19
Instruction Leaflet
I. L. 29-889B
Effective June 2011
Instructions for Digitrip RMS 910 Trip Unit
eaton corporation
www.eaton.com
3.7 No Instantaneous Current Setting
For types LS and LSG Trip Units, please see Sections 1 .1 .3
DlScriminator (High initial Current Release) and 1 .1 .4 OVERRIDE
(Fixed Instantaneous), for available fast-acting high short-circuit pro-
tection .
3.8 Ground Fault Current Setting
The eight (8) Ground Fault "Pick-up" Current Settings are labeled
with the code letters "A" through "K" (except there are no "G" or "I"
settings), as illustrated in Figure 18 . In general, the specific current
settings range from 0 .25 to 1 .0 times (I
n
), the rating plug value, but
cannot exceed 1200 A . The specific Ground Current Settings for
each letter are listed in Table 4 and on the (G) Time-Current Curve
applicable for the circuit breaker (see Section 6) .
otee:
N
For Testing Purposes Only: When using an external single phase current
source to test low level ground fault current settings, it is advisable to use the
Auxiliary Power Module (APM) (see Section 1 .6 and Figure 12) .
3.9 Ground Fault Time Delay Setting
As illustrated in Figure 19, there are two different Ground Fault
curve shapes, i .e ., fixed time (flat) and I
2
t response . The shape
selected depends on the type of selective coordination chosen . The
I
2
t response will provide a longer time delay in the low-end of the
ground fault current range than will the flat response .
Five flat ( .I, .2, .3, .4, .5 sec .) and three I
2
t ( .I*, .3*, .5* sec .)
response time delay settings are available . The I
2
t response settings
are identified by the suffix asterisk (*) that appears in the setting
viewing window . The I
2
t response is applicable to currents less than
0 .625 x I
n
, (the I
n
value is marked on the installed rating plug) . For
currents greater than 0 .625 x I
n
, the I
2
t response reverts to the flat
response .
otee:
N
See also Section 1 .1 .5 on Zone Interlocking .
otee:
N
In addition to the standard Ground Fault protection, the Digitrip RMS
910 Trip Unit also has a GROUND TIME MEMORY (GTM) function, which
serves to protect loads in the event of a sputtering arc to ground . Without
the GTM function, the Trip Unit would normally reset each time the arc sput-
tered, and begin to time-out all over again, so that a sputtering fault may not
have been detected . But with the GTM function, the Trip Unit "remembers"
the sputtering ground current for up to five (5) times the Ground Fault Time
Setting . After that time, it does reset automatically . The GTM function does
reset rather quickly; on the 0 .1 second setting, for example, it will reset in
0 .5 second .
4 test procedures
4.1 General
DANGER
DO NOT ATTEMPT TO INSTALL, TEST OR PERFORM MAINTENANCE ON
EQUIPMENT WHILE IT IS ENERGIZED. DEATH OR SEVERE PERSONAL
INJURY CAN RESULT FROM CONTACT WITH ENERGIZED EQUIPMENT.
DE-ENERGIZE THE CIRCUIT AND DISCONNECT THE CIRCUIT BREAKER
BEFORE PERFORMING MAINTENANCE OR TESTS.
DO NOT ATTEMPT TO PERFORM DIELECTRIC (OR HIGH POT OR HIGH
VOLTAGE) WITHSTAND TESTS ON THE CIRCUIT BREAKER WHILE THE
VOLTAGE DISCONNECT PLUG TO THE POTENTIAL TRANSFORMER MODULE
IS INSTALLED. (SEE FIGURE 11 AND INSTRUCTIONS FOR TESTING YOUR
SPECIFIC CIRCUIT BREAKER LISTED IN SECTION 6). PTM OR TRIP UNIT
DAMAGE OR FAILURE CAN RESULT FROM ENERGIZING PTM AT MORE
THAN 600 VOLTS.
VERIFY THAT NO VOLTAGE IS PRESENT ON THE CIRCUIT BREAKER BEFORE
REMOVING THE VOLTAGE DISCONNECT PLUG (SEE FIGURE 11).
REMOVE THE VOLTAGE DISCONNECT PLUG TO ISOLATE THE POTENTIAL
TRANSFORMER MODULE (FIGURE 11) BEFORE PERFORMING ANY VOLTAGE
TESTS ON THE CIRCUIT BREAKER. REINSTALL THE PLUG ONLY AFTER
ALL VOLTAGE TESTS HAVE BEEN COMPLETED AND CONFIRM THAT NO
VOLTAGE IS PRESENT ON THE CIRCUIT BREAKER.
REINSTALL THE VOLTAGE DISCONNECT PLUG TO RECONNECT THE
POTENTIAL TRANSFORMER MODULE BEFORE PLACING THE BREAKER
BACK INTO SERVICE. REFER TO THE APPLICABLE CIRCUIT BREAKER
INSTRUCTION LEAFLET SUPPLEMENT (LISTED IN SECTION 6) FOR
COMPLETE INSTRUCTIONS.
CAUTION
TESTING A CIRCUIT BREAKER UNDER "TRIP CONDITIONS" WHILE IT IS IN
SERVICE AND CARRYING LOAD CURRENT, WHETHER DONE BY LOCALLY OR
BY REMOTE MEANS, IS NOT RECOMMENDED.
ANY TRIPPING OPERATION WILL CAUSE DISRUPTION OF SERVICE
AND POSSIBLE PERSONAL INJURY RESULTING FROM UNNECESSARY
SWITCHING OF CONNECTED EQUIPMENT.
TESTING OF A CIRCUIT BREAKER THAT RESULTS IN THE TRIPPING OF THE
CIRCUIT BREAKER SHOULD BE DONE ONLY WITH THE CIRCUIT BREAKER
IN THE "TEST" OR "DISCONNECTED" CELL POSITIONS OR WHILE THE
CIRCUIT BREAKER IS ON A TEST BENCH.
4.2 When To Test
Tests can be conducted with the breaker in the "connected" cell posi-
tion while carrying load current . However, as stated in the caution
note in Section 4 .1, good practice will limit circuit breaker in-service
"trip tests", where required, to maintenance periods during times of
minimum load conditions . Testing is accomplished with the breaker
out of its cell or in the "Test", "Disconnected", or "Withdrawn" (or
Removed) cell positions .
otee:
N
Since time-current settings are based on desired system coordination
and protection schemes, the protection settings selected and preset in accor-
dance with Section 3 should not be altered during or as a part of any routine
test sequence .
