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Functions and
characteristics
Special applications
Generator protection
with Micrologic 2.2-G
Micrologic G trip units are used for the
protection of systems supplied by
generators or comprising long cable
lengths. They can be mounted on all
Compact NSX100/160/250 circuit breakers.
With extensive setting possibilities,
Micrologic 5 offers the same functions from
100 to 630 A.
A thermal-magnetic trip unit is also available
for the NSX100 (see page A-15).
Circuit breakers equipped with Micrologic G trip units protect systems supplied by
generators (lower short-circuit currents than with transformers) and distribution
systems with long cable lengths (fault currents limited by the impedance of the
cable).
Protection
……………………………………………
Settings are made using the ad
j
ustment dials
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Overloads: Long-time protection (Ir)
Inverse-time thermal protection against overloads with an ad
j
ustable current pick-up
Ir and a very short, non-ad
j
ustable time delay
tr
(15 seconds for 1.5 x Ir).
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Short-circuit protection with an ad
j
ustable pick-up
Isd
, delayed 200 ms, in
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Short-circuits: Non-adjustable instantaneous protection (li)
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protection.
Neutral protection
On 3-pole circuit breakers, neutral protection is not possible.
b
On four-pole circuit breakers, neutral protection may be set using a three-position
b
switch:
4P 3D: neutral unprotected
v
4P 3D + N/2: neutral protection at half the value of the phase pick-up, i.e. 0.5 x Ir
v
4P 4D: neutral fully protected at Ir.
v
Indications
…………………………………………
Front indications
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b
event of a fault.
Orange overload pre-alarm LED: steady on when I > 90 % Ir
b
Red overload LED: steady on when I > 105 % Ir
b
Remote indications
An SDx relay module installed inside the circuit breaker can be used to remote the
overload-trip signal.
This module receives the signal from the Micrologic electronic trip unit via an optical
link and makes it available on the terminal block. The signal is cleared when the
circuit breaker is closed.
The module is described in detail in the section dealing with accessories.
PB103377
SDx remote indication relay module
with its terminal block.
DB112118
A-48
559E1600.indd
version: 1.0