US5570028A — Method for detecting faults in electrical cables …

Claim 1

Independent Claim 93 words

Apparatus for localizing faults within a power line, comprising: a) an electromagnetic sensor interface for receiving a test signal propagating through said power line and detected by an electromagnetic sensor positioned proximate to said power line; b) signal conditioning means electrically coupled to said electromagnetic sensor interface for conditioning said received test signal; c) processing means for processing said received test signal using predetermined test signal signatures to generate usable power line fault detection data; and d) communicating means responsive to said processing means for communicating said usable power line fault detection data.

Claim 2

Dependent Claim 93 words

Apparatus for localizing faults within a power line, comprising: a) an electromagnetic sensor interface for receiving a test signal propagating through said power line and detected by an electromagnetic sensor positioned proximate to said power line; b) signal conditioning means electrically coupled to said electromagnetic sensor interface for conditioning said received test signal; c) processing means for processing said received test signal using predetermined test signal signatures to generate usable power line fault detection data; and d) communicating means responsive to said processing means for communicating said usable power line fault detection data.

Claim 3

Dependent Claim 15 words

The apparatus defined by claim 1, wherein said communicating means further includes a display interface.

Claim 4

Dependent Claim 20 words

The apparatus defined by claim 2, wherein said communicating means further includes a display in communication with said display interface.

Claim 5

Dependent Claim 17 words

The apparatus defined by claim 3, wherein said display includes an ambient light and a temperature sensor.

Claim 6

Dependent Claim 19 words

The apparatus defined by claim 1, wherein said signal conditioning means includes an analog gain and anti-aliasing filtering stage.

Claim 7

Dependent Claim 19 words

The apparatus defined by claim 5, wherein said signal conditioning means includes digitally controlled front-end variable gain selection means.

Claim 8

Dependent Claim 35 words

The apparatus defined by claim 1, further including a key-scan encoder, said encoder enabling a user to control the processing by the processing means and the communication of the usable power line fault detection data.

Claim 9

Dependent Claim 22 words

The apparatus defined by claim 1, further including an analog-to-digital (A/D) converter interposed between said signal conditioning means and said processing means.

Claim 10

Dependent Claim 15 words

The apparatus defined by claim 8, wherein said processing means includes a digital signal processor.

Claim 11

Dependent Claim 38 words

The apparatus defined by claim 1, wherein said processing means includes means for performing FIR and IIR filter functions on said signal to eliminate background noise, suppress artifacts and provide discrimination to said fault detection data contained therein.

Claim 12

Dependent Claim 27 words

The apparatus defined by claim 10, wherein said means for performing said filter function separates capacitive-discharge test signal information from background noise within the fault detection data.

Claim 13

Dependent Claim 37 words

The apparatus defined by claim 11, wherein said means for performing said FIR filter function comb filters said signal at multiples of 60 Hz and notch filters said comb-filtered data at low frequency multiples of 25 Hz.

Claim 14

Dependent Claim 25 words

The apparatus defined by claim 10, wherein said means for performing a filter function performs an integration function on said signal to derive current-based information.

Claim 15

Dependent Claim 22 words

The apparatus defined by claim 13, wherein said means for performing enable discrimination between faulted and unfaulted legs at a T junction.

Claim 16

Dependent Claim 77 words

The apparatus defined by claim 12, wherein: a) said comb filter function generates a response to an input signal U n substantially equivalent to: -1/8(U.sub.n-8p +U.sub.n-7p +U.sub.n-6p +U.sub.n-5p +U.sub.n-3p +U.sub.n-2p +U.sub.n-p +U.sub.n)+U.sub.n-4p, where F s is the sampling frequency and p equals the number of samples in a 60 Hz period; and b) said IIR filter function may be described by a digital transfer function: (1+z.sup.-1)/[1-((1-δ)z.sup.-1 /(1+δ)], where δ=1/2τF S and τ is an integrator time constant.

Claim 17

Dependent Claim 31 words

The apparatus defined by claim 15, wherein said means for performing said IIR filter function may be described by a digital transfer function substantially equivalent to: (1+2z.sup.-1 +z.sup.-2)/[1-(2z.sup.-1 (1-δ))/(1+δ)+((1-δ)/(1+δ)).sup.2 z.sup.-2 ].

Claim 18

Dependent Claim 35 words

The apparatus defined by claim 1, wherein said processing means includes means to perform an FIR comb filter function on said test signal which removes odd-order 60 Hz noise harmonics from said fault detection data.

Claim 19

Dependent Claim 50 words

The apparatus defined by claim 17, wherein said processing means includes means for providing a narrowband line detector function to detect test signal energy within said test signal at one of 120 and 240 Hz, said detector function in series with said means for performing said FIR comb filter function.

Claim 20

Dependent Claim 46 words

The apparatus defined by claim 17, wherein said FIR filter function generates a response to an input signal U n substantially equivalent to: 1/4[U.sub.n-p +(2)U.sub.n-(p/2) +U.sub.n ], where F s is the sampling frequency and p is the number of samples in a 60 Hz period.

Claim 21

Dependent Claim 19 words

The apparatus defined by claim 17, wherein said processing means further includes means for implementing an IIR filter function.

Claim 22

Dependent Claim 95 words

The apparatus defined by claim 20, wherein said IIR filter-function means includes means for distributing the data along first and second channels connected which each direct data processed by each function to an adder function where said data processing is added and provided to a function for generating a signal representative of a square root of a value output by said adder, and wherein said first channel performs a Co filter function and a signal data value squaring function and said second channel performs a Quad filter function and a signal data value squaring function.

Claim 23

Dependent Claim 76 words

The apparatus defined by claim 21, wherein said Co filter function is described with a digital transfer function substantially equivalent to: [2αβ/X+2αβz.sup.-2 /X]/Y, where Y equals [1+(2z -1 (ω o 2 -β 2 )/X)+(z -2 β 2 -2αβ+ω 2 o ))]/X, X equals B 2 +2αβ+ω 2 o , ω o equals the peak frequency in radians/sec, α equals two pi (π) times the half-power line width and βequals ω o cot(ω o /F S ).

Claim 24

Dependent Claim 24 words

The apparatus defined by claim 22, wherein said Quad filter function is described with a digital transfer function substantially equivalent to: 2αω.sub.o (1+2z.sup.-1 +z.sup.-2)/XY.

Claim 25

Dependent Claim 46 words

The apparatus defined by claim 19, further including in series with said FIR filter function: a) means for performing an IIR filter function upon said response; b) means for generating an absolute value of said filtered response; and c) means for low-pass filtering said filtered response.

Claim 26

Dependent Claim 70 words

The apparatus defined by claim 24, wherein said IIR filter function displays a transfer function substantially equivalent to: [2αβ/X-2αβZ.sup.-2 /X]/Y, where Y equals: 1+(2z -1 (ω 2 o β 2 )/X)+(z -2 (β 2 -2αβ+ω 2 o )/X), X=β 2 +2αβ+ω 2 o , ω o equals the peak frequency, α equals two pi (π) times the half-power line width and β equals ω o cot(ω o /F S ).

Claim 27

Dependent Claim 24 words

The apparatus defined by claim 22, wherein said peak frequency is one of: (a) 240π radians per second, and (b) 480π radians per second.

Claim 28

Dependent Claim 25 words

The apparatus defined by claim 3, wherein said display is manufactured according to one of the following technologies: electroluminescent, plasma vacuum fluorescent and liquid crystal.

Claim 29

Dependent Claim 20 words

The apparatus defined by claim 3, wherein said display is a liquid crystal display manufactured using super twisted nematic technology.

Claim 30

Dependent Claim 11 words

The apparatus defined by claim 1, wherein said apparatus is hand-held.

Claim 31

Dependent Claim 11 words

The apparatus defined by claim 1, wherein said apparatus is vehicle-mounted.

Claim 32

Dependent Claim 35 words

The apparatus defined by claim 17, wherein said processing means includes means for performing a matched filtering function to provide enhanced processing ability and enable identification of current flow direction within said cable under test.

Claim 33

Dependent Claim 34 words

The apparatus defined by claim 31, wherein said sensor interface and said processing means include cooperating means for identifying and compensating for variances in a distance from said apparatus to said cable under test.

Claim 34

Dependent Claim 35 words

The apparatus as defined by claim 10, wherein said sensor interface and said processing means include cooperating means for identifying and compensating for variances in a distance from said apparatus to a cable under test.

Claim 35

Dependent Claim 15 words

The apparatus defined by claim 1, further including an electromagnetic sensor connected to said interface.

Claim 36

Independent Claim 70 words

A method for localizing a fault within an electrical power cable, comprising the steps of: a) detecting a test signal propagating along said electrical power cable; b) conditioning said detected test signal within signal conditioning means to generate a data signal; c) processing said data signal within signal processing means using predetermined test signal signatures to generate user display data; and d) communicating said user display data to a user.

Claim 37

Independent Claim 70 words

A method for localizing a fault within an electrical power cable, comprising the steps of: a) detecting a test signal propagating along said electrical power cable; b) conditioning said detected test signal within signal conditioning means to generate a data signal; c) processing said data signal within signal processing means using predetermined test signal signatures to generate user display data; and d) communicating said user display data to a user.

Claim 38

Dependent Claim 21 words

The method defined by claim 35, wherein said conditioning includes anti-alias filtering and providing a gain to said detected test signal.

Claim 39

Dependent Claim 26 words

The method defined by claim 36, further including a step of converting said test signal to a digital data signal within an analog to digital converter.

Claim 40

Dependent Claim 22 words

The method defined by claim 37, wherein said step of processing includes processing said digital signal data within a digital signal processor.

Claim 41

Dependent Claim 36 words

The step of claim 37, wherein said step of processing includes generating digital user display data and said step of communicating includes converting said digital data to an analog signal within a digital to analog converter.

Claim 42

Dependent Claim 29 words

The method defined by claim 35, wherein said step of processing includes performing a comb filtering function on said data signal to eliminate periodic noise from said data signal.

Claim 43

Dependent Claim 21 words

The method defined by claim 40, wherein said performing includes eliminating noise at multiples of 60 Hz from said data signal.

Claim 44

Dependent Claim 34 words

The method defined by claim 41, wherein said performing includes performing a second filtering function upon said comb-filtered data signal to allow discrimination between faulted and unfaulted legs of said cable at a T-junction.

Claim 45

Dependent Claim 18 words

The method defined by claim 42, wherein said performing said second filtering function includes integrating said comb-filtered data.

Claim 46

Dependent Claim 28 words

The method defined by claim 42, wherein said performing further includes performing a notch filtering function on said data signal to remove period noise at several low frequencies.

Claim 47

Dependent Claim 15 words

The method defined by claim 44, wherein said frequencies are at multiples of 25 Hz.

Claim 48

Dependent Claim 22 words

The method defined by claim 40, wherein said performing includes removing noise at odd multiples of 60 Hz from said data signal.

Claim 49

Dependent Claim 35 words

The method defined by claim 46, wherein said performing includes performing a second filtering function upon said data signal whereby the effective signal energy at one of 120 Hz and 240 Hz is substantially extracted.

Claim 50

Dependent Claim 35 words

The method defined by claim 46, wherein said performing includes performing a matched filtering function on said data signal to identify replicas of a known test set signal in a background of essentially periodic noise.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1999-10-29	2000-04-29	2000-10-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2003-10-29	2004-04-29	2004-10-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2007-10-29	2008-04-29	2008-10-29	$7700.00	Window Closed / Lapsed

Method for detecting faults in electrical cables and apparatus for implementing same

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