This was originally posted on APC forums on 2/21/2011
I enjoyed reading your Seven Types of Power Problems but I have a suggestion. I think it would be helpful for readers, especially home users, to add another example in the section on Sag - Undervoltage. You mention flickering of lights, but the problem I had was not a rapid flickering but a momentary dimming of lights for a few seconds or longer whenever an appliance motor cycled on and off, such as in a refrigerator, furnace, or especially a clothes dryer. An electrical contractor advised me that my service level was likely adequate for the size of house and to contact the power utility and request a line check. He explained that the likely culprit was a faulty neutral side connection somewhere between the power pole and the electrical panel inside the house. I did request a line check "due to dimming of the lights," which the utility promptly performed the same day. I have not expeerienced the problem again since that time.