GE PACSystems RX3i User Manual page 52

3
Imbalance Threshold Examples
3-8
Parameter
ANSI 60 VI Imbalance Threshold
(%)
ANSI 60 VI Imbalance Delay
(sec)
ANSI 81U Under Frequency
Threshold
(Hz)
ANSI 81U Under Frequency
2
Delay (sec)
ANSI 81O Over Frequency
Threshold
(Hz)
ANSI 81O Over Frequency
2
Delay (sec)
Example 1:
VI Imbalance is set to 20%, VA1 = 126V, VB1 = 90V, VC1 = 124V
The difference between VB1 and the average of the three voltages is greater than 20%,
so the VI Imbalance alarm will be set.
Example 2:
VI Imbalance is set to 25%, IA2 = 4.2A, IB2 = 3.6A, IC2 = 5.5A
The difference between IC2 and the average of the three currents is less than 25%, so the
VI Imbalance alarm will not be set.
2
For all alarm conditions, the clear time is the same as the set time. The alarm condition must
be absent continuously for the Delay Time for the alarm to be cleared.
PACSystems* RX3i Power Sync and Measurement System – February 2013
The amount any one phase voltage or phase current
reading must vary, as a percentage of the average of all
three phases within the same grid, to trigger the VI
Imbalance alarm (after the VI Balance Delay).
The VI Imbalance alarm compares voltage phases to
voltage phases, and current phases to current phases
within a grid. No comparison is made between grids. If any
voltage varies from the average of all three voltages, or if
any current varies from the average of all three currents (by
more than the VI Imbalance Threshold) for longer than the
VI Imbalance Delay, that grid's VI Imbalance Alarm is set.
Range: 1 to 100
Default: 10
2
The amount of time any one phase voltage or phase current
reading can exceed the VI Balance Threshold before the VI
Balance Alarm status is set.
Range: 0.1 to 3276.7
Default: 10.0
The frequency difference from the Nominal Frequency
below which the Under Frequency Alarm status is set (after
the Under Frequency Delay).
0Range: 0.01 to 10.0
Default: 0.5
The amount of time a grid's frequency must remain below
the Under Frequency Threshold before the Under
Frequency Alarm status is set.
Range: 0.1 to 3276.7
Default: 10.
The frequency difference from the Nominal Frequency
above which the Over Frequency Alarm status is set (after
the Over Frequency Delay).
Range: 0.01 to 10.0
Default: 0.5
The amount of time a grid's frequency must remain Above
the Over Frequency Threshold before the Over Frequency
Alarm status is set.
Range: 0.1 to 3276.7
Default: 10
Function
GFK-2749