CA1192178A - Method of stretching high-tension electric power lines and a device for performing the method - Google Patents
Method of stretching high-tension electric power lines and a device for performing the methodInfo
- Publication number
- CA1192178A CA1192178A CA000406492A CA406492A CA1192178A CA 1192178 A CA1192178 A CA 1192178A CA 000406492 A CA000406492 A CA 000406492A CA 406492 A CA406492 A CA 406492A CA 1192178 A CA1192178 A CA 1192178A
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- Prior art keywords
- cable
- pulley
- haulage
- conductors
- supplementary
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to a system of stretching overhead electric lines, more particularly high-tension lines, according to which a pilot cord or haulage cable is positioned in conventional manner over a set of top pulleys positioned at the highest point on each pylon in the line, and is then used to pull a first haulage cable or guard cable together with at least one other supplementary haulage cable, and/or supplementary guard cable. Each supplementary cable, after pass-ing the top pulleys on which the first haulage cable or guard cable have been laid, is slid and guided downwards until it rests on pulleys underneath. In this manner, each further haulage cable is already positioned for drawing a conductor or bunch of conductors and other haulage cables if required. In the aforementioned system, it is no longer necessary to position a pilot cord for each conductor or bunch of conductors to be tensioned, but it is sufficient to position a single pilot cord on the top pulleys of the pylons, since all the conductors or bundles of conductors and/or further haulage cables are subsequently positioned automatically, starting from the pilot cord or first haulage cable, during the subsequent stage of tensioning.
The invention relates to a system of stretching overhead electric lines, more particularly high-tension lines, according to which a pilot cord or haulage cable is positioned in conventional manner over a set of top pulleys positioned at the highest point on each pylon in the line, and is then used to pull a first haulage cable or guard cable together with at least one other supplementary haulage cable, and/or supplementary guard cable. Each supplementary cable, after pass-ing the top pulleys on which the first haulage cable or guard cable have been laid, is slid and guided downwards until it rests on pulleys underneath. In this manner, each further haulage cable is already positioned for drawing a conductor or bunch of conductors and other haulage cables if required. In the aforementioned system, it is no longer necessary to position a pilot cord for each conductor or bunch of conductors to be tensioned, but it is sufficient to position a single pilot cord on the top pulleys of the pylons, since all the conductors or bundles of conductors and/or further haulage cables are subsequently positioned automatically, starting from the pilot cord or first haulage cable, during the subsequent stage of tensioning.
Description
7l~il "AN I~ROVED ~THOD OF STRETCHING HIGH-TENSION ELECTRIC POIYER LXNES
AND A DEVICE FOR PERFOR~IINC ~E ~IOD"
30*0=0*0_ As is well Imo~Yn to all experts in the construction of electric po~:er lines~ the usual modern method of tensioning electric conductors, either singly or in bundles~ on pylons is ~ie "controlled tension"
method, using "pilot cords" in the initial stage.
In the more convcntional method, the pilot cord is first substan-tially tensioned a~ ground level and then raised and conveyed over the pulleys suspended from the successive pylons in the line and then tensioned.
The actual tensioning operation begins only after the pilo~ cord has been tensioned and i3 consequently suspended b~t~een two pylons along the line. The actual tensioning operation normally comprises the following stages:
The pilot cord is recovered from one end whereas *le other end is coupled to a haulage cable trl~ch, to6ether ~th the pilot cord, is maintained under constant tension and is therefore always raised from the ground, The haulage cable is thus mo~ed forward and progressi-vely takes the place of the pilot cord on the pulleys~
Next, ~he haulage cable is recovered from one end ~herea~ the o~her end is coupled to ~he electric conductor or bundle of conductors uhich~ together ~ith the hæulage cable, are as before Icept ~nder constant tension and raised from the ground. The conductors are thlls moved fo~ard ~nd progressiYely take the place of the haulage cable on
AND A DEVICE FOR PERFOR~IINC ~E ~IOD"
30*0=0*0_ As is well Imo~Yn to all experts in the construction of electric po~:er lines~ the usual modern method of tensioning electric conductors, either singly or in bundles~ on pylons is ~ie "controlled tension"
method, using "pilot cords" in the initial stage.
In the more convcntional method, the pilot cord is first substan-tially tensioned a~ ground level and then raised and conveyed over the pulleys suspended from the successive pylons in the line and then tensioned.
The actual tensioning operation begins only after the pilo~ cord has been tensioned and i3 consequently suspended b~t~een two pylons along the line. The actual tensioning operation normally comprises the following stages:
The pilot cord is recovered from one end whereas *le other end is coupled to a haulage cable trl~ch, to6ether ~th the pilot cord, is maintained under constant tension and is therefore always raised from the ground, The haulage cable is thus mo~ed forward and progressi-vely takes the place of the pilot cord on the pulleys~
Next, ~he haulage cable is recovered from one end ~herea~ the o~her end is coupled to ~he electric conductor or bundle of conductors uhich~ together ~ith the hæulage cable, are as before Icept ~nder constant tension and raised from the ground. The conductors are thlls moved fo~ard ~nd progressiYely take the place of the haulage cable on
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pulleys ~inally, the pulleys conveying the pilot cord, haulage cable and conductors are replaced by kno~m suspension insulators, to hich the conductors are finally and permanently attached.
This method encounters considerable difficulties t/hich may rcadily be understood and are ell-knos~n to those skilled in the art. They relate to the initial tensioning of the pilot cord and to the stretchin~ f the haulage cables and conductors under constant tension.
The invention is n~inly concerr.ed ~ith ~he problems and difficul~
ties of tensioning the pilot cord. ~lthough the tensioning process is relati~ely easy in flat open ground~ it becomes more difficult if the route of the line goes through crops, ~rhich ~ill inevitably be dameged, or ~:oods, in which case it ~ill be necessary to cut dol~n entire lines of trees, particularly those ~ith high trunks. The difficulties ~
be correspondingly greater if the route is still Inore irregular, as is frequently the case in mountaineous regions or ~,here the line crosses other structures SUC}I as streets, rivers, power lines, built-up areas or the lilce~
In an attempt to obviate these difficulties and the associated long periods of ~ork~ it llas been proposed to use helicopters to tension the pilot cords. ,~ helicopter moves alon6 the route of the line above the pylons and gradually un~inds the pilo~ cord, lhich is conveyed by operators on the pylons over pulleys suspended ~therefrom or automati-cally rulls on specially-shaped pulleys.
After the pilot cords have been stretched by the aforementioned method, the haulage cables followed by the conductors and/or bundles of conductors are stretched under constant tension in ~the aforementioned manner.
This method of stretching the pilot cords has the great advantage of reducing damage to vegetation along the route and thus shortening the time required, but is not free from disadvantages.
More particularly, the helicopter pilots have to be par~icularly slcilful, firstly because the helicopter motion is opposed by the pilot cord, hich is at least partly under tension; secondly because ~he
pulleys ~inally, the pulleys conveying the pilot cord, haulage cable and conductors are replaced by kno~m suspension insulators, to hich the conductors are finally and permanently attached.
This method encounters considerable difficulties t/hich may rcadily be understood and are ell-knos~n to those skilled in the art. They relate to the initial tensioning of the pilot cord and to the stretchin~ f the haulage cables and conductors under constant tension.
The invention is n~inly concerr.ed ~ith ~he problems and difficul~
ties of tensioning the pilot cord. ~lthough the tensioning process is relati~ely easy in flat open ground~ it becomes more difficult if the route of the line goes through crops, ~rhich ~ill inevitably be dameged, or ~:oods, in which case it ~ill be necessary to cut dol~n entire lines of trees, particularly those ~ith high trunks. The difficulties ~
be correspondingly greater if the route is still Inore irregular, as is frequently the case in mountaineous regions or ~,here the line crosses other structures SUC}I as streets, rivers, power lines, built-up areas or the lilce~
In an attempt to obviate these difficulties and the associated long periods of ~ork~ it llas been proposed to use helicopters to tension the pilot cords. ,~ helicopter moves alon6 the route of the line above the pylons and gradually un~inds the pilo~ cord, lhich is conveyed by operators on the pylons over pulleys suspended ~therefrom or automati-cally rulls on specially-shaped pulleys.
After the pilot cords have been stretched by the aforementioned method, the haulage cables followed by the conductors and/or bundles of conductors are stretched under constant tension in ~the aforementioned manner.
This method of stretching the pilot cords has the great advantage of reducing damage to vegetation along the route and thus shortening the time required, but is not free from disadvantages.
More particularly, the helicopter pilots have to be par~icularly slcilful, firstly because the helicopter motion is opposed by the pilot cord, hich is at least partly under tension; secondly because ~he
- 3 - ~
pilot cord ~lSt be positioned on the pylons i~ith high accuracy so that the operators c~n secure it or so that it can automatically run on the special pulleys; thirdly, o;.~ing to the neecl for accuracy, the helicopter has to fly at R very low al~itude over ~he pylons or even remain still, ;iith evident difficulty and danger; and last but not leas~, since the most important electric lines normally have six conduc-tors or six bundles of conductors suspended from six braclsets disposed at three different levels separated by several ~etres from one another, the difficulty and risk are multiplied by a factor of six (since one pilot cord has to be positioned for each conductor or bundle of conduc-tors and one for the guard cable), or sometimes by an even higher factor if the helicopter, in order to accompany the pilot cords nearly as far as the lo~est braclcets, has to descend to an altitude at whicll the rotor blades are dangerously near the tip of tlle pylon or actually below it~
Of course, there is also the difficulty of manipulating large quantities of pilot cords and haulage cables. The helicopter and crew have to ork for a long time, resulting in high depreciation and invest-ment cos~s. For these reasons the aforementioned method and expenses are restricted to the most important lines for particularly difficult routes.
The invention, therefore, relates to a method of con~rolled tensioning of an overhead power line which substantially solves the problem of laying the pilot cord.
The system is of the Idnd in which two respective haulage cables are first conveyed over a series of pylons bearing conductors distribu-ted along a given route, and more specifically are conveyed over at least two pu~leys suspended from each pylon at the places ~ihere at least two conductors are attached at various levels, after .~;hich the conduc-tors or bundles of conductors are pulled into position. The system is characterised substantially in that:
- a pilot cord or haulage rope is disposed in conventional manner on the set of pulleys at the highest level;
- the pi]ot cord or 1~aulagc rope ;s recovercd from one end by running it over the sct of hig11-level pulleys, ~:hereas the otl~er cnd is coupled to a primary cable and at least one supplemcntary cahle;
- the primary cable is guided into posi-tion along the groovc of each pulley at the highest level and each supplementar-y c~blc is guided so as to run over the hig1l-level pulleys and then slide slo~;ly do1rn-rards and finally fall on to the lo er-level pulleys; and - cach supplementary pulley ~ositioncd on the lo~er-level pulleys is used directly for dra~ing a conductor or bunch of conductors and simultaneously dra ing another supplementary cable if required.
As can easily be seen9 the system according to the invention greatly reduces and simplifies the preparatory ~iork for tensioning the haulage cables~ The conventional method has to be used only for positioning a single pilot cord or first haulage cable, more particu-larly che cable for pulling ~le guard cable or conductor at the highest level, ~lereas c~ll the other haulage cables, i.eO those underncath, are automatically positioned during the progress of the wor1c of tension-ing thc line. It can also casily be understood that in such cases the use of a helicopter, wl1ich is limited to a single cable disposed at the top of the pylons, becomes much easier and more rapid and is therefore quite cconcmic and justifiable even on lines of secondary importance. This reduces the dama~e to vegctation underneath and the tin1e taken for the work.
Other characteristics and advantages of the systcm according to the invention will be clearer from the following description of some preferred embodiments, glven by way of example only and illustra-ted in the accompanving dra-~ings, in ~hich:
Figso 1 to .~ sho:r a pylon having six brackets distributed at three levels, during four successive stages of the tensioning of a guard cable and t~o other haulage cablesg starting from a first haulage cable;
Figs S ro 7 sho~r the same pylon during four successive operating stages sho~ring the ~ensioning of the haulage cables and b~dles of conductors underneath;
Iig. ~ sho~s the same pylon ith seven braclcets, fitted up in accordance ith a rariant of the system according to the invention;
~ igs. 9 to 11 sho three successive steps in tensioning on a pylon lith ~hree brackets distributed at three different levels in an asymmetrical arran~ement;
Fi~s. 12 to 1~ show three successive steps in tensior~ing on a Y-type pylon;
Fig. 15 diagrammatically sho~s a pulley ~or use in worlcing the ~ethod accordin~ to the inYention, more particularly for tensioning a bundle of three conductors;
Figs. 16a, 16b, 17a and 17b show some constructional details of the top of the pylon in Fig. 1~ and Figs. 18a and 18b are views in pL~n and elevation respectively of a balance-beam device connecting tlle haulage cable to the bundle of conductors~ ~th an attachment for an additional haulage cable, As sho~n, a pulley 2 is mounted in freely rotatable manner at the top of a pylon 1 for a hi~h-tension power line. A pilot cord (not sho~rn) is c~sposed in conventional manner on pulley 2 and on all the other puIleys in the subsequent pylons alo~g the line.
Preferably the pilot cord is laid by a helicopter, ~hich can advantageously be used e~en for secondary lines, o-~in~ tv the sa~.in~
in ~i~e and the reduction of da;nage to tlle crops underneath. The reasons for tlliS ~ider application, hicll have already been set out, are as follo~.s:
- only a sin~le pilot cord has to be laid, and - it is laid at the hiOIlest point of the pylon, ~hus clearly reducing and simpli~ying the ~;orlc of the llelicopterO
The invention, ho~:ever, also i~cludes ~he possibility of using9 not th2 helicopter but ~he conventional ~lethods of manually stretclling the pilot cord, in ~lich case all the advantages of the in~ention ~ri~- likewise b~ obtained, as sho.~n more clearly hereina~ter, e~ccep~
of course for the speed of stre~cllin~ the pilot cord or lirst haulage - 6 ~ 7~
cable, lhich requires the use of a hclicop~er.
The top pilot cord is then recovered from one end by running it over the pulleys, ~hereas the other end is at~ached to a first haulage cable hich, according to the conventional rnethod as before, progressively talces thc place of the pilot cord on the pulleys.
This may be regardcd as the end of the preparatory stage before stretching all the other haulage cables for the other conductors of the linc. The preparatory stage may be further greatly simplified at leas~ in certain cases, ~y initial direct manual stretching of the first haulage cable.
Fig~ 1 sho~:s the nect stage, the beginning of the recovery of the pilot cord and haulage rope T and the drawing of the guard cable G. The end T~ of cable T is pulled, e.g. by a ~nch, ullereas the oppo-site end T~ is secured to a balance-beam connecting device 3, the shape of hich is more clearly shown in Fig. 1~.
Device 3 is secured - at leas~ in the initial stage and in the case of a line of pylons as in Fig. 1 to the guard cable G to be stretched, ~hich is secured centrally on member 3, or to t~o additional haulage cables T1 and T2 secured at the sides, for the purpose described hereinafter.
As sho~.~n in Fig. 1~, member 3 comprises a main attachment plate 3a, one sidc of hich is centrally secured to a chain 3b, all the lin!cs of ~lich have a horizontal ~YiS. The free end of chain 3b is secured to the first haulage cable T by a freely rotating attachment 3c~
On the other side of plate 3a thre are three attachments 3d, 3e and 3f, preferably also rotatable, for securing the guard cable G and haulage cable Tl and T2.
Another rotatable attachment 3g is secured to chain 3b and connected to a cable T3 ~hich is deflected to the e~xterior of plate 3a by strirrups 3h/ the function of t~hich l~ill be more clearly e.Yplained hereinafter~
~ lember 3 also comprises a counter-weight 3i secured belo~ plate 3a near the central at~achment 3d and comprising a chain having i7~
hori~ontal linlcs.
During the recovery of cable T, counter-weight 3i holds plate 3a subst~ntially horizontally, aided by the fact that the freely rotatable attachments 3c to 3f absorb any torsional stresses applied to the cables, ~len member 3 moves over pulley 2, cables 3b and 3i hold member 3 in the central position since, o~ing to the horizo~tal linlcs, cables 3b and 3i fit into the arcuate groove of the pulley, ~ s a result, the guard cable G is directly and safely guided over pulley 2, wllereas cables T1 and T2 are pulled to the outside and slide over the sides of pulley 2 downh~ards. Fig. 16a shows the moment when member 3 is mo~ing over pulley 2 and the guard cable is centred on the pulley vhereas cables T1 and T2 are at the sides thereof, As shown in Fig. 2, in proportion as member 3 moves a~ay from pylon 1 ~the two cables Tl and T2 move downwards over the sides of the top of the pylon. To facilitate this descent and dot.,~nward motion and to protect the pylon structure, rods 5 having a pointed tip are secured to the sides of the holder ~l of pulley 2, as sho~m in Figs.
16a and 16b. ~ach rod 5 extends dol,nwards in a tubular guide 6 ~hich, oling to its round cross-section, facilitates the motion of cables T1 and T2 downwards and in tlle direction in ~hich the cables are pulled, In an alternative entbodin~ent, guide 6 can be a roller freely rotatable around its longitudinal axis relative to rod 5 and to another holder (not sho~n) at ~he opposite end.
As Fig. 2 shot:s, guides 6 1ihich, as stated, comprise bars or rollers, ~c-tend downt~ards to near the base o~ the tip of pylon 1, where they are connected to o~her guides 7 ~hich lilcewise are inclined dol~wards but ~ith a gentler slope and extend to above braclcet~s i3 and 9 of pylon 1, As shown in greater detail in Figs, 17, guides 7 also comprise tubular elements, more preferably rollers freely rotatable around their respective longitudinal axis and te~nina~ing in a ro~d, bevelled rod 7' projecting slightly beyond the end 3~ or 9~ of braclcet 3 or 9~
In an alternative embodiment (not shol;n) 6uides 6 and 7 can be replaced l~ a single straight or curvcd guide extending from the top rod 5 to the rod 7~ at the end of tlle braclcet.
According ~o yet another variant, the single guide can comprise a steel cable stretched bet~een the topmost part of the pylon and the ends 3~ or 9' of the brackets.
The downward motion of cables Tl and T2 is not instantaneous, even if the inclination of guides 6 and 7 is very steep, but progressi-ve, in proportion as member 3 moves away from pylon 1. The reason is that, as long as member 3 is near the pylon, the ~eight of the ha~lage cables~ ~hich controls ~le do~nward motion~ is offset by the pull on the cables ~owards member 3, i.e. towards the central axis of the line.
llhen member 3 moves a~ay, therefore~ cables Tl and T2 progressive-ly move dotmwards until ~ley meet the end rods 7~. This is the position sho~n in Fig. 3. At this stage the haulage cables fall abruptly do:n.
Note that ~le fall is not absolutely vertical but inclined tol~ards the a~is of pylon 1~ This is because each cable is subjected to t~:o opposing forces - on the one hand the resistance of the cable itsel~
and the associated conductor, ~hich acts substantially parallel to the line~ and on the other hand the tension whicll, o~ing to the re-lative nearness of men~ber 3 to the pylon, is exerted towards ~he central axis of the line.
A guide arm or bollard 10 is disposed belo~ the end of the bracket and has a tip 10~ projecting beyond rod 7~. When cable T falls, it is collected by arm 10~ which is inclined towards the interior and thus guides it towards pulley 11 suspended from ~he bracket.
Pulley 11 has an "open" shape, e.g. as illustrated in Fig. 15.
As Fig~ 15 sho~is, the pulley frame 11a has a substantially C- or G-shape, i.eD a rectangular s~ructure open at the top of one side. One or more ~heels or sheaves are rotakably mounted on the ~rame in order ~o convey a conductor or bundle of conductors. In the illustration 9 ~9~
there are three sheaves 15, 16 and 17, The centrc~l sheave 16 initially conveys the haulage cable, fol-lowed by the transmission member 3, each sheave conveying one conductor from the bundle, As sho~n in the diagram, arm 10 is shaped so that one end thereof lOa, thich prolongs its top edge, terminates at the bottom, under operatin6 conditions, level l.ith the edge of the central sheave 16 as sho:~n. Consequently s~hen the haulage cable~ ~ihich has fallen from the top braclcet, slides along arm 10, it can fit sideways into the frame of pulley 11 and be directly positioned in the groove of the central sheave 16. A stop ann 18 prevents the cable from sliding beyond sheave 16 to~ards sheave 15.
Fig, .~ shows the final or arrival position of the haulage cable ~hen it is properly positioned and centred on the pulley 11 of the top braclcet in the pylon.
The ne~ct stage of operation is sho~n in Fi6. S, ~hich sho~ s that the end T~t of the cable is coupled to a balance-rod mel~ber 3 ~/hich is coupled to the follo~ing:
- in ~le central position member 3 is coupled by attachment 3d to a service cord S, the other end of hich i5 connected to a conven-tional transmission member 12 for a bundle of three conductors C.
- in the lateral position, ~nellber 3 is coupled to another haulage cable T3, ~liCh iS secured to the attacll~ent 3g of nember 3 shol~n in Fig. lBa and is guided over the ends of stirrups 3h.
Before member 3 reaches the pulley, arm 10 is tilted do\~mrards, e.g. into the position ~lo~m in Fig. 6~
When member 3 reaches the pulley, cord S talces the place of the haulage cable T2 on the central sheave 16, At the s~ne time, cable T3 is dra~n beyol~d the outermost sheave of pulley 11 and, ol~ng to the absence of arm 10 which l~s been ~ilted do~mwards, runs along the side 11b and falls freely do~wards.
As shown in Fig, 6, during ~the pulling of the bundle of conductors C, each positionea on a sheave 15, 16, 17 of pulley ll~ the cable - 10~
T3 is fallinc to ards the b~aclcet 9a underneath and bears on a guide 7. Guide 7 is secured to bracket 9a in a ;namler completely similar to the guide 7 associated with the top braclcets ~,9. ~lternatively, guide 7 can be mounted so as to slide bet~een the end of the braclcet underneath and the base of the pulley, as sho~n by a chain-dotted line in ~ig. 6, in ~hich case guide 7 can also stabilize the pulley.
In both cases, the cable falls and abuts the guide underneath o~ing to the fact that the bracket projects e~ternally beyond the vertical axis of the pulley ll underneath.
Fig. 6) acordingly, shows ~he bundle of three conductors C, which no~ rest in the pulley 1l of the uppermost bracket, after the transmission member 12 and l~ulage cable T3 have passed over pulley 11 in three successive positions as follows:
- in posision I, indicated by chain lines, ~hich pulley 11 talces up immediately after the highest pulley 11 has moved along guide 7;
- in position II, indicated by cha~n lines, hich the pulley ta-kes up after sliding along guide 7 and falling belos~ rod 11', i.e.
against arm lOa, and - in position III, indicated by a continuous line, hich pulley 11 talces up ~fter sl;ding along a~ll 10a and entering pulley lla.
During the pulling of the bunch of conductors C over the high-est pulley 11, cable T3 is also pulled over the pulley 11a underneath.
At the moment ~hen member 3 reaches the pulling sta~ion, the bundle of conductors C and cable T3 have been completely extended. At this point, puIling begins on cable T3, which is associated :ith another balance-beam member and another bundle of conductors. ~ig~ 6 shows member 3 arriving near pulley lla and anchored to the haulage pulley, ~:hicn is coupled to a service member S for pull;ng a ~rans~ission mem~er 12 (not shot~n) for another ~ndle of conductor~ and another haulage cable T3l secured to attacl~nent 3g~
Finallyg Fig. 7 shows the stage ~:hen the b~tdle of conductors C ha~e been completely drawn over the highest pulley 11 and ~he bunch of conductors Ct, member 3 and transnission metnber 12 are begiL~ing 7~
to pass over the pulley lla underneath, having just passed the previous pulley. At the moment when member 3 passes pulley lla, cable T3' slides and falls and takes up position on the lowest pulley llb. As before, the fall is shown in various stages, i.e.:
- position I in which cable T3l after sliding from pulley lla, has fallen and abuts the guide 7 of the lowest bracket, and - position II, in which the cable rests on the lowest pulley llb.
Cable T3' is adapted next to draw a bundle of con-ductors like the preceding ones, but of course it is not necessary to draw other haulage cables at the same time.
All the stages described hereinbefore with reference to FigsO 4 to 7, which show the positioning and pulling of the haulage cables and conductors on the right side of the pylon relatively to the drawing, are exactly similar for the left side, either subsequently or simultaneously depending on the chosen operating conditions.
During the aforementioned stages reference has always been made to the motion of a balance-beam member 3, directly drawn by the haulage cable. The last-mentioned cable is pulled while cord S pulls transmission membex 12 and the bundle of conductors. This method is appropriate when it is desired ~o prevent a haulage cable travelling side by side with the conductors; in such cases cord S will be longer or at least equal in length to the length of cable between two pylons, so that the additional haulage cable is moved 9 and consequently moved away from cord 5~ opposite a given pylon along the line, before txansmission member 12 has passed the preceding pylon.
Alternatively, if the preceding requirements does not apply, member 3 can be connected to the haulage cable and also directly connected to the bunch of conductors (via the rotary attachments 3d, 3e and 3f) and to the additional haulage cable (via attachment 3g), thus avoiding the use of transmi 5 S ion member 12.
Fig. 8 shows a different embodiment in which single conductors are stretched on a pylon of the same kind as shown in the preceding drawings.
In ~ig. 8, the pylon is fitted with rods 20 and cables extending between each pulley 22 and the end of the bracket underneath it. Each pulley 22 is associated with a bollard or arm 12 which can take either a closed position (as shown on the left side of the pylon relative to the drawing) in which case motion will occur between pulley 22 and the end of the supporting bracket, or an open position tshown at the right of the pylon) when the cable or conductor will be guided inside the pulley.
The system shown in Fig. 8 can be used for stretching in various ways, some of which will be shown hereinafter. All of them star-t from an initial preliminary stage in which a pilot cord or haulage cable is positioned on the top pulleys 2 by the conventional method, by hand or by a helicopter.
A) - The first haulage cable is used to draw three additional haulage cables as already shown in the case of cables Tl, T2 and G during the first stage of the process illustrated in Fig. 1. The central additional haulage cable remains on pulley 2, whereas the side haulage cables are pulled and slide along the top and the first brackets, arms 21 and 21' of the top pulleys 22 and 22' being closed, so that the cables travel over pulleys 22, descend along the first rods 20, travel over the second pulleys 22', descend along the lower ~2~
rods 20, and finally fall beyond the lowest bracket on to the arm 21" underneath and into pulley 22". During the motion of the cable, the bottom arms 21' open, whereas arms 21 remain closed. The cable remains on pulleys 2 and the pull begins on three other haulage cables. In the same manner as shown previously, the central cable remains on pulleys 2 whereas the two side cables are run and slid down-wards. They travel over the top pulleys 22, down the top rods 20 and, after travelling over the tip of the interme-diate bracket, enter arm 21', which is now open, and areguided into the intermediat~ pulleys 22" . During this second motion of the cables, the top arms 21' also open and, while the cable remains on pulleys 2, the pu11 begins on the guard cable and two further haulage cables. The guard cable remains positioned on pulleys 2, in order subsequentary to be secured at the top of the pylon, whereas the two supplementary cables are moved and slide along the top brackets on to the open arms 21 and are guided into the top brackets 22. When the haulage cables are positioned in each bracket, the con-ductors are tensioned in the usual manner.
Of course, instead of pulling six complete haulagecables in the aescribed manner, service cords can be used for the drawing operations and directly coupled to the conductors.
s) - As an alternative to A), five haulage cables instead of three can be drawn during the first operation. The central cable is positioned on pulleys 2 whereas the other cables are conveyed, two on the left and two on the right of the pylon, and are guided in the previously-described manner over the intermediate pulleys 22' and bottom pulleys 22" , arm 21' being opened immediately after the first of ea~h pair of cables travels over it. Next, the cable which has remained on pulleys 2 is used to pull the guard cable and the two cables to be positioned on the top pulleys 22. Preferably the first five haulage cables are drawn by two balance-beam members in succession. a first balance member drawing two haulage cables and a central service cord of reduced length, and a second balance member coupled to the service cord and pulling the other three haulage cables. This facilitates the drawing process and prevents two cables from sliding together over the same bracket and twisting.
C) - If a sufficiently powerful which is available, another alternative consists in drawing six haulage cables and the guard cable simultaneously; the central guard cable is positioned on pulleys 2 whereas the haulage cables are drawn three to the right and three to the left of the pylon. In order properly to position the cables on pulleys ~2, 22' and 22" , the top arm 21 is opened immediately after two of the cables have run over it, whereas arm 21' is open~d immediately after one cable has run over it.
In this case also it is preferable to use three balance members in rapid succession one after the other, as already explained in alternative b).
D) - Alternative methods can be used, as chosen by the skilled in the art, for simultaneously pulling five haulage cables and conductors. These other methods, if any, will of course be decided upon in accordance with the operating conditions and the available means, without modifying the essential features of the inventionO
The aforementioned methods of tensioning single conductors can of course also be used for tensioning bundles of conductors. More particularly~ instead of proceeding in the method indicated in Figs. 1 to 7, all six haulaye cables can be positioned first, e.g. by one of the methods A) to D) hereinbefore, after which each haulage cable can be used ~9;~:~71~
to tension a respective bundle of conductors in conventional manner in the preferred sequences.
Figs. 9 to 11 show the sequence of operations according to the invention for tensioning on an asymmetrical pylon having three brackets.
As shown in Fig. 9, a pilot cord is positioned in conventional manner, i.e. manually or by helicopter, on the top pulleys 2 and is replaced by a first cable T, which is used to pull the guard rope G and three additional haulage cables Tl/ T2 and T3. The pull is applied via an asymmetrical balance member 25 diagrammatically shown in Fig. ~.
FigO lO shows the balance member 25 when it has just passed the top pulley 2. The guard cable G is thus positioned in the groove o pulley 2 in the previously-described manner. The three haulage cables are drawn one on one side and two on the other si~e of pylon 1.
Cable Tl, which is drawn to the left of the pylon~
descends along guides 6 and 7 until it reaches the end of the left bracket, from which it falls, guided by arm 27, into pulley 26.
Cables T2 and T3 descend along guides 6, 7 borne by the top right bracket to the end thereof, where a pulley 26' is secured with a closed arm 21 and a rod 20 completely similar to that illustrated in Fig. 8 is secured between pulley 26l and the bracket underneath. As soon as cable T3 has moved over the top bracket and arm 21 and pulley 26', arm 21 opens. Thus~ whereas cable T3 slides down along rod 20 to fall on to the open arm 21' and be guided into pulley 26" , cable T2 falls into arm 21, which is now open, and is guided into pulley 26l~.
Fig. 11 shows the final position in which cables Tl, T2 and T3 have been finally positioned in the respective pulleys 26, ~6' and 26" and are ready to pull singl~
conductors or bunches of conductors as required.
Of course, as already stated, instead of stretching haulage cables over the entire length of the line and then using them to stretch the conductors, the balance member 25 can be attach~d to service cables which are directly attached to conductors or bundles of conductors, the service cables performing the function of moving until they rest in the pulleys underneath.
As alread~ stated it may be preferable, instead of attaching all three cables and the guard cable to the same balance member 25, to use a first balance member attached to cables T1 and T2 and a short central cable, which is attached to a second balance member for drawing the guard cable G and cable T2.
Figs. 12 and 14 show the sequence of operations according to the invention for drawing over a Y-type pylon.
As is known, in a pylon of this kind the conductors are suspended from insulators Jl, J2, J3 borne by two side brackets 30, 31 and a central cross-member 32. The pylon also h.as two small tips 33, 34 each bearing a guard cable.
According to the invention, an additional central tip 35 is positioned on the aforementioned known pylon and used exclusively for the system of tensioning according to the invention, and is therefore preferably dismantle~ after the tensioning operation has been completed.
Apex 3S bears the previously-described top pulleys 2 and is also secured to guides 6, which preferably run from pulley 2 to the.top of apices 33 and 34, and guides 7, which run from apices 33, 34 to the outer ends of bracke~s 30, 31 respectively n Tensioning is performed as follows:
'7~3 - 16a -- the first haulage cable is positioned on pulley 2 in the conventional manner as pxeviously mentioned and is used to pull a balance member 36 secured to two guard cables Gl, G2 and three haulage cables Tl, T2 and T3.
Fig. 12 shows member 36 approaching pylon 1. Fig.
12 also shows how, according to an important feature of the invention, the central cable T3 is not pulled directly by member 36 but by a pair of service cables S1, S2 connected by joints which can easily be dismantled, and the purpose of which will be described in detail hereinafter.
One service cable - cable Sl in the present case -is under tension, whereas the other is slack. Consequently, when member 36 travels over the pulley, only cable Sl remains on it, whereas (Fig. 13) guard cable Gl and haulage cable Tl are slid towards the centre of the pylon, guard cable G2 and haulage cable T2 are slid towards the right of the pylon (relati~e to the drawing in al' cases), whereas cable S2 can be slid either rom the right or the left of pulley 20 As soon as member 36 has passed pulley 2, the pull is temporarily stopped. An operator disconnects the slack cable S2 and conveys it below cross-member 32 and then re-secures it. The operator also, using special equipment, tensions cable S2 and consequently relaxes Sl. Fig. 13 shows this exact moment, when cable S2 has just been re-attached and tensioned. Immediately afterwards, the operator releases cable Sl, now slack, and conveys it under member 32 and re-attaches it, at which point the pull can recommence.
As Fig. 13 also shows, cables Tl and T2 have been slid along guides 6 and after opening two small arms ~not shown) at the top of apices 33, 34) bear against guides 7 above brackets 30 and 31; guard cables G1 and G2 have been slid along guides 6 and, since the arms are open, have taken - 16b -up position on pulleys (not shown) at the top of apices 33 and 34, Finally Fi.g. 14 shows how, when member 36 moves further away from the pylon, haulage cables l'l and T2 slide along guides 7 and fall from brackets 30~ 31 and are guided ln the previously-described m~tner o~er arms (not sho n) under the ends of the braclcets, ~hich gttide them ~tto cornespondin~ pulleys (also not shotn). Fi6. 1~ sho~:s this final configuration, in hich haula~e cables T1, T2 are disposed in pullcys suspended frolt insulators J1 and J2, the ccntral haulage cable T3 is disposed in a pulley suspended from insulator J3 and the ~uard cablcs G1, G2 nre disposed in pulleys (lilce the precedin~, not sho n) at ~te top of apices 33 and 340 As Fig. 14 also sho:.~s, the central apex 35 llas been di~nantled, since it is no longer necessa-ry.
In ~lis ¢ase also, instead oP attaching the three haulage ca-bles and the two guard cables to a single balance mem~er 36, it may be preferable to use a first balance member to pull the t~o outer cables T1 and T2 and a central cable, which is attached to a second balance ntember for pullin~ the t~o guard cables and the central hau-lage cable T3.
~ Iroughout the description, reference has been made to the ini-tial positioning of a pilot cord by con~cntional methods, i.e. by hand or by helicopter, and used firstly to pull a haula~e rope. This ~anner of c~pression is based on the usual technique, in hich the pilot cord is a liglt cable of syntlletic material such ~s mJlon~
-hich l~akes it ~asier ~o posi~ion, ~ereas ~he haulage cable is nor-mally of steel and relati~ely heavy, and more particularly capable of ithstanding considerable ~tension and not accumulating torques.
Of course it is possible, and is actually practiced, for the cable initially positioned on the top pulleys to be capable of directly pulling the conductors.
~ lore particularly in the last case, but of course also in the morc general case :here a pilot cord is used ~ollowed by ~ 1~ulage cable, ~he balance members used for pulling lill first be secured to the service cables, uhic'n will be ad2pted for sliding and moving from the top pulleys to the bottom pulleys, to which the conductors or bundles of conduc~ors or haulage cables ~ill subsequently be at-tached~
~9Z~7~
The cld~ nta6es of the method according to the invention are con-siderable. In addition to ~le previously-mentioned main advanta~es of rapid performance, particularly on difficult or irreg~ualr routes, and of protecting khe vegetation underneath, there is also a consi-derable reduction in the need for pilot cord, the power lines remain out of operation for only a short ~ime, and owing to its lo~r expen-se, as previously mentioned, the method of controlled tensionin~ can be extended to less important lines, e.~ 150 IcV. Other advanta~es can easily be seen by the sldlled in the art.
~ lowever, the invention is not limited to the particular embodiments or procedures described, or to the only specific use which has been disclosed, but can have many variants, including uses, e.~. for stret-ching relpher cables or ~he like~ hic}l are all within reach of a technician slcilled in the art, and therefore are all falling Irithin the protec-tion scope of the present invention.
pilot cord ~lSt be positioned on the pylons i~ith high accuracy so that the operators c~n secure it or so that it can automatically run on the special pulleys; thirdly, o;.~ing to the neecl for accuracy, the helicopter has to fly at R very low al~itude over ~he pylons or even remain still, ;iith evident difficulty and danger; and last but not leas~, since the most important electric lines normally have six conduc-tors or six bundles of conductors suspended from six braclsets disposed at three different levels separated by several ~etres from one another, the difficulty and risk are multiplied by a factor of six (since one pilot cord has to be positioned for each conductor or bundle of conduc-tors and one for the guard cable), or sometimes by an even higher factor if the helicopter, in order to accompany the pilot cords nearly as far as the lo~est braclcets, has to descend to an altitude at whicll the rotor blades are dangerously near the tip of tlle pylon or actually below it~
Of course, there is also the difficulty of manipulating large quantities of pilot cords and haulage cables. The helicopter and crew have to ork for a long time, resulting in high depreciation and invest-ment cos~s. For these reasons the aforementioned method and expenses are restricted to the most important lines for particularly difficult routes.
The invention, therefore, relates to a method of con~rolled tensioning of an overhead power line which substantially solves the problem of laying the pilot cord.
The system is of the Idnd in which two respective haulage cables are first conveyed over a series of pylons bearing conductors distribu-ted along a given route, and more specifically are conveyed over at least two pu~leys suspended from each pylon at the places ~ihere at least two conductors are attached at various levels, after .~;hich the conduc-tors or bundles of conductors are pulled into position. The system is characterised substantially in that:
- a pilot cord or haulage rope is disposed in conventional manner on the set of pulleys at the highest level;
- the pi]ot cord or 1~aulagc rope ;s recovercd from one end by running it over the sct of hig11-level pulleys, ~:hereas the otl~er cnd is coupled to a primary cable and at least one supplemcntary cahle;
- the primary cable is guided into posi-tion along the groovc of each pulley at the highest level and each supplementar-y c~blc is guided so as to run over the hig1l-level pulleys and then slide slo~;ly do1rn-rards and finally fall on to the lo er-level pulleys; and - cach supplementary pulley ~ositioncd on the lo~er-level pulleys is used directly for dra~ing a conductor or bunch of conductors and simultaneously dra ing another supplementary cable if required.
As can easily be seen9 the system according to the invention greatly reduces and simplifies the preparatory ~iork for tensioning the haulage cables~ The conventional method has to be used only for positioning a single pilot cord or first haulage cable, more particu-larly che cable for pulling ~le guard cable or conductor at the highest level, ~lereas c~ll the other haulage cables, i.eO those underncath, are automatically positioned during the progress of the wor1c of tension-ing thc line. It can also casily be understood that in such cases the use of a helicopter, wl1ich is limited to a single cable disposed at the top of the pylons, becomes much easier and more rapid and is therefore quite cconcmic and justifiable even on lines of secondary importance. This reduces the dama~e to vegctation underneath and the tin1e taken for the work.
Other characteristics and advantages of the systcm according to the invention will be clearer from the following description of some preferred embodiments, glven by way of example only and illustra-ted in the accompanving dra-~ings, in ~hich:
Figso 1 to .~ sho:r a pylon having six brackets distributed at three levels, during four successive stages of the tensioning of a guard cable and t~o other haulage cablesg starting from a first haulage cable;
Figs S ro 7 sho~r the same pylon during four successive operating stages sho~ring the ~ensioning of the haulage cables and b~dles of conductors underneath;
Iig. ~ sho~s the same pylon ith seven braclcets, fitted up in accordance ith a rariant of the system according to the invention;
~ igs. 9 to 11 sho three successive steps in tensioning on a pylon lith ~hree brackets distributed at three different levels in an asymmetrical arran~ement;
Fi~s. 12 to 1~ show three successive steps in tensior~ing on a Y-type pylon;
Fig. 15 diagrammatically sho~s a pulley ~or use in worlcing the ~ethod accordin~ to the inYention, more particularly for tensioning a bundle of three conductors;
Figs. 16a, 16b, 17a and 17b show some constructional details of the top of the pylon in Fig. 1~ and Figs. 18a and 18b are views in pL~n and elevation respectively of a balance-beam device connecting tlle haulage cable to the bundle of conductors~ ~th an attachment for an additional haulage cable, As sho~n, a pulley 2 is mounted in freely rotatable manner at the top of a pylon 1 for a hi~h-tension power line. A pilot cord (not sho~rn) is c~sposed in conventional manner on pulley 2 and on all the other puIleys in the subsequent pylons alo~g the line.
Preferably the pilot cord is laid by a helicopter, ~hich can advantageously be used e~en for secondary lines, o-~in~ tv the sa~.in~
in ~i~e and the reduction of da;nage to tlle crops underneath. The reasons for tlliS ~ider application, hicll have already been set out, are as follo~.s:
- only a sin~le pilot cord has to be laid, and - it is laid at the hiOIlest point of the pylon, ~hus clearly reducing and simpli~ying the ~;orlc of the llelicopterO
The invention, ho~:ever, also i~cludes ~he possibility of using9 not th2 helicopter but ~he conventional ~lethods of manually stretclling the pilot cord, in ~lich case all the advantages of the in~ention ~ri~- likewise b~ obtained, as sho.~n more clearly hereina~ter, e~ccep~
of course for the speed of stre~cllin~ the pilot cord or lirst haulage - 6 ~ 7~
cable, lhich requires the use of a hclicop~er.
The top pilot cord is then recovered from one end by running it over the pulleys, ~hereas the other end is at~ached to a first haulage cable hich, according to the conventional rnethod as before, progressively talces thc place of the pilot cord on the pulleys.
This may be regardcd as the end of the preparatory stage before stretching all the other haulage cables for the other conductors of the linc. The preparatory stage may be further greatly simplified at leas~ in certain cases, ~y initial direct manual stretching of the first haulage cable.
Fig~ 1 sho~:s the nect stage, the beginning of the recovery of the pilot cord and haulage rope T and the drawing of the guard cable G. The end T~ of cable T is pulled, e.g. by a ~nch, ullereas the oppo-site end T~ is secured to a balance-beam connecting device 3, the shape of hich is more clearly shown in Fig. 1~.
Device 3 is secured - at leas~ in the initial stage and in the case of a line of pylons as in Fig. 1 to the guard cable G to be stretched, ~hich is secured centrally on member 3, or to t~o additional haulage cables T1 and T2 secured at the sides, for the purpose described hereinafter.
As sho~.~n in Fig. 1~, member 3 comprises a main attachment plate 3a, one sidc of hich is centrally secured to a chain 3b, all the lin!cs of ~lich have a horizontal ~YiS. The free end of chain 3b is secured to the first haulage cable T by a freely rotating attachment 3c~
On the other side of plate 3a thre are three attachments 3d, 3e and 3f, preferably also rotatable, for securing the guard cable G and haulage cable Tl and T2.
Another rotatable attachment 3g is secured to chain 3b and connected to a cable T3 ~hich is deflected to the e~xterior of plate 3a by strirrups 3h/ the function of t~hich l~ill be more clearly e.Yplained hereinafter~
~ lember 3 also comprises a counter-weight 3i secured belo~ plate 3a near the central at~achment 3d and comprising a chain having i7~
hori~ontal linlcs.
During the recovery of cable T, counter-weight 3i holds plate 3a subst~ntially horizontally, aided by the fact that the freely rotatable attachments 3c to 3f absorb any torsional stresses applied to the cables, ~len member 3 moves over pulley 2, cables 3b and 3i hold member 3 in the central position since, o~ing to the horizo~tal linlcs, cables 3b and 3i fit into the arcuate groove of the pulley, ~ s a result, the guard cable G is directly and safely guided over pulley 2, wllereas cables T1 and T2 are pulled to the outside and slide over the sides of pulley 2 downh~ards. Fig. 16a shows the moment when member 3 is mo~ing over pulley 2 and the guard cable is centred on the pulley vhereas cables T1 and T2 are at the sides thereof, As shown in Fig. 2, in proportion as member 3 moves a~ay from pylon 1 ~the two cables Tl and T2 move downwards over the sides of the top of the pylon. To facilitate this descent and dot.,~nward motion and to protect the pylon structure, rods 5 having a pointed tip are secured to the sides of the holder ~l of pulley 2, as sho~m in Figs.
16a and 16b. ~ach rod 5 extends dol,nwards in a tubular guide 6 ~hich, oling to its round cross-section, facilitates the motion of cables T1 and T2 downwards and in tlle direction in ~hich the cables are pulled, In an alternative entbodin~ent, guide 6 can be a roller freely rotatable around its longitudinal axis relative to rod 5 and to another holder (not sho~n) at ~he opposite end.
As Fig. 2 shot:s, guides 6 1ihich, as stated, comprise bars or rollers, ~c-tend downt~ards to near the base o~ the tip of pylon 1, where they are connected to o~her guides 7 ~hich lilcewise are inclined dol~wards but ~ith a gentler slope and extend to above braclcet~s i3 and 9 of pylon 1, As shown in greater detail in Figs, 17, guides 7 also comprise tubular elements, more preferably rollers freely rotatable around their respective longitudinal axis and te~nina~ing in a ro~d, bevelled rod 7' projecting slightly beyond the end 3~ or 9~ of braclcet 3 or 9~
In an alternative embodiment (not shol;n) 6uides 6 and 7 can be replaced l~ a single straight or curvcd guide extending from the top rod 5 to the rod 7~ at the end of tlle braclcet.
According ~o yet another variant, the single guide can comprise a steel cable stretched bet~een the topmost part of the pylon and the ends 3~ or 9' of the brackets.
The downward motion of cables Tl and T2 is not instantaneous, even if the inclination of guides 6 and 7 is very steep, but progressi-ve, in proportion as member 3 moves away from pylon 1. The reason is that, as long as member 3 is near the pylon, the ~eight of the ha~lage cables~ ~hich controls ~le do~nward motion~ is offset by the pull on the cables ~owards member 3, i.e. towards the central axis of the line.
llhen member 3 moves a~ay, therefore~ cables Tl and T2 progressive-ly move dotmwards until ~ley meet the end rods 7~. This is the position sho~n in Fig. 3. At this stage the haulage cables fall abruptly do:n.
Note that ~le fall is not absolutely vertical but inclined tol~ards the a~is of pylon 1~ This is because each cable is subjected to t~:o opposing forces - on the one hand the resistance of the cable itsel~
and the associated conductor, ~hich acts substantially parallel to the line~ and on the other hand the tension whicll, o~ing to the re-lative nearness of men~ber 3 to the pylon, is exerted towards ~he central axis of the line.
A guide arm or bollard 10 is disposed belo~ the end of the bracket and has a tip 10~ projecting beyond rod 7~. When cable T falls, it is collected by arm 10~ which is inclined towards the interior and thus guides it towards pulley 11 suspended from ~he bracket.
Pulley 11 has an "open" shape, e.g. as illustrated in Fig. 15.
As Fig~ 15 sho~is, the pulley frame 11a has a substantially C- or G-shape, i.eD a rectangular s~ructure open at the top of one side. One or more ~heels or sheaves are rotakably mounted on the ~rame in order ~o convey a conductor or bundle of conductors. In the illustration 9 ~9~
there are three sheaves 15, 16 and 17, The centrc~l sheave 16 initially conveys the haulage cable, fol-lowed by the transmission member 3, each sheave conveying one conductor from the bundle, As sho~n in the diagram, arm 10 is shaped so that one end thereof lOa, thich prolongs its top edge, terminates at the bottom, under operatin6 conditions, level l.ith the edge of the central sheave 16 as sho:~n. Consequently s~hen the haulage cable~ ~ihich has fallen from the top braclcet, slides along arm 10, it can fit sideways into the frame of pulley 11 and be directly positioned in the groove of the central sheave 16. A stop ann 18 prevents the cable from sliding beyond sheave 16 to~ards sheave 15.
Fig, .~ shows the final or arrival position of the haulage cable ~hen it is properly positioned and centred on the pulley 11 of the top braclcet in the pylon.
The ne~ct stage of operation is sho~n in Fi6. S, ~hich sho~ s that the end T~t of the cable is coupled to a balance-rod mel~ber 3 ~/hich is coupled to the follo~ing:
- in ~le central position member 3 is coupled by attachment 3d to a service cord S, the other end of hich i5 connected to a conven-tional transmission member 12 for a bundle of three conductors C.
- in the lateral position, ~nellber 3 is coupled to another haulage cable T3, ~liCh iS secured to the attacll~ent 3g of nember 3 shol~n in Fig. lBa and is guided over the ends of stirrups 3h.
Before member 3 reaches the pulley, arm 10 is tilted do\~mrards, e.g. into the position ~lo~m in Fig. 6~
When member 3 reaches the pulley, cord S talces the place of the haulage cable T2 on the central sheave 16, At the s~ne time, cable T3 is dra~n beyol~d the outermost sheave of pulley 11 and, ol~ng to the absence of arm 10 which l~s been ~ilted do~mwards, runs along the side 11b and falls freely do~wards.
As shown in Fig, 6, during ~the pulling of the bundle of conductors C, each positionea on a sheave 15, 16, 17 of pulley ll~ the cable - 10~
T3 is fallinc to ards the b~aclcet 9a underneath and bears on a guide 7. Guide 7 is secured to bracket 9a in a ;namler completely similar to the guide 7 associated with the top braclcets ~,9. ~lternatively, guide 7 can be mounted so as to slide bet~een the end of the braclcet underneath and the base of the pulley, as sho~n by a chain-dotted line in ~ig. 6, in ~hich case guide 7 can also stabilize the pulley.
In both cases, the cable falls and abuts the guide underneath o~ing to the fact that the bracket projects e~ternally beyond the vertical axis of the pulley ll underneath.
Fig. 6) acordingly, shows ~he bundle of three conductors C, which no~ rest in the pulley 1l of the uppermost bracket, after the transmission member 12 and l~ulage cable T3 have passed over pulley 11 in three successive positions as follows:
- in posision I, indicated by chain lines, ~hich pulley 11 talces up immediately after the highest pulley 11 has moved along guide 7;
- in position II, indicated by cha~n lines, hich the pulley ta-kes up after sliding along guide 7 and falling belos~ rod 11', i.e.
against arm lOa, and - in position III, indicated by a continuous line, hich pulley 11 talces up ~fter sl;ding along a~ll 10a and entering pulley lla.
During the pulling of the bunch of conductors C over the high-est pulley 11, cable T3 is also pulled over the pulley 11a underneath.
At the moment ~hen member 3 reaches the pulling sta~ion, the bundle of conductors C and cable T3 have been completely extended. At this point, puIling begins on cable T3, which is associated :ith another balance-beam member and another bundle of conductors. ~ig~ 6 shows member 3 arriving near pulley lla and anchored to the haulage pulley, ~:hicn is coupled to a service member S for pull;ng a ~rans~ission mem~er 12 (not shot~n) for another ~ndle of conductor~ and another haulage cable T3l secured to attacl~nent 3g~
Finallyg Fig. 7 shows the stage ~:hen the b~tdle of conductors C ha~e been completely drawn over the highest pulley 11 and ~he bunch of conductors Ct, member 3 and transnission metnber 12 are begiL~ing 7~
to pass over the pulley lla underneath, having just passed the previous pulley. At the moment when member 3 passes pulley lla, cable T3' slides and falls and takes up position on the lowest pulley llb. As before, the fall is shown in various stages, i.e.:
- position I in which cable T3l after sliding from pulley lla, has fallen and abuts the guide 7 of the lowest bracket, and - position II, in which the cable rests on the lowest pulley llb.
Cable T3' is adapted next to draw a bundle of con-ductors like the preceding ones, but of course it is not necessary to draw other haulage cables at the same time.
All the stages described hereinbefore with reference to FigsO 4 to 7, which show the positioning and pulling of the haulage cables and conductors on the right side of the pylon relatively to the drawing, are exactly similar for the left side, either subsequently or simultaneously depending on the chosen operating conditions.
During the aforementioned stages reference has always been made to the motion of a balance-beam member 3, directly drawn by the haulage cable. The last-mentioned cable is pulled while cord S pulls transmission membex 12 and the bundle of conductors. This method is appropriate when it is desired ~o prevent a haulage cable travelling side by side with the conductors; in such cases cord S will be longer or at least equal in length to the length of cable between two pylons, so that the additional haulage cable is moved 9 and consequently moved away from cord 5~ opposite a given pylon along the line, before txansmission member 12 has passed the preceding pylon.
Alternatively, if the preceding requirements does not apply, member 3 can be connected to the haulage cable and also directly connected to the bunch of conductors (via the rotary attachments 3d, 3e and 3f) and to the additional haulage cable (via attachment 3g), thus avoiding the use of transmi 5 S ion member 12.
Fig. 8 shows a different embodiment in which single conductors are stretched on a pylon of the same kind as shown in the preceding drawings.
In ~ig. 8, the pylon is fitted with rods 20 and cables extending between each pulley 22 and the end of the bracket underneath it. Each pulley 22 is associated with a bollard or arm 12 which can take either a closed position (as shown on the left side of the pylon relative to the drawing) in which case motion will occur between pulley 22 and the end of the supporting bracket, or an open position tshown at the right of the pylon) when the cable or conductor will be guided inside the pulley.
The system shown in Fig. 8 can be used for stretching in various ways, some of which will be shown hereinafter. All of them star-t from an initial preliminary stage in which a pilot cord or haulage cable is positioned on the top pulleys 2 by the conventional method, by hand or by a helicopter.
A) - The first haulage cable is used to draw three additional haulage cables as already shown in the case of cables Tl, T2 and G during the first stage of the process illustrated in Fig. 1. The central additional haulage cable remains on pulley 2, whereas the side haulage cables are pulled and slide along the top and the first brackets, arms 21 and 21' of the top pulleys 22 and 22' being closed, so that the cables travel over pulleys 22, descend along the first rods 20, travel over the second pulleys 22', descend along the lower ~2~
rods 20, and finally fall beyond the lowest bracket on to the arm 21" underneath and into pulley 22". During the motion of the cable, the bottom arms 21' open, whereas arms 21 remain closed. The cable remains on pulleys 2 and the pull begins on three other haulage cables. In the same manner as shown previously, the central cable remains on pulleys 2 whereas the two side cables are run and slid down-wards. They travel over the top pulleys 22, down the top rods 20 and, after travelling over the tip of the interme-diate bracket, enter arm 21', which is now open, and areguided into the intermediat~ pulleys 22" . During this second motion of the cables, the top arms 21' also open and, while the cable remains on pulleys 2, the pu11 begins on the guard cable and two further haulage cables. The guard cable remains positioned on pulleys 2, in order subsequentary to be secured at the top of the pylon, whereas the two supplementary cables are moved and slide along the top brackets on to the open arms 21 and are guided into the top brackets 22. When the haulage cables are positioned in each bracket, the con-ductors are tensioned in the usual manner.
Of course, instead of pulling six complete haulagecables in the aescribed manner, service cords can be used for the drawing operations and directly coupled to the conductors.
s) - As an alternative to A), five haulage cables instead of three can be drawn during the first operation. The central cable is positioned on pulleys 2 whereas the other cables are conveyed, two on the left and two on the right of the pylon, and are guided in the previously-described manner over the intermediate pulleys 22' and bottom pulleys 22" , arm 21' being opened immediately after the first of ea~h pair of cables travels over it. Next, the cable which has remained on pulleys 2 is used to pull the guard cable and the two cables to be positioned on the top pulleys 22. Preferably the first five haulage cables are drawn by two balance-beam members in succession. a first balance member drawing two haulage cables and a central service cord of reduced length, and a second balance member coupled to the service cord and pulling the other three haulage cables. This facilitates the drawing process and prevents two cables from sliding together over the same bracket and twisting.
C) - If a sufficiently powerful which is available, another alternative consists in drawing six haulage cables and the guard cable simultaneously; the central guard cable is positioned on pulleys 2 whereas the haulage cables are drawn three to the right and three to the left of the pylon. In order properly to position the cables on pulleys ~2, 22' and 22" , the top arm 21 is opened immediately after two of the cables have run over it, whereas arm 21' is open~d immediately after one cable has run over it.
In this case also it is preferable to use three balance members in rapid succession one after the other, as already explained in alternative b).
D) - Alternative methods can be used, as chosen by the skilled in the art, for simultaneously pulling five haulage cables and conductors. These other methods, if any, will of course be decided upon in accordance with the operating conditions and the available means, without modifying the essential features of the inventionO
The aforementioned methods of tensioning single conductors can of course also be used for tensioning bundles of conductors. More particularly~ instead of proceeding in the method indicated in Figs. 1 to 7, all six haulaye cables can be positioned first, e.g. by one of the methods A) to D) hereinbefore, after which each haulage cable can be used ~9;~:~71~
to tension a respective bundle of conductors in conventional manner in the preferred sequences.
Figs. 9 to 11 show the sequence of operations according to the invention for tensioning on an asymmetrical pylon having three brackets.
As shown in Fig. 9, a pilot cord is positioned in conventional manner, i.e. manually or by helicopter, on the top pulleys 2 and is replaced by a first cable T, which is used to pull the guard rope G and three additional haulage cables Tl/ T2 and T3. The pull is applied via an asymmetrical balance member 25 diagrammatically shown in Fig. ~.
FigO lO shows the balance member 25 when it has just passed the top pulley 2. The guard cable G is thus positioned in the groove o pulley 2 in the previously-described manner. The three haulage cables are drawn one on one side and two on the other si~e of pylon 1.
Cable Tl, which is drawn to the left of the pylon~
descends along guides 6 and 7 until it reaches the end of the left bracket, from which it falls, guided by arm 27, into pulley 26.
Cables T2 and T3 descend along guides 6, 7 borne by the top right bracket to the end thereof, where a pulley 26' is secured with a closed arm 21 and a rod 20 completely similar to that illustrated in Fig. 8 is secured between pulley 26l and the bracket underneath. As soon as cable T3 has moved over the top bracket and arm 21 and pulley 26', arm 21 opens. Thus~ whereas cable T3 slides down along rod 20 to fall on to the open arm 21' and be guided into pulley 26" , cable T2 falls into arm 21, which is now open, and is guided into pulley 26l~.
Fig. 11 shows the final position in which cables Tl, T2 and T3 have been finally positioned in the respective pulleys 26, ~6' and 26" and are ready to pull singl~
conductors or bunches of conductors as required.
Of course, as already stated, instead of stretching haulage cables over the entire length of the line and then using them to stretch the conductors, the balance member 25 can be attach~d to service cables which are directly attached to conductors or bundles of conductors, the service cables performing the function of moving until they rest in the pulleys underneath.
As alread~ stated it may be preferable, instead of attaching all three cables and the guard cable to the same balance member 25, to use a first balance member attached to cables T1 and T2 and a short central cable, which is attached to a second balance member for drawing the guard cable G and cable T2.
Figs. 12 and 14 show the sequence of operations according to the invention for drawing over a Y-type pylon.
As is known, in a pylon of this kind the conductors are suspended from insulators Jl, J2, J3 borne by two side brackets 30, 31 and a central cross-member 32. The pylon also h.as two small tips 33, 34 each bearing a guard cable.
According to the invention, an additional central tip 35 is positioned on the aforementioned known pylon and used exclusively for the system of tensioning according to the invention, and is therefore preferably dismantle~ after the tensioning operation has been completed.
Apex 3S bears the previously-described top pulleys 2 and is also secured to guides 6, which preferably run from pulley 2 to the.top of apices 33 and 34, and guides 7, which run from apices 33, 34 to the outer ends of bracke~s 30, 31 respectively n Tensioning is performed as follows:
'7~3 - 16a -- the first haulage cable is positioned on pulley 2 in the conventional manner as pxeviously mentioned and is used to pull a balance member 36 secured to two guard cables Gl, G2 and three haulage cables Tl, T2 and T3.
Fig. 12 shows member 36 approaching pylon 1. Fig.
12 also shows how, according to an important feature of the invention, the central cable T3 is not pulled directly by member 36 but by a pair of service cables S1, S2 connected by joints which can easily be dismantled, and the purpose of which will be described in detail hereinafter.
One service cable - cable Sl in the present case -is under tension, whereas the other is slack. Consequently, when member 36 travels over the pulley, only cable Sl remains on it, whereas (Fig. 13) guard cable Gl and haulage cable Tl are slid towards the centre of the pylon, guard cable G2 and haulage cable T2 are slid towards the right of the pylon (relati~e to the drawing in al' cases), whereas cable S2 can be slid either rom the right or the left of pulley 20 As soon as member 36 has passed pulley 2, the pull is temporarily stopped. An operator disconnects the slack cable S2 and conveys it below cross-member 32 and then re-secures it. The operator also, using special equipment, tensions cable S2 and consequently relaxes Sl. Fig. 13 shows this exact moment, when cable S2 has just been re-attached and tensioned. Immediately afterwards, the operator releases cable Sl, now slack, and conveys it under member 32 and re-attaches it, at which point the pull can recommence.
As Fig. 13 also shows, cables Tl and T2 have been slid along guides 6 and after opening two small arms ~not shown) at the top of apices 33, 34) bear against guides 7 above brackets 30 and 31; guard cables G1 and G2 have been slid along guides 6 and, since the arms are open, have taken - 16b -up position on pulleys (not shown) at the top of apices 33 and 34, Finally Fi.g. 14 shows how, when member 36 moves further away from the pylon, haulage cables l'l and T2 slide along guides 7 and fall from brackets 30~ 31 and are guided ln the previously-described m~tner o~er arms (not sho n) under the ends of the braclcets, ~hich gttide them ~tto cornespondin~ pulleys (also not shotn). Fi6. 1~ sho~:s this final configuration, in hich haula~e cables T1, T2 are disposed in pullcys suspended frolt insulators J1 and J2, the ccntral haulage cable T3 is disposed in a pulley suspended from insulator J3 and the ~uard cablcs G1, G2 nre disposed in pulleys (lilce the precedin~, not sho n) at ~te top of apices 33 and 340 As Fig. 14 also sho:.~s, the central apex 35 llas been di~nantled, since it is no longer necessa-ry.
In ~lis ¢ase also, instead oP attaching the three haulage ca-bles and the two guard cables to a single balance mem~er 36, it may be preferable to use a first balance member to pull the t~o outer cables T1 and T2 and a central cable, which is attached to a second balance ntember for pullin~ the t~o guard cables and the central hau-lage cable T3.
~ Iroughout the description, reference has been made to the ini-tial positioning of a pilot cord by con~cntional methods, i.e. by hand or by helicopter, and used firstly to pull a haula~e rope. This ~anner of c~pression is based on the usual technique, in hich the pilot cord is a liglt cable of syntlletic material such ~s mJlon~
-hich l~akes it ~asier ~o posi~ion, ~ereas ~he haulage cable is nor-mally of steel and relati~ely heavy, and more particularly capable of ithstanding considerable ~tension and not accumulating torques.
Of course it is possible, and is actually practiced, for the cable initially positioned on the top pulleys to be capable of directly pulling the conductors.
~ lore particularly in the last case, but of course also in the morc general case :here a pilot cord is used ~ollowed by ~ 1~ulage cable, ~he balance members used for pulling lill first be secured to the service cables, uhic'n will be ad2pted for sliding and moving from the top pulleys to the bottom pulleys, to which the conductors or bundles of conduc~ors or haulage cables ~ill subsequently be at-tached~
~9Z~7~
The cld~ nta6es of the method according to the invention are con-siderable. In addition to ~le previously-mentioned main advanta~es of rapid performance, particularly on difficult or irreg~ualr routes, and of protecting khe vegetation underneath, there is also a consi-derable reduction in the need for pilot cord, the power lines remain out of operation for only a short ~ime, and owing to its lo~r expen-se, as previously mentioned, the method of controlled tensionin~ can be extended to less important lines, e.~ 150 IcV. Other advanta~es can easily be seen by the sldlled in the art.
~ lowever, the invention is not limited to the particular embodiments or procedures described, or to the only specific use which has been disclosed, but can have many variants, including uses, e.~. for stret-ching relpher cables or ~he like~ hic}l are all within reach of a technician slcilled in the art, and therefore are all falling Irithin the protec-tion scope of the present invention.
Claims (33)
1) A method of controlled tensioning of high tension electric power lines, the method being of the and in which two respective haulage cables are first conveyed over a set of pylons bearing conductors distributed along a given route, more specifically along at least two pulleys suspended from each pylon at places for attaching at least two conductors at various levels, after which conductors or bundles of conductors are pulled in controlled manner under constant tension conditions, characterised in that:
- a pilot cord or haulage cable is disposed in conventional manner on the set of pulleys at the highest level;
- the pilot cord or haulage cable is recovered from one end by running it over the set of high level pulleys, whereas the other end is coupled to a primary cable and at least one supplementary cable;
- the primary cable is guided into position along the groove of each pulley at the highest level and each supplementary cable is guided so as to run over the high-level pulleys and then slide slowly downwards and finally fall on to the lower-level pulleys; and - each supplementary pulley positioned on the lower-level pulleys is used directly for drawing a conductor or bunch of conductors and simultaneously drawing another supplementary cable if required.
- a pilot cord or haulage cable is disposed in conventional manner on the set of pulleys at the highest level;
- the pilot cord or haulage cable is recovered from one end by running it over the set of high level pulleys, whereas the other end is coupled to a primary cable and at least one supplementary cable;
- the primary cable is guided into position along the groove of each pulley at the highest level and each supplementary cable is guided so as to run over the high-level pulleys and then slide slowly downwards and finally fall on to the lower-level pulleys; and - each supplementary pulley positioned on the lower-level pulleys is used directly for drawing a conductor or bunch of conductors and simultaneously drawing another supplementary cable if required.
2) A method as in claim 1), in which each pilot cord or initial haulage cable is positioned manually in known manner in the highest-level pulleys.
3) A method as in claim 1), in which each pilot cord or initial haulage cable is positioned by a helicopter in known manner on the highestlevel pulleys.
4) A method as in claim 1) for tensioning a power line in at least three phases, in which:
- the pilot cord or haulage cable is first positioned on pulleys at the tip of each pylon along the line;
- the pilot cord is used to pull a guard cable and two supplementary cables by means of a balanced connecting joint, and when the balanced member moves over the top pulleys the guard cable rests on them where-as the supplementary cables are slid and guided downwards until they take up position on the pulleys suspended from the brackets immediately underneath; then each supplementary haulage cable is used to pull a conductor or bundle of conductors together with at least one other supplementary haulage cable for drawing at least another conductor or bundle of conductors subsequently underneath.
- the pilot cord or haulage cable is first positioned on pulleys at the tip of each pylon along the line;
- the pilot cord is used to pull a guard cable and two supplementary cables by means of a balanced connecting joint, and when the balanced member moves over the top pulleys the guard cable rests on them where-as the supplementary cables are slid and guided downwards until they take up position on the pulleys suspended from the brackets immediately underneath; then each supplementary haulage cable is used to pull a conductor or bundle of conductors together with at least one other supplementary haulage cable for drawing at least another conductor or bundle of conductors subsequently underneath.
5) A method as in claim 4) in which, in order simultaneously to draw a supplementary haulage cable and a conductor or bundle of conductors an intermediate portion of service cable is disposed between the conductors and the main haulage cable, the supplementary haulage cable being placed alongside the service cable in order to draw it.
6) A method as in claim 1) for tensioning a power line in at least three stages, in which:
- the pilot cord or haulage cable is first positioned on pulleys at the top of each pylon along the line;
- The pilot cord is used to draw a central haulage cable and two supplementary side haulage cables, using a balanced connecting joint, and, when the joint moves over the top pulleys, the central cable takes up position in the grooves of the central pulleys whereas the supplementary cables are slid and guided downwards until they are positioned on the pulleys suspended from the lower brackets on the pylon;
- next, each supplementary haulage cable is used to draw a conductor or bunch of conductors to be positioned on the pulleys suspended from the lower brackets of the pylon, whereas- the central cable is used to pull another central cable or guard cable to be positioned on the top pulleys together with at least one other supplementary side cable for drawing at least another conductor or bundle of conductors to be positioned on the pulleys above the last-mentioned pulleys.
- the pilot cord or haulage cable is first positioned on pulleys at the top of each pylon along the line;
- The pilot cord is used to draw a central haulage cable and two supplementary side haulage cables, using a balanced connecting joint, and, when the joint moves over the top pulleys, the central cable takes up position in the grooves of the central pulleys whereas the supplementary cables are slid and guided downwards until they are positioned on the pulleys suspended from the lower brackets on the pylon;
- next, each supplementary haulage cable is used to draw a conductor or bunch of conductors to be positioned on the pulleys suspended from the lower brackets of the pylon, whereas- the central cable is used to pull another central cable or guard cable to be positioned on the top pulleys together with at least one other supplementary side cable for drawing at least another conductor or bundle of conductors to be positioned on the pulleys above the last-mentioned pulleys.
7) A method as in claim 6), in which each central haulage cable comprises a portion of service cable, also having a short length.
8) A method as in claim 7), in which each supplementary haulage cable comprises a service portion, preferably having a length equal to the length of cable between two pylons.
9) A method as in claim 1), in which each supplementary haulage cable, when drawn from an upper pulley is slid towards a lower pulley along guide means associated with the pylon structure and along guide means associated with the pulley underneath.
10) A method as in claim 9), in which the guide means associated with the pylon structure are removed when the line has been tensioned.
11) A method as in claim 9), in which the guide means associated with the pulley underneath are tilted into an inoperative position after being used to guide a supplementary cable into the pulley.
12) A method as in claims 4) and 11), in which the guide means associated with each higher pulley are normally open and in operation to receive the first supplementary haulage cable guided downwards, and when the aforementioned cable is received in the groove of the pulley it tilts the guide means into the closed or inoperative position so that the next supplementary haulage cable guided downwards can move over the pulley and fall on to the pulley beneath.
13) A method as in claim s 6) and 11), in which the guide means associated with each topmost pulley are normally in the closed inopera-tive position and the first supplementary haulage rope guided downwards slides over the pulleys and falls on to the lower pulley and simulta-neously opens the guide means to that the next supplementary haulage cable guided downwards is received in the pulley immediately above.
14) A method as in claim 1) in which each haulage cable is pulled, followed immediately by the respective conductor or bundle of conductors together with the haulage cable for the next conductor or bundle of conductors.
15) A method as in claim 1) in which all the haulage cables are first drawn one after the other followed by all the conductors or bundles of conductors one after the other.
16) A device for working the method according to claim 1, of the kind comprising a number of pulleys for conveying cables and conductors for suspending from each bracket along each pylon in the line, each pulley comprising a suspended frame on which one or more freely rotatable sheaves are mounted for conveying the cables or conductors, characterised in that the suspended frame of each pulley is open on one side for inserting a cable along an intermediate portion thereof.
17) A device as in claim 16) in which the suspended frame of each pulley has a substantially open shape in the form of a C or G.
18) A device as in claim 17) in which the open side of the frame is associated with guide means comprising a sloping bollard or arm extending downwards and towards the interior of the frame to guide the supplementary haulage cable after it has fallen from the bracket above.
19) A device as in claim 180, in which the guide means or arms are tiltable into the inoperative position after conveying the supple-mentary haulage cable into the pulley.
20) A device as in claim 16), further comprising guide means associated with the pylon structure and forming also elements for keeping at a distance fro the structure and protecting it.
21) A device as in claim 20 in which the guide means associated with the pylon structure run between the base of each pulley and the outermost end of the bracket underneath.
22) A device as in claim 21) in which the guide means comprise rods.
23) A device as in claim 22) in which the guide means comprise tubular rods mounted so as to be freely rotatable around their longitudinal axis on stationary holders associated with the pylon structure.
24) A device as in claim 21) in which the guide means comprise portions of stretched cable.
25) A device as in claim 21 in which the guide means also stabilize the pulley with which they are associated.
26) A device as in claim 16) also comprising a balanced joint in the form of a triangular plate for connecting a haulage cable to one or more supplementary conductors and/or cables.
27) A device as in claim 26) in which the means for attaching the supplementary conductors and/or cables to the balanced means are disposed symmetrically relative to the central or pulling axis of the balanced means.
28) A device as in claim 27) in which the balanced means have additional, asym etrically disposed attachment means for attaching a supplementary haulage cable to be drawn.
29) A device as in claim 27) or 28) in which the means for attaching supplementary conductors and/or haulage cables are freely rotatable.
30) A device as in claim 26) in which the balanced means are associated with a counter-weight for stabilizing it in a horizontal position.
31) A device as in claim 16) also comprising a top pulley with a sheave having a groove opening upwardly above the top of the pylon.
32) A device as in claim 31) in which the top pulley is mounted on the central point of the pylon.
33) A device as in claim 31) in which the top pulley is mounted on an apex temporarily placed at the centre of the top crossing of a Y pylon.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406492A CA1192178A (en) | 1982-07-02 | 1982-07-02 | Method of stretching high-tension electric power lines and a device for performing the method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406492A CA1192178A (en) | 1982-07-02 | 1982-07-02 | Method of stretching high-tension electric power lines and a device for performing the method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1192178A true CA1192178A (en) | 1985-08-20 |
Family
ID=4123143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000406492A Expired CA1192178A (en) | 1982-07-02 | 1982-07-02 | Method of stretching high-tension electric power lines and a device for performing the method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1192178A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109524921A (en) * | 2019-01-17 | 2019-03-26 | 国网江苏省电力有限公司太仓市供电分公司 | A kind of cable wiring device |
| CN120473828A (en) * | 2025-07-14 | 2025-08-12 | 陕西惠齐电力科技开发有限公司 | An intelligent centralized grounding box for railway traction depot |
-
1982
- 1982-07-02 CA CA000406492A patent/CA1192178A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109524921A (en) * | 2019-01-17 | 2019-03-26 | 国网江苏省电力有限公司太仓市供电分公司 | A kind of cable wiring device |
| CN120473828A (en) * | 2025-07-14 | 2025-08-12 | 陕西惠齐电力科技开发有限公司 | An intelligent centralized grounding box for railway traction depot |
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