Research and verification of DC current ratio self-calibration method

In order to evaluate the metrological performance of DC current ratio instruments in real time, a DC current ratio self-calibration method based on reference winding is presented. Set reference winding with unit turns value; conduct two independent measurements for difference current after connecting DC current; the actual conversion value of primary current against secondary current is finally obtained combining with formula deduction and calculation. The classic equal nominal ratio calibration method is employed to verify the self-calibration results; the normalized error $E_{\mathrm{n}}$ equals 0.43. This self-calibration method is characterized by the advantages of two simple measurement processes and measurement uncertainty of $8\times 10^{-7}$.