Ansi Functions Supported; Ansi Functions For Grid 1 (Public Grid/Load) Protection - GE PACSystems RX3i User Manual

ANSI Functions Supported

ANSI Functions for GRID 1 (Public Grid/Load) Protection

ANSI 27 – Under-voltage Protection
ANSI 32 – Reverse Power Protection
ANSI 47 – Voltage Phase Sequence Protection
ANSI 50 – Instantaneous Over-current Protection
GFK-2749
The Grid 1 and Grid 2 functions are similar, but with differences in implementation. Grid 1
is assumed to be the most stable power source, such a utility. Grid 2 is assumed to be a
less stable power source, such as a back-up generator. Either or both grids can be
connected for load monitoring, such as motors, lighting, HVAC or server room power.
Under-voltage Protection monitors voltages to protect motors against voltage sags. The
PSM monitors the phase-to-phase voltage in a delta power system, or phase-to-neutral
voltage in a wye power system, as a percentage of the Nominal Voltage parameter. An
alarm will be triggered if any voltage falls below the specified UNDER_VOLT_THR value
for a time period longer than UNDER_VOLT_DELAY. The alarm is cleared when the grid
voltage rises above the UNDER_VOLT_THR value for a time period longer than
UNDER_VOLT_DELAY. The UNDER_VOLT_THR is a percentage of the nominal voltage.
Reverse Power Protection provides protection from excessive reverse active power
produced by motors running as generators (supplying power). An alarm will be triggered if
a circuit's active power exceeds the REV_PWR_THR for a time period longer than
REV_PWR_DELAY. The Alarm will be cleared when the active power exceeds 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.
This function monitors the sequence of the phase A, B and C voltages. Detection of a
wrong sequence (A, C, B for example) triggers an alarm.
An entire cycle of waveforms is required to make this Phase Sequence determination.
There is no user settable delay parameter, so the moment a Phase Sequence error is
detected, the alarm is set. In both systems (Delta and WYE), the signal at the VA terminal
is expected to lead the signal at the VB terminal by 120 degrees. The signal at the VB
terminal is expected to lead the signal on the VC terminal by 120 degrees. Unused
"reconstructed" signal inputs are ignored for Phase Sequence detection. The current
signals are not monitored for Phase Sequence.
This function provides three-phase protection against overloads and phase-to-phase
short-circuits. An alarm will be triggered if any phase current exceeds the specified
OVER_CURR_ THR value for a time period longer than OVER_CURR_DELAY. This
alarm is cleared when the current value stays below the OVER_CURR_THR value for a
time period longer than OVER_CURR_DELAY. The OVER_CURR_THR is a percentage
of the nominal current.
Chapter 1 PSM Module Description and Specifications
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