Clocks in town mysteriously changing by 10 minutes

[russ_watters]

Billing is pretty complicated. Commercially, they bill for peak demand (kW), consumption (kWh) and power factor if you are outside of a certain range (.85 maybe...?). There are a host of complexities such as time of use, demand ratcheting (if you set a high peak in August you get charged for part of that in Sept.), price bands for different usages, etc. Its so complicated my dad makes a living by finding billing and rate errors and saving clients money.

 

[geometer]

I've never worked for the power company but I know a little bit about something called tracebility. Tracebility deals with how an end product or service is tied back to the National Bureau of Standards. Most likely a number of power plants, if not all of them, are tuned into WWV out of Ft. Collins CO in order to obtain a frequency standard. They then use this timebase to measure the frequency of or RPM of the generators. However, it probably doesn't do much good for error correction since if one generator measures a frequency error, all the plant can do is report it to the rest of the grid. I believe they also count the TOTAL number of cycles in a given period of time (possibly a day or more) and actually simultaneously correct for it. Probably over a period of a couple of minutes or something, maybe more I am not sure. This was told to me by an electrical engineer who had power distribution classes in college.

I've been away from this thread for a while, so I apologize if I'm beating a dead horse, but I think it needs to be made clear here that utilities do not regulate their frequency by checking with some central standard. The generators in utility plants are built with so many poles in them and given that number of poles, you can calculate the RPM your turbine has to turn to give you a 60 Hz (or any other frequency) output. The turbines then have governors on them that keep them at that RPM. Once connected to the grid, if your turbine RPM drops a little, you get some complicated feedback from the grid that will drag your turbine back up to the appropriate RPM and frequency.