HV Potential Transformers 4

[shocker23]

I have noticed that the accuracy of potential or current transformers used for metering is expressed "0.3 WXYZ". What do the letters represent? this could be on a 800:5 1600:5...etc.

Shocker23

 

[slavag]

Hi.
800:5 it's a CT ratio.
You wrote: accuracy 0.3 it's class , and letters it's burden
according to IEEE C57.13, 0.3 it's for revenue meter.
for example
W=12.5VA
X=25VA
Y=75VA and Z=200VA.
Hope it help.
Best Regards.
Slava

 

[scottf]

You've got something confused.

Accuracy/burdens for PTs is written like 0.3 WXYZ. The "0.3" is the accuracy class and the letters stand for burdens as noted above.

0.3 WXYZ, means that the PT will meet the defined 0.3 class from 0 to 200VA (Z). It means that the PT will be +/-0.3% accurate between 90-110% rated voltage when loaded to a max burden of 200VA.

A CT accuracy/burden would be written like 0.3B1.8, with the "0.3" being the accuracy class and "1.8" standing for 1.8 ohms burden. It means the CT is guaranteed to be +/-0.3% accurate from rated current up to the rating factor (max current) and +/-0.6% accurate from 10%rated to rated current, when loaded up to the max burden of 1.8 ohms.