Instruction Leaflet
DT3000
Page 4
Effective: Date 07/02
I.B. 17555D
For more information visit:
www.cutler-hammer.eaton.com
Supersedes I.B. 17555C dated November 1999
1-3 FUNCTIONS/FEATURES/OPTIONS
The primary function of the Digitrip 3000 Protective Relay is
overcurrent protection. This is achieved by analyzing the
secondary current signals received from the switch gear
current transformers. When predetermined current levels
and time delay settings are exceeded, the closing of trip
contact(s) is used to initiate breaker tripping.
The Digitrip 3000 Protective Relay operates from the
secondary output of standard switch gear current
transformers rated at = 5 amperes. It is configured to fit
specific distribution system requirements. The phase and
ground Ct ratios can be independently programmed over a
range of 5:5 to 5000:5. Refer to Table 2.2 for the available Ct
ratio settings.
Protective functions can also be configured with the circuit
breaker in the open or closed position. The DIP Switch S2,
located on the rear of the relay, is used to control closed
breaker settings (Figure 1-3). Refer to Paragraph 2-2.2 and
Table 5.1 for additional information.
Inverse time overcurrent protection for the phase element
cannot be disabled. This insures that all phase protection
cannot be disabled. The relay also automatically exits the
program mode, if there is no programming activity for 2-1/2
minutes. Programming and test mode security is provided by
a sealed, hinged access cover on the front of the relay.
Direct reading displays indicate the value currently being
considered, while multi-colored LED’s indicate operational
conditions and specific functions.
In addition to performing a continuous self-testing of internal
circuitry, all Digitrip 3000 Protective Relays include field
testing capabilities that are accessible from the front. To
check that all tripping features are functioning properly a test
current simulates an overload or short circuit condition. Refer
to Paragraph 2-1.5 for additional information.
The Digitrip 3000 Protective Relay provides five protective
functions for both phase and ground protection:
•
Inverse Time Overcurrent Pickup
•
Inverse Time Overcurrent Time Multiplier
•
Short Delay Pickup
•
Short Delay Time
•
Instantaneous
Pickup
The ground element is capable of a residual, an external
source ground or a zero sequence connection. But if ground
protection is not desired, it does not have to be connected.
Each of the protective functions is independently
programmed for various combinations to fit specific system
requirements. For protective functions not required, the relay
will allow all of the protective functions on ground and all but
the inverse time overcurrent function on phase to be
disabled. When the Digitrip 3000 is not set for an
instantaneous trip function, a true making current release
(discriminator) is available. But if it’s not desired, the
discriminator can be disabled.
Fig. 1-2 Digitrip 3000 Protective Relay (Rear and Side Views)
