I have read on this page that NZ consumer voltage is 230v +/- 6% which means a low of 216.2v and a high of 243.8v
http://www.trustpower.co.nz/index.php?section=79
I have a UPS that is showing fluctuations in the last 6 hours within this range (222v to 238v), though the fluctuation is fairly regular (it changes 15-20 times an hour significantly and upto 40 times an hour in smaller increments).
But what should be realistically expected - should the voltage ideally be very stable or is it expected that 15 to 20 times an hour it will move 'significantly' within the expected range?