Transfer characteristic of a MV/LV transformer in the frequency range between 2 kHz and 150 kHz

Abstract

Switching frequencies of modern, energy-efficient power electronics are commonly located within the frequency range between 2 kHz and 150 kHz, also referred to as supraharmonics. Due to the increasing use of this equipment, rising emission levels and a rising number of interference cases have been observed recently. While first studies exist about the emission and interaction of equipment, little is known about the propagation of supraharmonics via cables and transformers. This paper presents recent research results in order to identify the transfer characteristic of a distribution transformer at higher frequencies based on measurements. After a description of the used transformer, the measurement setup and the performed measurements are described in detail. In order to provide test conditions, which are as close to reality as possible, a two-frequency test signal is used. The last part of the paper discusses the results of the measurements, covering injection on the MV and the LV side as well as single or three-phase supraharmonics among others. The results are quantified by indices representing the transfer (ratio between the same phases at both sides) and the coupling between different phases. The presented results provide a comprehensive basis for the development of respective simulation models.