Patent ID: 8680842
Filing Date: 2014-03-25
Classification: G01R

Abstract:
1. A method for estimating a total harmonic distortion in an alternating current (AC) electrical circuit that receives a current or a voltage having a fundamental frequency, the method comprising: measuring the current or the voltage received by the AC electrical circuit in samples taken at a predetermined sample rate for each cycle of the fundamental frequency occurring for at least one second to produce a set of measurements; filtering the set of measurements by determining a magnitude of the measured current or a magnitude of the measured voltage at a harmonic frequency of the measured current or voltage, wherein the harmonic frequency is an integer multiple of the fundamental frequency, wherein the determining is carried out by applying a narrow band algorithm to the set of measurements, the narrow band algorithm having a frequency response that includes the harmonic frequency, wherein the frequency response is characterized by a frequency band that does not exceed one hertz; calculating the total harmonic distortion according to a function that includes the determined magnitude; and storing the total harmonic distortion in a memory.