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An investigation of welded and cast joints for A.C.S.R. conductors Tsou, Shang-Jen 1948

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AN INVESTIGATION OF WELDED AND CAST JOINTS FOR A.C.S.R. CONDUCTORS by Shang-Jen Tsou A Thesis Submitted in Partial Fulfilment of The Requirements for the Degree of MASTER 'OF APPLIED SCIENCE In the Department of MECHANICAL AND ELECTRICAL ENGINEERING 3 7 Cap I Approved: In Charge of Major Work H^d of --Department'. THE UNIVERSITY OF BRITISH COLUMBIA September, AN INVESTIGATION OF WELDED AND CAST JOINTS . FOR A.C.S.R. CONDUCTORS In the conventional Joint9 for aluminum core steel reinforced (A.C.S.R.) conductors the path of the electric current in the outer strands passes through two mechanical contacts, while for the inner strands the number of contacts i s considerably more. It i s recog-nized that the present techniques of making compression Joints i s considered by many to be satisfactory. However, i t i s obvious that a continuous metal Joint would be superior. Recent advances in welding make the con-struction of such a Joint possible. In the Joints constructed for experimental purposes each strand of a 3 9 7 , 5 0 0 c M conductor wasi brought out between two aluminium sleeves and Heliarc welded. In the finished Joint the weld bonds the inner and outer sleeves and the Individual conductors. The ends of the Joint are compressed to prevent ingress of mol3ture which may be injurious to the conventional steel compression sleeve which connects the steel cores to-gether. Tests of the Individual strand resistance as measured between the central part of the Joint and the s t r a n d s showed the s t r a n d r e s i s t a n c e s to be u n i f o r m and equal to an e q u i v a l e n t l e n g t h o f s t r a n d . T h i s shows t h a t each s t r a n d was s a t i s f a c t o r i l y connected a t the w e l d . O v e r a l l r e s i s t a n c e , heat and mechanical t e s t s i n d i c a t e t h a t the welded-compress ion j o i n t should be s a t i s f a c t o r y i n the f i e l d . I n a d d i t i o n to the welded-compress lon j o i n t two c a s t - a l u m i n i u m J o i n t s were a l s o i n v e s t i g a t e d . These, however, due to poor bonding were found u n -s a t i s f a c t o r y . Shang-Jen Tsou U n i v e r s i t y o f B r i t i s h Columbia September, 13k&. 2 TABLE OP CONTENTS PAGE 1 . Introduction 3 II. Investigation 8 A. Welded-compression joint for A.C.S.R. conductors & 1 . Procedure & 2 . Electrical conductivity tests ... . * 1 1 3 . Heating test .... 1 3 k-. Tensile strength test 1 5 5 . Microscopic examination , 1 J 6. Heliarc welding technique 21. B. Aluminum cast joint for A.C.S.R. conductors 2k-1 . Procedure . 2 ^ 2 . Electrical conductivity tests 2 6 3 . Heating test 2 6 Tensile strength test 2& 5 . Microscopic examination 29 III. Discussion and Prospectus 3 1 IV. References 3 3 V. Acknowledgements •• 3 5 VI. Drawings • 3*> 3 AN INVESTIGATION OF WELDED AND CAST JOINTS FOR A.C.S.R. CONDUCTORS 1. INTRODUCTION An important consideration in the installation of power transmission lines i s the making of conductor Joints which w i l l retain throughout the useful l i f e of the conductor both high electrical conductivity and mechanical strength. During service conductors are exposed to extreme variations in temperature and tension, vibration stresses, short-circuit currents and atmospheric corrosion for a period of 5° years or more. The main d i f f i c u l t y in making a satisfactory joint in Aluminum-Core-Steel Reinforced (A.C.S.R.) conductors i s due to the formation of aluminum oxide on the surface of the strands. Several types of joints have been developed and. among them are the bolted and clamped joints, twisted sleeve joints, threaded compression joints, core joints and compression sleeve joints. Most of .these, with the exception of the compression sleeve joint have been found unsatisfactory for large size A.C.S.R. conductors. x According to Gordon B. Tebors (7) investigations deterioration of twisted sleeve joints i s indicated f i r s t by increase of resistance and heating. This i s followed in x A l l numbered references given i n References. extreme cases by the appearance of holes in the sleeve, pro-duced by internal arcing, and f i n a l l y the conductor f a i l s mechanically at or near one end of the sleeve. •The threaded compression joints have a very bad operating record. After 20 years in service on a 110 kv line, several hundred such joints i n 312,000 cm A.C.S.R. conductors were tested, and more than ^>0% had a resistance greater than 10 time normal. In most cases the high resistance was i n the threaded connection. According to the Report made by W.J. Nichols (6) on a l l 132 kv lines, prior to 1933, the A.C.S.R. conductors were jointed i n midspan by cone-type joints gripping the steel and aluminum strands separately by means of steel and aluminum cones respectively. These joints were thoroughly tested before adoption, both for mechanical strength, 95$ °f the breaking strength of the conductor being required, and for conductivity, the resistance having to be less than that of an equivalent length of conductor. In 193^, the compression joint was introduced on new lines and for the maintenance of existing lines. The reason for this change x^ ras the increasing number of failures of cone-type joints. The cone-joint failures began to take a general form of break in the conductor, usually some 12 - IS* inches from one end of the joint. There was evidence of heating at the break and also in the Joint, the steel strands showing signs of heating over the length between the joint and the break. This evidence pointed to 5 high resistance in the. aluminum portion of the joint, with the resultant transfer of current to the steel core i n the joint and back to the aluminum strands a short distance out-side i t . This high resistance was checked and i t was found that the resistance of many joints had increased seriously in service. Experience with compression sleeve joints (7) has been generally satisfactory. Occasionally, hoi^ever, an aluminum conductor burns off at or near a compression sleeve. Examination usually discloses improper cleaning of strands of the conductor and the sleeve. The resultant high resistance causes heating, arcing, annealing, and f i n a l l y rupture of the conductor. The location of this rupture i s usually just at the entry to the sleeve, but i s sometimes a foot or more away from the sleeve. Investigation i n such cases has shown high inter-strand resistance in the joint with consequent uneven current distribution. The few high-conductivity but over-loaded strands become red-hot i n the vicini t y of the joint. Besides the above-mentioned methods of jointing A.C.S.R. conductors, the A.I.A.G-. in Switzerland has developed so-called Alutherm procedure for welded conductor joints. The original strength of the cable being somewhat diminished in the weld3, joints i n the spans were mechanically reinforced by aluminum sleeves which were pressed onto the cable. Unfortunately there i s very l i t t l e data available on a welded joint by this method. 6 It Is quite clear, that i f the conductors are jointed together by any of these methods, the interface i s essentially a discontinuous region, and there i s a more or less abrupt change in the conditions of current flow from one conductor to the other. If the conductors are welded together, the joint i s mechanically and electrically con-tinuous, and there i s in general less disturbance i n the current flow, provided that the weld i s homogeneous and of uniform conductivity. The art of welding, necessitated by the demands of industry i n wartime, has progressed considerably. A method known as the "HELLIARC" process (l) has been developed which can be used i n the welding of corrosion-resistant metals. The question therefore, arose as to whether this technique could be; applied in making satisfactory A.C.S.R. conductor joints. The idea of a welded-compression joint was dis-cussed with Mr. Laird of the Vancouver Office of the Aluminum Company of Canada, and also with Mr. Underwood of the Van-couver office of the Dominion Oxygen Company. As a result of these discussions these two companies supplied the necessary materials and' some equipment for the construction of two experimental joints. During the investigation certain d i f f i c u l t i e s arose which suggested the idea of making cast aluminum joints containing 12% silicon. Two experimental joints were con-structed and tested. The results of the tests were not as hoped for. 7 However, recent developments in aluminum solders may make this technique feasible and plans are now under way to make up experimental joints employing aluminum solder. The details are discussed in a later section of this thesis. 11. INVESTIGATION A. Welded-compression J o i n t f o r A.C.S.R. Conductors Procedure Two experimental j o i n t s were constructed f o r the i n v e s t i g a t i o n . These are shown i n photographs #1, 2 and 3.. Photograph #4- shows the 1 0 0 -ton model E h y d r a u l i c press used i n making the j o i n t s . I n the development of the welded-compression j o i n t f o r A.C.S.R. conductors, an endeavour was made to use standard p a r t s and equipment i n so f a r as p o s s i b l e . Care was taken to ensure that the e l e c t r i c a l c o n d u c t i v i t y of the j o i n t and the t e n s i l e s t r e n g t h were not impaired by damage to aluminum strands and s t e e l core during assembly or by heating d u r i n g the welding operation. The con-s t r u c t i o n a l d e t a i l s of the experimental j o i n t s are shown i n drawings F i g . 1, 2, and 3» The f o l l o w i n g procedure was employed i n assembling the j o i n t s j F i r s t the aluminum end or outer sleeves were placed on each of two conductors to be j o i n t e d . Then approximately 1$ inches of the aluminum strands of one conductor were unwound and fanned out. Care was taken not to unduly bend, the strands d u r i n g t h i s o p e r a t i o n . The i n n e r sleeve was then p l a c e d over the s t e e l core o f t h i s conductor. Next, the strands of the.other conductor 9 Photograph #1 showing the component p a r t s of the welded-compression j o i n t (A) standard s t e e l sleeve (B) Inner aluminum sleeve (C) End or outer sleeves. Photograph #2 showing welded-aluminum compression j o i n t p r i o r to welding. Photograph #3 shoving ( l & 2 ) welded-aluminum compression j o i n t s and (3 & *0 cast aluminum j o i n t s p r i o r to t e s t i n g . Photograph #K, Hydraulic compressor 100 ton cap a c i t y Model E. 11 were fanned out back to about k- inches. The steel sleeve was then put i n place and the steel compress-ion Joint made in the conventional manner. Following this the inner aluminum sleeve was placed centrally over the steel sleeve and compressed in place. The aluminum strands were then returned more or less to their original position i n such a manner that the ends of the strands lay along the outer ends of the inner sleeve. The end or outer sleeves were then driven in place so that the ends of the strands were held firmly as shown in photograph #2. The two ends of each outer sleeve were then compressed ; and the ends of the strands were welded together and to the sleeves by Heliarc welding. Elec t r i c a l Conductivity Test. In general i t may be stated that a joint which has a low resistance i n i t i a l l y may be expected to give satisfactory service. For reference the resistance of a joint i s compared with that of the equivalent length of conductor. In this particular case the specifications on 3 9 7 , 5 0 0 C.M. A.C.S.R. conductors are as follows: Number of aluminum strands 26 Number of layers . 2 Diameter of aluminum strand ... O . I 2 3 6 " 12 Number of s t e e l strands 7 Diameter of s t e e l strand O.O96I Outside diameter of the conductor .... 0.7^3 Ultimate strength, pounds l6l90# Weight, pounds per mile 2&S5# Approximate current c a p a c i t y 59° amp. Resistance at 50°C fo.r 60 c y c l e , ohms per conductor per mile 0.259 ohms o , Resistance at 25 C f o r 50 c y c l e , ohms per conductor per mile .............. 0.235 ohms. The f o l l o w i n g r e s i s t a n c e s were obtained w i t h an Evershed and Vignoles "Ductor": The r e s u l t was as f o l l o w s : (Room temperature 20 C) Resistance of £97,500 C.M. A.C.S.R. 44 microhms per f o o t . Resistance of welded aluminum compression j o i n t No. 1, 23" l o n g . .. 34 microhms Resistance of welded aluminum compression J o i n t No. 2, 25" l o n g .... 40 microhms. From these data i t i s seen that the r e s i s t a n c e . Of.'Joint No. 1 i n terms of the r e s i s t a n c e of an equivalent l e n g t h of the 397,500 A.C.S.R. cable i s 34 x 12 - koM 23 x 44 and that the r e s i s t a n c e of j o i n t No. 2 i s 40 x 12 = 4 3 . 0 % 25 x 44 13 These results are in very close agreement with the figures given by Mr. R. Lemire (5) of the Hydro-Electric Power Commission of Ontario,, which states that a well-made Joint i s about K0% of the resistance of the same length of cable. The welded-compression Joint No. 2 ha3 a .higher resistance than the No. 1. This might explain the fact that the No. 2 joint was welded f i r s t , with a current at 100 amp. which was not high enough. The No. 1 joint was welded at a higher current - 120 amp. which gave a better result. It was found, following a suggestion in Mr. Tebo's paper, that the individual strand resistance as measured between the central part of the joint and strands was uniform and equal to that of an equivalent length of strand. This shows that each strand was satisfactorily connected at the weld. Heating Test. For the heating test an 18* kw, 6 0 0 A , 30 v Hawthorn D.C. generator was used, t'tiis being the only big current source available. A l l the samples of conductor joints were connected in series. The current 'was kept constant by adjusting.the f i e l d current of the generator. During the tests the room temperature was almost constant at 1&|-0C. After two hours time an approximate steady state was reached. 14 The Heating Test was repeated six times, the longest one being continued for ten hours. The results of these tests were almost the same. The temperatures obtained in s t i l l a i r at current loading 7 5 ° amp. for the cable and the welded aluminum compression joints are l i s t e d in Table 1 and plotted in Pig. 4. Taking the average steady state temperature rise for cable and for the joints, the following results are obtained: Temperature rise for the cable 118° _ 1 2 L 5 0 . 9 9 . 5 ° c . Temperature rise for Joint No. 1 SO0 - 18 .5° =: 6 l . 5°C. Temperature rise for joint No. 2 84° - 13 .5° » 65.5°C. The temperature rise of the joints In percent-age with respect to the cable: For welded-compression joint No. 1 i s For welded-compressicm joint No. 2 §5J5 9 66% 9 9 . 5 4 These results indicate that the welded aluminum compression joint has a lower temperature rise and better conductivity than the cable i t s e l f which meets the essential requirement for conductor-15 joints i n transmission lines. TABLE 1 Cable and Welded-compres3ion joint Temperatures obtained i n s t i l l air with a current of 75° Amperes DC. Time Joint No.. 1 Joint No. 2 Cable 0-00 0-05 0-10 0-15 0-20 0-25 0-30 0-40 0-45 0-50 0- 55 1- 00 1-10 1-20 1-30 1-40 1- 50 2- 00 125.5° 22.0 29.0 34.5 46.0 51.0 55.0 59.0 62.0 65.0 67.5 72.0 74.5 77.4 79.5 s o . o 77.5 i3,5°c 22 30.0 J 5 55 ,0 59.0 63.0 65 .0 69.0 72.0 75.0 32.6 84.5 34.4 34 .0 79.0 13.5 40 .0 62.0 lh5 34.0 92.0 97.5 101.5 105.0 IO5.5 110.0 112.0 114.0 116.3 119.0 122.5 113.0 116.0 107.0 4. Tensile Strength Test. The tensile strength test was made in the Federal Forest Products Laboratory at the University of Br i t i s h Columbia. In order to provide adequate gripping by the stamps of the testing machine, standard steel compression sleeves, and short pieces of 16 Photograph #5 showing the r e s u l t s o f t e n s i l e t e s t on experimental J o i n t #1. The break o c c u r r e d i n the s p e c i a l g r i p shown at the l e f t . 17 aluminum sleeving were compressed on the ends of the experimental cables. The overall length of each joint plus two cables ends was approximately 76 inches. Only one sample joint (#l) was tested. It was found to break at 15,200 pounds ultimate in the special grip as shown in photograph #5. The welded-compression joint was unaffected and there was no measurable permanent elongation. The elongation of the cable i t s e l f was 77 1/3" - 76" x 100 - 2.1# 76" - 23" As was mentioned previously the ultimate strength of 397,500 A.C.S.R. conductor i s 16,190 pounds. It i s therefore seen that the test-load applied was approximately Sk-% of maximum for the cable. This i s quite satisfactory as the safety factor of the joint i s at least 1.9 since the break occurred in the cable grip. Normally a safety factor of 2 to 2.2 i s used. The effect of compressing the inner end of the outer sleeve i s shown in photographs #6 and 7. While the damage to the strands in this case was not detrimental excessive flattening could cause over-heating. Microscopic Examination In order to ascertain the effect of heating due IS to the welding operation the folloxtfing mlcro3copic examinations were made of the steel core and the aluminum strands and sleeves. (I) Steel Cores. Two specimens of the steel core were examined; one from the welded compression joint and the other from unheated piece of conductor. Examination of the micro-photographs (photographs #3-9) shows that no there is^apparent difference in the micro-structure of the steel cores. (II) Welded Aluminum. An examination of the welded aluminum was made by microphotographlng a longitudinal section of the welded joint. A longitudinal section was used instead of a cross-section because i t was impossible to determine the actual position of the ends of the welded strands inside the Joint. The microstructure of the longitudinal section i s shown in photograph #10. Photograph #6. Showing damage to strands due to compression of the outer sleeve. Photograph #7. Showing the Junction of the inner and outer sleeves, strands and steel core. 20 F T % * - ^ r Photograph #&*. M i c r o s t r u c t u r e o f unheated s t e e l s t r a n d and p o r t i o n o f s t e e l s l e e v e . 4— S t e e l s leeve 4 — Z i n c c o a t i n g on s t e e l s t r a n d 4 — S t e e l s t r a n d . JESB Photograph #9. M i c r o s t r u c t u r e o f heated s t e e l s t r a n d and p o r t i o n of s t e e l s l e e v e . *./ 4— S t e e l s leeve 4— Z i n c c o a t i n g on s t e e l s t r a n d . <f— S t e e l s t r a n d . M a g n i f i c a t i o n - 200 Exposure - 40 seconds Treatment - P i c r i c a c i d e t c h i n g . 21 Photograph #10 Micro s t r u c t u r e of welded aluminum strand and sleeve. -Weld ( l e f t - h a n d p o r t i o n ) -Strand " v M a g n i f i c a t i o n Expo sure Treatment 120X 1 minute H F 0.5 cc and H20 9 9 . 5 cc. Examination of the m i c r o s t r u c t u r e shows that there i s e x c e l l e n t bonding between the con-ductor strand and the aluminum sleeve. This s u b s t a n t i a t e s the r e s u l t s of the heating t e s t . 6. H e l l a r c Welding Technique. H e l i a r c welding ( l ) i s an e l e c t r i c a r c -welding process. H i g h l y concentrated heat i s produced by an arc drawn between the work and a s i n g l e , v i r t u a l l y non-consumable, tungsten elec t r o d e . H e l i a r c welding d i f f e r s from other a r c -welding processes i n that the welding zone i s at a l l times s h i e l d e d by a sheath of i n e r t gas that excludes the o x i d i z i n g atmosphere. Argon, the 22 inert gas most generally used, i s fed through a nozzle surrounding the electrode in the head of the Heliarc torch, and flows out to blanket completely the electrode, the arc, and the weld puddle. This protective blanket of inert gas i s the unique feature of the process; because of -it, aluminum can now be successfully fusion-welded without the aid of flux, which was never possible before. With Heliarc welding, there i s no spatter or deposition of chemical salts, and no cleaning i s required. The completed weld, i f properly made,.is smooth and clean, and most cases require no finishing treatment of any kind. The selection of welding current depends on the type of metal welded. For example, direct current with reverse polarity was originally used for the Heliarc welding of magnesium, but i s not recommended for work on any other metal. Direct current with straight polarity i s suitable for welding stainless steel, copper, and copper alloys but should not be used on magnesium or aluminum, Heliarc welding i s also widely used with alternating current. Research has revealed-that a high frequency stabilization current super-imposed on alternating current gives better result 23 than when low-frequency welding current alone i s used. High-frequency stabilized alternating current in combination with the advantages of argon gas, has made possible the welding of aluminum without flux. The standard torch can be used with either direct or alternating current. Fitted to the rear of the handle are three lengths of hose. The f i r s t supplies argon, and the second supplies cooling water which circulates through the body of the torch. The third hose carries the power cable and also serves as an outlet for the cool-ing water. Thus, the power cable i s completely surrounded by water. This feature makes i t possible to carry extremely high currents on a relatively small, light, and flexible cable. With a water flow of less than one pint a minute, the torch has a normal maximum rating of 2 5 0 amperes. Full protection against overheating of the torch due to failure, of the water supply i s afforded by a special fuse inserted in the . cable circuit which automatically shuts off the power. The argon supply i s conducted through the body of the torch and emerges from the gas orifices i n the head of the torch. It i s then 24 guided down toward the weld puddle hy the gas-shielding cup which surrounds the tungsten electrode, B, Aluminum Cast Joint for A.C.S.R. As mentioned in the introduction the conductor joint should possess high electrical conductivity and mechanical strength and i t should retain these qualities through the entire useful l i f e of the conductor. The welded-compression joint has "been shown by experiment to possess these requirements. However, in making this type of joint'considerable equipment i s required and the pro-cedure i s rather complicated. For these reasons a cast-aluminum joint was investigated. 1. Procedure. Two experimental cast-joints were constructed for investigation. These are shown in photograph #3. The mould for making the joints i s shown i n photograph #11. The mould i s made from a piece of 1^ -" diameter steel pipe about two feet long. The pipe was spl i t i n two longitudinally and jointed to-gether by means of 3 pairs of l-g-" hinges. The mould shown in the photograph was later modified by d r i l l -ing two 7/3" diameter holes 11§" apart to replace the V slot shown. These two holes provide the inlet 25 and outlet for the casting metal. In assembling the joint, the two layers of aluminum strands were cut back approximately 3 A " for inner layer, and l | - H for the outer layer. In order to prevent the moulten metal from damaging the aluminum strands at the end of the cast-joint two short pieces of 1" outer diameter aluminum conduit were placed at each end of the joint, so a3 to form an integral part of the joint. The connection of steel cores of the cable was made with the conventional steel compression sleeve. The leakage of moulten metal from the ends of the mould was pre-vented by two split steel rings. These details are shown also in photograph #11. Photograph #11 showing the mould and component parts of the cast-aluminum Joint. 26 P r i o r to c a s t i n g the aluminum j o i n t a l l surface d i r t was cleaned from the strands and the mould was preheated to 350°F w i t h a g a s o l i n e t o r c h . The cast metal was poured at a temperature of 135°°F. The cast-aluminum j o i n t s which are shown i n photograph #3 p r i o r to.the t e s t i n g are approximately 13" long "and 1-g-" outside diameter. E l e c t r i c a l C o n d u c t i v i t y Test. The e l e c t r i c a l r e s i s t a n c e as determined i f i t h an* Evershed and Vi g n o l e s "Ducter" were as f o l l o w s : Resistance of cast-aluminum j o i n t #3, 13" long, 36 microhms. Resistance of cast-aluminum j o i n t #4, 18" long, 3S* microhms. From these data i t i s 3 e e n that the r e s i s t a n c e of j o i n t s #3 and #4 i n terms of the equivalent l e n g t h of397500 cm. A.C.S.R. conductor-are r e s p e c t i v e l y : 13 x 44 and 33 x 12 » 5 ^ . 13 x 44 Heatlng Test of Cast J o i n t s . The heating t e s t f o r the cast j o i n t s was made at the same time as the welded-compression j o i n t s . The r e s u l t s are l i s t e d i n the Table 11 and p l o t t e d i n F i g . 4. The average steady s t a t e temperature of the cast 27 j o i n t No. y at the end of two hours was found to be 112°C which was very c l o s e to, the temperature of the cable, i . e . 113°C. The average steady s t a t e tempera-tur e of the cast j o i n t No. 4 was found to be l 6 o ° . I t i s to be noted that t h i s temperature i s higher than the temperature of the cable. These r e s u l t s i n d i c a t e u n s a t i s f a c t o r y bonding of the aluminum strands and the c a s t i n g . TABLE 11 Cable and C a s t - j o i n t Temperatures Obtained i n S t i l l A i r w i t h a Current of 75° amperes D.C. Time J o i n t No. 3 Join t -No Cable 0-00 0-05 0-10 0-15 0-20 0-25 0-30 0-35 0-40 0-45 0-50 0- 55 1- 00 1-10 1-20 1-30 1-40 1- 50 2- 00 i g . 5 ° c 27.5 A'5 43.5 53.0 66.0 73-0 34.0 33.0 91.0 94.0 97.0. 102 .5 105.5 109.2 111.0 112.0 112.0 13 5 2 73 3l 103 113 127 133 140.0 144.0 143 .5 152.0 155,0 161.0 165.0 167.0 163.0 163.0 165.0 5 ° c 0 13 .5 40 .0 • 62.5 34.0 92.0 97.5 101.5 105.0 105.5 110.0 112.0 114 .0 116.3 119.0 122.5 113 .0 116.0 ' 107.0 23 4. T e n s i l e Strength Test. One sample of the j o i n t (#4) was tes t e d i n a s i m i l a r manner to the welded-compression j o i n t . This j o i n t which f a i l e d i n the c a s t i n g at an u l t i m a t e strength of 10,140 pounds i s shown i n photograph #12. Photograph #12 showing the t e n s i l e t e s t f a i l u r e of cast-aluminum j o i n t i n the c a s t i n g . 29 Microscopic Examination. The microstructure of two of the aluminum strands shown in the cross-sectional view of photograph #13 i s shown in photograph #14. Photograph #13 showing cross-sectional view of cast-aluminum Joint. 3 0 Photograph #14 H 2 o 9 9 . 5 cc. The above micro-photograph shows c l e a r l y that there i s u n s a t i s f a c t o r y bonding of the strands and the c a s t i n g . This confirms the r e s u l t s of the r e s i s t a n c e and of the heating t e s t . 31 111. DISCUSSION AND PROSPECTUS I t has been shown i n t h i s l i m i t e d i n v e s t i g a t i o n o f welded-aluminum J o i n t s t h a t : (a) Welding can be s u c c e s s f u l l y used i n making a s u p e r i o r j o i n t i n A . C . S . R . c o n d u c t o r s . (b) The technique a t present must be c o n s i d e r e d as too c o m p l i c a t e d f o r f i e l d use . ( c ) The d e s i g n of the J o i n t should be m o d i f i e d s l i g h t l y as shown i n F i g . 1 and the ends o f the i n n e r s leeve should be o f such a diameter as to a l l o w a l l the s t rands to l i e around the p e r i m e t e r as I n d i c a t e d I n S e c t i o n A - A of F i g . 1. (d) The i n n e r end of the o u t e r s leeve should not be compressed. The c a s t i n g of aluminum J o i n t s by the procedure used i n t h i s i n v e s t i g a t i o n r e s u l t s i n an u n s a t i s f a c t o r y J o i n t . I t i s ev ident t h a t the sur face o f the aluminum s t rands should be t i n n e d . Dur ing t h i s i n v e s t i g a t i o n and f o l l o w i n g the c o n -s t r u c t i o n of the cas t J o i n t i t was l e a r n e d t h a t the aluminum Company of Amer ica (2) and (3) have developed a new type f l u x and s o l d e r w h i c h w i l l permit the s o l d e r i n g o f aluminum c a b l e s . U s i n g these new m a t e r i a l s there appears to be two p o s s i b l e methods of making j o i n t s i n A . C . S . R . cab le which w i l l meet a l l e l e c t r i c a l and mechanical requi rements . I t i s t h e r e f o r e p r o -posed t h a t a f t e r making the c o n v e n t i o n a l s t e e l compression 32 s leeve j o i n t , the s t rands as arranged i n photograph #11 c o u l d be t i n n e d w i t h the s o l d e r . I n s t e a d of u s i n g a r e -movable mould a p i e c e o f aluminum c o n d u i t which has been p r e v i o u s l y t i n n e d on the i n s i d e c o u l d be used as an i n t e g r a l p a r t of the J o i n t . The s o l d e r then c o u l d be poured i n t o the mould to make the c a s t i n g . I f need be the ends o f the c o n d u i t c o u l d be plugged w i t h s o l i d aluminum r i n g s and then compressed s l i g h t l y to reduce weather ing o f the s o l d e r . Another technique which warrants i n v e s t i g a t i o n i s t h a t of making the c o n v e n t i o n a l compression J o i n t w i t h s tandard p a r t s , however, the i n n e r s u r f a c e of the aluminum s leeve should be t i n n e d and a l s o a p o r t i o n o f each c o n -d u c t o r s t r a n d . A f t e r compressing the s leeve the whole J o i n t would be heated to 350°p to a l l o w sweating o f the s o l d e r . I f necessary the J o i n t c o u l d be re-compressed to p r o v i d e a permanent c lamping of the s t r a n d s . I n prospec tus an I n v e s t i g a t i o n i s to be made o f two p o s s i b l e types of j o i n t s j u s t d i s c u s s e d . 33 IV REFERENCES 1. Anderson, R.J. The Heliarc Welding Process. pp. 1-3. Published by the Linde Air Products Company, New York City, New York, 194-6. 2. Ange, C.W. and Mcllveen, E.E. Application of Insulated Aluminum Wire and Cable, pp. IO5 - I I 3 . Electrical World. September 13, 194-7. 3. Braglio, Charles and Cope, R.R. Aluminum as a conductor material In insulated Electrical wires and cables, pp. 1-11. Published by Aluminum Company of America, September 3, 194-7. 4-. Kochli, and Schlltknecht. 150 kv power Transmission Line of the Rhonewerice A.G-. from Morel to p. 1595. S.-E.-V. Bulletin (Sitfiss E l e c t r i c a l Association) No. 22, November, 194-7. 5. Lemire, R., Hydro-Electric Power Commission of Ontario. Letter to Dr. F. Noakes dated July 15, 194-7, dealing with resistance of A.G.S.R. joints on the Barrie-Scarboro Line. 6. Nicholls, W.J, Recent Progress in the Design of the .High Voltage Overhead Lines of the B r i t i s h Grid System, pp. 82-96. The Journal of the Institute of Electrical Engineers, Part 11. April 194-6. 3*4-7» Tebo, Gordon B. Joints and Clamps for Aluminum Conductors. Unpublished Technical paper No. k& Presented to the American Institute of Electrical Engineers in Spokane, Washington, in August, 19^8*. 35 V. ACKNOWLEDGMENTS The author wishes to express his sincere gratitude to F , Noakes for his suggestion of the problem and his untiring interest in i t s treatment. The author also wishes to express his appreciation to the following persons for providing materials and rendering assistance: Mr. Laird of the Vancouver office of the Aluminum Company of Canada. Mr. Underwood of the Vancouver office of. the Dominion Oxygen Company Limited. Mr. Eyford of the B.C. Electric Railway Company Limited. Mr. W. Armstrong, Associate Professor of Metallurgical Engineering, U.B.C. Mr. Alexander of the Federal Forest Products Laboratory at U.B.C. Mr. G.A. Van Dervoort, Chief Operations Engineer, B.C. Power Commission. 

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