GE Industrial Solutions EntelliGuard TU Trip Units - Manual (Page 17)

DEH-4567B EntelliGuard TU Trip Units: UL/ANSI Models
Protection
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SECTION 2. PROTECTION
OVERCURRENT PROTECTION FUNCTIONS
The Trip Unit provides the following over current
protections:
• Long Time (L)
• Short Time (S)
• Instantaneous (I, H=high range)
• Reduced Energy Let Through Instantaneous (RELT)
• Ground Fault Internal Summation (G)
• Ground Fault CT External Summation (C, EntelliGuard G
only)
• Instantaneous Override (HSIOC)
• Making Current Release (MCR)
LONG TIME PROTECTION
Long Time Pickup
This setpoint establishes the breaker's nominal ampere
rating, xLT, as a fraction of the rating plug value, xIn:
xLT = LT multiplier x xIn
The adjustment range for long time pickup settings is 0.50
to 1.00 times xIn in steps of 0.05. The pickup value has a
10% tolerance. The band is drawn at 1/(1+10%) and 1/1-
10%). The actual long time pickup is increased by 12% over
the nominal so that 100% nominal current may be carried
indefinitely. So a 1000 A setting is placed at 1120 A with the
minimum pickup drawn (left side of band) is 1088A, and the
maximum pickup (right side of band) is drawn at 1244A.
Figure 2-1 shows the Long Time pickup setting.
Figure 2-1: Long Time Pickup Settings
Long Time Delay
The trip unit provides up to 44 long time delay bands (only
on trip unit models starting with “J”). Not all circuit breakers
have all bands available. There are 22 bands using a
logarithmic type curve resembling the overcurrent
response of a thermal magnetic circuit breaker. And
available i
4 t option adds 22 bands that simulate the
overcurrent response of fuses. The EntelliGuard circuit
breaker is able to use all 44 bands. Power Break I, Power
Break II, WavePro and AKR circuit breakers use the 19
lower thermal CB-type bands and the 22 fuse-type bands.
Figure 2-2: Long Time Delay Settings
Thermal Long Time Overcurrent
The thermal I 2 T shape is similar to the typical curve of a
thermal magnetic circuit breaker and matches the shape
of many overcurrent devices used in industry today. The
typical shape and range of settings may be seen in Figure
2-2. The range of time delays is shown in Table 2-1 at
various multiples of nominal (100%) current setting. Drawn
bands also include a mechanical constant time to account
for circuit breaker operating and clearing time, which
causes the slight widening of the band evident at the lower
(right) end of the faster (lower) bands.