US1785972A - Communication system - Google Patents

Description

Dec. 23, 1930. V R. w. OSBORNE 1,785,972

COMMUNICATION SYSTEM Filed Oct. 16, 1929 Patented Dec. 23, 1930 PATENT orrica RALPH WILLOUGHIBY OSBORNE, OF TORONTO, ONTARIO, CANADA COMMUNICATION SYSTEM Application filed October 16, 1929, Serial No. 400,087, and in Canada August 6, 1928.

My invention relates to communication systems, and has special reference to protective means for systems that are subjected to transient disturbances due to their proximity to electric power transmission lines.

More particularly my invention refers to an electrical communication system which has one or more neutralpoints connected to ground for the drainage of extraneous. ourrent from the lines of the communication system to ground." 7

To those familiar with the art, it is well known that when the transmission line conductors of a communication system are parallel to an electric power transmission line, a

potential is induced in the transmission line conductors of the communication system. Such potentials are particularly severe dur- 3'0 tremities of the winding being connected respectively to each transmission line conductor of the communicatlon system. Drainage 0011s are so designed that they offer a low im-' pedance to induced current in the line conductors, but a very high impedance to the currentsused for the transmission of intelligence. A modification of the drainage coil comprises in addition to the winding and core enumerated above, a secondary winding thus constituting a transformer, the extremities of the primary winding being connected respectively to each transmission line conductor, the

neutral connected to ground, the secondary windingbeing insulated from the primary winding and its extremities connected to the conductors leading to the communication instrument or translating device.

During severe transient disturbances in the .power transmission system heavy current is induced in the communication line condue tors, which if permitted to flow through the winding of the drainage coil or transformer may burn out the winding. To protect the winding from burnoutit is common practise to insert fuses between the winding and the linewires. These fuses may blow out frequently causing interruption to the communication of intelligence.

The object of my invention. is to provide means for bypassing heavy extraneous current past the drainage coil or transformer winding directly to ground, and for automatically restoring the system to normal operating conditions when the extraneous current has subsided.

It is a further object of my invention to provide means for bypassing heavy extraneous current past the drainage coil or transformer winding directly to ground so as to permit using fuses of much larger capacity or in most cases dispensing with the use of fuses entirely.

In order to attain this object I provide arelay soarranged that it is actuated by extraneous current when such current exceeds a predetermined degree so as to close suitably arranged contacts for bypassing the current past the drainage coil or transformer winding to ground, and automatically releasing said contacts when the extraneous current subsides. I

In order to understand my invention more fully reference may be had to the following description and accompanying drawing in which the single figure is .a diagrammatic view of a communication system embodying a form of my invention.

Referring to the drawing it will be noted that I haveshown a communication system usinga transformer having a primary winding with the neutral point grounded, but it is apparent that my invention may be ap-. plied to a system employing a drainage coil. 1 and 2 represent the transmission line conductors of the communication system, 10 the relay with a pair of windings 3 and 4 connected respectively in series with the transmission line conductors 1 and 2' and woundarounda common core 5 and continued by means of wires 25 and '26 to the extremities of primary winding 13 of the transformer 11. 14: is the secondary winding of the transformer 11 connected to the translating device 23 by means of wires 21 and 22. The neutral point 12 of the primary winding 13 of the transformer 11 is connected to ground 16 by means of wire 15. Contacts 8 and 9 are con nected respectively by wires 19 and 20 to the extremities of primary Winding 13 at points i7 and 18 on wires 25 and 26. A third contact 7 is carried by armature 6 which is hinged by pivot 27 and normally held against back stop 29 by spring 28. Contact 7 is grounded through arn'iature (i and wire 24 to ground 16.

It will be seen that when extraneous current flows from wires 1 and 2 through windings 3 and 4 of relay 10, through wires 25 and 26 and the two halves'of the primary winding 13 of transformer 11, converging to neutral point 12 and ground wire 15 to ground at 16, the currents in the two windings 3 and 4 ofrelay 10 will act cumulatively tov magnetize core 5 and when the magnetic pull on armature 6 is sufficient to overcome the tension of the spring 28, contact 7 will be drawn down and make contact simultaneously with both contacts 8 and 9, thus bypassing the current around the primary'winding 13 of transformer 11 from points 17 and 18 through wires 19 and 20, contacts 8 and 9, contact .7,

armature ,6 and wire 24 to ground at 16. It will also be seen that the current continues to flow through the relay windings after the contacts have closed which is necessary in order to hold the contacts closed until the extraneous current subsides. When the cur rent subsides the armature is released. It has.

been found by experiment that a relay can be designed with heavy wire windings enabling them to carry heavy currents for considerable periods of time. In using the transformer with the ordinary fuse protection it frequently happens that one fuse blows leav-- ing the other intact and allowing current to pass through one half of the primary winding of the transformer with no opposing current in the other half oft-he winding, thus allowing a potential to build up which is transmitted to the secondary winding by induction, thence to the translating device. The importance of maintaining a balance of the circuit is therefore apparent for the adequate protection of the communication instruments connected thereto and it will be seen that the design'and operation of my relay is such that this ob ect is attained inasmuch that the two contacts are arranged to close and break simultaneously. This is accomplished by the simple expedient of arranging the contact faces of contacts 8 and 9 so that they converge at an angle and providing the contact electrode 7 with two contact faces respectively in parallel with the contact faces of contacts 8 and 9. .Vhen my relay protection is employed both sides. of the circuit remain intact atall times and when extraneous current becomes excessive the contacts close and bypass the transformer thus allowing a negligible current to flow through the transformer winding. It will be seen therefor that while the primary object of the invention is to protect the transformer by so doing better protection is afforded the translating instruments. The inductive properties of the relay wind ings also protect the transformer windings from high frequency disturbances that may set up in the system.

While I-have shown and described one em bodiment of my invention, it will be understood that'variousmodifications-may be made without departing fromthe spirit and scope of the appended claims.

That I claim is:

1. A communication system comprising transmission line conductors, a translating device relatively connected thereto, a winding extending between the transmission line conductors and having a neutral point connected to ground thus providing a path for draining extraneous current in the said communication system to ground, and an electromagnetic means serially connected in the said path and adapted to operate automatically suitably arranged contacts for connecting to ground, both extremities of the said winding having a neutral point, when extraneous current in the communication system exceeds a predetermined degree and for disconnecting both extremities of the said winding from ground when the extraneous currentsubsides.

2. A communication system comprising transmission line conductors, a translating device relatively connected thereto, a winding extending between the transmission line conductors and having a neutral point connected to ground and a relay comprising a pair of windings connected respectively in series with eachtransmission line conductor and wound around a common core, a pair of contacts connected respectively to each extremity of the aforementioned winding having a neutral point, anv armature carrying a third contact which is grounded and adapted to simultaneously make contact with both of the aforementioned pair of contacts when extraneous current in the said communica tion system exceeds a predetermined degree and to simultaneously break both contacts when extraneous current subsides.

3. A communication system comprising a translating device, transmission line conductors, conductors leading to said translating device, a transformer interposed in the circuit and having a primary winding extending between the transmission line conductors, said primary winding having a neutral point connected to ground, a secondary winding extending between the conductors leading to the saidtranslating device and a relay comprising a pair of Windings connected respectively in series with each transmis sion line conductor and Wound around a common core, a pair of contacts connected respectively to each extremity of the aforementioned primary Winding, an armature carrying a third contact which is grounded and adapted to simultaneously make contact with both contacts of the aforementioned pair of contacts When extraneous current in the said communication system exceeds a predetermined degree and to simultaneously break both contacts When extraneous current in said communication system subsides.

In testimony whereof I aifix my signature at the city of Toronto.

RALPH WILLOUGHBY OSBORNE.

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