Underground Cable Connection

This invention relates generally as indicated to an underground cable connection, and more particularly to a cable clamp achieving positive electrical contact with all of the concentric exposed neutrals of underground residential distribution cable.

The electric utility industry has been utilizing direct burial power cables for rural or residential electrical distribution, such underground residential distribution cable being known as URD cable. Some of such URD cable is provided with a copper concentric neutral wrapped around the outside of the cable. The neutral may take the form of copper wire or flat copper strap applied spirally exteriorly of an extruded layer of semiconducting material.

In some locations, the exposed copper of the neutral has corroded and this can create a hazardous condition. To protect the copper against further corrosion or to retard corrosion, cathodic protection utilizing magnesium or zinc anodes has been employed. To be effective, the anode must be positively electrically connected to all of the URD concentric neutrals. It is, of course, important that the electrical connection between the anode and the cable neutrals be made quickly and positively without damage to the cable.

Prior attempts have been made to provide such positive electrical connection by placing a contact sleeve beneath the neutral wires or between such wires and the semiconductor shield. In field installations, it is, of course, difficult to get an inner sleeve under the neutral wires without damaging the semiconductor. Damage to the semiconductor may be quite significant, since if the semiconductor is gouged or dented, it may set up a stress point which would be susceptible to cable failure.

Other attempts have been made to obtain an effective connection for all of the exposed neutrals, but such connectors generally require an extensive amount of field fabrication, particularly if different size cables are involved. Moreover, with conventional bolted cable clamps, excessive stresses may be imposed on the semiconductor.

It is accordingly a principal object of the present invention to provide a URD cable clamp which will achieve a positive electrical contact between a lead wire and all of the URD exposed concentric neutrals.

Another principal object is the provision of such cable clamp or connection which can readily be field applied from a simplified kit without extensive field fabrication.

Another important object is the provision of an electrical connection for underground direct burial power cables which includes a completely tinned copper sleeve wrapped around the neutrals of the cable, such sleeve being provided with a tab having secured thereto a crimp or compression connector.

A further object is the provision of a URD cable clamp which does not require placement of a conductor between the neutral wires and the semiconductor therebeneath.

Still another object is the provision of a kit from which the aforementioned electrical connection can quickly be field fabricated.

These and other objects and advantages of the invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but several of the various ways in which the principles of the invention may be employed.

In said annexed drawings:

FIG. 1 is a perspective view illustrating the connection of the present invention applied to a URD cable;

FIG. 2 is an enlarged, transverse section of the connection taken substantially on the line 2--2 of FIG. 1;

FIG. 3 is an exploded view illustrating the components of the connection in the position of assembly;

FIG. 4 is a top plan view of the tinned soft copper L-shaped sleeve, on a reduced scale, employed with the present invention;

FIG. 5 is an end elevation of the sleeve as seen from the line 5--5 of FIG. 4; and

FIG. 6 is a detailed view of the hose clamp employed illustrating the special shim utilized therein.

Referring now to the drawing and more particularly to FIG. 1, there is illustrated a round wire concentric neutral URD cable at 10 to which the electrical connection 12 of the present invention is secured. The purpose of the electrical connection is to provide positive electrical contact between all of the concentric neutral round wires 15 and the lead 14. The lead 14 may be connected to a magnesium or zinc anode for cathodic protection of the cable. The lead 14 may also be a test wire.

The particular URD cable illustrated comprises a stranded aluminum or copper conductor 17 covered with an extruded layer of semiconducting material indicated at 18. Insulation 19 of the proper thickness surrounds the semiconducting material 18. As a shield, an extruded semiconducting insulation screen 20 is provided and finally a correct number of proper size solid copper neutral wires 15 are applied spirally. Although less common, the present invention is equally applicable to flat strap concentric neutral URD cables wherein the concentric neutral is formed by copper flat straps applied spirally.

The connection 12 may be readily field formed from a kit comprising three components as seen more clearly in FIG. 3. Such components comprise an inner sleeve 22, a rubber or neoprene gasket 23, and an outer clamp 24.

Referring first to the inner sleeve, which is also shown in reduced scale in FIGS. 4 and 5, it will be seen that the inner sleeve is stamped from 0.013 gauge soft copper into the L-shape shown. The long leg 26 of the L may be approximately 7 inches in length, while the short leg 27 is approximately 23/8 inches in length and approximately 7/8 inch wide. The use of soft copper provides a sleeve with no resilience so that when rolled into the shape shown in FIG. 3, it will remain in such shape. During stamping, a hole is stamped in the center of the short leg 1/4 inch from the end of the tab formed by the short leg. After the stamping operation, the inner sleeve is then electro-tin plated so that there are no exposed copper edges.

In the hole thus formed in the short leg, a brass nut 28 and a brass bolt 29 are then used to connect a ring-tong crimp connector to the short leg 27 or tab of the inner sleeve. The ring-tong 30 of the connector projects beyond the edge 31 of the short leg of the sleeve. After the crimp connector is secured to the short leg of the inner sleeve in the manner shown, the entire assembly is then soldered, preferably by dipping the short leg 27 in a solder pot. The dip line of the solder is shown at 32.

The gasket 23 may preferably be of neoprene and in the kit will be approximately 1/8 inch thick by 1 inch wide by 7 inches in length.

The outer clamp 24 consists of a stainless steel hose clamp. The clamp includes stainless steel spring member 34, to one end of which is secured the housing 35 for the screw or worm 36 which may be rotated by the hex or screw head 37. The opposite end of the spring member 34 is provided with a series of pitched slots 38 which engage the screw 36 upon tightening.

Secured to the inside of the spring member 34 is a stainless steel shim 39. The shim is secured by the flush rivet indicated at 40. The shim is somewhat more narrow than the spring member 34 and serves to shield the slots 38 from the gasket member 23 and helps to distribute the stresses caused by the tightening of the clamp circumferentially around the cable. The shim thus aids in alleviating any stress concentrations which might cause damage to the semiconductor jacket or shield 20. Tests so far have indicated that it is impossible to overtighten the clamp and damage the semiconductor 20.

For installation, the long leg 26 of the tinned copper sleeve is wrapped around the cable over the neutral wires as seen in FIG. 3. Depending upon the size of the cable, the long leg of the sleeve will overlap itself as indicated. Because of the nature of the soft copper employed, once wrapped to the position seen in FIG. 3, it will remain in such position. The neoprene or rubber gasket 23 is then trimmed in length to approximately 1/4 inch less than the circumference of the cable. The gasket is then placed over the inner sleeve 22 circumjacent thereto. The outer clamp is then placed around the gasket with the end of the spring member 34 being brought into engagement with the screw 36 and the screw tightened. The clamp should be tightened securely but not excessively. When tightened, as seen in FIG. 2, the sleeve 22 closely conforms to and is pressed against all of the exposed concentric neutrals. The anode or test lead wire 14 is then placed in the ring-tong 30 and crimped as indicated at 42 in FIG. 1. By providing the clamp with the ring-tong crimp connection soldered to the end of the tab 27, there is, of course, eliminated any necessity for a man in the field to tighten a connector to the tab 27. All he has to do is slip the lead into the ring-tong and crimp the same in place. Because of the projection of the ring-tong beyond the end of the tab, it is readily accessible to pliers or other crimping tools.

The entire connection 12 should then be coated with a dielectric coating compatible with the semiconducting jacket 20.

It can now be seen that there is provided a positive anode and test lead wire electrical connection which can readily be field fabricated from a simplified kit to achieve a positive electrical contact between the anode or test lead wire and all of the URD concentric neutrals.