GE Industrial Solutions WavePro - Manuel (Page 12)

Power+™ Trip Units
Chapter 2. Trip Unit Setup
6
Figure 4. Time-current curve illustrating long-time delay.
2–4 Short-Time Pickup
The optional short-time pickup function establishes the
current at which short-time trip is activated. Short-time
pickup is coupled with long-time pickup and the choices of
pickup settings are 1.5, 2, 2.5, 3, 4, 5, 7, and 9 times the
long-time setting. The time-current curves for short-time
pickup is illustrated in Figure 5.
Figure 5. Time-current curves illustrating short-time pickup.
2–5 Short-Time Delay
This function delays the breaker trip when the short-time
pickup function is activated. The switch settings
MIN , INT ,
and MAX correspond to nominal time delays of .10, .21,
and .35 second, respectively. The delay with I 2 T IN is for a
current of 600% of C at the lower limit of the band. The
delay with
I 2 T OUT is for the lower limit of each band.
The I 2 T OUT function, illustrated in Figure 6, establishes a
constant time delay. I 2 T IN biases the delay with a constant
slope, as shown in Figure 7.
Figure 6. Time current curve illustrating short-time delay with I 2 T OUT.
Figure 7. Time current curve illustrating short-time delay with I 2 T IN.
2–6 Instantaneous Pickup
Instantaneous overcurrent protection causes an immediate
breaker trip when the chosen current setting is reached.
The pickup current may be set to 1.5, 2, 3, 5, 7, and 9 times
the rating plug current, X, when the Trip Unit does not
have short-time installed, with 10 times X also available on
800–2000 A frame breakers. Additional settings of 10, 13,
and 15 times X are only available when short-time is
installed, depending on the breaker frame size.
Note the difference from short-time pickup, which is based
on a multiple of the long-time pickup setting, C, while
instantaneous pickup is based on the rating plug current,
X
. The time-current characteristic is illustrated in Figure 8.