Applications
3.3 Voltage control
3KC ATC6300 transfer control device
Manual, 03/2018, L1V30535632002A-01
17
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In the case of three- or two-phase power supplies you can choose whether you want to
monitor the phase-to-phase voltage, the phase-to-neutral voltage, or both (P02.07). In
each case, the rated voltage set in P02.01 must be equal to the phase-to-phase voltage.
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The table below lists the measurements of the two lines. Some thresholds can also be
deactivated for triggering the transfer.
Measurement
Description
Can be deac-
tivated
Minimum voltage
One or more phases too low
No
Maximum voltage
One or more phases too high
Yes
Phase failure
Threshold value at which the device responds faster than when falling below
the minimum voltage
Yes
Voltage unbalance
Voltage phases are not symmetrical to one another
Yes
Minimum frequency
Frequency too low
Yes
Maximum frequency
Frequency too high
Yes
Phase sequence
Checking the rotational direction of the phases
Yes
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Each measurement can be assigned a specific delay time. Measured anomalies (beyond
the threshold values) must be present for longer than the set delay times, before it can be
concluded that there is a line fault.
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When all the line parameters are restored within the specified thresholds, the delay time
must elapse before the restored line may be reconnected. This delay period is
determined by two independent parameters:
–
P06.07 or P07.07 - delay time if the line is within the specified thresholds again (and
Line 2 or Line 1 is not available)
–
P06.08 or P07.08 - delay time if the line is within the specified thresholds again (and
Line 2 or Line 1 is available)
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For the minimum and maximum voltages, two thresholds are defined in each case. One
for the point beyond which the voltage is no longer considered sufficient (e.g. P06.01,
threshold MIN trip voltage); and another which is closer to the rated voltage, defining the
point beyond which it is sufficient again (e.g. P06.02, threshold MIN reset).
The distance between these two thresholds determines the hysteresis. It is possible to
stipulate, for example, that the voltage may no longer be used when it falls below 80% of
the rated voltage, and that in order to be usable again, it must rise above 85%. This
defines a hysteresis of 5% (dead zone). The same principle is applied to the maximum
voltage.
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If the voltage is within the set thresholds when the device is switched on or reset, both
sources are considered to be in order (without considering the delay times), except when
the load is already supplied by a circuit breaker; then the delay times are taken into
consideration.