What is the rating of the primary current in the current transformer?

The rating of the primary current in a current transformer (CT) depends on the specific application it is designed for. Current transformers are used in electrical systems to reduce high voltage currents to a lower, safer level for metering, protection, and control in high-voltage circuits. The primary current rating is typically specified based on the maximum current that the CT can safely handle without exceeding its accuracy limits or thermal capacity. This means the rating can vary widely, from a few amperes to thousands of amperes, depending on the requirements of the electrical system in which it is installed.

For instance, in a residential or small commercial building, a common primary current might be in the range of 100A to 400A, whereas in a large industrial setting or substation, the primary current rating could be in the thousands of amperes. The selection of a CT with an appropriate primary current rating is crucial for accurate measurement and for ensuring the safety and protection of the electrical system.