Metrological frequency response analysis of a high current instrument transformer

This paper presents the metrological frequency response analysis of a high current instrument transformer (HCT) with a rated primary current of 8 kA. A special measuring system is used to identify the frequency response of the HCT at different primary currents in a frequency range up to 40 kHz. The burden dependency of the frequency response is determined by using different resistive and resistive-inductive burdens. The measuring results indicate the good transmission behaviour of the HCT at higher frequencies by applying resistive burdens. However, resonances occur by applying resistive-inductive burdens, resulting in high resonance peaks which deteriorate the transmission behaviour of the HCT and cause high voltages at its secondary side.