I.B. 17555
Page 22
Effective 03/97
the protective relay's trip relay is energized. As is the
case with inverse time overcurrent protection, short
delay protection also offers a range of settings for both
pickup and time. Refer to Tables 2.2 and 2.3 for avail-
able selections.
Two points should be made concerning the available
selections: 1) In Table 2.2 covering Short Delay Pickup
settings, “NONE” is one of the available selections. If
“NONE” is selected, the Short Delay function is disabled
and there will be no Short Delay protection. Also, if
“NONE” is selected, a Short Delay Time selection is not
offered. 2) There is no curve shape selection for the
Short Delay Time portion of the curve. A flat response
curve is automatic.
When a short delay pickup setting other than “NONE” is
selected, the Short Delay pickup and the Short Delay
Time portions of the overall curve are moved horizontal-
ly and vertically in a similar manner to the inverse time
protection functions. Refer to Figures 3-6 and 3-7 for
graphic illustrations of this movement.
Note that the scope of protection offered by Digitrip
3000 is a coordinated effort. This is especially true when
TIME
CURRENT
Time Multiplier is
represented by the
dotted portion of
the curve.
Figure 3-5 Typical Time Multiplier Adjustment (I
2
T
Response)
TIME
CURRENT
Short Time Pickup
is represented by
the dotted portion
of the curve.
Figure 3-6 Short Delay Setting Adjustment
TIME
CURRENT
Short Delay Time
is represented by
the dotted portion
of the curve.
Figure 3-7 Short Delay Time Adjustment