ABB REG316 4 Series - Page 210

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-172
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
N
:
P
UI
S
UI
N
NN
GN
NN
´
=
´´
3
11
SUI
PS
GN GN GN
GN GN GN
=´ ´
=´
3
cos
j
where:
S
GN
, P
GN
, U
GN
, I
GN
, cos j
GN
: ratings of the protected unit
U
N1
, I
N1
: primary v.t. and c.t. ratings
P
N
, U
N
, I
N
: protection ratings.
Example 1
Generator: 96 MVA, 13,8 kV, 4 kA, cosj = 0,8
V.t’s/c.t’s:
14 4
3
100
3
55
.
;kV V kA A
Protection: 100 V; 5 A
Reverse power: 0.5 % P
GN
Alternative 1: No modification of P
N
Settings:
Reference power
P
UI
N
NN
´
=
10.
Reverse power:
P
P
UI
UI
N
GN GN
NN
GN
=
´
´
=
´
´
=0005 0005
13 8 4
14 4 5
08 0003
11
.cos.
.
.
..j