Eaton Cutler-Hammer Digitrip RMS 510 - Section 3 the Digitrip RMS Trip; Current Sensors and Sensor Wiring; Auxiliary CT Module and Auxiliary CT; Harness

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