Patent Publication Number: US-5896258-A

Title: Oil circuit recloser operator

Description:
FIELD OF THE INVENTION 
     The invention relates to circuit reclosers which open an electrical power circuit during abnormal conditions and then automatically reclose the circuit after a brief interval of time. 
     BACKGROUND OF THE INVENTION 
     Electric power distribution lines are occasionally subjected to lightning strikes or grounding. Lightning strikes and groundings result in a sudden surge of electric current through the power lines. These sudden current surges may damage transformers, power lines and other related equipment in the electric power distribution grid. Since sudden surges of current, caused by lightning strikes or grounded power lines, usually last for only a fraction of a second, standard circuit breakers cannot be used to limit the current on the distribution lines because they shall keep the circuit open even though the fault condition has passed. Automatic circuit breakers, referred to as reclosers, are used in place of standard circuit breakers for protecting transmission lines against current surges. 
     Reclosers are designed to open a circuit when a current surge is sensed and then reclose the circuit within a few moments. When a recloser device is used to limit current flow through electric power lines, sudden current flows resulting from a lightning strike or a downed power line causes contacts within the recloser to separate, thereby opening the circuit and limiting the current flow. After opening the circuit, the recloser is designed to wait an interval of time, approximately one second in most cases, before bringing the internal contacts back together to close the circuit. If the current is still too high, the recloser opens the circuit again, thereby limiting the current through the lines. Again, the recloser closes the circuit after a few moments. Reclosers are designed to successively reclose only a few times, typically three times, before going into an open circuit configuration. In the open circuit configuration, the recloser remains open and can only be closed by physically turning a lever located on its surface. 
     In many cases, a fault condition may place several reclosers along an electric power line in their open circuit configuration This requires workers to travel to each of the reclosers to reset them back into their closed circuit configuration. The time and effort required to reset all of the reclosers along the distribution lines can add significantly to the cost and delay of restoring electrical power after a failure. 
     DISCLOSURE OF THE INVENTION 
     The present invention is directed at a recloser device for limiting the current on a power line when a fault condition occurs, the recloser having an interrupting means for interrupting the current. The interrupting means is switchable between a closed state, where current flows through the lines, and an open state where the current is interrupted. The device also has a member operatively coupled to the interrupting means. The interrupting means being able to move the movable member from a first position to a second position when the interrupting means switches from its closed state to its open state. The movable member is also able to reset the interrupting means from its open state to its closed state when the movable member is moved from its second position to its first position. The device also includes a means for remotely moving the movable member from its second position to its first position, the remote moving means being operatively coupled to the movable member. 
     The present invention is also directed at a device for converting a standard recloser to a remotely activatable recloser. The standard recloser has a movable member which is moved from a first position to a second position when the recloser switches from its closed to its open state. The movable member can reset the recloser back into its closed state by moving from the members second position to its first position. The converting device itself includes a housing mountable to the recloser at a position on the recloser adjacent to the movable member. The converting device also includes a remote moving means mounted to the housing and being able to operatively couple with the member. The remote moving means is adapted to move the member from its second position to its first position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the method and device embodying the present invention will now be described and made clearer from the ensuing description, reference being had to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of the preferred embodiment of the invention; 
     FIG. 2 is a perspective view of the control device of the present invention showing the switch operating lever in its first position; 
     FIG. 3 is a front view of the control device of the present invention showing the switch operating lever in a position between its first and second positions; 
     FIG. 4 is a front view of the control device of the present invention showing the switch operating lever in its second position; 
     FIG. 5 is a side view of the control device of the present invention, and 
     FIG. 6 is a perspective view of a portion of the control device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring firstly to FIG. 1, the remotely activated recloser, shown generally as item 10, comprises a remotely activated recloser control device 12 having cover 11 mounted to a standard circuit recloser shown generally as item 15. Circuit recloser 15 has tank portion 20, head casting 22, insulated bushings 14, switch lever 16 and sleet hood 24. Insulated bushings 14 are connectable to electrical power lines (not shown). Tank portion 20 contains a pair of electrical contacts (not shown) suspended in electrically insulating oil. The electrical contacts are operatively coupled to insulated bushings 14. The recloser interrupts the current through the line by means of opening the electrical contacts. 
     Under normal operating conditions, the electrical contacts are in physical contact with each other and current can flow through the electrical power lines coupled to insulated bushings 14 and the recloser is said to be in its closed configuration. When the electric current exceeds a predetermined level, an electromagnet inside tank portion 20 physically separates the electrical contacts, thereby opening the circuit and interrupting the current flow. The electrical contacts are biased towards each other by a spring; therefore, after a brief moment of time the contacts are brought back into physical contact. If the fault condition is long lasting, then the electrical contacts shall separate and recloser 15 is placed into its open circuit configuration wherein the electrical contacts are placed into a stable position where they no longer make physical contact with each other. 
     Switch lever 16 is operatively coupled to the internal electrical contacts via a rotatable operating shaft 28 which in turn is operatively coupled to the electrical contacts. Operating shaft 28 passes through sleet hood 24 and into head casting 22. When recloser 15 is in its open circuit configuration, switch lever 16 and shaft 28 are usually in a vertical position as shown in FIG. 1. When recloser 15 switches from its open circuit configuration to its closed circuit configuration, operating shaft 28 rotates into a second position. Switch lever 16 is approximately in a horizontal position when recloser 15 is in its closed circuit configuration. Since switch lever 16 is rigidly connected to operating shaft 28, moving the switch lever from its vertical position to its horizontal position causes operating shaft 28 to rotate and forces the electrical contacts back into their closed circuit configuration. 
     Referring now to FIGS. 2 and 3, recloser control device 12 comprises mounting plate 26, drive motor 36, drive motor control interface 25 and cable 18 and lever member 29. Mounting plate 26 is rigidly connected to sleet hood 24 via bolts or some other suitable means. Drive motor 36 is operatively coupled to operating shaft 28 by lever member 29 and can rotate operating shaft between its open circuit configuration as shown in FIG. 2 to its closed circuit configuration as shown in FIG. 3. Lever member 29 provides motor 36 with a mechanical advantage. Lever member 29 comprises shaft gear 30 having shaft gear hub 32. Shaft gear hub 32 is preferably integral with shaft gear 30, and both are rotatably mounted to operating shaft 28 such that the shaft gear and the hub can be rotated freely about the operating shaft. Drive motor 36 is rigidly mounted to mounting plate 26 and has drive gear 34. Drive gear 34 meshes with shaft gear 30 such that when the drive means is activated the drive gear can be rotated in either direction. Mounted onto one side of shaft gear 30 is first activator 38. Second activator 40 is mounted to the other side of shaft gear 30 opposite first activator 38. First microswitch 42, second microswitch 44 and third microswitch 46 are mounted to mounting plate 26 around the periphery of shaft gear 30. 
     Referring to FIG. 2, hub 32 has a groove or slot 48 passing therethrough. Operating shaft 28 has a protruding drive pin 50 rigidly mounted thereto. Drive pin 50 is dimensioned to fit within slot 48 in a tongue in groove fashion. As best seen in FIG. 6, drive pin 50 extends through both sides of operating shaft 28. Since shaft gear 30 and hub 32 are rotatably mounted to operating shaft 28, shaft gear 30 can rotate freely in either direction relative to the operating shaft until drive pin 50 makes contact with edges 51 and 53 of the hub adjacent slot 48. Slot 48 is dimensioned so that shaft gear 30 can rotate approximately 90° relative to operating shaft 28 before drive pin 50 comes in contact with either edges 51 or 53. Slot 48 and drive pin 50 form a limiting means for limiting the free rotation of shaft 28 relative to shaft gear 30. If shaft gear 30 is rotated in either direction more than 90° degrees, then it shall rotate operating shaft 28. Likewise, shaft gear 30 can be rotated into a position such that operating shaft 28 can freely rotate 90° in one direction. 
     Referring now to FIGS. 2, 3 and 4, drive motor 36 is controlled by motor control interface 25, which in turn is operatively coupled to a remote operator via communication cable 18. Motor control interface 25 forms a means for coupling drive motor 36 with a remote operator. Motor control interface 25 controls how many degrees and in which direction drive motor 36 turns shaft gear 30. Drive motor 36 is sufficiently powerful, and the mechanical advantage provided by the relative diameters of drive gear 34 and shaft gear 30 is sufficiently high that the drive motor can rotate operating shaft 28 between its horizontal position as shown in FIG. 3, wherein recloser 9 is in its closed circuit configuration, to the shafts vertical position as shown in FIG. 2, wherein the recloser is in its open circuit configuration. The position of shaft gear 30 is measured by a position locator means comprising microswitches 42, 44 and 46 and first and second activators 38 and 40. Microswitches 42, 44 and 46 are operatively coupled to motor control interface 25. As shaft gear 30 rotates from one position to another, activators 38 and 40 trip microswitch 42 and microswitches 44 and 46 respectively, thereby indicating the position of the shaft gear to motor control interface 25. 
     Referring to FIG. 5, recloser control device 12 may be attached to any standard manually operated recloser 15. To attach recloser control device 12, switch operating lever 16 is first removed and a shaft extender 31 is attached to the existing recloser shaft 29 to form operating shaft 28. One end of shaft extender 31 is configured to rigidly mount to the end of existing recloser shaft 29. Pin 35 may be attached to the ends of shaft extender 31 and existing recloser shaft 29 to maintain a rigid connection between the two shafts. Cover 11 of recloser control device 12 is removed and the control device is mounted to sleet hood 24 such that operating shaft 28 is inserted through shaft gear 30. Drive pin 50 is then attached to operating shaft 28 and mounting plate 26 is bolted to sleet hood 24. Cover 11 is mounted to mounting plate 26. Handle 16 may then be attached to shaft 28 opposite shaft 29. 
     Referring now to FIGS. 2, 3 and 4, the operation of the recloser device shall be explained. When a fault conditions occurs recloser 15 enters its open state, the current through the power lines is interrupted and operating shaft 28 rotates into its open state position. After the fault condition is cured, an operator at a site remote from the automatic recloser device will send an electrical signal down communication cable 18 to the recloser control device 12. The recloser control device will then engage motor 36 which in turn shall rotate gear 30. When gear 30 reaches the limit of its free rotation, it shall in turn cause the rotation of operating shaft 28 from its open position to its closed position. The microswitches sense the relative position of gear 30 and, when operating shaft 28 is in its closed configuration, control unit 25 stops motor 36. Control unit 25 then causes drive motor 36 to rotate gear 30 in the opposite direction until it reaches the limit of gear 30&#39;s free rotation relative to shaft 28. This will permit shaft 28 to freely rotate into its open configuration if an additional fault condition occurs. The remote operator may also wish to switch the recloser from its closed configuration to its open configuration simply by sending an appropriate signal down communication cable 18. This will cause control unit 25 to engage drive motor 36 so that drive motor 36 rotates gear 30 and thereby rotates shaft 28 from its closed position towards its open position. On occasion, a repair crew working close to the recloser may wish to switch the recloser either into its closed state or into its open state. The repair crew can switch the recloser by engaging switch lever 10. The fact that gear 30 can freely rotate about shaft 28 to within certain limits permits shaft 28 to move between its open position and its closed position without damaging either the shaft or drive motor 36. 
     The invention having been so described, certain modifications and adaptations will be obvious to those skilled in the art. The invention includes all such modifications and adaptations which follow in the scope of the appended claims.