Abstract:
An electrical connector assembly for a cable having a plurality of insulated conductors comprises a body having a respective recess for receiving a terminating pin each of the conductors. A respective spigot sealingly engages within each of the recesses and has a passage for receiving an associated one of the terminating pins. Furthermore a seal is associated with each of the spigots for sealing the spigot relative to the associated terminating pin. The provision of a separate spigot for each of the conductors and for sealing engagement within a respective recess in the body enables the spigots to be sealingly fitted to the conductors prior to each spigot being introduced into its recess and sealingly engaged therein. This provides improved insulation of the conductor and increased creepage distance between the mating electrical parts and the outer surface of the housing of the assembly. It also provides the additional advantage that the seal on the conductor tends to be smaller than in prior arrangements so that there is less thermal expansion of the seal when the parts get hot in a downhole environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 11/295,348, filed Dec. 6, 2005 now U.S. Pat. No. 7,264,494, which is based on, and claims priority from, British Application Serial Number 0426585.6, filed Dec. 6, 2004. Each of the aforementioned related patent applications is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Filed of the Invention 
     This invention relates to electrical connector assemblies for cables having a plurality of insulated conductors, and to socket connector assemblies for electrical connection to such connector assemblies, and is more particularly, but not exclusively, concerned with such connector and socket assemblies for use with electric submersible pumps and compressors. 
     2. Description of the Related Art 
     Electric submersible pumps (ESP) are installed in subterranean wells for extracting hydrocarbons where the natural pressure in the reservoir is insufficient to lift the fluid or gas to the surface. The ESP motor is powered through a cable that connects the motor to a power source at the surface. The cable is connected to the motor by means of a detachable electrical connector assembly designed to provide electrical integrity and to seal the motor against the ingress of well fluids. 
     U.S. Pat. No. 5,567,170 discloses a plug-in type electrical connector assembly that can be used to connect the cable to the ESP motor. In this arrangement the motor is provided with a machined port, called a pothole, and the motor windings are terminated at a socket assembly within the pothole into which the connector assembly can be plugged. In this case the pothole is a single round hole containing a single socket connector block containing terminals that are connected to the motor windings by means of braided wire leads. The socket connector block is mechanically secured to the motor housing independently of its connection to the windings. 
     The connector assembly terminating the power cable that is run from the surface, called the pothead, is inserted into the pothole and is sealed against the ingress of well fluids by an elastomeric gasket or an O-ring. 
     The pothole is machined at an angle to the axis of rotation of the motor for ease of manufacturing. However, the angled pothole limits the length of the mating electrical parts of the connector and socket assemblies, and consequently limits the length of insulating material that can be provided around the parts to provide a long creepage distance between the outside of the connector assembly and the electrical interface between the connector and socket assemblies. It is important to provide as long a creepage distance as practically possible as a significant failure mechanism in such connection arrangements is electrical tracking from the live electrical parts to the motor housing, exacerbated by ingress of moisture after operation over many months or years. 
     Furthermore, because the primary seal with respect to each conductor from the cable bears against the conductor insulation and the conductor insulation is liable to swell when subjected to the high temperature environment of the well, the seal integrity is compromised. 
     U.S. Pat. No. 6,676,447 discloses a further plug-in type electrical connector assembly for an ESP motor in which three insulated conductors from the cable extend through three separate passages in a first insulating block and are sealed within these passages by means of separate washers compressed by three protrusions extending from a second insulating block screwed to the first insulating block. Such an arrangement suffers from the fact that the primary seal with respect to each conductor bears against the conductor insulation and the conductor insulation is liable to swell when subjected to the high temperature environment of the well. Furthermore, as the elastomeric materials of the insulation and the seal increase in volume, the insulation can be damaged or the seal integrity diminished. 
     U.S. Pat. No. 3,997,232 discloses a motor connector assembly that is attachable to the top of the motor housing by way of a pothole extending parallel to the motor axis. Motors with thrust bearings in the top cannot have the connector on top of the motor as it is not possible for the three insulated conductors from the cable to be passed beyond the bearing. However the three insulated conductors from the cable extend through three parallel passages in a common sealing gland, and thus there are again difficulties in terms of the integrity of the seals in a downhole environment. 
     U.S. Pat. No. 4,204,739 discloses a motor connector assembly having separate potholes for each conductor. Each conductor is provided with a strain relief and seal assembly that is tightened in the motor head independently of the assemblies of the other conductors. However each of the conductors is sealed within the corresponding pothole by a respective O-ring seal, so that there are difficulties in assembly as well as in the integrity of the sealing as a result of the direct sealing of the O-ring seal on the conductor insulation. Also there is insufficient strain relief for the conductors with the result that there is a risk that the conductors will be pulled out of the motor when it is installed in a well. 
     U.S. Pat. No. 5,700,161 discloses a two-piece pothead casting that is assembled in two halves and that is split radially across the conductors. However the three insulated conductors from the cable extend through three passages in a common insulating block, and thus there are again difficulties in terms of the integrity of the sealing in a downhole environment. Typically, in such arrangements, the motor head, within which the pothole is formed, is required to be screwed into the tubular motor housing during assembly. This means that there is little control over the relative rotational positions of the pothole and the motor stator within the housing. Furthermore the flexible leads connecting the stator windings to the socket connector block within the pothole tend to be wound around the motor shaft as the motor head is screwed into the motor housing, a protective tube being provided to separate the leads from the shaft. Such winding of the leads around the motor shaft during assembly can introduce further possible failure mechanisms, and it is not possible to observe the twisted motor leads and their connection to the stator windings once the motor head has been assembled with the motor housing. Any resulting chafing, cuts or strain on the internal electrical joints may not be revealed during initial electrical testing but may remain as a weak point during long-term service. 
     It is an object of the invention to provide an electrical connector assembly and corresponding electrical socket assembly that avoids many of the pitfalls associated with known assemblies. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided an electrical connector assembly for a cable having a plurality of insulated conductors, the connector assembly comprising: a body having a respective recess for receiving each of the conductors; a respective spigot for sealing engagement within each of the recesses and having a passage for receiving an associated one of the conductors; and sealing means associated with each of the spigots for sealing the spigot relative to the associated conductor. 
     The provision of a separate spigot for each of the conductors and for sealing engagement within a respective recess in a body of the assembly enables the spigots to be sealingly fitted to the conductors prior to each spigot being introduced into its recess and sealingly engaged therein. When provided in a motor the separate spigot allows the conductor terminal to be parallel with the motor shaft and therefore permits an elongated connector assembly internal to the motor. This provides improved insulation of the conductor and increased creepage distance between the mating electrical parts and the outer surface of the housing of the assembly. It also provides the additional advantage that the seal on the conductor tends to be smaller than in prior arrangements so that there is less thermal expansion of the seal when the parts get hot in a downhole environment. 
     According to a further aspect of the present invention, there is provided an electrical socket assembly for electrical connection to an electrical connector assembly for a cable having a plurality of insulated conductors, the socket assembly comprising: a housing having a respective recess for receiving an end of each of the conductors; a respective socket part for sealing engagement with each of the recesses and having a passage for detachably receiving the associated conductor end for electrical connection thereto; and a respective electrically insulating sleeve surrounding each of the socket parts. 
     Such an arrangement permits a relatively long creepage path between the mating electrical parts and the outer surface of the housing of the assembly. 
     According to a further aspect of the present invention, there is provided an electrical connector assembly for a cable having a plurality of insulated conductors, the connector assembly comprising a body having a respective recess for receiving each of the conductors; a respective conductive terminating pin connected to an end of each of the conductors; and a respective sealing means acting between an outer surface of each terminating pin and an inner surface of the corresponding recess. 
     Such an arrangement has the advantage that the primary sealing means with respect to the conductor no longer bears against the conductor insulation that is liable to swell when subjected to the high temperature downhole environment. Instead the sealing means bears against the outer surface of the conductive terminating pin which is much more stable at high temperatures. An insulating barrier preferably covers the pin/conductor connection to provide increased electrical integrity. Most preferably the barrier is sealed with elastomeric calk, with a crimped lead sheath or by crimping of the barrier itself to a lead sheath so as to render the connection gas tight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be more fully understood, preferred embodiments in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of the connector assembly attached to the motor in a first embodiment; 
         FIG. 2  is an axial section through parts of the motor and connector assembly; 
         FIGS. 3 and 4  show the connector assembly in assembled and disassembled states; 
         FIGS. 5 ,  6  and  7  are axial sections through corresponding parts of three different embodiments of the connector assembly; 
         FIG. 8  is an axial section through parts of interengaging connector and socket assemblies in accordance with the first embodiment; 
         FIG. 9  is an exploded perspective view of the socket assembly and associated motor; 
         FIGS. 10 to 16  are axial sections through parts of further embodiments of the invention ( FIGS. 10 and 12  showing only half of the section in each case); 
         FIG. 17  is an axial section through part of a preferred embodiment of the invention; and 
         FIG. 18  is an exploded perspective view of top and bottom casting parts of the preferred embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiments of the invention described below with reference to the drawings relate to the connection of power cables to the motors of ESP&#39;s, although it will be appreciated that other connector and socket assemblies in accordance with the invention can be used for other purposes, and this particular application is only given by way of example. 
     Referring to  FIG. 1 , this shows the electrical connector assembly  1 , that is the pothead, and the end of a cable  2  for supplying power from the surface plugged into the motor head  3  so as to establish an electrical connection with the windings of the motor stator. As shown the cable  2  extends within a slot  4  in the motor head  3 . 
     The cable used is typical for ESP applications and contains multiple conductors that have one or more layers of insulation with one or more layers of protective material. Three conductor flat cable with an interlocking metal armour with each conductor protected by a lead sheath, EPDM (ethylene propylene diene monomer rubber) insulator jacket, and Kapton insulation is used in the described embodiments but those skilled in the art will be aware that other types of cable can be used with slight modification to the connector. 
     In the axial section through the motor head  3 , the motor housing  3   a  and the pothead  1  shown in  FIG. 2 , the motor shaft  6  journalled within the motor housing  3   a  by bearings  7  and  7 ′ can be seen. An end view of the motor head  3  is shown on the left-hand side of the figure in which the location of the cable  2  containing three insulated conductors within the slot  4  in the motor head  3  can be seen, the sectional view being taken along the line A-A. Each of the insulated conductors is terminated by a respective spigot  8  sealed within a recess  9  of the connector assembly, as will be described in more detail below. The connector assembly  1  is shown plugged into a corresponding socket assembly  11  incorporating a respective socket  12  for receiving the associated conductor end for electrical connection thereto. 
     Referring to the assembled and disassembled views of the connector assembly shown in  FIGS. 3 and 4 , each of the three insulated conductors  20  extends through a respective one of three screwthreaded recesses  21  formed in an arcuate configuration in a first casting part  22  and has an elastomeric sealing gland  23 , a threaded spigot  24  fitted with an O-ring  25 , a PEEK insulating sleeve  26  and a conductive terminating pin  27 . The insulating sleeve  26  is bonded to the insulation of the conductor  20  in order to protect the insulation from motor oil and any trace gas that permeates into the motor. This is necessary because the insulation (EPDM) swells and deteriorates unless protected from such motor oil and will experience explosive decompression from gas permeation. 
     In order to seal the spigot on each conductor  20 , the sealing gland  23  is located between a shoulder in each recess  21  and the end of the spigot  24  so as to be compressed as the spigot  24  is screwed into the screwthreaded recess  21 . The resulting compression of the sealing gland  23  serves to compress the outer surface of the insulation of the conductor  20  by means of the inside surface of the sealing gland  23 , as well as compressing the outer surface of the sealing gland  23  against the inner surface of the recess  21  and the end surfaces of the sealing gland  23  against the shoulder and the end of the spigot  24 , thus providing fluid-tight sealing of the conductor  20  within the recess  21 . Such compressive sealing can be assisted by causing each recess  21  to taper inwardly towards the shoulder on which the sealing gland  23  is seated. 
     As best seen in  FIG. 3 , each of the spigots  24  protrudes from the casting  22  when screwed fully within its corresponding recess and has its associated O-ring  25  fitted so as to be accommodated within an annular groove in the outer surface of the spigot  24 . Furthermore the insulating sleeve  26  extends between the end of the spigot  24  and the terminating pin  27  soldered onto the exposed end of the conductor  20 . The O-rings  25  serve to seal the spigots  24  with respect to the corresponding receiving sockets of the socket assembly as described in more detail below. A second casting part  28  is connected to the first casting part  22  by screws  29  so that the conductors  20  pass between the two casting parts  22  and  28 . If required the cavity between the casting parts  22  and  28  can be filled with epoxy to improve the strain relief on the cable  2 . If no epoxy is used the cable  2  can be clamped by the clamping force produced when the two casting parts are screwed together. Alternatively a one-piece casting can be provided with a space through which the conductors are passed, with the cavity surrounding the conductors optionally being filled with epoxy to provide the strain relief on the cable. Screw fasteners  30  are provided for mechanically securing the connector assembly to the motor housing when the connector assembly is plugged into the socket assembly. 
     Various modifications of the above-described arrangement for sealing the spigot on the conductor are possible within the scope of the invention, and three such alternative arrangements are shown in  FIGS. 5 ,  6  and  7 . The arrangement of  FIG. 5  is substantially similar to that described above with reference to  FIGS. 3 and 4  except that the insulating sleeve  26  extending between the end of the spigot  24  and the terminating pin  27  is replaced by a longer sleeve  26 ′ that also extends through the axial passage within the spigot  24 . This is intended to provide improved sealing. 
     In the case of the arrangement of  FIG. 6 , the sealing gland  23  is replaced by a compression sleeve  32  fitted to the outer surface of the conductor  20  and positioned to be compressed between angle sections on the spigot  24  and the inside wall of the recess  21  as the spigot  24  is screwed into the recess  21 . Otherwise the arrangement is similar to that described with reference to  FIGS. 3 and 4 . 
     In the arrangement of  FIG. 7 , the spigot  24 ′ is provided with a shoulder  35  in the passage  36  through which the conductor  20  (and the insulating sleeve  26 ′) extends, and the required sealing of the spigot  24 ′ on the conductor  20  is effected separately from the subsequent screwing of the spigot  24 ′ into the associated recess in the casting. One or more O-rings  33  are located between the shoulder  35  in the passage  36  and a compression nut  34  that is screwed into a screwthreaded portion of the passage  36  to compress the O-rings  33  into engagement with the outer surface of the insulating sleeve  26 ′. Only after sealing of the spigot  24 ′ on the conductor  20  in this manner is the spigot  24 ′ screwed into the associated recess in the casting so that the portion of the spigot  24 ′ bearing the O-ring  25  projects from the casting in the manner shown in  FIGS. 3 ,  5  and  6 . In other, non-illustrated variants the spigot is not engaged within the recess by screwing but instead is a press fit within the recess by the engagement of complementary formation on the spigot and the inside of the recess, or a slip fit with a snap ring being provided to engage within a receiving groove in the inside wall of the recess. Alternatively the spigot may simply be arranged to be trapped between the two casting halves when these are screwed together, installed with a retaining ring, or bonded within the recess by adhesive. In the trapped configuration, the spigot could have limited float to allow for tolerance variations in the mating parts. 
     Various other arrangements can be contemplated within the scope of the invention but are not separately illustrated. For example an elastomeric gland element may be moulded into the inside surface of the spigot so as to provide an interference fit relative to the outer surface of the conductor to form the required fluid-tight seal. As a further alternative a stack of O-rings may be fitted to the underside surface of the conductor so as to provide an interference fit with the inside surface of the passage extending through the spigot. As a further alternative a stack of O-rings may be fitted to the outside surface of the conductor so as to engage the inside surface of the recess in the casting when compressed by screwing of the spigot into the recess. It will also be understood that the O-rings shown in the illustrated embodiment of  FIG. 7  may be replaced by an elastomeric sealing gland or some other sealing element. 
       FIG. 8  shows the mating parts of the socket assembly into which the connecting parts of the connector assembly are plugged as shown in  FIGS. 1 and 2 , only one of the three sockets being shown in section in the figure. In this case the terminating pin  27  provided at the end of each conductor  20  engages within a corresponding socket part  40  provided within a long insulating sleeve  41  of the socket assembly defining a bore  42 . The socket parts are accommodated within a conductive canister  54  that is in turn connected to stator  51  as described in more detail below. The conductor  20  with the insulating sleeve  26  and terminating pin  27  thereon is inserted into the insulating sleeve  41  to provide a long creepage distance between the interconnecting conductive parts and the outside of the connector assembly. 
     The insulating sleeves  41  are inserted into the corresponding recesses  9  in the motor head when the stator is installed in the motor housing. The O-ring  25  on the spigot seals on the inner wall of recess  9  in the motor head to provide a fluid tight seal for the motor. Other possible, non-illustrated arrangements for sealing of the spigot with respect to the internal surface of the bore can be contemplated within the scope of the invention. Instead of the O-ring provided for this purpose a seal may be moulded on the outside surface of the spigot so as to provide the required sealing with respect to the inside surface of the bore. Alternatively a custom moulded seal could be fitted to the outside of the spigot to provide an interference fit with the inside surface of the bore. As a further alternative a seal may be provided that seals between a shoulder on the spigot and the end of the bore or the face of the end plate of the motor head. 
     Instead of, or in addition to, the insulating sleeve  26 ,  26 ′ surrounding the conductor  20 , ptfe (polytetrafluiroethylene) tape may be wound around the portion of the conductor  20  to be insulated to provide protection and added insulation and to protect the insulation from motor oil and contaminants. 
     The construction of the socket assembly is best understood by reference to the exploded view of  FIG. 9  showing the stator windings  50  within the stator housing  51  and the coil terminations  52  of the stator windings. Each coil termination  52  is connected to a flat end region of a conductive socket part  40  by a wire  45  ( FIG. 8 ), and each socket part  40  is accommodated within a respective insulating sleeve  41  that extends forwardly of the socket part  40  as shown in  FIG. 8 . In addition a further, smaller insulating sleeve  53  is provided around the narrowed end portion of the socket part  40 . The insulating sleeve  53  enters the end of the insulating sleeve  41  so as to ensure a long creepage path at the rear of the assembly, and insulating tape is wound around the connecting lead from the stator winding up to and over the sleeve  53 . After assembly of these parts the canister  54  is passed over the parts and secured to the end of the stator housing  51  by screws  55 , and the sheathed socket parts  40  are moved radially outwardly so as to engage them within receiving notches  56  prior to screwing of an end plate  57  to the end of the canister  54  by means of screws  58  so as to align the socket parts  40  with holes  59  in the end plate  57 . The insulating sleeves  41  can float radially to a small extent within the holes in the end plate  57  during the final alignment stage of stator insertion. 
     A guiding pin  10  projects from the end plate  57  for the purpose of locating the three sockets parts  40  in the required orientation when the stator is inserted into the motor housing. The guiding pin  10  engages first to ensure proper alignment before the more fragile insulating sleeves  41  engage within their respective holes. Some designs will not require the guiding pin  10  to protect the insulating sleeves during insertion. 
     Because the stator and its associated connector parts are first assembled and then inserted as a whole into the motor housing, it is necessary to ensure the correct alignment of the stator and the pothole. Since no access to the motor connections is required during the subsequent assembly process, it is possible for the motor head to be welded to the motor housing, thus eliminating the need for a threaded joint and seal. Additionally it is preferred that the stator  51  is provided with a keyway  60  for engagement with a complementary formation on the inside surface of the motor housing so as to locate the stator with the correct orientation within the motor housing. In this case it follows that, if the motor head is welded to the motor housing with the correct orientation, then the stator will necessarily be in the required alignment with respect to the pothole so that the motor connections enter the potholes during the last stage of insertion. Such keying also provides the additional operational advantage that no strain is put on the motor windings as the connections are always mechanically guided without deflection or twisting. A known failure mechanism of existing motors is that, during initial motor starting before the stator has warmed up and differentially expanded against the housing to grip it, the torque reaction of the stator to the rotor can cause the stator to rotationally slip in the rotor housing resulting either in instantaneous motor failure by shearing of the windings or damage to the conductor insulation in such a manner as to lead to subsequent failure. This known failure mechanism is eliminated by the keying arrangement described above. 
       FIG. 10  is a section (only half of the section being shown) through one of the conductors  20  of a further embodiment of connector assembly in accordance with the invention. In this embodiment the terminating pin  27 ′ is of extended length so as to permit sealing of the spigot  24 ′ with respect to the terminating pin  27 ′ by means of an O-ring seal  23 ′ seated against a shoulder  27   a  of the terminating pin  27 ′, rather than such sealing being with respect to the wire insulation of the conductor as in the previously described embodiments. This is advantageous because the terminating pin  27 ′ does not swell to any appreciable extent under the high operating temperatures, and thus the seal is not compromised to the same extent as it would be if made with the insulation of the conductor. Furthermore the spigot  24 ′ is integral with an insulating sleeve  26 ′ surrounding the terminating pin  27 ′, rather than the spigot and insulating sleeve forming separate components as in the previously described embodiments. In addition the spigot  24 ′ is formed with a terminating bush  73  having a profiled outer surface over which a lead jacket  72  is swaged in order to provide a gas-tight connection between a lead sheath  74  of the conductor  20  and the spigot  24 ′. The spigot  24 ′ is provided with an outer O-ring seal  25 . The assembly is encased within a two-part casting comprising a bottom casting part  70  and a top casting part  71  which are screwed together so as to surround the assembly with the top casting part  71  engaging the armour surrounding the cable  2 . 
     In a further embodiment shown in  FIG. 11 , the spigot  24 ″ is a separate part from the insulating sleeve  26 ″, and surrounds a portion of the insulating sleeve  26 ″ so as to engage with the shoulder  26   a  thereon. In this case an O-ring seal  75  is provided between the inside of the insulating sleeve  26 ″ and the outside of the terminating pin  27 ′, and a further O-ring seal  23 ″ is provided between the insulating sleeve  26 ″ and the spigot  24 ″. Furthermore the insulating sleeve  26 ″ is provided with a profiled bush  73  over which a lead jacket  72  is swaged for establishing a fluid-tight connection between the insulating sleeve  26 ″ and the lead sheath  74  of the conductor  20 . An adhesive filler or sealant  76  is provided between the insulation of the conductor  20  and the insulating sleeve  26 ″. This embodiment also has the advantage that the primary seal is provided between the insulating sleeve  26 ″ and the conductive terminating pin  27 ′ so that the integrity of the seal is maintained at high temperatures. 
     A variant of the embodiment of  FIG. 10  is shown in  FIG. 12 , the conductor  20 , the terminating pin  27 ′ and the various seals being omitted from this figure in order to render it easier to read. In this case the spigot  24 ′ with its integral insulating sleeve is a loose fit within the two-part casting in order to allow it to float with respect to the casting for alignment purposes during installation in the motor. 
     A further variant of the embodiment of  FIG. 10  is shown in  FIG. 15 . In this case the terminating pin  27 ″ is moulded into the insulating sleeve  26 ″ and formed with ribs  77  providing added strength and sealing within the sleeve  26 ″. The insulating sleeve  26 ″ is integral with the spigot  24 ″ which is bonded to a separate terminating bush  73 ′ by way of a special bonding joint. The spigot  24 ″ is provided with either an O-ring seal  25  (as shown at the bottom of the figure) or an elastomeric sealing member  25 ′ (as shown at the top of the figure). In addition the gap between the casting part  71  and the terminating bush  73 ′ may be filled with a sealing compound, such a Viton caulk compound, to improve the sealing and provide improved strain relief on the cable. 
       FIG. 13  shows a further embodiment of the invention as applied to a connector assembly of a more standard type in which the three conductors extend through recesses in a common insulator block  84  retained within a generally cylindrical casting  90  by means of a retaining ring  89 . The external circumference of the insulator block  84  is sealed with respect to the motor head when the connector is inserted into a corresponding socket by means of either an O-ring  88  (as shown at the top of the figure) or an elastomeric sealing member  88 ′ (as shown at the bottom of the figure). As in the previously described embodiments, the conductor  20  is terminated by a conductive terminating pin  87  surrounded by an insulating sleeve  86  sealed with respect to the terminating pin  87  by an O-ring seal  83  and having in addition an O-ring seal  85  for sealing the outside of the insulating sleeve  86  within the recess extending through the insulator block  84 . As in the previously described embodiments, the insulating sleeve  86  is formed with a profiled bushing  93  over which the lead sheath  94  of the conductor  20  may be directly swaged. If required a lead sleeve or other gas impermeable membrane sleeve or tape could be used to seal the lead sheath  94  of the motor cable to the insulating sleeve  86 . Furthermore the gap  91  between the casting  90  and the conductor  20  may be filled with an epoxy or liquid fluoroelastomer compound to improve the sealing with respect to the conductor  20  and provide improved strain relief on the cable. 
       FIG. 14  shows a further embodiment that is generally similar to the embodiment of  FIG. 13  but that has an insulating sleeve  86 ′ formed integrally with its insulator block  84 ′, rather than the two parts constituting distinct components as in the embodiment of  FIG. 13 . In this case the primary sealing between the insulating sleeve  86 ′ and the conductive terminating pin  87  is provided either by an O-ring seal  83  (as shown in the lower part of the figure) or by an O-ring seal  83 ′ (as shown in the upper part of the figure) engaging against a shoulder  87   a  on the terminating pin  87 . Furthermore the sealing between the insulator block  84 ′ and the motor head on connection of the connector to a corresponding socket is effected either by an O-ring seal  88  (as shown in the upper part of the figure) or an O-ring seal  88 ″ (as shown in the lower part of the figure) engaging against an outer shoulder  95  on the insulator block  84 ′. 
     A further variant is shown in  FIG. 16 . In this case the terminating pin  87 ′ is formed with ribs  77  and is moulded within the insulator block  84 ″. The insulator block  84 ″ is bonded to a separate insulating sleeve  86 ″, and an elastomeric filler  96  is provided between the insulating sleeve  86 ″ and the conductor  20  to improve sealing. 
     In each of the above described embodiments the method of assembly of the connector is as follows. Each of the conductors  20  is prepared by removal of the armour of the cable, the lead sheath and the insulation of the conductor to the required lengths. The copper conductor end is then soldered or crimped within the terminating pin. The conductor with the pin thereon is then inserted into the insulating sleeve, and preferably bonded therein with adhesive. In the case of the embodiments of  FIGS. 15 and 16  the terminating pin is moulded within the insulator block so that a special conductor assembly procedure is required. Where provided, the lead jacket is then swaged over the end of the insulating sleeve and the conductor sheath. If required the lead jacket can be soldered to the sheath. If required the lead sheath on the conductor can be expanded prior to insertion of the terminating pin into the insulating sleeve so that the lead sheath slides over the insulating sleeve and can be swaged thereon. The connector assembly is then inserted into the pothead casting, and, if required, filler material may be poured into the cavity intermediate the casting and the conductors to anchor the connector to the cable and provide strain relief for the cable. 
     In the description of the connector assembly O-rings are used to seal the assembly. If required, the O-rings could be replaced with other fluid barrier seals, such as T-rings, quad rings, U-cup seals, chevron packs, etc. Furthermore the internal O-rings could be replaced by liquid sealants, such as Aflas Caulk or injected moulded compounds. 
     One of the conductors  120  of a preferred embodiment of the invention is shown in axial section in  FIG. 17 . As in the embodiment of  FIG. 10 , the terminating pin  127  is of extended length so as to permit sealing of the spigot  124  with respect to the terminating pin  127  by means of an O-ring seal  123  seated within an annular recess in the terminating pin  127 . Furthermore an outer O-ring seal  125  is provided within an annular recess in the spigot  124  as in a number of the previously described embodiments. The spigot  124  is screwed into a screwthreaded recess  121  in a top casting part  171  of a two-part casting, as shown in  FIG. 18 . In addition the spigot  124  is formed with a terminating bush  173  for engaging over a lead sheath  174  of the conductor  120 . The assembly is encased within the two-part casting together with two similar assemblies, with the top and bottom casting parts  171  and  170  being screwed together so as to surround the assembly, and is connected to the motor housing by fasteners extending through holes  175  in the upper casting part  171  as shown in  FIG. 18 .