energy meter

[salem]

an energy meter (kWhr) with the following name plate spec.

Current 5000:1 A
Voltage 10.5 kV/sqrt(3) : 100V/sqrt(3)

is fed from voltage and current transformers with following spec.

VT :10.5 kV/sqrt(3) : 110V/sqrt(3)
CT :5000:1 A

what will be the error in the meter reading due to voltage difference

 

[waross]

110/100
respectfully

 

[scottf]

Are you sure that the nameplate data is the same as the multiplier being used?

Multiplier would generally be CT ratio times VT ratio.

 

[salem]

scottf,

the case is that meter and VT secondary spec. are different!

 

[waross]

From your post, I must assume that your meter has a preprogrammed multiplier and reads directly in KWHr consumed, without the need for a multiplier. If this is the case, I have given your error factor.
respectfully

 

[salem]

yes waross, it is an electromechanical meter with preprogrammed multiplier (VT,CT)

 

[tinfoil]

To elaborate on waross's answer, the meter is expecting a multiplier due to external instrument xmfrs of 5000/1 * 10500/100 or 545,000

The actual installed IT xmfrs are providing 5000/1 * 10500/110, or a multiplier of 477,272.7.

So the meter is observing 545,000/ 477,272 of the anticipated energy (i.e the secondary amounts are LARGER than expected), which obviously simplifies to 110/100, or 10% too much.

edit: I missed the sqrt(3) bit in your OP, but as it applies to both VTs, the ratio still holds. Just divide my multipliers by sqrt(3) if you need the exact numbers for some reason.