CN101501788A - Electrical power cable with frangible insulation shield - Google Patents
Electrical power cable with frangible insulation shield Download PDFInfo
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- CN101501788A CN101501788A CNA2006800554152A CN200680055415A CN101501788A CN 101501788 A CN101501788 A CN 101501788A CN A2006800554152 A CNA2006800554152 A CN A2006800554152A CN 200680055415 A CN200680055415 A CN 200680055415A CN 101501788 A CN101501788 A CN 101501788A
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Abstract
An electrical power cable has an insulation shield with at least one path of weakness along a length of the cable to facilitate stripping. When the path of weakness is a score or groove, a thickness of the insulation shield -between a bottom of the at least one groove and the outer surface of the underlying insulation layer is about 1-15 mils. Preferably, blades arranged around the circumference cable following extrusion of the insulation shield cut the at least one groove continuously into the shield along the cable's length. The at least one groove, or other means for imparting weakness, enables an installer to easily strip the insulation shield in the field with minimal use of specialized tools.
Description
Technical field
Technical field of the present invention relates to power cable.More specifically, technical field of the present invention relates to the medium-pressure power cable with semiconductive insulation shield, and this semiconductive insulation shield is configured to improve joint or the termination of stripping performance to be used for cable of cable.
Background technology
Be used for distributing and press the power cable of (being 5kV to 46kV) to generally include several layers.These layers comprise electric conductor, the semiconductive shield of wrapping, are formed at insulator layer, the semiconductive insulation shield on the insulator layer, metal skirt and outermost protecting sheathing on the semiconductive shield.
Fig. 1 shows exemplary normal cable 100.Heart place therein, conductor 110 is made by copper, aluminum or aluminum alloy usually.Conductor 110 is solid or stranded, and the stranded flexibility that increases cable.If stranded, then conductor often comprises strand seal to fill its space, and this helps anti-sealing to move along conductor.Surround conductor 110 by the conductor shield 115 that semi-conducting material forms.
The layer that insulator 120 surrounds conductor shield 115 and normally extrudes.Insulator 120 is at conductor 110 and nearest provide electric insulation between electrical ground, thereby prevents power failure.Usually, insulator 120 is made by polyethylene, crosslinked polyethylene or ethylene-propylene rubber.Insulation shield 125 surrounds insulator 120 and generally makes by extruding semiconductor layer.
Term " core " is commonly used to represent the combination of conductor, conductor shield, insulator and the insulation shield of cable.
Concentric neutral elements 150, insulation shield 125 and conductor shield 115 help the control electric stress, and more symmetrical electric field is provided in cable 100.Polymeric semiconductive guard shield, such as insulation shield 125 and conductor shield 115, being applied to grade usually is to be used for the cable of voltage greater than 2kV.These guard shields provide intermediate conductivity between high potential conductor 110 and main guard shield 120 and between main guard shield 120 and ground connection or neutral potential 150.
Joint or termination power cable require sequentially to remove shell 130, semi-conductive insulator layer 125 and insulator 120 such as 100.Fig. 2 A and 2B show the stage of peeling off two midium voltage cables that are used to engage.Shown in Fig. 2 A, shell 130 at first is removed predetermined distance, exposed insulator guard shield 125.Concentric neutral elements 150 is pulled rearward so that use after engaging after a while.And insulation shield 125 is cut circumferentially or longitudinally in the predetermined distance of distance cable end, and this part of insulation shield 125 removes from insulator underlying 120.Shown in Fig. 2 B, make that then near the circumferential notch the cable end is passed insulator 120 and conductor shield 115 (not shown).After making this otch, the part that insulator 120 and conductor shield 115 are positioned at cable end is removed, and exposes conductor 110 at cable end.When being used for the individual cable of termination, preparation follows similar step.
It can be challenging peeling off midium voltage cable, when carrying out especially in the open air.For example, the various polymer layers in the cable moderately combine, and make them be difficult to separate when joint or terminated cable.Shell and insulation shield are easy to owing to condensate (for example polyethylene) shell and the affinity that is used as this class material of semiconductive insulation shield usually are bonded together.And polymer layer 115,120,125 and 130 is being squeezed under pressure during the cables manufacturing usually.Pressure extrusion causes the void area between the polymer material packed layer, and is generally polymer material (for example polyethylene) that this treatment of selected selects and has after extruding the trend of contraction downwards.Tight formation and slight mechanical bond between the layer help avoid harmful space, and have minimized otherwise any discharge that will for example occur between insulator layer and semiconductive insulation shield.So, need the power of 3 to 24 pounds (about 13.3 and 107N between) that insulation shield is removed from its insulator underlying layer usually.
In addition, in peeling off the semiconductive insulation shield of midium voltage cable, carefully cut channel or cutting to avoid following insulator layer, this can cause being used to engaging or the attachment body of terminated cable in the formation of electrical stress points.As explained above, peel off midium voltage cable and relate at first from cable end and remove the cable jacket of preset distance and remove the insulation shield of certain-length then.In the cutting insulation shield, setter must carefully can not be cut in the insulator layer, because these cables move under high electric stress, has the largest conductor operation stress up to 50% on the insulator surface.The cutting of passing conductor shield and entering insulator even only be one millimeter part, is engaging or termination also can cause partial discharge (ionization) in the cut place after finishing.
Therefore, in order to engage or the termination midium voltage cable, setter is usually by beginning for after removing shell the insulation shield indentation.But score cuts is passed the surface of insulation shield is preferably not exclusively passed material to avoid making indentation on the insulator layer below.A spot of insulation-shield material is stayed the base portion place (general about 5 mils (0.127 millimeter) or littler) of indentation.Tool using, setter usually from the end of cable to apart from the end predetermined distance that need remove insulation shield, form along the cable indentation of process vertically or spirally.In case insulation shield is by indentation, its can be along the longitudinal or the helical scores mark by peeling with the exposed insulator layer.Peel off in order to finish under the situation of vertical or helical scores, setter is the peeling band backward, to expose the insulating surface of predetermined length.It is difficult carrying out this accurate indentation in the open air.
U.S. Patent No. 5,987,204 and No.6,148,130 disclose signal-transmitting cable, and it is provided with the predetermined discrete link position that is incorporated in the cable during the manufacturing of cable.Particularly, the zone of at least one pre-indentation is formed at during the cables manufacturing process in the cable protection coating that surrounds cable conductor, connects in the open air so that be easy to.The user can need not to use under the situation of special tool(s) the application of force to come to break the protection coating so that connect at pre-indent locations place.After pre-indentation is broken coating, can remove coating by the protection coating is slided along cable as required.
U.S. Patent No. 4,993,147 have described a kind of automatic mode that is used to cut and peel off insulator under the situation of not pre-indentation.One or more blades move in a predetermined manner with respect to the insulated conductor that remains in the fixed position.Insulator is cut to certain depth and after this cuts off and from cable stripping.
Other document discloses is not having to use releasing member to improve peeling off of cable under the special tool(s).For example, U.S. Patent No. 5,611,017 discloses a kind of ribbon fiber cable, it comprise periodically be arranged between whole coating and the optical fiber, to allow to be easy at least one releasing member near optical fiber.U.S. Patent No. 5,008,490 relate to the flat belt-like telecommunication cable of electric screen, wherein the gauze material arrangements below electric guard shield so that guard shield is easy to remove.
U.S. Patent No. 6,858,296 have put down in writing the special composition of integral insulation body guard shield, to improve its rippability maintaining heat stability simultaneously.
The applicant has been noted that said method does not all have to solve owing to the high electric stress of this cable inherence in the problem of giving the insulation shield indentation and bringing from midium voltage cable is peeled off.The applicant be also noted that existing design do not provide a kind of under the situation of minimum ground tool using, in the open air, along any point of cable, from the midium voltage cable peeling or peel off the technology accepted of insulation shield.
Especially; above-cited U.S. Patent No. 5; 987; 204 and 6; 148,130 relate to signal-transmitting cable, such as fiber optic cables or power cable; wherein provide the pre-scored areas of annular (being circumference) of cable protection coating to be used for engaging and/or purpose of connecting under the situation of exfoliation tool need not, described pre-scored areas is provided with predetermined interval along cable length.
Above-mentioned annular indentation is provided in the cable protection coating so that its part can remove; make described part and all the other electrical cables separate by on described part, applying pulling force, and thereby make described part on the cable core that is positioned the inner radial position with respect to the cable coating, slide.
The applicant observes, and at least owing to following reason, above-mentioned annular indentation can not put on the insulation shield of medium and high voltage cable effectively.
At first, the insulation shield of medium and high voltage cable need be bonded to the insulator underlying layer securely.In fact, the existence in space and the existence of therefore catching air make the generation that causes partial discharge when voltage stress surpasses the dielectric strength of air between insulator layer and the insulation shield, described partial discharge since ozone formation be unfavorable for insulator layer and cause the premature failure of cable.Therefore, because the insulation shield of medium and high voltage cable need be bonded to the insulator underlying layer, the existence that is located at the annular indentation in the insulation shield does not allow insulation shield to remove by sliding on insulator layer.
Secondly, because return current (charging current or fault current) flows in the insulation shield of medium and high voltage cable usually, this insulation shield can not be provided with annular indentation, and the appearance of annular indentation will stop return current correctly to flow in insulation shield.
The 3rd, because annular indentation is provided at predetermined intervals along cable length, when selecting suitable size for cable prepares, setter can go wrong.For example, when under situation about engaging between two medium and high voltage cable, selected annular indentation should have suitable insulator layer length correctly to receive the joint in the engaging zones, and described length for example changes with respect to the diameter of wanting junction cable.
In addition, the applicant has been noted that to above-mentioned signal-transmitting cable annular indentation being set only needs very little accuracy.In fact, only need to control minimum width of nick, as long as the protection coating can be easy to separate and conductor is not cut or damages.The applicant observes, owing to related to low pressure, electric stress is very little and very little with the relation of pre-indentation.
U.S. Patent No. 5,611,017 and 5,008,490 disclose and have been arranged in the releasing member that below guard shield or the covering, directly or closely contacts cable or optical fiber, to be convenient to for the termination purpose near conductor or optical fiber.The applicant observes, because these cables move under low-down voltage, releasing member can not bring any electrical problems to cable.On the contrary, considering under the situation of medium and high voltage cable that any material that is arranged between insulator and the insulation shield will be the potential source that the run duration partial discharge begins, causing cable morning and too early inefficacy.
Summary of the invention
The applicant has realized that need provide a kind of medium and high voltage cable, its permission is easy to remove the cable insulation guard shield at cable between the preparatory stage and between installation period, carefully operate special tool(s) in the open air to form extremely thin otch under the situation that following cable insulation layer is not caused any injury and need not those of skill in the art.
The applicant has been found that the problems referred to above can solve satisfactorily by the cable insulation guard shield with at least one paths of weakness is provided, and described paths of weakness is longitudinally located along cable length and is beneficial to vertically peeling off of cable insulation guard shield.
Therefore, according to principle of the present invention, a kind of power cable comprises core with at least one conducting element, surround the semiconductive conductor shield of core, surround conductor shield and have outer surface insulator layer, surround insulator layer and contact the insulation shield of described outer surface and the shell that surrounds insulation shield.Insulation shield has structure along the length of cable and is convenient at least one paths of weakness that insulation shield is vertically peeled off, and shell surrounds insulation shield.
According to principle of the present invention, term " insulation shield " or " outside semiconductive layer " are used for representing to surround and contact the cable polymer layer of cable insulation layer.This polymer layer is bonded to insulator layer securely and preferably obtains by extruding.Preferably, base polymeric material comprises the carbon black of conduction, and it makes insulation shield conduct electricity.Preferably base polymeric material is non-crosslinked polymeric material, for example polyacrylate compound.Preferably, the amount of selecting carbon black is for the volume resistance value less than 500 Ω m is provided to insulation shield at room temperature, preferably less than 20 Ω m.
Described at least one paths of weakness is extended continuously along whole length of cable.In one embodiment, the path be straight basically and with the parallel axes of cable.In another embodiment, the path centers on the axis of cable basically spirally.
In one aspect, described at least one paths of weakness is groove or the line of weakness in the insulation shield.The thickness of insulation shield is about 1-15 mil (approximately 0.025-0.381mm) between the outer surface of the bottom of described at least one groove and insulator layer, preferably about 5-10 mil (approximately 0.127-0.254mm).
In one aspect of the method, described at least one paths of weakness is drag-line or embeds one of releasing member in the insulation shield.Releasing member can comprise band or other material different with insulation-shield material, and it carries out co-extrusion with insulation shield along paths of weakness during manufacture.
And according to principle of the present invention, a kind of method that is used to produce the power cable with improvement fissility comprises: the cable core with at least one conducting element is provided; Around core, apply the conductor shield of semiconductive; Insulator layer is provided around conductor shield; Around insulator layer, squeeze out insulation shield; Length along cable is given paths of weakness in insulation shield; And on by the insulation shield of indentation, squeeze out shell.Apply the semiconductive conductor shield, insulator layer is provided and squeezes out insulation shield and can carry out simultaneously by co-extrusion.
In one aspect, in insulation shield, give paths of weakness and relate to above insulator layer radially with the degree of depth of insulation shield indentation to about 1-15 mil (approximately 0.025-0.381mm).Preferably, indentation occurs to the approximately degree of depth of 5-10 mil (approximately 0.127-0.254mm) of insulator layer top.
The indentation insulation shield can relate to before the extruding of shell, cable is longitudinally moved through at least one locate the blade of cutting the insulation shield outer surface.Two blades can be arranged as substantially parallel to each other or angled to each other to improve the fissility of insulation shield.Alternatively, blade can rotate around the cable circumference, is imparted into the groove with helical or spiral in the surface of insulation shield.
Alternatively, giving at least one paths of weakness can relate to other material is co-extruded into insulation shield layer.The co-extrusion material can comprise that the strength of materials is different from those materials of insulation shield or the drag-line of embedding insulation shield.
It is to be understood that the general introduction of front and following specific descriptions all only are exemplary and indicative rather than to the restriction of described invention.Aforementioned background art and summary of the invention are not to carry out any independent restriction to the present invention.
Description of drawings
The accompanying drawing that is incorporated into this and constitutes this specification part shows several embodiments of the present invention, and is used for explaining principle of the present invention with describing.
Fig. 1 is vertical perspective view of conventional electric power cable.
Fig. 2 A is the end view of two conventional electric power cables that is in the phase I of joint.
Fig. 2 B is the end view of two conventional electric power cables that is in the second stage of joint.
Fig. 3 is the vertical perspective view that has the power cable of orthoscopic paths of weakness according to the embodiment of the invention.
Fig. 4 is the vertical perspective view that has the power cable of spirally paths of weakness according to a further embodiment of the invention.
Fig. 5 illustrates to make the flow chart of the step of power cable in accordance with the principles of the present invention.
Fig. 6 A is used for the cross-sectional view of parallel orientation that insulation shield at the power cable of Fig. 3 or 4 produces the blade of groove.
Fig. 6 B is used for the cross-sectional view of inclined orientation that insulation shield at the power cable of Fig. 3 or 4 produces the blade of groove.
Embodiment
The following specifically describes with reference to accompanying drawing.As possible, identical Reference numeral is used to refer to identical or similar parts in the accompanying drawings and the description below.Though described several exemplary versions of the present invention and characteristics here, modification, modification and other enforcement can have been arranged not breaking away under the spirit and scope of the present invention.For example, to parts shown in the accompanying drawing can make alternative, replenish or modification, and exemplary method described herein can by disclosed method is substituted, rearrangement or replenish step come modification.Therefore, description concrete below does not limit the present invention.On the contrary, correct scope of the present invention is limited by appended claims.
According to principle of the present invention, power cable comprises cable core with at least one conducting element, surround the semiconductive conductor shield of core, surround conductor shield and have outer surface insulator layer, surround the insulation shield of insulator layer and contact outer surface.In position to the outside, cable core footpath, cable is provided with metal skirt and shell.Insulation shield comprises at least one paths of weakness of portion within it, so that the peeling of insulation shield or peel off being used for engages or terminated cable.
As specific and disclosed in Fig. 3 generally here, cable 300 comprises conducting element 310.Conductor 310 generally is solid or stranded.Preferably, conductor 310 is made by copper, aluminum or aluminum alloy.
Cable core also comprises the conductor shield 320 of surrounding conducting element 310.Conductor shield 320 is made by the semiconductive material, and its polymer matrix preferably is selected from ethylene vinyl acetate (EVA), ethene ethyl acetate (EEA), ethene methyl acetate (EMA), ethylene-propylene rubber (EPR), ethene acetic acid butadiene ester (ethylene butadiene acetate), chlorosulfonated polyethylene (CSPE), polyethylene (PE).
The thickness of insulation shield 340 can change according to power cable type and application.As an example, under the situation of medium-pressure power cable, the thickness of insulation shield can be in 0.5 to 2mm scope.
Yet insulation shield 340 normally mechanically is attached to the extrded material that insulator layer 330 can remove from insulator layer 330.Mechanical attachment has advantageously minimized any partial discharge that not so can come across between insulator layer 330 and the insulation shield 340.As discussed further below, under the situation of medium-pressure power cable, the power in common available 3 to the 24 pounds of scopes of mechanical attachment is broken.
As shown in Figure 3, a plurality of conduction twisted bundles 360 or concentric neutral elements are positioned insulation shield 340 outsides.Concentric neutral elements 360 under failure condition as neutral return current path and therefore sizing correspondingly.Element 360 preferably is arranged in around the axis of cable 300 and along the twisting spirally of its length with one heart.Neutral element 360 is copper cash normally.Though the most conventional concentric neutral cable has the neutral line of size from #14 AWG to #8 AWG (about 1.63 to 3.26mm) scope, neutral element 360 can have the size of any reality, such as from #24 AWG to #8 AWG (about 0.51 to 3.26mm).Alternatively, their all sizes can be in about per inch 5000 circular mil from the insulating core diameter to the overall dimension scope of conductor 310.They also can be configured to flat band or other non-circular shape when implementing to allow.
Though not shown, can come the neutral element 360 of instead of concentric with metal skirt.Metal skirt can be the band of expectation electric conducting material (such as copper or aluminium), and its longitudinally folding or twisting spirally is to form circumference and longitudinally continuous layer.Preferably, metal skirt is a ripple.
Generally as shown in Figure 3, the insulation shield 340 of cable 300 comprises at least one paths of weakness 350 along cable length.This paths of weakness can comprise known being used to of the prior art any method of insulation shield 340 strengths of materials that weakens, thereby is convenient to insulation shield 340 is separated into a plurality of vertical section.In a preferred embodiment, described at least one paths of weakness is indentation or groove.Groove 350 can have Any shape or size and be used to provide the path of insulation shield thickness less than other places guard shield thickness.
Groove 350 should enough extend into insulation shield 340 deeply to be separated along groove to allow insulation shield, to such an extent as to but whether pass completely through insulation shield 340 so deeply.The degree of depth of groove 350 depends on the thickness and the material of insulation shield 340 to a great extent.No matter material type and thickness, at least some insulation-shield material should remain in the bottom of groove 350 so that groove 350 is separated with insulator layer 330.Preferably, the insulation-shield material of at least 1 mil remaines in the base portion place of groove 350.Especially, the thickness of the insulation shield 340 between the outer surface of the bottom of at least one groove 350 and insulator layer 330 should be about 1-15 mil.More specifically, the thickness of the insulation shield 340 between the outer surface of the bottom of at least one groove 350 and insulator layer 330 can be about 5-10 mil.
Paths of weakness 350 can have and the corresponding to any width of target that allows insulation shield to separate along the path.Preferably, groove 350 has the width in 1/2 inch to 1 inch the scope.
At least one paths of weakness 350 is being crossed the path on the direction of cable 300 length.As shown in Figure 3, paths of weakness 350 can be basically with the straight line of the parallel axes of cable 300.In spirit of the present invention, can use single groove or multiple-grooved 350, and a plurality of groove can the desired any circumferential distance of separated concrete application.In an example as shown in Figure 3, multiple-grooved 350 equidistantly separates around the circumference of cable 300.
Alternatively, as shown in Figure 4, paths of weakness 350 can form spiral with helicon mode roughly around insulation shield 340.Once more, if use multiple-grooved 350, can they be separated with the distance of any expection.In the example of Fig. 4, helicla flute 350 equidistantly separates around the circumference of insulation shield 340 basically.Can apply at least one helicla flute 350 among Fig. 4 at any angle.Spiral angle (A) can for example be determined by following formula:
Wherein:
A is a spiral angle;
W is the interval between the indentation;
D is the diameter of insulation shield; And
D is the degree of depth of indentation.
At least one paths of weakness 350 is preferably extended continuously along whole length of cable 350.Like this, groove 350 can be used to help to peel off insulation shield 340 at any some place along cable length, and this as discussed below.Yet groove 350 need not to cross whole length of cable 300, and does not need so continuously.For example, paths of weakness 350 can only be extended along a part of length of cable 300 at least.Equally, a series of groove 350 (not shown) that do not connect to each other can be arranged along the axis of cable 300 as a series of line segments at least one groove is provided in all points.
Though the embodiment that to have described wherein said at least one paths of weakness be groove or indentation alternately uses other mechanism of reduction insulation-shield material intensity within the scope of the invention.For example, drag-line (ripcord) or other releasing member (not shown) can embed in the insulator layer 340.When doing like this, should be noted that and guarantee that element embeds in the insulation shield 340.In the medium-pressure power cable between insulation shield and the insulator layer layout of material can cause the partial discharge that is harmful to.
One of drag-line may embodiment be the set of the high-tensile strength strength fibers in embedding basis material.The basis material that is fit to can be one of co-extrusion material described below.Optical fiber can be positioned in the insulation shield by means of compression tool during the cable extruding.
Other possibility of paths of weakness (not shown) can comprise band or other material with the insulation shield co-extrusion in the insulation shield 340.Explain more specifically that as following insulation shield applies via extruding usually.During this process, but intensity is not similar to insulation shield 340 can carries out co-extrusion with the material of insulator layer 330 compatibilities in paths of weakness.This material can comprise for example ethylene vinyl acetate of maleic anhydride modified (EVA), and ethylene vinyl acetate (EVA), ethylene-acrylate acetate (ethylene acrylate acetates) (EEA), the modifying copolymer composition of ethylene-propylene rubber (EPR), ethene acetic acid butadiene ester, EMA, chlorosulfonated polyethylene (CSPE) and polyethylene (PE).
By making it different, mean that the material in the paths of weakness has the material bond strength more greater or lesser than the material of insulation shield 340.As explained below, the difference of bond strength will help their separation between the material when the power that makes progress is applied to insulation shield 340.
When described at least one paths of weakness comprised more than one groove or indentation, it can be arranged as the several conditions in the judgment that satisfies those skilled in the art.For example, the material that helps to weaken can not mix with insulation shield 340, and is structurally stronger or more weak and do not stay the space than insulator.Alternatively, help the material that weakens to mix with insulation shield 340 and combine with it.In this case, this material can be mechanically remarkable more weak than insulation shield, is convenient to the trackman guard shield is separated.
Select as another, the material that helps to weaken can be mechanically significantly stronger than insulation shield 340, can mix maybe with insulator and can not mix.Material during this is arranged will be more near the conventional drag-line in the cable jacket on function.
In operation, cable 300 provides the enhancing structure that is used to peel off insulation shield 340 in joint or terminated cable.In strip cable 300, setter can remove shell 370 at first in a usual manner and concentric neutral elements 360 is pulled back with exposed insulator guard shield 340, shown in Fig. 2 A.At least one paths of weakness 350 in the insulation shield 340 provides and has been used for need not to split under the situation of special tool(s) and the groove of isolation insulator guard shield 340.
In the open air, the user can be by applying power, and for example the hand or with him installs, thereby next insulation shield being drawn back from cable assembly along paths of weakness removes insulation shield.By catch the part of insulation shield 340 at the place, end of cable 300, available manual force is drawn back guard shield from insulator layer 330.Usually, if they form by co-extrusion, the power of 3-24 pound is just separated these two layers.A part that outwards spurs guard shield 340 from insulator layer 330 will cause that guard shield is along at least one a plurality of part that separate in path 350 and formation is defined by for example described one or more groove.If wish fully to remove guard shield 340 from cable 300, single radially " annular " indentation can be in described part after insulator layer 330 optionally pulls back, in the position of expection, in guard shield 340 formation circumferentially on every side.Annular indentation can use any desired device to form, such as with conventional joining tool well known in the art.So setter can be with the standard mode of field operation by cutting and remove insulator layer 330 and conductor shield 320 continuous junction cables.
Preferably, paths of weakness, such as groove 350, but should so that can be used for the compatible mutually mode of the applicable industry standard that insulator removes (for example AEIC CS8-00, open-air fissility test) and be formed in the insulation shield 340.The parallel otch of two of this test requests be designed to the band parallel with cable axis remove the indentation instrument of insulation shield, (13 ± 1mm) spacing forms downwards towards insulator with 1/2 ± 1/32.The indentation instrument should be set at the degree of depth place that is no more than 1 mil (0.03mm), less than the specific specified minimum point thickness of insulation shield.This test does not need the pulling force measure.Insulation shield strip will be by drawing back insulation shield to remove from insulator with the speed of about per second 1/2 inch (13mm).Whole pulling is carried out to become about 90 ° angle with respect to cable axis.The total length of pulling is minimum 12 inches (300mm).In order to test by this, insulation shield should not torn or remove under the situation that stays residual conductive material on the insulator surface.
According to principle of the present invention, have the power cable that improves fissility and can follow several pressing steps and make.These steps can comprise provides the cable core that comprises at least one conducting element; around core, apply the semiconductive conductor shield; insulator layer is provided around conductor shield; around insulator layer, squeeze out insulation shield; around insulator layer, squeeze out insulation shield; length along cable is given paths of weakness in insulation shield, metal skirt is provided and squeezes out the outer protection shell around insulation shield.
As specializing here, the basic process that is used to form cable 300 is roughly described in the flow chart of Fig. 5.Provide the first step 510 of cable core to comprise the conventional process that forms electric conductor, may be by multiple conducting wires being twisted into conductor wire harness 310.Apply the semiconductive conductor shield in 520 steps around core, provide insulator layer in 530 steps, and squeeze out insulation shield in 540 steps around insulator layer, these all can relate to technology well known in the art.Can sequentially carry out each step 520,530 and 540.That is, conductor shield 320 can at first apply or be squeezed on the cable core 310, then applies insulator layer 330, and is the extruding of insulation shield 340 then.
Alternatively, step 520,530 and 540 one or more can the execution simultaneously.That is, conductor shield 320 and insulator layer 330 can carry out co-extrusion with the insulation shield 340 that is attached to above them.Alternatively, whole three floor 320,330 and 340 can use three road extrusion heads co-extrusion in single passage.
Giving paths of weakness 550 along the length of cable in insulation shield can relate to and use any conventional equipment to corrode in insulation shield 340 outsides or cut out the path.Preferably, one or more grooves or indentation can use one or more blades to make.Blade should produce indentation level and smooth and cleaning in insulation shield, simulation is the incision type that joint or termination were made between preparatory stage of carrying out by the user at cable in the open air.Razor-type blades is an example.In at least one embodiment, each blade should with predetermined width of nick set be provided with and locking in guide.Yet even when setting puts in place, blade also can flexibly be loaded in the device, so that allow cable because moving naturally of can occurring usually and vibrate caused certain and move in this indentation operation.
More specifically, indentation step 550 can relate to allows the local cable that forms pass a device, and blade is contained in the guide in this device, and this guide can be advanced along the outer surface of cable, guarantees the width of nick that obtains to expect.Blade on guide scalable to allow to be used for different cable dimension and different width of nick and types.
Fig. 6 A and 6B illustrate the exemplary means that is used to provide indentation insulator layer 340.In these were arranged, blade 610 and 620 should be maintained fixed when cable passes scratching device.In Fig. 6 A, two blade 610 and 620 positioned parallel are shown in 630.Fig. 6 B illustrates another embodiment, and paired herein blade 610 and 620 can be constructed at an angle to each other, shown in 640.In this angled orientation, blade is to minimize the mode indentation insulation shield of tearing 340 of groove 350 outboard shroud when the setter peeling guard shield.Directional angle among Fig. 6 B can be to make the groove 350 of the one or more surperficial perpendicular with insulation shield 340 of blade cuts.Though Fig. 6 A and 6B illustrate the orientation that comprises four blades, can use any amount of blade with any specific interval.In one example, blade 610 and 620 can be spaced apart about 0.5 inch.
The pre-scratching device that is used to produce helical scores will comprise one or more blades and guide, be similar to vertical scratching device.Yet, different with the fixed blade that is used for producing vertical indentation, the blade in the helical scores device can be when cable passes device around the circumference rotation of cable.As in vertical scratching device, the scalable blade is adapted to different cable dimension and width of nick.
Alternatively, the indentation on the insulator layer 340 obtains during its extruding.In other words, make insulating material pass membrane module, this membrane module provides the projection of suitably arranging, to form indentation on insulator layer 340.
Alternatively, the giving paths of weakness and can relate in insulation shield and be embedded in releasing layer or drag-line of 550 steps among Fig. 5 along the cable material that longitudinally co-extrusion is different with insulation shield or at guard shield.Compare with insulator layer when significantly stronger at material, such as drag-line, material can be positioned in the insulator by means of compression tool during the extruding of insulator, rather than passes through co-extrusion.
At last, in 560 steps of Fig. 5, metal skirt and shell provide to cable according to any technology known in the art.
By means of nonrestrictive example, two exemplary cable that are expressed as cable 1 and 2 prepare to have the insulation shield of extruding.Cable 1 is the stranded aluminium conductor cable of 1/C#1/0 AWG19 lead of 15kV grade.As well known in the art, 1/C represents single conductor cable, #1/0AWG represents the conductor size according to U.S.'s traverse survey standard (American Wire Gauge standards), and 19 expressions twist together the quantity with the lead that constitutes the 1/0 AWG conductor gross area.Cable 1 has the nominal insulation thickness of 175 mils, and expection reaches the insulation shield minimum thickness of 30 mils, and the actual insulation minimum thickness of 31 mils.
Cable 2 is stranded aluminium conductor cables of 1/C 1000kcm 61 leads of 25kV grade.Once more, 1/C represents single conductor cable, and 1000kcm represents that conductor size is 1,000 thousand circular mil (1,000,000 circular mil), and 61 individual conductor of 61 expressions is stranded.Cable 2 has the nominal insulation thickness of 260 mils, and expection reaches the insulation shield minimum thickness of 40 mils, and the actual insulation minimum thickness of 42 mils.
For each cable, two 1/2 inch longitudinal cut forms spaced apart 180 °.Each otch is formed perpendicular to insulation shield surface axis by the razor-type blades that latches into pre-scratching device.Cable 1 and 2 pre-indentations are to the degree of depth of measuring 2,5,7,10 and 15 mils from insulating surface.
The cable 1 and 2 of pre-indentation stands as AEIC CS8-00 and desired final electric the bearing and local discharge test of ICEA/ANSIS-94-649-2000, is that the insulation shield and the insulator underlying of electric (sound) reliably and pre-indentation kept good binding to guarantee cable.Two kinds of cables all satisfy the requirement of every kind of test.Cable 1 can bear the alternating current 5 minutes (35kV is 4 times of normal working voltage of relative ground connection) of 35kV, and under the 35kV alternating current less than 5 partial discharges of coulomb (pico-couloumb) slightly.Cable 2 can bear the alternating current 5 minutes (52kV is 4 times of normal working voltage of relative ground connection) of 52kV, and under the 52kV alternating current less than 5 slight coulomb partial discharges.
The cable 1 and 2 of pre-indentation stands the open-air fissility test according to AEIC CS8-00.For every kind of cable and every kind of predetermined score depth, the sample that takes out four 18 inches is used to peel off test.Each sample is carried out peeling off test twice.The total length minimum of pulling is 12 inches during each the test.
In order to carry out the fissility test, each cable flatly is placed and fixed into Instron tension test machine (Instron Tensile Testing Machine).The edge of pre-indentation is raised and be placed between two anchor clamps that are provided with perpendicular to horizontal sample to obtain and cable axis pulling at an angle of 90.Pulling speed is preset as 1/2 inch of per second.Spur at every turn up to band be removed at least 12 inches or in insulation shield the place except the line of rabbet joint occur tearing.
Following form has shown the result of fissility test.Various grooves or indentation be characterized by from their degree of depth of insulation shield surface and the bottom of groove and below distance between the insulator layer outer surface.Tear the separation that refers to the place of insulation shield in the path of groove or split.
Table I: cable 1: the open-air fissility test under the room temperature
| The vertical degree of depth (mil) of indentation/apart from the distance (mil) of insulator | 29/2 | 26/5 | 24/7 | 21/10 | 16/15 |
| The number of times of tearing in eight pulling tests | 0/8 | 0/8 | 2/8 | 6/8 | 8/8 |
Table II: cable 2: the open-air fissility test under the room temperature
| The vertical degree of depth (mil) of indentation/apart from the distance (mil) of insulator | 40/2 | 37/5 | 35/7 | 32/10 | 27/15 |
| The number of times of tearing in eight pulling tests | 0/8 | 0/8 | 2/8 | 5/8 | 8/8 |
These cables as cable 300 disclosed herein, provide the improvement structure that is used to improve the power cable fissility.Under the situation of insulation shield with at least one paths of weakness, this cable make setter can reduce to use specialist tools and reduce indentation or cutting below under the situation of danger of insulator layer preparation be used to engage or the cable of termination.
Considering that other embodiments of the invention are clearly to those skilled in the art under the present invention's explanation disclosed herein and the practice.Described explanation and example are intended to only to be considered as for example, and actual range of the present invention and spirit should be indicated by claims.
Claims (28)
1. power cable comprises:
At least one conducting element;
Be positioned in position to the outside, described at least one conducting element footpath and have the insulator layer of outer surface;
Surround insulator layer and contact the insulation shield of described outer surface, this insulation shield has along the length of cable and is configured to be convenient at least one paths of weakness that insulation shield is vertically peeled off; And
Surround the shell of insulation shield.
2. according to the cable of claim 1, also comprise the concentric neutral conductor that embeds in the shell.
3. according to the cable of claim 1, also comprise the conductor shield of surrounding described at least one conducting element.
4. according to the cable of claim 3, wherein insulator layer surrounds conductor shield.
5. according to the cable of claim 1, wherein insulation shield has the thickness of scope from 0.5 to 2mm in the place except at least one groove.
6. according to the cable of claim 1, wherein at least one paths of weakness is a groove.
7. according to the cable of claim 1, wherein the thickness of the insulation shield between the outer surface of the bottom of at least one groove and insulator layer is about 1-15 mil.
8. according to the cable of claim 7, wherein the thickness of the insulation shield between the outer surface of the bottom of at least one groove and insulator layer is about 2-10 mil.
9. according to the cable of claim 1, wherein at least one paths of weakness is extended continuously along whole length of cable.
10. according to the cable of claim 1, wherein at least one path be straight basically and with the parallel axes of cable.
11. according to the cable of claim 1, wherein at least one path is around the spiral basically of the axis of cable.
12. according to the cable of claim 11, wherein the path of spiral has the spiral angle A that is determined by following formula basically:
Wherein:
W is the interval between the indentation;
D is the diameter of insulation shield; And
D is the degree of depth more than one line of weakness.
13. according to the cable of claim 1, wherein at least one paths of weakness is a drag-line.
14. according to the cable of claim 1, wherein at least one paths of weakness is the releasing member that embeds in the insulation shield.
15. one kind is used to produce the method with the power cable that improves fissility, comprises:
At least one conducting element is provided;
In described at least one position to the outside, conducting element footpath, provide insulator layer;
Around insulator layer, squeeze out insulation shield;
Length along cable is given paths of weakness in insulation shield; And
Squeeze out and center on by the shell of the insulation shield of indentation.
16., also be included in described at least one conducting element and apply conductor shield on every side according to the method for claim 15.
17., wherein around conductor shield, provide insulator layer according to the method for claim 15.
18., wherein carry out applying conductor shield, insulator layer is provided and squeezes out insulation shield simultaneously by co-extrusion according to the method for claim 15.
19., wherein carry out in insulation shield, giving paths of weakness along whole length of cable according to the method for claim 15.
20., wherein in insulation shield, give paths of weakness and be included in above the insulator layer radially the insulation shield indentation to the about degree of depth of 1-15 mil according to the method for claim 15.
21., wherein in insulation shield, give paths of weakness and be included in above the insulator layer radially the insulation shield indentation to the about degree of depth of 2-10 mil according to the method for claim 15.
22. according to the method for claim 15, wherein in insulation shield, give before the extruding that paths of weakness is included in shell, cable longitudinally moved through to be positioned cut at least one blade in the insulation shield outer surface.
23. according to the method for claim 22, wherein said at least one blade comprises two blades of substantially parallel layout each other.
24. according to the method for claim 22, wherein said at least one blade comprises two blades arranging at an angle to each other.
25., wherein in insulation shield, give paths of weakness and also comprise described at least one blade of circumference rotation that centers on insulation shield according to the method for claim 22.
26., wherein in insulation shield, give paths of weakness and comprise that the extruded insulator guard shield passes the membrane module that comprises projection according to the method for claim 15.
27., wherein give at least one paths of weakness and comprise the material that is different from insulation shield along at least one path co-extrusion according to the method for claim 15.
28., wherein give at least one paths of weakness and comprise drag-line is imparted in the insulation shield according to the method for claim 15.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2006800554152A CN101501788A (en) | 2006-06-26 | 2006-06-26 | Electrical power cable with frangible insulation shield |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2006800554152A CN101501788A (en) | 2006-06-26 | 2006-06-26 | Electrical power cable with frangible insulation shield |
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| Publication Number | Publication Date |
|---|---|
| CN101501788A true CN101501788A (en) | 2009-08-05 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2006800554152A Pending CN101501788A (en) | 2006-06-26 | 2006-06-26 | Electrical power cable with frangible insulation shield |
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| Country | Link |
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| CN (1) | CN101501788A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103971799A (en) * | 2014-05-26 | 2014-08-06 | 龚利芬 | Insulated conductive band with improved structure |
| CN106057328A (en) * | 2016-06-17 | 2016-10-26 | 方倩 | Simple cable with heat-insulating protective cover and assembly and installation method of cable |
| CN108068727A (en) * | 2016-12-30 | 2018-05-25 | 德尔福中央电气（上海）有限公司 | It is a kind of high to press to wear cylinder connector |
-
2006
- 2006-06-26 CN CNA2006800554152A patent/CN101501788A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103971799A (en) * | 2014-05-26 | 2014-08-06 | 龚利芬 | Insulated conductive band with improved structure |
| CN106057328A (en) * | 2016-06-17 | 2016-10-26 | 方倩 | Simple cable with heat-insulating protective cover and assembly and installation method of cable |
| CN108068727A (en) * | 2016-12-30 | 2018-05-25 | 德尔福中央电气（上海）有限公司 | It is a kind of high to press to wear cylinder connector |
| CN108068727B (en) * | 2016-12-30 | 2024-01-16 | 安波福中央电气（上海）有限公司 | High-pressure through-cylinder connector |
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Open date: 20090805 |