Hi All,
BS7671 says the permitted tolerance for low voltage (230V) supply is +10%/-6%.
And table 41.1 for max disconnection time states that for a TN system, if the system supply is less than or equal to 230V ac, the disconnection time is 0.4s and if the voltage is greater than 230V ac, the disconnection time is 0.2s
Do the above two concepts contradict? how could one account for an increase in voltage for a short time at the source as two different disconnection times has to be considered? Should it be based on the worst case of 0.2s?
Many Thanks for your response.