Electrical energy meter

• US 4,255,707 A
• Filed: 08/07/1979
• Issued: 03/10/1981
• Est. Priority Date: 08/07/1979
• Status: Expired due to Term

• Current Assignee: ABB Power T&D Limited (ABB Limited)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Miller, Robert C.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US06/064,603
• Time in Patent Office: 581 Days
• Field of Search: 324/142, 364/483, 328/151, 328/158
• US Class Current: 324/142
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

Method and meter apparatus for measuring parameters of electrical energy quantities occurring in an electrical power distribution system. The meter apparatus samples a second input signal, which is proportional to one of the voltage and current components of an electrical energy quantity, at predetermined instants, which are a function of unit changes in the magnitude of a first input signal, which is proportional to the time integral of one of the voltage and current components of the electrical energy quantity, to provide instantaneous values of said second input signal. Successive ones of the instantaneous magnitudes of the second input signal are converted to signal representations and accumulated to provide totalized values which are equivalent to the time integral of the product of the ones of the electrical energy components being represented by the first and second input signals over a predetermined period of time and which are proportional to a measured parameter occurring on the electrical distribution system.

Claims

1. Meter apparatus for measuring a parameter of an electrical energy quantity occurring in an electrical power distribution system comprising:

input means for generating first and second input signals representative of certain ones of the voltage and current components of said electrical energy quantity occurring on said electrical power distribution system, with said first input signal being proportional to the time integral of one of said voltage and current components and said second input signal being directly proportional to one of said voltage and current components;

means for sampling said second input signal at predetermined instants, which are a function of unit changes in the magnitude of said first input signal, said sampling means providing the instantaneous magnitude of said second input signal at each of said predetermined instants;

means, responsive to said sampling means, for generating signal representations of said instantaneous magnitudes of said second input signal;

accumulator means for accumulating successive ones of said signal representations, said accumulator means providing totalized values which are proportional to the time integral of the product of said certain ones of the components being represented by said first and second input signals over a predetermined period of time; and

output means, responsive to said totalized values, for providing data output signals representative of the measured parameter of electrical energy quantity.

2. The meter apparatus of claim 1 wherein said signal representations are digital signals being generated by the means responsive to said sampling means.

3. The meter apparatus of claim 1 including means for detecting unit changes in the magnitude of the first input signal.

4. The meter apparatus of claim 3 including means for varying the magnitude from which each unit change in the magnitude of the first input signal is measured at predetermined intervals to optimize the sampling of the second input signal over a predetermined period of time.

5. The meter apparatus of claim 4 wherein the predetermined interval of varying the magnitude of the unit change is once per cycle of the first input signal.

6. The meter apparatus of claim 1 wherein the accumulator means includes:

means for adding successive ones of the signal representations of the second input signal to previously accumulated values during the time the magnitude of the first input signal is increasing; and

means for subtracting successive ones of the signal representations of said second input signal from previously accumulated values during the time the magnitude of said first input signal is decreasing to provide an accurate measurement of a parameter of an electrical energy quantity.

7. The meter apparatus of claim 1 wherein the first input signal is proportional to the time integral of e, where e is proportional to the voltage on the electrical distribution system, and the second input signal is proportional to the current drawn by a load on said distribution system and the measured parameter of electrical energy quantity is the watthours of electrical energy consumed by said load over a predetermined period of time.

8. The meter apparatus of claim 3 wherein the detecting means includes:

means for successively generating reference level voltages associated with the entire magnitude range of the first input signal, each of said reference level voltages being a constant unit of magnitude different from the preceding reference level voltage; and

means for determining when the instantaneous magnitudes of the first input signal crosses the magnitude of one of said reference level voltages, with the sampling means being responsive to said determining means to sample the second input signal at the instant said first input signal crosses the magnitude of one of said reference level voltages.

9. The meter apparatus of claim 8 wherein the reference level generating means includes means for generating successive reference level voltages which are the predetermined unit of magnitude greater than preceding reference level voltages when the magnitude of the first input signal is increasing with respect to time and which are the predetermined unit of magnitude less than preceding reference level voltages when the magnitude of the first input signal is decreasing with respect to time such that the magnitude of the present one of said reference level voltages constantly follows the magnitude of said first input signal.

10. The meter apparatus of claim 8 including means for varying the magnitude of corresponding ones of the reference level voltages by a predetermined amount at predetermined intervals to optimize the sampling of the second input signal over a predetermined period of time.

11. The meter apparatus of claim 10 wherein the predetermined interval is once per cycle of the first input signal.

12. The meter apparatus of claim 8 wherein:

the reference level generating means generates first and second reference level voltages at one time, said first and second reference level voltages having the predetermined unit of magnitude difference therebetween such that one of said first and second reference level voltages is greater than the instantaneous magnitude of the first input signal and the other of said first and second reference level voltages is less than the instantaneous magnitude of said first input signal.

13. The meter apparatus of claim 12 wherein the reference level generating means includes means responsive to the determining means, for generating third and fourth reference level voltages when the magnitude of the first input signal crosses the magnitude of one of the first and second reference level voltages, with said third and fourth reference level voltages having the predetermined unit of magnitude, difference therebetween and, further, having magnitudes which are said predetermined unit of magnitude difference from the magnitudes of said first and second reference level voltages, respectively.

14. A method of measuring a parameter of an electrical energy quantity occurring in an alternating current electrical distribution system comprising the steps of:

providing first and second input signals representative of certain ones of the voltage and current components occurring in said electrical distribution system, with said first input signal being proportional to the time integral of one of said voltage and current components and said second input signal being directly proportional to one of said voltage and current components;

sampling said second input signal at predetermined instants, which are a function of unit changes in the magnitude of said first input signal, to provide instantaneous magnitudes of said second input signal at each of said predetermined instants;

generating signal representations of said instantaneous magnitudes of said second input signal at each of said predetermined instants; and

totalizing successive ones of said signal representations of said second input signal to provide totalized values which are equivalent to the time integral of the product of said certain ones of the components being represented by said first and second input signals over a predetermined period of time in order to measure a parameter of electrical energy quantity occurring in said electrical distribution system.

15. The method of claim 14 further including the step of detecting unit changes in the magnitude of the first input signal.

16. The method of claim 14 wherein the step of accumulating successive ones of the signal representations of the second input signals includes the steps of:

adding successive ones of said signal representations of said second input signal to previously accumulated values during the time the magnitude of the first input signal is increasing; and

subtracting successive ones of said signal representations of said second input signal from previously accumulated values during the time the magnitude of said first input signal is decreasing.

17. The method of claim 15 wherein the step of detecting unit changes in the magnitude of the first input signal includes the steps of:

generating successive reference level voltages, each having a constant unit of magnitude difference therebetween, associated with the entire magnitude range of said first input signal; and

determining when the magnitude of said first input signal crosses the magnitude of one of said reference level voltages to initiate the sampling of the second input signal.

18. The method of claim 17 further including the step of varying the magnitude of corresponding ones of the reference level voltages at predetermined intervals of the first input signal to optimize the sampling of the second input signal over a predetermined period of time.

19. Meter apparatus for measuring a parameter of an electrical energy quantity occurring in an electrical power distribution system comprising:

input means for generating first and second input signals representative of certain ones of the voltage and current components of said electrical energy quantity occurring on said electrical power distribution system, with said first input signal being proportional to the time integral of time varying values of one of said voltage and current components and said second input signal being directly proportional to time varying values of one of said voltage and current components;

means for sampling said second input signal at predetermined instants, the occurrence of each predetermined sampling instant being a function of unit changes in the magnitude of said first input signal, and said sampling means providing sample values of the instantaneous magnitude of said second input signal at each of said predetermined sampling instants;

accumulator means for accumulating totalized values of successive ones of said sample values, said totalized values being proportional to the time integral of the product of said certain ones of the components being represented by said first and second input signals over a predetermined period of time; and

output means, responsive to said totalized values, for providing data output signals representative of the measured parameter of electrical energy quantity.

20. Meter apparatus for measuring a parameter of an electrical energy quantity occurring in an electrical power distribution system comprising:

input means for generating first and second input signals representative of the time varying values of certain ones of the voltage and current components of said electrical energy quantity occurring on said electrical power distribution system and wherein one of the first and second input signals is proportional to the time integral of one of said voltage and current components;

means for sampling said second input signal at predetermined instants in response to unit changes in the magnitude of said first input signal, said sampling means providing sample values of the instantaneous magnitude of said second input signal at each of the predetermined sampling instants;

accumulator means for accumulating totalized values of successive ones of said sample values;

means for selectively increasing or decreasing said totalized values of said accumulator means by the amount of the successive sample values occurring at said predetermined sampling instants when the magnitude of said first input signal is increasing or decreasing, respectively, so that said accumulator means produces totalized values being proportional to the time integral of the product of said certain ones of the components being represented by said first and second input signals over a predetermined period of time; and

output means, responsive to said totalized values, for providing data output signals representative of the measured parameter of electrical energy quantity.