Download Characteristic Study of Electronic Voltage Transformers` Accuracy on

Characteristic Study of Electronic Voltage Transformers’ Accuracy on
Harmonics
LIU XIANG, HU BEI,TONG YUE, YUAN TIAN，YAN FAN
China Electric Power Research Institute
Abstract:
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 standard system for this measuring in China, the accuracy test on harmonics haven’t been done yet. So
the standard system for electronic voltage transformer’s accuracy measuring 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 1200Hz,the standard system for accuracy measuring 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. And the test results of
accuracy on harmonics of electronic voltage transformer can meet the requirements of standards .
1.
Introduction
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 20840.7-2007 and IEC60044-7：2002. But because
there was no mature standard system for this measuring in China, the accuracy test on harmonics haven’t been
done yet.
2.
Principle of measuring system
According to the principle of accuracy test, combining with the characteristics of electronic instrument
transformers, the accuracy measuring system is consist of high precision digital multimeters and
digital instrument transformer test set. The voltage signal from standard system is converted to digital signal by
digital multimeters and input to test set together with the output of the electronic voltage transformer to test the
accuracy of the harmonic.
3.
Realization of standard system
The standard system for accuracy measuring on harmonics is consisted by a high voltage follower and a
divider system. The divider system is formed by two matched capacitors with the same frequency change trend.
The accuracy of the standard system can meet the requirements of standards.
4.
Experiment
Measuring the the accuracy of the harmonic of different kinds of electronic voltage transformers by the
measuring system, the preliminary study on the accuracy of the harmonic have been done.
5.
Conclusion
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. And the test results of accuracy on harmonics of electronic voltage transformer can meet the
requirements of standards’ .
Keywords:
accuracy measuring on harmonics, standard system, characteristic of accuracy, active electronic voltage
transformer, passive electronic voltage transformer
Author’s brief introduction and contact information:
LIU Xiang, born in October 1981, graduated in 2007 with a bachelor’s degree in high voltage and
insulation from Xi’an Jiaotong University, is a master’s degree student, and a senior engineer, specializing
in electronic transformers’ reliability, transformer testing technologies, and high-voltage measurements.
Email: [email protected]；TEL：13507177487