Method to Measure CVT Transfer Function

The results of tests on a 275 kV and a 400 kV capacitor voltage transformer (CVT) are presented. The objective has been to determine the transfer function of the CVTs in the Scottish Power EHV system, which in turn can be used to compensate for the errors at harmonic frequencies. As a primary requirement, the magnetic elements of the CVTs must be excited at nearly their nominal magnetic states. A test procedure is presented that does not require CVT disassembling and/or modeling and ensures that the above essential requirement is satisfied. The effects of burden on the frequency response will also be presented. It will be confirmed that the size and nature of burden affect the CVT frequency characteristic.