Figure 9. Series NRX RF Frame Neutral Sensor
Figure 10. Series NRX NF Frame Neutral Sensor
Zone selective interlocking (optional)
The zone selective interlocking function is an option when
ordering the Series NRX circuit breaker. The circuit breakers
that are built with the zone interlocking function ordered will
have three wires (Zout, Zcom, Zin) connected to secondary
contacts (27, 28, 29). These contacts can then be wired for
zone interlocking to other circuit breakers above and below in
the other zones.
Table 10. Series NRX/Digitrip Ground Fault Sensing Modes
Ground (Earth)
Sensing Method
Sensor Style
IZMX Type Code
Breaker Secondary
Contacts - if no
CAM module
Optional
CAM Module
Jumper Position
Neutral Input
Contacts
Ground Sensor
Input Contacts
Residual NF Frame
5721B76G12
IZMX-CT16-N
No jumper
Disable position
15 ,16
-
Residual RF Frame
70C1718G11
IZMX-CT40-N
No jumper
Disable position
15 ,16
-
Source ground
70C1527G14
IZMX-CT-NGS
Jumper 19 to 20
Enable position
-
17 ,18
Zero sequence
70C1527G14
IZMX-CT-NGS
Jumper 19 to 20
Enable position
-
17 ,18
ote:
N
This information applies to only trip units with ground fault or ground protection.
Zone selective interlocking is available on the SHORT delay and
GROUND fault protection functions. The zone interlocking, if
supplied, is wired via a single set of three wires labeled Zone
In (Zin) and Zone Out (Zout) along with a zone common wire.
The zone selective interlocking function has combined the logic
interlocking of SHORT delay and GROUND fault in one signal.
A zone out signal is sent whenever the ground fault pickup is
exceeded or when the short delay value of 2 x (Ir) is exceeded.
This provides maximum selectivity for coordination with larger
upstream circuit breakers. Zone selective interlocking provides
the fastest possible tripping for faults within the zone of
protection of the circuit breaker and yet also provides positive
coordination among all circuit breakers in the system (mains,
ties, feeders, and downstream circuit breakers). When zone
interlocking is employed, a fault within the zone of protection of
the breaker will:
• Trip the affected circuit breaker immediately.
• Send a signal to upstream Digitrip units to restrain from
tripping immediately. The restraining signal causes the
upstream circuit breakers to follow their set coordination
time delays, so that the service is interrupted to the
isolated fault area only while the fault is cleared in the
shortest time possible.
For an example of how zone selective interlocking may be used,
see
Appendix A: Zone Selective Interlocking Examples
of
this manual.
Diagnostics indicator—circuit breaker/trip unit
The Digitrip trip unit has LEDs for diagnostic reasons. The
Status LED is bicolored. A normally powered trip unit will flash
the green status at a 1 second repetition rate. The Status LED
will flash red and orange if a problem is encountered in any of
the following scenarios:
• Internal self test problem
• MCR auxiliary switch or circuit breaker mechanism is in an
improper state
• Trip actuator (TA) coil circuit is open
This LED status is indication of an issue that needs attention
as soon as possible (see
Appendix B: Troubleshooting
). In
addition, the Digitrip units provide a relay contact that can
provide a diagnostic alarm signal externally.
18
EATON
www.eaton.com
Operating Manual for Series NRX
Digitrip Trip Units 1150 / 1150i
Effective September 2013
Instructional Leaflet IL01301064E
