Figure 53: P645 Used To Protect An Autotransformer With Loaded Delta Winding - GE P642 Technical Manual

P64x
800:5
HV
A
B
C
V03116

Figure 53: P645 used to protect an autotransformer with loaded delta winding

Since the transformer has an on load tap changer on the HV side, the nominal voltage of the HV winding must be
set to the mid tap voltage level. According to the nameplate data, the mid tap voltage is 218.5 kV. The mid tap
voltage can also be calculated as follows:
Mid tap voltage =
Set the following parameters in the SYSTEM CONFIG column:
Setting in GROUP 1 SYSTEM CONFIG
Winding Config
Winding Type
HV CT Terminals
LV CT Terminals
TV CT Terminals
Ref Power S
Ref Vector Group
P64x-TM-EN-1.3
175/175/30 MVA
230/115/13.8 kV
YNynd1
+5% / -15%
19 taps
Protected zone
a
b
c
LV
1200:5
B
Phase & amplitude
Correction
+
Zero sequence filtering
D
( 5 15 )
−
100
+
2
230 218 5
× =
100
Chapter 6 - Transformer Differential Protection
Earthing
transformer
B
Phase & amplitude
Correction
B B
+
Zero sequence filtering
B B
B
Phase & amplitude
Correction
B
+
Zero sequence filtering
B
D D
. kV
HV+LV+TV
Auto
00001
10000
00100
175.00 MVA
0
TV
2000:5
a
b
c
P645
Value
125