1033 accr conductor stress strain test and fittings...

1033 ACCR Conductor

Stress Strain Test and Fittings Tensile Test

NEETRAC Project Number: 06-086

November, 2006

Requested by: Dr. Colin McCullough 3M

Principal Investigator: Paul Springer, PE

Reviewed by: Dale Callaway

A Research Center of the Georgia Institute of Technology

National Electric Energy Testing, Research & Applications Center

1033 ACCR, Dead End Tensile and Conductor Stress-Strain NEETRAC Project Number 06-086 of 12

1033 ACCR Conductor Stress Strain Test and Fittings Tensile Test

NEETRAC Project Number: 06-086

November, 2006

Summary Three AFL dead ends were tested to confirm holding strength exceeds 95% of nominal RBS required by ANSI C119.4. All samples exceeded nominal RBS. Stress-strain tests in accordance with the Aluminum Association’s 1999 guide characterized the elastic and short-term creep properties for 3M 1033 ACCR conductor. Samples

1) Three (3) ACA compression dead ends compressed on 21-foot sections of 1033 ACSR conductor. Connector installation was performed by ACA Conductor Accessories in Spartanburg, South Carolina.

2) Reel of 1033 ACCR conductor for stress-strain tests.

Procedure

I) Connector tensile tests (three dead-ends): Bird caging (excess slack) from the compression operation was worked to the conductor free end. Cast-resin fittings were then installed in accordance with a procedure developed for lab testing of ACCR conductors. Samples were loaded into an MTS tensile machine and pulled to destruction at a rate of 17,000 lbs/min.

II) Stress-strain: Samples were taken from near the center of the reel to ensure properties

are representative of the “as-manufactured” conductor. Bolted clamps were installed on both sides of each cut to prevent any component from shifting. Cast-resin terminations were applied to the sample ends using a procedure designed to preserve the conductor manufacturing pre-stress, and therefore ensure that test samples behave as similar as practical to in-service conductor.

The 1999 Aluminum Association guide for conductor stress-strain testing was followed with one exception: values for the elastic properties of the metal matrix composite (MMC) core were used instead of values provided in the guide. The elastic coefficients in the guide apply to steel core, and therefore are non-applicable for MMC conductor core strands.



Results

Tensile Tests:

Three (3) dead end connectors were pulled to destruction. The stress-strain composite sample was pulled to destruction following the stress strain test. The core sample was tensile tested, but results were not representative because a strand failure occurred at a location damaged during removal of the aluminum strands. Figure 3 shows the tension and actuator displacement data from the tensile machine. The 3M data sheet for 1033 ACCR lists nominal RBS as 35,470 lb.

The following breaking loads were recorded:

Sample # Breaking Load % RBS Failure Mode (lb)

Dead End1: 36,030 102 All strands mid span Dead End2: 36,160 102 Most strands ~2 feet from dead end Dead End3: 37,070 105 Most strands mid span Stress-strain conductor: 36,120 102 All strands mid-span

Figure 1, dead

end sample pre-test Figure 2, typical mid-span break



1033 kcmil, Type 13, 3M Composite ConductorTensile Test Data

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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Crosshead Position (inches)

Load

(lb)

Dead End 1

Dead End 2

Dead End 3

Stress-Strain Composite

RBS

95% RBS Acceptance Criterion

Figure 3, dead end tensile test results

Stress-strain: Detailed Procedure:

Composite conductor (RBS 35,470 lbs):

1) Apply load of 1,000 lbs. Remove sag with a mid-span support 2) Install extensometer, and set to zero. 3) Pull to 30% of RBS (10,641 lbs)* 4) Hold for 30 minutes. 5) Relax load to 1,000 lbs. 6) Pull to 50% RBS (17,740 lbs) 7) Hold for one hour 8) Relax load to 1,000 lb 9) Pull to 70% RBS (24,830 lb) 10) Hold for one hour. 11) Relax load to 1,000 lbs. 12) Pull to 75% RBS (26,600 lbs). 13) Relax load to 1,000 lbs, and remove the extensometer (for its own protection). 14) Pull sample to destruction at 17,000 lbs/min. *Due to a human error, sample was pulled to only 25% RBS, or 8,870 lb. See “Conclusions” for discussion of affect on overall accuracy for the test.



Core strands (nominal rating is 19,183 lbs):

1) Pull to calculated initial tension (in this case, 300 lbs). Remove sag with a mid-span support

2) Install extensometer, and set to zero 3) Pull to same strain as conductor at start of 30% of RBS test (0.0927%) 4) Hold for 30 minutes. 5) Relax load to 300 lbs. 6) Pull to same strain as conductor at start of 50% of RBS test (0.2041%) 7) Hold for one hour. 8) Relax load to 300 lbs. 9) Pull to same strain as conductor at start of 70% of RBS test (0.3159%) 10) Hold for one hour 11) Relax load to 300 lbs. 12) Pull to 75% of the core rating (14,390 lbs) 13) Relax load to 300 lbs, and remove the extensometer (for its own protection). 14) Pull sample to destruction at 10,000 lbs/min.

Figure 4, Composite stress-strain Figure 5, core stress-strain performed to same strains as composite sample



1033 kcmil, Type 13, 3M Composite ConductorStress-Strain Data

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ss (p

si)

Figure 6, plot of raw data recorded during conductor stress-strain test

1033 kcmil, Type 13, 3M Composite ConductorCore Stress-Strain Data

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Stre

ss (p

si)

Figure 7, plot of raw data recorded during core stress-strain test



1033 kcmil, Type 13, 3M Composite ConductorStress-Strain Data

y = 113497x - 12644R2 = 0.9999

y = -63454x2 + 97728x + 1040.5R2 = 0.9999

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si)

Stress-strain data

Initial modulus data

Final modulus data

Linear (Final modulus data)

Poly. (Initial modulus data)

Figure 8, construction of conductor initial and final moduli on stress-strain data

1033 kcmil, Type 13, 3M Composite ConductorStress-Strain Initial and Final Modulus Data, Shifted on Strain Axis for Zero Intercept

y = 112618x - 13149R2 = 0.9998

y = -63455x2 + 99070xR2 = 0.9999

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Translated initial modulus data

Translated final modulus data

Linear (Translated final modulus data)

Poly. (Translated initial modulus data)

Figure 9, conductor stress-strain data translated along strain axis for correct zero intercept



1033 kcmil, Type 13, 3M Composite ConductorCore Stress-Strain Data with Construction of Initial and Final Modulus

y = 329782x - 2541

y = -62411x2 + 334453x + 3311.8

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Core Stress-strain data

Final Modulus Selected Data

Initial Modulus Data

Linear (Final Modulus Selected Data)

Poly. (Initial Modulus Data)

Figure 10, construction of core moduli on stress-strain data

1033 kcmil, Type 13, 3M Composite Conductor Core Translated Moduli

y = -62412x2 + 335687xR2 = 0.9999

y = 329782x - 5800.6

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ss (p

si)

Translated Initial ModulusTranslated Final ModulusPoly. (Translated Initial Modulus)Linear (Translated Final Modulus)

Figure 11, core moduli, data translated along strain axis for correct zero intercept



1033 kcmil, Type 13 ACCR 3M Composite Conductor, Combined Stress-Strain Diagram

Initial Aluminum y = -56440x2 + 61339xFinal Aluminum y = 77129x - 12730

Initial Composite y = -63455x2 + 99070x

Initial Core y = -7015.1x2 + 37731xFinal Core y = 37067x - 649.34

Final Composite y = 112618x - 12818

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Stre

ss*a

rea

ratio

Initial Composite Final Composite

Initial Core Final Core

Initial Aluminum Final Aluminum

Figure 12, combined stress-strain graph (see following text for equations)


Equations for Stress-Strain Properties. Coefficients below are with respect to actual area. Figure 10 contains the equations normalized for area ratio of core and aluminum constituents): Composite Conductor Properties, direct test values: “Initial” Modulus for Stress Strain Curve: Stress (psi) = -63454*(Strain%)2 + 97728*(Strain%) + 1040.5 Final Modulus for Stress Strain Curve: Stress (psi) = 113497*(Strain%) - 12644 Tensile Test, Stress Strain Sample: 36120 lb (102% RBS) Composite Conductor, data shifted along strain axis to provide correct zero strain reference: “Initial” Modulus for Stress Strain Curve: Stress (psi) = -63455*(Strain%)2 + 99070*(Strain%) Final Modulus for Stress Strain Curve: Stress (psi) = 112618*(Strain%) – 13149 Core Strand Properties, direct test values: “Initial” Modulus for Stress Strain Curve: Stress (psi) = -62411*(Strain%)2 + 334453*(Strain%) + 3311.8 Final Modulus for Stress Strain Curve: Stress (psi) = 329782*(Strain%) – 2541 Core Properties, data shifted along strain axis to provide correct zero strain reference: “Initial Modulus” for Stress Strain Curve: Stress (psi) = 62412*(Strain%)2 + 335687*(Strain%) Final Modulus for Stress Strain Curve: Stress (psi) = 399782*(Strain%) – 5801 Aluminum Properties (computed, direct measurement is not possible): “Initial” Modulus for Stress Strain Curve: Stress (psi) = -63587*(Strain%)2 + 69107*Strain Final Modulus for Stress Strain Curve: Stress (psi) = 86896*Strain - 14342

CONCLUSION: The three dead end samples exceeded the ANSI C119.4 strength requirement of 95% RBS. Stress-strain data are provided to support transmission line design programs. The error in setting the load for the 30% load hold was evaluated and resolved in accordance with NEETRAC’s quality management system. The discrepancy was discussed with technical staff at 3M. It was concluded that the 5% change in tension did not significantly change the creep that occurred during the 30 minute load period. It was also observed that creep during the hour at 50% RBS, and during the hour at 70% RBS were both at the correct load. Most of the conductor creep missing from the 30% load hold period would be recovered during two hours at significantly higher loads. Therefore the change in the shape of the initial modulus curve due to the experimental error is small relative to other accepted experimental errors. A mutual decision was reached to accept the test results as representative of the conductor behavior. Figure 11 shows the actual load profile along with the correct target loads.


1033 kcmil, Type 13, 3M Composite ConductorLoad vs. Time

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75% RBS

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30% RBS

Figure 13, recorded load data and target loads for composite stress-strain test EQUIPMENT LISTING

1) MTS Servo-hydraulic tensile machine, Control # CQ 0195 (load and crosshead data) 2) Dynamics Research Corporation (DRC)/NEETRAC cable extensometer, Control # CQ 3002

(strain data). 3) Yokogawa DC100 data acquisition system, Control # CN 3022 (temperature data) 4) HBM linear position indicator for crosshead displacement (for reference only)

REFERENCES AND STANDARDS LISTING

1) ASTM E4, (Calibration of Load Testing Machines) 2) ANSI C119.4, (Connector testing) 3) Aluminum Association Guide for Stress-Strain Testing, 1999


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1033 accr conductor stress strain test and fittings...

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