ITU-T HDBK JTC-1982 Jointing of Telecommunication Cable Conductors《电信光缆导体结合》.pdf

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1、BI 48bZ59L b7b89 958 INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COM M IlTEE Jointing of Telecommunication Cable conductors Geneva 1982 4862591 0678690 biT INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CON

2、 SU LTATIVE COMMITTEE Jointing of Telecommunication Cable conductors Geneva 1982 ISBN 92-61-01281-7 I.T.U. 4862591 0678692 442 TABLE OF CONTENTS Page PREFACE III INTRODUCTION 1 . 1 Designs of communication cable conductors 1 1.2 Symmetrical pairs . 1 1.2.1 Conductors . 1 1.2.2 Insulation. . :-. 2 1.

3、2.3 Conductor stranding 2 1.1 General . 1 . 1.3 Coaxial pairs. . 2 1.3.1 Conductors . 2 1.3.2 Dielectric insulation 3 2 Methods of jointing symmetrical pairs in communication cables 3 2.1 General . 3 2.1.1 Electrical considerations 5 . 2.2 Manual methods of jointing . 5 2.2.1 Twist jointing - with a

4、nd without soldering 5 . . 2.3 Welding 9 2.3.1 Jointing aluminium conductors by twisting and welding 9 2.4 Connector jointing 9 2.4.1 Methods using ?serrated? metal connectors 9 2.4.3 Methods using ?pin and sleeve? connectors 19 2.4.2 ?Slotted? (metal tag connector i? 12 3 Methods of jointing coaxia

5、l conductors in communication cables . 19 3.1 General 19 I 111 4862593 0b78b93 389 Page 3.2 Methods of jointing inner conductors . 19 3.2.1 General . 19 3.2.2 Soldering methods 21 3.2.3 Crimping methods 21 3.2.4 Method using threaded sleeve 21 3.3 Restoration of inner conductor insulation . 21 3.3.1

6、 Using original insulation . 21 3.3.2 Using alternative insulation . 22 3.3.3 Other methods. 22 3.4 Methods of jointing outer conductors . 22 3.4.1 General . 22 3.4.2 Soldering methods 22 3.4.3 Crimpling methods 23 3.4.4 Mechanical clamping method 23 3.5 Methods of screening the joint . 23 3.5.1 Usi

7、ng original screening tape 23 3.5.2 Other methods . 23 3.6 insulation or sealing of the completed coaxial pair joint 23 3.7 Coaxial pair joints 23 4 Assessment of conductor joint performance 33 4.1 General . 33 4.2 Functional tests 33 4.2.1 Electrical tests . 33 4.2.2 Mechanical tests 34 4.3 Acceler

8、ated aging tests 34 4.3.1 Wire jointing methods and joint degradation mechanisms . 34 4.3.2 Test methods. . 36 ia 4662571 Ob78694 215 9 PREFACE The conductor joints made during construction and operation of telecommunications cables are of great importance in securing high-quality transmission, with

9、 low maintenance. Communication cables vary considerably in their design, depending upon the particular application. In this manual the types of conductor have been divided into those of symmetrical and coaxial pairs. The types of insulation used vary from paper to plastics. Whilst copper is still t

10、he commonly used conductor, aluminium and aluminium alloys have been introduced recently as alternative conductor material, as well as bimetal (e.g. copper- coated aluminium). The electrical performance required of conductor joints has altered with the increasing use of signals requiring a wider fre

11、quency spectrum. Besides manual methods, semi-automatic techniques have been developed which also reduce the labour and the time to complete cable joints. The principles of such methods of conductor jointing have been described to enable assessment of suitability, for particular conditions of use. T

12、he country, or countries, where a particular method is widely used have been indicated in the text. Thus the reader can obtain further information on such matters as electrical performance and reliability from the appropriate administration or operating company. Whilst some of the techniques describ

13、ed can be used for termination of cables (e.g. above ground flexibility, or test access points), this is a special use outside the scope of this manual. Similarly, methods of jointing specialized cables such as submarine cables, and some common antenna or closed circuit television (CATV and CCTV) di

14、stribution cables have also been excluded. The use of trade names has been avoided wherever possible, but references to terms in common use are included. The information in this handbook has been compiled from many sources, and the assistance of the cooperating organizations is gratefully acknowledg

15、ed. III II 4862571 Ob78b75 151 INTRODUCTION This manual describes methods of jointing metallic conductors of telecommunications cables, at present used by various Administrations, private operating agencies and manufacturing companies. Methods of jointing symmetrical and coaxial pair conductors are

16、dealt with separately and an indication is given of the methods of assessing the quality of the joints. When a method of jointing is selected a number of aspects must be considered. Type and design of the conductors i) symmetrical or coaxial pairs, ii) iii) The presence of petroleum jelly or other f

17、illing material in the cable may infiuence the choice. The electrical and mechanical characteristics of the conductor joints This may be influenced by: i) the transmission system requirements, i) Whether a straight joint in a symmetrical pair, or a branched or “tee” joint, is required. The possible

18、advantages of semi-automatic (machine) jointing processes for the larger multipair cables. The need for, or availability of, electrical or other power sources to carry out the jointing work on site. The choice of method and the reliability of the joints may also be influenced by the method of the sh

19、eath restoration (see Reference i) and by the site of the installation, e.g. in an underground structure, or on a pole, etc. conductor material e.g. copper, aluminium, etc., insulation material e.g. paper or plastics. the environment in which the jointed cable is to work, e.g. high humidity, possibl

20、e induced voltages, or mechanical stresses due to cable creepage or other causes. Other factors such as the level of skill, the training required, subsequent maintenance facilities and cost must be assessed by the user for his operating conditions. 1 Designs of communication cable conductors 1.1 Gen

21、eral The design of conductor pairs for communication cables varies widely, within the two main types, .e. symmetrical and coaxial. Apart from differences in materials for the conductor and insulation, there are differences of size and construction resulting from design and manufacturing consideratio

22、ns, which may affect the choice of jointing method. Some of these variations are given in $9 1.2 and 1.3 below. 1.2 Symmetrical pairs 1.2.1 Conductors Annealed copper is often used for the current carrying wire, but aluminium, its alloys and bimetal (e.g. copper-coated aluminium) are also used. 1 8

23、4b25L Ob78696 U38 W 1.2.2 Insulation Paper may be applied to the wire as a wet pulp which is dried to form a continuous uniform covering of paper over the wire, (see a) of Figure 1-1). Alternatively, the paper may be used as a dry tape wrapped spirally (or longitudinally) over the wire (see b) of Fi

24、gure 1-1). Other constructions may be encountered such as a string-paper and string-plastic (see c) of Figure 1-l), balloon-string (see d) of Figure 1-1) and balloon (see e) of Figure 1-1). Plastic insulations are generally uniform continuous coverings extruded over the wire. Polyethylene (PE), poly

25、vinylchloride (PVC), polystyrene and other plastics are used. Use is also made of cllular, or foamed, plastics usually polyethylene. One form has a continuous thin skin over the cellular body of the insulation. These last two designs may be found in cables filled with a petroleum jelly or similar co

26、mpound, but not invariably. CCITT.52370 c) d) FIGURE 1-1 1.2.3 Conductor stranding The basic stranding element from which pair type cables are formed may be one of the following: i) “Pair type” two insulated wires are twisted together symmetrically; i) “Star quad” four insulated wires are twisted to

27、gether symmetrically in close formation; iii) “DM quad” Double pair quad. In this, two symmetrically twisted pairs are themselves twisted together symmetrically. The stranding elements may be made laid up in concentric layers to form the cable core, or, in units or bundles not necessarily having a s

28、pecial symmetry within the unit. 1.3 Coaxial pairs 1.3.1 Conductors 1.3.1.1 Inner conductor A copper or bimetallic wire is used. Other designs use a stranded conductor. The wire strands may be copper, or if of steel, strands of thin copper are laid round the bundle. 1.3.1.2 Outer conductor This is a

29、 continuous metallic tube. The tube may be of copper and may be formed from a tape laid longitudinally with its edges either butt jointed, serrated or overlapped. Alternatively, an aluminium tape of suitable thickness may be welded longitudinally along a seam and then swaged down. Other designs may

30、have helically-laid copper tapes or tinned-copper wires braided or tightly laid in a layer. One or more steel tapes may be applied overall to provide magnetic screening and may also enhance the rigidity. 2 1.3.2 Dielectric insulation 1.3.2.1 Insulation of the inner conductor Polyethylene is commonly

31、 used as the insulation between the inner and outer conductors, although other The most widely used types of insulation are as follows (see Figure 1-2): 1) 2) 3) 4) 5) 6) plastics may be used. uniformly spaced disks with or without tape or peripheral tube (see a) of Figure 1-2); “balloon” type where

32、 a plastic tube is squeezed over the inner conductor at the uniformly spaced points (see b) of Figure 1-2); “worm and tape” type where spirally wound plastic strings over an inner conductor are covered by plastic tape (see c) of Figure 1-2); “bamboo” type, where the disk and tube are moulded in the

33、form of two symmetrical halves welded around the inner conductor (see d) of Figure 1-2); “star” type where the radial elements centre the inner conductor (see e) of Figure 1-2); type with solid or cellular dielectric (see f) of Figure 1-2). 1.3.2.2 Outer conductor insulation This is usually provided

34、 by wrapping two tapes of paper or plastic helically over the coaxial pair, with overlap. 2 Methods of jointing symmetrical pairs in communication cables 2.1 General The various methods of jointing symmetrical pairs are classified according to the method by which the joint is made. This gives four b

35、asic methods; twist jointing, soldering, welding and connector jointing. For jointing small pair size cables, manual methods are often used. These generally require only simple hand tools, and may be relatively lengthy processes. All four methods of pair jointing can be achieved manually. For larger

36、 (high pairage) cables, e.g. main distribution cables near to the exchange (central office), semi-automatic methods may be used. These give high quality joints for a minimum expenditure of time and labour. Generally, semi-automatic jointing methods require the use of connectors. Further points to be

37、 borne in mind when selecting a jointing method are: a) b) Within each of the four basic jointing methods, a variety of different techniques exist. The utility of each depends on the proper balance of properties desired in the final installation. These properties may be grouped as follows: not all m

38、ethods are suitable for use on both aluminium and copper conductors; joints can be constructed as “in-line”, “slack-splice or “single-ended”. 1) installed properties which include: a) b) mechanical ruggedness, and corrosion resistance to ground water and gases, - c) electrical considerations (listed

39、 below); 2) design features which include: a) b) multiple or individual termination, c) d) electrical arrangements, and e) permanency of conductor joint; range of conductor sizes accommodated, packing density in the selected closure system, 3) economic factors which include: a) b) connector cost, c)

40、 tooling required, and d) installation speed. level of network engineering design, 3 4862571 Ob78698 960 W P a) “Disc and tape” type b) “Balloon” type c) “Worm and tape” typ dt II II d) “Bamboo” type t typd 4 I I I Y I e) “Star” type f) Solid or cellular dielectric type 1. Paper tape 2. Outer conduc

41、tor 3. Inner conductor 4. PE tape 5. PE disc 6. Plastic strings (or worms) 7. Steel tape CCITT.52380 FIGURE 1-2 Types of coaxial cables 4 These important points should be borne in mind as each method is explained below. Each method is given in general terms. Examples are given of typical techniques

42、employing that method, together with a brief explanation of different tools required. Note that some processes require external power supplies and others none. 2.1.1 Electrical considerations When jointing symmetrical pair cables consideration should also be given to the possible effect on quality o

43、f signal transmission, e.g. : a) not only is low electrical contact resistance desirable but resistance unbalance should be avoided; b) the dielectric characteristics should be maintained at the joint; c) attention to detail of the joint layout may be necessary to minimize increase in crosstalk. For

44、 low frequency transmissions the first two factors are significant and are normally achieved satisfac- torily with ail jointing methods. With high frequency transmission (analogue or digital) it is important to maintain the symmetry of jointing elements or at least to minimize its degradation. In or

45、der to obtain optimal conditions in France use is made of stranding followed by soldering (see Figure 2-1 and 0 4.2.1.5). This method is used in France and sometimes in other countries. CCIl-r.52390 FIGURE 2-1 2.2 Manual methods of jointing 2.2.1 Twist jointing - with and without soldering Normally,

46、 the conductors to be joined are brought together, and given an initial twist before the insulation is removed. The bared conductors are then twisted tightly together and the surplus cut away. The twisted joint may, or may not, be soldered before being insulated. Unsoldered twisted joints should not

47、 be used with aluminium conductors. Furthermore, unsoldered twisted joints are not recommended for use in low level (dry type) circuits unless a sealing current (20 mA or more) is applied. The twisted joint is insulated by means of paper or plastic sleeves. Typical arrangements using dry unfilled pl

48、astic sleeves are illustrated in Figure 2-2. This method has been used in France and in other countries. 5 0 48b259L 0678700 349 4) $Yeeve 1 5) a) Manual twist operations Insulated conductor I Sleeve is moved FIGURE 2-2 Manual twist and solder method 2.2.1.1 Method of jointing conductors with plasti

49、c insulation using plastic sleeves Jilled with silicone grease or petroleum jelly The main operations are illustrated in a) to d) of Figure 2-3. As described above, the conductors are first brought together and twisted before the insulation is removed; the bare conductors are then twisted together, trimmed to length and soldered if necessary. A plastic sleeve closed at one end and filled with silicone grease is pushed over the twisted joint. The plastic sleeve filled with silicone grease can only be used once. If it is removed for any reason it is then discarded and a new sleeve