Method and apparatus, for power line communications using zero crossing load interruption

• US 4,300,126 A
• Filed: 04/11/1980
• Issued: 11/10/1981
• Est. Priority Date: 04/11/1980
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gajjar, Jagdishchandra T.
• Primary Examiner(s): Groody, James J.
• Application Number:
  US06/139,437
• Time in Patent Office: 578 Days
• Field of Search: 340/310 R, 340/310 A, 340/310 CP, 340/151, 340/147 LP, 340/163, 340/152 R, 340/152 T, 307/3, 307/149
• US Class Current: 307/17
• CPC Class Codes: H02J 13/00009 using pulsed signals
• CPC Class Codes: H02J 13/0001 using modification of a parameter of the network power signal
• CPC Class Codes: H02J 13/00034 the elements or equipment being or involving an electric power substation
• CPC Class Codes: H04B 2203/542 using zero crossing information
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/52 Outage or fault management, e.g. fault detection or location
• CPC Class Codes: Y04S 40/121 using the power network as support for the transmission

Abstract

In a system for communicating information over a power line network, connection of power loads is interrupted in the vicinity of zero crossings of the A.C. power line waveform to provide a high impedance condition during which the transmitters and receivers of the power line communication carrier system can be efficiently coupled to power network transformer secondary windings in order to improve communications reliability. The communications apparatus is coupled to the secondary winding through a capacitance, chosen to substantially series-resinate the leakage inductance presented by transformer secondary winding. Each load is connected through an interruption device to the secondary winding, with the interruption device interrupting the flow of current from the secondary winding to the associated load, responsive to both detection of each zero crossing of a power distribution network voltage waveform and to the presence of the power line carrier communications signal.

Claims

1. Apparatus for use in a power line carrier communications system having at least one load connected through a transformer to a power distribution network having a periodic network waveform voltage thereon, comprising:

at least one means for selectively interrupting current flow to an associated power-consuming load, responsive to an interruption signal;

means for detecting zero crossing of the network waveform voltage to provide an output signal to said interrupting means as said interruption signal to cause said interrupting means to interrupt current flow to said associated load for a time interval of predetermined duration in the vacinity of each network waveform zero crossing;

communications means associated with at least one of said at least one load for transmitting and/or receiving power line carrier communications signals to and/or from said network when said interrupting means has interrupted current flow to said associated load; and

an impedance element connected in series between said communications means and said transformer, said impedance element having a reactance selected to neutralize at least a portion of the leakage inductive reactance of said transformer to which said element is connected, at the carrier frequency of said power line communications signal.

2. The apparatus as set forth in claim 1, wherein said impedance element is a capacitance.

3. The apparatus as set forth in claim 1, wherein said transformer is a power network distribution transformer.

4. The apparatus as set forth in claim 3, wherein said impedance element is a capacitance element.

5. The apparatus as set forth in claim 1, wherein said communications means provides a signal whenever use of said network for communications purposes is required;

said apparatus further comprising;

a source of control potential;

means for switching said control potential under control of said communications means signal; and

means for providing said interruption signal only when both said control potential switching means is enabled and said zero crossing means output signal are present.

6. The apparatus as set forth in claim 5, wherein said interruption signal providing means is an AND gate having a first input receiving said control potential when said switching means is enabled, a second input receiving said zero crossing means output signal, and an output which is enabled only when both of said first and second inputs are enabled.

7. Apparatus for use with a power line carrier communications system having at least one transformer having a primary winding connected to a power distribution network having a periodic waveform voltage thereon, said system having a plurality of loads, each load connected to a secondary winding of said transformer, comprising:

a like plurality of means each for detecting zero crossings of said network waveform voltage to each provide a zero crossing signal;

a like plurality of means each for selectively interrupting current flow to an associated power-consuming load from the transformer secondary winding, each interrupting means being responsive to both an associated signal and an associated zero crossing signal;

communications means associated with at least one of said loads for transmitting and/or receiving power line carrier communications signals to and/or from said network only when an associated zero crossing signal is present, said communications means also providing said associated signal to the interrupting means associated with the load with which said communications means is associated; and

means associated with the remaining ones of said interrupting means for recognizing when another of said interrupting means is enabled to generate said associated signal to cause interruption of current flow to the load associated with said remaining ones of said interrupting means.

8. The apparatus as set forth in claim 7, wherein each of said recognizing means is a receiver tuned to at least one power line carrier frequency, and providing said associated signal whenever a signal at one of said at least one power line carrier frequency is received.

9. The apparatus as set forth in claim 7, wherein said communications means also transmits, when in operation, an auxiliary signal at a frequency which is other than a power line carrier frequency, and said recognizing means is a receiver tuned to the auxiliary signal.

10. The apparatus as set forth in claim 7, wherein said interrupting means interrupt current flow to all loads connectable to said transformer winding whenever the communications apparatus associated with any one of the loads is operational.

11. A method for providing power line communications on a power distribution network having a distribution transformer with at least one load connected to a secondary winding thereof, comprising the steps of:

(a) providing power line carrier communication apparatus at at least one of the locations associated with a load;

(b) detecting zero crossings of the network waveform to provide a zero crossing signal;

(c) providing a communications control signal whenever said power line carrier communications apparatus is to be coupled to said transformer secondary winding;

(d) selectively interrupting current flow to all loads connected to the transformer secondary winding when said zero crossing signal and said communications control signal are both present;

(e) causing said communications apparatus to be operatively coupled to said secondary winding only when said zero crossing signal is present;

(f) providing an impedance element connecting said communications apparatus to said transformer secondary winding; and

(g) adjusting the reactance of said element to substantially neutralize the reactance of a leakage inductance associated with said transformer secondary winding at the carrier frequency of said power line carrier apparatus.

12. The method as set forth in claim 11, wherein the impedance element of step (f) is an electrical capacitance.

13. The method as set forth in claim 11, wherein said control signal of step (c) is a power line carrier signal transmitted by that one of the power line communications apparatus then operatively coupled to said secondary winding;

and step (d) includes the step of detecting said control signal as a carrier signal across said secondary winding.

14. The method as set forth in claim 11, further comprising the step of transmitting an auxiliary control signal on a frequency other than the frequency of a powerline communications carrier from that one of said communications apparatus then coupled to said secondary winding;

and step (d) includes the step of detecting said auxiliary control signal across said secondary winding as said communications control signal.