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2.1.3.8 ET Sistema de amortiguamiento

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NUOVA ELETTROMECCANICA SUD S.P.A.
Doc. n° DSA EBB 03/13
Registered office: Via dell'Arco di S. Calisto, 24/B – 00153 Roma – Italia
+39 06 58335535 +39 06 59335495
Factory: Zona Industriale – 89052 Campo Calabro (RC) – Italia
+39 0965 792111 +39 0965 792222
info@nesspa.it www.nesspa.it
DAMPING SYSTEM ANALYSIS
Performed on phase conductors, shield wire and OPGW
pertaining to 230 kV OHTL
Armenia connection La Virginia - La Hermosa
COLOMBIA
02
01
00
1th/June/13
23th/Apr/13
28th/Mar/13
OPGW updated with the actual parameters
Some bugs fixed
First issue
Rev.
Date
Description
Page 1 of 7
Nuova Elettromeccanica Sud S.p.A.
Doc. n° DSA EBB 03/13 rev.2
of 1th/June/13
1. Foreword
On request of EBB, damping studies have been performed on the following cables of the
above captioned project:
• ACAR 600 12/7 (Φ 22.58mm) for twin bundle phase conductors,
• GW AWG 7#9 (Φ 8.71mm) for shield wire
• OPGW AFL DNO-9663 (Φ 10.8mm)
The studies have been performed by mean of a specific computer program, called Tecnosoft
III, designed for vibration analysis of overhead cables exposed to natural wind. By using this
program, it is possible to calculate aeolian vibration amplitudes and the relevant alternating
bending strains on the conductor, establishing the balance between the energy introduced by
the wind and the energy dissipated by the conductor, with and without the application of vibration dampers and/or spacers.
In this report, the results of the studies are reported together with the recommendations for the
quantity and the positioning of the spacers and the vibration dampers. These recommendations are valid for spacers and vibration dampers produced by the company NES only.
2. Line parameters
The parameters of the lines under examination have been derived from the input data files for
damping study provided by EBB.
The nature of terrain is Mountainous.
The tensile loads are available at the EDS after creep at 15 °C. The values are:
• ACAR 600 12/7 = 12.52 kN
• GW AWG 7#9 = 6.74 kN
• OPGW AFL DNO-9663 = 5.95 kN (12 % UTS)
Minimum Span = 90 m
Average Span = 473m
Maximum Span = 1101 m.
The average temperature of the coldest month of the year is 5 °C.
3. Damping Systems
The damping system proposed for the twin bundle of ACAR 600 12/7 consists of NES twin spacerdamper type 8.40.02.861.
The damping system proposed for the GW AWG 7#9 consists of NES vibration damper type
8.50.01.401.
The damping system proposed for the OPGW AFL DNO-9663 consists of NES vibration damper
type 8.50.01.470. In case to install the damper outward the suspension clamp or tension clamp, the
additional rods set 8.45.37.833 is needed.
4. Calculation parameters
The tensile load of the ACAR 600 12/7 conductor has been taken equal to 12.9 kN corresponding to
the load condition of the average span at the average temperature of the coldest month of the year.
The tensile load of the GW AWG 7#9 shield wire has been taken equal to 7 kN corresponding to
the load condition of the average spans at the average temperature of the coldest month of the year.
The tensile load of the OPGW AFL DNO-9663 has been taken equal to 6.06 kN corresponding to
the load condition of the average spans at the average temperature of the coldest month of the year.
Armor rods at the suspension clamp for the conductors and shield wire have been considered. Armor
Page 2 of 7
Nuova Elettromeccanica Sud S.p.A.
Doc. n° DSA EBB 03/13 rev.2
of 1th/June/13
Grip Suspension clamps and preformed tension clamps have been considered for the OPGW.
The spacers are distributed along the spans in accordance with the in-span positioning tables NES
INST EBB 02/13.
The assumed wind functions Single (Var2) and Bundle (Var2), have been considered at a turbulence level of 8% which is typical of the above mentioned areas.
5. Evaluation criterion
To evaluate the damping system performance, the criterion of the maximum allowable bending
strain, based on IEEE paper 31TP65-156 [1], has been applied.
For the ACAR 600 12/7, containing aluminum elementary wires in outer layer, a bending strain of
150 microstrains is internationally accepted as the limit below which no fatigue failure o conductor
strands can occur.
For the OPGW and shield wire, containing aluminum clad steel elementary wires in outer layer, a
bending strain of 225 microstrains is internationally accepted as the limit below which no fatigue
failure o conductor strands can occur.
The criterion of the maximum allowable bending strain is the most severe evaluation criterion
compared with the CIGRE evaluation procedure [2]. This procedure is based on the calculation of
the conductor lifetime by means of the Miner's theory. However, the CIGRE method can be
adopted only when the statistical distribution of the wind speed is available.
6. Calculation results
6.1 ACAR 600 12/7
The calculation has been performed first on the conductor alone (see Annex 1) and then on the
same conductor equipped with the damping system composed by vibration dampers and flexible
spacers.
The bending strains on the conductor alone resulted to be above the safety limit of 150 microstrains
in the lower frequency range of vibrations. These vibrations are excited by low speed winds that, in
a normal wind speed distribution, have the higher percentage of presence. Thus, the application of
damping system is justified.
The calculation of the optimum quantity and positioning of the damping system shows that the
spacer-damper 8.40.02.861 (distributed in accordance with the in-span positioning tables NES
INST EBB 02/13) can control the vibration levels within safety limit when installed according to
the following criteria (see Annex 2 about the average span and Annex 3 about the longest span)
6.2 GW AWG 7#9
The calculation has been performed first on the cable alone (see Annex 4) and then on the same
equipped with vibration dampers.
The bending strains on the shield wire alone resulted to be above the safety limit of 225 microstrains in the lower frequency range of vibrations. These vibrations are excited by low speed
winds that, in a normal wind speed distribution, have the higher percentage of presence. Thus, the
application of damping system is justified.
The calculation of the optimum quantity and positioning of the vibration dampers shows that the
vibration damper type 8.50.01.401 can control the vibration levels within safety limit when installed according to the following criteria:
• For span lengths up to 600 m, one vibration damper per span, positioned at 0.8 m from the suspension (or tension) clamp edge (see Annex 5).
Page 3 of 7
Nuova Elettromeccanica Sud S.p.A.
of 1th/June/13
Doc. n° DSA EBB 03/13 rev.2
•
For longer spans, two vibration dampers per span (one at a span extremity), positioned at 0.8 m
from the suspension (or tension) clamp edge (see Annex 6).
6.3 OPGW AFL DNO-9663
The calculation has been performed first on the cable alone (see Annex 7) and then on the same
equipped with vibration dampers.
The bending strains on the shield wire alone resulted to be well above the safety limit of 225 microstrains in a wide frequency range, thus the application of vibration dampers is justified.
The calculation of the optimum quantity and positioning of the vibration dampers shows that the
vibration damper type 8.50.01.470 can control the vibration levels within safety limit when installed according to the following criteria:
• For span lengths up to 400 m, one vibration damper per span, positioned at .52 m from the suspension clamp edge (see Annex 8).
• For span lengths up to 800 m, two vibration dampers per span (one at a span extremity), positioned at .52 m from the suspension clamp edge (see Annex 9).
• For longer spans, three vibration dampers per span (one at a span extremity, two at the other
one), the first one positioned at 0.52 m from the suspension clamp edge, the second one at 0.5
m from the first one (see Annex 10).
For tension clamps, it is recommended to install the same number of dampers recommended for suspensions clamps, installed on the free length of the reinforcing rods set and on reinforcing rod set.
7. Conclusions
According to the calculations described above, the damping systems proposed for the lines in subject can provide an excellent performance in controlling the levels of aeolian vibrations within the
safety limits referred in par. 5.
8. Installation criteria
ACAR 600 12/7
SPACER-DAMPER NES 8.40.02.861
SPAN LENGTH (m)
from
to
0
109
110
155
156
229
230
303
304
376
377
447
448
517
518
585
586
635
636
709
710
784
785
843
844
916
917
968
969
1043
1044
1115
NUMBER PER EACH
SPAN PER PHASE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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Nuova Elettromeccanica Sud S.p.A.
of 1th/June/13
Doc. n° DSA EBB 03/13 rev.2
SPAN LENGTH (m)
from
to
1116
1179
NUMBER PER EACH
SPAN PER PHASE
17
See in-span positioning tables NES INST EBB 02/13 for details.
GW AWG 7#9 - DAMPER NES 8.50.01.401
SPAN LENGTH (m)
L≤600
L>600
NUMBER PER
EACH SPAN
11
2
DISTANCE OF INSTALLATION FROM CLAMP EDGE (m)
X1=0.77
X1=0.77
OPGW AFL DNO-9663- DAMPER NES 8.50.01.470
SPAN
LENGTH
(m)
L≤400
400<L≤800
L>800
NUMBER OF
DAMPERS PER
EACH SPAN
12
2
33
DISTANCES OF INSTALLATION
(XI= 0.23 m)
ON TENSION CLAMP
ON AGS CLAMP (m)
X1=0.51, (X2=null)
See below
See below
X1=0.51, (X2=null)
X1=0.51, X2= 0.44
See below
For tension clamps, it is recommended to install the vibration dampers on the free length of the reinforcing rods set. The performances of the dampers are independent of the installation side.
1
In case of span between suspension and tension sets, it’s recommended to install the damper at suspension side.
In case of span between suspension and tension sets, it’s recommended to install the damper at suspension side.
3
In case of span between suspension and tension sets, it’s recommended to install two dampers at suspension side.
2
Page 5 of 7
Nuova Elettromeccanica Sud S.p.A.
of 1th/June/13
Doc. n° DSA EBB 03/13 rev.2
References
[1] IEEE
Standardization of conductor vibration measurements
IEEE 31 TP 65-156 Vol. Pas 85 N1, 1966
[2] CIGRE
Recommendation for the evaluation of the lifetime of transmission line conductors
Electra N° 63, 1979
[3] Diana, Gasparetto, Tavano, Cosmai
Field measurement and field data processing on conductor vibration (comparison between
experimental and analytical results).
CIGRE 22-11 September 1982
APPENDIX
THE COMPUTER PROGRAM
The TECNOSOFT III computer program has been developed for the simulation of the dynamic response of single and bundled conductors subjected to the wind induced vibrations. The program require the following input data:
•
Conductor characteristics (stranding, overall diameter, weight, UTS, tensile load).
• Span length. The value to be considered is the actual length of the conductors. However, for
normal spans with the towers at the same altitude, the distance between the towers can be also
used.
•
Type of suspension clamp. The "Clamp strain factor” is set to 1 for metal to metal clamps, while
a values less than one can be considered when AGS clamps or other clamp improving the slippage of the conductor outer strand are used. These clamps can reduce the outer wires dynamic
bending strains.
• Armor rods characteristics, if any (length, rod diameter, number of rods)
• Wind characteristics. The program contains several Wind Power Functions. The most appropriate wind function and the level of wind turbulence are input choices based on an evaluation of
the terrain roughness. The variations of wind turbulence at low wind speed can also be considered. Wind power functions for single and bundled conductors are available. The wind power
functions for bundled conductors take into account that the leeward sub-conductors take less energy form the wind [3].
•
Analytical model of the vibration dampers. It is represented by the dynamic response curve of
the damper. A "Safety factor on dampers" is applied to the calculation to take into account the
normal variation of the damper characteristics during production. This value is normally taken
equal to 1.5, which means a reduction of the damper power of 33.3%. This allows considering,
in the calculation, the worse damper response.
The computer program calculates the bending stiffness and the damping coefficient of the conductor. The conductor bending stiffness, EJ, is derived from the conductor stranding data. The conductor self-damping H is derived from the conductor stranding data and from the tensile load.
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Nuova Elettromeccanica Sud S.p.A.
Doc. n° DSA EBB 03/13 rev.2
of 1th/June/13
The "Exp wavelength" and the "Exp amplitude" are exponents used in the formula for the calculation of the energy dissipated by the vibrating conductor and for the calculation of the conductor
self-damping parameter H.
The above exponents have been determined by laboratory tests performed by various researchers.
The optimum position and the quantity of the vibration dampers per span are calculated by means
of a TECNOSOFT III sub-program called "Optimization". The input data for this sub-program are
the analytical model of the vibration damper, the wind power function adopted, the conductor parameters and the characteristics of the armor rods, if any.
After the set up of the input data, the program is ready to perform the required calculations. The
following span configurations can be analyzed in term of vibration behavior. The results are generally presented in graphical form, but are also available in tabulation form.
Vibration behavior of a single conductor without dampers.
The variations of the maximum bending strain at the suspension clamps and the variations
of the antinode vibration amplitude are shown in the vibration frequency range.
Vibration behavior of a single conductor with dampers.
The variations of the maximum bending strain at the suspension clamps and at the damper
clamp, together with the variations of the antinode vibration amplitude and of the vibration
amplitude at the damper clamp are shown in the vibration frequency range.
Vibration behavior of a conductor bundle without dampers.
The variations of the maximum bending strain at the suspension clamps and the variations
of the maximum antinode vibration amplitude are shown in the vibration frequency range.
Vibration behavior of a conductor bundle with dampers and spacers or spacers dampers.
The variations of the maximum bending strain at the suspension clamps and at the
damper/spacer damper clamps, together with the variations of the antinode vibration amplitude and the vibration amplitude at the damper clamp are shown in the frequency range.
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