First symbol/symbols, capital letters: HV winding connection.
Second symbol/symbols, small letters: LV winding connection.
Third symbol, number: Phase displacement expressed as the
clock hour number.
Winding connection designations
High Voltage Always capital letters
Delta - D
Star - S
Interconnected star - Z
Neutral brought out - N
Low voltage Always small letters
Delta - d
Star - s
Interconnected star - z
Neutral brought out - n
Phase rotation is always anti-clockwise. (international
Use the hour indicator as the indicating phase displacement
angle. Because there are 12 hours on a clock, and a circle
consists out of 360°, each hour represents 30°.
Thus 1 = 30°, 2 = 60°, 3 = 90°, 6 = 180° and 12 = 0° or 360°.
The minute hand is set on 12 o'clock and replaces the line
to neutral voltage (sometimes imaginary) of the HV winding.
This position is always the reference point.
Because rotation is anti-clockwise, 1 = 30° lagging (LV lags
HV with 30°)and 11 = 330° lagging or 30° leading (LV leads
HV with 30°)
Delta connected HV winding, star connected LV winding with
neutral brought out, LV is leading HV with 30°
Dyn11 is vector group notation of tansformer.It means LV
winding,which is star connected (written in small letters
means LV side and vice versa)is 30 degrees lagging by HV
winding which is delta connected.In India we go for +-30
deg connection of transformer.
D = Delta connection at primary,y = Star connection at
secondary and n = neutral point connected at secondary.
Dyn 11 means that the voltage of the secondary star winding
lead the primary phase voltage by 30 degree and it
corresponds to 11 o'clock.
1.where in India the maximum transmission voltage is operated?
2.what the methods are used to cool down the
transformer?give the specific ratings of the transformer &
specific cooling process.
3.how zero & negative sequence reactances are formed in a
rotating machine when fault occur in the system?