10
Instruction Leaflet
I. L. 29-889B
Effective June 2011
Instructions for Digitrip RMS 910 Trip Unit
eaton corporation
www.eaton.com
1.1.4 OVERRIDE (Fixed Instantaneous)
Each Digitrip RMS 910 Trip Unit has a Fixed Instantaneous "Override"
analog trip circuit pre-set to a value no greater than the short-time
withstand current rating of the circuit breaker in which the Trip Unit
is installed . Since the specific values vary for different circuit break-
er types and ratings, refer to time-current curves, listed in Section 6,
for the values applicable to your breaker . If the breaker trips due to
high instantaneous current, the "
OVERRIDE/
" LED will light "RED",
and the display will read "
ORID
" .
1.1.5 Zone Interlocking
Zone Selective lnterlocking (or Zone Interlocking) is available (see
Figure 2) for Digitrip RMS Trip Units having Short Delay and/or
Ground Fault protection . Zone Selective lnterlocking provides the
fastest possible tripping for faults within the breaker's zone of pro-
tection, and yet also provides positive coordination among all break-
ers in the system (mains, ties, feeders and downstream breakers) to
limit the outage to the affected part of the system only . When Zone
lnterlocking is enabled, a fault within the breaker's zone of protection
will cause the Trip Unit to:
•
Trip the affected breaker instantaneously, and
•
Send a signal to upstream RMS Digitrip Trip Units to restrain from
tripping immediately . The restraining signal causes the upstream
breakers to follow their set coordination times, so that only the
minimum service is disrupted, while the fault is cleared in the
shortest time possible .
This signal requires that only a single pair of wires be connected
from the interlock output terminals of the downstream breaker's
Trip Unit, to the interlock input terminals of the upstream breaker's
Trip Unit . For specific instructions see the applicable connection dia-
grams for your breaker listed in Section 6 .
otee:
N
If a breaker (M) receives a Zone lnterlocking signal from another
breaker (F) that is tripping, but the fault current level is less than the setting
for breaker (M), the presence of the Zone lnterlocking signal from the other
breaker (F) can not cause breaker (M) to trip .
CAUTION
IF ZONE INTERLOCKING IS NOT TO BE USED (I.E.: STANDARD TIME-
DELAY COORDINATION ONLY IS INTENDED), THE ZONE INTERLOCKING
TERMINALS MUST BE CONNECTED WITH JUMPER WIRES, AS SPECIFIED
ON THE CONNECTION DIAGRAMS FOR YOUR BREAKER (SEE SECTION
6), SO THE TIME DELAY SETTINGS WILL PROVIDE THE INTENDED
COORDINATION.
For examples of how Zone Selective lnterlocking may be used, See
Appendix A .
1.2 Four Character Information Display Window
The four-digit alpha-numeric display window, illustrated in Figures 1
and 2, serves two basic purposes: instrumentation and mode of trip
and trouble indication . The information displayed in the window is
listed in Tables 2 and 3 .
1.2.1 Values Displayed During Normal Service
The alpha-numeric display window provides informational values
under normal service conditions and coded messages after an alarm
condition or after an over-current trip operation . The 12 Green LEDs
below the display window indicate which value of current, voltage,
power, power factor, energy, or Total Harmonic Distortion (THD) is
being displayed . The value in the display window indicates the pres-
ent value of the parameter whose LED is lighted "Green" . In Figure
1, the first four "Green" LEDs identify which current
(kA)
value is
being displayed, i .e .: phase A current
(I
A
)
, phase B current
(I
B
)
,
phase C current
(I
C
)
, ground current
(I
G
)
, or current in the fourth pole
(neutral)
(I
D
)
. The press and release operation of the "Step" push-
button will step next to the Green LEDs that identify the breaker's
phase to phase voltages being displayed; i .e .: (V
AB
), (V
BC
), (V
CA
) .
Values are in volts RMS .
A repeat press and release of "Step" pushbutton will proceed to the
four Green LEDs that identify Peak Power Demand (MW), Present
Power Demand (MW), Energy Demand (MWh), and Power Factor
(PF) . The next press and release of "Step" push-button will show the
(THD) for phase
(I
A
)
current . Notice that both the green LEDs (THD)
and
(I
A
)
are illuminated . Repeating "Step" push-button operation will
show (THD) values for
(I
B
)
and
(I
C
)
currents . Repeating press and
release one more time will sequence back from the (THD) of
(I
C
)
to
the
(kA)
current of
(I
A
)
. See Section 1 .2 .1 .4 for displaying per har-
monic data .
1.2.1.1 Instrumentation - Current Values
During the normal service conditions, with the circuit breaker closed,
the Digitrip 910 serves as an ammeter, displaying the individual
phase currents (I
A
, I
B
, I
C
) and ground current (I
G
) or the fourth pole
(neutral) current
(I
D
)
, provided the circuit breaker is set up for ground
or fourth pole protection . Current values are displayed in kA . The
value displayed is current in the pole (or ground) indicated by the
"Green" LED that is turned "On" . Press and release the (Black)
"STEP" push-button to view the values of current in the other phases
(see Figure 1) . The range, accuracy and wave shape parameters for
current values displayed are:
RANGE: 0 to 9 .999 kA if I
n
≤
1000 A
0 to 99 .99 kA if I
n
>1000A
ASSUMES: 5% < Current < 100% of Frame Rating for Series
C
®
R-Frame or Type SPB circuit breaker .
or
5% < Current < 100% of [Current] Sensor Rating
for Type DS circuit breaker .
ACCURACY: ± 2% of Frame Rating for Series C
®
R-Frame or
Type SPB circuit breakers .
or
± 2% of [Current] Sensor Rating for Type DS
circuit breaker .
