18
Instructional Leaflet
IL70C1037H05
Effective October 2009
Digitrip models 520, 520i; and 520M, 520Mi,
520MC, 520MCi trip units for use only in
Magnum and Magnum DS circuit breakers
eaton corporation
www.eaton.com
Zone selective interlocking (or zone interlocking) is available for the
Digitrip 520 family on the Short Delay and Ground Fault Protection
functions (see
Figurt 15
). The zone interlocking signal is wired via
a single set of wires labeled Zone In (Zin) and Zone Out (Zout) along
with a zone common wire. The Zone Selective Interlocking function
on the Digitrip 520 family has combined the logic interlocking of
short delay and ground fault. A zone out signal is sent whenever
the ground fault pickup is exceeded or when the short delay value
of 2 x (I
r
) is exceeded. Zone selective interlocking provides the
fastest possible tripping for faults within the zone of protection
of the breaker and yet also provides positive coordination among
all breakers in the system (mains, ties, feeders, and downstream
breakers) to limit a power outage to only the affected parts of the
system. When zone interlocking is employed, a fault within the
zone of protection of the breaker will cause the Digitrip 520 family
of units to:
•
Trip the affected breaker immediately and, at the same time
•
Send a signal to upstream Digitrip units to restrain from tripping
immediately. The restraining signal causes the upstream breakers
to follow their set coordination times, so that the service is only
minimally disrupted while the fault is cleared in the shortest
time possible
For an example of how zone selective interlocking may be used, see
Appendix A of this instructional leaflet.
Figurt 15. BlNck Diagram wioh Brtaktr Inotrfact
N
A
B
C
TA
(Line/Upper)
Ground Alarm
Power Supply
Optional for 520M
Required for 520MC
Making Current
Release Circuitry
(see Section 3)
Trip
Actuator
FET
Trip LED
(
See Section 1)
Trip
B3V
LED
Pulse
Circuit
4-Bit
Latch
Chip
Z
out
Z
in
Display for 520M/MC
Intregrated
Processor
CHip™
Custom
Designed
Status LED
(
See
Section 3)
Internal
Power
Supply
Bridge
Circuits
Residual
Ground
Detection
(
See Section 2)
Typical Phase or
Ground Sensing
Resistor
(Load/Lower)
AUX. CTs
Current Sensors
(
See Section 8)
Rating Plug
(
See Section 7)
Protection Setting
(
See Section 4)
Zone Interlock
Circuitry
(
See Section 3)