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E 3080
Issue 1, 9.11.38


1. General
This Instruction describes the standard arrangements to be adopted in terminating open wires.

2. Definitions

  1. Terminating a line-wire consists in fixing it rigidly to an insulator so as to maintain the tension required. Before tension is taken by the wire at the terminal insulator, the free portion of the wire is passed round the insulator to form a loop, and the "termination" is completed by securing the wire as described in this Instruction.

  2. Single termination is the term indicating the termination of a wire on one side only of an insulator. The term is applied both to terminations at the ends of a wire and to terminations at intermediate points where the wire is made-off once only to an insulator, e.g. at a transposition cross.

  3. Double termination is the term generally used to denote the termination of:-
    i) a single wire in each groove of a double-groove insulator, with a jointless bridging loop (or "bow") - a through  termination, or of
    ii) two wires, one in each groove, on a double-groove insulator and connected by means of a bow formed by joining the tails together.

3. Terminating points
Terminations are essential at:-

  1. terminal points, i.e. leading-in points, terminal and distribution poles;

  2. test points where the circuits are not led into a building or pole test-box;

  3. intermediate poles where an alteration in the position of a circuit is unavoidable (excepting points where such alteration is due to a difference in arm capacity - in which case "transition poles" should be provided - see E 3040).

Line wires should also be terminated at the intermediate points enumerated in paras. 4 and 5. Only in exceptional circumstances should wires be terminated at other points.

4. Terminations at both ends of a span
Line wires should be terminated at both ends of the span at the following points:-

  1. Railway crossings.

  2. Road crossings.

  3. At crossings over power circuits, including the trolley wires of tramway or trolley-vehicle systems.

  4. Where an exceptionally-long span (100yds. or over) is unavoidable. These terminations are required to obviate risk of the wire falling in the crossing span in the event of a break occurring in adjacent spans.

5. Terminations at other intermediate points
Line wires should be terminated at other intermediate points, as follows:-

  1. At transposition poles. (The longitudinal stays, provided at +-mile intervals in accordance with D 3001, should be fitted at transposition poles wherever practicable).

  2. At least every mile in continuous sections of line, where terminations are not required in compliance with para. 4 or 5 (a) (e.g. lines wired on the "twist" system), to limit the effect of breakdowns. These terminating points should coincide with points at which the longitudinal stays, specified in D 3001, are fitted i.e. the terminations should be on longitudinally-stayed poles. If longitudinal stays are not provided in the first instance, the wires should be terminated at poles where facilities for longitudinal staying exist.

  3. At severe angles in the line, except where a pole is double-armed and the wires are carried on straight spindles.

  4. Where the erection of the wires is difficult ; e.g. over rivers or trees, and over or on high buildings.

  5. At the next pole to the terminal (or distribution) pole, where it is required to divide the terminal stress between the first two poles on a line (see C 3301).

  6. At changes of conductor gauge or material.

  7. At junction poles ; i.e. where the wires branch off, either to another pole-line or to a building.

All wires on the line should be terminated at points (a), (b), (c), (d) and (e). Only the wires affected should be terminated at points (f) and (g), and these terminations should be cut out if, and when, the wire is extended by wire of identical gauge and material in the same relative insulator position.

6. Insulators
The circumstances in which the various types of insulator should be used at terminating points are given in paras. 7 to 11.

7. At leading-in points, and at intermediate points where it is necessary to connect the open wire to a lead, "Insulators, No. 16 or 17" should be used.

8. For other single terminations (e.g. where a transposition cross is to be inserted), insulators, of the type specified for through positions of the circuit (see E 3035), should generally be used. Double-groove insulators, with the wire terminated in the lower groove, should be used when long open connexions are required, see para. 45.

9. At test points, "Insulators, No. 14" with "Fuses, Dummy, No. 1" should be used. The appropriate spindle for carrying these insulators on arms bored for spindles and on saddles (single-wire circuits) is Spindle No. 2".

10. At points where double terminations are required, double-groove insulators should invariably be used. Appropriate sizes for various conditions of use are enumerated in E 3035.


With such practice, chafing is liable to occur between the two wires in the insulator groove, eventually resulting in breakage; also, a broken bridge connexion may be masked, at the time of breakage, by the rubbing contact of the two wires in the insulator groove.

11. When it is necessary to run the open wires from a point on a building to a leading-in point below, "Insulators No. 10" (in conjunction with "Insulators No. 21") should be used, the wires between these points being terminated on the insulator side-knobs. With the insulators firmly screwed down, the side-knobs should be positioned so as to provide maximum separation between the vertical drop-wires. With straight spindles, any adjustment necessary can be made by turning the spindles in the bracket; with other spindles, by fitting additional Rings, Insulator, No. 1.


12. The "twisted-sleeve" termination should invariably be used for 40lb. and 70lb. cadmium-copper (or bronze) wires. This consists in the use of a jointing sleeve in forming the terminating loop in the line-wire at the insulator. The position of the sleeve relative to the insulator is such that the loop, when not in tension, can be readily detached from the insulator. The sleeve, when twisted with the wire, becomes virtually a joint and renders the loop practically inextensible.

13. Discontinuance of the "wrapped-bight" termination
The twisted-sleeve superseded the wrapped bight as the standard termination for 40lb. and 70lb. wires in 1916. The wrapped-bight method, which consists in doubling the line-wire back upon itself, taking the bight so formed round the insulator neck and wrapping the end round both the standing part of the wire and the tail, has, nevertheless, continued to be widely practised in some localities, chiefly because it lends itself to hand-tensioning of the wire. It will be seen from E 3064 that hand-tensioning is not permitted. Use of the wrapped-bight termination also constitutes an unauthorized departure from standard practice, and should be discontinued.

14. Sleeves
The sleeves used for terminating are "Sleeves, Jointing, Nos. 14 and 16" and these should be used as follows:-
a) "No. 14" 14in. long, for 40lb. wire and
b) "No. 16" 1in. long, for 70lb. wire.

15. Tools
The tools required for making twisted-sleeve terminations are "Clamps, Jointing, Nos. 1, 1A or 3" described and illustrated in E 3070. The small clamps (No. 3) are most suitable for twisting the sleeves used in terminating 40lb. and 70lb. wires. The detailed instructions given in E 3070 regarding the avoidance of the use of faulty clamps and their removal from service, etc., apply equally to terminating and should be carefully followed.


16. Looping around insulator
The wire which is to form the loop and tail of the termination should be free from abrasions, bends, or other irregularities which would weaken it or prevent its ready passage through the sleeve. It should be sufficiently long to provide a loop of the size required (see para. 17) and, also, a tail for connexion to the tail of the other termination or to the pole-lead, see paras. 24 and 25. To form the loop, the sleeve should be pushed on to the standing part of the line-wire, and the free end of the wire passed round the insulator groove and brought back, through the sleeve, alongside the standing part. The sleeve should then be moved into position, see para. 17; when terminating a regulated section, the free end should be pulled at the same time so that the wire may be as tight as possible between the regulating tool and the insulator.


NOTE:- When grease-packed sleeves are used (see para. 26) the sleeve should be pushed on grease-filled end first, to ensure distribution of the grease throughout the sleeve.

FIG. 1

17. Size of loop
To avoid sharp bends at the sleeve and to ensure that the loop is sufficiently large to allow it to be slipped off the insulator without further bending at the sleeve, the distance between the sleeve and the insulator (see A in Fig. 1) must not be less than the diameter of the insulator at the bottom of the groove, see Fig. 1 (B). Generally, dimension (A) should be equal to (B); when terminating on "Insulators, Nos. 16 and 17" and on the lower groove of No. 14, however, it is desirable for dimension (A) to be made slightly greater than dimension (B) ; this will facilitate the passing of the loop over the upper portion of the insulator, which in these cases is, comparatively, of greater diameter. The distance between sleeve and insulator, in relation to the various insulators, illustrated in E 3035, can be obtained from Table 1.


18. Twisting
The clamps (see para. 15) should be fixed so that their outer sides are flush with the ends of the sleeve. In making the twists, the precautions and instructions relating to the twisting of sleeve joints, detailed in E 3070, and the instructions given in paras. 19 to 22, should be carefully observed.

19. Number of twists
Each sleeve (both with 40lb. and 70lb. wire) should be given 12 twists, see Fig. 2. If fewer twists are made, there is a distinct likelihood of the wire slipping through the sleeve, whilst if more are given the sleeve may be fractured and/or the wire overstrained.

FIG. 2

20. Avoidance of twists in short lengths of wire
Breakages are likely to occur if twists are made in short lengths of wire. The clamp nearer to the point at which the wire is fixed in position should, therefore, be held stationary, the twists being made by rotating the clamp at the other end of the sleeve. Thus:-

  1. when terminating a wire before it is pulled up, the loop may remain on the insulator if the clamp next to the insulator is held still and the other clamp rotated. (The twists imparted to the wire of the span can be taken out by reversing the coil, or by detaching the loop from the insulator after the clamps have been removed).

  2. when terminating after regulating, the clamp nearer the regulating tool should invariably be held stationary, the twists being made from the opposite end of the sleeve, WITH THE LOOP DETACHED FROM THE INSULATOR.

21. To remove the loop from the insulator, first ensure that the sleeve, with the clamps affixed, is in the correct position relative to the wire and the insulator. Then slacken the wire as required between regulating tool and insulator by turning the ratchet drum, and lift off the loop, one side at a time, taking care not to shift the sleeve along the wire. In the case of insulators fitted with covers (Insulators, Nos. 14, 16, 17 and 21), the cover should be off the insulator when the loop is being removed or replaced.

22. When the twists in the sleeve are made from the end nearer the insulator, a cross in the loop results, as shown in Fig. 3. On no account should the loop be twisted to take out the cross ; loops as shown in Fig. 4 are produced when the twists are made from the end of the sleeve remote from the insulator.

FIG. 3

FIG. 4

23. Treatment of free end ("tail")
In replacing the wire on the insulator, the tail, at the sleeve, should be at the side on which it is to be taken to the insulator cavity or joined to the other tail, see para. 43. This will avoid crossing the wire of the span, and chafing can thus be prevented. When forming the connexions, the precautionary instructions given in paras. 42-45 should be closely observed.

24. Connexion to pole-lead
Where connexion to a pole-lead is required, 40lb. tails should be taken direct to the insulator cavity, as shown in Fig. 5. The tails of 70lb. terminations should be shaped as shown in Fig. 6. Jointing should be as detailed in E 3070 and G 3001.

FIG. 5

FIG. 6

25. Connexion to another termination.
Where a tail is to be connected directly to the tail of another termination, they should be brought together midway between the terminations, and jointed in accordance with E 3070. The bows of double terminations should be on a level with the terminations and should be shaped as shown in Fig. 7.

FIG. 7

26. Prevention of corrosion
Grease-packed sleeves. As a protection against corrosion, which is liable to occur when moisture collects in the cavities at the ends of a sleeve, petroleum jelly or other heavy grease is now being inserted in sleeves before issue, The grease, apart from a thin film on the inner walls of the sleeve, is concentrated at one end only ; reliance has, therefore, to be placed on the passage of the wire through the sleeve from the grease-filled end for the sealing of the other end, see para. 16. When the sleeve is twisted, the grease exudes and coats the ends of the sleeve and the adjoining wire; no other treatment is necessary when grease-packed sleeves are used.

27. Use of paint
When the sleeves used for terminating are not grease-packed (see para. 26), the sleeve make-off should be treated with "Paint, Black, for Ironwork". The surfaces of the wire and sleeve at the ends of the latter should be completely coated, the paint being well worked into the cavities. It should be applied when the surfaces are quite dry.


28. Method of terminating
All open wires of 100lb. (or more) per mile should be terminated by looping the wire closely around the insulator and making-off by means of a length of annealed binding wire, referred to in this Instruction as the binder.

29. Avoidance of joints at intermediate terminating points
An advantage of the binding-wire make-off is that, at intermediate points where the line-wire will itself form the connexion between the terminations, the wire can be terminated without destroying its continuity. During erection, therefore, wire should not be cut at intermediate points as a matter of course for the purpose of terminating. Where terminations (single or double) with jointless connexions can be made without inconvenience, line-wire should be paid out and erected without being cut, if otherwise practicable. For a transposition cross, for example, the line-wire should be taken direct from the first single termination to the second, one of the coils being passed under the other as paying-out proceeds.

30. Binder
The binder used for making-off the terminations is as follows:-

  1. Copper and cadmium-copper conductors of 100lb. or heavier per mile ("Wire, Copper, Binding, 50lb.").

  2. Cadmium-copper conductors of 40lb. or 70lb. per mile, 20lb. copper wire, recovered locally from scrap P.C. cables.

  3. Iron conductors, "Wire, Galvd., Binding".

The length of binder required for each type of conductor is given in Tables 2 and 3.

FIG. 8

31. Looping around insulator
A "knee" should be formed in the line-wire in such a position that, with the wire taut and central with the insulator, it fits up to the insulator groove, see A in Fig. 8. To form the knee, the wire should generally be bent inwards, i.e. towards the pole, so that the free portion B may be taken round the insulator from the side nearer the pole, and the bow or tail formed on the opposite side; see, however, para. 43. When the wire has been taken round the insulator groove in the direction indicated, a second knee should be formed, see C in Fig. 8, so that the loop will fit the insulator closely and the free portion D lie alongside the standing part when the binding is being applied. Where the termination is at the end of a section which has just been regulated, the positions of the knees must be carefully determined to ensure that the wire is taut between regulating tool and insulator, so maintaining correct regulation.



32. Making-off
The termination should be made-off in the following manner:-

  1. Form a "knee" in the binder (see A, Fig. 9) at the distance from one of its ends specified in Table 2, and straighten the shorter portion.

  2. With the longer portion towards that side of the insulator on which the bow or tail is to be formed, place the short, straight portion (see B, Fig. 9) under, and central with, the standing part and the free portion of the line-wire, and hold these together near the insulator.

  3. Take the free end of the binder round the insulator, keeping it under the line-wire; see C of Fig. 9.

  4. Pull the binder tight, and pass it around both the free portion and standing part of the line-wire, embracing also the straight portion of the binder. Continue the lapping closely and tightly for the length specified in Table 2.

  5. Bend the free portion of the line-wire D, Figs. 8 and 9, with an easy radius, at right-angles to the standing part, and pull the straight portion of the binder up in the fork thus formed see E, Fig. 9.

  6. Extend the lapping to this point and complete the binding by lapping both ends of the binder side by side around the main wire for five complete turns.

FIG. 9

FIG. 10

FIG. 11

33. Treatment of free end ("tail")
The tails of the terminated wires should be dealt with as laid down in paras. 34 to 36 the precautionary instructions given in paras. 42 to 45 should be carefully followed.

34. Single terminations
Where connexion to a pole-lead is required, the tail should be shaped as shown in Fig. 10 and connected as detailed in E 3070 and G 3001. Where the tail is to be used in forming a connexion to another termination (e.g. at a transposition cross), it should, wherever practicable, be taken direct to the second insulator, see para. 29: jointing a tail is dealt with in para. 37.

35. Double terminations
Except where a change of conductor gauge or material is made at a double termination, the wire should generally be terminated without being cut, see para. 29. The jointless bow is made as follows:-

  1. terminate the wire in the lower groove of the insulator. (It will be realized from Fig. 11 that threading of the remainder of the coil between the termination and the arm is necessary if the upper groove is used first).

  2. Form a knee in the free portion and place this against the insulator, see B in Fig. 11. (The length of wire (X) required in the loop AB is given in Table 2 as a general guide; it is suitable for terminations in straight sections of line, but some variation is necessary at angles).

  3. Take the wire round the insulator, form the second knee (C) and apply the binder, as detailed in para. 32, whipping the termination for the length specified in Table 2, to point (D), Figs. 9 and 11.

  4. Gripping the make-off at this point, turn the termination to its final position, at the same time bending the loop to form an approximately semi-circular bow.

  5. Complete the binding as described in Para. 32.
    Where it is more convenient to make-off the second termination in its final position, form the knees (D) and (B) and the bow before looping the wire round the insulator. (The distance between (D) and (13) can be obtained from the first termination). A completed double termination is illustrated in Fig. 12.

FIG. 12

36. Jointed bows should be made by bringing the tails together on a level with and midway between the terminations, and jointing as described in para. 37. The bows should be approximately semicircular, as shown in Fig. 12.

37. Joints
Where a joint is necessary in a bow or other open connexion between terminations, it should be made as detailed in E 3070. The twisted-sleeve joint (see Fig. 15) is specified for wires up to and including 150lb. per mile, and the Britannia joint (illustrated in Fig. 13), for wires of 200lb. per mile and over. In the case of the former, the tails may be connected as shown in Fig. 14 where it is more convenient to make a "nib" joint than to twist a sleeve fitted in the direction of the wire.

FIG. 13

FIG. 14

38. For the maintenance of correct regulation of line-wires and freedom from faults it is important that the greatest care be taken when terminating, and that the following instructions be carefully observed

39. Terminations to be completed before tension is applied. Tension should not be applied to a termination before the make-off is finished. When erecting wire, therefore, the termination at the beginning of a section should be completed before the wire is pulled up; at the end of the section, tension should be maintained by the regulating tool until the make-off is completed and the wire is in its final position on the insulator.

40. Tightening insulator
Care should be taken to ensure that insulators on which wires are terminated are so tightened that full advantage is obtained from the insulator ring (the rubber washer fitted on the upper shoulder of the spindle, see E 3035). This should be done before the load is taken at the insulator. With the insulator fully screwed down, the completed termination should be rotated slightly on it in a counter-clockwise direction. When the load is taken up, the termination will return to the position of correct alignment. This will cause the insulator to rotate and be firmly bedded on the insulator ring.

41. Position of wire on double-groove insulators. To maintain equality of wire spacing, all the wires terminated on any one side of a pole where double-groove insulators are used, should, where practicable, be made off in the corresponding grooves of the insulators.

42. Open connexions between terminations should be symmetrical and formed so as to provide good clearance from other conductors and from fittings generally, and should be so rigid as to obviate the risk of contact. The tail forming the bow or other connexion should not be bent sharply from the wire of the span at the end of the sleeve or binding-wire make-off, and sharp bends at other points should be avoided. No part of a bow or tail may be left in rubbing contact with another part of the conductor.

43. Position of connexions
Connexions should be arranged so as to be out of the way of workmen, wherever possible. The bow or tail should generally be at the side of the insulator remote from the pole, where it is least liable to damage. For transposition crosses, however, the tail should leave the make-off at the side nearer the other wire of the pair, as shown in Fig. 15.

44. Bows
There should be sufficient wire in a bow to provide for jointing, should it be necessary to cut the bow for testing purposes at a later date; in the case of sleeve terminations (40-lb. and 70-lb. wire), care should be taken not to make larger bows than is necessary for this. To avoid chafing, the tails should not be looped round the insulator when making a jointed bow.

45. Long connexions. Where it is preferable to
connect terminations more than, say, 18in. apart by means of bare wire instead of using cable, double-groove insulators ("Insulators, Nos. 7 or 4") should be fitted and a separate "bridge" wire terminated, by the binding-wire method (see paras. 30 to 32), in the upper grooves. Bows should be formed connecting the bridge wire with the span terminations. Long connexions without this support are insufficiently rigid and are likely to fail at their junction with the wire of the span, where the effect of vibration in them is concentrated. Light-gauge wire should not be used for long connexions wire of not less than 150lb. or 200lb. per mile (depending on length of bridge-wire) should be used.

FIG. 15

46. Disposal of scrap wire
When terminating, care should be taken to comply with the instructions contained in A 0201 for the disposal of scrap wire.


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Last revised: March 30, 2023