I.B. 29C891B
Page 28
Effective 11/98
Notice:
Keep in mind during testing that a faster trip time
may be observed due to the cumulative Thermal
Memory Effect (powered or unpowered).
Both the powered and unpowered Thermal
Memory may be enabled or disabled via the
OPTIMizer, BIM or IMPACC computer.
High Load Alarm
A high load phase and neutral alarm is provided on all
OPTIM Trip Units to signal a high load condition. The
programmable range is as follows:
• 0.5 to 1.0 times (I
r
)
High Load Alarm indicators are provided as follows:
• IMPACC on all OPTIM units with communications
• L and N-Frame Breakers
- BIM Contacts
• R-Frame, SPB and DSII/DSLII Breakers
- BIM Contacts
- Automatic Trip Relay Contact
3-2.5 SHORT DELAY PROTECTION
Short delay protection is selectable with all Digitrip
OPTIM Trip Units. It can be selected in combination with
instantaneous protection or without instantaneous pro-
tection. Either both, one or the other (short or instanta-
neous) must always be provided (Tables
3.2
and
3.3
and Figure
3-4
). Short delay protection can consist of
the following:
• Short delay pickup setting
• Short delay time setting (I
2
t Slope)
• Short delay time setting (Flat Slope)
• Zone Selective Interlocking (Model 750 and 1050 only)
Short Delay Pickup Setting
The short delay pickup setting establishes the current
level at which the trip unit’s short time tripping function
begins timing. It is programmable as a multiple of the
long delay current setting (I
r
). The programmable range
depends on the circuit breaker type as follows:
• Series C K, L, N and R-Frames
- 1.5 to 8.0 times (I
r
) in 0.1 increments
• SPB Systems Pow-R
- 1.5 to 8.0 times (I
r
) in 0.1 increments
(400-3000 ampere frames)
- 1.5 to 6.0 times (I
r
) in 0.1 increments
(4000/5000
ampere frames)
TIME
CURRENT
Note: Long Delay Time
Setting represented
by dotted lines
Figure 3-8 Typical Long Delay Time Adjustment (I
4
t)
Response
TIME
CURRENT
Note: Short Delay Pickup
represented by
dotted lines
Figure 3-9 Typical Short Delay Pickup Adjustment
Summary of Contents for Digitrip OPTIM 1050
Page 7: ......
