JP2008008859A - Method and device for detecting deterioration of wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for detecting the deterioration of a wire, capable of detecting semi-disconnection and disconnection occurring in an electric power source code. <P>SOLUTION: An instantaneous value of a cable way current is A/D-converted at a fixed interval of every 100 μs (S2) to be sampled, a difference with respect to the last sampling value is computed when an absolute value of the sampled current instantaneous value comes to 1A or less (S3), no current change section is judged to be determined (S4) when the found difference is 0.1 A or less, and the disconnection is determined to occur when the no-current-change sections are detected five times during 8.3 ms of period (S6). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric wire deterioration detection method and a detection device that detect the occurrence of a half-break or disconnection of an electric wire.

Conventionally, as a means for preventing the occurrence of an accident due to an abnormality in an electric circuit that supplies power to a load such as an electronic device, a circuit breaker for wiring that detects and cuts off when tracking is generated between both plug blades (for example, patent document) 1), and a circuit breaker (see, for example, Patent Document 2) that shuts down a circuit when a short-circuit accident occurs in the middle of an electric wire due to deterioration of the insulating film of the electric wire or melting of the film due to heating in the middle of the electric circuit. ing.
JP 2002-186168 A JP-A-10-14086

  Any of the above conventional circuit breakers that operate to shut down due to an abnormal electric circuit detects the discharge between the electrodes or the short circuit of the cord that occurs in the middle of the electric circuit, and operates in the middle of the power cord from the outlet to the load. When a half-break or break occurred in the electric wire, it could not be detected. However, most home appliances used in the home are connected to a commercial power supply via a power cord, and this power cord's half-breaking or disconnection phenomenon promotes the degradation of the power cord as well as the generation of tracking. Insulation breakdown may be caused, and eventually a short circuit accident and a fire accident may occur. Therefore, it is possible to prevent such an accident if the occurrence of the half disconnection or the disconnection can be detected.

  Therefore, in view of such a problem, an object of the present invention is to provide a wire deterioration detection method and a detection device that detect a half-break or break of a wire that occurs in a sheath of a power cord.

  In order to solve the above-mentioned problem, the wire deterioration detection method according to the invention described in claim 1 detects the current waveform of the wire by the current detection means, and at a predetermined constant interval of 1/50 or less of the voltage cycle. A sampling step for sampling an instantaneous value of the detected current, and a difference calculation step for calculating a difference from the previous sampling value stored in the storage means when the sampled current instantaneous value is equal to or less than a first predetermined value; And a non-change detecting step for determining that there is no current change when the obtained difference is equal to or smaller than a second predetermined value smaller than the first predetermined value, and occurred in a preset period within a voltage half cycle. The occurrence of disconnection is determined based on the number of unchanged sections.

  According to a second aspect of the present invention, there is provided an electric wire deterioration detection device that determines a disconnection of an electric circuit by calculation based on current detection means for detecting a current waveform of the electric wire, storage means for storing current waveform information, and current information. An arithmetic determination unit, the arithmetic determination unit, sampling means for sampling an instantaneous value of the current from the current waveform at a predetermined constant interval equal to or less than 1/50 of the current cycle, and the sampling value is a first predetermined value A non-change detecting means for detecting a non-change area that is less than or equal to a value and has a slight change in current; and a determination means that determines that a disconnection has occurred when the detection of the non-change area reaches a predetermined number of times in a substantially half voltage period. It is characterized by.

When power is being supplied to the load, if the power cord is half-broken or broken, the circuit current waveform will have a shape different from the power supply voltage, causing a phenomenon that almost no current flows near the voltage zero cross (see Fig. 2). I2 waveform shown in FIG. 2), and a large current flows (i1 waveform shown in FIG. 2) due to discharge occurring near the peak of the voltage waveform.
According to the first and second aspects of the present invention, a half-break or break is detected by detecting such a unique phenomenon, and a voltage zero cross is detected by detecting a current that is equal to or less than a predetermined value (first predetermined value). The vicinity of the point is detected, and the current unchanged section (i2 waveform shown in FIG. 2) is detected by observing the amount of change from the previous sampling value in that section. Then, by detecting the length based on the number of occurrences of the non-change section, it is possible to detect a peculiar phenomenon when a half-break or a break occurs in the electric wire. Therefore, it is possible to detect a half-break or a break.
Moreover, since it is possible to detect a half-break or a break simply by detecting the waveform of the current flowing through the wire, it is possible to detect the deterioration of the wire with a simple configuration.

According to a third aspect of the present invention, in the invention according to the second aspect, the non-change detecting means compares the sampled instantaneous current value with a predetermined value or less and the previous sampled value stored in the storage means, and the difference is It is characterized in that it is determined to be in the non-change region when it is equal to or less than a second predetermined value set between 0.05 and 0.2 amperes.
According to the present invention, it is possible to reliably detect the current unchanged section in the vicinity of the zero point.

According to a fourth aspect of the present invention, in the invention according to the second or third aspect, the determination means determines that a disconnection has occurred when the sampling value determined to be a non-change region is generated a predetermined number of times within a predetermined period within a voltage half cycle. It is characterized by.
According to the present invention, since the determination is made based on the length of the non-change period, it is possible to reliably detect a half-break or a break.

According to the present invention, when a no-current section is generated in the vicinity of the zero-cross point of the current flowing through the electric wire, it is detected, so that it is possible to detect a unique phenomenon when a half-break or a break occurs in the electric wire. Therefore, it is possible to detect a half-break or a break.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a wire deterioration detection device according to the present invention, and shows a block diagram of a plug device that cuts off a power cord from a power source when the power cord is disconnected using the wire deterioration detection device. In FIG. 1, 1 is a power cord, 2 is a power source (a power supply unit including an outlet connected to a plug), 3 is a blocking means, 4 is a load, 5 is a wire deterioration detection circuit, and 6 is a current of the power cord. A current transformer as a current detection means for detecting a waveform, 7 indicates a power supply line for supplying power to the wire deterioration detection circuit 5, and these devices and circuits are incorporated in a plug case having a plug blade. .

  The wire deterioration detection circuit 5 includes an I / V conversion circuit 10 that converts the waveform information of the circuit current detected by the current transformer 6 into a voltage signal, and an A / D conversion circuit 11 that converts the current information converted into a voltage into a digital signal. An operation determination circuit 12 that performs a predetermined calculation to determine disconnection (half disconnection and disconnection), a register 13 that is a storage unit that stores various information, a determination output circuit 14 that outputs a determination result, and a wire deterioration detection circuit A power supply circuit 15 for driving is provided. The determination output circuit 14 is configured to output a signal for causing the blocking means 3 to perform a blocking operation. Further, the A / D conversion circuit 11, the operation determination circuit 12, and the register 13 are composed of a microcomputer and are integrally formed.

  The deterioration detection operation of the wire deterioration detection circuit having the above configuration is as follows. However, the deterioration detection operation of the present invention is based on the following characteristics. FIG. 2 is an explanatory diagram of the power supply voltage and the circuit current waveform for explaining the theory of detecting the deterioration of the electric wire according to the present invention. When a half-break or a break occurs in the internal wire of the power cord 1, the section E2 in FIG. As shown in the current waveform diagram, a spark discharge is generated between the disconnected ends near the peak of the voltage waveform (waveform portion of about 70 V or more) at the disconnection point, and a relatively large current flows (i1 shown in FIG. 2). . On the other hand, in the vicinity of the zero cross point of the voltage waveform (waveform portion of about 70 V or less), a non-current section in which only a small current flows is generated (i2 shown in FIG. 2). Therefore, the circuit current waveform has a shape different from the power supply voltage waveform. In the present invention, this no-current section is detected to detect the occurrence of a half-break or break.

  FIG. 3 shows a flowchart for explaining the flow of operation of the electric wire deterioration detection circuit under microcomputer control, and the operation will be explained based on this figure. First, current information detected by the current transformer 6 is converted into voltage data and input to the microcomputer (S1). The input voltage data is input to the A / D conversion circuit 11, converted into digital data by the A / D conversion circuit 11, and taken into the arithmetic determination circuit 12 every 100 μs (S2). In the arithmetic determination circuit 12, first, a zero cross area determination process for detecting the vicinity of a voltage zero cross point where almost no current flows is performed (S3).

  The detection of the zero cross area is determined by the magnitude of the voltage value after A / D conversion, and in the range of 2.0 V to 3.0 V (center 2.5 V), the zero cross area is centered on the voltage zero cross point. It is determined that there is, and the process proceeds to the unchanged process step (S4). In the case of other voltages (voltage less than 2,0 V or more than 3.0 V), it is determined that the voltage is not in the zero cross area, and the operation determination circuit 12 takes in the next A / D conversion value. In this voltage value information, 2.5 V corresponds to 0 A, 2.0 V corresponds to −1.0 A, 3.0 V corresponds to +1.0 A, and the first predetermined value is 1.0 ampere.

  In the unchanged process, a comparison is made with the previous sampling value temporarily stored in the register 13, and the difference from the previous sampling voltage value is within a second predetermined value of 0.05V. If it is (within 0.1 A), it is determined that it is a non-change section, counts up (S5), and proceeds to the output processing step (S6).

In the output processing step, the timer started at count 1 is added until it counts 8.3 ms, and if it is counted 5 times before the time is up, that is, the difference from the previous sampling voltage value is within 0.05V. If the number of occurrences is five, it is determined that a disconnection has occurred, and the process proceeds to S7 where detection processing is performed. In this detection process, the determination output circuit 14 is output. If the counter does not reach 5, the process returns to the sampling step, the next A / D conversion value is taken in, and the above processing steps are repeated.
On the other hand, when there is a difference exceeding 0.05 V in the unchanged process, the next output processing step is similarly returned to the sampling step, and the next A / D conversion value is captured.

When the count number is less than 5, the A / D conversion value is taken in. However, in this re-processing, if it is determined that the process is unchanged again, the current sampling value and the previous sampling value are No change processing is performed again. Similarly, if it is within 0.05 V, it counts up and proceeds to output processing, and the number of times is added until it reaches 8.3 ms, but within 8.3 ms from the first count If the condition within 0.05V does not occur 5 times, the counter is cleared and restarts from N = 0.
Note that an upper limit (here, 8.3 ms) is always set in order to eliminate the case where the unchanged state continues continuously as in the case where the electric circuit is interrupted. The operation determination circuit 12 is a CPU of a microcomputer, and is also a sampling unit, a non-change detection unit, and a determination unit.

As described above, when a no-current section is generated in the vicinity of the voltage zero crossing point of the current flowing through the electric wire, it is detected, so that it is possible to detect a peculiar phenomenon when the electric wire is partially broken or broken. Therefore, it is possible to detect a half-break or a break.
Moreover, it is possible to detect a half-break or a break simply by detecting the current waveform flowing in the wire, and it is possible to detect the deterioration of the wire with a simple configuration.
And since no change in current is judged based on the difference from the previous sampling value, it is possible to reliably detect the no change section of current near the zero point, and because the judgment is based on the length of the no change period, it is a half-break. And disconnection can be detected reliably.

In the above embodiment, the state where the absolute value of the detected instantaneous current value is within 1 A is the vicinity of the zero cross point (zero cross area). The first predetermined value is preferably further reduced.
In addition, if the difference from the previous sampling value is within 0.1 A, it is determined that there is no change interval, but the second predetermined value that is this threshold is not fixed, and is 0.05 to Even if it is changed between 0.2A, it can be detected well.
Furthermore, the sampling interval of the instantaneous current value is set to 100 μs (in the case of 50 Hz, 200 samplings are performed in one voltage cycle), but the sampling interval is not changed even if it is performed at least about 50 times in one voltage cycle. Can be detected.

It is a block diagram which shows an example of embodiment of the electric wire deterioration detection apparatus which concerns on this invention. It is waveform explanatory drawing explaining the half-break detection method. 2 is a flowchart showing a flow of a half-break detection operation of the circuit of FIG.

Explanation of symbols

  1 .... Power cord 2 .... Power source 5 .... Wire deterioration detection circuit 6 .... Current transformer (current detection means) 10 .... I / V conversion circuit 11 .... A / D conversion circuit 12, ... .. Operation determination circuit, 13 .. Register, 14 .. Determination output circuit.

Claims (4)

A sampling step of detecting a current waveform of the electric wire by a current detection means and sampling an instantaneous value of the current detected at a predetermined constant interval of 1/50 or less of a voltage cycle;
A difference calculating step of calculating a difference from the previous sampling value stored in the storage means when the sampled current instantaneous value is equal to or less than the first predetermined value;
A non-change detecting step for determining that there is no current change when the obtained difference is equal to or smaller than a second predetermined value smaller than the first predetermined value;
An electric wire deterioration detection method, comprising: determining occurrence of disconnection based on the number of the unchanged sections generated in a preset period within a voltage half cycle. Current detection means for detecting the current waveform of the electric wire, storage means for storing the current waveform information, and an operation determination unit for determining disconnection of the electric circuit by calculation based on the current information,
The calculation determination unit includes a sampling unit that samples an instantaneous value of a current from a current waveform at a predetermined constant interval equal to or less than 1/50 of a current cycle;
A non-change detecting means for detecting a non-change region where the sampling value is equal to or less than a predetermined value and the change in current is slight;
An electric wire deterioration detection apparatus comprising: a determination unit configured to determine that a disconnection has occurred when detection of the non-change region reaches a predetermined number of times in a substantially voltage half cycle section. The non-change detecting means compares the sampled current instantaneous value with a predetermined value or less and the previous sampled value stored in the storage means, and sets the difference between 0.05 and 0.2 amperes. The wire deterioration detection device according to claim 2, wherein when it is equal to or less than a predetermined value of 2, it is determined to be in the unchanged region. The electric wire deterioration detection device according to claim 2 or 3, wherein the determination means determines that a disconnection has occurred when a sampling value determined to be a non-change region occurs a predetermined number of times within a predetermined period within a voltage half cycle.

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