Rapid voltage changes
BSRIA Power quality guide (AG 2/2000) was written by C C Pearson and V Uthayanan and published by BSRIA in July 2000. It states:
There are several terms for rapid voltage variations, depending on the length of time and the direction of change. Each type of variation can be designated as instantaneous, momentary, or temporary, depending on its duration as classified in Table 15.
Table 15 Classification of voltage changes by size and duration
Short-duration voltage variations are caused by fault conditions, the energization of large loads which require high starting currents, or intermittent loose connections in power wiring. Depending on the fault location and the system conditions, the fault can cause sags, swells and interruptions.
The fault condition can be close to or remote from the point of interest. In either case, the impact on the voltage during the actual fault condition is of short duration variation until protective devices operate to clear the fault.
--BSRIA
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