage is deliberately passes through  the transformer, this stresses the insulating material. If the transformer can withstand a high than usual voltage, it will safely operate at its normal rated voltage.

The Rating Factor of a current transformer indicates the amount by which the primary current can increase without exceeded the maximum allowable temperature rise of the transformer. For example, a current transformer with a RF rating of 2.0 can withstand twice its rated current (200%) without heating excessively.

The KA rating or transformer fault current is the maximum current a transformer can withstand during a fault. This is measured is kiloamperes (kA) hence the name.

The KA rating or transformer fault current is the maximum current a transformer can withstand during a fault. This is measured is kiloamperes (kA) hence the name.