Patent ID: 8024157

Claim:
A method for judging occurrence of voltage disturbance, comprising: storing digitized point values of a voltage reference waveform on a reference waveform storage unit of a device configured to judge an occurrence of a voltage disturbance in electric power measurement equipment; detecting actual voltage values and converting, in a voltage detection unit of the device, by digitization, actual voltage values into point values of the actual voltage which are in one-to-one correspondence with the stored digitized point values of the reference waveform; comparing the point values, in a point value comparison unit of the device, of the actual voltage values with the corresponding point values of the reference waveform; and judging occurrence of a voltage disturbance, in a disturbance judgment unit of the device, if, for N successive points, differences between said point values of the actual voltage and said point values of the reference waveform, obtained from the comparison, are all greater than a disturbance threshold, wherein N is an integer greater than 0, wherein, said reference waveform updating condition is that: the detected positive peak value of the actual voltage waveform is greater than a positive peak threshold and the negative peak value thereof is smaller than a negative peak threshold, and the differences between the values of the actual voltage and said corresponding point values of the reference waveform are greater than a distortion threshold.