JP2013142672A - Partial discharge measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test power supply of a partial discharge measuring device, which achieves a low noise level and low power consumption and in which a transformer having a small boosting ratio can be used.SOLUTION: According to the control of a personal computer 200, an AC voltage which rises or drops with the passage of time is outputted from a voltage control circuit 103, is amplified by an amplifier 104 which is a class-D amplifier, is boosted by a first transformer 106 at a boosting ratio that a maximum effective voltage becomes equal to a commercial power supply voltage, and is boosted, for example, to a measuring AC voltage of 5 kV by a second transformer 107.

Description

  The present invention relates to a partial discharge measuring apparatus for measuring a partial discharge generated when a high voltage is applied to an insulator.

  Partial discharges, which are weak discharges caused by defects such as voids and scratches in insulators such as electrical equipment, electronic parts and power cables, and abnormally concentrated areas of electric fields, accelerate the deterioration of the insulators and cause dielectric breakdown. It becomes a cause. Therefore, a partial discharge measuring device is used in order to prevent manufacturing defects and failures of these electric devices and the like. In particular, in recent years, partial discharge measurement is not limited to high-voltage devices, for example, in the inspection of low-voltage products such as low-voltage motors used in household appliances, and in the insulation performance test of a backsheet provided on the back of a solar cell. The importance of is increasing.

  As the partial discharge measuring device, for example, a device is known in which a winding failure of a motor is determined by an increase in discharge charge when an AC voltage of 800 V to 1100 V is applied to a specimen (see, for example, Patent Document 1). ).

  Also known is a device that amplifies a sine wave voltage generated by an oscillator with an amplifier, applies an AC voltage boosted by a transformer to a specimen, and controls the amplitude of the sine wave voltage generated by the oscillator by a voltage control program. (For example, refer to Patent Document 2). In this apparatus, the reliability of obtained data is improved by controlling the rate of increase of the applied voltage to be constant.

JP-A-3-246472 JP 2011-99775 A

  However, when the sine wave voltage generated by the oscillator is amplified by an amplifier and boosted by a transformer as described above, a large amount of power is consumed by the amplifier and a transformer having a large boost ratio is required. Had.

  The present invention has been made in view of such points, and an object of the present invention is to enable a partial discharge measuring device to easily reduce power consumption and to use a transformer with a small step-up ratio. is there.

The first invention is
A power supply circuit for applying an AC voltage for measurement to the specimen;
A measuring unit for measuring a partial discharge generated in the specimen in a state in which the measurement AC voltage is applied;
A partial discharge measuring device comprising:
The power circuit is
An amplifier that amplifies a pulse width modulation signal in which an AC voltage is pulse width modulated, and outputs the amplified signal via a low-pass filter;
A first transformer that boosts the output of the amplifier and outputs an AC voltage whose maximum effective voltage is a commercial power supply voltage;
A second transformer that boosts the output of the first transformer and outputs an AC voltage for measurement;
It is characterized by having.

  As a result, an AC voltage that is boosted by the transformer is generated by the pulse width modulation signal, so that power consumption can be greatly reduced even if the amplification degree is increased. Furthermore, since the boosting to the AC voltage for measurement is performed by two transformers, the boosting ratio of each transformer can be set small. Further, as the second transformer, a transformer capable of boosting the commercial power supply voltage to the measurement AC voltage can be used, so that a general-purpose transformer or the like can be easily applied.

The second invention is
A partial discharge measuring device according to a first invention,
The amplifier includes a modulation circuit that performs pulse width modulation on an alternating voltage controlled to a predetermined voltage;
A switching element for amplifying the pulse width modulation signal;
It is characterized by having.

  Thereby, the amplifier as described above can be easily configured.

The third invention is
The partial discharge measuring device according to any one of the first invention and the second invention,
The carrier frequency of the pulse width modulation is set to a frequency different from the measurement band in the measurement unit.

The fourth invention is:
A partial discharge measuring device according to a third invention,
The measurement band in the measurement unit is in the range of 15 kHz or more and 150 kHz or less, and the carrier frequency of the pulse width modulation is set to 400 kHz.

In addition, the fifth invention,
A partial discharge measuring device according to any one of the first to fourth inventions,
At least one of an LC filter, a noise removal capacitor, and a blocking coil is provided on at least one of the input side, the output side, and the output side of the second transformer. To do.

  As a result, the influence of noise or the like on the measurement accuracy can be easily suppressed.

The sixth invention is:
The partial discharge measuring device according to any one of the first to fifth aspects,
The measurement unit is configured to measure a voltage change that occurs when a partial discharge occurs in the specimen by a detection impedance connected to a low-voltage side of the coupling capacitor.

  Thereby, since the voltage change at the time of partial discharge generation is proportional to the magnitude | size of a discharge charge, a discharge charge can be measured easily.

The seventh invention
A partial discharge measuring device according to a sixth invention,
The measurement unit is further configured to measure a voltage actually applied to the specimen in conjunction with the measurement of the discharge charge.

  Thereby, it is possible to easily obtain an accurate relationship between the applied voltage and the discharge charge.

The eighth invention
The partial discharge measuring device according to any one of the first to seventh inventions,
A calibration pulse generating circuit is connected to a terminal for applying the measurement AC voltage to the specimen.

  Thereby, it is possible to perform calibration and measurement without attaching / detaching the calibration pulse generating circuit each time measurement is performed.

  In the present invention, in the partial discharge measuring device, it is possible to easily reduce power consumption and to use a transformer with a small step-up ratio.

It is a block diagram which shows the structure of the partial discharge measuring apparatus 100 of embodiment of this invention. 3 is a block diagram showing a specific configuration of a voltage control circuit 103 of the partial discharge measuring apparatus 100. FIG. 3 is a block diagram showing a specific configuration of an amplifier 104 of the partial discharge measuring apparatus 100. FIG. 3 is a graph showing an example of input / output signals of a comparator 104a of an amplifier 104. 4 is a flowchart showing processing performed by the personal computer 200. 5 is an explanatory diagram showing an example of a setting operation screen for a voltage applied to a specimen 300. FIG. 3 is a graph showing an example of a voltage applied to a specimen 300. 5 is a graph showing an example of a relationship between a voltage applied to a specimen 300 and a discharge charge. 5 is an explanatory diagram illustrating an example of a setting operation screen for a step voltage applied to a specimen 300. FIG. 3 is a graph showing an example of a step voltage applied to a specimen 300.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the partial discharge measuring apparatus 100 according to the present embodiment measures partial discharge when a measurement AC voltage is applied to the specimen 300 by combining with a personal computer 200, for example. .

  The specimen 300 is an object for inspecting partial discharge. Specifically, for example, a resin film such as a back sheet or a laminated body provided on the back surface of a solar cell, a power module integrated circuit, an IGBT (Insulated gate bipolar transistor). ), Or an element such as a small motor, or an element or device including the insulator.

  Further, the personal computer 200 controls the temporal transition of the voltage applied to the specimen 300, and performs processing such as determination of the presence / absence of partial discharge based on the measurement result by the partial discharge measuring device 100. Yes. The personal computer 200 is not limited to being used independently as described above, and a part or all of the functions may be provided in the partial discharge measuring apparatus 100.

  Hereinafter, the configuration of the partial discharge measuring apparatus 100 will be described in detail.

  The digital input / output circuit 101 functions as an interface for transmitting / receiving a signal input / output to / from the personal computer 200. Specifically, for example, based on a voltage control signal sent from the personal computer 200, a 12-bit voltage value signal taking values in 4096 steps from 0 to 4095 is output.

  The oscillation circuit 102 outputs an alternating voltage (a sine wave that is an analog signal) having a predetermined voltage at a frequency of 50 Hz or 60 Hz, for example, by a resistance tuning oscillation circuit.

  The voltage control circuit 103 outputs an AC voltage of, for example, 0 to 12.5 Vrms according to the voltage value signal output from the digital input / output circuit 101 based on the AC voltage generated by the oscillation circuit 102. Specifically, as shown in FIG. 2, for example, a D / A conversion circuit 103a that D / A converts a voltage value signal output from the digital input / output circuit 101 and outputs an analog voltage of 0 to 5 V, for example. The multiplication circuit 103b that multiplies the analog voltage and the AC voltage output from the oscillation circuit 102, the amplifier 103c that amplifies the multiplied voltage, and the CR filter 103d.

  The amplifier 104 is a so-called class D amplifier, and is a low-noise amplifier that amplifies the AC voltage output from the voltage control circuit 103 and outputs an amplified AC voltage having a maximum effective voltage of 24V, for example. Specifically, for example, as shown in FIG. 3, a comparator 104 a, a MOSFET 104 b (metal oxide semiconductor field-effect transistor), and a low-pass filter 104 c are provided. Further, the amplifier 104 outputs, for example, a triangular wave (carrier wave) of 400 kHz (that is, different from a frequency band of 15 kHz to 150 kHz, which is a measurement band) for pulse width modulation of the AC voltage output from the voltage control circuit 103. A triangular wave generation circuit (not shown) is also provided. The comparator 104a is a modulation circuit that outputs a pulse width modulated (PWM) PWM signal as shown in FIG. 4 based on the magnitude relationship between the AC voltage output from the voltage control circuit 103 and the triangular wave. The MOSFET 104b is a switching element that amplifies the PWM signal by turning on and off the power supply voltage. The low-pass filter 104c outputs an alternating voltage based on the amplified PWM signal.

  The amplifier power supply circuit 105 supplies a power supply voltage to the amplifier 104. For example, the amplifier power supply circuit 105 includes a power transformer 105a such as a toroidal transformer that steps down the commercial power supply voltage, a bridge rectifier circuit 105b, and a smoothing capacitor 105c. Has been.

  The first transformer 106 boosts the AC voltage output from the amplifier 104 at a boost ratio at which the highest effective voltage is the commercial power supply voltage.

  The second transformer 107 further boosts the AC voltage boosted by the first transformer 106 and outputs a measurement AC voltage of, for example, 5000V.

  The noise removal capacitor 108 removes noise propagating from the first transformer 106 to the second transformer 107.

  The blocking coil 109 prevents the partial discharge pulses from the specimen 300 from flowing out. Not only the noise removing capacitor 108 and the blocking coil 109 as described above, but also an LC filter, a noise removing capacitor, and / or a blocking coil are connected to the input and output sides of the first and second transformers 106 and 107. You may make it do.

  The applied voltage measuring capacitors 110 and 111 are for measuring a voltage actually applied to the specimen 300.

  The calibration pulse generation circuit 112 is a circuit in which, for example, a circuit that generates a square wave voltage and a capacitor are connected in series, and a calibration pulse of a known charge is generated. The calibration pulse is applied to the specimen 300 by passing the rectangular wave voltage at, and the rating is set to withstand the AC voltage for measurement from the second transformer 107 during the partial discharge measurement.

  The coupling capacitor 113 is connected to the signal amplification circuit 114 on the low voltage side, and detects a minute voltage change that occurs when a partial discharge occurs in the specimen 300.

  The signal amplification circuit 114 amplifies a voltage change detected by a detection impedance (not shown) connected to the low voltage side via the coupling capacitor 113 in a measurement band of 15 kHz to 150 kHz, and also applies the applied voltage measurement capacitors 110 and 111. The voltage at the connection point is full-wave rectified and converted to direct current.

  The A / D conversion circuit 115 converts the level of the signal amplified by the signal amplification circuit 114 into a digital signal and outputs the digital signal to the personal computer 200.

  Next, the operation of the partial discharge measuring apparatus 100 configured as described above will be described in association with processing performed by the personal computer 200 as shown in FIG. 5, for example.

  (S101) First, a test voltage pattern setting screen as shown in FIG. 6 is displayed on the display screen of the personal computer 200, for example.

  (S102) Subsequently, a user input operation is accepted, and when the user inputs a desired value on the setting screen, for example, a test voltage pattern that changes as shown in FIG. 7 can be instructed. The figure shows an example in which the AC voltage for measurement rises to 0 to 5 kV in 5 seconds, is maintained at 5 kV for 20 seconds, and drops to 5 to 0 kV in 15 seconds.

  (S103) Next, it is repeatedly determined whether or not the input operation has been completed, that is, for example, whether or not the OK button in the screen of FIG. 6 has been pressed, and if it is pressed, the process proceeds to (S104).

  (S104) The determination as to whether or not a measurement start instruction has been made on a measurement start instruction screen (not shown) is repeated, and when instructed, the process proceeds to (S105) and the measurement operation is started.

  (S105, S106) A voltage control signal for increasing the AC voltage for measurement from 0 to 5 kV in 10 seconds is output from the personal computer 200 to the partial discharge measuring apparatus 100. Specifically, for example, every 10/4095 seconds, data whose value increases by 1 from 0 to 4095 is output (S105). Further, it is determined whether or not the boost time specified by the user has elapsed (S106), and the output of the voltage control signal is repeated until the time has elapsed.

  The partial discharge measuring apparatus 100 generates a measurement AC voltage that increases by 5/4095 kV every 10/4095 seconds in accordance with the voltage control signal, and applies it to the specimen 300.

  More specifically, the voltage control circuit 103 outputs an alternating voltage that gradually increases in accordance with data output from the personal computer 200.

  The AC voltage output from the voltage control circuit 103 is pulse width modulated by the comparator 104a of the amplifier 104, amplified by the MOSFET 104b, and the amplified AC voltage is output via the low-pass filter 104c.

  The AC voltage output from the amplifier 104 is boosted by a factor of 100/24 by the first transformer 106, and further boosted by a factor of 5000/100 by the second transformer 107, and is supplied to the specimen 300 as an AC voltage for measurement. Applied.

  The discharge charge detected through the coupling capacitor 113 by applying the measurement AC voltage to the specimen 300 is amplified by the signal amplification circuit 114, and the voltage at the connection point of the applied voltage measurement capacitors 110 and 111 is: Similarly, full-wave rectification is performed by the signal amplification circuit 114, A / D conversion is performed by the A / D conversion circuit 115, and output to the personal computer 200.

  The personal computer 200 performs continuous measurement of partial discharge and applied voltage, determination of discharge start voltage, discharge extinction voltage, maximum discharge charge, and the like based on the measurement value input from the partial discharge measurement device 100. Specifically, for example, when a partial discharge does not occur as the voltage applied to the specimen 300 increases, for example, as shown in FIG. ) Or at the time of falling (solid line) does not increase from the noise level, but when partial discharge occurs, as shown in FIG. 8B, in the process of increasing the voltage (broken line) The discharge charge starts to increase from V1, and the discharge charge decreases from V2 to the noise level in the process of decreasing the voltage (solid line). Therefore, the applied voltage V1 when the discharge charge starts to increase is determined as the discharge start voltage, and the applied voltage V2 when the discharge charge is fully decreased is determined as the discharge extinction voltage.

  (S107) If it is determined in (S106) that the boost time specified by the user has elapsed, then it is repeatedly determined whether or not the holding time (20 seconds) of the applied voltage has elapsed. The process proceeds to (S108).

  (S108, S109) As in the above (S105, S106), a voltage control signal is output from the personal computer 200 to the partial discharge measuring apparatus 100, and the measurement AC voltage applied to the specimen 300 is 5 in 15 seconds. The voltage is lowered to ˜0 kV, and the discharge charge is measured in the same manner as described above.

  Note that the test voltage pattern is not limited to increasing and decreasing the voltage only once as described above, and may be set so as to change variously. Specifically, for example, the changed test voltage, arrival time, and holding time are set on the setting screen as shown in FIG. 9 displayed on the personal computer 200, and the test voltage changes as shown in FIG. A pattern may be designated. In addition, as shown in FIG. 9, for example, for convenience of setting operation, a check box for instructing whether to perform each step or skip may be provided. Further, the voltage change rate may be indicated instead of or together with the test voltage after the change, or the holding time may be omitted. Further, for example, it may be possible to instruct the control of the applied voltage in accordance with the applied voltage detected by the signal amplifying circuit 114 or a condition judgment based on a voltage change due to partial discharge. In this manner, by making it possible to arbitrarily control a complicated test pattern to which a plurality of step voltages are applied, it becomes possible to easily cope with various standard tests of electrical equipment.

  As described above, by using the amplifier 104 that amplifies the PWM signal, an AC voltage that is boosted by the first and second transformers 106 and 107 is generated, so that power consumption is greatly reduced, By increasing the amplification degree, the step-up ratio of the first and second transformers 106 and 107 can be kept small. In addition, the AC voltage generated by the amplifier 104 is once boosted by the first transformer 106 at a boost ratio at which the maximum effective voltage becomes the commercial power supply voltage, and then boosted by the second transformer 107 to measure AC. Since the voltage is generated, the step-up ratio of each of the first and second transformers 106 and 107 can be set to be smaller, and the design, manufacture, improvement of noise resistance, and the like are facilitated. In addition, as the second transformer 107, a voltage capable of boosting the commercial power supply voltage to the AC voltage for measurement can be used, so that a general-purpose transformer or the like can be easily applied, improving characteristics, reducing costs, etc. Can also be easily achieved.

  Conventionally, when an oscillator and an amplifier are used, noise is generated, and if this is used as a test power supply, a minute partial discharge signal to be measured is buried in the noise, which tends to make measurement impossible. On the other hand, it is possible to easily realize a test power supply device that can apply a low-noise test voltage.

  As described above, the present invention is useful as a partial discharge measuring device for measuring a partial discharge generated when a high voltage is applied to an insulator.

DESCRIPTION OF SYMBOLS 100 Partial discharge measuring device 101 Digital input / output circuit 102 Oscillation circuit 103 Voltage control circuit 103a D / A conversion circuit 103b Multiplication circuit 103c Amplifier 103d CR filter 104 Amplifier 104a Comparator 104b MOSFET
104c Low-pass filter 105 Power supply circuit for amplifier 105a Power transformer 105b Bridge rectifier circuit 105c Smoothing capacitor 106 First transformer 107 Second transformer 108 Noise elimination capacitor 109 Blocking coil 110/111 Applied voltage measurement capacitor 112 Calibration pulse generation circuit 113 Coupling capacitor 114 Signal amplification circuit 115 A / D conversion circuit 200 Personal computer 300 Specimen

Claims (8)

A power supply circuit for applying an AC voltage for measurement to the specimen;
A measuring unit for measuring a partial discharge generated in the specimen in a state in which the measurement AC voltage is applied;
A partial discharge measuring device comprising:
The power circuit is
An amplifier that amplifies a pulse width modulation signal in which an AC voltage is pulse width modulated, and outputs the amplified signal via a low-pass filter;
A first transformer that boosts the output of the amplifier and outputs an AC voltage whose maximum effective voltage is a commercial power supply voltage;
A second transformer that boosts the output of the first transformer and outputs an AC voltage for measurement;
A partial discharge measuring apparatus comprising: The partial discharge measuring device according to claim 1,
The amplifier includes a modulation circuit that performs pulse width modulation on an alternating voltage controlled to a predetermined voltage;
A switching element for amplifying the pulse width modulation signal;
A partial discharge measuring apparatus comprising: The partial discharge measuring device according to any one of claims 1 and 2,
The partial discharge measuring apparatus, wherein the carrier frequency of the pulse width modulation is set to a frequency different from a measurement band in the measuring unit. The partial discharge measuring device according to claim 3,
The partial discharge measuring apparatus, wherein a measurement band in the measurement unit is in a range of 15 kHz or more and 150 kHz or less, and a carrier frequency of the pulse width modulation is set to 400 kHz. The partial discharge measuring device according to any one of claims 1 to 4,
At least one of an LC filter, a noise removal capacitor, and a blocking coil is provided on at least one of the input side, the output side, and the output side of the second transformer. Partial discharge measuring device. The partial discharge measuring device according to any one of claims 1 to 5,
The measurement unit is configured to measure a voltage change that occurs when a partial discharge occurs in the specimen by a detection impedance connected to a low voltage side of the coupling capacitor. The partial discharge measuring device according to claim 6,
The measurement unit is further configured to measure a voltage actually applied to the specimen in conjunction with the measurement of the discharge charge. The partial discharge measuring device according to any one of claims 1 to 7,
A partial discharge measuring apparatus, characterized in that a calibration pulse generating circuit is connected to a terminal for applying the measurement AC voltage to the specimen.

Images