CT meters

[Edd]

Hi Guys,
Next week I'm fitting four 3 phase check meters, these will be done with CT's. it say in the info that each phase also has a fused down supply to 4 separate terminals L1 L2 L3 and N are these just to supply the meter or do they use this in some way to measure the current.
I ask as i would like to only fit a 3 Phase MCB to supply all 3 meters in Parallel, and hope its just the CT's that measure the current.
Thanks Guys, and girls

 

[Outspoken]

Edd, I think this will assist better than words mate.

 

[Edd]

Thanks for that. my wonder was can i supply all 4 meters from one set of fuses? if they are just used for supplying the meter then I can see no problem, but if they are used insome way to measure the current then i will end up with 12-16 inline fuses!

 

[Outspoken]

Thanks for that. my wonder was can i supply all 4 meters from one set of fuses? if they are just used for supplying the meter then I can see no problem, but if they are used insome way to measure the current then i will end up with 12-16 inline fuses!

Ed, Normally each CT has it's own single phase MCB, clearly labeled. However in the last couple of years I have seen a number of people put these on 3 phase MCB's and a Neutral Block. The fact is the Neutral can carry a significant amount of energy all by itself in large installations so this should be protected, because it is actually protecting the METER and not the CT. I do not like the 3P+N approach and when this was done recently in our DC new modules we insisted that Prism change this to individual protective devices.

 

[Knobhead]

The voltage is a reference for the meter to calculate KWHr I*V.

You could put all four meters on one MCB + the neutral connection, I wouldn’t be happy with you if you did. All our meters were individually fused at 2A also a neutral test link fitted. It’s a standard practice for metering.

PS it used to take one of the mates a full day to read all the meters on our section alone.

 

[Outspoken]

Edd, I should also point out that some of the new meters also require a 230V single phase supply (usually via a 12V Tx) to allow the meter enough power to run network systems for remote monitoring, alarms etc..

 

[Knobhead]

Unless I’ve totally misread Edd’s OP the meter requires a 3Ph+N reference supply. NOT 12V.

Using current measurement only for metering is possible but not reliable or accurate!

 

[Edd]

Unless I’ve totally misread Edd’s OP the meter requires a 3Ph+N reference supply. NOT 12V.

Using current measurement for metering is possible but not reliable or accurate!

Thats right, As with the above I'm now going to fuse each meter separately, i'm making a box up as I type!

Thanks again

 

[Outspoken]

Unless I’ve totally misread Edd’s OP the meter requires a 3Ph+N reference supply. NOT 12V.

Using current measurement only for metering is possible but not reliable or accurate!

Tony, you're well behind the curve on technology chap. For a start all 3 Phase meters used internal CT's for metering anyway, but many modern electronic ones, especially check meters, take their power from a reference voltage from the CT, this is also why many newer ones also require a separate 12V/230V/400V supply as this reference voltage is unable to supply power to run the meter services for alarms, network connections, logging etc.


This is not true for all of course, there are many that are designed for direct input of 3P services.

Here is the ones recently installed in the DC.

LINK

 

[Knobhead]

Tony, you're well behind the curve on technology chap. For a start all 3 Phase meters used internal CT's for metering anyway, but many modern electronic ones, especially check meters, take their power from a reference voltage from the CT, this is also why many newer ones also require a separate 12V/230V/400V supply as this reference voltage is unable to supply power to run the meter services for alarms, network connections, logging etc.


This is not true for all of course, there are many that are designed for direct input of 3P services.

Here is the ones recently installed in the DC.

LINK

I may be behind the times, but I read Edd’s OP!