User Manual Chapter 1
GFK-2749A Jan 2020
PSM Module Description and Specifications 16
mover power rises above the REV_PWR_THR for a time period longer than REV_PWR_
DELAY. The REV_PWR_THR is a percentage of the nominal power which, in a 3-phase
system, is three times the nominal voltage multiplied by the nominal current.
ANSI 47 – Voltage Phase Sequence Protection
The sequence of the phase A, B and C voltages is monitored. Detection of a wrong sequence
(A, C, B for example) will trigger an alarm.
ANSI 50 – Instantaneous Over-current Protection
Provides three-phase protection against overloads and phase-to-phase short-circuits. The
alarm will be triggered if any phase current exceeds the specified OVER_CURR_ THR voltage
value for a time period longer than OVER_CURR_DELAY. The OVER_CURR_THR is a
percentage of the nominal current.
ANSI 59 – Over-voltage Protection
This 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.
ANSI 60 – Voltage (current) Imbalance
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.
ANSI 81U – Under-frequency Protection
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.
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