Microgrids operate in islanding or utility grid mode. In islanding mode, distributed energy sources with power electronics inverters can generate fault currents over a wide range of frequencies. To gain a better understanding of the nature of these events, it is crucial to measure currents at frequencies of up to 20 kHz at transient states with protective relays. Protective relays at these frequency responses should be tested prior to being installed in microgrids. However, testing at high-frequency currents cannot be done with Relay Test Equipment (RTE) that generate signals up to 50th Harmonic for 60 Hz (3 kHz). In this study, a frequency response method and testbed for high-frequency currents of up to 20.16 kHz was developed and tested. The testbed utilized a RTE and High-Frequency Power Source/ Amplifier. Frequency relay experiments were run at frequencies of up to 1 and 20.16 kHz at a current magnitude of 0.1 and 0.5 A, respectively. The events were collected, and the current magnitude and frequency were plotted at time and frequency domain, respectively. The study of current magnitude and frequencies of up to 20.16 kHz for two overcurrent relays was performed and validated the variable frequency testbed and methodology.

微电网以孤岛或公用电网模式运行。在孤岛模式下，带有功率电子逆变器的分布式能源可以在很宽的频率范围内产生故障电流。为了更好地了解这些事件的性质，至关重要的是使用保护继电器在瞬态下以高达20 kHz的频率测量电流。在将这些频率响应的保护继电器安装到微电网之前，应对其进行测试。但是，不能使用继电器测试设备（RTE）在高频电流下进行测试，该设备会在60 Hz（3 kHz）的频率下产生高达50谐波的信号。在这项研究中，开发并测试了频率响应方法和用于高达20.16 kHz的高频电流的测试平台。测试台使用RTE和高频电源/放大器。频率继电器实验分别在高达1和20.16 kHz的频率下，以0.1和0.5 A的电流幅度进行。收集事件，并分别在时域和频域绘制当前幅度和频率。进行了两个过电流继电器的电流幅值和频率高达20.16 kHz的研究，并验证了变频试验台和方法。