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Effective 11/2003
Page 6
I.L. 66A7535H02
If you have any questions or need further information or
instructions, please contact your local representative or
the Cutler Hammer Customer Support Center.
1.0 GENERAL DESCRIPTION OF DIGITRIP TRIP UNITS
The Digitrip Trip Units are breaker subsystems that provide
the protective functions of a circuit breaker. The trip unit is
in a removable sealed housing, installed in the breaker,
and can be replaced in the field by the end user.
This instruction book specifically covers the application of
Digitrip Trip Units, as illustrated in Figure 1.1, installed in
Type VCP-T, VCP-TR, T-VAC or T-VACR Medium Voltage
Circuit Breakers.
The Digitrip 1150V version conforms to UL/CSA require-
ments and model 1150V
i
adheres to IEC requirements.
NOTE:
Throughout this Instructional Leaflet, the use of the
term “Digitrip 1150V” refers to both the Digitrip 1150V and
1150V
i
unless unless otherwise noted.
The Digitrip 1150V trip units may be applied to either 50 or
60 Hz systems.
Digitrip 1150V trip units incorporate two microprocessors in
their design. One processor is devoted totally to the task
of current protection functions. This processor provides
true RMS current sensing for the proper coordination with
the thermal characteristics of conductors and equipment.
The Digitrip analyzes the secondary current signals from
the user’s wired in current sensors and, when preset
current levels and time delay settings are exceeded, sends
an initiating trip signal to the Trip Actuator of the circuit
breaker. The current sensors provide operating power to
the trip unit. As current begins to flow through the breaker,
the sensors generate a secondary current which powers
the trip unit.
The second microprocessor provides the voltage protec-
tion, display, communications, metering, harmonic calcula-
tions, alarming and auxiliary relay functions. These
additional features require that auxiliary power be provided
to the circuit breaker.
1.1 Protection
The Digitrip 1150V Trip Unit is completely self-contained
and requires no external control power to operate its basic
over current protection functions. It operates from current
signal levels derived from the current sensors.
The Digitrip 1150V provides five phase and two ground
(time-current) curve-shaping adjustments. To satisfy the
protection needs of any specific installation, the exact
selection of the available protection function is adjustable.
The short delay and ground fault adjustments include
either a FLAT or I2T response. A pictorial representation of
the applicable time-current curves for the selected protec-
tion functions is provided, for user reference, on the face of
the trip unit as shown in Figure 1.1.
1.2 Mode of Trip and Status Information
A green light emitting diode (LED), labeled Status, blinks
approximately once each second to indicate that the trip
unit is operating normally. This Status LED will blink at a
faster rate if the Digitrip is in a pick-up, or overload, mode.
Red LEDs on the 1150V’s face flash to indicate the cause,
or trip mode, for an automatic trip operation (for example,
ground fault, overload, or short circuit trip). A battery in the
Digitrip unit maintains the trip indication until the Reset
button is pushed. The battery is satisfactory if its LED
lights green when the Battery Test button is pushed
(See
Section 6).
NOTE:
The Digitrip 1150V provides all protection functions
regardless of the status of the battery. The battery is only
needed to maintain the automatic trip indication on the
mimic curve of the Digitrip when auxiliary power is not
available.
1.3 Installation and Removal
1.3.1 Installation of the Trip Unit
Align the Digitrip unit with the molded guide ears on the
platform and spring clips of the circuit breaker. Before
plugging into the black edge connector, align the long pins
on the bottom of the Digitrip into the white, I1, connector
(See Figure 1.2).
Press the unit into breaker until the PC
board edge engages into the connector and the spring
clips engage over the Digitrip’s housing. NOTE: Recheck
visually the connector I1 to insure all plugs are engaged
properly.