A single-span aeroelastic model of an overhead electrical power transmission line with guyed lattice...
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Transcript of A single-span aeroelastic model of an overhead electrical power transmission line with guyed lattice...
A single-span aeroelastic model of an overhead electrical power transmission line
with guyed lattice towers
A study by
W.E. Lin, E. Savory, R.P. McIntyre, C.S. Vandelaar & J.P.C. King
The University of Western Ontario
With funding from
Friday 15th July 2011, ICWE 13, Amsterdam, The Netherlands
Overview• Scope: design and test a physical model of a section
that failed due to downdraft outflow winds
• Direct comparison of tower and line response to synoptic wind profile versus downdraft outflow wind profile
• Aeroelastic model of a transmission line system with length scaling of 1:100
• In successive order, the experimental model was subjected to boundary layer and downdraft outflow wind forcing in a single test facility
Purpose and motivation
• Examine feasibility of the required design and fabrication
• Characterize the structural response to the two different types of wind forcing
• Why do transmission line failures occur in downdraft winds?
Lattice tower: 44.4 m
Two x-arms
Four guy wires
Two insulators
Two conductor pairs: 488 m span
One lightning shield
Full-scale structure
Model scaling
Model layout
• Distorted horizontal length scaling (Loredo-Souza & Davenport 2001)
• 1:100 length scaling of one line span, for all
Model scaling
Scaling of aerodynamic drag
D = CD · 0.5 ·· U2 · A
• Drag coefficients from Mara et al. (2010) section model tests
3-D assembly 2-D projection
• Projected areas from CAD model
• Lattice tower modelled as an equivalent mast
Model scaling
• Scaling of flexural rigidity about two axes
p p
n
n
conductor
conductor
tower
Model scaling
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Section 1 (z = 0 to 0.06 m)
Section 2 (0.06 to 0.07)
Section 3 (0.07 to 0.10)
Sections 4, 5, 6 (0.10 to 0.41)
Guy wire x-arm (0.35 to 0.38)
Conductor x-arm (0.38 to 0.41)
Section 7 (0.41 to 0.45)
Total (z = 0 to 0.45 m)
tow
er
reg
ion
mass (g)
scaled lattice tower ± 2.5 %
mast model
Model installation
Response to boundary layer wind forcing
• ASCE (2010):
Subconductor oscillation at 0.15 to 10 Hz
Galloping at 0.08 to 3 Hz
• Conductor axial force spectra also had spectral peak at 0.6 Hz with 0.5 Hz bandwidth
• Spectral peak centred at 0.6 Hz (full-scale) with bandwidth of 0.4 Hz (f-s)
Response to boundary layer wind forcing
Response to downdraft outflow wind forcing
Response to downdraft outflow wind forcing
BL
Comparison of peak responses
across-wind
along-wind
across-wind
along-wind
Comparison of peak responses1.3 to 1.7
1.5
0.96 to 2.4
1.84
1.3 to 1.7
1.5
0.96 to 2.4
1.84
1.3 to 1.7
1.5
0.96 to 2.4
1.84
Conclusions
• Observed imbalance between peak load on the upstream and downstream conductors was particularly severe for the downdraft outflow forcing
• Fundamental mode of vibration was evident, but response was generally quasi-static to both types of wind forcing
• Resonant dynamic response was less significant with downdraft outflow wind forcing
• Peak values of tower response to downdraft outflow forcing were significantly larger
Future work
• Yaw angle effects
AcknowledgementsFinancial sponsors:
• Natural Sciences & Engineering Research Council of Canada
•
• Centre for Energy Advancement through Technological Innovation
•
• Association of Universities and Colleges of Canada
• www.mitacs.ca
Colleagues: J.K. Galsworthy, T.G. Mara, K. Barker, S. Hewlette, G. Dafoe,
AFM Research Group (www.eng.uwo.ca/research/afm/main.htm)