Harmonic-adjusted power factor meter

• US 5,298,856 A
• Filed: 10/06/1992
• Issued: 03/29/1994
• Est. Priority Date: 02/25/1992
• Status: Expired due to Fees

• Current Assignee: Basic Measuring Instruments, Inc.
• Original Assignee: Basic Measuring Instruments, Inc.
• Inventors: McEachern, Alexander, Grady, W. Mack
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US07/957,274
• Time in Patent Office: 539 Days
• Field of Search: 324/116, 324/126, 324/137, 324/141, 324/142, 364/483, 340/646
• US Class Current: 324/142
• CPC Class Codes: G01R 21/006 Measuring power factor

Abstract

An electric power measuring system wherein power factor measurements are adjusted to reflect the adverse economic effects of harmonic currents and voltages. Well-known techniques are used to acquire frequency spectra that represent the voltages and currents present at the measuring point. These spectra are weighted in such a way that non-fundamental currents are increased and non-fundamental voltages are decreased. The weighted spectra are used to calculate a harmonic-adjusted volt-ampere measurement, which is then accumulated to form a harmonic-adjusted volt-ampere-hour measurement. The weighting functions for voltage and current are selected to approximate the economic impact on the AC power generating, transmission, and distribution system of nonfundamental currents and voltages. The resulting harmonic-adjusted volt-ampere-hour measurement is used to calculate a harmonic adjusted power factor measurement.

Claims

1. A method of measuring electric power consumed by a consumer, comprising the steps of:

a. measuring time-domain watt-hour consumption;

b. measuring time-domain volt-ampere-hour consumption;

c. calculating a frequency-domain power factor including one or more non-fundamental currents comprising a function of a ratio of watt-hours to volt-ampere-hours coupled to receive a data signal from the first means and the second means; and

d. adjusting the power factor in a predetermined manner related to the non-fundamental current.

2. The method according to claim 1 wherein the steps of measuring time-domain watt-hour consumption and measuring time-domain volt-ampere-hour consumption include sensing time-domain current consumed by the consumer and sensing time-domain voltage consumed by the consumer.

3. The method according to claim 2 wherein the step of adjusting the power factor includes storing a current adjustment table and a voltage adjustment table.