Masterpact ® ci rcuit breaker
control u n its
neutral sensor
G round-fault protection may be applied on
304W or 303W circuits. On 304W circuits
an external neutral sensor must be used.
This neutral current sensor must have the
same ampere rating as the circuit breaker.
neutral
main circuit breaker
neutral sensor
zone-selective interlocking
feeder
circuit
breaker
external neutral sensor
M P 1 001A.O
Note:
#1 8 to #1 4 AWG cables - max. length 60 ft./18.3 m
MP1 002A.O
Zone-selective Interlocking
(ZSI)
Option Z on the STR 58U trip unit provides
selective interlocking on short time or ground
fault.
A pilot wire links several trip units in the
distribution network, as shown in the
opposite figure.
In the event of a fault, the trip unit will obey
the pre-set delay only if receiving a signal
from the downstream unit. If not receiving a
signal, the tripping will be instantaneous.
Therefore, the fault is cleared
instantaneously by the nearest circuit
breaker:
the thermal stresses (l"t) in the network are
minimized, without any effect on the correct
time delay coordination in the installation.
fault 1
Circuit breaker A will clear the fault
instantaneously, regardless of its time delay
setting.
fault 2
Circuit breaker B will inform upstream
circuit breaker A that it is clearing the fault
and will prevent it from tripping
instantaneously.
Circuit breaker A will trip at the end of its
time delay setting if the fault is not cleared
during this time.
Note:
•
circuit breaker terminals are delivered
with "in" terminals jumpered. Remove the
jumper when interlocking with a downstream
circuit breaker.
•
the Masterpact circuit breaker may also be
interlocked with Compact CK type molded
case circuit breakers with ZSI option.
•
do not ground.
1 0
cable size
max. length
wiring
no. of circuit
breakers
MP1 003A.O
# 1 8-#1 4 AWG/1 .5mm'
60 11./1 8.3 m
twisted in pairs
one turn per 4 in./1 0 em
upstream: 2
downstream: no limit
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