What conditions should the standard current transformer used to calibrate the current transformer meet?

        (1) The standard current transformer should be two accuracy levels higher than the current transformer being tested.

        (2) The error value of the tested current transformer should meet the standard value.

        (3) The variation of the standard current transformer shall comply with the requirements specified in the regulations. During the calibration period, the error of the standard current transformer shall not exceed its standard error limit.

        (4) The standard current transformer must have a verification certificate from a statutory metrological verification agency.