Vanguard Instruments Company ATRT-03, User Manual

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REV 2 ATRT-03, ATRT-03A, AND ATRT-03B USER’S MANUAL
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APPENDIX A – TRANSFORMER VECTOR GROUP CODES
Utility power transformers manufactured in accordance with IEC specifications have a Rating
Plate attached in a visible location. This plate contains a list of the transformer's configuration
and operating specifications. One such rating is the winding configuration and phase-
displacement code. This code follows a convention that comprises letter and number sets that
denote three-phase winding configurations (i.e., Wye, delta, or zig-zag). Letter symbols for the
different windings are noted in descending order of their rated voltages. That is, symbols
denoting higher voltage ratings will be in upper-case letters and symbols denoting lower or
intermediate voltage ratings will be in lower-case letters. If the neutral point of either a wye or
zig-zag winding is brought out, the indication will be an N (high voltage) or n (lower voltage).
The end numeral is a 300 multiplier that indicates phase lag between windings.
Accordingly, the following standard practice applies:
Wye (or star) = Y (high voltage) or y (low voltage)
Delta = D (high voltage) or d (low voltage)
Zig-zag = Z (high voltage) or z (low voltage)
For example, Dyn11 decodes as follows:
D indicates that the high-voltage windings are connected in a Delta configuration
(Since delta windings do not have a neutral point, the N never appears after a D).
y indicates that the lower voltage winding is in a wye (or star) configuration.
n indicates that the lower voltage windings have the neutral point brought out.
11 indicates a phase-displacement lag of 330 degrees between the Wye and the Delta
winding.