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Wei Yan, Yi Li, and Ilya Budovsky
National Measurement Institute Australia
To meet the growing industry demand, NMI has developed a range of capabilities to measure fast transient high voltages. Such voltages, with a peak value greater than 1 kV and time to peak typically less than 1 s, are created by nuclear electromagnetic pulses, lightning phenomena, and switching events in power systems. Fast transient high voltages are also generated in high-voltage laboratories to test the robustness of insulation and electromagnetic compatibility of electrical and electronic devices.

One variety of fast transients is the steep front impulse. It is used for detecting imperfections in internal insulation of high-voltage apparatus, such as ceramic and polymer insulators and machine windings (Figure 1). Very fast rise times up to 2500 kV/s create a rapidly increasing field across the insulation media, with sufficient energy to free up electrons in the areas of internal defects or interface of different materials. To measure these impulses the NMI high-voltage laboratory has developed an impulse divider with a rise time of 120 ns and a maximum input voltage of 1 MV.  NMI has also developed a waveform reconstruction algorithm that can recreate the true waveforms using the measured step response of the measurement system and the measured steep front impulse waveforms. Using these instruments and methods, the least uncertainty of ± 3% can be achieved for the peak voltage of steep front impulses.

Another type of fast transient voltage is electrical fast transient (EFT) bursts, which have even faster rise times than those of the steep front impulses. The EFT bursts contain multiple series of short pulses, each with a peak voltage up to a few kilovolts, a rise time of 5 ns and a pulse width of only 50 ns. The EFT bursts are used in the electrical immunity tests to ensure reliable operation of electrical and electronic devices that are designed to withstand real-life levels of fast transients. NMI has developed state of the art reference measurement systems, including automated software for measuring EFT bursts and calculating their parameters in accordance with IEC 61000 4 4:2012. 

The ability to accurately measure fast transient high voltages has enabled NMI to deliver new services to its energy sector stakeholders. In recent years, NMI has helped local industrial clients to investigate equipment service conditions of equipment, analyse faults and verifying new equipment designs, resulting in significant cost saving.  NMI has also provided the EFT calibration services to electromagnetic compatibility (EMC) test laboratories so that the measurement traceability of the EFT devices can be established.

For more information regarding NMI’s capabilities on fast transient high-voltage measurement please contact This email address is being protected from spambots. You need JavaScript enabled to view it. .