VOLTAGE MElISUREMEft TIME
The time required for the
M-0290
to detect an over or undervoltage condition is dependent on the
voltage level before and after the voltage change and
the
setpcint of
the
over/undervoltage detector.
In case the J.X>tential input drops to zerO volts from its nominal
100%
value, the following time delays
for measurement can be eXJ;ected.
lJndervoltage Setting
5%
10%
20%
MeasurE!DeJ1t Time Delay
3
cycles
4
cycles
6
cycles
Longer measurement delays can be expected i f the input change is less. For example, if the input
voltage drops from
100%
to
75%
and the undervoltage setting is
80%,
a measurement delay of
20
cycles
can
be expected.
The measurement time delay for either under or overvoltage can be calculated from Figure
2.
This
figu£e
can
be used for either
an
increase or decrease in the input voltage if the voltage setp:>int is
between the initial voltage
and
the final voltage.
'!he
following two examples are shown to clarify this technique.
Refer to Figure
2
for definitions of
the terms..
Example
1 .
Exanple
2.
Initial Voltage
=
120
V
Final Voltage
=
140
V
Setpcint
=
130
V
vstep
=
20
V
Vset
=
10
V
Vset
(130 - 120)
10
--
=
X
100%
= - X
100%
=
50%
vstep
(140 - 120)
20
Time Delay (fran Figure
2)
=
0 .16
sec
( 9 .6
cycles)
Initial Voltage
=
120
V
Final Vol tage
=
100
V
Setpcint
=
108
V
Vset
(120 - 108)
12
-- =
X
100%
= - X
100%
=
60%
Vstep
(120 - 100)
20
Time Delay (fran Figure
2)
=
0 .19
sec
(ll.4
cycles)
FREQUENCY MEASUREMENT TIME
(2)
(3)
The time required for the
M-0290
to detect an over or under frequency eondi tion is dependent on the
frequency before and after an input frequency step change and the setpcint for the OVer/Under Frequency
detector. The frequency is measured each cycle of the potential input.
A
digital filter is used in
the microprocessor t o filter the data. This filter can add time delay dependent on how the input
changes relative to the setpcint.
Figure
3
shows how the filter output changes for a step change in
input frequency. If the setpoint is
62
Hz, the measured delay time is
1
cycle.
However, if the
setpcint is
64.5
Hz. the delay time is
4
cycles.
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6
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