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
.
1.0
-
+
Frequency or Resonant Frequency
Ratio
S
tr
e
ss
M
ag
ni
fic
at
io
n
F
ac
to
r
IEC12000611-2-en.vsd
50
100
150
200
250
300
IEC12000611 V2 EN-US
Figure 71:
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
Section 10
1MRK 511 407-UEN C
Frequency protection
186
Phasor measurement unit RES670 2.2 IEC
Application manual
Summary of Contents for Relion RES670
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