ABB REG316 4 Series Operating Instructions Manual page 101

REG 316*4 1MRB520049-Uen / Rev. F
Compensating any difference between the rated currents of c.t.
I and protected unit I
N1
the aid of the reference value of the A/D channel or by correcting
the overcurrent setting.
For example, for I
GN
pick-up current of 1.5 I
I
800
GN
=
1 5 . 1 5 .
I 1000
N 1
CurrentInp
An interposing c.t. in the input is essential for current settings
lower than < 0.2 I .
N
Delay
The delay is used to achieve discrimination of the overcurrent
function. It is set according to the grading table for all the over-
current units on the power system. The zone of protection of our
overcurrent function extends to the location of the next down-
stream overcurrent relay.
Should the downstream relay fail to clear a fault, the overcurrent
function trips slightly later as a back-up protection.
Setting MaxMin
This parameter enables the following operating modes to be
selected:
·
MIN (3ph): Pick-up when the highest phase current also
falls below the setting. This setting is not per-
mitted for single-phase measurement.
·
MIN (1ph): Pick-up when the lowest phase current falls
below the setting.
·
MAX (3ph): Pick-up when the lowest phase current also
exceeds the setting. This setting is not permit-
ted for single-phase measurement.
·
MAX (1ph): Pick-up when the highest phase current ex-
ceeds the setting.
·
MAX-Inrush: Blocking of inrush currents when a phase
current exceeds the setting.
is recommended. This is achieved with
GN
= 800 A and I = 1000 A, the setting for a
N1
= 1200 A would have to be
GN
A
=
1 2 .
A
ABB Switzerland Ltd
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