Errors in measuring of high voltage harmonics in the medium voltage power networks

Amplitude frequency responses of inductive voltage transformers with cast insulation designed for 24kV and 36 kV power networks are studied. The analysis was carried out in the range of the transformers´ secondary winding loads from idling mode up to rated load. In the paper it is shown that because of the errors in the amplitude frequency response of the voltage transformers, it is necessary to conduct research in the simultaneous presence of the industry frequency voltage and the voltage harmonics in the transformer primary circuit. The measurements have been carried out in the frequency bandwidth up to 2.5 kHz. Amplitude frequency responses in the range between 100 and 2500Hz of some types voltage transformers mentioned above allow correcting the measurement results obtained by smart measuring devices in the presence of high voltage harmonics in the network.