A damped oscillatory wave (DOW) is a sine wave that oscillates as it loses its strength and is generally found in situations like the opening and closing of high-voltage components in substations. To protect substations from damped oscillatory transients, the components need to be tested for the strength of their conducted immunity. A transient generator can send either slow or fast damped oscillatory waves into a component or electrical system, which simulates real world oscillating transients and gives test engineers feedback on when and why switchgear, circuit breakers, protective relays and more components fail.
A slow damped oscillatory wave is generally associated with the switching of HV busbars in substations. Slow DOW will also occur in power, signal and control cables installed in substations. For testing purposes, a slow damped oscillatory wave is generated at a frequency range of between 100kHz to 1MHz. Fast damped oscillatory waves are found in electrical substations, produced by switchgear and controlgear, and installations in general which are exposed to high-altitude electromagnetic pusles (HEMP). Often fast DOW will possess a high transfer impedance, which results in voltage impulses. A fast DOW is generated at a frequency of 10, 30 or 100MHz.
Damped Oscillatory Wave Test Standards