ABB REG316 4 Series Operating Instructions Manual page 210

ABB Switzerland Ltd
Determining the settings
Where the rated currents and possibly also rated voltages of
c.t's, v.t's and the protected unit differ, it is of advantage to refer
the setting to the rated power of the protected unit. This neces-
sitates modifying the sensitivity using the setting for PN.
Setting the reference power P
S
P
N GN
=
´
U I ´
3 U
N N
N 1
where:
S , P , U , I
GN GN GN GN
U , I :
N1 N1
P , U , I :
N N N
Example 1
Generator: 96 MVA, 13,8 kV,
14 4
V.t's/c.t's:
Protection: 100 V; 5 A
Reverse power: 0.5 % P
Alternative 1: No modification of P
Settings:
Reference power
U
Reverse power:
´
U I
P
GN GN
=
0 005 .
´
P U I
N N 1 N 1
3-172
REG 316*4 1MRB520049-Uen / Rev. F
:
N
S
GN
´
I
N 1
P
GN
, cos j
: ratings of the protected unit
GN
primary v.t. and c.t. ratings
protection ratings.
. 100
kV V ;
3 3
GN
P
N
= 10 .
´
I
N N
13 8 4
j =
cos 0 005 .
GN
14 4 5
= ´ ´
3 U I
GN GN
= ´ cos j
S
GN GN
cos j = 0,8
4 kA,
5 kA 5 A
N
´
.
=
0 8 0 003 . .
´
.