Conductor Strength Tests on ACCR 1622TW T13 Pecos Conductor

Transcription

1 Conductor Strength Tests on ACCR 1622TW T13 Pecos Conductor 3M HCC Testing Laboratory August 5, 2011 Phu Trac Sr. Quality Engineer: Phu Trac Technical Manager: Dr. Herve Deve Lead Development Specialist: Dr. Colin McCullough Approved Date 8/8/2011 c{â gütv 8/8/2011 Herve Deve 8/8/2011 Colin McCullouogh

2 3M ACCR 1622TW-T13 Conductor Strength Tests Laboratory: 3M HCC Testing Laboratory, St Paul, MN, USA Date of Tests: 2/11/11 to 4/12/11 Reference Documents: See Appendix A Test Data: This report contains conductor strength test data for 3M ACCR 1622TW- T13. Test reports for conductor with deadend, conductor with T-Tap and conductor with splice are available in separate reports. Reel Ref Number Manufacturing date: 7/2/2009 Requestor: 3M Test Ref Number. Test Numbers 572, 573, 623 Summary of Results Three conductor samples were tested for tensile strength. The conductor tests averaged 107.4% RBS (Rated Breaking Strength) and fully met specification requirements. Summary of Test Procedure: The conductor was tested as a straight load to failure. Testing Equipment Equipment used for tensile testing is a Roberts Tensile Tester machine model number: RTE-LC13 (Serial Number 08142). The tester is capable of testing samples up to 670 kn. The load cell was recalibrated on 3/28/2011 by Instron Calibration Laboratory. The load cell has accuracy better than 1%.

3 1) Picture of Roberts Tensile Tester 2) Picture of the calibration certificate. Test Method The conductor samples was terminated using cast resin terminations on both ends. For more information on test methods, please see document Testing of Conductor, Full- Tension Compression Dead-ends, and Splices/Joints for ACCR at Room Temperature. Results The RBS (Rated Breaking Strength) of 1622TW-T13 conductor is 246,876 N. The SFML (Sample Minimum Failure Load) for the conductor is 95% of RBS (234,532 N).

4 Table 1: Table showing all three test results and sample information. Sample Test Number Description of Method Max Load (N) %RBS Failure Mode Conductor 572 Conductor 573 Conductor 623 a) Conductor with direct ramp to failure 261, Gauge break a) Conductor with direct ramp to failure 268, Gauge break a) Conductor with direct ramp to failure 265, Gauge break Analysis / Conclusions Test result show that the 3M ACCR 1622TW-T13 samples has a load to failure that exceeded the 95% SMFL. The average conductor strength result was 107.4% RBS. The failure modes for all tests were gauge breaks. Figure 1: Load versus Time for conductor strength tests. 1622TW-13 Conductor Strength Tests Load (N) Test 572 Test 578 Test Time (s)

5 APPENDIX A I. Reference Documents: EN50182 IEC Testing of Conductor, Full-Tension Compression Dead-ends, and Splices/Joints for ACCR at Room Temperature (attached at bottom, section II). II. Test Method Testing of Conductor, Full-Tension Compression Dead-ends, and Splices/Joints for ACCR at Room Temperature 1.0 Goal: This document covers the sample geometry and test procedure for strength testing of ACCR conductor and compression fittings at room temperature. 2.0 Background: Tensile testing of ACCR compression fittings should avoid sample configurations that use multiple fittings within a single tensile test. For example a length of conductor with a compression dead-end at each end, or a length of conductor with a compression dead-end at each end AND a splice in the center. This test configuration is NOT advisable for testing with ACCR. When a compression accessory is pressed onto a conductor sample, there is some loosening of the aluminum strands at the end of the fitting. In ACSR, this can even be quite severe. In an actual transmission line, this is not usually a cause for concern, because in time the loose aluminum will distribute over the length of the span, and looseness is not significant. During testing of ACSR, there is extra cause for concern, since at the site of the aluminum looseness, the steel core will initially carry all the load. Only after the steel has stretched sufficiently to match the extra length of the aluminum looseness, will the aluminum begin to load. Since the aluminum and steel both have a high ductility and so can stretch sufficiently, the full strength of the aluminum and steel will eventually be accessed and the conductor and fittings can be expected to approach the full strength of the conductor. However, with ACCR, the core has a limited strain to failure, and so if there is sufficient looseness in the aluminum from pressing of say two or three fittings in the short length of a tensile sample rather than one, then the core may reach the failure strain before the aluminum reaches it s peak load. Thus the test is a poor representation of the intended use. The preferred method of testing with ACCR is to isolate just one compression fitting in a test length, and apply resin terminations for the loading points, as outlined in section 3.0 below.

6 If aluminum slack does occur after sample harvesting and / or after pressing of the accessories, the slack must be removed prior to applying the resin end terminations. This is done by applying the appropriate size pulling grips to the open ends of the sample length, then bringing the sample up to a load of about 3000 lbs (13.3 kn). Take some rectangular wood blocks and gently tap the conductor sample, working your way down from the accessory towards the pulling grips. Finally, use three hose clamps to clamp down on each open end. Once this step is completed, the sample is now ready for resin end terminations. 3.0 Preferred test configurations for use with ACCR: (a) Dead-end Strength Test Apply one compression dead-end fitting at one end of the sample, and a resin end at the other end. Dead-end Resin (b) Splice/Joint Strength Test Apply one compression splice fitting at the center of the sample, and a resin socket-ends at the two free ends. Resin Splice Resin (c) Conductor Only Strength Test Apply resin socket-ends at the two free ends. Resin Resin 3.1 Method for Attaching Resin End-Sockets Details for preparing resin terminations for ACCR can be found in the Test Method Document entitled, Preparation of ACCR Samples using Resin End-Terminations. This is a relatively conventional procedure with care taken not to spread the core wires excessively and impart too much bending strain. 3.2 Fractures Near Terminations

7 Fractures are considered to be affected by the end termination if they occur within 150 mm (6 inches) of the end termination. These fractures should be bound by a lower rating to account for the stress concentration at and near terminations, such as a 90% RBS requirement, rather than a 95% RBS requirement.. If the event that slipping of wires occurs in the resin terminations (e.g. due to poor wire cleaning, aged resin) and the test result is below 95% RBS, then the test shall be deemed invalid and will be repeated. If the fracture occurs within 150 mm (6 inches) or if slipping of the wires occurs but the test result is still greater then 95% RBS, then the test is deemed a valid test. No retesting will be necessary 4.0 Test Procedure 4.1 Conductor Strength Tests Resin terminations shall be used at all free ends. Sample Gauge Length 10 to 12 ft (3 to 4 m). Conductor is tested as a straight load to failure. Loading shall be applied at a rate equivalent up to 1% strain per minute. This results in a test that takes approximately 40 seconds to reach failure. This is an exception to EN because the loading rate is faster. In load control, the loading rate to produce this strain rate is calculated as: Conductor RBS 0.6 and given in units of lbs/min or N/min Thus for 1622TW-T13 ACCR conductor, the rate is: 55,500/0.6 = 92,500 lbs/min 246,876/0.6 = 411,460 N/min Install sample in test frame and preload to approximately 1000 lbs (4448 N). Setup strain measuring equipment. Check sample straightness and alignment of ends (visual check) and data acquisition software is running. The force and crosshead displacement are measured throughout the test. The temperature of the test laboratory shall be measured and noted. Measure gauge length and zero stress strain and crosshead displacement. Start to record the test. Perform test as indicated. At the end of the test, note; (i) the breaking load of the conductor (ii) location of fracture (iii) ambient temperature during test (iv) Photographs of test set-up (v) photographs of failure location

8 4.2 Deadend strength tests (Room Temperature) Firstly a deadend termination shall be applied at one end of the conductor, and then secondly a resin termination shall be applied at the other end. Sample Gauge Length 7.1 to 8.2 ft (2.16 to 2.5 m) SMFL (sample minimum failure load) = 95% RBS. RBS for 1622TW-T13 conductor is 55,500 lbs (246,876 N). SMFL would equal 0.95*55,500 lbs = 52,725 lbs (234,533 N). One sample shall be tested per IEC / Loading shall be applied at a rate up to 1% strain per minute. This is an exception to IEC because the loading rate is faster. Install sample in test frame. The temperature of the test laboratory shall be measured and noted. Measure the gauge length. Start recording the test. Increase load to 60% SMFL (31,635 lbs / 140,720 N) Hold for 60 minutes. Note any slip distance at the mouth of the deadend. Steadily increase the load to bring to failure. At the end of the test, note; (i) the breaking load of the conductor (ii) location of fracture (iii) slip of the conductor in the DE (iv) photographs of failure location 4.3 Splice/Joint strength tests Firstly a splice is installed at the center of the intended gauge length, joining two pieces of conductor together. Resin terminations are then applied at the two free ends. Sample Gauge Length 14.2 to 16.4 ft (4.3 to 5.0 m) SMFL (sample minimum failure load) = 95% RBS One sample shall be tested per IEC / Loading shall be applied at a rate up to 1% strain per minute. This is an exception to IEC because the loading rate is faster.

9 Install sample in test frame. The temperature of the test laboratory shall be measured and noted. Measure the gauge length. Start recording the test. Increase load to 60% SMFL (31,635 lbs / 140,720 N) Hold for 60 minutes. Note any slip distance at the mouth of the deadend. Increase load to SMFL. Hold for 1 minute. Steadily increase the load to bring to failure. At the end of the test, note; (i) the breaking load of the conductor (ii) location of fracture (iii) slip of the conductor in the splice (iv) photographs of failure location 5.0 Criteria 5.1 Conductor - gauge length failure and > 95% RBS = Passed - within 150 mm of resin ends and >95% RBS = Passed, no retest required - within 150 mm of resin ends, and < 95% RBS retest required 5.2 Deadend termination - no slip of the conductor in the deadend < 95% RBS - no failure of the conductor or the deadend < 95% RBS 5.3 Splice/Joint termination - no slip of the conductor in the splice < 95% RBS - no failure of the conductor or the splice < 95% RBS 6.0 Reference Documents IEC EN 50182

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