Allowed utility fluctuation

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Sharpie

Senior Member
Location
PA
Just curious, does anybody know how much utilities are allowed to deviate from nominal voltage and Hz? And who would be imposing/ reinforcing these rules on the utility?

Thanks,
 

cschmid

Senior Member
As far as know it is 10% from the nominal voltage. but I do not know on what line it is measured from? I would be curious if someone can find the regulation on this. I suppose it is the utilities commission but really have never searched for it. good question..
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I expect that each state sets their own rules. Here is what is required in Illinois.
Section 410.300 Voltage Regulation

a) Standard voltage. Each entity supplying electrical energy for general use shall adopt a standard service voltage of 120 volts (when measured phase to neutral) and shall maintain the service voltage within the allowable variations from that value at all times.

b) Allowable voltage variations. For service rendered at the standard service voltage, voltage variations as measured at any customer's point of delivery shall not exceed a maximum of 127 volts nor fall below a minimum of 113 volts for periods longer than two minutes in each instance. For service rendered at voltages other than the standard voltage value, voltage variations as measured at any customer's point of delivery shall not exceed 10% above or below the service voltage for a longer period than two minutes in each instance.

c) Variations of voltage in excess of those specified above shall not be considered a violation of this Section if caused:

1) by operations of a retail customer in violation of an agreement with or the rules of the entity;

2) by the operation of apparatus on a retail customer's premises that results in large inrush currents;

3) by infrequent and unavoidable fluctuations of short duration due to system operation; or

4) by acts of nature or other situations beyond the entity's control.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Ron,
Apparently Illinois doesn't care about the frequency as I don't see it covered in the rule:D

I didn't look far enough...frequency is covered..
Section 410.320 Standard Frequency

Each entity that supplies alternating current for use by retail customers in this State shall operate its equipment in a manner that the frequency of the alternating current maintained by the operation of the interconnected transmission systems is not degraded as a result of any action or lack of action on the part of the entity.
 
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PetrosA

Senior Member
In PECO territory for residential service, anything below 232V measured between legs is considered below tariff and is grounds for calling a crew in to fix it. I'm not sure about high tariff numbers or 3 phase numbers. Low voltages and high voltages are pretty rare around here.
 

Den

Member
Location
Southern Iowa
Here it is the Iowa Utilities Board (I think) and the distribution people (they sell to end user) buy electricity from the transmission people (they own our sub stations) and they buy from the power plant people who make it. All down the line voltage is monitered and is regulated. Our poco has metering in the substations and when needed we have voltage regulators on the line which keeps up with the demand at the time. These regulators are not instantanious and will take several minutes to stabalize with the demand. All of our meters are electronic and they also record the voltage and other things and are checked every few days for the readings so that somebody knows what is happening and get corrections made if needed. (That's how it is supposed to work anyway.)
 
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