Frequency Responses of MV voltage transformers in the range of 50 Hz to 10 kHz

Abstract

Voltage quality plays an important role in modern distribution networks. One voltage quality parameter is harmonic distortion. Voltage harmonics in MV-networks are measured in most cases by using installed inductive voltage transformers (IVT). The accuracy of these transformers for frequencies above nominal frequency (50Hz or 60Hz) is usually not known. The paper presents a systematic analysis of the frequency-dependent accuracy of these IVT's for harmonic measurements in the frequency range up to 10 kHz and it's dependency from different factors and operating conditions. After an overview of possible factors that influence the frequency response, the used measurement equipment and methodology is described. The frequency responses of more than 85 IVT's with rated primary voltages between 10 kV and 35 kV were measured and analysed. The significance of each influencing factor to the frequency response is discussed and finally a frequency-dependent measurement uncertainty range for 20 kV IVT's is proposed.