ABB REG316 4 Series Operating Instructions Manual page 127

REG 316*4 1MRB520049-Uen / Rev. F
Where the rated c.t. current I
of the protected unit, compensating the measurement to achieve
a match is recommended. This is done by correcting either the
reference value of the A/D input or the setting.
For example, assuming I
to pick up at 1.5 I
GN
I
GN
=
1 5 , 1 5 ,
I 1000
N 1
Characteristic angle
Determining the phase-angle of the current provides an addi-
tional criterion for preserving discrimination compared with non-
directional overcurrent protection. The directional sensitivity is
± 180° in relation to the reference voltage. This is illustrated in the
following diagrams. The angles given apply for connection ac-
cording to the connections in
I
R
j
w
U
R
U U
TR RS
U
U
T S
U
ST
a)
j ' = phase-angle between current and voltage
(positive angle)
a = Characteristic angle
L = Border line between operating and restraint areas
a) Definition of current
and voltage
Fig. 3.5.7.2 Vector diagram for a fault in the forwards direction on
R phase
differs from the rated current I
N1
= 800 A and I
GN
= 1200 A would be
800 A
=
1 2 ,
A
Section 12.
L
Restraint:
cos ( - ) = neg. j a '
b)
b) Operating characteristic
ABB Switzerland Ltd
= 1000 A, the setting
N1
I
R
a = 45°
j'
U
ST
Operation:
j a
cos ( - ) = pos. '
L
HEST 005 001 C
GN
3-89