ECN Forum Forums General Topics of the Trade General Discussion Area Over voltage level at night for Street lights

Hi all,
I have a product to regulate the voltage that feeds streetlights of mercury vapour and high preasure sodium. I need to know what is the overvoltage level on the street lights at night to calculate energy savings when power is regulated. In other countries power is not stable at all, how is it in USA?

if the street lights circuit is 240VAC will it go to 250, 260 or at what level during the night?

same for 277VAC and 480VAC.