ABB REC670 Applications Manual page 271

1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual
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Frequency or Resonant Frequency
IEC12000611 V2 EN-US
Figure 99: Typical stress magnification factor curve according ANSI/IEEE
C37.106-2003 Standard
Each turbine manufactured for different design of blades has various time restriction
limits for various frequency bands. The time limits depend on the natural frequencies
of the blades inside the turbine, corrosion and erosion of the blade edges and additional
loss of blade lifetime during the abnormal operating conditions.
The frequency limitations and their time restrictions for different types of turbines are
similar in many aspects with steam turbine limitations. Certain differences in design
and applications may result in different protective requirements. Therefore, for
different type of turbine systems, different recommendations on the time restriction
limits are specified by the manufacturer.
However, the IEEE/ANSI C37.106-2003 standard "Guide for Abnormal Frequency
Protection for Power Generating Plants" provides some examples where the time
accumulated within each frequency range is as shown in Figure 100.
+
1.0
Ratio
IEC12000611-2-en.vsd
Section 10
Frequency protection
265