JP2019090693A - Partial discharge detector - Google Patents

Abstract

To provide a partial discharge detector with which can detect a partial discharge without relying on the power supply frequency of a facility whose partial discharge is to be detected.SOLUTION: The partial discharge detector comprises: an antenna type sensor 101 for detecting a current flowing through a ground line of a facility whose partial discharge is to be detected (rotary machine 100 to be measured) to which an AC power supply voltage is applied; a filter circuit 102 for removing low-frequency components from a detection output of the antenna type sensor 101; an envelope circuit 103 for converting the output signal of the filter circuit 102 to an envelope-shaped signal; a current sensor 104 for detecting the power supply current of the facility whose partial discharge is to be detected; a low-resolution analog board 105 for determining whether there is occurrence of a partial discharge, with the envelope-shaped signal converted by the envelope circuit 103 and the power supply current detected by the current sensor 104 used as inputs thereto.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for detecting a partial discharge generated in a winding of a transformer or a rotating machine, and more particularly to a partial discharge detection apparatus capable of measuring an area current and configuring the apparatus with an inexpensive analog board.

  FIG. 9 shows an example of a conventional partial discharge detection device. In FIG. 9, 100 is a to-be-measured rotary machine as partial discharge detection object installation to which alternating current power supply voltage is applied. Reference numeral 120 denotes a rotating machine housing that accommodates the measured rotating machine 100, and is grounded via a grounding wire.

  An antenna type sensor 101 is attached to the rotary machine housing 120 and detects a leaked electromagnetic wave generated by a partial discharge of the rotary machine 100 to be measured. The antenna type sensor 101 includes, for example, a surface current sensor, and captures a current flowing to the ground line through the rotary machine housing 120 by partial discharge.

  Reference numeral 102 denotes a filter circuit that removes noise components from the output of the antenna type sensor 101, and is configured of, for example, a high pass filter circuit.

  An analog board 300 analyzes the frequency component of the output signal of the filter circuit 102 to determine the occurrence of partial discharge.

  Moreover, as a conventional apparatus which detects a partial discharge signal and diagnoses the insulation abnormality of a diagnostic object, the thing of patent document 1 is proposed, for example.

JP, 2005-147890, A

  In the “insulation abnormality diagnostic device” described in Patent Document 1, a band pass filter is provided in the filter circuit, and only a frequency twice as high as the commercial power supply frequency, that is, 100 Hz frequency components twice as high as 50 Hz is detected. It is judged that partial discharge has occurred.

  However, this can not be used when the power supply frequency of the DUT is different from the design, and for example, when the power supply frequency is variable, such as when using an inverter (when the DUT is driven by the inverter), partial discharge It can not be detected.

  The present invention solves the above problem, and an object thereof is to provide a partial discharge detection device capable of detecting partial discharge without depending on the power supply frequency of the partial discharge detection target equipment.

The partial discharge detection device according to claim 1 for solving the above problems is
An antenna type sensor that detects a current flowing to a ground line of a partial discharge detection target equipment to which an alternating current power supply voltage is applied;
A filter for removing low frequency components from the detection output of the antenna type sensor;
An envelope circuit for converting an output signal of the filter into an envelope-like signal;
A current sensor that detects a power supply current of the partial discharge detection target facility;
And a low-resolution analog board that receives as input the envelope-like signal converted by the envelope circuit and the power supply current detected by the current sensor, and determines whether or not partial discharge has occurred.
The low resolution analog board is
A signal level determination unit that determines whether the input envelope-like signal is equal to or greater than a preset voltage level threshold signal;
An envelope-like signal in a set period of one cycle of the input power supply current detection signal from an envelope-like signal determined to be equal to or higher than a preset voltage level threshold signal by the signal level determination unit A signal extraction unit for extracting a waveform block;
A count unit that counts the number of lumps of the waveform of the envelope-like signal extracted by the signal extraction unit within a set time;
And a partial discharge occurrence determination unit that determines that partial discharge has occurred when the number of lumps of the waveform of the envelope-like signal counted by the counting unit is equal to or greater than a set number threshold value. It is characterized by

The partial discharge detection device according to claim 2 in claim 1,
The signal extraction unit extracts, from the envelope-like signal, a lump of the waveform of the envelope-like signal in a period in which a current obtained by full-wave rectification of the input power supply current is equal to or more than an effective value of the power supply current. It features.

The partial discharge detection device according to claim 3 in claim 1,
The signal extraction unit sets the power supply current from rising or falling of the full-wave rectified power supply current set by a signal obtained by differentiating the input power supply current from full-wave rectified current from the envelope-like signal. It is characterized by extracting the lump of the waveform of the envelope-like signal in the period up to the peak.

The partial discharge detection device according to claim 4 is the device according to any one of claims 1 to 3.
The antenna type sensor is attached to a housing that accommodates the partial discharge detection target equipment, and detects a current flowing through the housing to the ground line.

  According to the present invention, detection is performed only during a set period of the power supply current of the partial discharge detection target equipment detected by the current sensor to determine the occurrence of partial discharge, so the power supply frequency of the partial discharge detection target equipment Partial discharge can be detected without depending on

  For this reason, partial discharge can be detected even if the power supply frequency of the partial discharge detection target facility is variable, for example, when using an inverter.

  Also, since the output signal of the antenna type sensor is converted to an envelope-like signal through a filter and an envelope circuit, and the presence or absence of partial discharge occurrence is determined by the analog board, a low resolution analog board is used. Partial discharge can be detected. For this reason, cost reduction can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the partial discharge detection apparatus by Example 1 of this invention. The circuit diagram of the principal part of FIG. The wave form diagram of the output signal of the circuit of FIG. BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the low-resolution analog board in Example 1 of this invention. The block diagram showing the composition of the partial discharge detection device in the present invention. Explanatory drawing showing processing of the output signal of the antenna type sensor in the low-resolution analog board of Example 1 of this invention. The block diagram of the low-resolution analog board in Example 2 of this invention. Explanatory drawing showing processing of the output signal of the antenna type | mold sensor in the low-resolution analog board of Example 2 of this invention. The block diagram which shows an example of the conventional partial discharge detection apparatus. The schematic diagram of an antenna type sensor output.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. First, FIG. 10 shows a schematic view of a signal when the signal change generated by the partial discharge is captured by the antenna type sensor 101 in the conventional partial discharge detection device of FIG. FIG. 10 shows respective waveforms of the output voltage of the antenna type sensor 101 and the power supply current of the rotating object under test 100 (shown as the object under test in the drawing).

  In FIGS. 9 and 10, the signal flowing through the rotary machine casing 120 is usually only a noise component. When partial discharge occurs, a large signal fluctuation occurs due to the discharge phenomenon near the peak of the power supply current.

  However, the fluctuation of this signal is a high frequency phenomenon of megahertz or more. Therefore, the analog board 300 of the conventional partial discharge detection device is required to be compatible with high frequency components, and the frequency resolution must be high. Such analog boards are generally expensive.

  However, if the purpose is to detect a partial discharge, it is not necessary to measure this high frequency signal as it is, as long as changes due to the partial discharge can be captured. Therefore, in the present embodiment, a circuit system is adopted in which the output signal of the antenna type sensor is not directly input to the analog board, but is once input to the analog board through the analog envelope circuit.

  In addition, by providing a current sensor for detecting the power supply current of the partial discharge detection target equipment and performing detection only at the timing of the peak of the power supply current or the rise and fall of the power supply current, the partial discharge detection target equipment Partial discharge detection can be performed without depending on the power supply frequency.

  FIG. 1 shows the configuration of the partial discharge detection device according to the first embodiment, and the same parts as FIG. 9 are indicated by the same reference numerals. 1 differs from FIG. 9 in that the output signal of the filter circuit 102 obtained by removing noise components from the output of the antenna type sensor 101 is converted into an envelope-like signal to form an envelope circuit 103 for waveform formation. A current sensor 104 is inserted in the rotating machine power supply cable 130 that guides AC power to the rotating machine 100, detects the power supply current of the measured rotating machine 100 and acquires the power supply frequency, and replaces the analog board 300 with high frequency resolution. In that a low resolution analog board 105 is provided to receive the output signal of the envelope circuit 103 and the output signal of the current sensor 104 as input to determine the presence or absence of partial discharge occurrence, and the other parts are configured the same as FIG. ing.

  A specific example of the envelope circuit 103 is shown in FIG. In FIG. 2, reference numeral 51 denotes a diode to which an output signal of the filter circuit 102 (a signal obtained by removing noise (low frequency) components from the output of the antenna type sensor 101) is input to the anode side.

  One end of each of a capacitor 52 and a resistor 53 is connected to the cathode side of the diode 51, and the other ends of the capacitor 52 and the resistor 53 are commonly connected.

  The high frequency component of the signal input to the anode side of the diode 51 is removed by the circuit of FIG. 2, and the waveform close to the envelope of the input waveform, that is, the envelope is obtained on the output side (between the two ends of the resistor 53). Signal is obtained.

  An example of the envelope-like signal output from the envelope circuit 103 of FIG. 2 is shown in FIG. With an envelope-like signal as shown in FIG. 3, even a low-resolution analog board (105) such as an analog board with a resolution of several tens of kHz can be sampled, and this enables partial discharge detection can get.

  The low resolution analog board 105 is configured as shown in FIG. 4 in the first embodiment. In FIG. 4, an envelope-like signal a which is the output of the envelope circuit 103 is input to the positive side input end of the comparator 11 (comp1) and one end of the switch 14 (S1).

  The comparator 11 divides the envelope-like signal a input to the positive side input terminal and the voltage of the control power supply (not shown) input to the negative side input terminal by the resistor 12 and the variable resistor 13 (VR1). The voltage level determination result signal c is output by comparing the obtained voltage level threshold signal b (preset voltage level threshold signal).

  The switch 14 is on / off controlled by the voltage level determination result signal c output from the comparator 11, and is on when the envelope-like signal a is equal to or higher than the voltage level threshold signal b. It will be off.

  Therefore, only the envelope-like signal a equal to or higher than the preset voltage level threshold signal b is obtained at the other end of the switch 14.

  The comparator 11, the resistor 12, the variable resistor 13 and the switch 14 constitute a signal level determination unit of the present invention.

  The other end of the switch 14 is connected to one end of the switch 15 (S2), and the power supply current instantaneous value d which is an output signal of the current sensor 104 (the power supply current of the rotary machine 100 to be measured The sensed signal is input to the diode bridge 16 (full wave rectification circuit) and the effective value detection circuit 17. The diode bridge 16 rectifies the power supply current instantaneous value d, converts it into a full wave rectified signal e of the power supply current, and inputs it to the positive side input end of the comparator 18 (comp2).

  The effective value detection circuit 17 converts the instantaneous value d of the power supply current into the effective value signal f of the power supply current and inputs it to the negative input terminal of the comparator 18.

  The comparator 18 compares the full-wave rectified signal e of the power supply current with the effective value signal f of the power supply current to output a peak extraction signal g of the power supply current.

  The switch 15 is on / off controlled by the peak extraction signal g of the power supply current output from the comparator 18, and is turned on when the full-wave rectified signal e of the power supply current is larger than the effective value signal f of the power supply current. If it is smaller than f, it will be off.

  Therefore, at the other end of the switch 15, only the envelope-like signal a at a timing near the power supply current equal to or higher than the effective value, ie, when the power supply current peaks, is obtained.

  The switch 15, the diode bridge 16, the effective value detection circuit 17 and the comparator 18 constitute a signal extraction unit of the present invention.

  The other end of the switch 15 is connected to the input end of the envelope signal block number counter circuit 19 and one end of the resistor 20, and the other end of the resistor 20 is grounded.

  The envelope-like signal block number counter circuit 19 counts the number of waveforms of the envelope-like signal a in the vicinity of the peak of the power supply current input through the switch 15, and the digital envelope-like signal block number The counter output signal k is output.

  Reference numeral 21 denotes a crystal oscillator which oscillates a signal of a predetermined frequency and outputs a crystal oscillator output signal h.

  Reference numeral 22 denotes a crystal oscillator counter circuit which counts up every time the crystal oscillator output signal h rises and outputs a crystal oscillator counter output signal i.

  23 indicates whether the crystal oscillator counter output signal i has reached a set value (a set value for determining the count time of the envelope signal block number counter circuit 19 and the crystal oscillator counter circuit 22) set to itself. Is a decoder circuit that decodes the

  The decoder output signal j of the decoder circuit 23 becomes inactive when the crystal oscillator counter output signal i is less than the set value of the decoder circuit 23, and becomes active when the crystal oscillator counter output signal i reaches the set value of the decoder circuit 23. .

  The decoder output signal j is introduced into the envelope signal block number counter circuit 19 and the crystal oscillator counter circuit 22. When the decoder output signal j becomes active, the count operations of the counter circuits 19 and 22 are each reset. , 0. The envelope-like signal block number counter output signal k and the crystal oscillator counter output signal i are set to 0.

  Therefore, the envelope-like signal block number counter circuit 19 continues to count up from 0 every time the envelope-like signal a in the vicinity of the peak of the power supply current is input from the switch 15, and is reset by the decoder output signal j. Then, the envelope-like signal block number counter output signal k is returned to the output 0.

  Therefore, the number of waveforms of the envelope-like signal a in the set time is obtained as the envelope-like signal block number counter output signal k.

  The envelope-like signal block number counter output signal k is input to the D / A conversion circuit 24 to be converted from digital to analog, and the D / A conversion circuit 24 outputs a D / A conversion output signal l. Therefore, the D / A conversion output signal l is an analog voltage signal corresponding to the digital envelope-like signal block number counter output signal k.

  The envelope-like signal block number counter circuit 19, the resistor 20, the crystal oscillator 21, the crystal oscillator counter circuit 22, the decoder circuit 23 and the D / A conversion circuit 24 constitute a count unit of the present invention.

  Reference numeral 25 denotes a comparator (comp3) to which the D / A conversion output signal l is input to the positive side input terminal.

  The comparator 25 divides the D / A converted output signal 1 input to the positive side input terminal and the voltage of the control power supply (not shown) input to the negative side input terminal by the resistor 26 and the variable resistor 27 (VR2). The partial discharge detection signal n is output to the CPU 28 by comparing it with the envelope-like signal block number threshold value signal m (set block number threshold value) obtained as a result.

  The partial discharge detection signal n is activated when the D / A converted output signal l is larger than the envelope signal block number threshold signal m, and the CPU 28 assumes that partial discharge has occurred, and the l is greater than m. If it is too small, it becomes inactive, and the CPU 28 does not consider that partial discharge has occurred.

  The partial discharge occurrence determination unit of the present invention is configured by the comparator 25, the resistor 26, the variable resistor 27 and the CPU 28.

  It is as FIG. 5 when only the principal part structure of the partial discharge detection apparatus of Example 1 shown to FIGS. 1-4 is represented with a block.

  Next, the operation of the partial discharge detection device of the first embodiment shown in FIGS. 1 to 5 will be described with reference to FIG. 6 showing processing of an output signal of an antenna type sensor on a low resolution analog board.

  (1) The antenna type sensor 101 detects the current flowing through the rotary machine housing 120, and the current sensor 104 detects the power supply current of the measured rotary machine 100 flowing through the rotary machine power cable 130. The output of the antenna type sensor 101 is input to a filter circuit 102 (for example, a high pass filter circuit) to remove low frequency components.

  (2) The signal output from the filter circuit 102 is input to the envelope circuit 103 and converted into an envelope-like signal a as shown in FIG.

  (3) The envelope signal a output from the envelope circuit 103 and the power supply current instantaneous value d output from the current sensor 104 are input to the low resolution analog board 105, and the low resolution analog board 105 Signal processing shown to (3)-(3-4) is performed, and partial discharge detection is performed.

  (3-1) Referring to FIG. 4, the voltage level threshold signal b set by the variable resistor 13 (VR1) and the envelope signal a output from the envelope circuit 103 are compared by the comparator 11, and the voltage level determination result signal c Output The relationship between the envelope-like signal a and the voltage level threshold signal b is as shown in the upper part of FIG. When the envelope-like signal a is larger than the voltage level threshold signal b, the switch 14 is turned on according to the voltage level determination result c. Also, when the envelope-like signal a is smaller than the voltage level threshold signal b, the switch 14 is turned off according to the voltage level determination result c, and removed when the voltage level of the input signal (a) does not reach the threshold (b) Be done. Thereby, only the envelope-like signal a having the voltage level threshold signal b or more set in advance is obtained.

  (3-2) The power supply current instantaneous value d is converted into a full wave rectified signal e of the power supply current by the diode bridge 16 and is input to the positive side input terminal of the comparator 18. Further, the power supply current instantaneous value d is converted to the power supply current effective value signal f by the effective value detection circuit 17 and is input to the negative input terminal of the comparator 18.

  When the full wave rectified signal e of the power supply current is larger than the effective value signal f of the power supply current, the switch 15 is turned on by the peak extraction signal g of the power supply current output from the comparator 18. When the full wave rectification signal e of the power supply current is smaller than the effective value signal f of the power supply current, the switch 15 is turned off by the peak extraction signal g of the power supply current.

  As a result, only the envelope-like signal a of the timing before and after the power supply current is equal to or more than the effective value, that is, the power supply current becomes peak is obtained. Therefore, as shown in the middle part of FIG. 6, the antenna-type sensor output (envelope-like signal) in a period in which the relationship between the full wave rectified signal e of the power supply current and the effective value signal f is e> f Only a) is extracted.

  (3-3) While the switch 15 is on, the envelope-like signal a is input to the envelope-like signal block number counter circuit 19, and the envelope-like signal block number counter circuit 19 generates the waveform block of the envelope-like signal a. The number is counted to output a digital envelope-like signal block number counter output signal k.

  On the other hand, the crystal oscillator output signal h from the crystal oscillator 21 is input to the crystal oscillator counter circuit 22, the crystal oscillator counter circuit 22 outputs the crystal oscillator counter output signal i, and the crystal oscillator counter output signal i is the decoder circuit 23 Is input to

  Every time the crystal oscillator output signal h rises, the crystal oscillator counter circuit 22 counts up the crystal oscillator counter output signal i. When the crystal oscillator counter output signal i reaches a set value preset in the decoder circuit 23, the decoder output signal j of the decoder circuit 23 becomes active. When the crystal oscillator counter output signal i is less than the set value of the decoder circuit 23, the decoder output signal j becomes inactive.

  When the decoder output signal j becomes active, the crystal oscillator counter circuit 22 and the envelope signal block number counter circuit 19 are reset. The reset envelope-like signal block number counter circuit 19 and the crystal oscillator counter circuit 22 set the respective output signals, that is, the envelope-like signal block number counter output signal k and the crystal oscillator counter output signal i to zero.

  The envelope-like signal block number counter circuit 19 sets the envelope-like signal block number counter output signal k to 0 until it is reset by the decoder output signal j every time the envelope-like signal block is input through the switch 15. Continues counting up, and when reset by j, the envelope-like signal block number counter output signal k is returned to the output 0.

  The state of the count processing in the envelope-like signal block number counter circuit 19 is as shown in the lower part of FIG. In the lower part of FIG. 6, the signal surrounded by the broken line is the input of the envelope-like signal a (near the power supply current peak) (the envelope-like signal block number counter circuit 19 extracted in the range of e> f in the middle of FIG. 6) is a period until the envelope-like signal block number counter circuit 19 starts counting and is reset by the decoder output signal j. It corresponds to the setting value of.

  (3-4) The envelope-like signal block number counter output signal k output from the envelope-like signal block number counter circuit 19 is input to the D / A conversion circuit 24, and the D / A conversion circuit 24 is an envelope-like signal The D / A conversion output l corresponding to the block number counter output signal k is output and input to the comparator 25.

  The D / A conversion output l is compared by the comparator 25 with the envelope-like signal block number threshold signal m set by the variable resistor 27 (VR2), and the D / A conversion output l is the envelope-like signal block number threshold signal m If larger, the partial discharge detection signal n is activated, and the CPU 28 considers that a partial discharge has occurred.

  Further, when the D / A conversion output 1 is smaller than the envelope-like signal block number threshold signal m, the partial discharge detection signal n is inactivated by the comparator 25 and the CPU 28 does not consider that the partial discharge has occurred.

  Thus, the partial discharge detection function using the low resolution analog board can be obtained.

  As described above, according to the first embodiment, partial discharge can be detected without depending on the power supply frequency of the partial discharge detection target equipment (the rotary machine 100 to be measured). For this reason, partial discharge can be detected even if the power supply frequency of the partial discharge detection target facility is variable, for example, when using an inverter.

  Also, since the output signal of the antenna type sensor 101 is converted to an envelope-like signal through the filter circuit 102 and the envelope circuit 103 and the low resolution analog board 105 determines the presence or absence of partial discharge occurrence, it is low. Partial discharge can be detected using a resolution analog board. For this reason, cost reduction can be achieved.

  In the first embodiment, the system is configured to detect partial discharge in the vicinity of the peak of the power supply current of the measured rotating machine 100. However, as shown in FIG. 10, when the partial discharge is detected using the antenna type sensor 101, the sensor output is not only near the peak of the power supply current of the rotary machine under test 100, but also at the rise and fall of the power supply current. There is also a possibility of large fluctuations at times.

  In the second embodiment, therefore, the partial discharge is detected in a period from the rise or fall of the power supply current to the peak of the power supply current.

  The partial discharge detection apparatus according to the second embodiment is a low detection circuit that detects a partial discharge in a period from the rise or fall of the power supply current to the peak of the power supply current, instead of the low resolution analog board 105 in FIGS. A resolution analog board 205 is provided, and the other parts are configured the same as in FIG. 1 and FIG.

  The low resolution analog board 205 of the second embodiment is configured as shown in FIG. In FIG. 7, the same parts as those in FIG. 4 are indicated by the same reference numerals. 7 differs from FIG. 4 in that the switch 15, the diode bridge 16, the diode bridge 16, and the derivative instead of the circuit of the switch 15, the diode bridge 16, the effective value detection circuit 17 and the comparator 18 which constitute the signal extraction unit of FIG. The point is that a signal extraction unit configured by the circuit 31 and the circuit of the comparator 32 (comp 4) is provided, and the other parts are configured the same as FIG. 4.

  In FIG. 7, a power supply current instantaneous value d which is an output signal of the current sensor 104 is input to the diode bridge 16. The diode bridge 16 rectifies the power supply current instantaneous value d to convert it into a full wave rectified signal e of the power supply current, and inputs it to the differentiating circuit 31.

  The differentiating circuit 31 differentiates the full wave rectified signal e of the power supply current, and inputs the differentiated signal p of the full wave rectified power supply current to the positive input terminal of the comparator 32.

  The comparator 32 compares the differential signal p of the full-wave rectified power supply current input with the ground potential (0) of the negative side input terminal, and outputs a rise detection signal q of the full-wave rectified power supply current.

  The switch 15 is on / off controlled by the rise detection signal q of the full wave rectified power supply current output from the comparator 32, and is turned on when the differential signal p of the full wave rectified power supply current is larger than the ground potential 0, the p Is smaller than 0, it is off.

  Therefore, at the other end of the switch 15, only the envelope-like signal a in the period from the rise or fall of the power supply current to the peak is obtained.

  Next, the operation of the second embodiment using the low resolution analog board 205 of FIG. 7 instead of the low resolution analog board 105 of FIGS. 1 and 5 is the processing of the output signal of the antenna type sensor in the low resolution analog board. This will be described together with FIG.

  First, the operations of the antenna type sensor 101, the filter circuit 102, the envelope circuit 103 and the current sensor 104 are the same as the operations (1) and (2) of the first embodiment described above.

  Next, among the operations of the low resolution analog board 205, the operation performed by the signal level determination unit to determine whether the envelope-like signal a is the voltage level threshold signal b or more is the operation of the first embodiment described above. It becomes the same as (3-1). The relationship between the envelope-like signal a and the voltage level threshold signal b is the same as in the upper part of FIG. 6 and in the upper part of FIG.

  In addition, partial discharge occurred when the number (k, l) of lumps of the waveform of the envelope-like signal counted by the count unit, which is performed by the partial discharge occurrence determination unit, is equal to or greater than the set threshold value (m) The operation to determine that is the same as the operation (3-4) of the first embodiment described above.

  Next, among the operations of the low resolution analog board 205, an operation (13-2) performed by the signal extraction unit, which is different from the operation (3-2) of the above-described first embodiment, and the above-described embodiment An operation (13-3) different from the operation (3-3) of Example 1 will be described.

  (13-2) In the signal extraction unit including the switch 15, the diode bridge 16, the differentiating circuit 31, and the comparator 32 in FIG. 7, the power supply current instantaneous value d is converted by the diode bridge 16 into a full wave rectified signal e of the power supply current It is input to the differentiation circuit 31. Further, the full wave rectified signal e of the power supply current is converted into a differentiated signal p of the full wave rectified power supply current by the differentiating circuit 31, and the differentiated signal p of the full wave rectified power supply current is input to the comparator 32.

  When the differential signal p of the full-wave rectified power supply current is larger than 0, which is the ground potential, the switch 15 is turned on by the rising detection signal q of the full-wave rectified power supply current which is the output of the comparator 32. When the differential signal p of the full-wave rectified power supply current is smaller than 0, the switch 15 is turned off by the rise detection signal q of the full-wave rectified power supply current.

  Thereby, only the envelope-like signal a in the period from the rise or fall of the power supply current to the peak is obtained. That is, a period in which the differential signal p of the full wave rectified power supply current obtained by differentiating the full wave rectified signal e of the power supply current is p> 0 as shown in the middle part of FIG. Only the antenna-type sensor output (envelope-like signal a)) is extracted.

  (13-3) While the switch 15 is on, the envelope-like signal a is input to the envelope-like signal block number counter circuit 19, and the envelope-like signal block number counter circuit 19 generates the waveform block of the envelope-like signal a. The number is counted to output a digital envelope-like signal block number counter output signal k.

  On the other hand, the crystal oscillator output signal h from the crystal oscillator 21 is input to the crystal oscillator counter circuit 22, the crystal oscillator counter circuit 22 outputs the crystal oscillator counter output signal i, and the crystal oscillator counter output signal i is the decoder circuit 23 Is input to

  Every time the crystal oscillator output signal h rises, the crystal oscillator counter circuit 22 counts up the crystal oscillator counter output signal i. When the crystal oscillator counter output signal i reaches a set value preset in the decoder circuit 23, the decoder output signal j of the decoder circuit 23 becomes active. When the crystal oscillator counter output signal i is less than the set value of the decoder circuit 23, the decoder output signal j becomes inactive.

  When the decoder output signal j becomes active, the crystal oscillator counter circuit 22 and the envelope signal block number counter circuit 19 are reset. The reset envelope-like signal block number counter circuit 19 and the crystal oscillator counter circuit 22 set the respective output signals, that is, the envelope-like signal block number counter output signal k and the crystal oscillator counter output signal i to zero.

  The envelope-like signal block number counter circuit 19 sets the envelope-like signal block number counter output signal k to 0 until it is reset by the decoder output signal j every time the envelope-like signal block is input through the switch 15. Continues counting up, and when reset by j, the envelope-like signal block number counter output signal k is returned to the output 0.

  The state of the count processing in the envelope-like signal block number counter circuit 19 is as shown in the lower part of FIG. In the lower part of FIG. 8, the signal surrounded by the broken line is an envelope-like signal a (in a period from the rise or fall of the power supply current to the peak) extracted in the range of p> 0 in the middle of FIG. The “set period” described in the lower part of FIG. 8 is an input signal of the linear signal block number counter circuit 19), and the enveloped signal block number counter circuit 19 starts counting and is reset by the decoder output signal j. Period, which corresponds to a set value in the decoder circuit 23.

  As described above, according to the second embodiment, the operations (1), (2), (3-1), (13-2), (13-3), and (3-4) described above are compared with the first embodiment. The same effect is obtained.

  That is, the partial discharge can be detected without depending on the power supply frequency of the partial discharge detection target equipment (the rotary machine 100 to be measured). For this reason, partial discharge can be detected even if the power supply frequency of the partial discharge detection target facility is variable, for example, when using an inverter.

  In addition, since the output signal of the antenna type sensor 101 is converted to an envelope-like signal through the filter circuit 102 and the envelope circuit 103 and the low resolution analog board 205 determines the presence or absence of partial discharge, it is low. Partial discharge can be detected using a resolution analog board. For this reason, cost reduction can be achieved.

11, 18, 25, 32 ... Comparator 12, 20, 26, 53 ... Resistance 13, 27 ... Variable resistance 14, 15 ... Switch 16 ... Diode bridge 17 ... Effective value detection circuit 19 ... Envelope-like signal block number counter circuit 21 ... Crystal oscillator 22 ... Counter circuit for crystal oscillator 23 ... Decoder circuit 24 ... D / A conversion circuit 28 ... CPU
31 differential circuit 51 diode 52 capacitor 100 rotating machine under test 101 antenna type sensor 102 filter circuit 103 envelope circuit 104 current sensor 105, 205 low resolution analog board 120 rotating machine housing 130 Rotating machine power cable

Claims (4)

An antenna type sensor that detects a current flowing to a ground line of a partial discharge detection target equipment to which an alternating current power supply voltage is applied;
A filter for removing low frequency components from the detection output of the antenna type sensor;
An envelope circuit for converting an output signal of the filter into an envelope-like signal;
A current sensor that detects a power supply current of the partial discharge detection target facility;
And a low-resolution analog board that receives as input the envelope-like signal converted by the envelope circuit and the power supply current detected by the current sensor, and determines whether or not partial discharge has occurred.
The low resolution analog board is
A signal level determination unit that determines whether the input envelope-like signal is equal to or greater than a preset voltage level threshold signal;
An envelope-like signal in a set period of one cycle of the input power supply current detection signal from an envelope-like signal determined to be equal to or higher than a preset voltage level threshold signal by the signal level determination unit A signal extraction unit for extracting a waveform block;
A count unit that counts the number of lumps of the waveform of the envelope-like signal extracted by the signal extraction unit within a set time;
And a partial discharge occurrence determination unit that determines that partial discharge has occurred when the number of lumps of the waveform of the envelope-like signal counted by the counting unit is equal to or greater than a set number threshold value. A partial discharge detection device characterized by   The signal extraction unit extracts, from the envelope-like signal, a lump of the waveform of the envelope-like signal in a period in which a current obtained by full-wave rectification of the input power supply current is equal to or more than an effective value of the power supply current. The partial discharge detection device according to claim 1, characterized in that   The signal extraction unit sets the power supply current from rising or falling of the full-wave rectified power supply current set by a signal obtained by differentiating the input power supply current from full-wave rectified current from the envelope-like signal. 2. The partial discharge detection device according to claim 1, wherein a lump of the waveform of the envelope-like signal in a period up to the peak is extracted.   The antenna type sensor according to any one of claims 1 to 3, wherein the antenna type sensor is attached to a housing that accommodates the partial discharge detection target equipment, and detects the current flowing through the housing to the ground line. Partial discharge detection device as described.

Images