Undervoltage
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:
Variations in supply voltage outside the normally accepted limits of ± 10% are subdivided according to the length of the variation.
Long duration variations encompass rms deviations at power frequencies for longer than one minute. EN 50160 specifies the steady state voltage tolerances expected on a power system. A voltage variation is considered to be of long duration when the limits are exceeded for more than 3 minutes (the international standards use a period of one minute).
Long duration variations can be:
- sustained interruptions
- undervoltages
- overvoltages.
An undervoltage is a decrease in the rms ac voltage to less than 90% at the power frequency for a duration longer than 3 minutes.
Undervoltages are the result of the events which are the reverse of the events that cause overvoltages. A load switching on or a capacitor bank switching off can cause an undervoltage until voltage regulation equipment on the system can bring the voltage back to within tolerances. Overloaded circuits can also result in undervoltages.
--BSRIA
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