Abstract:
Disclosed is a power line broadband communication system having broadband coupler devices capable of direct electrical connection to an energized power line. The coupler includes a conductive portion movable by an adjustable member from a non-conducting retracted position spaced apart from the power transmission line to a forward conducting position in electrical contact with the power line. An insulated arm supports the coupler on the power line. A base on the coupler is engageable with a remotely activated tool in order to accomplish the electrical connection in a safe and secure manner. Broadband data signals are sent to and from customer premises along the shared energized power lines. New coupler connections to the energized power lines allow the additional broadband customers and/or repeaters to join the communication system. Also couplers may provide connections to control electronics, routers, wireless transceivers, and may allow the broadband signals to bypass transformers on the power lines. The invention helps to minimize risk by allowing an installer to be remotely spaced from the energized power line while making the electrical coupling contact with the energized power line.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application relates generally to data transmission, and more particularly to data transmission over power lines.  
         [0002]     The use of power lines to transmit data is known. Initially, power line communication systems were limited to relatively low data rates, typically less than 500 kbs. These low data rates are generally useful for applications such as remote control of various switches connected to the power line system. More recently, developments have been made in the area of broadband power line communication systems, also known as power line telecommunications (PLT) systems or broadband power line (BPL) systems. These systems are capable of transmitting data at significantly higher data rates than previous systems. For example, BPL systems can transmit data at rates of 4-20 Mbps.  
         [0003]     While existing power line systems are capable of transmitting data at the rates described above, they were not initially designed for data transmission. Instead, they were designed to carry large currents at high voltages so that significant amounts of energy could be distributed at one primary low frequency (e.g., 60 Hertz).  
         [0004]     Power line communication systems generally use one or more carrier frequencies in order to spread the data transmission over a wider range of frequencies. The low data rate power line communication systems discussed above generally utilized frequencies in the range of 9 kHz to 525 kHz. In this frequency range the risk of emissions is low as the attenuation of the cable is low and the wavelengths used in the signaling are long with respect to the typical cable lengths in the system. However, the high data rates of BPL systems cannot be achieved using carrier frequencies below 525 kHz. Instead, BPL systems typically use carrier frequencies in the range of 1-30 MHz. At these higher frequencies, it is preferable to employ capacitive coupling rather than inductive coupling in order to implement a broadband communication system using power line cables.  
         [0005]     Providing an electrical coupling to medium voltage (MV) and low voltage (LV) power lines as part of a broadband communication system is a dangerous task. Also the coupling must be made secure to withstand hostile weather conditions and to provide reliable communication services. Previous attempts to install such a coupling as part of a capacitive coupling circuit have relied on highly trained and skilled installation personnel. New customer interconnections as well as periodic interconnections with auxiliary electronics such as repeaters, routers, etc. must be done at various points along energized power lines without incurring risk of injury or disruption of both power transmission and broadband communications. There is an important need to develop a technique for providing such interconnections at a safe distance spaced from the energized power lines.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The invention provides a power line broadband communication system having broadband coupler devices capable of direct electrical connection to an energized power line without creating unreasonable safety risks.  
         [0007]     Various embodiments of the invention include a conductive portion movable from a non-conducting retracted position spaced apart from the power transmission line to a forward conducting position in electrical contact with the power line. An insulated arm supports the coupler on the power line. In some embodiments a base of an adjustable member on the coupler is engageable with a remotely activated tool in order to accomplish the electrical connection in a safe and secure manner.  
         [0008]     Generally speaking the invention enables broadband data signals to be sent to and from existing and new customer premises along the shared energized power lines. New coupler connections to the energized power lines allow additional broadband customers to join the communication system. Also couplers may provide power line connections to other components such as to repeater control electronics for the broadband signals, to signal routers, and to transformer bypass circuits.  
         [0009]     In accordance with some embodiments of the invention, a method for facilitating broadband electrical transmissions on a power line includes placing a coupler device on an energized power line in a self-supporting position, engaging the coupler device from a location spaced apart from the energized power line to cause a conductive portion of the coupler device to make electrical metallic contact with the power line, and transmitting data signals through the coupler device via the energized power line.  
         [0010]     In one embodiment the coupler device carries signals to and from transceivers associated with customer premises. Such transceivers may have wired connections via transformer bypass router lines to and from customer premises. Other exemplary transceivers may be wireless transceivers that eliminate any need for a transformer bypass line.  
         [0011]     In other embodiments the coupler device may provide a direct connection to energized power lines from electronic signal control devices. Signal repeaters are an example of such devices that can be connected to an MV line through a coupler installation device incorporating features of the invention.  
         [0012]     Exemplary coupler device embodiments may include a hanger fixture having a first insulated end capable of self-supporting contact with a power line cable, and a second conductive end adjustably movable relative to the power line cable. Secure attachment may be accomplished after electrical contact has been made between the conductive end and the power line cable by a compressive force exerted by an adjustment bolt or screw holding the power line cable between the first and second ends of the hanger fixture.  
         [0013]     In some embodiments the first end of the coupler device includes a U-shaped portion for partially surrounding the power line cable, and the adjustment bolt or screw may be incorporated as part of the second conductive end of the fixture and may have a sharp edge or point for making metallic electrical contact with the power line cable. In some embodiments the adjustment bolt or screw may cause closure of the coupler device to prevent the coupler from becoming disengaged from the power line cable.  
         [0014]     One aspect of the invention includes moving the conductive portion from the retracted position with an insulated tool that is activated remotely to engage an adjustment portion of the coupler.  
         [0015]     In some embodiments, the conductive portion of the coupler is connected to a broadband signal line through a capacitor. The technique of the present invention as implemented in certain embodiments helps to make capacitive coupling cost competitive with inductive coupling, thereby taking advantage of the fact that capacitive coupling is more efficient for broadband signals. The impedance of a capacitive coupler (i.e., its ability to obstruct the flow of signal energy) decrease with signal frequency. With an inductive coupler, the impedance increase with frequency. Thus the capacitive coupler is better suited to cases where we want to use high-frequency broadband signals.  
         [0016]     Because a capacitive coupler device requires direct electric conductive contact with an energized power line, the coupler installation device and method of the present invention greatly facilitate the capability of enjoying the benefits of capacitive coupling for broadband power line communication systems as compared with inductive coupling.  
         [0017]     These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a broadband power line communication system for implementing various features of the invention.  
         [0019]      FIG. 2  is a schematic illustration showing an exemplary power line communication system embodiment of the invention.  
         [0020]      FIG. 3  shows an exemplary embodiment of a coupling device for connection to a power line communication system.  
         [0021]      FIGS. 4A and 4B  show exemplary techniques for using features of the invention to make an electrical connection at different angular orientations directly to an energized communication power line.  
         [0022]      FIGS. 5A and 5B  show additional exemplary techniques for using a coupling device to make an electrical connection directly to an energized communication power line.  
         [0023]      FIGS. 6A and 6B  show fragmentary views of other coupling device embodiments that facilitate electrical connections to an energized communication power line.  
         [0024]      FIG. 7  shows a fragmentary view of another coupling device embodiment.  
         [0025]      FIG. 8  shows a fragmentary view of a different coupling device embodiment in closed conductive position, with an open position of the coupling device shown in phantom. 
     
    
     DETAILED DESCRIPTION  
       [0026]     A typical power line communication system for implementing features of the invention is shown in  FIG. 1 . A high voltage (HV) power line  102  transmits power through sub-station  104  to a medium voltage (MV) power line  106  that eventually may connect through a transformer  108  to low voltage (LV) lines  110  that provide alternating electrical power to customer premises  111 ,  112 ,  113 . A wireless connection through transceiver  107  may provide an alternative connection to customer premises  109 .  
         [0027]     A head end data network provides communication signals  120  via a fiber optic cable or other suitable transmission links to the end user customer premises  111 ,  112 ,  113  using power line cables as the transmission medium. Techniques for converting data signals to the electrical domain for transmission via the power lines are well known. A transmitter contains a modulator which modulates the incoming data onto a carrier signal using well known RF modulation techniques. As described above, typical carrier frequencies for a power line communication system are in the range of 1-30 MHz. The modulated signal is provided to the power line cable  106  via couplers  122 .  
         [0028]     It will be understood by those skilled in the art that a signal on an optical cable must first be converted to an electrical signal, then reformatted (demodulated-remodulated) to a format appropriate for transmission on a power line (e.g., OFDM). Such a modulated and reformatted signal can then be coupled by the present invention onto a power line as shown at coupler connections  122 .  
         [0029]     A power line communication system of the type shown in  FIG. 1  may use orthogonal frequency division multiplexing (OFDM) in which the available bandwidth is split up into multiple narrowband channels which do not interfere with each other. However the present invention is applicable to any type of power line communication system such as OFDM, a spread-spectrum system, etc. Thus, in accordance with any appropriate BPL system, broadband signals are carried over the MV line  106  and optionally LV lines  110  to receivers at the customer premises  111 ,  112 ,  113 , or via MV line  106  through wireless transceiver  107  to customer premises  109 .  
         [0030]     For purposes of the present description, it is assumed that the MV power line cable  106  will typically supply power at 4-66 kV. Such medium voltage cable is typically an aluminum cable having a 1 cm diameter. Couplers  122  provide an interconnection for the modulated carrier signal to the MV line  106 . Various types of couplers are known in the art, including for example inductive couplers and capacitive couplers. The carrier signal is transmitted along the length of MV power line cable  106  through transformers  108  to LV lines  110 . The low voltage power line typically supplies power at 100-240 volts. The low voltage line transmits the data signals to the customer premises  111 ,  112 ,  113  where a modem demodulates the signal and extracts the data message.  
         [0031]     It is noted that for ease of description only downstream (i.e., from head end to end user) data transmission is shown and described. One skilled in the art would readily recognize that upstream transmission could be accomplished in a similar manner.  
         [0032]     As described above in the background section, there is a significant problem with safety risks in providing broadband coupler connections directly to an energized power line.  
         [0033]     As shown in the embodiment of  FIG. 1 , the MV line  106  may connect through MV couplers  124  to signal repeater electronics  126 . Providing a repeater connection to a MV power line is an important application in some embodiments of the invention.  
         [0034]     The MV line  106  may also connect through MV coupler  128  via bypass router  130  to LV coupler  132  in order to achieve data signal transfer to an LV power line  110 . Router  136  interconnects with LV power line  110  at LV coupler  134  in order to selectively deliver appropriately addressed data signals to receivers at either customer premises  112  or customer premises  113 . The coupler installation of the invention can be incorporated at high risk MV coupler connection  128 , and also at lower risk LV coupler connections  132 ,  134 , although installation at these LV points does not pose the high safety risk associated with installation on MV lines  
         [0035]     The MV line  106  may also connect through MV coupler  142  via bypass router  144  to LV coupler  146  in order to achieve data signal transfer to an LV power line  110 . Router  140  interconnects with MV power line  106  at MV coupler  138  in order to selectively deliver appropriately addressed data signals via wireless transceiver  107  to customer premises  109 . Using such a wireless transceiver, as for example a WiFi access point, makes it unnecessary to provide a transformer bypass path for the broadband signal. The coupler installation of the invention can be incorporated at high risk MV coupler connections  138 ,  142 , and also at lower risk LV coupler connection  146 .  
         [0036]      FIG. 2  is a high level schematic diagram showing exemplary locations for installing a coupler device on a power line communication system. Although most present day power lines transmit alternating current (AC), the invention is applicable to both AC and DC (direct current) power line systems. Utility poles  220  support MV lines  202  and LV lines  204  at a safe distance from the ground. Implementing a communication system on the power lines typically requires electronic components  206 ,  208 ,  210 ,  214 ,  216  including capacitors  212 ,  218  in order to assure satisfactory transmission of broadband signals to customers  224 . The invention provides a safe, secure and reliable coupling technique for making electrical interconnections to high risk MV lines at coupling locations  220 , as well as to lower risk LV lines at coupling locations  222 .  
         [0037]     The embodiment of  FIG. 3  shows an exemplary coupler device  300  having an insulated portion  302  and a conductive portion  304  connected through link  306  via capacitor  308  to electronic components  310 . A threaded sleeve  312  receives a conductive adjustment screw  313  with threads  314 . The adjustment screw  313  has a contact point  316  for electrical contact with a power line cable (not shown). An insulated tool  320 , as for example a tool known in the trade as a hotstick, includes a long extension  322  having a cap  324  sized and shaped for engagement with the adjustment screw  313 . An installer can grasp a handle  326  at a location remote from high risk MV or lower risk LV power cables and actuate the tool such as by rotation in direction  328 .  
         [0038]     The insulated portion  302  of the coupler  300  may have a hook-shaped end  334  formed by extension  330  and truncated end  336 . A leg portion  332  provides an attachment junction with the conductive portion  304 . The overall contours of the insulated portion  302  may be U-shaped in order to provide multiple interior contact surfaces  338 ,  340 ,  324  for contacting adjacent surfaces of a power line cable in order to support the coupler when the adjustment screw  313  is in open position, as well as to securely establish electrical contact and maintain attachment to the power cable when the adjustment screw  313  is in closed position. Other hook-like shapes may be incorporated in the insulated portion  302  in order to partially surround the power cable and maintain the coupler  300  in self-supporting position during initial coupler installation as well as during actuation of the tool to accomplish electrical contact between the conductive portion  304  and the energized power cable.  
         [0039]     Of course, the benefits of the invention can be achieved with other adjustment members which perform a similar function to the adjustment screw  313  so that the coupler can have a conductive component remotely actuated from a retracted position to a forward conducting position while the coupler remains in self-supporting position on the power cable.  
         [0040]     It will be understood by those skilled in the art that various angular orientations of a coupler fixture and its conductive element relative to a power line cable are possible in order to achieve the goals of the present invention. For example, in  FIG. 4A , a conductive adjustment screw  404  has a tapered head  406  with a central contact point  408  and is shown facing upwardly in a vertical direction for making electrical contact with power cable  400 . A coupler having contact surfaces approximately coincident with plane  410  will apply compressive forces in a direction  412  in order to help maintain such electrical contact and hold the coupler in secure position on the power cable. A conductive adjustment screw  414  has a tapered head  416  with a central contact point  418  and is shown facing laterally in a horizontal direction for making electrical contact with power cable  400 . A coupler having contact surfaces approximately coincident with plane  420  will apply compressive forces in a direction  422  in order to help maintain such electrical contact and hold the coupler in secure position on the power cable. A conductive adjustment screw  424  has a tapered head  426  with a central contact point  428  and is shown facing partially upwardly in a somewhat oblique angular direction for making electrical contact with power cable  400 . A coupler having contact surfaces approximately coincident with plane  430  will apply compressive forces in a direction  432  in order to help maintain such electrical contact and hold the coupler in secure position on the power cable.  
         [0041]     Similar orientations are illustrated in  FIG. 4B  for non-tapered heads respectively having sharp peripheral edge contact surfaces  438 ,  448 ,  458 . Compressive forces applied perpendicular to planes  410 ,  420 ,  430  will maintain electrical contact with adjustment screws  436 ,  446 ,  456  respectively, and hold the coupler in secure position on the power cable.  
         [0042]     Referring to  FIGS. 5A and 5B , a coupler device is shown in closed position with a conductive portion in electric metallic contact with a power line cable  400 . In these embodiments, a U-shaped insulated coupler arm  334  includes an elongated extension  330  and a shortened extension such as truncated end  336 . An adjustment shaft in the form shown as threaded adjustment screw  313  makes electrical contact and also applies compressive forces to hold the power line cable  400  in secure position against the U-shaped insulated coupler arm  334 .  
         [0043]     In  FIG. 5A  a central contact point  316  on the apex of the adjustment screw  313  makes the electrical contact. In  FIG. 5B  a sharpened circular peripheral edge  416  on the apex of the adjustment screw  31  makes the electrical contact. Various other shapes and type of sharp contact edges or points may be used in order to penetrate any weather coating or other surface material on the power line cable and make the appropriate metallic contact for transmitting message and control signals between the coupler and the power line cable.  
         [0044]     Additional embodiments for facilitating engagement of a self-supported coupling device on a power line are shown in  FIGS. 6A and 6B . Referring to  FIG. 6A , an insulated arm  600  includes elongated extension  602 , header  604  and shortened extension  606  which together form a rectangular-shaped hook having a central concave recess  608  shaped and sized to provide support on a power line cable  611 . A threaded conductor shaft  613  is shown in partially closed position with its tapered head  615  starting to penetrate an outer insulation layer prior to making electrical contact with the power line cable  611  (see  FIG. 4A ).  
         [0045]     Referring to  FIG. 6B , an insulated arm  610  includes shortened extension  612 , header  614  and elongated extension  616  which together form a rectangular-shaped hook having a triangular slot  618  to provide support on a power line cable  611 . The threaded conductor shaft  613  is shown in partially closed position similar to  FIG. 6A .  
         [0046]     Referring to the embodiment of  FIG. 7 , a mechanical fixture assembly includes a coupler device  740  shown in a self-supporting position on a power line  700 , and also includes a remotely activated insulated tool  722  that has been manually engaged with the coupler device  740 . The insulated tool  722  has a cap  724  sized and shaped to fit an enlarged base  726  of a threaded shaft  728  on the coupler device  740 . After an installer has manually rotated a handle  727  remotely located from the power line  700  in order to advance the threaded shaft  728  forwardly, a sharpened point  730  on an apex of the shaft advances from a partially closed position making initial contact with an insulation layer as shown in the drawing until the insulation layer is penetrated and electrical metallic contact is made directly with the power line (see  FIG. 4A ).  
         [0047]     The threaded shaft and its adjacent threaded base  732  together constitute a conductor portion of the coupler device for carrying signals to and fro between line  734  and power line  700 . In this embodiment, an insulated arm is formed by a first extension  742  connected at its lower end to the base  732 , and is joined at its upper end  748  to angular extension  744  to form a triangular recess  745  for supporting the coupler device on the power line  700 . A lower leg portion  746  on the angular extension  744  along with interior contact surfaces  750 ,  752  help to assure the coupler device  740  remains in self-supporting position on the power line  700  upon initial installation of the coupler device and during adjustment of threaded shaft  728  into conducting position by insulated tool  722 .  
         [0048]     In view of the foregoing description and drawings of exemplary embodiments, it will be understood by those skilled in the art that variously shaped coupler devices with differently shaped interior contact surfaces can be utilized in order to maintain the coupler device in a somewhat stable self-supporting position on a power cable during the various stages of installation. In some instances, the corresponding mass of each portion of the exemplary coupler devices shown in the various drawing figures may if necessary be counter-balanced in order to help the coupler device remain self-positioned, such as when an adjustment member such as a threaded shaft is in retracted open position as well as when an adjustment member is moved into closed position such as during rotation of the threaded shaft by the remotely positioned installer.  
         [0049]     Referring to the embodiment of  FIG. 8 , a power line  800  is shown in an engaged position with a closed fully installed coupler device  840  comprising another mechanical fixture. A conductor shaft  820  has an upper end  822  tapered to form a sharpened central point  824 , the shaft being formed integral with a conductor plate  826  connected to signal line  828 . A separate bolt  830  that may be formed with a dielectric material has a threaded upper end  836  that engages a matching threaded sleeve  838  on a U-shaped insulated arm  840 . Rotation of the bolt by a remotely activated tool (not shown in this drawing) advances the conductor plate  826  and conductor shaft  820  forwardly into closed position to provide electrical metallic contact of the central point  824  with the power line  800 , as shown in the drawing. Rotation of the bolt  830  is facilitated by a raised low-friction boss  834  on the underside of conductor plate  826 .  
         [0050]     When the conductor plate is moved to a closed position as shown by arrow  846 , the insulated arm  840  has a lower leg  842  abutting an end  844  of the conductor plate  825  in order to eliminate an initial installation gap. When the coupler device is in open position as shown in phantom at  848 , the initial installation gap allows insertion of the power line  800  inside of the U-shaped insulated arm. The upper part of the U-shaped insulated arm  840  provides a recess for holding the coupler device in self-supporting position on the power line  800 .  
         [0051]     In view of all the foregoing, it will be understood by those skilled in the art that various embodiments of the invention enable and facilitate implementation of a broadband communication system on energized power lines by various installation methods including but not limited to one or more of the following techniques: making multiple connections to power lines through individual coupler devices in order to bypass transformers connecting LV customer premises to shared power lines; or making multiple connections to power lines through wireless transceivers in order to connect customer premises to shared power lines; or making multiple connections to power lines through capacitive coupler devices in order to connect customer premises to shared power lines; or connecting repeater electronics to MV power lines in order to facilitate broadband signal transmission on shared power lines to customer premises; or connecting routers to LV or MV power lines in order to direct delivery of data messages to appropriate customer premises.  
         [0052]     The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.