28
Instruction Leaflet
I. L. 29-888B
Effective July 2011
Instructions for Digitrip RMS 810 Trip Unit
eaton corporation
www.eaton.com
appenDiX a: Zone lnterlocking
Assume a ground fault of 2000 Amperes occurs and refer to Figure
A .1 .
CASE 1e: There is no Zone Selective Interlocking (standard time
delay coordination is used).
Fault 3
The branch breaker will trip clearing the fault in 0 .1 s .
Fault 2
The feeder breaker will trip clearing the fault in 0 .3 s .
Fault 1
The breaker will trip clearing the fault in 0 .5 s .
CASE 2e: There is Zone Selective lnterlocking.
Fault 3
The branch breaker trip unit will initiate the trip in 0 .03 s to clear the
fault and Z3 will send an interlocking signal to the Z2 trip unit; and Z2
will send an interlocking signal to Z1 .
Z1 and Z2 trip units will begin to time out, and in the event that the
branch breaker Z3 would not clear the fault, the feeder breaker Z2
will clear the fault in 0 .3 s (as above) . Similarly, in the event that the
feeder breaker Z2 would not clear the fault, the main breaker Z1 will
clear the fault in 0 .5 s (as above) .
Fault 2
The feeder breaker trip unit will initiate the trip in 0 .03 s to clear
the fault; and Z2 will send an interlocking signal to the Z1 trip unit .
Z1 trip unit will begin to time out, and in the event that the feeder
breaker Z2 would not clear the fault, the main breaker Z1 will clear
the fault in 0 .5 s (as above) .
Fault 1
There are no interlocking signals . The main breaker trip unit will initi-
ate the trip in 0 .03 s .
Figure A .2 presents a Zone Selective lnterlocking connection dia-
gram for a system with two main breakers from incoming sources
and a bus tie breaker . Note the blocking diode D1 is needed so that
the feeder breakers can send interlocking signals to both the main
and tie breakers, without having the tie breaker send itself an inter-
locking signal .
Figure A.1 Typical Zone Interlocking (Ground Fault Protection).
otese:
N
A1: Wiring to be twisted pair of AWG No . 14 to AWG No . 20 . Route
Zone lnterlocking wiring separate from power conductors . DO
NOT GROUND any Zone Interlock Wiring .
A2: The maximum distance between first and last zone is 250 feet
(110 m) .
A3: A Maximum of 20 breakers may be connected in parallel in one
Zone .
Figure A.2 Typical Zone Interlocking Connections with Two Main
Breakers (M1, M2) and a Tie Breaker (T) (Short Delay Protection).
I
3200 A
)
Main
1
0.5 Sec
Z2
0.1 Sec
1200 A
100 A
Zo
ne
3
Legend
=Common (Ungrounded)
=Short Delay Output Signal
to Higher Level Zone
= Short Delay Input Signal
from Lower Level Zone
=Ground Output Signal
to Higher Level Zone
=Ground lnput Signal
from Lower Level Zone
= Fault at Location 2
F21
0.1 Sec
0.1 Sec
0.1 Sec
0.1 Sec
0.1 Sec
M2
C
C
SO
SO
-
-
F12
F22
F23
0.5 Sec
0.5 Sec
SI
SO
SI
0.3 Sec
1N4004
D1
