Specifications

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Doc. no.
Model
Apparatus
Scale
Page No
1SDH000460R0002
L5439
12.5.3. Changing protection functions
This paragraph enables the user to set the protection functions implemented in the PR121/P unit. Only the setting methods and
which values can be selected are explained here. For all other information on the technical characteristics of the protection func-
tions, see par. 12.2.5.
WARNING: No parameter settings can be made if the PR121/P unit is in alarm conditions.
12.5.3.1. Example of settings
In the diagrams on the front plate (see par. 12.5) relating to the settings, the position of the DIP switch is indicated by the
white part.
An example of how to set the DIP switch for the protection function L is given below, where I
n
= 2000A:
Frequency
60 Hz
50 Hz
I
n
N
Frequency = 50 Hz
I
n
N = 50%
x I
n
t1 = 3s@2.550A (3*I
1
)I1 = 0,4 + 0,025 x In
I1 = 850A
+
t
1
I
1
x 3 I
1
A faulty configuration of the dip-switches generates a “Settings Inconsistency” error which is signalled by means of a LED (see
par. 12.7.1).
Comply with this formula: I1<I2<I3.
E.g.: if I1 = 1In and I2 = 1In, the relay signals a “Settings Inconsistency” error. The same occurs when I2 = 5In and I3 = 4In.
12.5.4. PR121/P default settings
The PR121/P is supplied by ABB SACE with the following preset parameters:
# Protection Threshold Time
1 L 1 In 144 s
2 S Off 0,1 s
3 I 4 In --
4 G Off 0,1 s
5 Mains frequency 50 Hz
6 Neutral sel *
Note:
* = Off for 3-pole versions
* = 50% for 4-pole versions
* = 100% for full-size versions
12.6. Operating instructions / Operation in service
12.6.1. Neutral adjustment
The neutral protection is normally set to a current value 50% of the adjustment made on the phases.
In some installations, where particularly high harmonics occur, the current circulating on the neutral may be higher than that of
the phases.
In the SACE PR121/P release, this protection can be set for the following values: I
n
N =Off - 50% - 100% - 200% * I
n
.
WARNING: With three-pole circuit-breakers, without external neutral sensor, the adjustment of the neutral must
be set to OFF.
12.6.2. Neutral adjustment specifications
To adjust neutral (I
n
N) comply with the following formula: I
1
x I
n
NIu.
With a 4-pole CB, this setting is checked by the relay which signals any failure by means of a LED (see par. 12.7.1) and indepen-
dently adjusts this parameter, restoring it to within the accepted limits.
With a 3-pole CB, with external neutral, the relay performs no checks and setting is to be done by user.
E.g.: With E1B800 CB having a 400A Rating Plug, Iu = 800A and I1 = 1In, I
n
N adjustment may be: 50-100-200% .
With E1B800 CB having a 800A Rating Plug, Iu = 800A and I1 = 1In I
n
N adjustment may be: 50-100%.
Note 1: I
1
=1I
n
setting is intended as the maximum adjustment of the protection against overloads. Actual maximum allowable adjustment must take into
account any temperature derating, terminals used and altitude, or In (rating plug)≤ 50% of circuit breaker size.
WARNING: Failure to comply with the setting limits for “I
1
” and “I
n
N” can damage the circuit-breaker, with con-
sequent risks to the operator too.