Off-line calibration is the main method for CVT error checking

which causes a lot of problems such as huge workload and the results deviate from the actual value of the CVT on-line running error. So a kind of new online calibration method is proposed in the paper with the help of running capacitive equipment. Based on the common structure of LVQB type current transformer

some changes are done to realize the function of high voltage standard capacitor. By untying the ground wire of reconstructed LVQB type current transformer and series connecting a low-voltage standard capacitor and a voltage divider

a standard capacitor voltage divider can be set up to become an on-line standard device so as to make the on-line calibration of CVT available. The new method avoids the risk of switching the standard capacitor voltage divider directly. When the error calibration work is finished

the ground wire is recovered so the LVQB type current transformer is an ordinary current transformer.With the applications of this method

the on-line error calibrating method will replace the traditional off-line method and provide the basis for on-line maintenance of electrical equipment.