US1539902A - Carrier transmission over power circuits - Google Patents

Description

June 2. 19.25-

R. K. HONAMAN CARRIER TRANSMISSION OVER POWER CIRCUITS Filed April 29, 1924 INVENTOR IRK. HmmY/nan/ ATTORNEY Patented June 2, 1925.

UNITED STATI-:s

PATENT OFFICE..

RICHARD IK, HONAMAN, OF BLOOMFlELD, NEW JERSEY, ASSIGNGR T AMERICAN TELEPHONE & TELEGRAPH COMPANY, A CORPORATION OF YQRK.

CARRIER TRANSMISSION OVER POWER. CIRCUITS.

Application led April 29, 1924. Serial N'o. 709,898.

To all whom may concern: p

Be it known that I, RICHARD K. HoNA- MAN, residing at Bloomfield, in the county of Essex and State of New Jersey, have invented certain Improvements in Carrier Transmission Over Power Circuits, of which the following is a specification.

This invention relates to the use of power circuits for the transmission of signaling currents, and lmore particularly to arrangements whereby carrier transmission channels may be related to the conductors of a power system.

In accordance with the present invention, advantage is taken of the fact that .the current transformers, which are ordinarily associated with a power system in order to step down the current actually transmitted to a value suitable for use with nary current measuring instruments, e such characteristics that, although normilly designed for the transmission y of power frequencies, they will eiiciently transmit the much higher frequencies employed in carrier transmission. The carrier apparatus is connected to the circuit `which includes the current measuring or other translating device which is normally inductively connected to the power circuit, and in order to prevent an substantial increase in the impedance o the instrument i the connection is made through a ing a very low impedance at the pew e. frequency and a considerably higher' impedance at the carrier current frequencies, v

rthe invention will now be more fully understood from the following description when read in connection with the accomvif; psig: irawings, Figures 1 and 2 of which illustrate two different arrangements embodying the principles of the invention.

Referring to Fig. 1, G designates a power generator of the well known polyphase type 1, 2 and .3, respectively, of the power dishaving its starwindings connected to the tribution system. The transformers 11, 12 and 13 are transformers which step down the current flowing through the measuring instruments to values appropriate for indication by the measuring instruments. The terminals of the three measuring instruments are normally connected together (as indicated by the dotted line connection in the figure) and grounded througha conductor of substantially no resistance as shown.

In practice, the current transformers such as 11, 12 and 13 have their windings constructed with relatively few turns so that thedistributed capacity' is very small, and although these transformers are primarily designed for the transmission of power frequencies such as currentsin the neighborhood of cycles, they are quite eicient transformers at the much higher frequencies employed in carrier transmission. Consequently in superposinga carrier channel on a power distribution system it adds greatly to the economy of the system to be able to utilize the current transformers for associating the carrier channel with the power conductors. In order to accomplish this result, the present invention contemplates opening the normal connection between two of the instrument circuits,vfor example, 1 'i and 2', and connecting the terminals of the carrier channel C to the two instrument terminals as indicated.

In order that this may be` done without disturbing the measuring apparatus, the impedance looking into the carrier channel must be made very low forv the power frequencies. The carrier channel may be made to have a very low impedance to the power frequencies if the high-pass filter F which is included in the channel to suppress power frequencies and the lower harmonics thereof, is properly designed. The impedance looking into the filter isv not greatly different from the impedance of the Erst section of the filter. Consequently if the filter is given a shunt termination, as illustrated, its impedance will be very low, for the shunt inductance element of the first section of the filter may be readily designed to offer a very low impedance to 60 cycle currents without changing the action of the lilter in its range of free transmission. The power currents to be measured will therefore pass through the measuring, instrushunt these instruments by means of con densers, as indicated, to by-pass the carrier frequencies.

A modified arrangement is illustrated in Fig. 2 which differs from that of Fig. 1 in that one terminal of the carrier channel is connected to ground and the other terminal is connected to a conductor common to the three measuring circuits so that the carrier current will be transmitted over the three wires of the distribution system in parallel.

Normally the current measuring instruments will have their terminals joined together and the common terminal connected to ground, preferably through an additional measuring instrument 24, which measures'the total current flowing in all three conductors of the distribution system. The carrier channel C may be connected to the circuit of the current transformers by opening the normal ground connection shown in dotted lines in Fig. 2 and connecting the terminals of the carrier channel into the circuit at the point where it is o ened up. As in the case of Fig. 1, it is un esirable that any substantial impedance be introduced in the measuring circuit at the power frequency, and accordingly the filter is'constructed to have a shunt termination. The terminal shunt inductance element of the filter, as already stated, may then have practically negligible impedance at the power frequency without changing the action of the filter at carrier frequencies.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed is:

1. In a system for signaling over power conductors, a power source, power conductors for transmitting power from said source to a load, current transformers associated ing a filter connected in circuit with said transformers and having a very low impedance at power frequencies.

2. In a. system for signaling over power conductors,a power source, power conductors fortransmitting power from said source to a load, current transformers associated with said conductors for transforming the current to be applied to translating devices, carrier apparatus, and means to connect said carrier apparatus to said power conductors through said current transformers, comprising a high-pass filter included in circuit with said transformers and having a shunt termination so that its impedance will be very low at power frequencies.

3. In a system for signaling over power conductors, apower source, power conduc-` tors for transmitting power from said source to a load, current transformers associated with said conductors for transforming the current to be applied to translating devices, carrier apparatus, and means to connect said carrier apparatus to said power conductors through said current transformers, comprising a high-pass filter having its terminals connected in circuit with said current transformers, said filter being so designed that its impedance at power frequencies will be very low.

4. In a system for signaling over power conductors, a power-source, power conductors for transmitting power from said source to a load, current transformers associated with said conductors for transforming the current to be applied to translating devices, carrier apparatus, and means to connect said carrier apparatus to said power conductors through said current transformers, comprising a high-pass filter having its terminals connected in circuit with said translating devices, said filter having a shunt termination so that its impedance to currents of power frequency will be very low.

In testimony whereof I have signed my name to this specification this 26th day of April, 1924.

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