JPH04248479A - Method and device for detecting partial discharge of mold bus - Google Patents

Abstract

PURPOSE:To enable a partial discharge to be observed and diagnosed with an improved sensitivity with a mold bus even under a live wire. CONSTITUTION:A sensor 2 has a rubber piece 5, an electrode 6, a shield container 7, and a coil 8 and a connector 9 as inductance elements. The rubber piece 5 is allowed to contact an external conductor of a mold bus 1. The electrode 6 is provided being adhered to a rear surface of the rubber piece 5 and is capacity-coupled to an external conductor 11 of the mold bus 1 through the rubber piece 5. The coil 8 is connected in series to a coupling capacity according to the electrode 6 and constitutes a resonance circuit along with this coupling capacity. The shield container 7 houses the electrode 6 and the coil 8 and is shielded. A signal from the coil 8 within the shield container 7 is led to an outside through the connector 9. The sensor 2 is connected to an oscilloscope 4 for observation through a coaxial cable 3 which is connected to the connector 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to a partial discharge generated inside an insulator and at an insulator-conductor interface at a connection portion of a mold bus bar and parts in the vicinity thereof.
The present invention relates to a method and device for detecting a partial discharge in a mold busbar that detects partial discharge (PD), and particularly relates to a method and device for detecting partial discharge in a mold busbar that can detect the partial discharge with high sensitivity under a live wire.

0002

[Prior Art] It is important to maintain insulation performance not only in high-voltage power transmission wiring components but also in medium- and low-voltage wiring components.
It is extremely important to ensure safety and reliability, etc.
It is necessary to inspect and diagnose insulation performance from time to time. As an insulation diagnostic technique for the cable itself, the following method is effective and has been commercialized as a live wire insulation diagnostic device.

In the first method, an AC blocking filter for blocking alternating current is provided between the neutral point of the grounding transformer and the cable shield, and the neutral point of the grounding transformer and the cable shield are connected under live wires. A direct current is superimposed between the cables and the insulation resistance of the cable is measured up to a high resistance.

A second method involves measuring the tan δ of the cable. That is, this method is called the dielectric loss tangent method, in which the cable current flowing through the grounding wire is detected by a CT (current transformer), and the voltage applied to the cable is measured via a voltage divider. , find the tan δ of the cable.

However, the first and second methods described above mainly detect water tree deterioration of cables, and these methods usually only diagnose cables that have been in use for more than 10 years. I can't.

[0006] In addition, for medium and low voltage wiring components, unlike ultra-high voltage mainline cables, there is a possibility that operation can be stopped during measurement, and in that case, partial discharge occurring within the power cable may be detected. It is considered possible to measure partial discharge using the following method that has been proposed in the past.

That is, conventional methods for detecting partial discharge occurring in power cables include, for example, the tuned detection method and the A
There is a method using an E (acoustic emission) sensor.

[0008] A tunable detection device using the tunable detection method connects a coupling capacitor and a detection impedance in series between an internal conductor at a terminal end of a power cable or the like and a metal shielding layer. The potential difference generated between both ends is extracted by a tuned amplifier with a tuning frequency of several hundred kHz.

However, since this tunable detection device requires a signal to be extracted from an internal conductor, detection under live wires is difficult, and a dedicated coupling capacitor is also required. Furthermore, since the tuning frequency of this device is several hundred kHz, it is easily affected by surrounding noise, and although good detection accuracy can be obtained in experiments in a shielded room, it is difficult to apply it to cables, etc. after installation. .

[0010] Furthermore, a detection device using an AE sensor is
An AE sensor is used to detect elastic waves propagating inside an insulator due to partial discharge, but while this device is not affected by electrical noise, it is highly sensitive to ultrasonic waves because they travel in a straight line. It has directivity, and detection sensitivity is extremely reduced depending on the detection position.

[0011]Furthermore, at the connection part of the power cable etc.
A detection method has also been proposed in which the metal shield layer is insulated and the potential difference generated between the two metal shield layers sandwiching the insulating part when a partial discharge occurs is detected by a detection impedance connected between the two metal shield layers (``Minamiikegami''). line 275
"Partial discharge test results of kV CV cable line"; Katsuta et al., Institute of Electrical Engineers of Japan Insulating Materials Study Group material EIM-90-2
0).

[0012] This method is limited to application only to connections where the metal shield layer is insulated, and since the metal shield layer is not grounded, it lacks safety in the event of a short-circuit accident. In addition, the equipment is large and measurement requires skill.

[0013]In practice, in medium and low voltage wiring parts such as load break elbows, there are many cases where dielectric breakdown occurs at parts such as connecting parts. These dielectric breakdowns are thought to be caused by partial discharges occurring at the interfaces of components. For this reason,
Although it is desirable to locally and sensitively observe and diagnose partial discharges on the parts themselves, this has not been studied much as a specific technique for implementation. Furthermore, with the recent spread of computers, uninterrupted inspection has become necessary in almost all cases, and partial discharge observation using the conventional measurement method as described above is not preferred.

Regarding the load break elbow, there is a voltage detection terminal for dividing the line voltage through a capacitor and taking it out to the outside, and it is conceivable to use this to detect partial discharge.

However, the outer conductor of the molded bus bar is exposed, and there is no voltage dividing part such as a voltage detection terminal in the case of a load break elbow.

That is, as shown in FIG. 4, which shows a partial cross section of an example of a mold bus bar, the mold bus bar 1 has an insulating layer 12 made of insulating rubber inside an outer conductor 11 made of a conductive polymer such as semiconductive rubber. An internal conductor 13 made of copper (Cu) or the like is provided therebetween. Partial discharge in the mold bus bar 1 is likely to occur in the portion A shown in the figure.

[0017]

[Problems to be Solved by the Invention] Conventionally, when attempting to measure partial discharge in a mold bus bar using a commercially available partial discharge measuring device, as shown in FIG. A series circuit of a resistor 21 and a capacitor 22 is connected between the AC power supply and the grounding point, an AC power supply AC is connected to the internal conductor 13 of the mold bus bar 1, and a coupling is made between the hot side of the AC power supply AC and the grounding point. Connect capacitor 23. A commercially available measuring device is connected to both ends of the series circuit of resistor 21 and capacitor 22.

As described above, by connecting the lead wire directly to the external conductor 11 and using a commercially available partial discharge measuring device, it is possible to measure the position of the insulation deterioration point that is easily affected by external noise and is causing partial discharge. Regardless, partial discharge is detected in the same way. Therefore, with this method, it is not possible to determine the deteriorated portion where partial discharge is occurring, and it is difficult to identify the portion to be removed or replaced. This method cannot be applied to installation sites of molded busbars because of the large influence of noise, and insulation diagnosis using this method is not actually performed.

The present invention has been made in view of these problems, and provides a molded busbar that allows partial discharges to be observed and diagnosed with high sensitivity at the molded busbar, and that can also be inspected under live wires. It is an object of the present invention to provide a partial discharge detection method and a device directly used for carrying out the method.

[0020]

[Means for Solving the Problems] A partial discharge detection method for a mold bus bar according to the present invention includes an insulating member that is brought into contact with an external conductor of the mold bus bar, and capacitive coupling to the external conductor via this insulating member. using a manually operable detection unit having an electrode forming a coupling capacitance, an inductance element coupled in series with the coupling capacitance, and a shielding member shielding the electrode and the inductance element, the insulating member is connected to the mold busbar. The present invention is characterized in that partial discharge in the mold bus bar and its vicinity is detected by resonance characteristics between the coupling capacitance and the inductance element of the detection unit when the detection unit is brought into contact with a desired portion of the external conductor.

The partial discharge detection device for a mold bus bar according to the present invention includes: an insulating member that comes into contact with the external conductor of the mold bus bar; an electrode that is capacitively coupled to the external conductor via the insulating member; an inductance element that is coupled in series to a coupling capacitance formed by the coupling capacitor and forms a resonant circuit together with the coupling capacitance; and a shielding container that shields the electrode and the inductance element and forms a detection section together with the insulating member, the electrode and the inductance element; a signal processing means for processing the output of the resonant circuit, and converts the high frequency component of the signal generated in the mold bus bar and the power transmission section in the vicinity thereof by the partial discharge pulse and propagating through the conductive layer of the power transmission section into the resonant circuit. It is characterized by detection using the resonance characteristics of.

[0022]

[Operation] In the mold bus bar partial discharge detection method and apparatus of the present invention, a partial discharge surge appearing on the mold bus bar is detected by a manually operable detection section. The detection unit includes an insulating member that is in contact with the outer conductor of the mold bus bar, an electrode that is capacitively coupled to the outer conductor via the insulating member to form a coupling capacitance, and coupled in series to the coupling capacitor. and a shield member that shields the electrode and the inductance element. By bringing the insulating member of the detection section into contact with a desired portion of the external conductor of the mold bus bar, partial discharge is generated in the mold bus bar and its vicinity by utilizing the resonance characteristics of the coupling capacitance and inductance element of the detection section. can be detected.

[0023] In the present invention, a detecting section that can come into contact with any part of the mold bus bar by manual operation is used.
The mold busbar insulation diagnosis can be performed under live wire conditions. The detection unit connects an inductance element to a coupling capacitance formed by an electrode capacitively coupled to the external conductor via an insulating member, configures a resonant circuit with the inductance element and the coupling capacitance, and utilizes resonance characteristics. Detects partial discharge with high sensitivity.

[0024] The present invention is a method of detecting the high frequency component of the traveling wave traveling from the outer metal layer toward the ground when a partial discharge occurs by manually abutting the detection section on an arbitrary point on the mold bus bar. , measurement can be performed simply by touching the detection unit to the mold bus bar. Therefore, the mold busbar in actual use can be easily inspected at any time, and partial discharge measurement under live wire conditions is also easy.

Furthermore, since the present invention uses a method of detecting traveling waves propagating through the outer metal layer, there is no need to bring the outer metal layer into a non-grounded state. For this reason, the present invention does not have problems such as being limited in its application or being reduced in safety depending on the type of the connecting portion or the like.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the configuration of a partial discharge detection device for a mold bus bar according to an embodiment of the present invention.

The detection section, that is, the sensor 2 has a rubber piece 5 as an insulating member, an electrode 6, a shield container 7, a coil 8 as an inductance element, and a connector 9. The rubber piece 5 is brought into contact with the outer conductor of the mold bus bar 1 . Electrode 6
is provided in close contact with the back surface of the rubber piece 5, and is capacitively coupled to the external conductor 11 of the mold bus bar 1 via the rubber piece 5. The coil 8 is coupled in series with the coupling capacitance formed by the electrode 6, and forms a resonant circuit together with this coupling capacitance. The shield container 7 is made of a conductor or an insulator having a conductive layer formed by metal vapor deposition or the like on its inner surface, and accommodates and shields the electrode 6 and the coil 8. A signal from the coil 8 inside the shield container 7 is led out to the outside via a connector 9 made of a coaxial cable connector conforming to, for example, the BNC standard.

The sensor 2 is connected to an observation oscilloscope 4 via a coaxial cable 3 connected to a connector 9.

During measurement, the rubber piece 5 of the sensor 2 is pressed against the exposed outer conductor 11 of the mold bus bar 1. At this time, the sensor 2 is held by the worker as shown in FIG. 2 and is operated as if a doctor were operating a stethoscope. For this reason, it is desirable to further provide a protective rubber cover 10 on the outside of the shield container 7, as shown in FIG. Particularly when the shield container 7 is made of a conductor, a rubber cover 10 is provided for insulation and protection. With the sensor 2 in contact with the outer conductor 11 of the mold bus bar 1, the outer conductor 11 is inserted through the rubber piece 5.
A coupling capacitance formed by the electrode 6 and the coil 8 is connected in series to the coil 8. A partial discharge signal detected by the resonant circuit constituted by the coupling capacitance and the coil 8 is extracted to the outside of the shield container 7 via the connector 9 and observed by the oscilloscope 4 via the coaxial cable 3. Currently, even portable oscilloscopes have 100MHz.
Oscilloscopes with better accuracy than z are commercially available, and partial discharge measurements during periodic inspections can be easily performed using such oscilloscopes. The resonant frequency of the resonant circuit is as follows:
Approximately 30 to 50 MH, taking into account external noise, etc.
It is recommended to set it within the range of z.

As shown in FIG. 3, this sensor 2 can be easily pressure-contacted to any plurality of locations on the external conductor 11 of the mold bus bar 1, and by successively contacting the plurality of locations,
By comparing the magnitudes of the output detection signals, the location where the discharge occurs can be easily estimated. That is, the sensor 2 is sequentially brought into contact with a plurality of locations on the external conductor 11 of the mold bus bar 1 to observe detection signals, and it is estimated that partial discharge is occurring near the location where the detection signal is maximum. In this way, since the location of discharge generation can be estimated, it is also possible to predict before destruction whether only parts such as the mold bus bar need to be replaced or whether the cable needs to be re-laid.

Therefore, the apparatus shown in FIG. 1 has the following various advantages. Partial discharge can be measured at any time when the line is live, so it can be used for periodic inspections of power distribution equipment, etc. Since the measurement can be performed in a short time with simple operations, it is easy to detect a large number of locations. By comparing the magnitudes of the detection signals, it is possible to evaluate the location where partial discharge occurs. Since it is possible to detect in which part of the mold busbar a partial discharge is occurring, it is possible to specify the part to be replaced during repair, and repair work can be easily performed. If a system capable of constantly monitoring detection signals is constructed based on this device, even more reliable partial discharge detection of mold busbars can be performed.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the invention.

For example, in the above description, the case where the detection signal from the sensor 2 is observed with the oscilloscope 4 has been described, but if the detection signal is integrated by an integrator and the partial discharge pulse waveform is output as a current value, the detection The signal waveform can be recorded with a recorder or the like. Furthermore, the detection signal of the sensor 2 that has passed through the integrator can be easily measured with a hand-held ammeter.

[0035]

As described above, according to the present invention, the high frequency component of the traveling wave traveling from the outer metal layer toward the ground when a partial discharge occurs can be detected at any location on the mold bus bar by manual operation. A method for detecting partial discharge in a mold bus bar, which can be detected and diagnosed with high sensitivity by simply touching the parts of the mold bus bar, and also enables inspection under live wires, and its implementation. We can provide equipment for direct use.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a partial discharge detection device for a mold bus bar according to an embodiment of the present invention.

FIG. 2 is a perspective view showing how the sensor shown in FIG. 1 is in use.

FIG. 3 is a diagram for explaining an example of how the sensor shown in FIG. 1 is used.

FIG. 4 is a cross-sectional view for explaining the configuration of a mold generatrix.

FIG. 5 is a diagram for explaining a conventional method of measuring partial discharge in a mold bus bar.

[Explanation of symbols]

1; Mold bus bar 2; sensor 3; Coaxial cable 4;Oscilloscope 5; Rubber piece 6; Electrode 7; Shield container 8; coil 9; Connector 10; Protective rubber cover

Claims (2)

[Claims] 1. An insulating member that is in contact with an external conductor of a mold busbar, an electrode that is capacitively coupled to the external conductor through the insulating member to form a coupling capacitor, and an electrode that is coupled in series to the coupling capacitor. A manually operable detecting section having an inductance element and a shielding member that shields the electrode and the inductance element is used, and when the insulating member is brought into contact with a desired portion of the outer conductor of the mold bus bar, the detecting section is activated. A method for detecting partial discharge in a mold bus bar, comprising detecting partial discharge in the mold bus bar and its vicinity based on the resonance characteristics of the coupling capacitance and the inductance element. 2. An insulating member that is in contact with the outer conductor of the mold bus bar, an electrode that is capacitively coupled to the outer conductor via this insulating member, and an electrode that is coupled in series with the coupling capacitance by this electrode, an inductance element that together forms a resonant circuit; a shield container that shields the electrode and the inductance element to form a detection section together with the insulating member, the electrode and the inductance element; and a signal processing means that processes the output of the resonant circuit. , and detects a high frequency component of a signal generated in the mold bus bar and the power transmission section in the vicinity thereof by the partial discharge pulse and propagating through the conductive layer of the power transmission section using the resonance characteristics of the resonant circuit. Partial discharge detection device for mold busbars.