MicroVersaTrip Plus™ and MicroVersaTrip PM™ Trip Units
Chapter 2. Setup Mode
19
Figure 22. Time-current curve for ground-fault pickup.
Ground-Fault Delay
This function sets the delay before the breaker trips
when the ground-fault pickup current has been
detected. The Trip Unit display is shown in Figure
23. The choices are listed in Table 15. The delay for
I2T OUT
is at the lower limit of each band. The delay
for
I2T IN
is at 200% of the pickup setting at the lower
limit of the band.
The
I2T OUT
function establishes a constant time
delay, as shown in Figure 24.
I2T IN
biases the delay
with a constant slope, as shown in Figure 25.
With the X or GD options (switchable ground fault),
an
OFF
selection appears as an additional time-delay
set point. Selecting
OFF
disables ground-fault protec-
tion.
Figure 23. Trip Unit display for ground-fault delay, showing
I2T
out.
B
B
B
Baa
a
an
n
n
nd
d
d
d
T
T
T
Tiiiim
m
m
meee
e D
D
D
Deee
ellllaa
a
ayyyy,,,, sssseee
eccc
c
OFF
Disabled
1
0.10
2
0.21
3
0.35
Table 15. Lower-limit delays for ground-fault delay bands.
Figure 24. Time-current curve for ground-fault delay with
I2T
OUT
.
Figure 25. Time-current curve for ground-fault delay with
I2T IN
.
Voltage-Unbalance Relay Pickup
This function compares the highest or lowest phase
voltage with the average of all three phases and
initiates a trip if the difference exceeds the set point.
The true rms voltage is computed for each phase.
The range of set points is from 10 to 50% of the
unbalance, with an increment of 1%. The Trip Unit
display is shown in Figure 26.
