GE P642 User Manual

Setting in GROUP 1 SYSTEM CONFIG Value
TV Vector Group 0
TV Connection Y-Wye
TV Grounding Ungrounded
TV Nominal 230.0 kV
TV rating 175.0 MVA
Phase Sequence Standard ABC
VT Reversal No Swap
CT1 Reversal No Swap
CT2 Reversal No Swap
CT3 Reversal No Swap
Vector correction and zero sequence filtering are automatically performed by virtue of the L
V Vector Group setting
and the HV Grounding and LV Grounding settings.
It is preferable to have the ratio correction factors equal to or close to 1.
Applying Kirchoff's law, assume that the full load current is flowing, that an equivalent source is connected to the
HV winding and that an equivalent load is connected to the LV winding. The current distribution is as follows:
I
S
V
A
I
S
V
FLC HV
nom HV
FLC LV
nom LV
−
−
= =
×
× ×
=
= =
3
175 10
3 230 10
439
3
1
6
3
,
,
775 10
3 115 10
878
6
3
×
× ×
= A
A
B
C
175/175/30 MVA
230 /115/13.8 kV
YNynd1
230 kV - +5%/-15% - 19 taps
1200:5
1200:5
Equivalent
load
a
b
c
1200:5
439 Ð0°
439 Ð-120°
439 Ð120°
878 Ð0°
878 Ð-120°
878 Ð-240°
439 Ð0°
439 Ð-120°
439 Ð-120°
V03118
Figure 55: Unloaded delta – current distribution
The r
eference power is set to 175 MVA and the nominal voltage in HV, LV and TV windings is set to 230 kV. In this
application, you do not need to consider the mid tap voltage, even though, there is an on load tap changer on the
HV side.
The device calculates the ratio correction factors as follows:
K K K
I
S
V
amp T CT amp T CT amp T CT
nom T CT
ref
nom
, , ,
,
1 2 3
1
3
1200
175 1
= = = =
× 00
3 230 10
2 73
6
3
× ×
= .
P64x Chapter 6 - Transformer Differential Protection
P64x-TM-EN-1.3 129

GE P642 Specifications

General

Brand	GE
Model	P642
Category	Relays
Language	English