User Manual Chapter 1
GFK-2749A Jan 2020
PSM Module Description and Specifications 11
ANSI Functions for GRID 2 (Generator/Generator Grid)
Protection
WARNING
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.
ANSI 25 – Generator & Public Grid Synchronization
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 3 for 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.
Voltage Matching
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.
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