This test is designed to ensure that the protective circuit (Earth Bar) is capable of handling the prospective current and energy seen during an external earth fault. Generally the device with the largest energy let through is selected for this test. This is most commonly the largest MCCB. The phase closest to the Earth bar is shorted to the Earth bar. An Icc test is then carried out in exactly the same method as in clause 10.11.
As an alternative option, the Earth bar can be subjected to an Icw test, with a current level of 60% of the main bars, for a duration not less than the maximum expected trip time of a device, normally 200mS.