Phase identification apparatus having automatic gain control to prevent detector saturation

• US 20070063664A1
• Filed: 09/19/2006
• Published: 03/22/2007
• Est. Priority Date: 09/22/2005
• Status: Abandoned Application

• Current Assignee: Avistar
• Original Assignee: Avistar
• Inventors: Kessler, Gary, Migliori, Albert, Rhodes, George
• Application Number:
  US11/522,939
• Publication Number:
  US 20070063664A1
• Time in Patent Office: Days
• US Class Current: 318/400.210
• CPC Class Codes: G01R 15/09 Autoranging circuits
• CPC Class Codes: G01R 15/16 using capacitive devices
• CPC Class Codes: G01R 25/00 Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
• CPC Class Codes: G01R 29/18 Indicating phase sequence; Indicating synchronism

Abstract

An apparatus for measuring phase angle difference between two conductors uses a hot stick, a field unit, and reference unit. Voltage is sensed at a conductor, and the voltage is passed through an automatic gain control which adjusts the voltage input to a voltage detector to a level which prevents saturation of the voltage detector. Non-saturation of the voltage detector enables detection of all of the data in a detected sine wave. Pulse width modulation and pulse width modulation RF transmission are used to provide for data transmission from a hot stick to a field unit.

Claims

1. An apparatus for detecting power line AC voltage comprising in combination:

a voltage sensor having an output proportional to a power line voltage;

a voltage detector;

an automatic gain control for adjusting voltage input to the voltage detector to a level which prevents saturation of the voltage detector;

wherein all available data in the AC voltage is detected.

2. The apparatus for detecting power line phase in accordance with claim 1 wherein the sensor is a capacitor.

3. The apparatus for detecting power line voltage in accordance with claim 1 wherein prevention of saturation of the voltage detector enables detection of available phase information contained in the voltage sensor output.

4. The apparatus for detecting power line voltage in accordance with claim 1 wherein the gain control comprises:

an adjustable gain amplifier which is connected to said voltage sensor;

a rectifier circuit connected to an said adjustable gain amplifier which rectifies an output signal of said amplifier;

a CPU connected to the output of the rectifier circuit FIG. 1 which determines if the rectifier output signal is above saturation;

wherein the CPU provides a discrete gain adjustment signal to the adjustable gain amplifier when the averaged rectifier output is above a saturation level.

5. The apparatus for detecting power line voltage in accordance with claim 1 wherein the gain control comprises:

an amplifier which is connected to said voltage sensor, said amplifier having an output;

a analog multiplier connected to said amplifier output;

a rectifier circuit connected to an output of said analog multiplier and which rectifies an output of said analog multiplier;

an integrator connected to an output of the rectifier circuit, wherein the integrator averages the rectifier output signal, and wherein the integrator has an output;

a CPU connected to the output of the integrator circuit which determines if the rectifier output signal is above saturation;

wherein the CPU provides a discrete gain adjustment signal to the adjustable gain amplifier when the integrator output signal is above a saturation level.

6. The apparatus for detecting power line voltage in accordance with claim 1 wherein the gain control comprises:

an amplifier which is connected to said voltage sensor, said amplifier having an output;

a analog multiplier connected to said amplifier output;

a rectifier circuit connected to an output of said analog multiplier and which rectifies an output of said analog multiplier;

an integrator connected to an output of the rectifier circuit, wherein the integrator averages the rectifier output signal, and wherein the integrator has an output;

wherein the integrator output is connected to an input of the analog multiplier; and

wherein the analog multiplier multiplies a voltage from said amplifier by said integrator output and provides an input to said voltage detector.

7. The apparatus for detecting power line voltage in accordance with claim 5 wherein the gain control further comprises:

a desired level adjustment which is adjusted until the rectifier signal reaches a user selectable value.

8. The apparatus for detecting power line phase in accordance with claim 7 wherein the user selectable value is set with an integrating error amplifier level adjustment control.

9. The apparatus for detecting power line phase in accordance with claim 3 wherein the voltage detector is a digitizer for digitizing of the voltage signal.

10. The apparatus for detecting power line voltage in accordance with claim 9 further comprising a CPU which generates a pulse-width modulated digital signal.

11. The apparatus for detecting power line voltage in accordance with claim 10 further comprising a radio frequency transmitter for transmitting the pulse-width modulated digital signal as a pulse width modulated wave.

12. The apparatus for detecting power line voltage in accordance with claim 10 further comprising a radio frequency receiver for receiving said pulse width modulated wave and a converter for generating a sine wave from the pulse width modulated digital signal.

13. The apparatus for detecting power line voltage in accordance with claim 12 wherein the radio frequency transmitter is located in or on an end of a hot stick.

14. The apparatus for detecting power line voltage in accordance with claim 12 wherein the radio frequency receiver is located at a phase angle difference measurement field unit.

16. An apparatus for measuring phase angle difference between two conductors in accordance with claim 1 wherein the computer for determining a difference is located in the field unit.

15. An apparatus for measuring phase angle difference between two conductors comprising in combination:

a hot stick having

a voltage sensor having an output proportional to a power line voltage;

a voltage detector which is a first digitizer for digitizing of the voltage signal;

an automatic gain control for adjusting voltage input to the voltage detector to a level which prevents saturation of the voltage detector;

wherein prevention of saturation of the voltage detector enables detection of all available phase angle data contained in the voltage sensor output;

a hot stick computer which generates a pulse-width modulated signal; and

a radio frequency transmitter for transmitting a pulse-width modulated wave;

a field unit having

a radio frequency receiver for receiving said pulse width modulated wave and a converter for generating a sine wave from the pulse width modulated RF wave;

a second digitizer having an output for generating a digitized output of the reference voltage, which is initiated by a GPS pulse; and

a first computer for computing by a Fourier transform a power line phase value of a fundamental frequency of said reference voltage from the second digitizer output;

a reference unit having

a reference voltage sensor;

a reference voltage detector which is not saturated by a voltage from the reference voltage sensor;

a third digitizer having an output for generating a digitized output of the reference voltage, which is initiated by said GPS pulse; and

a second computer for computing by a Fourier transform a reference phase value of a fundamental frequency of said reference voltage from the third digitizer output;

a computer for determining a difference between the reference phase value and the power line phase value wherein the computer is located at the field unit or the reference unit.

18. The apparatus for measuring phase angle difference in accordance with claim 15 wherein the automatic gain control is a two stage automatic gain control which comprises:

a first discrete automatic gain control stage comprising;

a rectifier which rectifies an input to the voltage detector to provide an automatic gain controlled DC voltage output;

a CPU which receives the DC voltage from the precision rectifier and which determines whether gain adjustments need to be made;

wherein a step adjustable input amplifier gain is changed by the CPU by a discrete amount when gain adjustment is needed;

wherein when it is determined that the rectifier output DC voltage signal is below saturation discrete gain changing is terminated by the CPU;

a second fine automatic gain control stage comprising;

the precision rectifier which rectifies the input to the voltage detector;

an integrator connected to said rectifier which averages the gain controlled DC voltage signal of the rectifier for a long time compared to the period of the power line to produce a resulting DC signal; and

a multiplier for multiplying the signal voltage by an integrator output voltage to provide a continuous feedback for fine gain control.

19. The apparatus for measuring phase angle difference in accordance with claim 15 wherein the automatic gain control is a two stage automatic gain control which comprises:

a first discrete automatic gain control stage comprising;

a rectifier which rectifies an input to the voltage detector to provide an automatic gain controlled DC voltage;

an integrator connected to said rectifier which averages the gain controlled DC voltage signal of the rectifier for a long time compared to the period of the power line to produce a resulting DC signal;

a CPU which receives the DC voltage from the integrator and which determines whether gain adjustments need to be made;

wherein a step adjustable gain amplifier is changed by the CPU by a discrete amount when gain adjustment is needed;

wherein when it is determined that the rectifier output DC voltage signal is below saturation discrete gain changing is terminated by the CPU;

a second fine automatic gain control stage comprising;

the precision rectifier which rectifies the input to the voltage detector;

the integrator connected to said rectifier which averages the gain controlled DC voltage signal of the rectifier; and

a multiplier for multiplying the signal voltage by an integrator output voltage to provide a continuous feedback for fine gain control.

17. A method for measuring phase angle difference between two conductors comprising in combination:

placing hot stick voltage sensor having an output proportional to a power line voltage adjacent to a power line;

automatically controlling gain and adjusting input to a voltage detector to a level which prevents saturation;

digitizing the input to the voltage detector with a voltage digitizer;

wherein prevention of saturation of the voltage digitizer enables detection of available phase information contained in the voltage sensor output;

generating a pulse-width modulated signal;

transmitting the pulse width modulated signal as pulse width modulated RF wave;

placing field unit where it receives the transmitted pulse width modulated RF wave;

receiving said pulse width modulated RF wave and a converting the pulse width modulated wave to a sine wave signal;

generating a digitized output of the power line voltage, which is initiated by a GPS pulse;

computing by a Fourier transform a power line phase value of a fundamental frequency of said power line voltage from the second digitizer output;

placing a reference unit at a grid known location;

sensing a reference voltage;

generating a digitized output of the reference voltage, which is initiated by said GPS pulse;

computing by a Fourier transform a reference phase value of a fundamental frequency of said reference voltage from the third digitizer output;

determining a difference between the reference phase value and the power line phase value.