Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Patent
1996-04-24
1998-04-21
Brown, Glenn W.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
324 7711, G01R 1925, G01R 2300
Patent
active
057421560
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a digital process for obtaining a measured parameter from an electric signal having a predetermined rated frequency, and more particularly wherein: values with a scanning frequency that is generated by a clock generator and corresponds to N times the rated frequency of the electric signal, converter and analyzer.
BACKGROUND INFORMATION
A digital process for obtaining a measured parameter from an electric signal is described, for example, in the book by P. Profos and T. Pfeifer, Technology!, 1992, pages 404 and 405. In this known method, in order to measure the effective value, an electric signal formed from an electric voltage with a predetermined frequency is scanned and subjected to an analog-to-digital conversion and then used to calculate the effective voltage value in an analyzer. An effective current value and the electric power can be determined with this known method.
Other known processes of this type are described in the book by R. Electronic Measurement Technology!, 5th edition, 1990, pages 307 to 311 and the book by R. Lappe and F. Fischer Leistungselektronik-Messtechnik
The frequency measurement can be performed as described in the article by J. Heydeman and E. N. Lulf "Microprocessor Based Underfrequency Relaying," Delft University of Technology, the Netherlands, published in IEE Conference Publication No. 249, Third Internal Conference on Developments in Power System Protection, 1985, pages 24 to 28. The voltage is scanned with a frequency of 2.5 kHz, which is accomplished by programming the microprocessor to generate interrupts with this frequency. The passage of the voltage through zero is detected by the software. The frequency of the voltage can then be calculated from the number of pulses counted during one period of the voltage by forming the ratio of the scanning frequency to the number of pulses per period. The accuracy of this known method of frequency measurement is determined first by the accuracy that can be achieved in determining the length of the period and second by the scanning frequency.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a digital method of determining a measured value from an electric signal, so the measured value can be determined with a much greater accuracy than has been possible with the known method described above, and this can be accomplished without any significant increase in effort or expense and without requiring a longer analysis time.
To achieve this object, the following measures are implemented according to the present invention in a digital process of the type described above: electric signal is determined with a frequency measurement device, measured value, of the clock generator to the derived measured value is formed in a quotient forming circuit and divider installed between the clock generator and the clock input of an analog-digital converter so that the frequency corresponding to the derived measured value is sent to the clock input, where a change in the divider ratio is not implemented until after several periods of the electric signal have elapsed.
It is known from German Patent 41 22 399 A1 that the scanning frequency in a process for digital measurement of voltages and currents in a power supply system can be derived from the instantaneous frequency of the variable parameter measured in order to be able to perform relatively accurate measurements, German Patent No. 41 22 399 A1, however, does not contain any reference to a clock generator or a downstream quotient forming circuit that receives a measured parameter derived from the instantaneous frequency of the electric signal measured.
An important advantage of the process according to the present invention is that regardless of the instantaneous frequency of the analog electric signal measured in each case, it uses a scanning frequency corresponding to N times the instantaneous frequency of the electric signal. This yields a great increase in measurement accuracy because the number of scans pe
REFERENCES:
patent: 4057756 (1977-11-01), Ley et al.
patent: 4093988 (1978-06-01), Scott
patent: 4563637 (1986-01-01), DeBortoli et al.
patent: 5307284 (1994-04-01), Brunfeldt et al.
Taha et al, "Direct Digital RMS Measuring Device", International Journal of Electronics, vol. 59, No. 2, Aug. 1985, pp. 199-210. of Industrial Measurement Technology!," 1992 pp. 403 to 405. (month unavailable). Electronic Measurement Technology!," 5th edition, 1990, pp. 307 to 312. (month unavailable). Measurement Technology!," 2nd edition, 1993, p. 242. (month unavailable).
J. Heydeman and E. N. Lulf, "Microprocessor Based Underfrequency Relaying," Delft University of Technology, the Netherlands, published in IEE Conference Publication No. 249, Third Internal Conference on Developments in Power System Protection, 1985, pp. 24 to 28. (month unavailable).
Brown Glenn W.
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