Current Transformer

Nomenclature of CT:

·         Ratio: input / output current ratio

·         Burden (VA): total burden including pilot wires. (2.5, 5, 10, 15 and 30VA.)

·         Class: Accuracy required for operation (Metering: 0.2, 0.5, 1 or 3, Protection: 5, 10, 15, 20, 30).

·         Accuracy Limit Factor:

·         Nomenclature of CT: Ratio, VA Burden, Accuracy Class, Accuracy Limit Factor.

·         Example: 1600/5, 15VA 5P10  (Ratio: 1600/5, Burden: 15VA, Accuracy Class: 5P, ALF: 10)

·         As per IEEE Metering CT: 0.3B0.1 rated Metering CT is accu­rate to 0.3 percent if the connected secondary burden if imped­ance does not exceed 0.1 ohms.

·         As per IEEE Relaying (Protection) CT: 2.5C100 Relaying CT is accurate within 2.5 percent if the secondary burden is less than 1.0 ohm (100 volts/100A).