I.L. 29C508B
Page 6
Effective 9/00
The microcomputer, in cyclic fashion, repeatedly scans
the voltage values across each calibrating resistor and
enters these values into memory. These data are used
to calculate true RMS current values, which are then
repeatedly compared with the protection function set-
tings and other operating data stored in the memory.
The software program then determines whether to initi-
ate protection functions, including tripping the breaker
through the flux transfer shunt trip device in the circuit
breaker.
4.2 OVERLOAD TRIP
In accordance with standards requirements, the trip unit
initiates a trip of the circuit breaker within two hours for
an overload of 135 percent, and will trip in less time for
higher overload currents.
A "Thermal Memory" effect prevents the breaker from
being re-energized immediately after an overload. A
"cooling off" period of up to 5 minutes is required, which
allows time for cabling to cool off.
For details on the operation and protective functions of
the OPTIM 550 Trip unit and other related instructions,
contact Cutler-Hammer for the following information and
user’s manuals:
L-Frame and Accessories Selection Data
29-120L
Instructions and Overview of
OPTIM Trip Units
29C890
Instructions on the Operation of Digitrip
OPTIMIZER Hand Held Programmer
29C892
Instructions on the Operation of Digitrip
Breaker Interface Module
29C893
Instructions on the Operation of Digitrip
OPTIM Trip Units
29C891
Digitrip OPTIM Wire Diagrams
29C894
5.0 TESTING
5.1 FUNCTIONAL FIELD TESTING
Any field testing should be done in accordance with
applicable NEMA Standard. The operation of circuit
breakers with Digitrip OPTIM RMS trip units can be field
tested periodically using the hand held OPTIMIZER (see
user’s manuals).
5.2 PERFORMANCE TESTING FOR GROUND
FAULT TRIP UNITS
5.2.1 CODE REQUIREMENTS
The National Electrical Code under Article 230-95-C
requires that any ground-fault protection system be per-
formance tested when first installed. The test shall be
conducted in accordance with approved instructions
provided with the equipment. A written record of this test
shall be made and shall be available to the authority
having inspection jurisdiction.
5.2.2 STANDARDS REQUIREMENTS
As a follow-up to the basic performance requirements
stipulated by the N.E.C. as stated above, UL Standard
No. 1053 requires that certain minimum instructions
must accompany each ground fault protection system.
These following statements plus a copy of the test
record form illustrated in Figure 5-4 are shipped with
each Digitrip OPTIM 550 Trip Unit.
5.2.3 GENERAL TEST INSTRUCTIONS
The interconnected system shall be evaluated in accor-
dance with the equipment assembler's detailed instruc-
tions by qualified personnel.
The polarity of the neutral sensor connections (if used)
must agree with equipment assembler's detailed instruc-
tions to avoid improper operations following apparently
correct simulated test operations. Where a question
exists, consult the specifying engineer and/or equipment
assembler.
The grounding points of the system shall be verified to
determine that ground paths do not exist that would
bypass the sensors. The use of high-voltage testers and
resistance bridges may be used.
THERE IS A HAZARD OF ELECTRICAL SHOCK OR
BURN WHENEVER WORKING IN OR AROUND
ELECTRICAL EQUIPMENT. ALWAYS TURN OFF
POWER SUPPLYING BREAKER BEFORE CON-
DUCTING TESTS.
Since the Digitrip OPTIM 550 Trip Units derive their
operating power from the phase currents, and not
from the neutral current, passing current through
the neutral sensor only will not properly test the
ground fault feature.
Using a low voltage (0-24 volt), high current, AC source,
apply a test current of 125% of the Digitrip OPTIM 550
!
WARNING
NOTICE
