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capuchi (Electrical) (OP)
25 Mar 09 9:07
hi to everybody,

I plan to install ac voltmeter and ammeter on a 3 phase, 3-wire main dist. panel using transformer rated current voltmeter and ammeter to monitor current (amps) demand on the system. Can anybody please direct me to a URL or links that has sample wiring diagrams showing the connection to potential and current transformers.

Further, can I use the 2 nos. CT's presently serving the kilowatthour meter?

any help will be very much appreciated.

capuchi
Helpful Member!  racobb (Electrical)
25 Mar 09 10:51
"I plan to install ac voltmeter and ammeter on a 3 phase, 3-wire main dist. panel using transformer rated current voltmeter and ammeter to monitor current (amps) demand on the system. Can anybody please direct me to a URL or links that has sample wiring diagrams showing the connection to potential and current transformers."

If it is a listed panel, you may void the listing by installing additional meters/equipment in the panel.  Otherwise, if you already have the meters, the mfg. should have wiring diagrams...if not, try SATEC, Bi-Tronics, or Electro Industries websites for info.

"Further, can I use the 2 nos. CT's presently serving the kilowatthour meter?"

You can if they are yours and you do not over burden them.  If they belong to the utility, I seriously doubt they will allow you to connect to them.

You could also purchase a 3 wire power meter and get kW and kVAR along with the amps and volts.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner.  Liberty is a well armed sheep!
Ben Franklin

racobb (Electrical)
25 Mar 09 12:22
Forgot to add on the previous post that once you get the diagrams you will see that the current coils will be wired in series and the potential coils will be an additional tap from the PT's in parallel.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner.  Liberty is a well armed sheep!
Ben Franklin

capuchi (Electrical) (OP)
25 Mar 09 22:04
Thanks racobb. I'm just concerned about the polarity of the CT's reason I want to see a "standard" metering wiring diagram.

capuchi
racobb (Electrical)
26 Mar 09 7:57
Have you tried to google the meter mfg. or contact them by phone?  I guess the only "standard" will be to connect the marked terminal of the ct secondary to the + or HI meter input, then be sure you only have 1 ground point on the ct secondary.

Also recommend shorting switches for the ct circuits and disconnects/fusing for the voltage inputs if you don't already have them.

Is it an analog or digital display?  Who is the mfg. and what is the catalog number/type of meter?

Alan

Democracy is two wolves and a sheep deciding what to have for dinner.  Liberty is a well armed sheep!
Ben Franklin

capuchi (Electrical) (OP)
26 Mar 09 10:28
I don't have the meters yet. I'm still undecided if I will go for digital or just analog for the meantime due to economic considerations. Big difference in price between analog and digital meters. I know it will a lot easier if I go for digital coz no need for voltmeter and ammeter switches. Am I right?

capuchi    
racobb (Electrical)
26 Mar 09 11:41
Or you could use 2 single phase analog units of each type without switches, but there is another increase to save the cost of switches.  I am assuming you only have 2 ct's and pt's available on the 3 wire metered service.  Long term, I would use an electronic power meter for the added info.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner.  Liberty is a well armed sheep!
Ben Franklin

capuchi (Electrical) (OP)
28 Mar 09 10:36
that's right there are 2 CT's and 2 PT's since the kwhr meter is a 2-stator type. for long term the digital power meter is the best option.

thanks for the suggestions.

capuchi

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