480 volt to ground question and info

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Tim_Nelson

Member
Location
Bonita Springs,Fl.
I'm working in south florida and we are doing street light repairs for the city municipality where i'm at.
FPL is our provider.
Basically, the city has been paying a flat rate from FPL to operate their lights. But now they want meters because we have been changing from high pressure sodium to LED.
No big deal so I THOUGHT.
But are after consideration?
480 V to ground has a couple of complications.
number one.
Will the meters handle 480 V on one leg?
Number two
Is there a meter that FPL can provide that will read one leg at 480 volts to ground?
Anyone who's worked with Fpl, Knows about the cooperation that they do or do not have depending on circumstance.
I'm just trying to get a leg up.
Will they need a CT meter?
Or is there something that I can suggest?
Granted, this is the utility company's problem. However, they really don't care as I'm sure anyone that has worked with utilities understands.
Ok.
Let us open the discussion 🤣
 
tom baker

tom baker

First Chief Moderator & NEC Expert
Staff member
Location
Bremerton, Washington
Occupation
Master Electrician
Our street lighting and signals were flat rated but we have added meters to track usage. With flat rate someone at city has to update utility with adds and changes (and that somebody retires or leaves) Both you and POCO can have incorrect billing. Your POCO may have a customer service handbook with meter details
For us having a meter resulted in a service address and account that simplified outage reporting. Plus the meters are AMR and self report outage and status
 
T

Tim_Nelson

Member
Location
Bonita Springs,Fl.
My interest was wether or not they had a way to measure it accurately.
After all most meters require two legs.
With 480 volts to ground you have one leg one neutral.
A. CT meter may be needed unless there is another way,that was my question
 
T

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Could be a 2 wire 480 volt with one leg grounded as the OP indicates. That used to be a common thing for FPL street lighting but I thought they went to using 480 center taped some years back as it is safer and easier to deal with. Been many years since I did anything on FPL turf.
 
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Tim_Nelson

Member
Location
Bonita Springs,Fl.
Currently they have it running based on the old-fashioned. Insulated bars that connect the meter cans point of contact.
1 leg,direct connected.
How can you Meter that one leg connection
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Tim_Nelson said:
The city wants the metering.
I'm just not sure if FPL can get it done.
I've never heard of a meter that measures one leg, let alone at 480 V to ground.
Click to expand...
It’s single phase, the meter doesn’t care if on leg is grounded. The electronics powering it may, EKM probably makes a meter that can. Just a CT around one wire, maybe a PT to power the electronics.
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Tim_Nelson said:
Currently they have it running based on the old-fashioned. Insulated bars that connect the meter cans point of contact.
1 leg,direct connected.
How can you Meter that one leg connection
Click to expand...

You cannot meter one leg. To measure power you must measure both voltage and current. To measure voltage you must _always_ have 2 connections. For a power supply system with N wires, to be accurate you must measure N-1 voltages and N-1 currents.

But there is no problem at all if you make the connection 'hot to neutral' (really 'ungrounded' circuit conductor to 'grounded' circuit conductor). For the 2 wire service being described, the measured voltage _must_ be 'hot to neutral', but that works just fine as the required voltage measurement.

(And yes, common residential meters are not 'Blondel Compliant' and only measure a single L-L voltage, and a single average current. This leads to small inaccuracy by assuming the L1-N and L2-N voltages are the same. Ideally in residential applications you would separately measure the two L-N voltages and the two L currents, and then add the resulting power measurements.)

Jon
 
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