GE PACSystems RX3i User Manual page 16

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ANSI 59 – Over-voltage Protection
ANSI 60 – Voltage (Current) Imbalance Protection
ANSI 81U – Under-frequency Protection
ANSI 81O – Over-frequency Protection
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This function provides detection of abnormally high phase voltage. It works with
phase-to-phase voltage in delta power systems, or phase-to-neutral voltage in wye power
systems. Each voltage is monitored separately. An alarm will be triggered if any voltage
exceeds the specified OVER_VOLT_THR value, as a percentage of the Nominal Voltage
parameter, for a time period longer than OVER_VOLT_DELAY. This alarm is cleared
when the voltage drops below the OVER_VOLT_THR value for a time period longer than
the OVER_VOLT_DELAY. The OVER_VOLT_THR is a percentage of the nominal
voltage.
An alarm will be triggered if any phase voltage or current reading varies from the average
of all three phases by more than VI_IMBALANCE_THR for a time period longer than
VI_IMBALANCE_DELAY. The alarm is cleared when the imbalance condition is corrected
for a time period longer than VI_IMBALANCE_DELAY. IV_IMBALANCE_THR is a
percentage of the average of the three phase voltages (for voltage imbalance) or the three
phase currents (for current imbalance) on a given grid. It works with phase-to-phase
voltage in Delta power systems, or phase-to-neutral voltage in WYE Power systems. No
comparison is performed between the two grids. Neutral current is not monitored for
imbalance.
Detection of abnormally low frequency compared to the nominal frequency, to monitor
power supply quality. An alarm will be triggered if a circuit's frequency falls below the
nominal frequency minus the UNDER_FRQ_THR for a time period longer than
UNDER_FRQ_DELAY. The alarm is cleared when the frequency rises above the nominal
frequency minus UNDER_FRQ_THR for a time period longer than UNDER_FRQ_DELAY.
UNDER_FREQ_THR is an absolute frequency, in Hz, that is subtracted from the nominal
frequency to determine the lowest acceptable frequency for the grid.
Detection of abnormally high frequency compared to the nominal frequency, to monitor
power supply quality. The alarm will be triggered if a circuit's frequency is above the
nominal frequency plus OVER_FRQ_THR for a time period longer than
OVER_FRQ_DELAY. The alarm will be cleared when a circuit's frequency falls below the
nominal frequency plus OVER_FRQ_THR for a time period longer than
OVER_FRQ_DELAY. OVER_FREQ_THR is an absolute frequency, in Hz, that is added
to the nominal frequency to determine the highest acceptable frequency for the grid.
PACSystems* RX3i Power Sync and Measurement System – February 2013
GFK-2749