JPH11237430A - Partial discharge measurement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement accuracy in relation to a partial discharge measurement apparatus. SOLUTION: A desired sine wave voltage is generated at a power amplifier 2 and a transformer 3 from a sine wave of a sine wave oscillation part 1 an output voltage value of which is swept with an optional pattern, and impressed to a test object S. A current sent to the test object S because of the impression of the sine wave voltage is detected at a resistor R and integrated in an integration part of every period synchronous with a cycle of the sine wave. The integrated value is sample-held at a sample hold circuit 8 synchronously with the cycle of the sine wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measuring device, and more particularly to a partial discharge measuring device suitable for measuring the insulation performance of electronic parts and electronic materials.

[0002]

2. Description of the Related Art Safety in electrical and electronic equipment is largely maintained by insulation. Insulation is important for preventing accidents, and various test methods are defined by various safety standards (IEC standard, UL standard, Electrical Appliance and Material Control Law, etc.).

In the insulation resistance test, a DC voltage is applied to a test sample and a DC resistance value is calculated from a current value flowing through the test sample according to Ohm's law. Usually, 1 M ohm or more is measured. The insulation resistance test is performed to determine whether or not the insulation performance of the test object has deteriorated due to moisture absorption or the like. This is performed by applying a voltage.
Therefore, the deterioration (moisture absorption, etc.) of the insulating material can be inspected, but the gap (VOI) of the insulator is easily lost.
Inspection is not possible until D)).

[0004] The withstand voltage test is generally a test for applying a high alternating voltage to a specimen to confirm that the specimen is not damaged, and may be performed using a DC voltage. In the withstand voltage test, a large electric power of 500 VA is applied in order to cause dielectric breakdown of a defective product. The pass / fail test of the withstand voltage test is performed based on the presence or absence of breakage of the sample.The withstand voltage tester detects the leak current that flows when the sample breaks down, and determines whether or not the sample has been damaged. .

[0005] In other words, the withstand voltage test is in the form of "dielectric breakdown = increase in current". The withstand voltage test is a test that only makes a pass / fail decision as described above, and a specimen that fails in the test is often damaged and cannot be restored. Normally, the current detection method of a withstand voltage test object is an effective value detection or an average value detection, and a peak current is not detected. In addition, since a reactive current (also included in the leak current) flowing through the capacitance of the insulator cannot be separated, a small discharge current cannot be detected. Therefore,
A single discharge or a partial discharge cannot be detected, and even if a void or the like that causes insulation failure exists, it is determined to be non-defective if there is no breakdown (increase in current) in a withstand voltage test.

[0006] In this specification, a partial discharge refers to a discharge that partially bridges insulation between conductors, and does not include a discharge that completely bridges between conductors. Of the partial discharges, those that occur in the air around the conductor are called corona discharges.

[0007] As described above, the above-mentioned withstand voltage test causes damage to the specimen, and is not particularly suitable for insulation evaluation at the component level.

Therefore, JEC-0401 (Standards of the Institute of Electrical Engineers of Japan, Standards of the Institute of Electrical Engineers of Japan) specifies a partial discharge measurement for detecting a state before a specimen reaches dielectric breakdown.

FIGS. 5 to 7 are block diagrams of a conventional partial discharge measuring device defined in JEC-0401. FIG. 5 shows a basic circuit, FIG. 6 shows a measuring circuit using a bushing tap, and FIG. 7 shows a measuring circuit for a test object capable of inducing a voltage by itself.

In the circuit shown in each figure, an AC high voltage is applied to a test sample from a commercial power supply Vac to generate a partial discharge, and a minute voltage change of the pulse generated thereby is detected by an electric detection impedance Zd. The magnitude of the partial discharge can be measured by the measuring device M.

According to this partial discharge measurement, the state before the specimen reaches the dielectric breakdown is detected. Therefore, the potential defect that was not found in the withstand voltage test, the potential defect that could not be detected, or the manufacturing defect was detected. The above variation can also be detected. Specifically, it can detect defects nondestructively, can easily inspect defective parts, can easily analyze defects of unknown cause, and can easily optimize insulation design. In addition, the effect of partial discharge measurement is that it is possible to suppress variations that occur during manufacturing and that it is easy to find variations at the material level. It is effective in improving the quality.

[0012]

However, in the above conventional partial discharge measurement, it is necessary to further improve the measurement accuracy.
There is a need for easier measurements.

Accordingly, the present invention has been made in view of the above problems, and has as its object to provide a partial discharge measuring device which solves the above problems.

[0014]

According to the present invention, there is provided a partial discharge measuring apparatus for applying a high voltage to a specimen and measuring the insulation performance of the specimen. In, a sine wave oscillating means in which the output voltage value is swept by an arbitrary pattern, a desired sine wave voltage is generated from a sine wave from the sine wave oscillating means, and a voltage applying means for applying to the specimen, A current integrating means for detecting a current flowing through the specimen under application of the desired sine wave voltage and integrating the current at each period synchronized with a cycle of the sine wave; Sampling means for sampling and holding in synchronization with the cycle of the wave.

The device according to the second aspect of the present invention is the same as the first aspect.
And a voltage measuring means for measuring the applied desired sine wave voltage in synchronization with a cycle of the sine wave.

The device according to the third aspect of the present invention is the same as that of the second aspect.
, Further comprising an illustration means for illustrating a relationship between the value sampled and held by the sampling means and the measured voltage.

The device according to the fourth aspect of the present invention is the second aspect of the present invention.
(3) In (3), means for converting the value sampled and held by the sampling means into a digital value, storage means for storing the digital value, and arithmetic means for arbitrarily reading the digital value from the storage means and performing a predetermined operation Are further provided.

The device according to the fifth aspect of the present invention provides the device according to the fourth aspect.
, The arithmetic means calculates an average value of the values sampled and held by the sampling means.

The device according to the sixth aspect of the present invention is the same as that of the fourth aspect.
, The arithmetic means calculates the sum of the values sampled and held by the sampling means.

The device of the present invention according to claim 7 is the same as that of claim 4.
And a means for averaging the values sampled and held by the sampling means for a predetermined period.

The device of the present invention according to claim 8 is the device according to claim 4.
And a means for integrating a value sampled and held by said sampling means for a predetermined period.

The device according to the ninth aspect of the present invention is the first aspect of the present invention.
In any one of (8) to (8), the value sampled and held by the sampling means and a predetermined limit value set by the limit value setting means are compared by a comparator to determine pass / fail.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIGS. 1 and 2 are block diagrams showing a first embodiment of a partial discharge measuring device according to the present invention.

In FIG. 1, reference numeral 1 denotes a sine-wave oscillating unit having an oscillator therein, and oscillates and outputs a sine-wave voltage of a predetermined frequency with very little waveform distortion and stably. The output voltage value from the sine wave oscillating unit 1 is swept by an arbitrary voltage pattern set from the outside. The sine wave oscillator 1 also generates and outputs a timing pulse Tp synchronized with the frequency of the output sine wave.

The sine wave voltage from the sine wave oscillating section 1 is amplified by the power amplifier 2 and applied to the primary side of the transformer 3 to output a boosted voltage to the secondary side. This boosted output is the desired high voltage (eg, up to 1440
V), the gain of the power amplifier 2 and the transformer 3
Is determined. The secondary high voltage output of the transformer 3 is connected to one end of the impedance element Z, and the capacitance C is connected between the secondary low voltage output and the other end of the impedance element Z. The common connection point of the impedance element Z and the capacitance C is connected to the high-voltage test electrode 4a to which one electrode of the specimen S is connected, and to the low-voltage test electrode 4b to which the other electrode of the specimen S is connected. A current detection resistor R (may be impedance Z) is connected between the secondary low-voltage outputs of the transformer 3.

Here, the partial discharge measurement will be briefly described.

In the partial discharge measurement, the measurement is performed with the sample sandwiched between two electrodes, but the sample can be replaced with an equivalent circuit of a capacitor and a resistor. When the specimen has a non-uniform and non-uniform portion of the material due to, for example, an internal void or a defect, the capacitor of the equivalent circuit is regarded as a series-parallel connection of various capacitors.

Usually, the gap inside the specimen is made of a gas such as air, and its size is very small, so that the capacitance of the capacitor is small. When an AC voltage is applied to the electrodes at both ends of a test sample having a gap, a larger voltage is applied to a gap having a smaller capacitance.

Discharge is performed at a relatively low voltage in the gap with a small insulation distance. Even if a discharge occurs in the gap, there is no insulation that short-circuits between the electrodes because of the presence of the entire insulator. As the deterioration of the specimen progresses, the gap increases, and eventually, dielectric breakdown affecting the entire specimen may be reached. The above-mentioned state in which discharge does not lead to short-circuiting between electrodes even if discharge occurs in the gap is partial discharge, and a test for detecting movement of electric charge when partial discharge occurs is a partial discharge test.

In this embodiment, a desired high voltage is applied to the specimen S at a predetermined frequency by the configuration shown in FIG. 1, and at this time, a current flowing through the specimen S is detected by the resistor R to obtain a charge. I made it. This makes it possible to measure the applied voltage and the movement of the charge when the voltage is applied.

The high-pass filter 5 extracts a wide-range component from the current detected by the resistor R, and the rectifier circuit 6 performs half-wave rectification. The rectified output is input to the integrator 7, and the integration is repeated without interruption (at the same frequency) for each period synchronized with the frequency of the sine wave from the sine wave oscillator 1.

That is, the integrator 7 outputs the timing pulse T
The reset switch S1 is switched by p, and a well-known integrating circuit 7a including an operational amplifier OP and an integrating capacitor C1. The electric charge charged in the capacitor C1 is discharged by the reset switch S1 every period described above. ing. The integrated value of the DC voltage obtained by the integration unit 7 is input to the sample hold circuit 8, and is held in the sampling capacitor C2 at the switching timing of the sampling switch S2 operated by the timing pulse Tp for each period described above. This integral value represents the charge in the gap of the sample S.

On the other hand, a voltage measuring section 9 is connected to the test electrodes 4a and 4b to measure the voltage applied to the specimen S. The timing pulse Tp is input to the voltage measuring section 9 and the sine wave oscillating section 1 is reset in the same manner as the reset of the integral value.
The voltage measurement is performed without interruption every period (at the same frequency) synchronized with the frequency of the sine wave from.

The voltage measurement result and the integrated value held in the sampling capacitor C2 are converted into digital data via the A / D board 20 or the like as shown in FIG. And the relationship between the two is displayed in a graph, and an arithmetic operation can be performed on the measurement result.

The measurement result display unit 25 includes a display device having a display screen such as a liquid crystal display, a CRT display, and a plasma display;
Any configuration may be used as long as it has a memory for storing input data and an arithmetic unit for performing arithmetic processing on the input data, and can be realized by a personal computer.

In FIG. 2, the A / D board 20
Digital data obtained by A / D-converting the input data by the D converters 21 and 22 is temporarily stored in the RAM 26,
The data is read out as needed by U27, subjected to data processing for graph display, and displayed on the display screen of the display device 28 together with the measured values. The A / D converters 21 and 22 receive the timing pulse TP and receive the sine wave oscillator 1 shown in FIG.
A / D conversion is performed for each period synchronized with the frequency of the sine wave from.

The above-described sine wave voltage variable pattern of the sine wave oscillator 1 can be set and swept by the CPU 27.

FIG. 3 shows an example of a display screen of the measurement result display section 25 in the present embodiment, wherein a curve A represents an integrated value (charge) and a curve B represents a voltage. The horizontal axis represents the sweep time of the sine wave, and the vertical axis represents the charge amount and the voltage value. However, the measured values of the voltage are shown along the horizontal axis for convenience of display. Although the voltage variable pattern in FIG. 3 is trapezoidal, it may be a pattern in which two trapezoids having different constant values of voltage are combined, or a pattern in which the constant value of voltage changes in a stepwise manner. Settings can be made.

As described above, since both measurement results are simultaneously displayed on the display screen of the measurement result display section 25 so as to clarify the relationship between the charge and the voltage, the state of the specimen in the partial discharge test can be easily determined. You can figure out. In addition, the amount of mobile charge is obtained by integrating the current flowing through the specimen, and the integrated value is reset and sampled and held in each cycle in synchronism with the frequency of the test sine wave, and the partial discharge charge is calculated. Since the amount is measured, a stable measurement result can always be obtained irrespective of the frequency of the sine wave, and a partial discharge test with good reproducibility can be performed. Furthermore, integration reset and sample hold are performed for all periods of the sine wave, and all digital data of the sample hold result is stored in the memory, so measurement can be performed without overlooking the partial discharge phenomenon that occurs randomly. it can.

(Other Embodiments) In the above embodiment, the voltage and the charge of the specimen are measured. However, if the voltage at both ends of the resistor R is detected and converted into a current, The leakage current flowing through the test sample can be measured. The measurement of the leakage current is also performed at intervals synchronized with the frequency of the sine wave from the sine wave oscillating unit 1 by using the timing pulse Tp in the same manner as the reset of the integrated value and the sample hold, and the measurement result display unit 25 Curve A as curve C on the display screen,
An example displayed together with B is also shown in FIG.

Further, by reading the digital data in the RAM 26 and performing an arithmetic operation such as a moving average process by the CPU 27, it is easy to grasp the tendency of the occurrence of the partial discharge. If the sum of the sampled charge amounts is calculated by the CPU 27, the total charge amount can be obtained.

The total charge can also be obtained by a hardware configuration without using the arithmetic processing. An integration circuit is provided between the output of the sample and hold circuit 8 in FIG. 1 and the A / D board 20 in FIG. 2 for integration. Can be obtained by: Further, the output of the sample and hold circuit 8 of FIG.
By providing a low-pass filter (not shown) between the D boards 20 and inputting it to the measurement result display unit 25, it is possible to display the average value of the randomly generated partial discharges.

Further, in the above description, a case has been described in which a voltage is applied to facilitate the measurement and observation of the mobile charge and the applied voltage itself when a partial discharge phenomenon occurs. By doing so, it can also be used when making a pass / fail decision on a specimen based on a predetermined limit value.

In FIG. 4, reference numeral 40 denotes a register for setting a limit value, and reference numeral 41 denotes a digital comparator for comparing the output of the sample hold circuit 8 with the limit value, and transfers the comparison result to the CPU 27. The register 40 can variably set an arbitrary value based on an experiment result or the like.

An analog circuit using an analog comparator instead of the digital comparator 41 may be provided by setting a limit value by providing a voltage source or the like capable of changing the voltage in place of the register 40. This is also effective in the case where a low-pass filter or an integrating circuit is added to the output of the circuit 8.

[0047]

As described above, according to the present invention, a desired sine wave voltage is generated from a sine wave swept by an arbitrary pattern and applied to the sample by applying the output voltage value to the sample. Detects the flowing current and integrates the value obtained by integrating every period synchronized with the sine wave cycle.The integrated value is sampled and held in synchronization with the sine wave cycle. Thus, there is an effect that the measurement of the partial discharge can be more easily performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a partial discharge measuring device according to the present invention.

FIG. 2 is a block diagram showing a first embodiment of the partial discharge measuring device according to the present invention.

FIG. 3 is an explanatory view showing an example of a display screen of a measurement result display section of the partial discharge measurement device according to the present invention.

FIG. 4 is a block diagram showing a part of another embodiment of the partial discharge measuring device according to the present invention.

FIG. 5 is a block diagram of an example of a conventional partial discharge measuring device.

FIG. 6 is a block diagram of an example of a conventional partial discharge measuring device.

FIG. 7 is a block diagram of an example of a conventional partial discharge measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sine wave oscillation part 2 Power amplifier 3 Transformer 4a, 4b Test electrode 5 High pass filter 6 Rectifier circuit 7 Integrator 7a Integration circuit 8 Sample hold circuit 9 Voltage measurement part 20 A / D board 21, 22 A / D converter 25 Measurement result Display unit 26 RAM 27 CPU 28 Display device S1 Reset switch S Sample

Claims (9)

[Claims] 1. A partial discharge measuring device for applying a high voltage to a specimen to measure the insulation performance of the specimen, comprising: a sine wave oscillating means for sweeping an output voltage value in an arbitrary pattern; Generating a desired sine wave voltage from a sine wave from the wave oscillating means, applying a voltage to the sample, and detecting a current flowing through the sample by applying the desired sine wave voltage; Current integration means for integrating every period synchronized with the cycle of the sine wave; and sampling means for sampling and holding the integrated value obtained by the current integration means in synchronization with the cycle of the sine wave. Partial discharge measurement device. 2. The partial discharge measuring device according to claim 1, further comprising voltage measuring means for measuring the applied desired sine wave voltage in synchronization with a cycle of the sine wave. 3. The partial discharge measuring device according to claim 2, further comprising an illustration unit that illustrates a relationship between a value sampled and held by the sampling unit and the measured voltage. 4. A means for converting a value sampled and held by the sampling means into a digital value, a storage means for storing the digital value, and an operation for arbitrarily reading the digital value from the storage means and performing a predetermined operation The partial discharge measuring device according to claim 2, further comprising a unit. 5. The partial discharge measuring device according to claim 4, wherein the arithmetic unit calculates an average value of values sampled and held by the sampling unit. 6. The partial discharge measuring device according to claim 4, wherein the calculating means calculates a sum of values sampled and held by the sampling means. 7. The partial discharge measuring device according to claim 4, further comprising: means for averaging values sampled and held by said sampling means for a predetermined period. 8. The partial discharge measuring apparatus according to claim 4, further comprising means for integrating a value sampled and held by said sampling means for a predetermined period. 9. The apparatus according to claim 1, wherein the value sampled and held by said sampling means is compared with a predetermined limit value set by said limit value setting means by a comparator to determine whether or not the result is acceptable. The partial discharge measuring device as described in the above.