Section 3 The Digitrip Rms Trip; Current Sensors And Sensor Wiring; Auxiliary Ct Module And Auxiliary Ct; Harness - Eaton Cutler-Hammer Digitrip RMS 510 Instructions Manual

AD
33-855-4
Page
11
SECTION
3
THE DIGITRIP RMS TRIP
SYSTEM
3.1
Digitrip BMS Overcurrent
Protection
The Digitrip RMS Retrofit Kits covered by this
Application Guide are designed
to replace the
existing Trip System employed on the Breaker
selected
for
Retrofitting.
All Digitrip RMS Retrofit Kits provide basic
Overcurrent Protection, which includes a selected
combination of Long Time
(L),
Short Time (S),
lnstantaneous (l),
and Ground Fault Time (G) Delay
Trip Functions. Five major components comprise
the Digitrip RMS Ti'ip System:
the Current Sensors;
Auxiliary CT Module; Digitrip Trip Unit; Rating Plug;
and the Direct Trip Actuator (DTA).
These compo-
nents are interconnected by use of the various
wiring harnesses to make up the Digitrip
RMS Trip
System. Breaker interface diagrams for Digitrip
RMS 510 through 910 are provided in Sections 4
through 7. These diagrams
show the major Digitrip
RMS components and their interconnections.
Wiring diagrams for each of the wiring harnesses
are
shown in Section
12.
Figure
3-1 shows the major components of the
Digitrip Retrofit System and their interconnections.
The following sections describe the function and
operation of each component.
3.2
Current Sensors and Sensor Wiring
Harness
Three single or multi-tapped Current Sensors (one
per phase) are located at the rear of
the
Breaker.
The Sensors pass information to the Auxiliary CT
Module and the Trip Unit about the primary current
level passing through the Breaker. All the energy
required
to power the Digitrip RMS Trip System
is
produced by the Current Sensors.
The Current Sensors are connected
to
a terminal
block strip on the Auxiliary CT Module by the
Sensor Wiring Harness. The Current Sensor Tap
ratio connected, in concert with the Rating Plug,
determines the Continuous Current Rating (ln) of
the
Breaker.
At rated primary current, the Current
Sensors provide 5 ampere nominal current inputs
to the Auxiliary CT Module.
3.3
Auxiliary
GT
Module and Auxiliary CT
Harness
The Auxiliary CT Module encloses three auxiliary
phase Current Transformers, which reduce the
5
ampere nominal inputs from the Current Sensors
to the milliampere level required for the Digitrip
RMS Trip Unit
electronics. When Ground Fault
(G)
protection
is
selected, a Ground Auxiliary Current
Transformer is also provided, which performs the
same function.
A 7-point terminal block strip is mounted to the
Auxiliary CT Module. Terminals A through G termi-
nate the inputs from the Current Sensors via the
Sensor Wiring Harness. Terminals OP and ON
connect the Trip Signal
Outputs to the Direct
Trip
Actuator (DTA)
via the Sensor Wiring Harness or
DTA
Wiring Harness. A 12-point female CT Plug-in
Block is mounted
on
the right hand side of the
module, which receives the male plug of the
Auxiliary CT Harness. The Auxiliary CT Harness
also has a 10-pin black plug, which plugs into the
Trip Unit
to connect the
Auxiliary CT lnputs to
the'
Trip Unit and receives the Trip Unit trip signal
outputs.
Refer
to
Figure 12-6 for Auxiliary CT
Module wiring.
3.4
Digitrip RMS Trip
Unit and Power
Relay Module
(ATR)
The 1O-Series Digitrip RMS Trip Units (510
through 910 Kits), Figure
3-1 ,
are designed
to
permit flexibility in Retrofit applications. They are
physically repackaged versions of the original
1
OO-Series
Digitrip RMS Trip Units that were used
on Cutler-Hammer
DS and
SPB Breakers. The
RMS Trip
Units
have
the same features and
options and have identical characteristic curves,
adjustments, and electrical pedormance.
The Digitrip RMS Trip Unit is a microprocessor
based protective device that provides true
RMS
sensing means for proper correlation with thermal
characteristics on conductors and equipment.
Digitrip
RMS Trip Units are available in
four mod-
els, RMS 510,
61
0,
81
0, &
91
0. These models are
available in horizontal or vertical labeling and
display orientations.
Eflective 9/01
ElT.il