Frequency versus time domain immunity testing of Smart Grid components
Smart Grid components often are subject to considerable conducted current disturbances in the frequency range 2–150 kHz and, as a consequence, it is necessary to provide reliable immunity test methods. The relevant basic standard IEC 61000-4-19 that is currently under discussion focusses on frequency domain test methods. It is remarked in this contribution that in the context of frequency domain testing the chosen frequency spacing is related to the resonance response of the system under test which, in turn, is characterized in terms of resonance frequencies and quality factors. These notions apply well to physical system but it is pointed out by the example of an actual smart meter immunity test that smart grid components may exhibit susceptibilities that do not necessarily follow a resonance pattern and, additionally, can be narrowband. As a consequence it is suggested to supplement the present frequency domain test methods by time domain tests which utilize damped sinusoidal excitations with corresponding spectra that properly cover the frequency range 2–150 kHz, as exemplified by the military standard MIL-STD-461.