Abstract:
An electrical connector and method of making the electrical connection are disclosed for use in particularly arduous conditions, such as down hole oil production applications. The invention provides high electrical integrity with an ability to accommodate steady and/or fluctuating mechanical forces placed via the cable into the connector. Synergy between the mechanical and electrical aspects of the design is taught in which an insulating member, fitted with annular upstands, co-operates with a mechanically soft, essentially incompressible, insulating substance (gel) to cause vibrations in the cable to be dissipated over a length of the insulated cores inside the connector rather that at a single point where it would cause the core to fracture. In addition, annular collars of the gel are provided between the insulating member and the crimped pin-core connections and between the annular upstands and insulated cores to give further cushioning. Because the core insulation sits deep inside the annular upstand of the insulating member and gel collars, this creates a good electrical interface with a long creepage distance. The method covers the creation of the gel collars, alignment of contact pins and insulated cores and assembly of the connector.

Description:
BACKGROUND OF THE INVENTION 
   This specification relates to electrical connectors which have to carry very high powers in compact spaces in hostile environments and covers both the connector design and method of assembling it in the field. 
   The oil production industry has to contend with some of the most inhospitable conditions anywhere. These include wide temperature variations, e.g. −40° C. (storage of equipment in Alaska) to +120° C. (downhole), thermal shock, high pressures and highly corrosive, abrasive environments. A further, and frequently major, factor is mechanical shock and fatigue due, particularly, to vibration caused by fluid flow past the connector. A typical installation is shown in  FIG. 1  where wellhead  1  is shown on seabed  2 . Hole liner  4  is suspended from tubing hangar  3  and supports a number of items, e.g. electrical submersible pump (ESP)  5 , which is powered via protected cable  6 . A key item is the motor lead extension (MSE) connector  7 , which is sometimes known as a ‘pothead’. 
   This specification deals particularly with connectors  7  such as this, which are inaccessible once in position and have to last, at least, for the lifetime of pump  5 . 
   Previous experience with currently available connectors  7  has been unsatisfactory as the factory made units often suffer from problems relating to temperature variations, and the resultant mechanical stresses generated and electrical failure due to movement of the contacts under thermal, or operating pressure, effects. One particular problem is vibration, induced by the high flow rate of oil and/or gas in liner  4 . Another factor is that cable  6  must be cut to the exact length so that there is a minimum of free cable as slackness can result in cable damage due to fretting and/or impacts as the cable whips around in liner  4 . High frequency vibrations, even though of only small amplitude, can, over a period of time, have a significantly damaging effect on a cable, e.g. fatigue, chafing of insulation, etc. 
   Cable  6  is attached to connector  7  and it is this which effectively has to provide the ‘reaction’ to these vibrations. Thus, the cores inside connector  7  are subject to high frequency, cyclical, axial and bending forces. The effect of these forces is to weaken the connection both mechanically and electrically and, usually, lead to premature electrical failure, with consequent serious loss of production. 
   As explained, the connector provides the ‘mechanical reaction’, i.e. acting in a pin-jointed or encastrè capacity. Some current connectors use a multiple metal-rubber disc compressed sandwich to form the seal. This can leak due to the effects of thermal cycling and set when the rubber does not fully recover its previous size on cooling (in operating practice, it is common to have to shut down the well, either for downhole maintenance or for work on the seabed or surface equipment; this allows cycling from 100+° to 4° C. {sealed temperature} and back.) Here the reaction point is where the conductor enters the crimped or soldered joint. In others, moulded rubber is used and here the reaction point is where the insulated core enters the rubber insulator. Clearly, there is a need to spread the reaction over as long an axial length as possible to minimise fatigue effects. 
   Current practice is for cables  6  and connectors  7  to be factory assembled in fixed lengths, often 16.76 m (55 ft). Though means-to shorten cables, e.g. by coiling, etc., are known, space is extremely limited in liner  4  and wellhead  1 . Furthermore, cable  6  is armoured and not easily bent. Additionally sharp bends place unnecessary stresses in the cable. 
   There is thus a need for a high powered, precision-made electrical connector which can be assembled on site, quickly and reliably and to exact lengths, preferably by semi-skilled personnel. Preferably, such connectors should be able to accommodate external forces placed on them without deterioration. 
   SUMMARY OF THE INVENTION 
   According to the invention, there is provided an electrical connector connecting a cable to a powered item/further connector comprising;
         i) a multicored, insulated electrical cable;   ii) electrical connections securing individual cores to individual contact pins;   iii) individual contact pins positively engageable within an insulating member;   iv) a flexible boot, defining, with the insulating member, an interior which is filled with a mechanically soft, essentially incompressible, electrically insulating substance;   v) a housing providing a seal with the insulating member and also with the powered item/further connector; and   vi) a clamp able to grip and secure the electrical cable into the housing;   wherein annular channels are provided between the insulating member and the contact pins, the mechanically soft, essentially incompressible, electrically insulating substance forming cushioning in the annular channels, the connector being arranged so that, when assembled, where external forces are placed on the connector via the cable, they are dissipated progressively over an extended length of the insulated portions of the cores inside the connector and where the ends of the contact pins not secured to the cable cores are connectable to the powered item/further connector.       

   According to a first variation of the apparatus of the invention, the annular channels are in communication with the interior. 
   According to a second variation of the apparatus of the invention, the individual cores are secured to contact pins by crimping. 
   According to a third variation of the apparatus of the invention, circlips provide the positive engagement for the individual contact pins within the insulating member and O-rings provide sealing to exclude the operating environment from the area of the electrical connections. 
   According to a fourth variation of the apparatus of the invention, the insulating member is provided with annular upstands around the individual electrical conductors as they enter the insulating member. 
   According to a fifth variation of the apparatus of the invention, the annular upstands around the individual electrical conductors as they enter the insulating member are cylindrical in form. 
   According to a sixth variation of the apparatus of the invention, the mechanically soft, essentially incompressible, electrically insulating substance is cast in position as a liquid and subsequently polymerised. 
   According to a seventh variation of the apparatus of the invention, the mechanically soft, essentially incompressible, electrically insulating substance is cast in position in a way to avoid incorporation of air bubbles. 
   According to an eighth variation of the apparatus of the invention, annular channels are also provided between parts of the insulating member and the insulation of said insulated portions of the cores, the mechanically soft, essentially incompressible, electrically insulating substance forming cushioning in those annular channels. 
   According to a ninth variation of the apparatus of the invention, the annular channels provided between parts of the insulating member and the insulated cores are right cylindrical in form. 
   According to a tenth variation of the apparatus of the invention, the annular channels provided between parts of the insulating member and the insulated cores are in the form of conical cylinders. 
   According to an eleventh variation of the apparatus of the invention, the mechanically soft, essentially incompressible, electrically insulating substance is cast in position as part of the pre-assembly stages. 
   According to a twelfth variation of the apparatus of the invention, a forming tool is provided for use in the pre-assembly stages to fill the flexible boot with mechanically soft, essentially incompressible, electrically insulating substance. 
   According to a thirteenth variation of the apparatus of the invention, jigs and/or tools are provided for use in the final stages of assembly-to prepare the cable insulation prior to crimping and to align the contact pins and insulated cores for fitting into the insulating member. 
   According to the invention, there is disclosed a method of making an electrical connection comprising the steps of:
         i) providing the components for the connection;   ii) fitting a flexible boot over an insulating member,   iii) filling the void inside the boot with a mechanically soft, essentially incompressible, electrically insulating substance in such a way that space is provided for contact pins and insulated cores to be fitted at a subsequent time;   iv) fitting the filled insulating member-boot sub-assembly into the housing and creating a seal between the sub-assembly and the housing;   v) tag a multicored electrical cable and cutting to length;   vi) placing the cable grip over the cable;   vii) preparing an appropriate length of insulation on each conductor and baring the requisite length of each core;   viii) inserting each bared conductor into a prepared part of a contact pin and securing in position;   ix) bending the conductor-pin assemblies to align the conductors and pins to fit the spaces provided in the boot and mechanically soft, essentially incompressible, electrically insulating substance and insulating member,   x) inserting each contact pin and connector sub-assembly through holes in the boot, through passages in the mechanically soft, essentially incompressible, electrically insulating substance and into the insulating member;   xi) causing the contact pins to engage positively with the insulating member and form a seal with the insulating member; and   xii) securing the cable clamp.       

   According to a first variation of the method of the invention, a hand tool is provided to define the passages for the insulated cores in order to fill the boot with a mechanically soft, essentially incompressible, electrically insulating substance. 
   According to a second variation of the method of the invention, the mechanically soft, essentially incompressible, electrically insulating substance is placed inside the flexible boot using a syringe. 
   According to a third variation of the method of the invention, a hand operated tool is provided to prepare the insulation on the conductors and cut and remove insulation to expose the correct length of cores. 
   According to a fourth variation of the method of the invention, a template is provided to align the contact pins and conductors to fit the insulating member. 
   In a preferred example, the cable ending connector is partly pre-prepared before supply. The steps are fitting the flexible boot to the insulating member and filling the boot with a mechanically soft, essentially incompressible, electrically insulating substance. A forming tool is used to define the passages through which the pin and conductor assemblies will pass into the insulating member. The substance is preferably introduced as a monomer and hardener mixture in a way to avoid the incorporation of air bubbles into the liquid, e.g. using a syringe stuck through the boot. As the inviscid liquid flows in, the assembly is rotated and tilted so that the liquid fills every part of the boot, including channels between parts of the forming tool and upstands on the insulating member. When full, the polymer mixture inside the insulator boot assembly is polymerised, e.g. by placing in a warm oven for a period of time. 
   Internal circlips are placed into the bores of the insulating member where the contact pins will fit. The insulator-boot assembly is fitted into the housing with its O-ring seal. O-rings are also fitted to the contact pins, which are bagged to maintain cleanliness. The separate items, as described including cable clamp, are supplied to the client 
   On site, the assembler cuts the cable to length so that it has a square end. Armoured cables, are usually used for down hole applications in the oil industry. The armouring is removed and the insulation on the conductors prepared, preferably using special tools provided. The cable clamp is placed over the cable. A further tool is used to prepare the insulation on the cores and expose the requisite lengths of cores. A contact pin secured to each core. Crimping is preferred as it is a less critical operation than, say, soldering and so a semiskilled person would be less likely to produce a suspect connection. 
   A jig is provided to align the crimped contact pins and conductors so that they can be inserted into the insulator-boot assembly through an aperture in the housing. The aligned contact pins and insulated conductors are sprayed with a lubricant so that they pass through the mechanically soft, essentially incompressible, electrically insulating polymer into the insulating member. The pins positively engage with the circlips, previously placed in the insulating member and the O-rings form a seal. The final stage is to fit the cable clamp which also closes the aperture in the housing. 
   A key advantage of this form of assembly is that a highly developed electrically and mechanically designed connector will be fitted correctly because the critical operations are performed by the manufacturer and the final assembly, which of necessity must be performed on site, is reduced to a series of simple operations by the use of specially provided jigs and tools. Clearly, critical operations could be performed on site by a skilled person but this relies on him/her being available at the particular time to perform these operations and having the required facilities to hand. As this connector is designed for a critical application, production cannot be jeopardised by the risk of a poorly made connection 
   Preferably the mechanical and electrical design incorporates annular upstands surrounding the insulated cores as they enter the insulating member. Between these annular upstands and the insulated cores are channels filled with the mechanically soft, essentially incompressible, electrically insulating substance. The form of these upstands and channels are essentially cylindrical and may be right cylinders, conical cylinders, or any combination of these forms. A further channel may be provided between the insulating member and the crimped portion of core-pin connection. The interactive design of the annular upstands and filled channels provides both an optimal electrical environment to accommodate the passage of electrical current from cable to contact pins as well as an ideal mechanical design to dissipate vibration, flexure and other mechanical forces in the cable which are applied to the connector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a clearer understanding of the invention and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which: 
       FIG. 1  is a diagrammatic section of a sub-sea wellhead and hole liner (Prior Art); 
       FIG. 2  is a sectional side elevation of an assembled connector according to the invention; 
       FIG. 3  is a plan view of the connector shown in  FIG. 2 ; 
       FIG. 4  is a sectional end elevation of the connector shown in  FIG. 2  along the line AA; 
       FIG. 5  is an enlarged par sectional side elevation of the connector shown in  FIG. 2 ; 
       FIG. 6  is a part sectional elevation of a boot gel-filling tool of the invention; 
       FIG. 7  is an end elevation of the boot gel filling tool shown in  FIG. 6  looking in thee direction of arrow B; 
       FIG. 8  is a sectional elevation of a core stripping tool of the invention; 
       FIG. 9  is an end elevation of the core stripping tool shown in  FIG. 8 ; 
       FIG. 10  is a plan view of a core bending tool of the invention, including core a template; 
       FIG. 11  is a side elevation of the core bending tool of  FIG. 10 ; and 
       FIG. 12  is a side elevation of a core bending tool of the invention without a core template. 
   

   DESCRIPTION OF THE INVENTION 
   In the following description, the same reference numeral is used for identical components or different components fulfilling an identical function. 
   The connector A will be described firstly in the assembled condition, to give an overall understanding, and then the method of assembly will be explained in detail. 
     FIGS. 2 and 5  show armoured cable  6  passing into cable connector A. The particular connector shown has three pins  12  arranged in a triangle to match the socket  7  on ESP  5  (FIG.  1 ). 
   Armoured cable  6  passes through cable clamp  24  into connector housing  8 . Beyond clamp  24 , the armouring  6  is cut to reveal the lead sheathed conductors  9  which pass through collars  27  in flexible boot  23 . Lead sheathing  9  is removed beyond the end of collar  27  to reveal insulation  10 . The final section of insulation  10  is removed to reveal core  13  which is crimped in the annular space  14  in the end of contact pin  12 . Drilling  15  is provided to view the end of core  13  to ensure that is in position before crimping. 
   Pin  12  is located positively by circlip  17  in metal sleeve  18  fist with insulator  11 . Circlip  17  is essential to provide axial location of pin  12  but its presence generates high localised electrical stress concentrations. Metal sleeve  18  is an important feature as it dissipates these electrical stress concentrations and thus protects insulator  11 . Collar  21  is an integral feature of insulator  11 , mechanically and electrically supporting sleeve  18  whose annular nose  18 A passes the electrical stresses smoothly into pins  1 . O-rings  16  separate the insulating oil  47  from crimped joint  13 ,  14 . Cavities  19  are provided to assist in ensuring uniform electrical insulating throughout insulator  11 . 
   Flexible boot  23  covers the insulator  11  and crimped connections  13 ,  14  of each conductor. Boot  23  is secured to insulator  11  via ridge  29  engaging in annular groove  30 . The space inside boot  23  is filled with a mechanically soft, essentially incompressible, electrically insulating substance  28 , hereinafter referred to as a “gel.” 
   The purpose of this gel  28  is both to provide electrical insulation and mechanical support for the insulated conductors  10  adjacent to the crimpled connection  13 ,  14 . Annular collars  28 B and  28 A of gel are provided between annulus  14  and insulator body  11  and between insulated core  10  and insulator collar  20  respectively. The design of tapering collar  20  provides gradually increasing flexibility to bending with increasing distance from crimped joint  13 ,  14  so that external loads, applied via cable  6 , cause progressive deflection along the whole length of insulated core  10  inside boot  23  rather than a sharp bend at a single point. Gel collars  28 B and  28 A contribute significantly to this aspect of the design. 
   The forms of insulating collars  20  and gel collars  28 A and  28 B are basically cylindrical but may be right cylinders or conical cylinders, or any combination of these forms. The combination of collars  20 ,  28 A and  28 B act together to support to the insulated cores inside boot  23  in a progressively cushioned manner. This minimises the reactions required from crimped joint  13 ,  14  and is important to guaranteeing the operating life of the connector A. 
   Of great importance is that the core insulation  10  sits deep inside the upstand of insulator collars  20  and gel collars  28 A to create a good electrical interface with a long creepage distance. This is to accommodate the potential difference o, for example, 3000V at crimp  14  to earth on lead sheath  9 . As gel  28  is filled at normal atmospheric pressure, the increased operating pressure will act to compress gel  28  into collars  28 A and  28 B, thus ensuring maximum electrical insulation. 
   Gel  28  also cushions cores  10  against changes in external pressure or rough handling of the connector A and cable  6 . This is important as, in the extreme conditions in which the connectors operate and the very high levels of power being carried, any minor deviation from the insulation specification can lead to high electrical stresses, possible arcing and eventual failure. It is to address such failures that the connector of the invention has been devised and the attention to such details ( 20 ,  28 A and  28 B) is necessary to be able to guarantee that the operational life of connector  7  will exceed that of pump  5 . 
   It is common to drill for oil in water over 1000 m deep where the pressure is over 100 atmospheres. The application of such pressure to boot  23  causes substance  28 ,  28 A,  28 B to ‘flow’, e.g. to compact into annuli  28 A and  28 B. A range of electrical insulators are suitable for gel  28 , such as natural rubber, a soft resilient polymer, etc. A particularly preferred gel is a two part mixture of fluorosilicone. 
   A circlip  22  and co-operating shoulders  31  locate insulator  11  axially within housing  8 . Cable  6  is secured in cable clamp  24  by two grub screws  25  which also lock clamp  24  axially in housing  8 . This ensures that axial forces applied to cable  6  do not affect crimping  13 ,  14  or the engagement of pins  12  in their sockets (not shown). A protective transit cover  46 , sealed with O-ring  48 , is shown attached by bolts  49  to housing  8 . When the connection  7  is made to ESP  5 , bolts  49  and seal  48  are re-used. The void  47  inside connection  7  will be filled with electrically insulating oil and provided with pressure compensation from the motor head (not shown). 
   The connector just described is a precision item which, when made to ESP  5 , will keep the medium in which pump  5  and connection  7  are operating out of the connector internals, irrespective of changes in external pressure. The dimensions and materials of construction of sleeves  18 , collars  18 A and insulator  11 , including collars  20  and  21 , have been carefully designed to minimise electrical stresses between the contact pins  12  (including annulus  14 ) and core insulation  10 . As explained before, mechanical support for cores  10  is an integral part of the overall design. 
   The details of the assembly of connector A will now be described. 
   A number of special tools are provided to enable the connector A to be fitted. One of these, the Gel Filling Tool B (FIGS.  6  and  7 ), is used by the manufacturer but the rest are used on site. This procedure eliminates the need for precision workshop processes on site so that semi-skilled personnel can perform final assembly and yet produce a guaranteed precision connector. The principle of the procedure is: 
   Factory Assembly Processes:
         i) Fitting boot  23  to insulator  11  and filling with gel  28  (special tool B);   ii) Placing circlips  17  into grooves  32  in sleeves  18 ;   iii) Fitting insulator-boot assembly into housing  8 ;   iv) Fitting seals  16  to pins  12 ; and   v) Packing in sealed containers for delivery.       

   Site Assembly Processes:
         i) Preparing cable, i.e.
           Stripping armoured protection  6 ;   Preparing and removing predetermined lengths of lead sheathing (special tool C);   Stripping predetermined lengths of insulation  10  to expose cores  13 ;   Crimping exposed cores  13  into annulus  14  of contact pin  12  (special tool—not shown); and   Bending to align the three cores to fit insulator-boot assembly (special tools and template D &amp; E)   
           ii) Fit pins-conductors assembly through housing  8  into boot-insulator and ensuring positive engagement  17  and sealing  16 ; and   iii) Securing cable clamp  24  to housing  8 .       

   Factory pre-assembly starts with fitting boot  23  to insulator  11  by engaging ridge  29  into groove  30 . (Metal sleeves  18  are bonded to insulator  11  when the insulator is made, e.g. by a polymerisation process.) The gel filling tool B ( FIGS. 6 &amp; 7 ) consists of a handle  42  to which three pin formers  40  are secured  43 . Pin formers  40  pass through collars  27  of boot  23 . The section of pin former  40  inside boot  23  carries a sleeve  41 . Parts of sleeve  41  are carefully profiled with some sections  41 A to the full size of insulated core  10  and other sections  41 B undersized, compared to that of insulated core  10  and contact pin  14 . The undersized sections will allow gel annuli  28 A and  28 B to be created. Pin former sleeves  41  are coated with a release agent and inserted through collars  27  and sleeves  18  until flanges  44  contact the shoulders  18 B, as shown (FIG.  6 ). Seals  45  retain the polymer mixture. 
     FIG. 7  shows the end of tool B and insulator  11  as seen from the direction of arrow B. The ends of pin formers  40 , sleeves  18 , collars  21  and the fairings  21 A of collar  21  into insulator  11  are shown. Cavities  19 , again with fairings, are also shown. 
   The unpolymerised gel solution and hardener are mixed and injected into boot  23  via an aperture (not shown) to fill completely the space  28  inside boot  23  between pin former surfaces  41 ,  41 A and  41 B including annuli  28 A and  28 B. The polymer mixture as a low viscosity so completely fills all internal voids, including annuli  28 A and  28 B and is injected slowly, to avoid incorporation of air bubbles, until excess emerges from an appropriate point, e.g. one of the collars  27 . During filling, the whole is gently rotated and tilted to ensure complete filling without entrapping air bubbles. When full, the whole assembly is placed in an oven and gently-cured. 
   When fully cured, the assembly is removed from the oven and tool B removed from the insert assembly. Because a release agent is used, the polymerised gel will not adhere to surfaces  41  but will bond strongly to insulator  11 . Should a problem occur during tool removal, it can be dismantled  43  and any sticking pins gently rotated to free them. 
   Site assembly uses stripping tool C ( FIGS. 8 and 9 ) and cable bending tools D &amp; E, (FIGS.  10 - 12 ). 
   The end of cable  6  is placed in a vice and cut square. A predetermined length of armouring  6  is removed and the three cores gently separated. The cable lengths are marked off, using a template (not shown). Tool C is used to prepare pre-determined lengths of lead sheath conductors  9 . Sheathing  9  often has a square section and must be rounded to fit collars  27  of boot  23 . This is done by running smoothing tool  39  ( FIG. 8 ) down the conductor until the cut end reaches the limit of hole  38 . Handle  35  is provided to turn  36  tool C. This is repeated for each conductor  9 . 
   Now tool C is reversed and blind annular hole  34  slipped over lead sheathing  9  up to stop  37 , i.e. the end of blind hole  34 . Inside hole  34 , cutters  33  score sheathing  9  axially, as the cable is pushed in to stop  37 . Then tool C is rotated  36  using handle  35 , to cut sheathing  9  circumferentially. Removal of the cable from hole  34 , allows the cut sheathing to be peeled away, exposing insulation  10 . A length of insulation  10  equal to the axial depth of crimping annular space  14  is now removed exposing core  13 . This may be done with a knife or special tool (not shown). The exposed end  13  is now ready for crimping  14  to pin  12 . Drilling  15  permits checking that the correct length of insulation  10  has been removed. 
   The description above is given for armoured, lead sheathed cable commonly used for downhole operations. Another form of armoured cable used for this application has double annular layers of polymeric insulation. For this latter case, a modified tool C is provided to remove only the outer layer if insulation. 
   Contact pins  12  are crimped onto the exposed ends of cores  13 . A precision crimping tool (not shown) with hexagonal dies is preferred. Drilling  15  allows a check to be made that cores  15  are fully inserted into sleeve  14  before crimping. 
   Tools D and E ( FIGS. 10-12 ) are used to bend cores  9 ,  10  to fit insulator  11 . Both tools D and E consist of a short hollow cylinder  51 , with bores  52 , fast with an extended member  53  attached to a handle  54 . Bores  52  fit over pins  12 ,  14  (including O-ring  16 ), cores  10  and lead sheathing  9  and the two tools, D and E, are used together as levers to bend sheathing  9  (and insulated cores  10 ) so that the three insulated cores  10  and pins  12  are parallel to each other. A template  55 , with holes  56 , is provided to align pins  12  and insulated cores  10  to fit boot  23  and insulator  11 . It will be noted that template  55  has considerable depth  57  to ensure that pins  12  and insulated cores  10  are properly parallel and correctly spaced along their fill exposed length. 
   The three pins  12  and insulated cores  10  are passed into housing  8  through the cable hole. A cut out (not shown but covered by cut out  26  (FIG.  3 )) is provided in housing  8  to allow top contact pin  12  (hatched  FIGS. 2 and 5 ) to enter without affecting the parallel core alignment. Pins  12 ,  14  and cores  10  enter collars  27 , pass through pre-formed holes in gel  28 , through collars  20 ,  28 A,  28 B and into insulator  11 . Light greasing or an oil spray lubricant may be used to ease the passage through gel  28  into insulator  11 . The rounded ends of pins  12  enter circlips  17  and the bodies of the pins slide through until the circlips lock into grooves  50 . Insulated cores  10  can be pushed gently in via cable  6  as well as pulled, via pins  12 , when they emerge through insulator  11 . O-ring  16  will contact sleeve  18  forming a seal between oil-filled space  47  and crimped connection  13 ,  14 . 
   Axial clearance is provided in circlip grooves  50  and  32  to ensure that pins  12  lock into position irrespective of any minor differences in the axial length of insulated cores  10  or in the crimping  13 ,  14 . This is a further demonstration of the attention to detail in the design and method of the invention to guarantee a connection which is mechanically and electrically ideal for its purpose. 
   Cable clamp  24  is fitted and secured  25 . A lug  26  covers the cut out (not shown) in housing  8 . 
   The detail of the method of assembly is summarised as follows: 
   Factor Pre-assembly Stages:
         1. Fit boot  23  to insulator  11  and fill boot void  28  with gel using filling tool B with pin formers  40 ,  41 . Polymerise filling gel. Remove filling tool B with pin formers  40 ,  41 .   2. Fit pin-locking circlips  17  in sleeves  18 .   3. Insert insulator-boot assembly into housing  8  against shoulder  31 . Insert locking circlip  22 .   4. Fit O-rings  16  to pins  12  and package.   5. Package housing assembly  8 , including cable clamp  24 .       

   Site Assembly Stages:
         1. Place cable  6  in a vice and cut end square.   2. Strip armoured protection  6  back to a pre-determined length. Gently move insulated cores  10  apart.   3. Smooth lead sheathing  9  to give a round section (using tool C) and strip lead sheathing  9  from a pre-determined length of all three cores (again using tool C).   4. Strip insulation  10  to expose a pre-determined length of core  13 , using a knife or a stripping tool (not shown).   5. Fit exposed core  13  filly into annular space  14  in pin  12  (so that core is fully home  15  and insulation  10  abuts pin  12 ) and crimp using an hydraulic-crimping tool. Repeat for the other connectors.   6. Bend cores  9  and  10 , using tools D and E, so that pins  12  and insulated cores  10  are parallel to each other and align with template  55 .   7. Fit contact pin-insulated core assembly into collars  27  in boot  23  inside housing  8  so that pins  12  pass into sleeves  18 . Gently push and pull pins  12  until circlips  17  engage in the pin locking grooves and O-rings  16  are properly seated.   8. Fit cable clamp  24 .   9. Fit protective cover  46  with O-ring  48 , if appropriate.   10. The connector of the invention has been described with respect to a motor lead extension connection  7  for an electrically submerged pump  5  in an oil production well. This is a particularly arduous application where exceptional reliability is required without any maintenance being possible. The connector of the invention and method of using it are equally applicable to other situations where, though the environment is not so severe, extreme reliability is essential.