Patent Publication Number: US-11657959-B2

Title: Spiral core current transformer for energy harvesting applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of provisional patent application Ser. No. 62/725,322, titled, Spiral Core Current Transformer For Energy Harvesting Applications, filed Aug. 31, 2018. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates generally to a current transformer assembly having a wound spiral core and, more particularly, to a current transformer assembly having a wound spiral core that is attachable to a connected power line. 
     Discussion of the Related Art 
     An electrical power network, often referred to as an electrical grid, typically includes a number of power generation plants each having a number of power generators, such as gas turbines, nuclear reactors, coal-fired generators, hydro-electric dams, etc. The power plants provide power at a variety of medium voltages that are then stepped up by transformers to a high voltage AC signal to be connected to high voltage transmission lines that deliver electrical power to a number of substations typically located within a community, where the voltage is stepped down to a medium voltage for distribution. The substations provide the medium voltage power to a number of three-phase feeders including three single-phase feeder lines that carry the same current, but are 120° apart in phase. A number of three-phase and single phase lateral lines are tapped off of the feeder that provide the medium voltage to various distribution transformers, where the voltage is stepped down to a low voltage and is provided to a number of loads, such as homes, businesses, etc. 
     It is known in the art to couple monitoring devices to the various feeder lines and lateral lines in an electrical power network to monitor current, voltage, power factures, temperature, etc. in the line so as to detect faults downstream of the device, which can be used to identify fault locations, help with protection schemes and perform load profiling. The monitoring devices typically employ current transformers having a secondary winding wound on a core that generates a current flow by magnetic induction coupling with the current traveling in the power line. This current flow is used to power the sensors and other electronics in the device, such as transmitters that wirelessly transmit the measurement signals to a control facility. 
     The current transformers include a central opening through which the power line travels. Thus, the power line needs to be positioned in the opening when the monitoring device is installed. However, it is costly, disruptive and impractical to disconnect the power line to pass the line through the opening. Therefore, split core current transformers are generally employed in these types of monitoring devices that have an air gap in the core of the transformer that allows the power line to be inserted into the core opening while it is connected. Once the power line is positioned within the core, a lineman will employ a hot stick to rotate a threaded engagement or other attachment device to close the core around the power line where it is securely fixed. However, because the current transformer has a split core with an air gap therein, the magnetic field lines traveling through the core when the transformer is carrying current are disrupted, which reduces the amount of power that is generated for powering electronics in the device. Therefore, because the split core transformer is only able to generate a reduced amount of power when compared to a solid core based on its size, the number and type of electronics within the device is also limited. 
     SUMMARY 
     The present disclosure describes a current transformer assembly for harvesting power from a primary conductor, such as a power line, for operating electronics, where the assembly is coupled to the conductor. The assembly includes a current transformer having a transformer structure with a central opening that accepts the primary conductor and a spindle member for accepting a current transformer including a lamination in a spiral shape form, such as a magnetic tape, operating as the core of the current transformer. The assembly also includes a tape carrier secured to the structure on which the transformer tape is wound, and a winding device operable to unwind the transformer magnetic tape from the tape carrier and wind the magnetic tape onto the spindle member. 
     Additional features of the present disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an isometric view of a current transformer assembly including a current transformer having a wound spiral core, where a power line travels through the transformer; 
         FIG.  2    is a broken-away isometric view of the current transformer assembly showing a spiral core lamination wound on a spindle; 
         FIG.  3    is a broken-away isometric view of the current transformer assembly showing the spiral core lamination wound around the power line; 
         FIG.  4    is a cut-away isometric view of the current transformer separated in the assembly shown in  FIG.  1   ; 
         FIG.  5    is a front view of a current transformer assembly including a current transformer and a detachable magnetic tape cartridge; 
         FIG.  6    is an exploded back isometric view of the current transformer assembly shown in  FIG.  5   ; 
         FIG.  7    is a front broken-away isometric view of the current transformer assembly shown in  FIG.  5   ; 
         FIG.  8    is an isometric view of a current transformer in the current transformer assembly shown in  FIG.  5    in an open configuration; 
         FIG.  9    is an isometric view of another current transformer assembly also including a current transformer and a detachable magnetic tape cartridge; 
         FIG.  10    is another isometric view of the current transformer assembly shown in  FIG.  9   ; 
         FIG.  11    is another isometric view of the current transformer assembly shown in  FIG.  9   ; 
         FIG.  12    is an isometric view of another current transformer assembly including a current transformer having a hinged outer structure; 
         FIG.  13    is a front view of the current transformer assembly shown in  FIG.  12    with the structure open and a power line extending therethrough; 
         FIG.  14    is an isometric view of the current transformer assembly shown in  FIG.  12    with the structure open and the power line extending therethrough; 
         FIG.  15    is an isometric view of the current transformer assembly shown in  FIG.  12    with the structure closed and the power line extending therethrough; and 
         FIG.  16    is a back view of the current transformer assembly shown in  FIG.  12    with the structure closed and the power line extending therethrough. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the disclosure directed to a current transformer assembly including a current transformer having a wound spiral core and being attachable to a connected power line is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses. For example, the discussion below describes the current transformer assembly as being installed on a power line without opening or de-energizing the line. However, as will be appreciated by those skilled in the art, the current transformer assembly of the disclosure may have other applications and uses. 
       FIG.  1    is an isometric view of a current transformer assembly  10  that is applicable to be installed on an electrical power line  12 , such as a power line in an electrical power network. The power line  12  is intended to represent any of the several types of power lines employed in electrical power networks, such as transmission lines, feeder lines, lateral lines, etc., which carry varying amounts of current and power, including high current. The assembly  10  includes an outer housing  14  mounted to a control box  20 , where the housing  14  includes a back housing panel  16  and a front housing panel  18  defining an enclosure  22 . The assembly  10  also includes a bracket  28  pivotally secured to the outer housing  14  that has cut-out sections  30  that accept the line  12  for securing the line  12  to the assembly  10 .  FIGS.  2  and  3    are isometric views of the assembly  10  with the front panel  18  removed to show the components therein, as described below. 
     The current transformer assembly  10  further includes a current transformer  32  having a secondary winding  34  and an open tube  36  extending across the center of the secondary winding  34  through which the power line  12  extends, where the tube  36  is rotatable within the secondary winding  34 , and where the line  12  is the primary conductor for the transformer  32 . Wires  40  are part of the secondary winding  34  and extend into the control box  20  to provide power to electronics therein. The tube  36  is rigidly secured to a circular plate  38  that is rotatably mounted within the housing  14  so that the tube  36  and the plate  48  rotate in combination. The outer housing  14  includes a slot  46 , the plate  38  includes a slot  48 , the secondary winding  34  includes an opening  50  and the tube  36  includes a slot  52  that all align with each other so as to allow the line  12  to be inserted into the tube  36  without disconnecting it. The bracket  28  is pivotally mounted to the housing  14  so that it can be positioned in an open position to expose the slots  46 ,  48  and  52  to accept the line  12 , as shown in  FIG.  2   , and a closed position to cover the slots  46 ,  48  and  52  and hold the line  12  in the tube  36 , as shown in  FIG.  3   . 
     A ferromagnetic lamination  60  made of a transformer core material having a high magnetic permeability, such as a suitable steel, having a certain thickness and length suitable for the size of the current transformer  32  is wound on a spindle  62  rigidly secured in the outer housing  14 , where one end of the lamination  60  is secured to the spindle  62 . The lamination  60  extends into a secondary winding opening  64 , where an opposite end of the lamination  60  is secured to the tube  36 . The assembly  10  is shown in this configuration in  FIG.  2   . 
     The current transformer assembly  10  includes a cylindrical winding device  70  that extends across the enclosure  22 , as shown, and that has gear teeth  72  that engage plate teeth  74  that are circumferentially disposed around the plate  38 . By rotating the device  70  using a key  76 , for example, through a special tool used by the lineman, the engagement of the teeth  72  and  74  causes the plate  38  and the tube  36  to rotate, which pulls on the lamination  60  and causes it to unwind from the spindle  62  and be wound onto the tube  36  to form the core of the transformer  32 . The assembly  10  is shown in this configuration in  FIG.  3   . 
       FIG.  4    is a broken-away, isometric view of the current transformer  32  separated from the current transformer assembly  10  showing the lamination  60  being wound within the secondary winding opening  64  to define a magnetic wound spiral core  80  having laminated layers. It is noted that the lamination  60  can be unwound from the tube  36  and wound onto the spindle  62  by turning the device  70  in an opposite direction in a similar manner. 
     The current transformer assembly  10  can include any suitable electronics provided in the control box  20  for any particular application that receive electrical power generated in the secondary winding  34  as a result of inductive coupling with the power line  12 . Example electronics include, but are not limited to, a current sensor, a temperature sensor, processing circuitry, a humidity sensor, a wireless transceiver, etc. 
     Once the lamination  60  has been wound onto the tube  36  in the secondary winding opening  64 , then the current transformer  32  is complete in that electrical current flowing in the power line  12  creates magnetic field lines in the wound core  80  that generate an electrical current in the secondary winding  34 . The number of the windings of the lamination  60  within the secondary winding opening  64  that form the core  80  would be determined for the particular application. The wound core  80  increases the power transfer efficiency from the power line  12  to the secondary winding  34  because the direction of the magnetic flux is the same as the winding direction of the lamination  60  within the secondary winding opening  64 . The wound core  80  also reduces losses due to Eddy currents because laminations are formed as the core  80  is wound. 
     The current transformer assembly  10  includes one embodiment for how the spiral core can be deployed in a current transformer that can be mounted to a power line for harvesting power therefrom of the type being discussed herein. Other embodiments showing how the spiral core can be deployed also may be applicable.  FIG.  5    is a front view,  FIG.  6    is an exploded back isometric view and  FIG.  7    is a front cut-away isometric view of a current transformer assembly  90  showing one such embodiment. The assembly  90  includes a current transformer  88  having a cylindrical housing  92  with a first housing half  94  and a second housing half  96  being pivotally mounted together by a torsional spring hinge  98  and defining a center opening  100  through which a power line  102  extends when the assembly  90  is in use.  FIG.  8    is an isometric view of the housing  92  in its open state to show how the housing halves  94  and  96  separate on the hinge  98  to secure the housing  92  to the power line  102 , where magnets (not shown) opposite to the hinge  98  can be employed to hold the housing halves  94  and  96  together and allow the halves  94  and  96  to be separated. A hook  106  is secured to and extends from the housing  92  to allow a lineman to remotely secure the assembly  90  to and remove the assembly  90  from the line  102 . A series of friction rollers  108  are secured to the housing  92  so that they extend into the opening  100  and contact the power line  102  to prevent the assembly  90  from rotating on the line  102 . The housing  92  includes a central chamber  110  that will accept a current transformer magnetic tape that is wound on a spindle  112  as will be discussed below. 
     Once the housing  92  is secured to the power line  102 , the lineman will then attach a cylindrical tape cartridge  120  to the housing  92 . The tape cartridge  120  includes a cartridge housing  122  defining a chamber  124  therein holding a tape winding  126  including a magnetic tape  118  wound on a rod  128  in the chamber  124  and a hook  116  that allows the lineman to hold the cartridge  120 . In this embodiment, magnetic pads  130  are secured to the housing  92  and the cartridge  120  includes magnets  132 , or another ferromagnetic material, extending from the housing  122  to allow the lineman to attach the cartridge  120  to the current transformer  88 . In this configuration, a slot  134  in the housing  92  aligns with a slot  136  in the housing  122 . A crank  138  extending from a back surface  140  of the housing  122  is attached to the rod  128  on which the winding  126  is wound so that rotation of the crank  138  in one direction causes the magnetic tape  118  to feed through the slots  134  and  136  so that the magnetic tape  118  is wound on the spindle  112  in the housing  92  and forms the core of the current transformer  88 . 
     The cartridge  120  can remain attached to the housing  92  where an end of the magnetic tape  118  remains secured to the rod  128  so that the magnetic tape  118  can be wound back on the rod  128  by rotating the crank  138  in the opposite direction to remove the magnetic tape  118  from the housing  92 . Alternately, the magnetic tape  118  can be completely wound in the housing  92  and the cartridge  120  removed therefrom, where the cartridge  120  can then be reloaded with another winding for installation on another current transformer. 
       FIGS.  9 ,  10  and  11    are isometric views of a current transformer assembly  150  that is similar to the assembly  90 , where like elements are identified by the same reference number. In this embodiment, the slot  134  in the housing  92  is replaced with a duct  152  and the cartridge  120  is replaced with a cartridge  154  including an outer housing  156  having the magnetic tape  118  wound therein. The housing  156  includes a duct  158  that is inserted into the duct  152  that not only provides a transition location for the magnetic tape  118  from the cartridge  154  to the housing  92 , but also allows the cartridge  154  to be secured to the housing  92 , by, for example, magnetic coupling or press fit. The cartridge  154  includes a spring follower  160  extending therethrough and the housing  156  includes a pair of tabs  162  having aligned through holes  164  on one side of the spring follower  160  and a pair of tabs  166  having aligned through holes  168  on an opposite side of the spring follower  160 . Alignment prongs  158  extend from the housing  156  around the spring follower  160 . 
     The assembly  150  also includes a plunger  170  having a head  172  and a rod  174 , where tabs  176  and  178  having holes  180  extend from an inside surface of the head  172  on opposite sides of the rod  174 . A compression spring  182  is slid onto the rod  174  and the rod  174  is inserted into the spring follower  160  so that the spring  182  is compressed between the head  172  and the housing  156 , as shown in  FIG.  11   . In this configuration, the tab  176  is positioned between the tabs  162  so that the holes  164  and  180  align and the tab  178  is positioned between the tabs  166  so that the holes  168  and  180  align. A compressible pull pin  184  is inserted into the holes  164 ,  168  and  180  to hold the spring  182  in compression and the magnetic tape  118  is loaded onto the spring follower  160  with spring tension. When the housing  92  is clasped onto the power line  102 , the pin  184  is pulled by, for example, a hot stick, and the spring  182  is released, which pushes the rod  174  out of the spring follower  160  causing it to rotate, which causes the magnetic tape  118  to be unwound from the spring follower  160  and wound onto the spindle  112  within the housing  92 . 
       FIG.  12    is an isometric view of a current transformer assembly  200  including an elliptical structure  202  defining a central opening  204 . The structure  202  includes an outer elliptical rail  206  and an inner elliptical rail  208  defining a gap  210  therebetween. The structure  202  is formed by a lower section  212 , a first side section  214  secured to the lower section  212  by a spring-loaded hinge  216  and a second side section  218  secured to the lower section  212  by a spring-loaded hinge  220 . The assembly  200  includes a snap rod  224  extending across the opening  204  to hold the structure  202  in the open position against the bias of the spring-loaded hinges  216  and  220 . When the rod  224  is removed the hinges  216  and  220  force the structure  202  closed so that a magnetic tab  230  on the first side section  214  is magnetically coupled to a magnetic tab  232  on the second side section  218  and the structure  202  is held closed. The assembly  200  further includes a frictional elastic band  234  coupled to band fasteners  236  and  238  secured to the lower section  212  so that the band  234  extends across the opening  204 . The assembly  200  also includes a roll  244  of current transformer magnetic tape  246  mounted to a tape carrier  248  secured to an outer surface  256  of the outer rail  206 , where the magnetic tape  246  is directed along the surface  256 , through a slot  250  in the outer rail  206  and into the gap  210 , as shown. A friction roller  252  is positioned in contact with the magnetic tape  246  and is rotated by a roller crank  254 . 
     The current transformer assembly  200  is secured to a power line  260  as follows. The assembly  200  is positioned by, for example, a hot stick or otherwise, so that the power line  260  is inserted between the sections  214  and  218  and into the opening  204  so that it snaps the rod  224 , as shown in  FIG.  13   . The power line  260  then contacts the band  234  pushing it downward, as shown in  FIG.  14   . At the same time, removal of the rod  224  allows the spring-loaded hinges  216  and  220  to close the structure  202  so that the magnetic tabs  230  and  232  engage and hold the structure  202  closed, where the power line  260  is securely held between the band  234  and the tabs  230  and  232 , as shown in  FIGS.  15  and  16   . The crank  254  is then rotated by the hot stick or otherwise so that that friction roller  252  pulls the magnetic tape  246  around the carrier  244  so that it is fed through the slot  250  in the outer rail  206  and into and around the gap  210  to surround the power line  260  as a transformer core. 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.