Test Report on 3M ACCR 477-T16 Conductor Returned from Xcel Riverside Line after 13 Years of Service in Minneapolis, MN

Transcription

1 Test Report on 3M ACCR 477-T16 Conductor Returned from Xcel Riverside Line after 13 Years of Service in Minneapolis, MN 3M HCC Testing Laboratory November 3, 2015 Phu Trac Quality Quality Specialist: Phu Trac Technical Manager: Dr. Herve Deve Approved Date Phu Trac 11/3/2015 Herve Deve 11/3/2015

2 Test Report on 3M ACCR 477-T16 Conductor Returned from Xcel Riverside Line after 13 Years of Service in Minneapolis, MN Laboratory: 3M HCC Testing Laboratory, St Paul, MN, USA Field Testing on Energized Line: Fall Dec 2014 Date of Laboratory Tests: 1/30/2015 to 2/18/2015 Reference Documents: Appendix A: 3M ACCR 477-T16 specifications Appendix B: Test Method Appendix C: Sag 10 table used for installation in 2001 Introduction 3M ACCR 477 kcmil conductor was first installed on one span of a 115 kv transmission line at Xcel Energy's Riverside Plant in the fall of The 477 kcmil Hawk conductor was installed as a field test for the new conductor. The ACCR line ran from the 511 MW Riverside Plant to the transmission substation. This plant is located on the Mississippi River near Minneapolis, Minnesota. The line operated in conditions that ranged from - 40 o F in the winter to over 100 o F in the summer. During the time this line has been in service, the plant was converted from coal to natural gas combined cycle. When Xcel Energy first installed this line, to our knowledge no one had ever installed a composite conductor of any kind in the U.S. grid. The ACCR conductor and terminations were removed in December 2014 and sent to the 3M lab for testing. The results show that after 13 years in field operation, the conductor strength is well above the predicted strength. The sag tension was measured during the removal process. The measured sag-tension matches the prediction. Test Ref Number. Test Number 1452, 1454, 1464, 1465, and 1476 I. Summary of Results Three conductor samples were tested for tensile strength. Test results ranged from 108% rated breaking strength (RBS) to 110% RBS with an average of 109.5% RBS. Two conductor samples with PLP dead ends attached on one end and resin termination on the other tested 108% of RBS. 2.

3 Individual Aluminum Zirconium (Al-Zr) and Aluminum Matrix Core (AMC) wires passed specification requirements listed in ASTM B941 and ASTM B976. The Sag 10 sag tension table for the 422 feet span was used to install the conductor at an initial tension of 3540 lb at 20 o F in 2001, APPENDIX B. The predicted final tension after creep is 2990 lbs. The sag tension measured after 13 years of service was 2900 lbs at 20 o F. This result compares well to the predicted final tension. It confirms that the measured creep follows the predicted creep and that the sag model is reasonably accurate. II. Summary of Test Procedure: Conductor samples without deadends and conductor samples with PLP deadends were tested for strength, taken straight load to failure. Individual AlZr and AMC core wires were tested to ASTM B941 and ASTM B976. III. Testing Equipment Equipment used for tensile testing was a Roberts Tensile Tester machine model number RTE-LC13 (Serial Number 08142). The tester is capable of testing samples up to 150,000 lbf (670 kn). The load cell was recalibrated on March 28, 2013 by Instron Calibration Laboratory. The load cell has accuracy better than one percent. 1) Picture of Roberts Tensile Tester 2) Picture of the calibration certificate. 3.

4 IV. Test Method Conductor without deadend and conductor with PLP deadend samples were tensile tested using resin end terminations. For more information on tensile strength test methods, please see document Testing of Conductor, Full-Tension Compression Dead-ends, and Splices/Joints for ACCR at Room Temperature. An exception to the described test method is that all strength samples were tested straight load to failure. For AlZr wires, please see ASTM B941. For Aluminum Matrix Core wires, please see ASTM B976 for more information. V. Results The RBS of 477-T16 conductor is 19,200 lbf (85,406 N). Strength test results for the conductor-only samples ranged from 108% to 110% of RBS. Strength test results for the conductor with PLP deadends attached on one end tested to 108% RBS. See Table 1 below for all strength test results. Individual AlZr and AMC core wires were measured for diameter, strength, and conductivity, and all passed ASTM B941 and ASTM B976 specification requirements. See Table 2 below for results. Also, the sag tension was measured prior to taking the line down after 13 years of service. The result of 2900 lbs at 20 o C agreed very well with the expected value of 3000 lbs at 20 o C. See Table 3 for results. Table 1: Table conductor and conductor with PLP deadend strength test results. 4.

5 Sample Test Number Conductor 1452 Conductor 1465 Conductor 1476 Conductor with PLP Deadend 1454 Conductor with PLP Deadend 1464 Description of Method Max Load (lbs) %RBS Failure Mode 477-T16 Conductor from XCEL Riverside Line (Sample 1 of 3) 21, Gauge break. 477-T16 Conductor from XCEL Riverside Line (Sample 2 of 3) 21, Gauge break 477-T16 Conductor from XCEL Riverside Line (Sample 3 of 3) 20, Gauge break. 477-T16 Conductor with PLP Deadend from XCEL Riverside Line (Sample 1 of 2) 20, Gauge break. 477-T16 Conductor with PLP Deadend from XCEL Riverside Line (Sample 1 of 2) 20, Gauge break. Table 2: Average AlZr and Aluminum Matrix Core Wire Properties Sample Property Result Units Specification AlZr Outer Wire Strength 24,384 psi 23,500 Diameter inches /- 1% Conductivity 60.7 %IACS 60.0 AMC Core Wire Conductivity 24.9 %IACS 24.0 Strength 2110 lbs 1699 Table 3: Sag Tension Property Result Prediction after Creep Sag Tension after 13 Years 2900 lbs at 20 F 2990 lbs at 20 F 5.

6 Test Pictures Test 1452 Conductor strength test 6.

7 Test 1454 Conductor with PLP Deadend 7.

8 VI. Analysis / Conclusions Test results show that the 3M ACCR 477-T16 conductor samples all passed the 100% RBS requirement after 13 years of service in Minneapolis, MN. The average of 3 samples was 109% RBS. For conductor samples with PLP deadends attached on one end, both samples passed the 95% sample minimum failure load (SMFL) requirement. The two tests averaged 108% RBS (Figure 2). Figure 1: Load versus Time for conductor with PLP deadend strength tests. 8.

9 Load (lbf) 3M Aluminum Conductor Composite Reinforced Conductor with PLP Deadend Strength Test Test 1454 Test Time (Sec) In addition, AlZr outer wires and AMC core wires passed ASTM specification requirements for diameter, strength, and conductivity. Prior to taking the 477-T16 ACCR conductor down after 13 years of service, the sag tension was measured and found to match very well with the expectation of 2990 lb at 20 o F. The measured sag tension was 2900 lb at 20 o F. VII APPENDIX A: ACCR 477-T16 Conductor Properties Conductor designation Conductor construction Nominal conductor size Aluminum strands Core strands Outer strand material Outer strand shape Layers of outer strands Core material Conductor diameter Conductor weight Rated strength DC 20 C Continuous rating Emergency rating* 477 T16 ACCR Outer Layer Right Hand Lay 470 kcmil (aluminum strands only) 26 each 7 each Aluminum-zirconium alloy Round 2 each Aluminum matrix wire inches ( 2%) pounds/foot ( 4%) 19,200 pounds ohms/mile ( 2.5%) 210 o C 240 o C 9.

10 *1000 hours VIII. APPENDIX B 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 10.

11 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. 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 lbf (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. 11.

12 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 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 477-T16 ACCR conductor, the rate is: 19,200/0.6 = 32,000 lbf/min 85,406/0.6 = 142,343 N/min Install sample in test frame and preload to approximately 1000 lbf (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; 12.

13 (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 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 5.4 to 7.6 ft (1.7 to 2.3 m) SMFL (sample minimum failure load) = 95% RBS. RBS for 477-T16 conductor is 19,200 lbf (85,406 N). SMFL would equal 0.95*19,200 lbf = 18,240 lbf (81,136 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 (10,944 lbf / 48,681 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 /

14 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 (10,944 lbf / 48,681 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

15 IX- APPENDIX C: Sag10 sagging table used in 2001 to sag the line 15.