What is the normal low-side rating of a current transformer?

The normal low-side rating of a current transformer is typically 5 amps. This value is significant because current transformers (CTs) are used to transform high currents to a lower, manageable level for measurement and protection purposes. The 5-amp rating is a common standard in many applications, particularly in power systems, where it allows for accurate measurement without overloading the secondary side of the transformer.

Using a 5-amp rating offers a suitable balance between sensitivity and capacity, making it effective for various metering and protective relaying applications. In practical terms, this means that when the primary current flows through the transformer, the secondary output is scaled down to a 5-amp output, allowing connected devices to safely monitor electrical conditions without risking damage or inaccurate readings.