Page 637 - Industrial Power Engineering and Applications Handbook

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Surges on one phase only Surges of opposite polarity on two phases
Transformer connections
V,=lp.u, v,= v,=o v, = 1 p.u, vy = - 1 p.u, vb = 0
HV LV Tertiary HV Value of rfor LV HV Value of rfor LV
winding winding winding winding winding winding winding
/L 0 /A

0 - 0 0 AlS - -1
-1
-
1
v( Q 0 - 0 -113 -113 0 4b.S-

-1
-
I L
m
A 0 - 0 Oq-m 0 - -1

L
A

-
-113 ,x -113 0 -1
-3-,. 0 0 - -1
0

A Oa
0 0 -1ld3 0 -1 fi a -21d3 lN3
4 0 L

f lId3

0 x 0 -1143 -1 ,Id3-+ -2113
x

A
0
+bo * 0
-1143
.
A A
-113q 'I3
O -1 G .a' -1
-113
g - Grounded star Delta connected windings
i - isolated star

A Star connected windings "& Zig-zag windings
b y
Figure 18.14 Values of factor 'r'