Patent Publication Number: US-2022216022-A1

Title: Switchgear with overmolded dielectric material

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to co-pending U.S. Provisional Patent Application No. 62/839,278, filed on Apr. 26, 2019, and to co-pending U.S. Provisional Patent Application No. 62/889,577, filed on Sep. 12, 2019, the entire contents of both of which are incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to solid dielectric switchgear, and more particularly to reclosers. 
     BACKGROUND OF THE DISCLOSURE 
     Reclosers are switchgear that provide line protection, for example, on overhead electrical power lines and/or substations and serve to segment the circuits into smaller sections, reducing the number of potentially impacted customers in the event of a short circuit. Previously, reclosers were controlled using hydraulics. More recently, solid dielectric reclosers have been developed for use at voltages up to 38 kV. Solid dielectric reclosers may be paired with electronic control devices to provide automation and “smart” recloser functionality. 
     SUMMARY OF THE DISCLOSURE 
     A need exists for fault protection and circuit segmentation in power transmission circuits, which typically operate at higher voltages (e.g., up to 1,100 kV). Reclosers allow for multiple automated attempts to clear temporary faults on overhead lines. In power transmission systems, this function is typically achieved using circuit breakers in substations. The present disclosure provides switchgear in the form of a recloser that can operate at voltages up to 72.5 kV. In some embodiments, the switchgear according to the present disclosure includes a vacuum interrupter assembly with a vacuum bottle and a sleeve over the vacuum bottle that allows for a more consistent seal when molding a dielectric material about the vacuum interrupter assembly (i.e., an overmold). 
     By providing a more consistent overmold, the present disclosure advantageously provides better over-current protection with reduced degradation over time, which provides better protection against arcing over the contacts of the vacuum interrupter. For example, the sleeve may help keep the dielectric material used in an overmolding process from entering gaps and/or cracks that may be present within and/or between components of the vacuum assembly. This reduces the number of customers or end users impacted by a potential fault and therefore improves the power transmission system&#39;s reliability. 
     The present disclosure provides, in one aspect, a switchgear apparatus configured for operation at voltages up to 72.5 kV, the switchgear apparatus including a vacuum interrupter assembly including a vacuum bottle having an upper portion and a lower potion, a sleeve surrounding the vacuum bottle, a dielectric material surrounding the sleeve, a first terminal electrically coupled to the upper portion of the vacuum interrupter assembly, and an interchange coupled to a lower portion of the vacuum interrupter assembly. The dielectric material is molded around the sleeve and around at least a portion of the first terminal or the interchange. In some embodiments, the sleeve is molded around the vacuum bottle. In other embodiments, the sleeve may be otherwise positioned (i.e., by sliding a pre-formed sleeve) around the vacuum bottle. 
     The present disclosure provides, in another aspect, a switchgear apparatus configured for operation at voltages up to 72.5 kV, the switchgear apparatus including a vacuum interrupter assembly including a vacuum bottle having an upper portion and a lower potion, and a fixed contact and a movable contact hermetically sealed within the vacuum bottle. The switchgear apparatus further includes a first terminal electrically coupled to fixed contact at the upper portion of the vacuum bottle, an interchange coupled to the movable contact at the lower portion of the vacuum bottle, a conductor electrically coupled to the interchange, a second terminal electrically coupled to the conductor, and a sensor assembly associated with the conductor. The sensor assembly includes at least one of a voltage sensor or a current sensor. An actuator assembly is operable to selectively break a conductive pathway between the first terminal and the second terminal by moving the movable contact from a closed position in which the movable contact engages the fixed contact to an open position in which the movable contact is spaced from the fixed contact. The actuator assembly includes a drive shaft configured to move the movable contact between the closed position and the open position, a magnet configured to maintain the drive shaft in a position corresponding with the closed position of the movable contact, and a dielectric material molded around the vacuum interrupter assembly. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a recloser and/or switchgear apparatus (“recloser”) according to an embodiment of the present disclosure. 
         FIG. 2  illustrates a cross-sectional view of the recloser of  FIG. 1 . 
         FIG. 3  illustrates a detailed, cross-sectional view of a top portion of the vacuum interrupter assembly of the recloser of  FIG. 1 . 
         FIG. 4  illustrates a detailed, cross-sectional view of a bottom portion of the vacuum interrupter assembly of the recloser of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Also, as used herein and in the appended claims, the terms “upper,” “lower,” “top,” “bottom,” “front,” “back,” and other directional terms are not intended to require any particular orientation, but are instead used for purposes of description only. 
       FIG. 1  illustrates a recloser  10  according to an embodiment of the present disclosure. The recloser  10  includes a housing assembly  14 , a vacuum interrupter (“VI”) assembly  18 , a conductor assembly  22 , which in some embodiments may be a load-side conductor assembly  22  and in other embodiments may be a source-side conductor assembly  22 , and an actuator assembly  26 . The VI assembly  18  includes a first terminal  30  extending from the housing assembly  14  along a first longitudinal axis  34 , and the conductor assembly  22  includes a second terminal  38  extending from the housing assembly  14  along a second longitudinal axis  42  perpendicular to the first longitudinal axis  34 . In other embodiments, the second longitudinal axis  42  may be obliquely oriented relative to the first longitudinal axis  34 . The actuator assembly  26  may operate the VI assembly  18  to selectively break and/or reestablish a conductive pathway between the first and second terminals  30 ,  38 . Although the recloser  10  is illustrated individually in  FIG. 1 , the recloser  10  may be part of a recloser system including a plurality of reclosers  10 , each associated with a different phase of a three-phase power transmission system and ganged together such that operation of the plurality of reclosers  10  is synchronized. 
     Referring now to  FIG. 2 , the illustrated housing assembly  14  includes a main housing  46  with an insulating material, such as epoxy, that forms a solid dielectric module  47 . The solid dielectric module  47  is preferably made of a silicone or cycloaliphatic epoxy. In other embodiments, the solid dielectric module  47  may be made of a fiberglass molding compound. In other embodiments, the solid dielectric module  47  may be made of other moldable dielectric materials. The main housing  46  may further include a protective layer  48  surrounding the solid dielectric module  47 . In some embodiments, the protective layer  48  withstands heavily polluted environments and serves as an additional dielectric material for the recloser  10 . In some embodiments, the protective layer  48  is made of silicone rubber that is overmolded onto the solid dielectric module  47 . In other embodiments, the protective layer  48  may be made of other moldable (and preferably resilient) dielectric materials, such as polyurethane. 
     With continued reference to  FIG. 2 , the main housing  46  includes a first bushing  50  that surrounds and at least partially encapsulates the VI assembly  18 , and a second bushing  54  that surrounds and at least partially encapsulates the conductor assembly  22 . The silicone rubber layer  48  includes a plurality of sheds  58  extending radially outward from both bushings  50 ,  54 . In other embodiments, the sheds  58  may be formed as part of the dielectric module  47  and covered by the silicone rubber layer  48 . In yet other embodiments, the sheds  58  may be omitted. The first and second bushings  50 ,  54  may be integrally formed together with the dielectric module  47  of the main housing  46  as a single monolithic structure. Alternatively, the first and second bushings  50 ,  54  may be formed separately and coupled to the main housing  46  in a variety of ways (e.g., via a threaded connection, snap-fit, etc.). 
     The illustrated VI assembly  18  includes a vacuum bottle  62  at least partially molded within the first bushing  50  of the main housing  46 . In some embodiments, the vacuum bottle  62  is additionally or alternatively pressed into the first bushing  50  of the main housing  46 . In some embodiments, the vacuum bottle  62  is surrounded by a sleeve  158 , which is preferably made of a resilient dielectric material such as silicone rubber. The vacuum bottle  62  encloses a movable contact  66  and a stationary contact  70  such that the movable contact  66  and the stationary contact  70  are hermetically sealed within the vacuum bottle  62 . The movable contact  66  is maintained in contact with an interchange  82  through the use of contact bands. Contact between the moveable contact  66  and the interchange  82  may be maintained through frictional contact. In some embodiments, (i) the sleeve  158  is molded around the VI assembly  18 , and includes silicone, (ii) the solid dielectric module  47  is molded around the sleeve  158 , and includes an epoxy, and (iii) the silicone rubber layer  48  is molded around the solid dielectric module  47 , and includes silicone. Such an embodiment including each of (i) to (iii) may be particularly advantageous in a high voltage (i.e., 72.5 kV) recloser to establish or break electrical contact within the VI assembly  18  because of the more consistent molding process provided by each of the overmolds (i) to (iii). 
     In some embodiments, the vacuum bottle  62  has an internal absolute pressure of about 1 millipascal or less. The movable contact  66  is movable along the first longitudinal axis  34  between a closed position (illustrated in  FIG. 2 ) and an open position (not shown) to selectively establish or break contact with the stationary contact  70 . The vacuum bottle  62  quickly suppresses electrical arcing, for example suppression may occur in less than 30 milliseconds, that may occur when the contacts  66 ,  70  are opened due to the lack of conductive atmosphere within the bottle  62 . In some embodiments, the vacuum bottle  62  suppresses electrical arcing in a time of between about 8 milliseconds and about 30 milliseconds. 
     The conductor assembly  22  may include a conductor  74  and a sensor assembly  78 , each at least partially molded within the second bushing  54  of the main housing  46 . The sensor assembly  78  may include a current sensor, a voltage sensor, partial discharge sensor, voltage indicated sensor, and/or other sensing devices. One end of the conductor  74  is electrically coupled to the movable contact  66  via the current interchange  82 . The opposite end of the conductor  74  is electrically coupled to the second terminal  38 . The first terminal  30  is electrically coupled to the stationary contact  70 . The first terminal  30  and the second terminal  38  are configured for connection to respective electrical power transmission lines. 
     With continued reference to  FIG. 2 , the actuator assembly  26  includes a drive shaft  86  extending through the main housing  46  and coupled at one end to the movable contact  66  of the VI assembly  18 . In the illustrated embodiment, the drive shaft  86  is coupled to the movable contact  66  via an encapsulated spring  90  to permit limited relative movement between the drive shaft  86  and the movable contact  66 . The encapsulated spring  90  biases the movable contact  66  toward the stationary contact  70 . The opposite end of the drive shaft  86  is coupled to an output shaft  94  of an electromagnetic actuator  98 . The electromagnetic actuator  98  is operable to move the drive shaft  86  along the first longitudinal axis  34  and thereby move the movable contact  66  relative to the stationary contact  70 . In additional or alternative embodiments, the functionality provided by the encapsulated spring  90  may be provided with an external spring and/or a spring positioned otherwise along the drive shaft  86 . For example, the spring may be instead positioned at a first end or at a second end of the drive shaft  86 . 
     The electromagnetic actuator  98  in the illustrated embodiment includes a coil  99 , a permanent magnet  100 , and a spring  101 . The coil  99  includes one or more copper windings which, when energized, produce a magnetic field that acts on the output shaft  94 . The permanent magnet  100  is configured to hold the output shaft  94  in a position corresponding with the closed position of the movable contact  66 . The spring  101  biases the output shaft  94  in an opening direction (i.e. downward in the orientation of  FIG. 2 ). In some embodiments, the actuator assembly  26  may include other actuator configurations. For example, in some embodiments, the permanent magnet  100  may be omitted, and the output shaft  94  may be latched in the closed position in other ways. In additional or alternative embodiments, the electromagnetic actuator  98  may be omitted. 
     The actuator assembly  26  includes a controller (not shown) that controls operation of the electromagnetic actuator  98 . In some embodiments, the controller receives feedback from the sensor assembly  78  and energizes or de-energizes the electromagnetic actuator  98  in response to one or more sensed conditions. For example, the controller may receive feedback from the sensor assembly  78  indicating that a fault has occurred. In response, the controller may control the electromagnetic actuator  98  to automatically open the VI assembly  18  and break the circuit. The controller may also control the electromagnetic actuator  98  to automatically close the VI assembly  18  once the fault has been cleared (e.g., as indicated by the sensor assembly  78 ). 
     In the exemplary illustrated embodiment, the actuator assembly  26  further includes a manual trip assembly  102  that can be used to manually open the VI assembly  18  through the operation of the drive shaft  86  and/or other linkages. The manual trip assembly  102  includes a handle  104  accessible from an exterior of the housing assembly  14  (as shown in  FIG. 1 ). The handle  104  is rotatable to move a yoke  106  inside the housing assembly  14  (as shown in  FIG. 2 ). The yoke  106  is engageable with a collar  110  on the output shaft  94  to move the movable contact  66  toward the open position. The illustrated housing assembly  14  includes an actuator housing  114  enclosing the electromagnetic actuator  98  and a head casting  118  coupled between the actuator housing  114  and the main housing  46 . The manual trip assembly  102  is supported by the head casting  118 , and the output shaft  94  extends through the head casting  118  to the drive shaft  86 . 
     Referring now to  FIG. 3 , a detailed, cross-sectional view of a top portion of the VI assembly  18  of the recloser  10  is shown. The sleeve  158  is shown positioned around the vacuum bottle  62 . The first terminal  30  is seated against the sleeve  158  at an upper connection point  151  within the first bushing  50 . The sleeve  158  is compressed between the first terminal  30  and the top of the vacuum bottle  62  to form a complete seal between the first terminal  30  and the vacuum bottle  62 . In the illustrated embodiment, the upper connection point  151  between the first terminal  30  and the sleeve  158  is completely molded (i.e., entirely surrounded in molding) within dielectric material  152  of the dielectric module  47  (cross-hatching of the dielectric material  152  is omitted from  FIG. 3  for the purpose of more clearly illustrating the sleeve  158 ). In other words, the upper connection point  151  is entirely encapsulated by the dielectric material  152 . 
     In additional and/or alternative embodiments, a method related to the structure disclosed herein may include providing the vacuum bottle  62  and the first terminal  30 , positioning the sleeve  158  about the vacuum bottle  62 , positioning the first terminal  30  against a portion of the sleeve  158  surrounding an opening of the vacuum bottle  62 , and compressing the portion of the sleeve  158  between the first terminal  30  and the vacuum bottle  62  to form a seal between the first terminal  30  and the vacuum bottle  62 . A contact area between the sleeve  158  and the first terminal  30  is the upper connection point  151 . The method may further include encapsulating at least the upper connection point  151  by molding the dielectric material  152  over at least the upper connection point  151 . Such a configuration and/or method may advantageously inhibit creepage and tracking from the VI assembly  18 . In some embodiments, the sleeve  158  may be compressed before, during, and/or after molding the dielectric material  152 . 
     Referring now to  FIG. 4 , a detailed, cross-sectional view of a bottom portion of the VI assembly  18  of the recloser  10  of  FIG. 1  is illustrated. As shown, the interchange  82  is positioned to interact with an interchange terminal  153  along the first longitudinal axis  34  (and configured to connect to the movable contact  66 , shown in  FIG. 2 ) and the connector  74  along the second longitudinal axis  42 . The interchange  82  connects to the sleeve  158  positioned about the vacuum bottle  62  at a lower connection point  156 . 
     In the illustrated embodiment, the sleeve  158  includes at least one ridge  157  integrally formed with the sleeve  158  and surrounding the circumference of the sleeve  158  at the lower connection point  156 . The interchange  82  may include a mating feature (e.g., one or more ridges, grooves, or the like) configured to cooperate with the ridge  157  on the sleeve  158  to form a seal between the vacuum bottle  62  and the interchange  82  at the lower connection point  156 . In the illustrated embodiment, the lower connection point  156  is completely molded (i.e., entirely surrounded in molding) with the dielectric material  152  (cross-hatching of the dielectric material  152  is again omitted from  FIG. 4  for the purpose of clarity). In other words, the lower connection point  156  is entirely encapsulated by the dielectric material  152 . 
     For example, in additional and/or alternative preferred embodiments, a method related to the structure disclosed herein may include providing the vacuum bottle  62  within the sleeve  158  and the interchange  82 , positioning a portion of the sleeve  158  around an opening of the vacuum bottle  62  against and/or partially within the interchange  82  such that the ridge  157  is located between the sleeve  158  and the interchange  82 , and molding the dielectric material  152  over the sleeve  158  and the interchange  82 . Such a configuration and/or method may advantageously prevent the dielectric material  152  (e.g., epoxy) from leaking into the connection between the vacuum bottle  62  and the interchange  82  during molding. In addition, by sealing between the vacuum bottle  62  and the interchange  82 , the sleeve  158  may also inhibit creepage and tracking from the VI assembly  18  at the lower connection point  156 . 
     An exemplary operating sequence of the recloser  10  according to certain embodiments of the present disclosure will now be described with reference to  FIG. 2 . During operation, the controller of the recloser  10  may receive feedback from the sensor assembly  78  indicating that a fault has occurred. In response to this feedback, the controller automatically energizes the coil  99  of the electromagnetic actuator  98 . The resultant magnetic field generated by the coil  99  moves the output shaft  94  in an opening direction (i.e. downward in the orientation of  FIG. 2 ). This movement creates an air gap between the output shaft  94  and the permanent magnet  100  that greatly reduces the holding force of the permanent magnet  100 . With the holding force of the permanent magnet  100  reduced, the spring  101  is able to overcome the holding force of the permanent magnet  100  and accelerate the output shaft  94  in the opening direction. As such, the coil  99  is only required to be energized momentarily to initiate movement of the output shaft  94 , advantageously reducing the power drawn by the electromagnetic actuator  98  and minimizing heating of the coil  99 . 
     The output shaft  94  moves the drive shaft  86  in the opening direction. As the drive shaft  86  moves in the opening direction, the encapsulated spring  90 , which is compressed when the contacts  66 ,  70  are closed, begins to expand. The spring  90  thus initially permits the drive shaft  86  to move in the opening direction relative to the movable contact  66  and maintains the movable contact  66  in fixed electrical contact with the stationary contact  70 . As the drive shaft  86  continues to move and accelerate in the opening direction under the influence of the spring  101 , the spring  90  reaches a fully expanded state. When the spring  90  reaches the fully expanded state, the downward movement of the drive shaft  86  is abruptly transferred to the movable contact  66 . This separates the movable contact  66  from the stationary contact  70  and reduces arcing that may occur upon separating the contacts  66 ,  70 . The movable contact may be separated in a time of between 8 milliseconds and 30 milliseconds. By quickly separating the contacts  66 ,  70 , degradation of contacts  66 ,  70  due to arcing is reduced, and the reliability of the VI assembly  18  is improved. 
     Thus, the present disclosure provides a high voltage recloser  10  suitable for use in power transmission applications up to 72.5 kV. The VI assembly  18  quickly and reliably suppresses arcing without the need for an oil tank or a gas-filled container containing sulphur hexafluoride (SF6), which is a potent greenhouse gas. In addition, the VI assembly  18  disclosed herein is advantageously maintenance free. 
     Various features and advantages of the invention are set forth in the following claims.