DT3000
Instruction Leaflet
I.B. 17555D
Effective: Date 07/02
Page 29
For more information visit:
www.cutler-hammer.eaton.com
Supersedes I.B. 17555C dated November 1999
3-4.1 ADDRESS AND BAUD RATE SETTINGS
To enter the mode that permits changing the device
Address and/or BAUD Rate, depress and hold the Test
Pushbutton and then depress and release the “Select
Tests” Pushbutton. The BAUD Rate and Address
respectively will appear in the Settings/Test Time/Trip
Cause Window. The Test Pushbutton can now be
released. The last digit on the right is flashing. Press and
release the Select Settings Pushbutton to shift the flashing
portion of the display horizontally from the lowest address
digit on the right to the last display on the left, which is the
BAUD rate. The BAUD rate will flash with an “H” (High
BAUD Rate = 9600) or an “L” (Low BAUD Rate = 1200).
To increase or decrease the flashing digit or flashing baud
rate, press and release the Raise or Lower Pushbuttons.
When completed, depress the Save Set points Pushbutton
to save and exit this mode.
In the past sections we discussed several message the
DT3000 may display, below is a list of each message and
their meanings.
Message
Meaning
TEST
•
The system has entered test mode.
RAM
•
A ram check error was detected.
ERR
•
An error in the test mode has occurred.
•
An error in the EPROM set points was
detected.
PRGM
•
The system has entered program mode.
LDT
•
The Digitrip 3000 tripped via the inverse
time overcurrent function.
SDT
•
The Digitrip 3000 tripped via the short
delay function.
INST
•
The Digitrip 3000 tripped via the
instantaneous function.
DISC
•
The Digitrip 3000 tripped via the
discriminator function.
EXTT
•
An external trip occurred via INCOM
communications.
OVER
•
The Digitrip 3000 tripped via an override
(60 per unit fixed instantaneous).
ORNG
•
The Digitrip 3000 tripped via an overrange
value (trip value is greater than 28 per
unit).
SECTION 4: APPLICATION CONSIDERATIONS
4-1 ZONE INTERLOCKING CAPABILITIES
To minimize damage to the system, faults should be
cleared as quickly as possible. Zone selective interlocking
provides this capability better than a system with only
selective coordination.
When the “Ground Zone Interlocking” feature is utilized, an
immediate trip is initiated when the fault is in the breaker’s
zone of protection, regardless of its preset time delay.
When the “Phase Zone Interlocking” feature is utilized, the
inverse time overcurrent and short delay phase elements
work as follows. The short delay phase element will initiate
an immediate trip when the fault is in the breaker’s zone of
protection, regardless of its preset time delay.
For the
inverse time overcurrent phase element, the current
sensed by the Digitrip 3000 must exceed 300 percent
(3 x I
n
) for the zone selective interlocking to initiate an
immediate trip signal.
This interlocking signal requires
only a pair of wires from the downstream breaker to the
upstream breaker.
When a Digitrip 3000 initiates a trip signal, the zone
interlocking signal stays active for an additional 175
milliseconds. Therefore, if a downstream Digitrip 3000 is
zone interlocked to an upstream Digitrip 3000, the
downstream breaker will have 175 milliseconds to clear the
fault before the upstream Digitrip 3000 is allowed to react
to that same fault.
Zone interlocking, therefore, provides fast tripping in the
zone of protection, but gives positive coordination between
mains, feeders and downstream breakers. For faults
outside the zone of protection, the Digitrip 3000 on the
breaker nearest the fault sends an interlocking signal to
the Digitrip 3000 protective devices of the upstream
breakers. This interlocking signal restrains tripping of the
upstream breakers until their set coordination times are
reached. Thus zone interlocking, applied correctly, can
result in minimum damage with a resultant minimum
disruption of service.
Zone selective interlocking is available on Digitrip 3000
Protective Relays for the inverse time and short time
functions on the phase and ground elements. Refer to
Figure 4-1 for a typical ground zone selection interlocking
wiring diagram or refer to Figure 4-2 for a typical phase
zone selection interlocking wiring diagram.
