Broadband coupler technique for electrical connection to power lines

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.

BACKGROUND OF THE INVENTION

This application relates generally to data transmission, and more particularly to data transmission over power lines.

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.

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).

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

DETAILED DESCRIPTION

A typical power line communication system for implementing features of the invention is shown inFIG. 1. A high voltage (HV) power line102transmits power through sub-station104to a medium voltage (MV) power line106that eventually may connect through a transformer108to low voltage (LV) lines110that provide alternating electrical power to customer premises111,112,113. A wireless connection through transceiver107may provide an alternative connection to customer premises109.

A head end data network provides communication signals120via a fiber optic cable or other suitable transmission links to the end user customer premises111,112,113using 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 cable106via couplers122.

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 connections122.

A power line communication system of the type shown inFIG. 1may 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 line106and optionally LV lines110to receivers at the customer premises111,112,113, or via MV line106through wireless transceiver107to customer premises109.

For purposes of the present description, it is assumed that the MV power line cable106will typically supply power at 4–66 kV. Such medium voltage cable is typically an aluminum cable having a 1 cm diameter. Couplers122provide an interconnection for the modulated carrier signal to the MV line106. 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 cable106through transformers108to LV lines110. The low voltage power line typically supplies power at 100–240 volts. The low voltage line transmits the data signals to the customer premises111,112,113where a modem demodulates the signal and extracts the data message.

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.

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.

As shown in the embodiment ofFIG. 1, the MV line106may connect through MV couplers124to signal repeater electronics126. Providing a repeater connection to a MV power line is an important application in some embodiments of the invention.

The MV line106may also connect through MV coupler128via bypass router130to LV coupler132in order to achieve data signal transfer to an LV power line110. Router136interconnects with LV power line110at LV coupler134in order to selectively deliver appropriately addressed data signals to receivers at either customer premises112or customer premises113. The coupler installation of the invention can be incorporated at high risk MV coupler connection128, and also at lower risk LV coupler connections132,134, although installation at these LV points does not pose the high safety risk associated with installation on MV lines

The MV line106may also connect through MV coupler142via bypass router144to LV coupler146in order to achieve data signal transfer to an LV power line110. Router140interconnects with MV power line106at MV coupler138in order to selectively deliver appropriately addressed data signals via wireless transceiver107to customer premises109. 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 connections138,142, and also at lower risk LV coupler connection146.

FIG. 2is 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 poles220support MV lines202and LV lines204at a safe distance from the ground. Implementing a communication system on the power lines typically requires electronic components206,208,210,214,216including capacitors212,218in order to assure satisfactory transmission of broadband signals to customers224. The invention provides a safe, secure and reliable coupling technique for making electrical interconnections to high risk MV lines at coupling locations220, as well as to lower risk LV lines at coupling locations222.

The embodiment ofFIG. 3shows an exemplary coupler device300having an insulated portion302and a conductive portion304connected through link306via capacitor308to electronic components310. A threaded sleeve312receives a conductive adjustment screw313with threads314. The adjustment screw313has a contact point316for electrical contact with a power line cable (not shown). An insulated tool320, as for example a tool known in the trade as a hotstick, includes a long extension322having a cap324sized and shaped for engagement with the adjustment screw313. An installer can grasp a handle326at a location remote from high risk MV or lower risk LV power cables and actuate the tool such as by rotation in direction328.

The insulated portion302of the coupler300may have a hook-shaped end334formed by extension330and truncated end336. A leg portion332provides an attachment junction with the conductive portion304. The overall contours of the insulated portion302may be U-shaped in order to provide multiple interior contact surfaces338,340,324for contacting adjacent surfaces of a power line cable in order to support the coupler when the adjustment screw313is in open position, as well as to securely establish electrical contact and maintain attachment to the power cable when the adjustment screw313is in closed position. Other hook-like shapes may be incorporated in the insulated portion302in order to partially surround the power cable and maintain the coupler300in self-supporting position during initial coupler installation as well as during actuation of the tool to accomplish electrical contact between the conductive portion304and the energized power cable.

Of course, the benefits of the invention can be achieved with other adjustment members which perform a similar function to the adjustment screw313so 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.

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, inFIG. 4A, a conductive adjustment screw404has a tapered head406with a central contact point408and is shown facing upwardly in a vertical direction for making electrical contact with power cable400. A coupler having contact surfaces approximately coincident with plane410will apply compressive forces in a direction412in order to help maintain such electrical contact and hold the coupler in secure position on the power cable. A conductive adjustment screw414has a tapered head416with a central contact point418and is shown facing laterally in a horizontal direction for making electrical contact with power cable400. A coupler having contact surfaces approximately coincident with plane420will apply compressive forces in a direction422in order to help maintain such electrical contact and hold the coupler in secure position on the power cable. A conductive adjustment screw424has a tapered head426with a central contact point428and is shown facing partially upwardly in a somewhat oblique angular direction for making electrical contact with power cable400. A coupler having contact surfaces approximately coincident with plane430will apply compressive forces in a direction432in order to help maintain such electrical contact and hold the coupler in secure position on the power cable.

Similar orientations are illustrated inFIG. 4Bfor non-tapered heads respectively having sharp peripheral edge contact surfaces438,448,458. Compressive forces applied perpendicular to planes410,420,430will maintain electrical contact with adjustment screws436,446,456respectively, and hold the coupler in secure position on the power cable.

Referring toFIGS. 5A and 5B, a coupler device is shown in closed position with a conductive portion in electric metallic contact with a power line cable400. In these embodiments, a U-shaped insulated coupler arm334includes an elongated extension330and a shortened extension such as truncated end336. An adjustment shaft in the form shown as threaded adjustment screw313makes electrical contact and also applies compressive forces to hold the power line cable400in secure position against the U-shaped insulated coupler arm334.

InFIG. 5Aa central contact point316on the apex of the adjustment screw313makes the electrical contact. InFIG. 5Ba sharpened circular peripheral edge416on the apex of the adjustment screw31makes 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.

Additional embodiments for facilitating engagement of a self-supported coupling device on a power line are shown inFIGS. 6A and 6B. Referring toFIG. 6A, an insulated arm600includes elongated extension602, header604and shortened extension606which together form a rectangular-shaped hook having a central concave recess608shaped and sized to provide support on a power line cable611. A threaded conductor shaft613is shown in partially closed position with its tapered head615starting to penetrate an outer insulation layer prior to making electrical contact with the power line cable611(seeFIG. 4A).

Referring toFIG. 6B, an insulated arm610includes shortened extension612, header614and elongated extension616which together form a rectangular-shaped hook having a triangular slot618to provide support on a power line cable611. The threaded conductor shaft613is shown in partially closed position similar toFIG. 6A.

Referring to the embodiment ofFIG. 7, a mechanical fixture assembly includes a coupler device740shown in a self-supporting position on a power line700, and also includes a remotely activated insulated tool722that has been manually engaged with the coupler device740. The insulated tool722has a cap724sized and shaped to fit an enlarged base726of a threaded shaft728on the coupler device740. After an installer has manually rotated a handle727remotely located from the power line700in order to advance the threaded shaft728forwardly, a sharpened point730on 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 (seeFIG. 4A).

The threaded shaft and its adjacent threaded base732together constitute a conductor portion of the coupler device for carrying signals to and fro between line734and power line700. In this embodiment, an insulated arm is formed by a first extension742connected at its lower end to the base732, and is joined at its upper end748to angular extension744to form a triangular recess745for supporting the coupler device on the power line700. A lower leg portion746on the angular extension744along with interior contact surfaces750,752help to assure the coupler device740remains in self-supporting position on the power line700upon initial installation of the coupler device and during adjustment of threaded shaft728into conducting position by insulated tool722.

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.

Referring to the embodiment ofFIG. 8, a power line800is shown in an engaged position with a closed fully installed coupler device840comprising another mechanical fixture. A conductor shaft820has an upper end822tapered to form a sharpened central point824, the shaft being formed integral with a conductor plate826connected to signal line828. A separate bolt830that may be formed with a dielectric material has a threaded upper end836that engages a matching threaded sleeve838on a U-shaped insulated arm840. Rotation of the bolt by a remotely activated tool (not shown in this drawing) advances the conductor plate826and conductor shaft820forwardly into closed position to provide electrical metallic contact of the central point824with the power line800, as shown in the drawing. Rotation of the bolt830is facilitated by a raised low-friction boss834on the underside of conductor plate826.

When the conductor plate is moved to a closed position as shown by arrow846, the insulated arm840has a lower leg842abutting an end844of the conductor plate825in order to eliminate an initial installation gap. When the coupler device is in open position as shown in phantom at848, the initial installation gap allows insertion of the power line800inside of the U-shaped insulated arm. The upper part of the U-shaped insulated arm840provides a recess for holding the coupler device in self-supporting position on the power line800.

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.

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.