Frequency Adaptivity And Generator Start-Up Protection - ABB RELION REX640 Technical Manual

1MRS759142 C
11.5
REX640
Technical Manual
value respectively with appropriate quality information. The frequency estimation
requires 160 ms to stabilize after a bad quality signal. Therefore, a delay of 160 ms is
added to the transition from the bad quality. The bad quality of the signal can be due
to restrictions like:
• The source voltage is below 0.02 × U
• The source voltage waveform is discontinuous.
• The source voltage frequency rate of change exceeds 15 Hz/s (including stepwise
frequency changes).
When the bad signal quality is obtained, the nominal or zero (depending on the Def
frequency Sel setting) frequency value is shown with appropriate quality information
in the measurement view. The frequency protection functions are blocked when the
quality is bad, thus the timers and the function outputs are reset. When the frequency
is out of the function block's setting range but within the measurement range, the
protection blocks are running. However, the OPERATE outputs are blocked until the
frequency restores to a valid range.
Frequency adaptivity and generator start-up
protection
Frequency adaptivity enables sensitive and selective protection during the start-up
and shutdown phase of the generator when low frequency and low voltage amplitude
exist at the same time. Sensitive protection is necessary because, for example, the fault
current level in generator internal fault during start-up or shutdown (when field
excitation is not present) may not exceed even the nominal current level.
Frequency adaptivity can be enabled by setting Frequency adaptivity and setting one
UTVTR Frequency adaptivity to "Main frequency source". One additional UTVTR
or ILTCTR can be set to "Backup frequency source". For main or backup frequency
source, all three-phases must be connected. Each TxTR block that is set to Frequency
adaptivity mode enable outputs measurements adapted to either main or backup
source frequency depending on their availability.
See the Preprocessing blocks chapter for more information.
The frequency adaptivity uses the positive-sequence voltage in the frequency tracking
and adapts the DFT, RMS, peak-to-peak and peak measurement accuracies of the
current and voltage inputs by using the tracked frequency in the operation range of
0.2...1.5 xFn. Frequency adaptation starts when the generator terminal positive-
sequence voltage level exceeds 0.04 xUn (minimum level). If frequency adaptivity
backup source is currents their positive sequence must exceed 0.07 xIn to be usable as
backup source. Backup source threshold limit is valid at nominal frequency and
threshold increases when frequency deviates from nominal (up to 0.35 xIn or 0.2 xUn
General function block features
at F .
n n
Section 11
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