JP2005140721A - Discharge sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a discharge phenomenon due to partial disconnection of a wire from a conductor in a commercial electric wire, and a tracking phenomenon or the like generated on a circuit between the wires or the like, by simple circuit constitution. <P>SOLUTION: A discharge current detecting means 10 is clamped onto the commercial electric wire (100V or 200V) by a CT clamp or the like, and detects a current flowing in the commercial electric wire. A discharge current component extracting means A extracts a discharge current component appeared in a ridge portion of a waveform in a commercial frequency (50Hz or 60Hz), and a determination means 80 determines the generation of the discharge phenomenon when detecting the discharge current component at a prescribed frequency or more within a fixed time. The discharge current component extracting means A also full-wave-rectifies an extracted alternating current and forms a filtered waveform wherein a commercial frequency component and a noise component are removed from a full-wave-rectified waveform, and the determination means 80 preferably observes a waveform having two times of frequency of the commercial frequency, based on the waveform. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge sensor that detects a discharge phenomenon caused by a partially broken strand of a commercial electric wire, a tracking phenomenon, or the like.

Conventionally, various methods for detecting a partial discharge generated in a power cable have been proposed.
For example, Patent Document 1 discloses a detection coil that generates an induced electrical signal by electromagnetic waves emitted from a power cable in association with partial discharge, and a specific frequency component that is connected to the detection coil and selectively passes a specific frequency component. A partial discharge detection sensor including a K filter is disclosed.

In a commercial electric wire, a tracking phenomenon or the like occurs on a circuit such as a partial disconnection of a stranded wire or a line between wires. The tracking phenomenon is a phenomenon in which an electric spark is generated along the surface of the insulating material, thereby generating carbide on the surface and generating an electrically conductive track. The tracking phenomenon occurs when dust adhering to the outlet absorbs moisture and lowers insulation properties, causing an electrical fire. The sensor disclosed in Patent Document 1 cannot detect these discharge phenomena and tracking phenomena.
JP-A-6-273472

  The present invention has been made to solve the above-described problems, and detects a discharge phenomenon caused by a tracking phenomenon or the like occurring on a circuit such as a partial disconnection of a wire from a conductor of a commercial electric wire or a line with a simple circuit configuration. It is an object of the present invention to provide a discharge sensor that can perform such a process.

  In order to achieve this object, the invention described in claim 1 includes a discharge current detecting means 10 that clamps a commercial wire and detects a current flowing through the commercial wire, as shown in the basic configuration diagram of FIG. Among the currents detected by the discharge current detection means 10, a discharge current component extraction means A that extracts a discharge current component that appears in the vicinity of the peak value of the commercial frequency component, and a discharge current extracted by the discharge current component extraction means A And determining means 80 for determining that a discharge phenomenon has occurred when a component is detected a predetermined number of times or more in a certain period of time.

  According to the first aspect of the present invention, the discharge current detecting means 10 clamps the commercial electric wire (100 V or 200 V) with a CT clamp or the like, and detects the current flowing through the commercial electric wire. The discharge current component extraction unit A extracts a discharge current component that appears in the peak portion of the waveform of the commercial frequency component (50 Hz or 60 Hz), and the determination unit 80 detects the discharge current component a predetermined number of times or more in a certain time. It is determined that a discharge phenomenon has occurred.

  According to a second aspect of the present invention, in the first aspect of the invention, the discharge current component extraction unit A includes a full-wave rectification unit 20 that performs full-wave rectification on the alternating current detected by the discharge current detection unit 10, and the total current rectification unit 20 Filtering means B that removes commercial frequency components and noise components from the waveform that has been full-wave rectified by the wave rectifying means 20, synchronous waveform generating means 50 that generates a synchronous waveform having a frequency twice that of the commercial frequency, and the synchronous waveform Waveform shaping means 70 for shaping the waveform filtered by the filtering means B in accordance with the synchronization waveform generated by the generation means 50, and the determination means 80 observes the waveform shaped by the waveform shaping means 70. When a waveform having a frequency twice as high as the commercial frequency is detected a predetermined number of times or more in a predetermined time, the determination means 80 determines that a discharge phenomenon has occurred. It is characterized by having a.

  According to the second aspect of the present invention, the full-wave rectifying means 20 constitutes a diode bridge circuit or the like, and full-wave rectifies the alternating current detected by the discharge current detecting means 10, and the filtering means B is full-wave rectified. The commercial frequency component and noise component are removed from the obtained waveform, and only the discharge current component is extracted. The synchronous waveform generating means 50 generates a synchronous waveform having a frequency twice as high as the commercial frequency, and the waveform shaping means 70 has a discharge current component at a predetermined level at the peak portion of the full-wave rectified commercial frequency component waveform. If it occurs, a synchronization waveform having a frequency twice the commercial frequency is output. If not, a synchronization waveform is not output. The determination unit 80 determines that a discharge phenomenon has occurred when a waveform having a double frequency is detected a predetermined number of times or more in a predetermined time by FFT or the like.

  According to a third aspect of the present invention, in the second aspect of the present invention, the filtering unit B removes the commercial frequency component and the low-frequency noise component from the full-wave rectified waveform by the full-wave rectifying unit 20. The high-frequency filter 30 and the waveform filtered by the high-pass filter 30 and the synchronous waveform having a frequency twice the commercial frequency generated by the synchronous waveform generating means 50 are ANDed to remove high-frequency noise components. And an AND circuit 60.

  According to the third aspect of the present invention, the high pass filter 30 removes the commercial frequency component and the low frequency noise component from the full-wave rectified waveform. The AND circuit 60 removes a high frequency noise component from the waveform filtered by the high pass filter 30.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the filtering means B further includes a comparator 40 for pulse-shaping the waveform filtered by the high-pass filter 30 with a predetermined threshold, and generating the synchronous waveform The synchronization waveform generated by the means 50 is pulse-shaped, and the waveform shaping means 70 is supplied from the AND circuit 60 within a period specified by the pulse-shaped synchronization waveform output from the synchronization waveform generation means 50. The first Hi signal to be output is latched and output to the determination means 80.

  According to the fourth aspect of the present invention, the comparator 40 pulses the waveform filtered by the high pass filter 30 with a predetermined threshold value. The synchronization waveform generation means 50 generates a pulsed synchronization waveform having a frequency twice the commercial frequency. The waveform shaping means 70 uses a flip-flop or the like, latches the first Hi signal output from the AND circuit 60 within a period specified by the pulse-like synchronization waveform, and outputs it to the determination means 80. That is, when pulse shaping representing the discharge current component exists, a pulse waveform having a frequency twice the commercial frequency is output.

  According to the first aspect of the present invention, by clamping to a commercial electric wire, detecting the current flowing through the commercial electric wire, extracting and observing the discharge current component that appears near the peak value of the commercial frequency component, It is possible to detect with high sensitivity, for example, partial wire breakage, discharge between wires due to the influence of dust, tracking phenomenon occurring on the wire surface, and the like.

  According to the second aspect of the present invention, in addition to the effect of the first aspect of the invention, the detected alternating current is subjected to full-wave rectification, and the commercial frequency component and the noise component are removed from the full-wave rectified waveform. Since a waveform having a frequency twice as high as the commercial frequency is observed from a waveform formed based on the obtained waveform, the presence or absence of discharge can be determined more efficiently than when full-wave rectification is not performed.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, by removing the commercial frequency component and the noise component from the full-wave rectified waveform by the high-pass filter and the AND circuit, the number of parts is reduced. Therefore, a simple circuit configuration can be obtained.

  According to the invention described in claim 4, in addition to the effect of the invention described in claim 3, it is possible to determine the presence or absence of discharge at high speed with high sensitivity by observing and determining with the pulse waveform.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. FIG. 2 is a circuit diagram showing a configuration of the discharge sensor in the embodiment of the present invention. The discharge sensor includes a discharge current detection unit 10, a full-wave rectification circuit 20, an HPF (high pass filter) 30, a comparator 40, a comparator 50, an AND (logical product) circuit 60, a flip-flop 70, a frequency detection circuit 80, and a control. Part 90 is provided.

  The discharge current detection unit 10 includes a CT clamp (transformer), a capacitor, a minute resistance, and the like. The discharge current detection part 10 clamps to both electric wires of AC100V or AC200V commercial electric wire used as a commercial power source, and detects the electric current which flows through both electric wires. A load current, a noise current, and a discharge current generated due to a part of the conductor wire being broken, a wire surface deterioration, a tracking phenomenon, or the like flow through the electric wire. In order to detect the discharge current, the discharge current detection unit 10 clamps upstream from the discharge occurrence location. The discharge current detection unit 10 outputs the detected current to the full-wave rectifier circuit 20.

  The full-wave rectification circuit 20 performs full-wave rectification on the alternating current input from the discharge current detection unit 10. The full-wave rectifier circuit 20 may be configured using a diode bridge circuit or a transformer with a neutral point. After full-wave rectification, the voltage extracted by the detection resistor or the like is output to the HPF 30 and the comparator 50.

  The HPF 30 is a filter that passes a signal having a frequency equal to or higher than a predetermined cutoff frequency and attenuates a frequency component equal to or lower than the cutoff frequency. In the present invention, the noise of the commercial frequency component (50 Hz or 60 Hz) and the low frequency component is reduced. It shuts off and passes the noise of the discharge current component and high frequency component. The signal from which the commercial frequency component is blocked is output to the comparator 40.

  The comparator 40 compares the input signal from the HPF 30 with a predetermined reference voltage, and pulses the input signal. It is preferable to use an operational amplifier. That is, when the input signal exceeds the predetermined reference voltage, Hi is output, and when the input signal is equal to or lower than the predetermined reference value, Lo is output, thereby converting the analog component to the digital component. The pulse-shaped signal is output to the AND circuit 60.

  The comparator 50 generates a reference pulse signal based on the input signal from the full wave rectifier circuit 20. It is preferable to use an operational amplifier. That is, when the input signal exceeds a predetermined reference voltage, Hi is output, and when the input signal is equal to or lower than the predetermined reference value, Lo is output, thereby converting the analog component to the digital component. The predetermined reference voltage is set to a level for generating a synchronization pulse signal having a frequency twice the commercial frequency. The generated synchronization pulse signal is output to the AND circuit 60 and the flip-flop circuit 70. The predetermined reference voltage is not limited to the method of generating from the output of the full-wave rectifier circuit 20, and may be generated by acquiring a commercial frequency component from the outside.

  The AND circuit 60 performs an AND operation on the input signal from the comparator 40 and the synchronization pulse signal input from the comparator 50. That is, Hi is output when both input signals are Hi, and Lo is output when both or one of the input signals is Lo. The discharge current is generated at the peak portion of the waveform of the commercial frequency component. Therefore, when the logical product of the input signal from the comparator 40 and the synchronization pulse signal generated based on the commercial frequency component is taken, noise other than the peak portion of the waveform is removed, and only the discharge current component is extracted. The The signal from which the noise has been removed is output to the flip-flop 70.

  The flip-flop 70 is an RS flip-flop, and an input signal from the AND circuit 60 is input to the set terminal, and an inverted signal of the reference pulse signal input from the comparator 50 is input to the reset terminal. The output signal of the flip-flop 70 is input to the frequency detector 80.

  The frequency detector 80 applies FFT (Fast Fourier Transform) to the signal input from the flip-flop 70 using an FFT analyzer or the like. An FFT analyzer or the like uses the time for performing the FFT as a measurement time, counts this measurement time for a certain time, and determines the presence or absence of the frequency component of the discharge current in the input signal from the flip-flop 70. For example, if the measurement time is 10 seconds and this is repeated 6 times, the fixed time is 1 minute. If a frequency twice the commercial frequency is measured 5 times per minute, it is determined that a discharge phenomenon has occurred. In addition, the said measurement time and fixed time are examples, and are not limited to this.

  When the control unit 90 determines that a discharge phenomenon has occurred in the detected electric wire as a result of frequency analysis by the frequency detection unit 80, the control unit 90 displays a warning on a display unit (not shown) or warns from a voice synthesis unit (not shown). Send a buzzer to alert the manager of the detected wire. Further, it may be possible to instruct safety of the detected electric wire by instructing to shut off the detected electric wire, stop power supply to the detected electric wire, or the like.

  The operation of the discharge sensor in the embodiment of the present invention will be described. FIG. 3 is a voltage waveform transition diagram in each element of the discharge sensor according to the embodiment of the present invention. First, a detection current is acquired from a commercial electric wire of AC100V or AC200V via the discharge current detection unit 10. This current is full-wave rectified by the full-wave rectifier circuit 20. The output voltage waveform of the full-wave rectifier circuit 20 is as shown in A of FIG. This waveform includes full-wave rectified commercial frequency components, noise components, and discharge current components.

  The output voltage of the full-wave rectifier circuit 20 passes through the HPF 30, and noises of commercial frequency components and low frequency components are removed. The voltage from which these components are removed passes through the comparator 40 and is pulse-shaped. The output current waveform of the comparator 40 is a waveform as shown in FIG. This waveform includes a digitized discharge current component and a noise component that has not been removed by the HPF 30.

  Further, the output voltage of the full-wave rectifier circuit 20 passes through the comparator 50 and is pulse-shaped into a synchronous pulse signal (a frequency twice the commercial frequency). The output current waveform of the comparator 50 is as shown in FIG. This waveform is a pulse signal having a frequency (100 or 200 Hz) twice the commercial frequency.

  The output voltage of the comparator 40 and the output voltage of the comparator 50 are input to the AND circuit 60 and ANDed. Since the output voltage of the AND circuit 60 is Lo during the pulse OFF period of the frequency twice the commercial frequency that is the output voltage of the comparator 50, the noise component shown in B is removed. The output voltage of the AND circuit 60 has a waveform as indicated by D in FIG. This waveform includes only the discharge current component.

  The output voltage of the AND circuit 60 is input to the set terminal of the flip-flop circuit 70. The output voltage of the comparator 50 is inverted and input to the reset terminal of the flip-flop circuit 70. The output voltage waveform of the flip-flop circuit 70 is as shown in E of FIG.

  The operation of the flip-flop circuit 70 will be described. When Hi is input from the AND circuit 60 to the set terminal for the first time, the waveform of the comparator 50 is inverted and Lo is input to the reset terminal. Becomes Hi. Next, when Lo is input from the AND circuit 60 to the set terminal, since Lo is input to the reset terminal without change, the flip-flop circuit 70 performs a latch operation, and the output remains Hi. As described above, while the reset terminal is Lo, regardless of whether the set terminal is Hi or Lo, the output becomes Hi by the set operation or the latch operation. Next, when the waveform of the comparator 50 is inverted and Hi is input to the reset terminal, the flip-flop circuit 70 is reset and the output becomes Lo.

  When the discharge current component is not detected, the output of the AND circuit 60 becomes a continuous waveform of Lo, so that Hi cannot be set in the flip-flop circuit 70 and has a frequency twice the commercial frequency as shown by E. No pulse waveform is generated.

  The frequency detection unit 80 determines that a discharge phenomenon has occurred when a pulse waveform having a frequency twice the commercial frequency is continuously detected within a predetermined time from the output waveform from the flip-flop circuit 70.

  When the frequency detection unit 80 determines that a discharge phenomenon has occurred in the detected electric wire, the control unit 90 displays a warning on a display unit (not shown) or sends a warning buzzer from a voice synthesis unit (not shown). To alert the manager of the detected wire.

  The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention.

  For example, the degree of the discharge phenomenon can also be determined by making the measurement time in the frequency detection circuit 80 and making the threshold value of the comparator 40 variable. Further, instead of making the threshold value of the comparator 40 variable, the detection resistor for converting the discharge current into voltage may be made variable.

It is a basic lineblock diagram of a discharge sensor in an embodiment of the present invention. It is a circuit diagram which shows the structure of the discharge sensor in embodiment of this invention. It is a waveform transition diagram in each element of the discharge sensor in the embodiment of the present invention.

Explanation of symbols

A discharge current component extraction means B filtering means 10 discharge current detection means (discharge current detection unit)
20 Full-wave rectification means (full-wave rectification circuit)
30 HPF
40 Comparator 50 Synchronous waveform generation means (Comparator)
60 AND circuit 70 Waveform shaping means (flip-flop)
80 Determination means (frequency detection circuit)
90 Control unit

Claims (4)

A discharge current detecting means for clamping the commercial wire and detecting a current flowing through the commercial wire;
Among the currents detected by the discharge current detection means, a discharge current component extraction means for extracting a discharge current component that appears near the peak value of the commercial frequency component;
A determination unit that determines that a discharge phenomenon has occurred when the discharge current component extracted by the discharge current component extraction unit is detected a predetermined number of times or more in a predetermined time;
A discharge sensor comprising: The discharge current component extraction means includes
Full wave rectification means for full wave rectification of the alternating current detected by the discharge current detection means;
Filtering means for removing a commercial frequency component and a noise component from a waveform that has been full-wave rectified by the full-wave rectifying means;
Synchronization waveform generating means for generating a synchronization waveform having a frequency twice the commercial frequency;
Waveform shaping means for shaping the waveform filtered by the filtering means in accordance with the synchronization waveform generated by the synchronization waveform generating means,
The determination means observes the waveform formed by the waveform shaping means, and determines a discharge phenomenon occurrence when detecting a waveform having a frequency twice the commercial frequency at a predetermined number of times in a predetermined time;
The discharge sensor according to claim 1, further comprising: The filtering means includes
A high-pass filter that removes the commercial frequency component and the low-frequency noise component from the waveform that has been full-wave rectified by the full-wave rectifier;
An AND circuit that takes a logical product of the waveform filtered by the high-pass filter and a synchronous waveform having a frequency twice the commercial frequency generated by the synchronous waveform generating means, and removes a high-frequency noise component;
The discharge sensor according to claim 2, comprising: The filtering means includes
A comparator for pulse-shaping the waveform filtered by the high-pass filter at a predetermined threshold;
Further including
The synchronization waveform generated by the synchronization waveform generation means is
Pulsed,
The waveform shaping means includes
The first Hi signal output from the AND circuit is latched and output to the determination means within a period specified by the pulse-shaped synchronization waveform output from the synchronization waveform generation means. 3. The discharge sensor according to 3.

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