Littelfuse Startco Protection Relays
Technical Note - Ground Check
GC-13 : SPLITTER-BOX DUAL-CABLE MONITORING WITH AN SE-135
An SE-135 Ground-Fault Ground-Check Monitor can protect the cables entering and leaving a dual-cable splitter box
(junction box), when one is terminated with an SE-TA24A and the other with an SE-TA24B Termination Assembly.
The SE-MUX was previously used to monitor two ground-check circuits by sampling each ground-check circuit
every half second. As a result, ground-check trip times were increased by up to a half second. The improved
method provides continuous monitoring of both ground-check circuits; therefore ground-check trip times are not
increased, and the complexity of splitter boxes is reduced. Littelfuse recommends replacing the SE-MUX in splitter-
box applications with an SE-TA24A and an SE-TA24B, as shown in Fig. 1.
LOAD 1
SE-CS10/40
ØA, B, C
SPLITTER BOX
GC
L
TRIP A
N
24
22
L1
1
25
UV
G
S E -TA 2 4 A
TE RMI NATION
AS SE M BLY
Use with
SE-135 and
SE-TA24B
24A
!
TRIP B
23
L2
2
CURRENT 16
SENSOR 17
GROUND
CHECK
5
6
LOAD 2
GC
CABLE
GROUND
7
8
G
S E-TA 2 4B
24B
TERM I NATI ON
A SSE M BLY
SE-135
!
Use with
SE-135 and
SE-TA24A
PORTABLE SUBSTATION
Figure 1: Simplified Connection Diagram
When an SE-TA24A and an SE-TA24B are used as a set, the parallel combination has the 12-V Zener characteristic
required by the SE-135 as a valid ground-check-loop termination. An open or short in the ground-check loop of
either cable will result in an SE-135 ground-check trip; no indication is provided of which cable is faulted.
To be able to energize either single cable independently, a live-end cover fitted with an SE-TA24A or an
SE-TA24B, as required, must be available at the splitter box.
WARNING:
Take proper care to prevent an SE-TA12A-series termination assembly from being used in a dual-termination
application with an SE-135. Because a single SE-TA12A will satisfy the SE-135, if an SE-TA12A terminates one (or
both) of the cables on a splitter-box application with an SE-135, the second cable will not be monitored. This can
result in a hazardous condition on the unmonitored cable, where an energized open cable/coupler, an open ground
connection, or a shorted ground-check loop would not be detected. See Fig. 2 for a sample warning label that could
be applied to each cable coupler or beside each SE-TA24A and SE-TA24B installation location.
© 2014 Littelfuse Startco
www.littelfuse.com/relayscontrols
1
Pub. TN-GC12, Revised December 17, 2014
Littelfuse
Littelfuse Startco Protection Relays Startco Protection Relays
Technical Note - Ground Check
GC-13 : SPLITTER-BOX DUAL-CABLE MONITORING WITH AN SE-135
To avoid confusion on dual-cable and splitter-box applications, the SE-TA24A has a green label with 24A shown in
large white print, and the SE-TA24B has a white label with 24B shown in large green print. See Fig. 3.
For new applications, or those where UL, CSA, or CE labeling is required on the termination assemblies, consider
the SE-134C Ground-Fault Ground-Check Monitor and SE-TA12A and SE-TA12B Termination Assemblies. This
technology also has one advantage in an application where the SE-MUX and SE-TA12A Termination Assemblies
were previously used: a single SE-TA12A does not satisfy the SE-134C. See Technical Note GC-09: Splitter-Box
Dual-Cable Monitoring (http://www.littelfuse.com/splitterbox-gc).
WARNING
THIS EQUIPMENT IS PART OF A SPLITTER-BOX/DUAL-CABLE
APPLICATION.
USE ONLY SE-TA24A (GREEN LABEL) OR SE-TA24B (WHITE
LABEL) TERMINATION ASSEMBLIES.
USE OF ANY OTHER TERMINATION ASSEMBLY COULD RESULT
IN HAZARDOUS CONDITION.
Figure 2: Sample Warning Label
Figure 3: SE-TA24A and SE-TA24B Termination Assemblies
© 2014 Littelfuse Startco
www.littelfuse.com/relayscontrols
2
Pub. TN-GC12, Revised December 17, 2014
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