Impedance Determination for High Voltage Air-Core Reactor Over Wide Frequency Range Based on Impulse Injection Technique

To analyze interference induced by transient overvoltage, this article proposes an impulse injection technique for determining the impedance of a high-voltage air-core reactor over a wide frequency range. By injecting nanosecond pulses into reactor in open-circuit, short-circuit and loading conditions, the linear characteristics of air-core reactor can be revealed up to several MHz. Then the equivalent two-port impedance including stray parameters can be derived from the measured current waveforms. Using vector fitting and impedance synthesis, the equivalent circuit is obtained and can be further applied in transient simulation. As an example, a 110 kV reactor is studied in this paper and its equivalent circuit is deduced in the frequency range of [2.5 kHz, 10 MHz]. The accuracy of the model is validated based on the measurements of a loading experiment.