Method for discriminating abnormal current including arc current in AC load circuit and apparatus for executing the same

• US 20030137309A1
• Filed: 01/24/2002
• Published: 07/24/2003
• Est. Priority Date: 01/25/2001
• Status: Active Grant

• Current Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Itimura, Yasuo, Shiokaw, Akimi, Kunimoto, Yoichi
• Granted Patent: US 6,703,842 B2
• Time in Patent Office: Days
• US Class Current: 324/536
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

An abnormal current discriminating method including an arc current detecting method and the apparatus for performing the same in which the arc current method includes the steps of: extracting a predetermined transition pattern specified by the combination of fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave detected from an alternating current flowing to the AC load circuit which is sampled in a predetermined cycle and converted into a digital value, counting the number of appearances of the predetermined transition pattern, and comparing the count value with a predetermined threshold. According to which, a series arc which may be caused in a relative small current range by an apparatus cord or the like which has not been detected by an instantaneous breaker and an arc short-circuit phenomenon generated together with an arc through the contact between the cores in a cord and an interior wiring can be detected by executing simple algorithm without error detecting.

Claims

1. An abnormal current discriminating method in an AC load circuit, comprising the steps of:

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by the combination of fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a restricted predetermined period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold.

2. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the predetermined transition pattern is specified by four kinds of fluctuation patterns, that is, no fluctuation to an increase, an increase to no fluctuation, no fluctuation to a decrease, and a decrease to no fluctuation in the peak values of the three continuous half waves.

3. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the predetermined transition pattern is specified by two kinds of fluctuation patterns, that is, an increase to a decrease, and a decrease to an increase in the peak values of the three continuous half waves.

4. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the method further comprises the steps of comparing a time series array of the transition pattern thus extracted with a predetermined load fluctuation pattern, and clearing to reset the count value which is counted up when the time series array is coincident with the predetermined load fluctuation pattern.

5. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein in the case that the peak value for each half wave of the alternating current sampled and digitally converted is smaller than a predetermined threshold, such peak value is excluded, and the number of appearances of the transition pattern for other peak values of alternating currents is counted up, thereby discriminating an arc current.

6. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the peak value for each half wave of the alternating current is specified as the maximum value by executing following data processing of:

detecting a zero cross point of an alternating voltage supplied to the AC load circuit, sampling the alternating current plural times at regular intervals for a period from the zero cross point to a next zero cross point and converting the alternating current into a digital value, and further extracting the maximum value among the converted digital values of the alternating current.

7. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the peak value for each half wave of the alternating current is specified as the maximum value by executing following data processing of:

detecting a zero cross point of an alternating voltage supplied to the AC load circuit, sampling the alternating current plural times at regular intervals for a period from the zero cross point to a next zero cross point and converting the alternating current into a digital value, and calculating a mean value with a maximum value of the alternating current converted into the digital value and an instantaneous value of at least one sampled alternating current adjacent thereto.

8. The abnormal current discriminating method in an AC load circuit according to claim 6,

wherein when the alternating current sampled and converted into a digital value for a period of the zero cross point has a defined waveform sharpness (Vmax/VD):

Vmax/VD=a maximum value (Vmax) of an alternating current converted into a digital value/{a maximum value (Vmax)−

a minimum value (Vmin) in an instantaneous value of at least one sampled alternating current adjacent to the maximum value} which exceeds a predetermined threshold, such specified peak value for the period of the zero cross point is excluded and the number of appearances of the transition pattern for other peak value for each half wave of other alternating currents is counted up, thereby discriminating an arc current.

9. The abnormal current discriminating method in an AC load circuit according to claim 6,

wherein when a time interval between a time that the maximum value of the alternating current sampled and converted into a digital value and the zero cross point of the alternating voltage exceeds a predetermined threshold for the period of the zero cross point, such peak value is excluded and the number of appearances of the transition pattern for a peak value for each half wave of other alternating currents is counted up in the restricted predetermined period, thereby discriminating an arc current.

10. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein a starting point of an interval in which the number of appearances of the transition pattern is to be counted is set to be a time that a first transition pattern to be counted appears.

11. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein a starting point of a restricted interval in which the number of appearances of the transition pattern is to be counted is set to be a time that a first transition pattern to be counted appears, and furthermore, if the number of appearances of the transition pattern in the restricted interval is less than a predetermined threshold, the starting point of the interval in which the number of appearances of the transition pattern is to be counted is sequentially shifted every half wave, thereby counting the number of appearances of the transition pattern.

12. The abnormal current discriminating method in an AC load circuit according to claims 1,

wherein when a transition pattern is to be decided based on the fluctuation patterns of the three continuous half waves, at least one peak value to be a decision object in a previous transition pattern is duplicated to be the decision object.

13. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the fluctuation patterns are detected from either positive or negative three continuous half waves of the alternating current flowing to the AC load circuit.

14. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein the alternating current flowing to the AC load circuit is full wave rectified prior to the sampling step.

16. The abnormal current discriminating method in an AC load circuit according to claim 1,

wherein a starting point of the predetermined restricted period is set to be a time that the absolute value of the instantaneous current sampled and digitally converted first exceeds the preset threshold.

15. An abnormal current discriminating method in an AC load circuit, comprising the steps of:

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current;

calculating a virtual arc energy by integrating an absolute value of an instantaneous value of the current converted into the digital value in a predetermined restricted period; and

deciding that an abnormal current is generated when a virtual arc energy value thus calculated exceeds a predetermined threshold.

17. An abnormal current discriminating method in an AC load circuit, comprising the steps of:

sampling an alternating current flowing to the AC load circuit in a predetermined cycle; and

deciding that an arc short circuit or another short-circuit current occurs immediately after a value converted into a digital value corresponding to an absolute value of an instantaneous current thus sampled exceeds a predetermined value continuously a predetermined number of times.

18. An abnormal current discriminating method in an AC load circuit in which at least one abnormal discriminating method selected from first to third abnormal current discriminating method is carried out by sampling and converting into a digital value through a current-voltage converting circuit an alternating current flowing to the AC load circuit in a predetermined cycle and then executing predetermined data processing,

wherein the amplification degree of the current-voltage converting circuit is preset as the same value or as different values for carrying out the first to third method, and

wherein the first current discriminating method comprises the steps of:

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a restricted predetermined period; and

comparing the count value with a previously specified threshold and deciding the current to be an arc current when the count value exceeds the threshold, and

wherein the second current discriminating method comprises the steps of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current;

calculating a virtual arc energy by integrating an absolute value of an instantaneous value of the current converted into the digital value in a predetermined restricted period; and

deciding that an abnormal current is generated when a virtual arc energy value thus calculated exceeds a predetermined threshold, and further,

wherein the third current discriminating method comprises the steps of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a predetermined restricted period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold.

19. An abnormal current discriminating method in an AC load circuit in which first to third abnormal current discriminating method is concurrently carried out by sampling and converting into a digital value through a current-voltage converting circuit an alternating current flowing to the AC load circuit in a predetermined cycle and then executing predetermined data processing,

wherein the amplification degree of the current-voltage converting circuit is preset as the same value or as different values for carrying out the first to third method, and

wherein the first current discriminating method comprises the steps of:

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current to detect a peak value for each half wave thereof;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a predetermined restricted period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold, and

wherein the second current discriminating method comprises the steps of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current;

calculating a virtual arc energy by integrating an absolute value of an instantaneous value of the current converted into the digital value in a predetermined restricted period; and

deciding that an abnormal current is generated when a virtual arc energy value thus calculated exceeds a predetermined threshold, and further,

wherein the third current discriminating method comprises the steps of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a predetermined restricted period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold, and further

wherein the first to the third current discriminating methods are carried out in a manner that the data processing for the third method is started prior to the data processing for the first and the second methods with respect to the alternating current flowing to the AC load circuit, thereby concurrently carrying out the first to third methods.

20. An abnormal current detecting apparatus of an AC load circuit comprising:

a current-voltage converting circuit for sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value;

the amplification degree of circuit being set as the same value or a variable value,

a zero cross detecting circuit for detecting a zero cross point of an alternating voltage supplied to the AC load circuit; and

a data processing section for executing necessary data processing for carrying out at least one current discriminating method selected from first to third current discriminating methods,

wherein the first current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a predetermined restricted period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold, and

wherein the second current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current;

calculating a virtual arc energy by integrating an absolute value of an instantaneous value of the current converted into the digital value in a predetermined restricted period; and

deciding that an abnormal current is generated when a virtual arc energy value thus calculated exceeds a predetermined threshold, and further,

wherein the third current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle; and

deciding that an arc short circuit or another short-circuit current is generated immediately after a value converted into a digital value corresponding to an absolute value of an instantaneous current thus sampled exceeds a predetermined value continuously a predetermined number of times.

21. An abnormal current detecting apparatus of an AC load circuit comprising:

a current-voltage converting circuit for sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value;

the amplification degree of circuit being set as the same value or a variable value,

a zero cross detecting circuit for detecting a zero cross point of an alternating voltage supplied to the AC load circuit; and

a data processing section for executing necessary data processing for carrying out first to third current discriminating methods,

wherein the first current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

extracting a predetermined transition pattern specified by fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a predetermined restricted period; and

comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold, and

wherein the second current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to an instantaneous current;

calculating a virtual arc energy by integrating an absolute value of an instantaneous value of the current converted into the digital value in a predetermined restricted period; and

deciding that an abnormal current is generated when a virtual arc energy value thus calculated exceeds a predetermined threshold, and further,

wherein the third current discriminating method is carried out by following data processing of;

sampling an alternating current flowing to the AC load circuit in a predetermined cycle; and

deciding that an arc short circuit or another short-circuit current is generated immediately after a value converted into a digital value corresponding to an absolute value of an instantaneous current thus sampled exceeds a predetermined value continuously a predetermined number of times, and further

wherein the first to the third current discriminating methods are carried out in a manner that the data processing for the third current method is started prior to the data processing for the first and the second methods with respect to the alternating current flowing to the AC load circuit, thereby concurrently carrying out the first to third current method.