Ansi Functions For Grid 2 (Generator/Generator Grid) Protection - GE PACSystems RX3i User Manual

ANSI Functions for GRID 2 (Generator/Generator Grid) Protection

ANSI 25 – Generator & Public Grid Synchronization
GFK-2749
It is the responsibility of the user to verify that the system has
sufficient frequency stability to maintain the current phase trend
during the synchronization process. This requirement is especially
true for long breaker delays. Failure to maintain frequency stability
during synchronization may result in personal injury, equipment
damage, or both.
The PSM module can synchronize two sources from either a static phase angle or a
rotating phase angle.
In static phase angle synchronization, the overall PLC control system holds the two grids
at the same amplitudes, frequencies and phase angles, and then requests that the PSM
module synchronize the grids. To select this mode, set the Breaker Delay parameter
to 0ms.
In rotating phase angle synchronization, the overall PLC control system holds the two
grids at the same amplitudes while keeping the frequencies at slightly different values so
the two grids gradually go in and out of phase. The PLC then requests that the PSM
module synchronize the grids whenever it is safe to do so. To select this mode, set the
Breaker Delay parameter to the non-zero value that corresponds to the time required for
the synchronization contacts to close. See "ANSI Protection Parameters" in chapter 3for
more details on setting the breaker delay.
For safe synchronizing (i.e. connecting the generator grid with the public grid), in addition
to having no faults in either the public or generator grids, the following three parameters
must be within their specified limits:

voltage matching (Delta Voltage between public grid and generator grid, all
measured phase voltages considered)

frequency difference (Delta Frequency between public grid and generator grid)
 angle (Phase Shift between public grid and generator grid — using phase A
voltages)
Voltage Matching
For synchronization, the Grid 2 RMS voltage must be within ±DELTA_VOLT_THR of the
Grid 1 RMS voltage. DELTA_VOLT_THR is a percentage of the measured Grid 1 voltage.
There is no delay for setting or clearing this DeltaVoltOK status bit.
Frequency Difference
For synchronization, the Grid 2 frequency must be within ±DELTA_FREQ_THR of the
Grid 1 frequency. DELTA_FREQ_THR is an absolute frequency difference in Hz.
Chapter 1 PSM Module Description and Specifications
Warning
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