ABB Relion 670 Series Applications Manual page 241

1MRK 511 401-UUS F
10.4 Frequency time accumulation protection function
FTAQFVR (81A)
10.4.1 Identification
Function description
Frequency time accumulation
protection
10.4.2 Application
Generator prime movers are affected by abnormal frequency disturbances. Significant frequency
deviations from rated frequency occur in case of major disturbances in the system. A rise of
frequency occurs in case of generation surplus, while a lack of generation results in a drop of
frequency.
The turbine blade is designed with its natural frequency adequately far from the rated speed or
multiples of the rated speed of the turbine. This design avoids the mechanical resonant condition,
which can lead to an increased mechanical stress on turbine blade. If the ratio between the turbine
resonant frequencies to the system operating frequency is nearly equal to 1, mechanical stress on
the blades is approximately 300 times the nonresonant operating condition stress values. The
stress magnification factor is shown in the typical resonance curve in Figure 103.
Bay control REC670
Application manual
IEC 61850
identification
FTAQFVR
© Copyright 2017 ABB. All rights reserved
IEC 60617 ANSI/
identification IEEEidentificatio
n
f<> 81A
Section 10
Frequency protection
GUID-124A1F91-44C0-4DB6-8603-CC8CA19AE2A6 v3
GUID-87605DA0-EAA6-4A6C-BF03-7FDB187E1B29 v2
GUID-82CA8336-82BE-42AB-968A-D4F08941C9D0 v3
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