High impedance fault analyzer in electric power distribution
First Claim
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1. A method for detecting an abnormality in a network for distributing a.c. electric power at a fundamental frequency, said method comprising the steps of:
- (a) producing a signal representing the fundamental frequency of a voltage occurring in said network;
(b) producing a signal representing an harmonic of a current occurring in said network;
(c) comparing the phase relationship between said fundamental voltage and harmonic current representing signals; and
(d) producing an indication in response to predetermined change in said phase relationship indicating the occurrence of abnormality in the network.
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Abstract
A system and method is disclosed for detecting an abnormality in a network for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal representing the fundamental frequency and another signal representing a harmonic current occurring in the network. The phase relation between the fundamental voltage and harmonic current representing signal are compared. The system produces a signal indicating the occurrence of a high impedence fault in response to a predetermined change in the compared phase relationship.
119 Citations
61 Claims
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1. A method for detecting an abnormality in a network for distributing a.c. electric power at a fundamental frequency, said method comprising the steps of:
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(a) producing a signal representing the fundamental frequency of a voltage occurring in said network; (b) producing a signal representing an harmonic of a current occurring in said network; (c) comparing the phase relationship between said fundamental voltage and harmonic current representing signals; and (d) producing an indication in response to predetermined change in said phase relationship indicating the occurrence of abnormality in the network. - View Dependent Claims (2, 3, 4, 5)
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6. A system for detecting an abnormality in a network for distributing a.c. electric power at primarily a fundamental frequency, said system comprising:
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(a) means for producing a signal representing the fundamental frequency of a voltage occurring in said network; (b) means for producing a signal representing an harmonic of a current occurring in said network; (c) means for comparing phase relationship between said fundamental voltage representing signal and said harmonic current representing signal, and (d) means for producing an indication in response to said phase comparison indicating a change in phase relationship. - View Dependent Claims (7, 8, 9)
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10. A method for detecting an abnormality in an electric power distribution network energized at a fundamental frequency, said method comprising:
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(a) producing a signal representing the phase of an harmonic of a voltage occurring in said network; (b) producing a signal representing an harmonic of a current occurring in said network; (c) comparing phase between said voltage harmonic and said current harmonic representing signals, and (d) producing an indication when said phase comparison changes by a predetermined amount in response to abnormality. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A system for detecting an abnormality in an electric power distribution network energized primarly at a fundamental frequency, said system comprising:
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(a) circuitry for producing a signal representing the phase of an harmonic of a voltage occurring in said networks; (b) circuitry for producing a signal representing an harmonic of a current occurring in said network; (c) circuitry for comparing phase between said voltage harmonic and said current harmonic representing signals, and (d) circuitry for producing an indication of change in said phase comparison. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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26. A fault analysis system for detecting a high impedance abnormality in an electric powered network, by determining a phasor current signature of such abnormality distinct from ambient harmonics and other causes, said system comprising:
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(a) circuitry for producing a first signal representing a fundamental system frequency voltage; (b) circuitry for producing a second signal representing one harmonic of a current of said fundamental frequency; (c) circuitry for producing a third signal representing phase relation between said first and second signals; (d) circuitry for determining average ambient values of said third signal; (e) circuitry for determining the amplitude value of said second signal; (f) circuitry for determining the average ambient value of said amplitude of said second signal; (g) circuitry for determining substantially present, short term average values of said second signal and of said third signal; (h) circuitry for comparing said substantially present average values to the respective average ambient values of said second and third signals; (i) circuitry for determining when changes in said ambient value of said second and said third signals, respectively, are within a predetermined range of values, and (j) circuitry for providing and output signal when said changes are within said predetermined range of values. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33)
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34. A fault analyzer system for an electric power network, for detecting high impedance abnormalities in said network by detecting a phasor signature of such abnormality distinct from other sources of system disturbance, said system comprising:
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(a) circuitry for producing a first reference signal representing substantially instantaneous power system voltage at a point in the system; (b) circuitry for producing a second signal representing a substantially instantaneous power system current; (c) circuitry for producing a third signal representing substantially instantaneous power system voltage at a point near the point of current signal measurement; (d) means for filtering and processing said first, second and third signals to produce signals representing the phasor values of a harmonic component in said second and third signals with respect to a fundamental component of said reference first signal, irrespective of nominal changes in electric power system frequency and without ambiguity due to harmonic frequency difference; (e) circuitry for averaging said phasor values of said harmonic signals to produce signals representing the ambient values of each; (f) circuitry for determining change in ambient value of each of said harmonic phasor signals; (g) circuitry for establishing limits of such changes of said harmonic signals in both magnitude and phase relationship with respect to said reference first signal, and (h) circuitry for determining when said changes in said harmonic phasor are within said limits thereby indicating a high impedance fault type abnormality on the circuit under observation. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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45. An analyzer system for detecting a high impedance abnormality in an electric power network having a fundamental frequency by determining a harmonic phasor current signature of such abnormality distinct from ambient harmonics in said power system, said analyzer system comprising:
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(a) circuitry for producing a first signal representing a substantially instantaneous power system voltage; (b) circuitry for producing a second signal representing a substantially instantaneous power system current; (c) means for scaling each of said first and second signals to respective values suitable for ensuing processing; (d) circuitry for producing a third signal by filtering substantially all frequencies except a harmonic frequency component of said system fundamental frequency from said first signal; (e) circuitry for producing a fourth signal by filtering substantially all frequencies except a harmonic component of said system fundamental frequency from said second signal; (f) circuitry for producing a fifth signal representing phase relation between said fourth harmonic current signal and said third harmonic voltage signal; (g) circuitry for determining the average ambient value of said fifth signal; (h) circuitry for determining the respective amplitude values of said third and fourth signals; (i) circuitry for determining the average ambient values of said magnitudes of said third and fourth signals; (j) circuitry for determining, over a relatively short period of time, the present value of said third and fourth signals and of said fifth signal; (k) circuitry for comparing said present averaging values to the respective average ambient values of said third, fourth and fifth signals; (l) means for determining when the changes in said relatively short term averaged value of said fourth signal and said fifth signal, respectively, are each within a predetermined range of values, with respect to said respective ambient values; (m) circuitry for providing an output signal in response to both of said fourth and fifth signal when changes are within a predetermined range of values; (n) further means for ratioing the change in amplitude of said third signal with respect to said fourth signal; (o) means for determining when said ratio of said change in harmonic voltage to current is within a preset range; (p) means for producing an output signal when said ratio and said change in relative phase angle are both within said preset range. - View Dependent Claims (46)
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47. A method for detecting an abnormality in a network for distributing AC electrical power at a fundamental frequency, said method comprising the steps of:
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(a) producing a signal representing the fundamental frequency component of a voltage occurring in said network; (b) producing a signal representing a phasor of an harmonic of a current occurring in the network; (c) monitoring said signal indicating said harmonic current phasor with respect to the fundamental voltage signal, and (d) producing an indication in response to the occurrence of a predetermined amount of change of said harmonic current phasor signal with respect to said fundamental voltage signal.
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48. A method for detecting an abnormality in a network for distributing AC electrical power of a fundamental frequency, said method comprising the steps of:
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(a) measuring both the magnitude and phase components of a phasor defining an harmonic current of the network, and (b) producing an indication in response to a predetermined change of said phasor. - View Dependent Claims (49)
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50. A method for detecting an abnormality in a network for distributing AC electrical power at a fundamental frequency, said method comprising the steps of:
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(a) producing a signal representing a phasor of a harmonic of a voltage occurring in the network; (b) producing a signal representing a phasor of an harmonic of a current occurring in the network; (c) monitoring change in the relative value of said harmonic current phasor signal with respect to the harmonic voltage phasor signal, and (d) producing an indication in response to the occurrence of a predetermined amount of said change.
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51. A fault analyzer system for an electric power network, for detecting a phasor signature of such abnormality distinct from other sources of system disturbance, said system comprising:
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(a) means for producing a first reference signal representing substantially instantaneous power system voltage at a point in the system; (b) means for producing a second signal representing a substantially instantaneous power system current; (c) means for producing a third signal representing substantially instantaneous power system voltage at a point near the point of current signal measurement; (d) means for filtering and processing said first, second and third signals to produce signals representing the phasor values of a harmonic component in each of said second and third signals with respect to a fundamental component of said reference first signal, irrespective of nominal changes in electric power system frequency and without ambiguity due to harmonic frequency difference; (e) means for averaging said phasor values of said harmonic signals to produce signals representing the ambient values of each; (f) means for determining change in ambient value of each of said harmonic phasor signals; (g) means for establishing limits of such changes of said harmonic signals in both magnitude and phase relationship with respect to said reference first signal, and (h) a tracking oscillator coupled for phase locking to the fundamental frequency component of said first reference signal for generating a third harmonic signal having zero crossings substantially coincident with said system fundamental frequency voltage zero crossings irrespective of variations in the electric power system nominal frequency, and (i) means for determining when said changes in said harmonic phasors are within said limits thereby indicating a high impedance fault type abnormality on the network under observation. - View Dependent Claims (52, 53)
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54. A method for detecting an abnormality in a network for distributing a.c. electric power at a fundamental frequency, said method comprising the steps of:
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(a) producing a signal representing the fundamental frequency of a voltage occurring in said network; (b) producing a signal representing an harmonic of a current occurring in said network; (c) producing a signal representing the phase difference between said fundamental frequency voltage and harmonic current representing signals; (d) detecting the degree of network abnormality by measuring change in said signal representing said phase difference, and (e) producing an indication in response to a predetermined amount of change in said phase difference signal.
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55. A method for detecting an abnormality in a network for distributing AC electrical power at a fundamental frequency, said method comprising the steps of:
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(a) measuring both the phase component, with respect to a system voltage of the network, and the magnitude component, of a phasor defining an harmonic current of the network, and (b) producing an indication in response to a predetermined change of said phasor.
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56. A system for detecting an abnormality in a network for distributing AC electrical power at a fundamental frequency, said system comprising:
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(a) means for measuring both the magnitude and phase components of a phasor defining an harmonic current of the network, and (b) means for producing an indication in response to a predetermined change of said phasor.
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57. A system for detecting an abnormality in a network for distributing AC electricl power at a fundamental frequency, said system comprising:
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(a) means for producing a signal representing the fundamental frequency component of a voltage occurring in said network; (b) means for producing a signal representing a phasor of an harmonic of a current occurring in the network; (c) means for monitoring said signal indicating said harmonic phasor with respect to the fundamental voltage signal, and (d) means for producing an indication in response to the occurrence of a predetermined amount of change of said harmonic current phasor signal with respect to said fundamental voltage signal.
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58. A system for detecting an abnormality in a network for distributing AC electrical power at a fundamental frequency, said system comprising:
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(a) means for producing a signal representing a phasor of an harmonic of a voltage occurring in the network; (b) means for producing a signal representing a phasor of an harmonic of a current occurring in the network; (c) means for monitoring change in the relative value of said harmonic current phasor signal with respect to the harmonic voltage phasor signal, and (d) means for producing an indication in response to the occurrence of a predetermined amount of said change.
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59. A fault analysis system for detecting a high impedance abnormality in an electric power network, by determining a phasor current signature of such abnormality distinct from ambient harmonics and other causes, said system comprising:
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(a) means for producing a first signal representing a fundamental system frequency voltage; (b) means for producing a second signal representing one harmonic of a system current; (c) means for producing a third signal representing phase relation between said first and second signals; (d) means for determining average ambient value of said third signal; (e) means for determining the amplitude value of said second signal; (f) means for determining the average ambient value of said amplitude of said second signal (g) means for determining short term average values of said second signal and of said third signal; and (h) means for comparing said short term average values to the respective average ambient values of said second and third signals. - View Dependent Claims (60, 61)
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Specification