Methods of detecting anomalies in ambient alternating current fields

• US 20080255779A1
• Filed: 08/20/2007
• Published: 10/16/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Inventors: Hull, David M., Vinci, Stephen J.
• Granted Patent: US 7,920,975 B2
• Time in Patent Office: Days
• US Class Current: 702/57
• CPC Class Codes: G01R 29/12 Measuring electrostatic fields or voltage-potential

Abstract

Methods of detecting anomalies in ambient alternating current (AC) fields are provided. An exemplary embodiment of such a method includes the steps of placing an AC field sensor in an ambient AC field, generating a signal representative of the ambient AC field received by the sensor, and processing the signal to determine if the ambient AC field includes any anomalies. Various applications for the methods are also provided.

Claims

1. A method of detecting anomalies in an ambient alternating current (AC) field, comprising the steps of:

placing an AC field sensor in an ambient AC field;

generating a signal representative of the ambient AC field received by the AC field sensor; and

processing the signal to determine if the ambient AC field includes any anomalies.

2. The method of claim 1, wherein the AC field sensor is an AC electric field sensor or an AC magnetic field sensor.

3. The method of claim 1, wherein the ambient AC field is an approximately stable quasi-static electric or magnetic field.

4. The method of claim 1, wherein the signal is a voltage signal.

5. The method of claim 1, wherein the step of processing the signal includes the step of demodulating the signal to generate a demodulated signal that includes portions representative of anomalies in the ambient AC field.

6. The method of claim 5, wherein the step of demodulating the signal includes the step of demodulating the signal with a synchronous demodulation circuit.

7. The method of claim 1, wherein the step of processing comprises determining whether a detected anomaly corresponds to presence of a conducting or quasi-conducting object in the ambient AC field.

8. The method of claim 7, wherein the conducting or quasi-conducting object is a person, a ground vehicle or a low-flying aircraft.

9. The method of claim 1, wherein the step of processing comprises detecting anomalies caused by voltage fluctuations in an AC power line.

10. The method of claim 1, wherein the step of processing comprises detecting anomalies caused by movements of an AC power line.

11. The method of claim 1, wherein the step of processing comprises detecting anomalies caused by objects in close proximity to an AC power line.

12. A method of detecting anomalies in an ambient alternating current (AC) electric field generated by an AC power line, comprising the steps of:

placing an AC electric field sensor in an ambient AC electric field generated by an AC power line;

generating a signal representative of the ambient AC electric field received by the AC electric field sensor; and

processing the signal to determine if any anomalies are present in the ambient AC electric field.

13. The method of claim 12, wherein the ambient AC electric field is generated by the AC power line when the AC power line is energized but regardless of whether or not the AC power line is supplying current to a load.

14. The method of claim 12, wherein the signal is an amplitude modulated signal.

15. The method of claim 12, wherein the step of processing the signal includes the step of demodulating the signal with an amplitude demodulation circuit to generate a demodulated signal that includes portions representative of anomalies in the ambient AC electric field.

16. The method of claim 15, wherein:

the amplitude demodulation circuit includes an envelope detector connected to a low pass filter;

the signal is fed into the envelope detector; and

the demodulated signal is output by the low pass filter.

17. The method of claim 12, wherein the step of processing the signal includes the step of demodulating the signal with a synchronous demodulation circuit to generate a demodulated signal that includes portions representative of anomalies in the ambient AC electric field.

18. The method of claim 17, wherein:

the synchronous demodulation circuit includes a mixer connected to a low pass filter and a high-gain amplifier connected to the mixer;

the signal is fed to the mixer and the high-gain amplifier; and

the demodulated signal is output by the low pass filter.

19. A method of detecting anomalies in an ambient alternating current (AC) magnetic field generated by an AC power line, comprising the steps of:

supplying approximately stable AC current to an AC power line that causes the AC power line to generate an ambient AC magnetic field;

placing an AC magnetic field sensor in the ambient AC magnetic field generated by the AC power line;

generating a signal representative of the ambient AC magnetic field received by the AC magnetic field sensor; and

processing the signal to determine if any anomalies are present in the ambient AC magnetic field.