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What is the Ground Fault Accuracy of the C445 with external CT's?

The XCT300-5 has an operating range of 17 – 300 amps @ a 300:5 ratio with published accuracy of 0.3%, as noted on page 6 of the C445 UM.

The C445MA-005 has an operating range of 1 – 5 amps @ Gf protection of 30% when coupled with the XCT300-5, as noted on page 137 of the C445 UM.


When coupled with the C445MA-005, the minimum primary current of 17 amps (0.28 amperes secondary current) falls below the 1 ampere minimum monitoring range of the C445MA-005. With this in mind, the minimum effective monitoring current of the XCT300-5 is 60 amperes of primary current which in turn yields a secondary current of 1.0 amperes which is within the monitoring range of the C445MA-005.

Gf protection of 30% @ 60 amperes (primary) results in a Gf current value (flow) of 18 amperes (± 0.6 amperes CT accuracy) or greater downstream of the C445MA-005 location to cause the C445 to react to this condition.