Power line communication system having a protective terminating impedance arrangement

• US 3,924,223 A
• Filed: 02/21/1974
• Issued: 12/02/1975
• Est. Priority Date: 02/21/1974
• Status: Expired due to Term

• Current Assignee: ABB Power T&D Limited (ABB Limited)
• Original Assignee: Ian A. Whyte, Leonard C. Vercellotti
• Inventors: Whyte, Ian A., Vercellotti, Leonard C.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/444,587
• Time in Patent Office: 649 Days
• Field of Search: 340/31A,31R,150,151 333/24C,77,79,1,2,12 328/165,138 324/57R
• US Class Current: 307/1
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5491 using filtering and bypassing
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines

Abstract

A terminating impedance network is disclosed for communication signals transmitted by a power line carrier communication system to the premises of residential customers of an electric utility. Corrective impedance values suitable for communication signal terminations are established in the power line conductors serving the customer loads from a distribution network. Frequency sensitive low impedance values are established across the service conductors adjacent the customer loads to protect the communication system from interfering signals and high frequency noise originating in the customer loads.

Claims

1. A power line communication system transmitting high frequency carrier communication signals through power line conductors of a distribution network supplying power to electric loads at the premises of an electric utility customer with the customer electric loads characterized by varying impedance values and at least periodically being at very low impedance values, wherein the system comprises:

a plurality of service conductors including line and grounded conductors at the customer premises connecting the power line conductors of said distribution network to the customer electric loads so as to supply electric power to the loads while concurrently having said high frequency carrier communication signals transmitted thereon;

a communication terminal coupled to a pair of said service conductors including at least one line conductor for transmitting and receiving said high frequency carrier communication signals through said service conductors; and

means forming a terminating impedance in the service conductors at the premises of the utility customer including tubular magnetic core means, said at least one line conductor passing through said tubular magnetic core means at a location intermediate said communication terminal and said customer electric loads, and said magnetic core means effecting a predetermined inductance having a substantially increased value of impedance at the frequencies of the communication signal relative to the very low impedance values of said customer electric loads.

2. A power line communication system as claimed in claim 1 wherein the means forming the terminating impedance includes parallel resonant circuit means formed by a capacitor means being transformer coupled to the magnetic core means, and said parallel resonant circuit means being tuned to the frequencies of the high frequency carrier communication signals.

3. A power line communication system as claimed in claim 1 including a capacitor connected across said service conductors at an intermediate location between the magnetic core means and the customer loads so as to be in parallel with the loads, said capacitor having a predetermined capacitance so as to present a substantially lower value of impedance at the frequencies of the communication signals relative to higher impedance values of said customer electric loads and being in the order of one ohm or less so as to provide a bypass path for interfering signals orginating at the customer loads in the frequency range of the communication signals.

4. A power line communication system as claimed in claim 3 wherein the means forming the terminating impedance includes an inductance connected in series with said capacitor so as to form a series resonant circuit tuned to the frequencies of the high frequency carrier communication signals.

5. A power line communication system as claimed in claim 1 wherein the tubular magnetic core means is made of a ferrite magnetic material, and further wherein the magnetic core means is made of two substantially identical halves each substantially enclosing one half of the associated service conductor.

6. A power line communication system as claimed in claim 5 wherein the the magnetic material has a thickness in the order of 0.25 inch.

7. A power line communication system as claimed in claim 1 including a watthour meter connected to the service conductors between the means forming the terminating impedance and the customer loads.

8. A power line communication system as claimed in claim 1 wherein each of said service conductors passes through the magnetic core means at the intermediate location, the magnetic core means effecting separate predetermined inductances in each of the service conductors so that the predetermined inductances have impedance values that are substantially increased at the communication signal frequencies relative to the low impedance values of the customer electric loads.

9. A power line communication system as claimed in claim 8 wherein the increased impedance values effected by the magnetic core means is in a range in the order of 50 to 600 ohms.