US1852902A - Telephone system for high tension transmission lines - Google Patents

Description

April 1932- R. B. H. ROCKWELL 1,852,902

TELEPHONE SYSTEM FOR HIGH TENSION TRANSMISSION LINES Filed Dec, 12, 1950 INVENTOR 0 akzmeZZ ATTORNEYS Patented Apr. 5, 1932 PATENT OFFICE ROBERT B. H. ROCKWELL, OI ATLANTA, GEORGIA TELEPHONE SYSTEM. FOR HIGH TENSION TRANSMISSION LINES Application filed December 12, 1980. Serial No. 501,961.

This invention relates to high voltage transmission systems and more particularly to communication systems wherein the conductors are strung on transmission towers or poles. One of the objects of the invention is to eliminate the possibility of building up dangerous induced voltages in the communication circuits due to the proximity of the communication conductors to the electrical conductors. Also, the invention aims to utilize a ground conductor as a sheath to carry the communication conductors, thereby dispensing with the ordinary separate communication conductors which are usually connected to the towers or poles below the power conductors where they endanger the lives of linemen.

Other aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawings wherein Fig. 1 is a diagrammatic view showing a telephone system connecting stations of a power system;

Fig. 2 is an enlarged fragmentary View showing telephone conductors within an improved form of hollow ground wire or conductor; and

Fig. 3 is a sectional view of the ground Wire and telephone conductors shown in Fig. 2.

Telephone circuits for transmission systems are very expensive to install because they require special equipment to insure safety. Moreover, the ordinary telephone conductors mounted on towers below the power conductors are a constant source of danger to linemen on account of induced voltages. Further, such systems are sometimes so noisy as to make satisfactory communication practically impossible. This invention provides a system wherein the telephone conductors are housed within an overhead ground wire so as to utilize the ground wire as a means to dissipate any induced voltage from the power conductors. Overhead ground wires are now being used as lightning protection on nearly all long transmission lines. They are useful only during storms. By combining telephone conductors with them they serve a double purpose. Thus, the expense of installing such combined conductors is justified even on short lines and in localities where lightning storms are more or less frequent.

In this example, a telephone system is shown as connecting two power stations having telephone equipment 11. The telephone conductors 12 are housed within an overhead ground wire or cable 13 which is strung on the tops of the usual steel towers 14c and grounded through each tower. The telephone conductors are ordinary insulated wires covered by insulation 15 and wrapped with a metal tape 16 like an armored cable. The arrangement is such that the conductors are well insulated from the ground wire and from each other.

The ground wire may be an ordinary tubular shell of such diameter as to receive the telephone cable, but in this example it is formed of twisted steel. strands. This construction not only enables the ground wire to be formed on the telephone cable but the steel strands have great permeability and thus a shielding effect to magnetic induction.

Now it will be seen that the communication circuits are very nearly completely shielded from the influence of the transmission line conductors even though there may be a fault to ground or a flash over on the transmission system. If the ordinary telephone wires were used, such a condition would cause very dangerous induced voltages when a fault to ground occurs. Most of the fault current returns on the overhead ground wire or sheath for the telephone conductors. The magnetic field about the ground wire, due to this current, opposes the magnetic field about the power conductors; consequently practically all of the magnetic flux due to the fault current in the power conductors would be crowded between them and ground wire and there would be very little linkage of the ground wire due to magnetic 5 flux from the power conductors. Moreover, current flowing in the ground wire or sheath would produce practically no magnetic flux within it. Since the sheath is grounded at mo every tower the communicating circuits will not be afl'ected by any electro-static disturbances outside of the sheath or ground wire and quiet and efiicient communication will result. In fact, the arrangement elimi nates loud humming which is very troublesome in ordinary communication systems.

Obviously, the present invention is not restricted to the particular embodiment thereof herein shown and described.

What I claim is I 1. In a high voltage transmission system,

' an overhead ground wire for lightning protection comprising a hollow conductor connected to and grounded at the transmission line supports; and a series of communication wires within and insulated from the hollow conductor whereby the hollow conductor acts as an anti-induction shield for the wires.

2. In high voltage transmission systems wherein the electrical conductors are supported on towers, a hollow, overhead ground wire connected to the tops of the towers; and insulated telephone wires within the hollow ground wire whereby the ground wire serves as an anti-induction shield for the telephone wires.

3. In combination with a communication system for high voltage transmission lines, an overhead ground wire comprising a hollow sheath made of oppositely twisted strands; and telephone" conductors within and insulated from the sheath whereby the sheath acts as an anti-induction shield for the said conductors.

4. In a high voltage transmission system, a combined lightning protective ground wire and hollow anti-induction sheath for a series of insulated telephone Wires; said sheath housing the telephone wires throughout the lengthof the system.

In testimony that I claim the foregoing as my own, I have hereto afliXed my signature.

ROBERT B. H. ROCKWELL.

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