Characteristic Study of Electronic Voltage Transformers' Accuracy on Harmonics

Harmonics in electric power systems can affect the measurement, quality analysis and relay protection of the power grid, making the accurate measurement of harmonics a necessity. The broad frequency range of electronic transformers makes them suitable for measuring harmonics. The requirements of accuracy on harmonics for electronic transformers are put forward in the standards GB/T 20840.8-2007 and IEC60044-8: 2002. But because there was no system for this measuring in China, the accuracy test on harmonics haven't been done yet. So the measuring system for electronic voltage transformer's (EVT) accuracy on harmonics had been studied and found in this article. Then the preliminary measuring of accuracy on harmonics of different kinds of electronic voltage transformer has been done. And the test results have also been analysed. All the results shows that: under the condition of voltage from 0 to 80kV, frequency from 50Hz to 650Hz, the measuring system for accuracy on harmonics we found can meet the requirements of standards. In terms of accuracy on harmonics, the variation of the active electronic voltage transformers' ratio error is less than the passive electronic voltage transformers' with the increase of the harmonic order. And the variation of the active electronic voltage transformers' phase displacement is more than the passive electronic voltage transformers' with the increase of the harmonic order. The test results of accuracy on harmonics of passive electronic voltage transformer can meet the requirements of standards. And the active electronic voltage transformer need to improve the production craft to meet the requirements.