Substation load distribution monitor system

Claim 1

A method of monitoring power distribution equipment carrying voltage and current to distribute electrical power, said monitoring method comprising the steps of: sampling periodic waveforms representative of said current and said voltage within said power equipment to obtain samples which are substantially equally spaced in time so that said samples have a sample period, said samples having magnitudes and wherein a value derived from said magnitudes of said samples is used as feedback to maintain a sample rate such that a period of the periodic waveforms is substantially an integer multiple of said sample period; and analyzing said sample values by means of a discrete Fourier Transform to obtain a relative phase between the voltage and current waveforms.

Claim 2

A method of monitoring power distribution equipment carrying voltage and current to distribute electrical power, said monitoring method comprising the steps of: sampling periodic waveforms representative of said current and said voltage within said power equipment to obtain samples which are substantially equally spaced in time so that said samples have a sample period, said samples having magnitudes and wherein a value derived from said magnitudes of said samples is used as feedback to maintain a sample rate such that a period of the periodic waveforms is substantially an integer multiple of said sample period; and analyzing said sample values by means of a discrete Fourier Transform to obtain a relative phase between the voltage and current waveforms.

Claim 3

A method of determining the relative phase between a periodic voltage waveform and a periodic current waveform carried in power equipment, said determining method comprising the steps of: simultaneously sampling said periodic current waveform and said periodic voltage waveform at a sampling rate to obtain first and second sets of sample values, said first set of sample values comprising a representation of said periodic current waveform with discrete sample values substantially equally spaced in time to define a first sample period, said second set of sample values comprising a representation of said periodic voltage waveform with discrete sample values substantially equally spaced in time to define a second sample period and wherein a feedback value derived from said first and second sets of sample values is used as feedback to automatically adjust said sample rate to insure that a period of said periodic current waveform is substantially an integer multiple of said first sample period and a period of said periodic voltage waveform is substantially an integer multiple of said second sample period; applying a discrete Fourier Transform to the first and second sets of sample values of said periodic voltage waveform and said periodic current waveform to obtain a phase of said periodic voltage waveform and a phase of said periodic current waveform; and comparing the phase of said periodic voltage waveform and said periodic current waveform to obtain a relative phase between said periodic voltage waveform and said periodic current waveform.

Claim 4

A method of determining the relative phase between a periodic voltage waveform and a periodic current waveform carried in power equipment, said determining method comprising the steps of: simultaneously sampling said periodic current waveform and said periodic voltage waveform at a sampling rate to obtain first and second sets of sample values, said first set of sample values comprising a representation of said periodic current waveform with discrete sample values substantially equally spaced in time to define a first sample period, said second set of sample values comprising a representation of said periodic voltage waveform with discrete sample values substantially equally spaced in time to define a second sample period and wherein a feedback value derived from said first and second sets of sample values is used as feedback to automatically adjust said sample rate to insure that a period of said periodic current waveform is substantially an integer multiple of said first sample period and a period of said periodic voltage waveform is substantially an integer multiple of said second sample period; applying a discrete Fourier Transform to the first and second sets of sample values of said periodic voltage waveform and said periodic current waveform to obtain a phase of said periodic voltage waveform and a phase of said periodic current waveform; and comparing the phase of said periodic voltage waveform and said periodic current waveform to obtain a relative phase between said periodic voltage waveform and said periodic current waveform.

Claim 10

A method of taking an integer number of sample values per cycle of a periodic voltage or current waveform carried by power equipment, said method comprising the steps of: sampling said periodic voltage or current waveform at a selected sampling rate corresponding to a first expected frequency to obtain a first set of samples equally spaced in time to define a first sample period and covering substantially a first cycle of said periodic voltage or current waveform; transforming the samples from said first set of samples by means of a discrete Fourier Transform to obtain a first X transform value and a first Y transform value; sampling said periodic voltage or current waveform at said selected sampling rate to obtain a second set of samples equally spaced in time to define a second sample period, said second set of samples covering at least a portion of a second cycle of said periodic voltage or current waveform; transforming at least one of the samples from said second set of samples by means of a discrete Fourier Transform to obtain a second X transform value and a second Y transform value; comparing said first Y transform value with said second X transform value; and adjusting said selected sampling rate in response to said comparison to insure that a period of said periodic voltage or current waveform is substantially an integer multiple of said first and second sample periods.

Claim 11

A method of taking an integer number of sample values per cycle of a periodic voltage or current waveform carried by power equipment, said method comprising the steps of: sampling said periodic voltage or current waveform at a selected sampling rate corresponding to a first expected frequency to obtain a first set of samples equally spaced in time to define a first sample period and covering substantially a first cycle of said periodic voltage or current waveform; transforming the samples from said first set of samples by means of a discrete Fourier Transform to obtain a first X transform value and a first Y transform value; sampling said periodic voltage or current waveform at said selected sampling rate to obtain a second set of samples equally spaced in time to define a second sample period, said second set of samples covering at least a portion of a second cycle of said periodic voltage or current waveform; transforming at least one of the samples from said second set of samples by means of a discrete Fourier Transform to obtain a second X transform value and a second Y transform value; comparing said first Y transform value with said second X transform value; and adjusting said selected sampling rate in response to said comparison to insure that a period of said periodic voltage or current waveform is substantially an integer multiple of said first and second sample periods.