GB2348056A - Connecting a branch cable to a live power cable - Google Patents

Abstract

The connector allows a branch cable 32, already connected to a load, to be connected to a live main cable. The connector body (4, Fig 1) is clamped around the two cables, and the insulation around the main cable is pierced. A movable conductor 42 is at first held away from the branch cable. A threaded bolt 46 is then rotated until the head 56 shears off, at which point a spring 48 quickly pushes the conductor 42 into contact with the core 34 of the branch cable. Because the connection is made quickly, little arcing occurs. Insulation piercing teeth 28 may be used to create a more robust connection later. Instead of a spring 48, other propelling means can be used, for example an explosion, compressed gas or a hammer.

Description

CONNECTOR ASSEMBLY FOR INTERCONNECTING A POWER CABLE UNDER LOAD This invention relates to an electrical connector assembly for use in the electrical power transmission industry, and, more particularly, to an assembly for interconnecting power cables under load.

In certain applications, branch cables are interconnected to live main power cables, the branch cable supplying power to an electrical load such as machinery, a factory, or other electrical networks. The current to be drawn by the electrical load is unknown until connection is established. Large electrical current loads during the termination of a connector to the main and branch cables may cause eleczric arcing.

Interconnection of live cables under current loads requires cumbersome safety measures and may lead to some impairment of the connector thereby reducing the performance and reliability of thé interconnection. A conventional method of interconnecting a load to a live cabie is to scrin sections of the branch and main cable thereby exposing the inner conducting cores thereof, and tt en conductive clamping jaws of a clamping connector onto the exposed cable cores. The operators manipulating the ! e connection need to takespecial care and perform the clamping connection fairly quickly to reduce arcing.

It is an object of this invention to provide a connector assembly that proves the safety and ease o handling in terminating a cable connected to an electrical load, to a live power supply cable.

Objects of this invention have been achieved y providing the connector assembly according to claim 1.

Disclosed herein is a connector assembly cor interconnecting a branch cable of an electrical load ec a main cable supplied with electrical pcwer, eh~ assembly including a branch cable bridging'assembly having a connector portion with a terminal for contacting the inner conducting core of the branch cable, the bridging assembly further comprising an electrical bridging device, the device having a moveable con conductor elementandafixedconductorportion,the moveable conductor element retainable in a first position insulatively separated from the branch cable conducting core, the device having means to propel the moveable conductor element to a second position in contact with the branch cable conducting core. A rapin electrical connection to the branch cable conductina core is thus established. The bridging assembly may De permanently connected to the cable by terminating the connector portion to the cable after the bridging device is actuated. The rapid interconnection of the bridging device prior to termination of the connector portion reduces or eliminates arcing thus creating a safer termination, The connector portion of the bridging assembly may advantageously comprise insulation piercing contacts that pierce through the outer insulating layer or the branch cable during clamping of the cable thereagainst by clamping members in the form of bolts. The connect-or may be covered in an insuiacing layer such that here are na exposed conductive surfaces on the outside of che connector icrx particularly safe operation. The bridging interconnection enables the insulation piercing connection to be effectedwithouttheproblemofarcing between the insulation piercing teeth of the connector portion and the cable conducting core. If arcing ere cc occur, the insulation piercing tips may significantly deteriorate by the welding effect of arcing, thereby rendering the insulation plercing connection particularly unreliable.

The bridging device may extend from a longitudinal end of the connector portion in substantially the same direction of the branch cable. The device may extend from an end of the connector portion opposed to the end in which the cable is introduced in the connector portion. The bridging assembly moveable conductor may be in the form of a projectile that is propelledbya spring, compressed gas, or other means such as a smalt explosive charge. The moveable conductor may be held in the first position by a retention member in the form oc a bolt or screw with a shearabie head. Upon turning the bolt the head snears and a pre-stressed spring projects the moveable conductor into electrical connection with the branch cable. The outer conductor portion of the bridging assembly may entend in the form or a tube or rod recevable between clamping ja. ws of conventional insulation piercing contact (IPC) connector.

In order to effect electrical connection between the main and branch cable, the main cable and the bridging assembly outer conductor are receive : between jaws of the IPC connector, the jaws being tighteied together to clamp and pierce through the outer insulating layers such that the main cable is electricallyinterconnectedtoc.heoutercond'.t.ctord the bridging assembly. A branch cable is received in the bridging assembly connector portion. Subsequently, the bridging devic. e is actuated, for example by shearing the retention bolt head, such that the inner conductor is propelled against the end of the branch cabine, Temporary electrical connection is made from the branch cable through the moveable conductortotheouterconductorc: the bridging assembly and therefore to the main cable via the IPC connector. The temporary connection is designed to withstand the electrical current load for ac least a few minutes to allow the bridging assembly connector portion to be clamped and permanently interconnectedtcthebranchcabi,frexampleby- interconnected to the branch cable, for example by tightening clamping bolts thereof that press the branch cable into the insulation piercing contacts of the connector portion. The retention boit-ouf the bridging device may be made of an insulative material such hac the device is insulated and enables safe operation under live conditions. The bridging assembly connector portion may comprise a longitudinal cavity for receiving the end of the branch cable therein, whereby an insulative stopper at an end of the cavity from which the bridging device extends, positions the branch cable end wich respect to the bridging device.

An embodiment of this invention will now be described by way of example with reference to the accompanying drawings in which ; Figure 1 is a perspective view of a connector assembly and a bridging assembly according to this invention; Figure 2 is a view cowards a cable receivingedci the he bridging assembly ; Figure 3 is a cross-sectional view through line 3-2 cf figure 2 ; Figure 4 is a cross-sectional view throug-hline4-4 o ficfure 2 (without branch cable) : Figure 5 is a perspective view cowards a bridging device end ot the bridging assemble ; Figure 6 is a perspective view towards cabre receiving end of the bridging assembly with cut-away portions to see the interior thereof.

Referring to the figures, particularly figure 1, a connectorassembly2ccmprisccaninsulationpi.; rcLgcontact(IPC)connector4andanelectricalload contact (IPC) connector 4 and an electrical load bridging assembly 6. The IPC connector 4 may be a conventional IPC connector comprising a pair of clamping jaws 7,8 that may be tightened together by a shearable bolt 10 Each connector jaws 7,8 comprises terminals with insulation piercing contacts at either end of each terminal for piercing through the outer insulation of respective first and second cables or conductors received in the first and second positions 5 respectively of the connector. Interconnection between insulated conductors can thus be established by placing the conductors in respective positions 11, 12 and subsequently tightening the bolt 10 to clamp the connector jaws 8, 7 together. IPC connectors are however not conventionally employed for interconnecting a live cable to a cable connected to a large electrical load, because arcing during the insulation piercing may damage the cable insulation and/or weld the insulation piercing tips of the terminas prior to complete connection- Deterioration of the insulation piercing contacts and insulation or the conductors may impair the performance of the interconnection. The provision of the bridging assembly 6 according to this einvention enables the use of a connector assembly with an IPC or other type of connector under safe conditions for repliable interconnection.

The bridging assembly 6 comprises a conneccor portion 14 and a bridging device 16. The connector portion 14 comprises a housing 18, an electrical terminal 20, an actuator 22 in the form of clamping bolts 23, and an outer insulating layer 26. The terminal 20 has insulation piercing contact (IPC) teeth 28 projecting into a cable receiving cavity 30 of the connector and arranged opposed to the clamping bolts23.

A branch cable 32 having an outer insulating layer33 and an inner conducting core 34 may be inserted into the cavity 30 until an end 35 of the cable abuts an end 3c of the cavity defined by an insulative insert 38.

As best seen in figures 2 and 3, the cavity 30 ils shaped and adapted to receive the cable 32 such that che clamping bolts 23 can clamp the cable against rhe IPC teeth 28 such that the teeth pierce through the curer insulting layer 33 and contact the inner core 34. Secure electrical connection may thus be established between the cable 32 and terminal 20.

The bridging device 16 comprises a static conductor portion 40, a moveable conductor 42, and an actuator mechanism 44 to propel the moveable conductor towards the end 35 of the branch cable. The actuator mechanism comprises a shearable bolt 4s and a spring 48. The static conductor portion 40 is electrically connected to the terminal 20 of the connector portion, and in this embodiment the terminal 20 and conductor portion 40 are formed from an integral piece of metal which is secoure^ partially within the housing 18 of. the connector- . ; The static conductor portion 40 of the bridging device 16 comprises a substantially tubular section within which is slideably received the moveable conductor 42. The outer insulating layer 26 or Xlle connector portion also extends over the static conductor portion 40 of the bridging device 16 such that the whole assembly 6 is insulated and can be safely handled under live conditions.

As best seen in figure 3, the moveable conductor 41 is held in a pre-assembly or retracted position where a cable connection end 48 thereof is spaced from the insulator end 36 and thus from the cable end 35. The spring 48 which is in the form oE a coil spring, is compressed between the moveable terminal 42 and a shoulder 50 at an outer end 52 of the static conductor portion 40. The bolt 46 threadably engages in a corresponding threaded bore 54 in the mcveable conductor 42, and when rotated clockwise draws the moveable conductor 42 towards the outer end 52. Once the compression spring 48 is completely compressed such chat the spires touch each other, the bolt head 56 shears at the shank 57 thereby releasing the moveable conductor 42. The compressed spring 48 propels the moveable conductor 42 towards the cable end 3 such thai ic pierces or butts against the cable conducting core 34. A temporary electrical connection is thus established between the cable and terminal 20 via the moveable conductor 42 through the static conductor 40. The moveable conductor42 is slideably received in the bore 55 of the static conductor 40 in a close but sliding fit such that electrical contact therebetween is established. Electrical connection is also established between the moveable conductor and static conductor through the coil spring 43. If desired, electrical contact between the moveable conductor and static conductor may be improved by inserting leaf spring contacts between the moveable conductor 42 and the bore 55.

The screw 46 is made from an ir. sulating material such as a plastic based material. The bolt head 56 may be engaged by a standard tool such as a screwdriver that fits into the slot 59.

While in the above described embodiment the moveable conductor 42 is propelled by a spring 48, it is possible to propel the moveable contact by a gas discharge, for example a smail discharge from a explosive device or a compressed gas canister. Another possibility to drive the moveable conductor wouid be co engage the actuator with a hammer. In the above examples, the moveable conductor 42 is projected sufficiently rapidly to establish electrical connection between the cable and terminal 20 without substantial arcing problems. In addition, any arcing between = : se moveable conductor 42 and the cable core 34 doesnot have any adverse effect on the final interconnection, as the bridging device 16 only serves to effect a temporary electrical interconnection between the cable and static conductor portion.

In order to establish an electrical connection between a live cable and a branch cable connected to an electrical load, the main cable is position betweer. the connector jaws 7, 8 in the second position 12, ana the static conductor 40 of the bridging assembly 6 is position between the jaws 7, 8 in the first position 11. The connector 4 is then cerminaced to the bridging assembly and cable by clamping the jaws 7, 8 with tne bolt 10. At this stage, the insulation piercing contacts of the connector 4 have establishedcontactwithhe inner conducting core or the main cable and wi. n cre static conductor 40 (having pierced through crue insulation layer 26 therearound). The branch cable is inserted in the connector portion cavity 30 until the end 35 thereof abuts the insulating end 36. Subsequently the bridging actuator 56 is actuated to propel the moveable conductor 42. In this embodiment, the bolt head 56 is rotated until the shank 57 shears and releases the moveable conductor 42 which is propelled by the spring 48 into electrical contact with the end 35 of the cable e conducting core 34. Temporarily electrical connection is established between the main and branch cables via the moveable conductor 42. The branch cable may then be securely terminated to the bridging assembly. In this embodiment, the shear bolts 23 are threaded to clamp the cable 32 against the insulation piercing teeth 28.

The temporary interconnection through the moveable conductor 42 ensures that as the branch cable 32 is pierced by the teeth 28, no arcingoccurstherebetweenA safe and reliable electrical connection is thus achieved-

Claims (2)

1. CLAIMS 1. A connector assembly for interconnecting a branch cable, connected to an electrical load, to a main cable supplied with electrical power, the assembly including a bridging assembly having a connector portion for terminating the branch cable, the connector portion comprising an electrical bridging device, the bridging device having a moveable conductor and a fixed conductor portion, the moveable conductor being retainable in a first position insulatively separated from the branch cable, and the bridging device having means to propel the moveable conductor into contact with a conducting core of the branch cable.
2. 2. A connector assembly constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings,