SSLA
Electrical
- Dec 6, 2004
- 37
Folks:
ANSI has defined a number of standard burdens (W,X,Y,Z,ZZ and sometimes M). Usually a VT nameplate will list all that it can support e.g. 0.3WXY for a 75 VA unit and 0.3WXYZ for a 200 VA unit.
But what does it mean if the name plate on a VT with one secondary lists only one value, e.g. 0.3Z? I have always assumed that meant it was also passed factory tests at all of the lesser burdens, i.e. 0.3Z would mean 0.3 class accuracy at W,X and Y burdens as well.
Am I right? Or can accuracy at the lesser burdens exceed the limits of the 0.3 (in this case) class?
I've had a look in the ANSI, IEEE standards and Handbook for Electricity Metering but cannot find a clear reference to what the single rating means.
Can anyone help?
ANSI has defined a number of standard burdens (W,X,Y,Z,ZZ and sometimes M). Usually a VT nameplate will list all that it can support e.g. 0.3WXY for a 75 VA unit and 0.3WXYZ for a 200 VA unit.
But what does it mean if the name plate on a VT with one secondary lists only one value, e.g. 0.3Z? I have always assumed that meant it was also passed factory tests at all of the lesser burdens, i.e. 0.3Z would mean 0.3 class accuracy at W,X and Y burdens as well.
Am I right? Or can accuracy at the lesser burdens exceed the limits of the 0.3 (in this case) class?
I've had a look in the ANSI, IEEE standards and Handbook for Electricity Metering but cannot find a clear reference to what the single rating means.
Can anyone help?