ANSI/IEEE Std C57.13-1993<br>
Standard accuracy class for metering service and corresponding limits of transformer correction factor [0.6 to 1.0 power factor (lagging) of metered load]<br>
7.2 Standard burdens<br>
Table 15 (Standard burdens for voltage transformers)<br>
<br>
Characteristics on standard burdens<br>
<br>
Designation / VA<br>
W / 12.5<br>
X / 25<br>
M / 35<br>
Y / 75<br>
Z / 200<br>
ZZ / 400<br>
<br>
<br>
7.3 Accuracy ratings<br>
A voltage transformer shall be assigned an accuracy rating for each of the standard burdens for which it is rated. For example, an accuracy rating might be 0.3W and X, 0.6Y, 1.2Z.
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