Alstom iSTAT M355, Manual, Page: 48 / 154

M3x5/EN M/B User Manual
Page 46
iSTAT M3x5
10.5.3 Used Voltage and Current Range
The setting of this range is connected with the setting of all alarms, analogue outputs and the
display (calculation) of energy and measurement recording. Using a value that matches the
expected measurement range (with overload) will achieve the highest quality of
measurements.
If the ‘Used’ ranges are changed after the analogue or alarm settings have been defined,
then the analogue and alarm settings will be modified automatically, as defined below. It
may be necessary to modify the settings for the analogue and alarm outputs.
The ‘Used’ ranges are used to set the default scaling for the analogue output, which can be
subsequently changed to meet the application requirements. Internally the analogue
settings are also stored as a percentage of the ‘Used’ ranges. If the ‘Used’ ranges are
subsequently changed the analogue output settings will be correspondingly changed to
maintain the settings as the same percentage of the ‘Used’ range.
Although the alarm settings are defined in real values on QDSP2 , the alarms are also
calculated as a percentage of the ‘Used’ range. If the ‘Used’ ranges are subsequently
changed the alarm settings will be correspondingly changed to maintain the settings as the
same percentage of the ‘Used’ range.
10.5.4 Nominal Frequency
The Nominal frequency can be selected from a list of predefined values. A valid frequency
measurement is within ± 30Hz of the nominal frequency.
This setting is only used for alarms and recorders.
10.5.5 Maximum Demand current for TDD
Select maximum current (CT or fuse rating) at a point of instrument connection for proper
TDD calculation. Unlike THD, TDD is a measure of harmonics relative to a fixed value of
max demand current. Therefore TDD is a demand independent measure of current
harmonics.
10.5.6 Wrong connection warning
If all phase currents (active powers) do not have the same sign (some are positive and some
negative) and/or if phase voltages and phase currents have mixed signs, the warning will be
activated if this setting is set to YES. An icon will appear on the display.
10.5.7 Energy flow direction
This setting allows a manual change of energy flow direction (IMPORT to EXPORT or vice
versa) in readings tab.
It has no influence on readings sent to communications or to memory!
10.5.8 CT connection
If this setting is set to REVERSED it has the same influence as if the CT’s were connected in
reverse. All power readings will change their sign.
This setting is useful to correct wrongly wired CT connections.