System for analyzing and locating partial discharges

Abstract

A sensor detects partial discharges (PDs) in an electrical power system and generates a corresponding analog electrical signal. A data acquisition component receives the signal from the sensor and converts it to digitized zero span data for a series of uniformly spaced frequencies in a frequency spectrum of interest. A digital signal processing component receives the digitized zero span data, analyzes such data, and generates a corresponding phase resolved spectrum signal in three dimensional format including dimensions of amplitude, phase and frequency for each of the uniformly spaced frequencies. A display component receives the analyzed data stream from the processing component and actuates one or more displays from which characteristics of the PD can be identified, such as different types of PDs from different sources, and information on the location of a PD relative to the sensor.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A method for analyzing a partial discharge (PD) in an electrical system receiving electric power at a characteristic power frequency, which comprises:
 (1) receiving an electrical PD signal from a sensor configured and positioned to sense a PD in an electrical system over a measured frequency range;   (2) converting the electrical PD signal to a digitized zero span data signal having digital zero span data for each of several frequencies in a frequency range of interest, said frequency range being within the measured frequency range; and   (3) sorting the digital zero span data so as to obtain a phase resolved spectrum signal in three dimensional format including dimensions of amplitude, phase and frequency for each of the several frequencies in the frequency range of interest.   
     
     
         2 . The method of  claim 1 , including, between steps (1) and (2), de-noising the digitized zero span data signal. 
     
     
         3 . The method of  claim 1 , including, following step (2), automatically identifying one or more types of PDs represented in the phase resolved spectrum signal by source clustering the digital zero span data for each of the several frequencies in the frequency range of interest, automatically computing the frequency bandwidth for each of said one or more types of PDs, followed by automatically source grouping the digital zero span data for each of the one or more types of PDs identified. 
     
     
         4 . A method for analyzing a partial discharge in a power cable receiving electric power at a characteristic power frequency, which comprises:
 (1) receiving an electrical PD signal from a sensor configured and positioned to sense a PD in an electric power cable over a measured frequency range;   (2) converting the electrical PD signal to a digitized zero span data signal having digital zero span data for each of several frequencies in a frequency range of interest, said frequency spectrum being within the measured frequency range;   (3) sorting the digital zero span data so as to obtain a phase resolved spectrum signal in three dimensional format including dimensions of amplitude, phase and frequency for each of the several frequencies in the frequency range of interest.   
     
     
         5 . The method of  claim 4 , including, following step (2), automatically identifying one or more types of PDs represented in the phase resolved spectrum signal, followed by automatically computing the frequency bandwidth for each of said one or more types of PDs. 
     
     
         6 . The method of  claim 5 , including automatically calculating an estimate of a distance along the electric power cable from a source of at least one of the one or more types of PDs to the location of the sensor and displaying the distance calculated in human readable form. 
     
     
         7 . A method for analyzing a partial discharge (PD) in an electrical system receiving electric power at a characteristic power frequency, which comprises:
 (1) acquiring a digitized zero span data signal representing the PD and having digital zero span data for each of several frequencies in a frequency range of interest, wherein adjacent frequencies are separated by a uniform frequency amount over the entire frequency range of interest; and   (2) processing the digital zero span data so as to obtain a phase resolved spectrum signal in three dimensional format including dimensions of amplitude, phase and frequency for each of said several frequencies in said frequency range of interest.   
     
     
         8 . The method of  claim 7 , wherein the uniform frequency amount is no greater than 5 MHz and the entire frequency range of interest is at least 100 MHz. 
     
     
         9 . The method of  claim 7 , including using the phase resolved spectrum signal to actuate a display in three dimensional format including dimensions of amplitude, phase and frequency for each of the several frequencies in the frequency range of interest.