JPH10282181A - Void-detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a void-detecting apparatus of high insulation performance and high reliability. SOLUTION: In the void-detecting apparatus, a commercial frequency is added from a commercial frequency power source 1. A magnetic flux of a core (iron core) of a saturable reactor 2 is changed in accordance with a change of a time-integrated voltage. The core is saturated when the magnetic flux exceeds a predetermined value, whereby an inductance of the saturable reactor 2 is decreased to charge a charging capacitor 3. As a result, a pulse voltage appears at both ends of the charging capacitor 3. The pulse voltage is pumped in accordance with a turns ratio of a transformer 4 and impressed to a coupling capacitor 5 and a sample device 6. A void present in the sample device 6 is detected in this manner. Operation safety of the void-detecting apparatus is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a void detecting device for detecting a void existing in an insulating component of a high-voltage device formed of a polymer resin such as epoxy resin or brimix.

[0002]

2. Description of the Related Art In conventional electric equipment, electrical insulation between the ground and between phases is performed by gas, liquid, solid or the like. In power equipment, a large number of epoxy resins are used as insulation using solids (solid insulation). Insulators using epoxy resin as an insulating material include insulating spacers (inserts) that support the bus bars of GIS (gas insulated switchgear), PTs (instrument transformers),
Insulation of a CT (current transformer), a stator winding of a rotating machine, and the like are included. In these electric devices, the epoxy resin is filled between the high-voltage part and the ground or between different high-voltage parts and solidified to provide insulation performance and a function of mechanically supporting the high-voltage part.

[0003] Since the epoxy resin is a thermoplastic material, a liquid material is poured into a predetermined mold and exposed to high temperature to be fixed (casting). During the casting operation, there may be a part where air bubbles or resin are not filled, and such a part is generally called a void. In such a solid-insulated high-voltage device including a void, the electric field in the void portion increases during application of power, and discharge may occur in the void portion. Then, the epoxy resin around the voids is carbonized due to the generation of electric discharge, and a tree (tree-like crack) develops in the epoxy resin, which may cause dielectric breakdown.

There is an ultrasonic flaw detection method as a method for detecting such voids. This method is often used as a nondestructive method for inspecting cracks inside metal. It is an excellent detection method when different media exist in the same medium, but in order to increase the detection accuracy in order to detect voids in the area where metal and solid insulator are combined like high voltage equipment There is a problem that it takes time.

As another method, there is a method of detecting a discharge sound when a discharge is generated in a void. The AE (audio / echo) sensor is attached to the high-voltage equipment, and the presence or absence of discharge is confirmed by detecting the sound of particles charged by void discharge colliding with the surface of the insulator. By attaching a plurality of AE sensors and measuring the magnitude and time difference of the sensor output, it is possible to specify the location where the void discharge has occurred. However, since the method detects a small signal, it is susceptible to noise and cannot detect a small void discharge.

As another method, there is a method of detecting a discharge pulse generated by a discharge generated in a void. This is a method that has been used for a long time as a method for detecting the occurrence of partial discharge in high-voltage equipment. This is a method of detecting a pulse current flowing in a circuit due to discharge. Since a sensor for detecting a high-frequency pulse current is installed outside the specimen, it is difficult to distinguish the partial discharge from the void discharge when the partial discharge occurs on a surface other than the void, such as on a surface. Further, since the partial discharge itself is a small signal, it is easily affected by external noise, and it becomes difficult to detect a minute discharge.

[0007]

As for voids in a solid insulator formed by casting a thermoplastic material, the temperature inside the void at the time of casting depends on the temperature of the surrounding insulator.
At the time of casting, the resin is kept at a high temperature to solidify it.However, as the resin solidifies and is released from the mold as time elapses, and as the temperature of the insulator reaches the ambient air temperature, the inside of the void is The temperature also becomes the temperature of the atmosphere.

However, since the periphery of the void is covered with a resin and shielded from the atmosphere, when the temperature inside the void changes from a high temperature to the atmospheric temperature, the pressure inside the void becomes negative as compared with the atmospheric pressure. The discharge voltage of the void in such a negative pressure state becomes lower than the discharge voltage in the atmosphere, and as a result, the pulse current generated by the discharge becomes smaller, making it difficult to detect from the outside.

It is an object of the present invention to provide a high-voltage apparatus having excellent insulation performance by detecting the presence of the above-described void of a negative pressure.

[0010]

According to a first aspect of the present invention, there is provided a void detecting apparatus, comprising: a transformer connected to an AC power supply for transforming an applied AC voltage; and a transformer connected in series to the transformer and applied to the transformer. A saturable reactor that adjusts the waveform of the AC voltage to be supplied, a charging capacitor that is connected in parallel to the power supply side of the transformer and supplies a pulse current, a coupling capacitor that is connected in parallel to the load side of the transformer, and this coupling. A pulse detector that is connected in series with the capacitor and detects a pulse current flowing through the DUT via the coupling capacitor, and a void that detects a void present in the DUT based on a pulse output signal output from the pulse detector And a detection circuit.

A void detector according to a second aspect of the present invention includes a second pulse detector that is connected in series with the DUT and detects a pulse current flowing through the DUT via the coupling capacitor.
It is characterized by having a void detection circuit connected to the first and second pulse detectors and operated by the sum of the two pulse currents.

A void detecting device according to a third aspect of the present invention includes a transformer connected to a variable voltage variable frequency power supply for transforming an applied AC voltage, a coupling capacitor connected in parallel to a load side of the transformer, and A pulse detector is connected to the coupling capacitor and detects a pulse current flowing through the DUT, and a void present in the DUT is detected by a pulse output signal output from the pulse detector.

According to a fourth aspect of the present invention, there is provided a void detecting device which is applied around an insulating spacer which insulates and supports a high voltage conductor which is a charged part of a test sample from a ground side, and an insulator coated on the high voltage conductor. And a detection electrode attached in contact with the high-resistance conductive layer.

A void detecting device according to a fifth aspect is characterized in that a pulse detector is connected in series with the detecting electrode.

A void detection device according to a sixth aspect of the present invention includes a DC power supply that is connected in series with a resistor to form a series circuit and supplies a DC voltage, a high-speed switch that short-circuits the DC power supply,
A ladder circuit connected to a high-speed switch composed of a capacitor and a reactor connected in a ladder stage, a pulse detector connected to the ladder stage circuit to detect a pulse current flowing through the DUT, and an output from the pulse detector And a void detection circuit for detecting a void present in the test sample in accordance with the pulse output signal.

A void detection device according to a seventh aspect of the present invention is a DC power supply comprising a DC power supply connected in series with a resistor to form a series circuit and supplying a DC voltage, and a capacitor and a reactor connected in a ladder stage. Connected to the ladder stage circuit,
A transformer connected to the ladder stage circuit, a high-speed switch connected between the ladder stage circuit and the transformer to interrupt the voltage applied to the transformer, and a coupling capacitor connected in parallel to the load side of the transformer A pulse detector that is connected to the coupling capacitor and detects a pulse current flowing through the sample, a void detection circuit that detects a void present in the sample by a pulse output signal output from the pulse detector, It is characterized by having.

The void detecting device according to claim 8 is characterized in that the high-speed switch is a saturable reactor.

According to the present invention, a high frequency power supply or a PFN is used for a voltage source circuit for applying a test device for a partial discharge test.
A circuit and a magnetic switch circuit were provided, and electrodes and sensors were installed near the area where voids were expected.

Then, the voltage dv /
By increasing dt (change in voltage per unit time), dv / dt of the voltage shared in the void portion was increased, the discharge delay generated in the void portion was increased, and the discharge voltage was increased. In addition, the pulse current generated in the void portion is caused to flow through a circuit having a small loss to perform local detection.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the void detecting device according to the present invention will be described.

FIG. 1 shows an embodiment of a void detecting device according to the present invention. The transformer 4 is connected to a commercial frequency power supply 1 and transforms an applied AC voltage. The transformer 4 is connected in series to the transformer 4. A saturable reactor 2 connected to adjust the waveform of an AC voltage applied to the transformer 4 and a charging capacitor 3 connected in parallel to a power supply side of the transformer 4 and supplying a pulse current.
A coupling capacitor 5 connected in parallel to the load side of the transformer 4, a pulse detector 7 connected in series with the coupling capacitor 5 and detecting a pulse current flowing through the DUT via the coupling capacitor 5, A void detection circuit 50 for detecting voids present in the test sample based on a pulse output signal output from the pulse detector 7.

That is, a closed circuit is formed in which the saturable reactor 2 and the charging capacitor 3 are connected in series with the commercial frequency power supply 1. The primary winding (low-voltage winding) of the transformer 4 is connected in parallel with the charging capacitor 3. To the secondary winding (high-voltage winding) of the transformer 4, a coupling capacitor 5 and a high-voltage device having a solid insulation, which is a test device 6, are connected in parallel.

FIG. 2 shows an embodiment of the void detecting device according to the second aspect, which detects a pulse current which is connected in series with the sample 6 and flows through the sample 6 via the coupling capacitor 5. And a void detection circuit 50 connected to the pulse detectors 7 and 8 and operated by the sum of the two pulse currents.

That is, the pulse detector 7 was installed on the ground lead of the coupling capacitor 5, and the pulse detector 8 was installed on the ground lead of the test device 6.

FIG. 3 shows an embodiment of the void detecting device according to the third aspect of the present invention.
Variable voltage variable frequency (VVVF; Variable V)
ol-tage and Variable Frequency) Install the power supply 9,
A transformer 4 connected to the VVVF power supply 9 for transforming the applied AC voltage, a coupling capacitor 5 connected in parallel to the load side of the transformer 4, and a pulse connected to the coupling capacitor 5 and flowing to the DUT 6 A pulse detector 7 for detecting a current;
A void detection circuit 5 for detecting a void existing in the specimen 7 based on a pulse output signal output from the pulse detector 7
0. That is, the VVVF power supply 9 is connected to the primary terminal of the transformer 4, and the secondary winding (high-voltage winding) of the transformer 4
Are connected in parallel to a coupling capacitor 5 and a high voltage device having a solid insulation, which is a test device 6, respectively. FIG. 4 is a circuit diagram of the commercial frequency power supply 1 shown in FIG.
And

FIG. 5 shows an embodiment of the void detecting device according to the present invention, in which an insulating spacer 12 for supporting a high voltage conductor 10 which is a charged part of a test sample insulated from a ground side.
And a high-resistance conductive layer 13 applied around an insulator 11 covered by the high-voltage conductor 10, and a detection electrode 14 attached in contact with the high-resistance conductive layer 13. The insulating spacer 12 for fixing the position of the high-voltage conductor 10 in the casting mold on the surface of the high-voltage conductor 10 which is thus subjected to a high voltage.
Is disposed in a region at a height from the surface of the high-voltage conductor 10 to the height of the insulating spacer 12.
A high-resistance conductive layer 13 formed by applying a high-resistance paint to the surface formed of the insulating material 11 and the ground electrode 14 is attached to the surface of the high-resistance conductive layer 13 facing the insulating spacer 12. I have.

FIG. 6 shows an embodiment of the void detecting device according to claim 5, in which pulse detectors 7 and 8 are connected in series with the detecting electrode 14 via lead wires 16 and 16a. . That is, a pair of insulating spacers 12 that support the high-voltage conductor 10 in the middle of the high-voltage conductor 10 during casting are vertically arranged,
An insulator 11 is filled around the insulating spacer 12 and the high-voltage conductor 10, and a high-resistance conductive layer 13 is formed on the upper and lower surfaces of the insulating spacer 12 and the insulator 11. A ground electrode 14 is formed on the surface of the high-resistance conductive layer 13. The pulse detectors 7 and 8 were installed on each lead wire 16 connected from the ground electrode 14 to the ground electrode. An output of a test voltage 17 is connected to the high-voltage conductor 10, the high-resistance conductive layer 13 is grounded by a lead 16, and pulse detectors 7 and 8 are connected to the lead 16a.

FIG. 7 shows an embodiment of the void detecting device according to claim 6, wherein the power supply 21 is connected in series with the resistor 23 to form a series circuit and supplies a DC voltage, and is connected to the series circuit. And a high-speed switch 24 alternately short-circuiting the series circuit to use as an AC power supply, a capacitor C and a reactor L
A ladder stage circuit 25 configured to be connected in a ladder stage shape and connected to a high-speed switch 24 to shape an AC voltage; a pulse detector 7 connected to the ladder stage circuit 25 and detecting a pulse current flowing through the DUT 6; A void detection circuit 50 for detecting voids present in the test sample based on a pulse output signal output from the pulse detector 7.

That is, a DC power supply 21 connected in series with a resistor 23 to supply DC power and a high-speed switch 24 such as a semiconductor switch or a thyratron are connected in parallel.
A ladder stage circuit 25 including a reactor L and a capacitor C is connected in series with these circuits, and the sample 6 and the pulse detector 7 are connected in series to the other end of the ladder stage circuit 25.

FIG. 8 shows an embodiment of a void detecting device according to claim 7, wherein a DC power supply 21 is connected in series with a resistor 23 to form a series circuit and supplies a DC voltage;
A ladder stage circuit 25 configured by connecting the capacitor C and the reactor L in a ladder stage configuration and connected to the first series circuit and the second series circuit to form an AC voltage; and an AC voltage connected to the ladder stage circuit 25 and applied thereto. A transformer 4 for transforming, a high-speed switch 24 connected between the series circuit and the transformer 4 for interrupting an AC voltage applied to the transformer 4, and a coupling connected in parallel to the load side of the transformer 4; A capacitor 5, a pulse detector 7 connected to the coupling capacitor 5 for detecting a pulse current flowing through the sample 6, and a void for detecting a void existing in the sample based on a pulse output signal output from the pulse detector 7. And a detection circuit 50.

That is, a DC power supply 21 connected in series with the resistor 23 and supplying a DC voltage, and a high-speed switch 24 composed of, for example, a semiconductor switch or a thyratron, are connected, and a ladder stage composed of a reactor L and a capacitor C is connected in series with this circuit. The circuit 25 is connected, the primary winding of the transformer 4 is connected to the other end of the ladder stage circuit 25, and the coupling capacitor 5 and the sample 6 are connected in parallel to the secondary winding of the transformer 4. .

FIG. 9 shows an embodiment of the void detecting device according to the eighth aspect, in which the high-speed switch 2 shown in FIG.
4 was designated as a saturable reactor 24a.

A DC power supply 21 connected in series with the resistor 23b and a DC power supply 21 connected in series with the resistor 23b to form a series circuit and supply a DC voltage;
A ladder stage circuit 25 configured by connecting the capacitor C and the reactor L in a ladder stage configuration and connected to the first series circuit and the second series circuit to form an AC voltage; and an AC voltage connected to the ladder stage circuit 25 and applied thereto. A transformer 4 for transforming, a high-speed switch 24 connected between the series circuit and the transformer 4 for interrupting an AC voltage applied to the transformer 4, and a coupling connected in parallel to the load side of the transformer 4; A capacitor 5, a pulse detector 7 connected to the coupling capacitor 5 for detecting a pulse current flowing through the sample 6, and a void for detecting a void existing in the sample based on a pulse output signal output from the pulse detector 7. And a detection circuit 50.

That is, a DC power supply 21 connected in series with a resistor 23 and supplying a DC voltage, and a high-speed switch 24 composed of, for example, a semiconductor switch or a thyratron, are connected, and a ladder stage composed of a reactor L and a capacitor C is connected in series with this circuit. The circuit 25 is connected, the primary winding of the transformer 4 is connected to the other end of the ladder stage circuit 25, and the coupling capacitor 5 and the sample 6 are connected in parallel to the secondary winding of the transformer 4. .

FIG. 9 shows an embodiment of the void detecting device according to claim 8, wherein the high-speed switch 2 shown in FIG.
4 was designated as a saturable reactor 24a.

That is, the DC power supply 21 connected in series with the resistor 23 is short-circuited by the saturable reactor 24a. Further, one end of a ladder stage circuit (PFN circuit) 25 composed of a reactor L and a capacitor C is connected to the output of these DC power supply circuits, and a test device 6 is connected to the other end of the ladder stage circuit 25 to be tested. A pulse detector 7 is provided at the ground side end of the detector 6.

Next, the operation of the embodiment will be described.

The void detecting device according to the first embodiment is shown in FIG.
When a commercial frequency is applied from the commercial frequency power supply 1, the magnetic flux of the core (iron core) of the saturable reactor 2 changes according to the change of the voltage over time. When the magnetic flux exceeds a predetermined value, the core is saturated, the inductance of the saturable reactor 2 is reduced, the charging capacitor 3 is charged, and a pulse voltage appears at both ends of the charging capacitor 3. This pulse voltage is boosted according to the winding ratio of the transformer 4 and applied to the coupling capacitor 5 and the test device 6. This process is illustrated in FIG.
The output voltage 40a of the commercial frequency power supply 1, the voltage 40b between the terminals of the charging capacitor 3, and the secondary winding voltage 40c of the transformer 4 are shown.

The void detecting device according to the second aspect is shown in FIG.
, When a partial discharge occurs inside the test sample 6, the pulse current Ip shown in FIG. 11 flows from the coupling capacitor 5 to the test device 6 due to the voltage change at that time, and at this time, the secondary winding of the transformer 4 Hardly flows to On the other hand, the current flowing due to the intrusion of the external noise is divided into the pulse current In and the coupling capacitor 5 and the tester 6.

Looking at these currents, the current flowing in the partial discharge of the test device 6 has the opposite polarity between the pulse detectors 7 and 8, but in the case of external noise, the pulse detectors 7 and 8
It can be seen that the polarities are the same between. From this, as shown in FIG. 11, the polarity of the pulse signals P7 and P8 output from the pulse detectors 7 and 8 is determined by the polarity determination circuit 12A, and the pulse signal P9 and the switch operation signal R are output.
The pulse signal P9 is delayed by the delay circuit 12B, and when the pulse signals P7 and P8 are signals of the same polarity, the signal input to the pulse detection circuit 12D is interrupted for a short time via the switch circuit 12C.

That is, as shown in FIG. 12, when an external noise is applied to the circuit to which the applied voltage V is applied, the current I ₇ of the pulse detector ₇ and the current I ₇ of the pulse detector 8 are changed.
₈ indicates the same vector direction, and the synthesized pulse current In
Appears as shown.

However, in the case of partial discharge, the current I ₇ of the pulse detector ₇ and the current I ₈ of the pulse detector 8 show opposite vector directions, and the combined pulse current In does not appear as shown in the figure.

The void detecting device according to the third aspect is shown in FIG.
, A VVVF power supply 9 is connected to the primary winding of the transformer 4 to apply a high-frequency voltage to the coupling capacitor 5 and the test device 6 to perform a partial discharge test.

FIG. 5 shows a void detecting device according to a fourth embodiment.
In this case, if the insulating spacer 12 is present at the time of casting the insulator 11, voids are easily trapped at the interface of the insulating spacer 12. In the partial discharge test, a voltage is applied between the high-voltage conductor 10 and the high-resistance conductive layer 13 to detect a pulse current due to the partial discharge. The equivalent circuit at this time is shown in FIG.

The capacitance Ci of the portion of the insulator 11 corresponding to the void, the capacitance Cv of the void portion,
A series circuit of a resistor Rc of the high-resistance conductive layer 13,
When partial discharge occurs, a switch Sw in parallel with the capacitance Cv is turned on, and the capacitance Cv is short-circuited. Accordingly, the pulse current peak value Ipp at the time of discharge is determined by the shared voltage Vg of the capacitance Cv immediately before the discharge and the resistance Rc of the high-resistance conductive layer 13, and the pulse current peak value Ipp = shared voltage Vg / resistance Rc. ... (1)

If the insulating spacer 12 in which the void is trapped and the grounding lead wire mounting position of the high resistance conductive layer 13 are far apart, the resistance Rc shown in FIG. 13 becomes large, and the pulse is evident from the equation (1). The current peak value Ipp becomes small and detection becomes difficult.

Here, as shown in FIG.
When the ground electrode 14 is provided near the ground electrode 2 and the current flowing through the ground electrode 14 is detected, the equivalent circuit of FIG. 13 shows that the resistance Rc has become extremely small. Larger and easier to detect.

FIG. 14 is a circuit diagram showing a circuit in which a capacitor is turned on as shown in FIG. Then, as shown in FIG. 15, a rectangular wave 15A is output. The vibration wave is gradually attenuated due to the small resistance in the actual circuit. However, if the measurement is performed in the first part, the purpose of the corona discharge can be achieved because the voltage attenuation is small. FIG. 16 shows an example of an actual measurement result, and each of the curves 16A corresponds to the test equipment 2
6B, the final stage voltage applied to 6; 16B is the intermediate stage voltage;
C indicates the first stage voltage.

FIG. 6 shows a void detecting device according to a fifth embodiment.
In this case, a plurality of insulating spacers 12 are included, and a ground electrode 14 is attached to each of the spacers.
The pulse detector 7 is installed on the ground lead from each ground electrode 14. Thereby, it is possible to specify which part of the insulating spacer 12 has a void in which the partial discharge occurs.

FIG. 7 shows a void detecting device according to the sixth embodiment.
, The ladder stage circuit 25 is charged by the DC power supply 21 via the resistor 23, and the high-speed switch 24 is turned on after the charging is completed. Then, after the electric charge stored in the ladder stage circuit 25 is completely discharged, the high-speed switch 24 is opened. Next, the ladder stage circuit 25 is charged by the DC power supply 23 via the resistor 23, and after the charging is completed, the high-speed switch 24 is turned on. After the electric charge stored in the ladder stage circuit 25 is completely discharged, the high-speed switch 24 is opened. By repeating these positive and negative voltage charging and turning on and off the high-speed switch 24, positive and negative voltages are repeatedly applied to the test device 6. In FIG. 8, the void detection device applies a higher voltage to the DUT 26 by boosting the positive and negative repetitive voltages appearing at the output terminal of the ladder stage circuit 25 with the transformer 4.

FIG. 9 shows a void detecting device according to the eighth embodiment.
7 is a circuit in which the high-speed switch 24 shown in FIG. 7 is replaced by a saturable reactor 24a. The ladder stage circuit 25 is charged from the DC power supply 21, the magnetic flux of the saturable reactor 24a also increases as the voltage increases, and when the value reaches a predetermined value, the core of the saturable reactor 24a is saturated, and the impedance of the saturable reactor 24a is increased. Becomes smaller.

Next, effects of the embodiment will be described.

As for the effect of the void detecting device according to the first aspect, it has been found by Versien that the discharge voltage of the gas changes depending on the gab length and the pressure of the gas. FIG. 17 shows an example of investigating this. . If this example is applied to a void, the lower the pressure in the void, the lower the discharge voltage.

The partial discharge in the void is considered as shown in FIG. 18. Discharge and extinction are repeated in the void, and the discharge voltage Vg at this time becomes a discharge pulse current and is detected by an external pulse detector. If the pressure inside the void is low, the discharge voltage Vg decreases as shown in FIG. 17, the discharge pulse current value that can be detected outside decreases, and if the output of the pulse detector drops to the noise level, detection becomes impossible.

On the other hand, in the gas discharge, the flash voltage at which the voltage change dv / dt per unit time of the applied voltage increases as shown in FIG. From this, the discharge pulse which becomes negative pressure and the discharge voltage of the void decreases and cannot be detected by the normal partial discharge test is calculated by the circuit of FIG.
By increasing v / dt, the discharge voltage inside the void is increased, and it becomes possible to detect the discharge voltage with a pulse detector.

The effect of the void detecting device according to the second aspect is that, as already described with reference to FIG. 11, when the output signals of the pulse detectors 7 and 8 have the same polarity, they are erroneous signals due to external noise. Then, the polarity discrimination circuit 12A detects this, and the delay (delay) circuit 12B interrupts the signal input to the detection circuit with a delay by the switch circuit 12C.

The effect of the void detecting device according to the third aspect is that a high dv / d
Instead of generating a test voltage of dt, a VVVF power supply can generate a high-frequency voltage having the same dv / dt.

The effects of the void detecting device according to the fourth and fifth aspects have already been described in the description of the operation.

The effect of the void detecting device according to the sixth aspect is that when the high-speed switch 22 is turned on to the charged ladder stage circuit 25, a rectangular-wave-shaped pulse voltage is generated.
Is applied with a high dv / dt voltage. By repeating charging and discharging of the positive power supply and the negative power supply, an alternating voltage of a rectangular wave is applied to the test device 6. The effect is the same as the first aspect.

The effect of the void detecting device according to the present invention is that the rectangular wave voltage generated at the end of the ladder stage circuit is transformed by the transformer 4.
And a high test voltage is applied to the test device 26. The effect is the same as the first aspect.

The effect of the void detecting device according to the present invention is characterized in that a supersaturated reactor 24a is used in place of the high-speed switch, and the ladder stage circuit 25 is charged with a DC power supply, and the supersaturation occurs in the process of increasing the voltage. Reactor 24a
When the magnetic flux of the saturable reactor 24a reaches a predetermined value, the core of the saturable reactor 24a is saturated, the inductance of the saturable reactor 24a decreases, and the electric charge stored in the ladder stage circuit 25 is discharged. /
A square wave voltage with dt appears. The ladder stage circuit 25 is charged alternately with the positive power supply 21 and the negative power supply 22, and the alternating voltage of the rectangular wave is applied to the EUT 6 by switching using the saturation of the supersaturated reactor 24 a. The effect is the same as that of the first aspect, but is characterized in that a high-speed switch having a control function and an operation mechanism is not used.

The effect of the void detecting device according to the ninth aspect is that the ladder stage circuit 25 connected to both ends of the tester 26 is provided.
a, 25b are connected to the high-speed switches 30a, 3
0b is alternately turned on / off (open / closed) to charge the battery, and the high-speed switches 31a and 31b are turned on / off in conjunction with the on / off operation of the high-speed switches 30a and 30b. An alternating voltage of waves is applied. The effect is the same as that of the first aspect, but is characterized in that only one charging power source is used.

The high-speed switches 31a and 31b can be replaced with supersaturated reactors. The operation and effect are the same as those of the eighth aspect. The high-speed switch described in this embodiment has the following specifications in addition to the mechanical switch. (A) Thyristor, GTO (gate turn off), IGBT (insulated gate gate)
A semiconductor such as a bipolar transistor is used. In the case where the same high-speed switch causes positive and negative currents to flow, a switch circuit connected in anti-parallel to these semiconductor elements is formed.
(B) Use a discharge tube such as a thyratron, an Ignatron, or a triger switch.

[0064]

According to the present invention, the presence or absence of a void in an insulator can be detected by detecting a void discharge that generates only a weak pulse signal in a partial discharge test. Further, the position of the void can be roughly specified. As a result, a highly reliable void detection device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a void detection device according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a void detection device according to an embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a void detecting device according to an embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a void detection device showing another embodiment.

FIG. 5 is a sectional view of a void detection object according to an embodiment of the present invention;

FIG. 6 is a sectional view of a void detection object according to an embodiment of the present invention;

FIG. 7 is a circuit configuration diagram of a void detection device according to a sixth embodiment.

FIG. 8 is a circuit diagram of a void detecting device according to an embodiment of the present invention.

FIG. 9 is a circuit diagram of a void detecting device according to an embodiment of the present invention.

FIG. 10 is an explanatory diagram showing the operation of claim 1;

FIG. 11 is an explanatory diagram showing the operation of claim 2;

FIG. 12 is an explanatory diagram showing the operation of FIG. 11;

FIG. 13 is an explanatory diagram showing the operation of claim 5;

FIG. 14 is an explanatory diagram showing an equivalent circuit of FIG.

FIG. 15 is an explanatory diagram showing the operation of FIG.

FIG. 16 is an explanatory diagram showing actual waveforms of FIG.

FIG. 17 is an explanatory diagram showing a relationship between a gas pressure (SF6 gas) and a discharge voltage.

FIG. 18 is an explanatory diagram showing a partial discharge voltage waveform in a void.

FIG. 19 is an explanatory diagram showing a Vt characteristic of a gas flash voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial frequency power supply 2 Supersaturated reactor 3 Charging capacitor 4 Transformer 5 Coupling capacitor 6 Tester 7, 8 Pulse detector 9 VVVF power supply 50 Void detection circuit

Claims (8)

[Claims] 1. A transformer connected to an AC power supply for transforming an applied AC voltage, a saturable reactor connected in series to the transformer and adjusting a waveform of the AC voltage applied to the transformer, A charging capacitor connected in parallel to the power supply side of the transformer and supplying a pulse current; a coupling capacitor connected in parallel to the load side of the transformer; and a coupling capacitor connected in series with the coupling capacitor and via the coupling capacitor. A pulse detector that detects a pulse current flowing through the DUT, and a void detection circuit that detects a void present in the DUT based on a pulse output signal output from the pulse detector. Detection device. 2. A second pulse detector connected in series with the DUT to detect a pulse current flowing through the DUT through the coupling capacitor, and a first and a second pulse detector. 2. The void detection device according to claim 1, further comprising a void detection circuit connected to the first circuit and operated by the sum of the two pulse currents. 3. A transformer connected to a variable voltage variable frequency power supply for transforming an applied AC voltage, a coupling capacitor connected in parallel to a load side of the transformer, and the power supply connected to the coupling capacitor. A void detector comprising: a pulse detector for detecting a pulse current flowing through a sample; and a void detection circuit for detecting a void present in the sample based on a pulse output signal output from the pulse detector. . 4. An insulating spacer that insulates and supports a high-voltage conductor that is a charged part of the sample from a ground side, a high-resistance conductive layer applied around an insulator that covers the high-voltage conductor, 5. A detection electrode provided in contact with the high-resistance conductive layer.
The void detection device described in 1 above. 5. The void detection device according to claim 1, wherein a pulse detector is connected in series with the detection electrode. 6. A DC power supply connected in series with a resistor to form a series circuit to supply a DC voltage, a high-speed switch for short-circuiting the DC power supply, and a capacitor and a reactor connected in a ladder stage. A ladder stage circuit connected to the high-speed switch, a pulse detector connected to the ladder stage circuit for detecting a pulse current flowing through the sample, and a pulse output signal output from the pulse detector present in the sample. And a void detection circuit for detecting a void. 7. A ladder circuit connected in series with a resistor to form a series circuit and supplying a DC voltage, and a ladder stage circuit configured by connecting a capacitor and a reactor in a ladder stage and connected to the DC power source. A transformer connected to the ladder stage circuit, a high-speed switch connected between the ladder stage circuit and the transformer to interrupt the voltage applied to the transformer, and connected in parallel to the load side of the transformer; A coupling capacitor, a pulse detector connected to the coupling capacitor and detecting a pulse current flowing through the DUT, and detecting a void present in the DUT based on a pulse output signal output from the pulse detector. And a void detection circuit. 8. The void detecting device according to claim 7, wherein said high-speed switch is a saturable reactor.