Instruction Leaflet DT3000
Page 24 Effective: Date 07/02 I.B. 17555D
For more information visit: www.cutler-hammer.eaton.com
Supersedes I.B. 17555C dated November 1999
Instantaneous Protection
Instantaneous (short circuit) protection reacts to high level
fault currents. The instantaneous pickup setting
establishes the current level at which the relay’s
instantaneous trip relay will be energized with no time
delay and is the instantaneous setting times (I
n
).
”If “NONE” is selected, the instantaneous trip function is
disabled and the discriminator option is offered. See the
Phase Instantaneous section to review the discriminator
option details.
If an Instantaneous Setting other than “NONE” is selected,
the instantaneous portion of the overall curve can be
moved independently in a horizontal direction. Figure 3-9
graphically illustrates this horizontal movement.
The instantaneous protection (INST) is designed to
typically provide no less than 2 cycle total response time.
To provide this fast response time the rms current
detection level and display readout may differ somewhat
from a true rms ampere value, if a significant percentage
harmonic current is present.
Ground Fault Protection
The ground fault protection function can be a composite of
the ground:
1. Inverse time overcurrent curve shape, pickup, and
time.
2. Short delay pickup and time.
3. Instantaneous pickup. Its curve shape is independent
of the phase curve.
There are two differences between Digitrip 3000 phase
and ground functions. The inverse time overcurrent time
multiplier values for the ground function of the thermal
curves are for (1 x I
n
). The inverse time overcurrent time
multiplier values for the phase is (3 x 2). The short delay
settings are more sensitive and can be set from (0.1 x I
n
)
to (11 x I
n
). Movement of the pickup portion of the curve in
a horizontal direction and the time portion of the curve in a
vertical direction is similar to phase inverse time over-
current, short delay and instantaneous functions previously
described. Therefore, ground fault curve movement is not
graphically illustrated. When programming ground fault
protection, keep in mind that if “NONE” is selected, the
ground fault protection is disabled. Even if the ground fault
protection is disabled, a detectable ground current will still
be displayed.
Fig. 3-3 Sample Electronic Trip Curves
To Next Page
Loading...
