JP2007047181A - Leak current detection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect leak current caused by ground insulation resistance. <P>SOLUTION: This leak current detection device comprises: a leak current detection section 10 for detecting leak current from a measured line; an amplifying section 11 for converting the detected leak current into voltage and amplifying converted voltage; a first harmonic component removing section 12 for removing a harmonic component included in the voltage amplified by the amplifying section, a voltage detection section 14 for detecting voltage from the measured line; a second harmonic component removing section 16 for removing a harmonic component included in the detected voltage; a phase difference detection section 20 for detecting phase difference from two voltage signal waveforms from which harmonic component is removed; a frequency calculation section 21 for calculating frequency occurring in the measured line of which voltage is detected by the voltage detection section based on the voltage signal waveforms from which harmonic component is removed by the second harmonic component removing section; and a phase angle calculating means 22 for calculating phase angle of the leak current based on the phase difference detected by the phase difference detection section and frequency calculated by the frequency calculation section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a leakage current detection apparatus and method for determining an insulation state of an electrical device by measuring a leakage current, and more specifically, detects a leakage current of only a ground insulation resistance component flowing in a measured electric line. The present invention relates to a leakage current detection apparatus and method.

  In everyday life, there is not much awareness of the existence of electricity, but as is well known, it is used as an energy source and in various fields such as information and communication. It has become a must not.

  On the other hand, the use of electricity is convenient, but if it is not properly managed and used, it also has very dangerous aspects, and there are many possibilities of causing serious accidents such as electric fires and electric shocks.

  For example, one of the causes of the serious accident is leakage current that is closely related to insulation failure of electric circuits and equipment. However, in order to investigate this leakage current, it takes a long time, and it is necessary to measure the value of insulation failure with an insulation resistance meter after a power failure.

  However, in the current social situation, computers are used in various areas of society, and systems that operate continuously for 24 hours have been constructed by the spread of intelligent buildings and factory automation (FA). In order to measure, it is in a situation where it cannot temporarily be in a power failure state.

  Therefore, at present, due to the demand for uninterruptible socialization due to such advanced information technology, the leakage current measurement method that can measure the insulation failure of the electric circuit and equipment from the method using the insulation resistance meter with power failure without turning off the electricity Various preventive measures during energization in which the leakage current is measured by an earth leakage breaker, an earth leakage fire alarm, or the like and the insulation state is managed have been proposed (see, for example, Patent Documents 1 and 2).

  By the way, the leakage current I includes a leakage current (Igc) caused by the ground capacitance and a leakage current (Igr) caused by the ground insulation resistance directly related to the insulation resistance. The cause of the above-mentioned leakage fire is the presence of insulation resistance. If only the leakage current (Igr) caused by this insulation resistance can be accurately detected, the insulation state of the circuit can be checked, A catastrophe such as a fire can be avoided.

  However, electrical equipment used in factories or the like may have a long wire path when connecting the devices, and this increase in the length of the wire path increases the capacitance to the ground. As a result, the leakage current (Igc) due to the ground capacitance increases.

  Moreover, these electric devices are equipped with inverters using power semiconductor elements. In electrical equipment, this installed inverter is used as a high-speed electronic switch, so inevitably harmonic distortion current is generated that is a sine wave that is an integral multiple of 50 Hz or 60 Hz, which is the fundamental frequency of commercial power. To do. Since the harmonic distortion current contains high frequency components, it passes through the ground capacitance that is naturally distributed in the electric wire and flows into the electric wire, and due to the harmonic distortion current that flows in the electric wire. The value of the leakage current I becomes large.

  Therefore, the leakage current (Igr) caused by the ground insulation resistance directly related to the quality of the insulation is affected by the length of the electric wire and the harmonic distortion current due to the inverter, and it is difficult to detect accurately. .

In addition, in equipment in which parts are mounted with high density, such as telephones, facsimiles, printers, and multi-function machines, when measuring with an insulation resistance meter or the like in order to check the insulation location, an electronic circuit is generated by the injected measurement voltage. May be affected. Accordingly, there is a large number of devices that cannot measure the insulation resistance because such devices may cause functional destruction.
JP 2001-215247 A JP 2002-98729 A

  The problem to be solved by the present invention is that the leakage current is measured, and the function of the equipment connected to the line to be measured is destroyed without causing the electric circuit and mechanical equipment to be in a power failure state for detection. Therefore, only the leakage current (Igr) caused by the ground insulation resistance directly related to the quality of the insulation is measured and detected easily and safely from the outside.

Moreover, in order to solve the above-mentioned problem, the leakage current detection apparatus according to the present invention includes a leakage current detection means for detecting a leakage current flowing in a measured electric wire having a single phase electric method, and the leakage current detection described above. Voltage conversion means for converting the leakage current detected by the means into voltage, voltage detection means for detecting the voltage applied to the electric wire to be measured, signal waveform of the voltage detected by the voltage detection means, A phase difference detecting means for detecting a phase difference from the voltage signal waveform from the voltage converting means; and a power supply frequency applied to the measured electric line based on the voltage signal waveform detected by the voltage detecting means. Based on the phase difference detected by the phase difference detection means and the power supply frequency calculated by the frequency calculation means, the leakage current flowing in the measured electric line is calculated. A phase angle calculating means for calculating a phase angle, an effective value calculating means for calculating an effective value of the leakage current detected by the leakage current detecting means, an effective value calculated by the effective value calculating means, and the phase angle Based on the phase angle of the leakage current flowing through the measured electric wire calculated by the calculating means, the leakage current component due to the ground insulation resistance included in the leakage current flowing through the measured electric wire is calculated. A ground insulation resistance leakage current component calculating means, wherein the effective value calculating means sets the average value of the leakage current detected by the leakage current detecting means to I, and sets the effective value I ₀ to I ₀ = I × (Π / 2) √2
The ground insulation resistance leakage current component calculation means calculates the effective value I ₀ calculated by the effective value calculation means and the leakage current flowing through the measured electric wire calculated by the phase angle calculation means. Of the leakage current component Igr caused by the ground insulation resistance included in the leakage current flowing in the measured electric wire path from the phase angle θ of Igr = I ₀ × cos θ
It is characterized by calculating by.

Furthermore, in order to solve the above-mentioned problem, the leakage current detection method according to the present invention includes a leakage current detection step for detecting a leakage current flowing in a measured electric line whose electric system is a single phase, and the leakage current detection described above. A voltage conversion step for converting the leakage current detected in the step into a voltage; a voltage detection step for detecting a voltage applied to the measured electric line; and a signal waveform of the voltage detected by the voltage detection step; A phase difference detection step for detecting a phase difference from the voltage signal waveform from the voltage conversion step, and a power supply frequency applied to the measured line based on the voltage signal waveform detected by the voltage detection step The leakage current flowing in the line to be measured based on the phase calculation detected in the phase difference detection step and the power supply frequency calculated in the frequency calculation step A phase angle calculating step for calculating a phase angle, an effective value calculating step for calculating an effective value of the leakage current detected by the leakage current detecting step, an effective value calculated by the effective value calculating step, and the phase angle Based on the phase angle of the leakage current flowing through the measured electric wire calculated in the calculation step, the leakage current component due to the ground insulation resistance included in the leakage current flowing through the measured electric wire is calculated. A ground insulation resistance leakage current component calculation step, wherein the effective value calculation step is defined as an average value of leakage currents detected by the leakage current detection step, and the effective value I ₀ is defined as I ₀ = I × (Π / 2) √2
The ground insulation resistance leakage current component calculation step calculates the effective value I ₀ calculated by the effective value calculation step and the leakage current flowing through the measured electric wire calculated by the phase angle calculation step. Of the leakage current component Igr caused by the ground insulation resistance included in the leakage current flowing in the measured electric wire path from the phase angle θ of Igr = I ₀ × cos θ
It is characterized by calculating by.

  The leakage current detection apparatus and method according to the present invention detects leakage current flowing through a measured electrical line, removes harmonic components from the detected leakage current, and occurs in the voltage line of the measured electrical line. The phase angle of the leakage current is detected from the detected phase difference and the power supply frequency calculated from the voltage from which the harmonic component has been removed. And the leakage current caused only by the ground insulation resistance is calculated from the calculated phase angle of the leakage current and the effective value of the leakage current from which the harmonic component is removed. Therefore, the leakage current detection apparatus and method according to the present invention accurately calculate the power frequency (50 Hz or 60 Hz for commercial power) flowing from the voltage from which the harmonic component has been removed to the line to be measured. Based on the frequency, the phase difference between the input signal waveform of the leakage current from which the harmonic component has been removed and the voltage signal waveform from which the harmonic component has been removed is accurately detected. Since the angle can be calculated, and the leakage current due to the ground insulation resistance alone can be calculated from the accurate phase angle and the effective value of the leakage current from which the harmonic component has been removed, Even if it is lengthened and affected by the harmonic distortion current caused by the inverter, only the leakage current due to the ground insulation resistance that causes a catastrophe such as a leakage fire can be calculated.

  In addition, the leakage current detection apparatus and method according to the present invention can measure Igr easily and safely from the outside without causing the electric circuit / mechanical equipment to temporarily stop for measuring and detecting the leakage current. it can.

  Hereinafter, a leakage current detection apparatus and method according to embodiments of the present invention will be described.

  As shown in FIG. 1, the leakage current detection device 1 is clamped to the entire measured electric wire A and detects a leakage current I flowing in the measured electric wire A (hereinafter referred to as a CT sensor unit). 10), the leakage current I detected by the CT sensor unit 10 is converted into a voltage, and the converted voltage (hereinafter referred to as “converted voltage”) V1 is amplified; A low-pass filter (hereinafter referred to as LPF) 12 that removes harmonic components from the voltage V1, a full-wave rectifier 13 that rectifies the converted voltage V1 from which the harmonic components have been removed by the LPF 12, and the voltage of the measured electrical line A The voltage detector 14 for detecting the voltage V2 from the line, the transformer 15 for transforming the voltage V2 detected by the voltage detector 14 to a predetermined transformation ratio, and the transformer 15 being transformed to a predetermined voltage value. Voltage V2 A low-pass filter (hereinafter referred to as LPF) 16 that removes harmonic components, a full-wave rectifier 17 that rectifies the voltage V2 from which the harmonic components have been removed by the LPF 16, and a post-conversion from which harmonic components have been removed by the LPF 12 The comparison unit 18 that compares the signal waveform S1 of the voltage V1 with the signal waveform S2 of the voltage V2 from which the harmonic component has been removed by the LPF 16, and the calculation unit 19 that performs a predetermined calculation based on the comparison result by the comparison unit 18 And a phase pulse width measuring unit 20 that measures the phase pulse width based on the calculation result by the calculating unit 19 and a voltage V2 signal from which the harmonic component has been removed by the LPF 16 The power source frequency measuring unit 21 that measures the power source frequency that is present, the phase pulse measured by the phase pulse width measuring unit 20, and the power source measured by the power source frequency measuring unit 21 A phase angle calculation unit 22 that calculates the phase angle of the leakage current I flowing through the measured electric wire A from the wave number, and an A / D conversion unit 23 that converts the converted voltage V1 rectified by the full wave rectification unit 13 into a digital signal. An effective value calculator 24 for calculating an effective value of the converted voltage V1 converted into a digital signal by the A / D converter 23, and an A for converting the voltage V2 rectified by the full-wave rectifier 17 into a digital signal. / D conversion unit 25, effective value calculation unit 26 for calculating the effective value of voltage V2 converted into a digital signal by A / D conversion unit 25, and phase angle of leakage current I calculated by phase angle calculation unit 22 The leakage current I calculated from the effective value of the converted voltage V 1 calculated by the effective value calculation unit 24 and the leakage current I calculated by the phase angle calculation unit 22. Phase angle and effective value calculation unit 2 And a resistance value calculation unit 28 for calculating the resistance value of the ground insulation resistance from the effective value of the voltage V2 calculated in Step 6.

  The CT sensor unit 10 detects magnetism generated from a leakage current component flowing in the electric wire path A to be measured, and generates a current from the detected magnetism. The CT sensor unit 10 supplies the generated current as the leakage current I to the amplification unit 11. In addition, the leakage current I generated by the CT sensor unit 10 is a leakage current (hereinafter referred to as Igc) due to the ground capacitance and a leakage current (hereinafter referred to as Igc) directly related to the insulation resistance. Igr.). In addition, Igc not only increases in capacity according to the length of the line A to be measured, but also increases in capacity due to harmonic distortion current caused by an inverter, a noise filter, or the like used in an electrical device.

  The amplifying unit 11 converts the leakage current I supplied from the CT sensor unit 10 into a voltage, and amplifies the converted voltage V1 to a predetermined level. For example, when the leakage current I supplied from the CT sensor unit 10 is 0 mA to 10 mA, the amplification unit 11 amplifies in two stages, and the leakage current I supplied from the CT sensor unit 10 is 10 mA to 300 mA. In this case, it is amplified in one stage. The amplifying unit 11 supplies the converted voltage V1 after amplification to the LPF 12. The LPF 12 removes harmonic components contained in the converted voltage V1. The LPF 12 supplies the converted voltage V1 from which the harmonic component has been removed to the full-wave rectification unit 13 and the comparison unit 18. The full-wave rectification unit 13 rectifies the supplied converted voltage V <b> 1 and supplies the converted voltage V <b> 1 after rectification to the A / D conversion unit 23.

  The voltage detection unit 14 detects a voltage generated in the voltage line by connecting a voltage probe to the measured electric line A. The voltage detector 14 detects the voltage between the R phase and the T phase other than the S phase (ground) when the electrical system of the measured electrical line A is a three-phase three-wire system (consisting of a delta connection). . Moreover, the voltage detection part 14 detects a voltage from between phases other than a grounding wire, when the electrical system of the to-be-measured electric wire A is a three-phase four-wire system (it consists of star connection). Moreover, the voltage detection part 14 detects the voltage between N phase and L phase, when the electrical system of the to-be-measured electrical line A is a single phase 2 wire type.

  Then, the voltage detection unit 14 obtains a reference point from the voltage V <b> 2 detected from the measured electric line A, and supplies the voltage V <b> 2 to the transformer 15. For example, the voltage detection unit 14 uses a point where the voltage V2 detected from the measured electric wire A crosses zero as a reference point.

  The transformer 15 transforms the supplied voltage V2 to a predetermined voltage value, and supplies the transformed voltage V to the LPF 16. For example, the transformer 15 performs voltage transformation so that the voltage ratio is 20: 1. The LPF 16 removes harmonic components contained in the supplied voltage V2. The LPF 16 supplies the voltage V <b> 2 from which the harmonic component has been removed to the full wave rectification unit 17, the comparison unit 18, and the power frequency measurement unit 21. The full-wave rectifier 17 rectifies the supplied voltage V <b> 2 and supplies the rectified voltage V <b> 2 to the A / D converter 25.

  The comparison unit 18 takes a 0V cross point of the converted voltage V1 supplied from the LPF 12, performs square wave conversion, and supplies the square wave converted signal to the arithmetic unit 19. Further, the comparison unit 18 takes the 0V cross point of the voltage V <b> 2 supplied from the LPF 16, performs square wave conversion, and supplies the square wave converted signal to the calculation unit 19.

  The calculation unit 19 performs a predetermined calculation based on the signal supplied from the comparison unit 18 and supplies the calculated signal to the phase pulse width measurement unit 20. The arithmetic unit 19 is composed of, for example, an EXOR (exclusive OR) circuit, and executes EXOR of the two signals after square wave conversion supplied from the comparison unit 18.

  The phase pulse width measurement unit 20 detects the phase pulse widths of the converted voltage V1 and voltage V2 based on the calculation result supplied from the calculation unit 19. Here, the operation of the phase pulse width measurement unit 20 will be described.

  When the electrical system is a single phase, as shown in FIG. 2A, the phase angle θ of Igr is 0 ° and the phase angle θ of Igc is 90 °. Therefore, the phase difference between Igr and Igc is 90 ° (1/4 cycle). When the power source is three-phase, the phase angle θ of Igr is 60 ° and the phase angle θ of Igc is 0 ° as shown in FIG. Therefore, the phase difference between Igr and Igc is 60 ° (1/6 cycle). Therefore, the phase pulse width measuring unit 20 targets only a phase pulse width of ¼ or less of one cycle so that it can cope with a single-phase power supply or a three-phase power supply.

  Therefore, the phase pulse width measurement unit 20 outputs to the phase angle calculation unit 22 a phase pulse width that is calculated based on the calculation result supplied from the calculation unit 19 and is ¼ or less of one cycle. When the power supply frequency is 60 Hz, one cycle is 16.6 ms, so the phase pulse width is 4.15 ms or less. When the power supply frequency is 50 Hz, one cycle is 20 ms. 4 ms or less.

  The power supply frequency measurement unit 21 measures the power supply frequency based on the voltage V <b> 2 supplied from the LPF 16 and supplies the measurement result to the phase angle calculation unit 22. In addition, if the to-be-measured electrical line A is a commercial power source, the measurement result of the power frequency measuring unit 21 is 50 Hz or 60 Hz. The power supply frequency measuring unit 21 may be configured to determine either 50 Hz or 60 Hz based on the voltage V2 supplied from the LPF 16.

Based on the phase pulse width W supplied from the phase pulse width measurement unit 20 and the power supply frequency F supplied from the power supply frequency measurement unit 21, the phase angle calculation unit 22 is connected to the measured electrical line A according to the following equation (1). The phase angle θ of the flowing leakage current I is calculated.
θ = 360 × A × F (1)
The phase angle calculation unit 22 supplies the calculated phase angle θ to the leakage current calculation unit 27.

The A / D converter 23 converts the rectified converted voltage V <b> 1 supplied from the full-wave rectifier 13 into a digital signal, and supplies the converted signal to the effective value calculator 24. Based on the signal supplied from the A / D conversion unit 23, the effective value calculation unit 24 calculates the effective value I ₀ of the converted voltage V1 by the following equation (2). The signal supplied to the effective value calculating unit 24, since it is based on the converted voltage V1 obtained by converting the leakage current I flowing through the measured electric line A to the voltage, and convenience I _0.
I ₀ = I × (π / 2) / √2 (2)

The effective value calculation unit 24 supplies the calculated effective value I ₀ to the leakage current calculation unit 27.

The A / D converter 25 converts the rectified voltage V <b> 2 supplied from the full-wave rectifier 17 into a digital signal and supplies the converted signal to the effective value calculator 26. The effective value calculation unit 26 calculates the effective value V ₀ of the voltage V2 based on the signal supplied from the A / D conversion unit 25 by the following equation (3).
V ₀ = V × (π / 2) / √2 (3)

The effective value calculation unit 26 supplies the calculated effective value V ₀ to the resistance value calculation unit 28.

The leakage current calculation unit 27 calculates Igr based on the phase angle θ supplied from the phase angle calculation unit 22 and I ₀ supplied from the effective value calculation unit 24. When the power source is a single-phase power source, Igr is calculated by the following equation (4), and when the power source is a three-phase power source, Igr is calculated by the following equation (5).
Igr = I ₀ × cos θ (4)
Igr = (I ₀ × sin θ) / cos 30 ° (5)
The leakage current calculation unit 27 determines whether the power source is a single-phase power source or a three-phase power source according to a selection state of a rotary switch (not shown).

  The leakage current calculation unit 27 supplies the calculated Igr to the resistance value calculation unit 28.

The resistance value calculation unit 28 calculates Gr by the following equation (6) based on the effective value V ₀ supplied from the effective value calculation unit 26 and Igr supplied from the leakage current calculation unit 27.
Gr = V ₀ / Igr (6)
In the leakage current detection apparatus 1 according to the present invention configured as described above, for example, when the power source of the measured electrical line A is a three-phase type, the power source can be processed in the same manner as a single-phase type. Yes. Here, the principle of the leakage current detection apparatus 1 according to the present invention will be described.

  The CT sensor unit 10 clamps the electric wire A to be measured, and, as shown in FIG. 3A, the waveforms between the R phase and the S phase, between the S phase and the T phase, and between the T phase and the R phase, which are different by 120 °. Is detected. In FIG. 3A, each waveform is shown for convenience, but the waveform detected by the CT sensor unit 10 is a composite waveform. The combined waveform detected by the CT sensor unit 10 is input to the calculation unit 19 via the amplification unit 11, the LPF 12, and the comparison unit 18.

  Moreover, the voltage detection part 14 connects a voltage probe to R phase and T phase, detects the voltage between R phase and T phase, and reverses the detected voltage, as shown in FIG.3 (b). The voltage detector 14 determines a point at which zero crossing occurs at a predetermined location of the detected voltage as a reference point. The voltage V <b> 2 whose reference point is determined in this way is input to the calculation unit 19 via the transformer 15, the LPF 16 and the comparison unit 18.

  For example, when only Igr (hereinafter referred to as “R phase Igr”) is generated in the R phase of the measured electrical line A, and only Igr (hereinafter referred to as “T phase Igr”) is generated in the T phase. As shown in FIG. 3C, the R phase Igr has a phase difference of 120 ° from the reference point, and the T phase Igr has a phase difference of 60 ° from the reference point.

  Further, when only Igc (hereinafter referred to as “R phase Igc”) is generated in the R phase of the measured electrical line A, and only Igc (hereinafter referred to as “T phase Igc”) is generated in the T phase. As shown in FIG. 3D, the phase difference from the reference point of the combined waveform of the R phase Igc and the T phase Igc is 180 ° (0 °).

  Further, when Igr and Igc are generated in the R phase of the measured electrical line A and Igr and Igc are generated in the T phase, the result is as shown in FIG.

  Further, the above description can be expressed as a vector as follows. Since the wire A to be measured is a three-phase type, it is as shown in FIG. Then, when the voltage detector 14 detects the voltage between the R phase and the T phase and obtains the reference point from the detected voltage, a single-phase vector diagram is obtained as shown in FIG. As described above, the phase difference between the R phase Igr and the reference point is 60 °, and the phase difference between the T phase Igr and the reference point is 120 °.

  Further, in the case of the single-phase type, as described above with reference to FIG. 2A, the phase difference between Igr and Igc is 90 °, so the R-phase Igc is obtained at a position rotated 90 ° from the R-phase Igr. In addition, the T-phase Igc can be obtained at a position rotated 90 ° from the T-phase Igr. Further, a combined vector Igc of the R phase Igc and the T phase Igc can be obtained at a position 180 ° (0 °) from the reference point (FIG. 4C).

Therefore, for example, when only the R phase Igr is generated in the measured electrical line A, the combined vector of the R phase Igr and Igc, that is, the leakage current I ₀ flowing in the measured electrical line A is It can be expressed as 4 (d). Note that, from FIG. 4D, the above-described equation (5) can be derived as an equation for calculating the R phase Igr. Further, the phase difference θ of the leakage current I ₀ changes depending on the magnitudes of the R phases Igr and Igc, and the range of change is 60 ° to 180 ° from the reference point.

For example, when only the T-phase Igr is generated in the measured electrical line A, the combined vector of the T-phase Igr and Igc, that is, the leakage current I ₀ flowing in the measured electrical line A is It can be expressed as 4 (e). Note that, from FIG. 4E, the above-described equation (5) can be derived as an equation for calculating the T-phase Igr. In addition, the phase difference θ of the leakage current I ₀ changes depending on the magnitudes of the T phases Igr and Igc, and the range of change is 120 ° to 180 °.

  Here, the operation of detecting the leakage current component flowing in the measured electrical line A by the leakage current detection apparatus 1 according to the present invention described above will be described with reference to the flowchart shown in FIG.

  In step ST1, the user switches a rotary switch (not shown) of the leakage current detection device 1 according to the type of electric wire to be measured (single-phase two-wire system, single-phase three-wire system, three-phase three-wire system, etc.). .

  In step ST2, the user connects the voltage probe to the voltage line of the electric wire to be measured. When the electric wire to be measured is a single-phase two-wire system (consisting of a voltage line and a ground line), pay attention to the polarity of the voltage line and connect a voltage probe to the voltage line. The voltage detection unit 14 supplies the voltage detected via the voltage probe to the transformer 15. In addition, when the electric wire to be measured is a single-phase three-wire type or a three-phase multi-wire type (three-phase three-wire type or three-phase four-wire type), A voltage probe is connected to the phase and T phase. The voltage detection unit 14 combines the voltages detected via the voltage probe, and supplies the combined voltage to the transformer 15.

  In step ST3, the user turns on the main power supply of the leakage current detection device 1.

  In step ST4, the user pays attention to the directions of K and L of the sensor unit (divided AC device) of the CT sensor unit 10 and sandwiches the ground wire or the measured electric wire path of the class B installation work in a lump. In the leakage current detection device 1, when the K and L directions of the sensor unit are aligned, the leakage current component is displayed on a display unit (not shown), and the K and L directions of the sensor unit are incorrect. If it is, a configuration in which a buzzer sounds from a buzzer output unit (not shown) may be used. Further, a K display and an L display may be attached to the handle portion of the sensor unit so that the direction in which the sensor unit is sandwiched is not mistaken.

  In step ST5, the user presses the measurement start button of the leakage current detection device 1. The leakage current detection device 1 detects the leakage current flowing in the measurement target electric line by pressing the measurement start button.

  Here, FIG. 6 shows a first result of actually measuring the leakage current component from the measured electric line by the leakage current detection apparatus 1 according to the present invention. FIG. 6 shows a power board (power frequency: 50 Hz, voltage: 200 V, type of low-voltage circuit to be measured: three-phase three-wire system, 150 kvA, room temperature: 41 ° C., humidity: 43 of a rooftop power distribution cubicle (high voltage power receiving equipment). %) Was measured.

  In the experiment, 20 kΩ was grounded to the R phase as a pseudo-insulation resistance 6 minutes to 9 minutes before the start of measurement (3 minutes), and 9 minutes to 11 minutes before the start of measurement (2 minutes). As a pseudo-insulation resistance, ground 20 kΩ in the T phase, remove the pseudo-insulation resistance (11 minutes) after the elapse of 11 minutes to 12 minutes (1 minute) from the start of measurement, and 12 to 13 minutes after the start of measurement. 10kΩ is grounded to the R phase as the pseudo-insulation resistance before the passage (1 minute), and 10kΩ is grounded to the T phase as the pseudo-insulation resistance at the time of 13 minutes to 15 minutes (2 minutes) after the start of measurement. 15 minutes later, the pseudo-insulation resistance was removed.

For example, when a 20 kΩ resistor is grounded to the R phase as the pseudo insulation resistance, theoretically, as the current of the pseudo insulation resistance component,
Igr = V / R = 200 / (20 × 10 ³ ) = 10 mA
Current is added to the line to be measured and flows.

  As shown in FIG. 6, the leakage current detection device 1 detected 12.3 mA Igr when grounding a resistance of 20 kΩ in the R phase as a pseudo-insulation resistance when the time was 6 minutes. Since Igr is 2 mA when the pseudo-insulation resistance is not grounded (before 6 minutes from the start of measurement, after 11 minutes from the start of measurement to 12 minutes before and after 15 minutes from the start of measurement), If 2 mA is subtracted from Igr after grounding the pseudo resistance of 20 kΩ, it becomes 10.3 mA. Therefore, the leakage current detection apparatus 1 according to the present invention can measure a change of 10.3 mA. This value almost coincides with the theoretical value (10 mA) described above.

In addition, when the pseudo insulation resistance is grounded to the R phase at 20 kΩ, the combined resistance value with the resistance value before grounding (Gr≈105.46 kΩ (average value of Gr from the start of measurement to 6 minutes before)) is
Gr = (20 × 10 ³ × 105.46 × 10 ³ ) / (20 × 10 ³ + 105.46 × 10 ³ ) ≈16.3 kΩ
It becomes. As shown in FIG. 6, the leakage current detection device 1 has a resistance Gr of 17.2 kΩ when 6 minutes have elapsed from the start of measurement, which substantially matches the above-described theoretical value (16.3 kΩ).

  Further, even when a 20 kΩ resistor is grounded as the pseudo-insulation resistance in the T phase, the current of the pseudo-insulation resistance component theoretically increases by 10 mA as described above. In the leakage current detection device 1, as shown in FIG. 6, the Igr detected from 9 minutes to 11 minutes after the start of measurement is approximately 12.4 mA, and when 2 mA is subtracted from the value, 10 g .4 mA, which almost coincides with the theoretical value (10 mA).

  Further, the combined resistance value Gr when the pseudo-insulation resistance is grounded to the T phase at 20 kΩ is theoretically 16.3 kΩ and the measured value is 17.4 kΩ, as described above. Is consistent with

  In addition, as shown in FIG. 6, the leakage current detection device 1 has a theoretical value and an actual measurement value that are substantially the same for Igr and Gr when 10 kΩ is grounded to the R phase or the T phase as a pseudo insulation resistance.

Further, the leak current detecting device 1, prior to the expiration 12 minutes from the start of measurement after elapse of 11 minutes, and when releasing the ground state of the pseudo insulation resistance when 15 minutes elapsed, Igr, the value of I ₀ and Gr ground earlier ( The state returned to the state of 1 minute to 5 minutes from the start of measurement.

  Moreover, the 2nd result which actually measured the leakage current component from the to-be-measured electric wire line by the leakage current detection apparatus 1 which concerns on this invention is shown in FIG. FIG. 7 shows a power board (power supply frequency: 50 Hz, voltage: 200 V, type of low-voltage circuit to be measured: three-phase three-wire system, 150 kvA) of a power distribution cubicle (high-voltage power receiving equipment) as a measurement target. .

  In the experiment, 1 minute elapsed from the start of measurement to 4 minutes before (3 minutes), 0.22 μF was grounded to the R phase and T phase as a pseudo capacitance, and 3 minutes elapsed from the start of measurement to 4 minutes. Before the lapse of time (1 minute), 20 kΩ was grounded to the T phase as a pseudo insulation resistance, and after 4 minutes from the start of measurement, the pseudo capacitance and the pseudo insulation resistance were removed. Therefore, from 3 minutes to 4 minutes before the start of measurement, the pseudo capacitance was grounded to the R phase and the T phase, and the pseudo insulation resistance was grounded to the T phase.

For example, when a capacitance of 0.22 μF is grounded to the R phase and the T phase as a pseudo capacitance, the capacitive reactance X is
X = 1 / 2πfC = 1 / (2π × 50 × (0.22 × 10 ⁻⁶ + 0.22 × 10 ⁻⁶ ))
≒ 7.23 × 10 ³
It becomes.

Therefore, the line to be measured has
I = V / X = 200 / 7.23 × 10 ³ ≈27.6 mA
The current is added and flows.

In addition, when a 20 kΩ resistor is grounded to the T phase as an insulation resistance, theoretically, as a current of a pseudo insulation resistance component,
Igr = V / R = 200 / (20 × 10 ³ ) = 10 mA
Current is added to the line to be measured and flows.

As shown in FIG. 7, the leakage current detection device 1 has a time when 1 minute has elapsed from the start of measurement, and when a capacitance of 0.22 μF is grounded in the R phase and the T phase as a pseudo capacitance, 7.8 mA of Igr was detected, and 100.8 mA of I ₀ was detected. Note that I ₀ is a combined current of the current Igr caused by the insulation resistance and the current Igc caused by the capacitance as described above.

  As shown in FIG. 7, the Igr when the pseudo capacitance is not grounded is 7.6 mA (Igr 1 minute before the start of measurement), so the pseudo capacitance is not added to the R phase and the T phase. When grounded, there is almost no change in Igr.

On the other hand, _{I 0} when not grounded pseudo capacitance is 75.9mA _{(I 0} before a lapse of one minute from the start of measurement). When the _I 0 after the pseudo capacitance ground (100.8mA) subtracting the pseudo-capacitance ground before _I 0 _{(75.9mA), 24.9mA} next, which is the Igc of the addition. This added Igc is almost equal to the theoretical value (27.6 mA).

In addition, as shown in FIG. 7, the leakage current detection device 1 has a pseudo-capacitance grounded in the R phase and the T phase, and a pseudo insulation resistance is grounded in the T phase (3 minutes from the start of measurement). From the elapsed time to 4 minutes before), 21.0 mA of Igr was detected, and 107.0 mA of I ₀ was detected.

  Subtracting Igr (8 mA (Igr after 3 minutes from the start of measurement)) before grounding the insulation resistance from Igr (21 mA) after grounding the insulation resistance to the T phase yields 13 mA, which is a theoretical value (10 mA) Is almost equal to

  Further, the operations of the comparison unit 18 and the calculation unit 19 when 10 kΩ is grounded as a pseudo insulation resistance in the R phase will be described with reference to FIGS.

  As shown in FIG. 8, the comparison unit 18 receives the converted voltage V <b> 1 from the LPF 12 and receives the voltage V <b> 2 from the LPF 16. The phase difference between the converted voltage V1 and the voltage V2 is 120 °. As shown in FIG. 9A, the comparison unit 18 performs square wave conversion on the converted voltage V <b> 1 input from the LPF 12, and outputs the converted signal to the calculation unit 19. Further, as shown in FIG. 9B, the comparison unit 18 performs square wave conversion on the voltage V <b> 2 input from the LPF 16 and outputs the converted signal to the calculation unit 19.

  As illustrated in FIG. 10, the arithmetic unit 19 performs EXOR based on the square wave signal of the converted voltage V2 and the square wave signal of the voltage V2. The computing unit 19 obtains a phase pulse width equal to or less than ¼ of one cycle based on the signal after EXOR, and outputs the obtained phase pulse width to the phase angle calculating unit 22.

  In step ST6, when the measurement is completed, the user turns off the power of the leakage current detection device 1.

The leakage current detection device 1 according to the present invention configured as described above detects the leakage current I flowing through the measured electric wire A, converts the detected leakage current I into a voltage, and converts the detected voltage into a harmonic from the converted voltage. The converted voltage V1 from which the wave component has been removed and the harmonic component has been removed, and the voltage V2 from the voltage line of the line A to be measured are detected, the harmonic component is removed from the detected voltage V2, and the harmonic component is removed. On the basis of the measured voltage V2, the phase angle θ of the leakage current I flowing in the measured electrical line A is accurately determined, and the accurate phase angle θ and the effective value of the converted voltage V1 from which the harmonic component has been removed. only for detecting a leakage current Igr resulting from the ground insulation resistance from I ₀ Metropolitan. Therefore, in the leakage current detection apparatus 1 according to the present invention, even if the measured electric line becomes long and the leakage current (Igc) due to the ground capacitance is increased by an inverter or the like that outputs a harmonic distortion current. , Since only the leakage current (Igr) caused by the ground insulation resistance can be reliably detected in units of mA, when the present invention is applied to the leakage current interrupting device, it depends on elements other than Igr (increased Igc). If the leakage current increases, the malfunction does not occur, and if the present invention is applied to a leakage alarm, it can be used without any false alarm even if the leakage current increases due to factors other than Igr. it can. Therefore, the leakage current detection device 1 according to the present invention is capable of safely and reliably causing a disaster such as a leakage fire without temporarily turning off the electric circuit / mechanical equipment when detecting the leakage current. In addition, it is possible to detect a leakage point.

  In addition, the leakage current detection device 1 according to the present invention does not bring in a reference point from another as in the frequency injection type, but obtains the reference point from the voltage generated in the transmission line. Igr flowing in A can be accurately measured.

It is a block diagram which shows the structure of the leakage current detection apparatus which concerns on this invention. It is a figure which shows the phase difference of Igr and Igc in the case where a power supply is a single phase and the case of three phases. It is the figure which showed a mode that the leakage current performed by the leakage current detection apparatus concerning this invention was detected. It is the figure which showed a mode that the leakage current performed by the leakage current detection apparatus based on this invention was detected with the vector. It is a flowchart explaining the operation | movement of the leakage current detection apparatus which concerns on this invention. It is a figure which shows the 1st data example when an electric wire path is actually measured by the leakage current detection apparatus which concerns on this invention. It is a figure which shows the 2nd data example when an electric wire path is actually measured by the leakage current detection apparatus which concerns on this invention. It is a figure which shows the phase difference of the converted voltage V1 and the voltage V2 which were input into the comparison part. FIG. (A) is a diagram showing a waveform of the converted voltage V1 when input to the comparison unit and a waveform when square wave conversion is performed based on the converted voltage V1, and FIG. It is a figure which shows the waveform when the waveform of the voltage V2 when input, and square wave conversion based on the voltage V2. It is a figure which shows the waveform formed when EXOR is performed based on the waveform when square-wave conversion is performed based on the voltage V1 after conversion shown in FIG. 9, and the waveform when square-wave conversion is performed based on the voltage V2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Leakage current detection apparatus, A to-be-measured electric wire line, 10 Current transformer sensor part (CT sensor part), 11 Amplification part, 12, 16 Low-pass filter (LPF), 13, 17 Full wave rectification part, 14 Voltage detection part, 15 Transformer, 18 comparison unit, 19 calculation unit, 20 phase pulse width measurement unit, 21 power supply frequency measurement unit, 22 phase angle calculation unit, 23, 25 A / D conversion unit, 24, 26 rms value calculation unit, 27 leakage current Calculation unit, 28 Resistance value calculation unit

Claims (6)

Leakage current detection means for detecting a leakage current flowing in a measured electric line with a single phase electrical method;
Voltage conversion means for converting the leakage current detected by the leakage current detection means into a voltage;
Voltage detecting means for detecting a voltage applied to the measured electric line;
A phase difference detection means for detecting a phase difference between a voltage signal waveform detected by the voltage detection means and a voltage signal waveform from the voltage conversion means;
Based on the signal waveform of the voltage detected by the voltage detection means, a frequency calculation means for calculating a power supply frequency applied to the measured electric line,
A phase angle calculating means for calculating a phase angle of a leakage current flowing in the measured electric line based on the phase difference detected by the phase difference detecting means and the power supply frequency calculated by the frequency calculating means;
An effective value calculating means for calculating an effective value of the leakage current detected by the leakage current detecting means;
Based on the effective value calculated by the effective value calculating means and the phase angle of the leakage current flowing in the measured electric wire calculated by the phase angle calculating means, the leakage current flowing in the measured electric wire A ground insulation resistance leakage current component calculating means for calculating a leakage current component caused by the ground insulation resistance included in
The effective value calculation means sets the average value of the leakage current detected by the leakage current detection means to I, and sets the effective value I ₀ to I ₀ = I × (π / 2) √2
Calculated by
The ground insulation resistance leakage current component calculation means includes an effective value I ₀ calculated by the effective value calculation means, and a phase angle θ of the leakage current flowing through the measured electric wire calculated by the phase angle calculation means. The leakage current component Igr caused by the ground insulation resistance included in the leakage current flowing through the measured electric line is expressed as Igr = I ₀ × cos θ
The leakage current detection device characterized by the above calculation. The phase angle calculation means calculates the phase angle θ of the leakage current detected by the leakage current detection means from the phase pulse width W detected by the phase difference detection means and the frequency F calculated by the frequency calculation means, θ = 360 x W x F
The leakage current detection device according to claim 1, wherein the leakage current detection device is calculated by: Comprising digital conversion means for digitally converting the leakage current detected by the leakage current detection means,
The effective value calculating means, the leak current detecting device according to claim 1, wherein calculating the effective value I ₀ of the average value I of the digitally converted said leakage current in the digital conversion means.   2. The leakage current detecting device according to claim 1, wherein the leakage current detecting means clamps a measured electric wire including a ground line and detects a leakage current flowing through the measured electric wire. A leakage current detection step for detecting a leakage current flowing in a measured electric line having a single-phase electrical method;
A voltage conversion step for converting the leakage current detected by the leakage current detection step into a voltage;
A voltage detection step of detecting a voltage applied to the measured electric line;
A phase difference detection step of detecting a phase difference between a voltage signal waveform detected by the voltage detection step and a voltage signal waveform from the voltage conversion step;
Based on the signal waveform of the voltage detected by the voltage detection step, a frequency calculation step for calculating the power supply frequency applied to the measured electric line,
A phase angle calculation step of calculating a phase angle of a leakage current flowing through the measured electric line based on the phase difference detected in the phase difference detection step and the power supply frequency calculated in the frequency calculation step;
An effective value calculation step of calculating an effective value of the leakage current detected by the leakage current detection step;
Based on the effective value calculated in the effective value calculating step and the phase angle of the leakage current flowing in the measured electric wire calculated in the phase angle calculating step, the leakage current flowing in the measured electric wire A ground insulation resistance leakage current component calculation step for calculating a leakage current component due to the ground insulation resistance included in
In the effective value calculating step, the average value of the leakage current detected in the leakage current detecting step is set as I, and the effective value I ₀ is set as I ₀ = I × (π / 2) √2
Calculated by
The ground insulation resistance leakage current component calculation step includes the effective value I ₀ calculated by the effective value calculation step and the phase angle θ of the leakage current flowing through the measured electric wire calculated by the phase angle calculation step. The leakage current component Igr caused by the ground insulation resistance included in the leakage current flowing through the measured electric line is expressed as Igr = I ₀ × cos θ
The leakage current detection method characterized by calculating by this. In the phase angle calculation step, the phase angle θ of the leakage current detected in the leakage current detection step is calculated from the phase pulse width W detected in the phase difference detection step and the frequency F calculated in the frequency calculation step. θ = 360 × W × F
The leakage current detection method according to claim 5, wherein the leakage current detection method is calculated by:

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