4–42 PQM POWER QUALITY METER – INSTRUCTION MANUAL
S4 ALARMS/CONTROL CHAPTER 4: PROGRAMMING
• UNDERVOLTAGE LEVEL: When the voltage on one, two, or three phases drops to or
below this level, an undervoltage condition occurs. The number of phases required is
determined by the
PHASES REQUIRED FOR U/V OPERATION setpoint. To clear the
undervoltage condition, the level must increase to 103% of the
UNDERVOLTAGE
LEVEL
setting. For example, if the UNDERVOLTAGE LEVEL is set to 4000 V, the
condition clears when the voltage in the appropriate phase(s) increases above 4120 V
(4000 × 1.03). This hysteresis is implemented to avoid nuisance alarms due to voltage
fluctuations.
• UNDERVOLTAGE DELAY: If the voltage drops to or below the
UNDERVOLTAGE LEVEL
setpoint value and remains this way for the time delay programmed in this setpoint,
an undervoltage condition will occur.
• PHASES REQ’D FOR U/V OPERATION: Select the minimum number of phases on which
the undervoltage condition must be detected before the selected output relay will
operate. This setpoint is not visible if
VT WIRING is set to SINGLE PHASE DIRECT.
• DETECT UNDERVOLTAGE BELOW 20V: If an indication is required for loss of voltage,
select
YES for this setpoint. If NO is selected and any one of the voltage inputs has less
than 20 V applied, the undervoltage feature will be disabled.
• OVERVOLTAGE RELAY: Overvoltage can either be disabled, used as an alarm or as a
process control. Set this setpoint to off if the feature is not required. Selecting alarm
relay will cause the alarm relay to activate and display an alarm message whenever
an overvoltage condition exists. Selecting auxiliary relay will cause the auxiliary relay
to activate for an overvoltage condition but no message will be displayed. This is
intended for process control.
• OVERVOLTAGE LEVEL: When the voltage on one, two, or three phases equals or
exceeds the level determined with this setpoint, an overvoltage condition occurs. The
number of phases required is determined by the
PHASES REQUIRED FOR O/V
OPERATION
setpoint. To clear the overvoltage condition, the level must decrease to
97% of the
OVERVOLTAGE LEVEL setting. For example, if the OVERVOLTAGE LEVEL
is set to 4200 V, the condition clears when the voltage in the appropriate phase(s) goes
below 4074 V (4200 × 0.97). This hysteresis is implemented to avoid nuisance alarms
due to voltage fluctuations.
• OVERVOLTAGE DELAY: If the voltage equals or exceeds the
OVERVOLTAGE LEVEL
setpoint value and remains this way for the time delay programmed in this setpoint,
an overvoltage condition will occur.
• PHASES REQ’D FOR O/V OPERATION: Select the minimum number of phases on which
the overvoltage condition must be detected before the selected output relay will
operate. This setpoint is not visible if
VT WIRING is set to SINGLE PHASE DIRECT.
• CURRENT UNBALANCE RELAY: Current unbalance is calculated as the maximum
deviation from the average divided by the average three phase current. Current
unbalance can either be disabled, used as an alarm or as a process control. Set this
setpoint to off if the feature is not required. Selecting alarm relay will cause the alarm
relay to activate and display an alarm message whenever a current unbalance
condition exists. Selecting auxiliary relay will cause the auxiliary relay to activate for a
current unbalance condition but no message will be displayed. This is intended for
process control.
Courtesy of NationalSwitchgear.com
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