Non-contact self-powered electric power monitor

• US 6,470,283 B1
• Filed: 11/15/1999
• Issued: 10/22/2002
• Est. Priority Date: 11/15/1999
• Status: Expired due to Fees

• Current Assignee: Edel, Thomas G.
• Original Assignee: Edel, Thomas G.
• Inventors: Edel, Thomas G.
• Primary Examiner(s): Shah, Kamini
• Assistant Examiner(s): VO, HIEN XUAN
• Application Number:
  US09/440,483
• Time in Patent Office: 1,072 Days
• Field of Search: 702/64, 702/65, 702/60, 361/18, 361/79, 361/1, 361/56, 340/310.01, 340/870.02, 324/544, 324/72.5, 324/557
• US Class Current: 702/64
• CPC Class Codes: G01R 15/142 Arrangements for simultaneous measurements of several parameters employing techniques covered by groups G01R15/14 - G01R15/26
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging

Abstract

An electric power monitoring device that senses power system voltages by capacitive coupling to one or more power system conductors. The capacitive coupling may be embodied by wrapping a conductive material around the insulating covering of a power system conductor. A capacitor is connected between the conductive material and a reference voltage to form a simple voltage divider. The voltage across the capacitor is proportional to the power system voltage and is used as an information signal which is analyzed by a microprocessor, after being converted to digital form by an analog-to-digital converter. Standard current transformers may be used to provide current information signals, which are also analyzed by the microprocessor. Operating power may be derived from one or more of the current information signals generated by current transformers. The power monitor requires no direct connections to power system conductors and requires no separate source of operating power.

Claims

1. Apparatus for providing indication of electric power;

said apparatus comprising;

(a) a voltage-sensing means for sensing a voltage signal;

said voltage signal being provided in a non-contact manner by a capacitive coupling in close proximity to a power system conductor;

said voltage signal providing information about a first voltage on said power system conductor;

said voltage-sensing means being connected to said capacitive coupling;

(b) a current-sensing means for sensing an input current;

said input current being provided in a non-contact manner by a current transformer;

said input current providing information about a primary electric current flowing on said power system conductor;

said current-sensing means being connected to said current transformer;

(c) a power supply means for deriving operating power from said input current;

said power supply means being connected in series with said input current;

(d) a microprocessor means for calculating one or more electric power parameters;

said microprocessor means receiving information about said voltage signal from said voltage-sensing means and receiving information about said input current from said current-sensing means;

said microprocessor means further utilizing operating power provided by said power supply means;

(e) a communicating means for communicating said one or more electric power parameters;

said communicating means receiving said one or more electric power parameters from said microprocessor means;

said apparatus deriving both information and operating power from said input current;

said apparatus requiring no other external source of operating power;

said apparatus requiring no direct connection to any electric power system conductor.

2. The apparatus of claim 1 wherein said power system conductor has an insulating covering and said capacitive-coupling comprises a conductive material in close proximity to said insulating covering.

3. The apparatus of claim 2 wherein said conductive material is a flexible metallic material wrapped around said insulating covering.

4. The apparatus of claim 2 wherein said conductive material is a flexible semiconducting material wrapped around said insulating covering.

5. The apparatus of claim 2 wherein said voltage-sensing means comprises

(a) a capacitor connected between said conductive material and a reference voltage, thereby forming a voltage divider with said capacitive coupling; a second voltage across said capacitor being approximately proportional to, and smaller than, said first voltage; and

(b) an analog-to-digital converter circuit for measuring said second voltage and providing digital information about said second voltage to said microprocessor means.

6. The apparatus of claim 5 wherein the accuracy of said current transformer is adversely affected by the operation of said power supply means and said sensing of said input current is not continuous;

said power supply means therefore deriving operating power from said input current only during periods of time during which said input current is not sensed, thereby improving the accuracy of said input current during periods of time that said input current is sensed, thereby improving the accuracy of said apparatus.

7. The apparatus of claim 6 wherein

said current transformer comprises a secondary winding and a magnetic core;

said secondary winding being wrapped around said magnetic core;

said current transformer being positioned around said power system conductor in such a way that said power system conductor functions as a primary winding of said current transformer;

said input current flowing in said secondary winding; and

said current-sensing means comprises a resistor and an analog-to-digital converter circuit;

said resistor being connected in such a way that said input current flows through said resistor whenever said input current is sensed;

a third voltage across said resistor therefore being approximately proportional to said input current;

said analog-to-digital converter circuit measuring said third voltage and providing digital information about said third voltage to said microprocessor means.

8. The apparatus of claim 7 wherein said communicating means utilizes a communication medium selected from the group consisting of a visual display, electric signals on metallic wires, electric signals on metallic cables, radio waves, electromagnetic radiation, light waves through air, and light waves through optical fiber.

9. The apparatus of claim 1 wherein the accuracy of said current transformer is adversely affected by the operation of said power supply means, and said sensing of said input current is not continuous;

said power supply means therefore deriving operating power from said input current only during periods of time during which said input current is not sensed, thereby improving the accuracy of said input current during periods of time that said input current is sensed, thereby improving the accuracy of said apparatus.

10. The apparatus of claim 9 wherein

said current transformer comprises a secondary winding and a magnetic core;

said secondary winding being wrapped around said magnetic core;

said current transformer being positioned around said power system conductor in such a way that said power system conductor functions as a primary winding of said current transformer;

said input current flowing in said secondary winding; and

said current-sensing means comprises a resistor and an analog-to-digital converter circuit;

said resistor being connected in such a way that said input current flows through said resistor whenever said input current is sensed;

a third voltage across said resistor therefore being approximately proportional to said input current;

said analog-to-digital converter circuit measuring said third voltage and providing digital information about said third voltage to said microprocessor means.

11. The apparatus of claim 1 further comprising

(a) a plurality of said voltage-sensing means;

each of said voltage-sensing means sensing one of a plurality of said voltage signal;

each of said voltage signals being generated by capacitive-coupling with one of a plurality of said power system conductor; and

(b) a plurality of said current-sensing means;

each of said current-sensing means sensing one of a plurality of said input current;

each of said input currents being generated by one of a plurality of said current transformer;

said apparatus further providing indication of electric power parameters associated with all of said input currents and said voltage signals;

said apparatus deriving operating power from one or more of said input currents.

12. The apparatus of claim 1 wherein said communicating means utilizes a communication medium selected from the group consisting of a visual display, electric signals on metallic wires, electric signals on metallic cables, radio waves, electromagnetic radiation, light waves through air, and light waves through optical fiber.

13. A method for providing indication of one or more electric power parameters;

said method comprising the steps of;

(a) generate a voltage information signal in a non-contact manner by utilizing capacitive-coupling means with a power system conductor;

(b) generate a current information signal in a non-contact manner by utilizing a current transformer in a non-contact arrangement with said electric power conductor;

(c) derive operating power from said current information signal;

(d) sense said current information signal and said voltage information signal;

(e) utilize a microprocessor means to calculate said one or more electric power parameters from said current information signal and said voltage information signal; and

(f) communicate said one or more electric power parameters utilizing a suitable communication means;

said method requiring no direct connection to any electric power system conductor;

said method requiring no external source of operating power.

14. The method of claim 13 wherein the accuracy of said of said current information signal is adversely affected by derivation of said operating power, and sensing of said current information signal is not continuous;

said operating power therefore being derived from said current information signal only during periods of time during which said current information signal is not sensed, thereby improving the accuracy of said current information signal during periods of time that said current information signal is sensed, thereby improving the accuracy of said method.

15. The method of claim 13 further providing indication of said one or more electric power parameters for a plurality of said power system conductor;

said method further comprising the steps of

(a) generate a plurality of said voltage information signal in a non-contact manner by utilizing capacitive-coupling means with a plurality of said power system conductor;

(b) generate a plurality of said current information signal in a non-contact manner by utilizing a plurality of said current transformer, each in a non-contact arrangement with one of said plurality of said power system conductor;

(c) derive operating power from one or more of said plurality of current information signals;

(d) sense said plurality of current information signals and said plurality of voltage information signals; and

(e) utilize said microprocessor means to calculate said one or more electric power parameters from said plurality of current information signals and said plurality of voltage information signals.

16. The method of claim 13 wherein said communicating means utilizes a communication medium selected from the group consisting of a visual display, electric signals on metallic wires, electric signals on metallic cables, radio waves, electromagnetic radiation, light waves through air, and light waves through optical fiber.

17. The method of claim 13 wherein said power system conductor has an insulating covering and said capacitive-coupling means comprises a conductive material in close proximity to said insulating covering.

18. The method of claim 17 wherein said voltage-information signal is generated by connecting a capacitor between said conductive material and a reference voltage, thereby forming a voltage divider with said capacitive coupling means;

a second voltage across said capacitor being approximately proportional to, and smaller than, a first voltage associated with said power system conductor;

said second voltage being said voltage-information signal.

19. The method of claim 18 wherein the accuracy of said current information signal is adversely affected by derivation of said operating power, and sensing of said current information signal is not continuous;

said operating power therefore being derived from said current information signal only during periods of time during which said current information signal is not sensed, thereby improving the accuracy of said current information signal during periods of time that said current information signal is sensed, thereby improving the accuracy of said method.

20. The method of claim 19 wherein said communicating means utilizes a communication medium selected from the group consisting of a visual display, electric signals on metallic wires, electric signals on metallic cables, radio waves, electromagnetic radiation, light waves through air, and light waves through optical fiber.