阅读说明：本技术 一种空间电荷与漏电流联合测量装置及测量方法 (Space charge and leakage current combined measuring device and measuring method ) 是由 吕泽鹏 彭锦阳 吴锴 马运同 陈嘉欣 张琛 张天悦 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种空间电荷与漏电流联合测量装置及测量方法,包括相互对接的上部电极单元与下部电极单元,形成一个屏蔽室,待测平板试样置于上部电极单元与下部电极单元之间；外电路分别连接上部电极单元和下部电极单元形成电流回路；通过连接上部电极单元程控开关断开,连接下部电极单元程控开关接通测量漏电流；通过连接上部电极单元程控开关接通,连接下部电极单元程控开关接地测量空间电荷。本发明能够实现空间电荷和漏电流的联合测量,避免了信号的干扰,实现了将空间电荷数据和电流数据在时序上精确的对应。(The invention discloses a space charge and leakage current combined measuring device and a measuring method, comprising an upper electrode unit and a lower electrode unit which are mutually butted to form a shielding chamber, wherein a flat plate sample to be measured is arranged between the upper electrode unit and the lower electrode unit; the external circuit is respectively connected with the upper electrode unit and the lower electrode unit to form a current loop; the upper electrode unit programmable switch is connected and disconnected, and the lower electrode unit programmable switch is connected and disconnected to measure leakage current; the upper electrode unit programmable switch is connected for switching on, and the lower electrode unit programmable switch is connected for grounding measurement of space charge. The invention can realize the combined measurement of space charge and leakage current, avoids the interference of signals and realizes the accurate correspondence of space charge data and current data in time sequence.)

1. A space charge and leakage current combined measuring device is characterized by comprising an upper electrode unit, a lower electrode unit and an external circuit; the upper electrode unit and the lower electrode unit are mutually butted to form a shielding chamber, and a flat plate sample to be tested is arranged between the upper electrode unit and the lower electrode unit; the external circuit is respectively connected with the upper electrode unit and the lower electrode unit to form a current loop;

the programmable switch connected with the external circuit of the upper electrode unit is switched off, the programmable switch connected with the lower electrode unit is switched on, and the leakage current of the flat plate sample to be measured is measured; the programmable switch connected with the upper electrode unit is switched on, the programmable switch connected with the lower electrode unit is grounded, and the space charge of the flat plate sample to be measured is measured.

2. The space charge and leakage current combined measuring device according to claim 1, wherein the upper electrode unit comprises a metal cylinder, an upper electrode, a current limiting resistor, a coupling capacitor and an epoxy tube; the current-limiting resistor and the coupling capacitor are respectively connected with the upper electrode and are jointly packaged in the metal cylinder, the top of the metal cylinder is provided with an epoxy tube, and the current-limiting resistor is packaged in the epoxy tube.

3. The device of claim 2, wherein the top electrode is fixed at the center of the bottom of the metal cylinder and protrudes slightly from the bottom surface of the metal cylinder; the bottom of the upper electrode is a semi-conducting layer, and a flat plate sample to be tested is placed below the semi-conducting layer and is in contact with the semi-conducting layer.

4. The joint space charge and leakage current measuring device according to claim 1, wherein the lower electrode unit comprises a lower electrode plate, a current ring, an insulating ring and a piezoelectric sensor; the upper surface of the lower electrode plate is provided with an annular groove, the bottom surface of the annular groove is provided with a current ring embedded groove, and an insulating ring is arranged below the current ring embedded groove; the piezoelectric sensor is connected to the lower surface of the lower electrode plate.

5. The device of claim 4, wherein the piezoelectric sensor is supported by the sensor pad in a sensor shield, the sensor shield is connected to the lower surface of the lower electrode plate, and the piezoelectric sensor is attached to the center of the lower surface of the lower electrode plate.

6. The space charge and leakage current combined measuring device according to claim 2, wherein the external circuit comprises a high voltage pulse power supply and a high voltage direct current power supply which are connected with the upper electrode unit, and a program-controlled switch, an ammeter, a signal amplifier, an oscilloscope and a computer which are connected with the lower electrode unit.

7. The device of claim 7, wherein the high voltage pulse power supply is connected to the coupling capacitor and the high voltage dc power supply is connected to the current limiting resistor.

8. The device for joint measurement of space charge and leakage current according to claim 7, wherein the computer is connected to the piezoelectric sensor via an oscilloscope and a signal amplifier; the computer is connected with the current loop through the ammeter and the program control switch.

9. A method for jointly measuring space charge and leakage current is characterized by comprising the following steps:

placing a flat plate sample to be tested on a lower electrode plate, and placing a semi-conducting layer between an upper electrode and the flat plate sample to be tested;

the current-limiting resistor is connected with a high-voltage direct-current power supply, and the coupling capacitor is connected with a high-voltage pulse power supply through a program-controlled switch;

the current loop is connected with an ammeter to a computer through a program control switch, and the piezoelectric sensor is sequentially connected with a signal amplifier and an oscilloscope to the computer;

the computer controls the switching period of the program-controlled switch, the period is alternately switched on and off, the ammeter is disconnected when the space charge measuring loop is switched on, the high-voltage pulse is disconnected when the current measuring loop is switched on, and the leakage current and the space charge are jointly measured.

10. The method as claimed in claim 9, wherein when the leakage current is measured, the programmable switch connected to the high voltage pulse power supply and the coupling capacitor is turned off to stop generating the pulse signal; the current-limiting resistor is connected with a high-voltage direct-current power supply, and a current loop is connected to a computer through an upper electrode, a semi-conducting layer, a flat plate sample to be tested, a current loop and an ammeter;

when space charge is measured, a high-voltage pulse power supply is connected with a program-controlled switch of a coupling capacitor to collect space charge data, a current-limiting resistor is connected with a high-voltage direct-current power supply, the program-controlled switch grounds a current loop, and a space charge signal passes through an upper electrode, a semi-conducting layer, a flat plate sample to be measured, a piezoelectric sensor, a signal amplifier and an oscilloscope to be transmitted to a computer.

Technical Field

The invention relates to the technical field of high voltage and insulation technology and dielectric medium space charge measurement, in particular to a space charge and leakage current combined measurement device and a measurement method thereof.

Background

The high-voltage direct-current transmission system is an important component of a transmission system in China, and the high-voltage direct-current cable is important equipment in the transmission system. Space charge problems are an important factor influencing the problem of insulation aging of high voltage direct current cables. The space charge condition also has a great influence on the leakage current in the cable insulation, and the change of the space charge polarity and the processes of charge injection, accumulation, extraction and the like all cause the change of the current magnitude. Therefore, the space charge and the current are jointly measured, so that the change rule between the space charge and the current can be revealed, and the space charge condition can be estimated through the current measurement data.

The electroacoustic pulse method (PEA method) belongs to a nondestructive measurement method, and the test principle is that a narrow high-voltage pulse signal is applied to an electrode on one side of a medium, space charges in the medium generate an electric field force under the action of the electric pulse, so that a pressure wave signal is generated, the space charges are converted into an electric signal by a piezoelectric sensor of an electrode unit on the lower portion of a sample, the electric signal is amplified and transmitted to a computer for analysis, and the space charge distribution in the sample can be obtained. Compared with other measuring methods, the electroacoustic pulse method has the characteristics of simple equipment structure, convenient test flow, low cost, electrical isolation of a high-voltage loop and a measuring loop and the like, thereby gradually becoming one of the most important space charge measuring methods and having wide prospects.

The leakage current of the dielectric is also affected by space charge, and at present, the current measurement mainly adopts a three-electrode system. The three-electrode method is a standard method for measuring the volume resistivity of the solid insulating material, and can guide the volume current and the surface current of a medium to different electrodes, so that the accuracy of an experiment is ensured.

For space charge and leakage current measurement, the joint measurement of the two has certain technical difficulties, which are mainly reflected in that the signal interference and the data time sequence correspond to two points. High-voltage pulses are required to be applied to the measurement of the space charge, and the high-voltage pulses have serious interference on current measurement, so that current measurement data are distorted; when high-voltage pulse acts on precision instruments such as an ammeter, the high-voltage pulse has greater risk of damaging the instruments; the space charge measuring electrode and the current measuring electrode are difficult to arrange in space and can generate mutual interference; in the conventional measuring system, space charge and current are respectively measured, the space charge and the current do not strictly correspond to each other in time, the space charge data and the current data are difficult to establish accurate relation in time sequence, and the relation between the space charge data and the current data cannot be accurately reflected.

How to correspond space charge and leakage current data in real time is a problem which needs to be solved for researching the correlation between the space charge and the leakage current. Based on the existing research and theory, the result shows that the space charge and leakage current data can be obtained simultaneously by using the novel composite electrode for measurement, which becomes the key of research.

Disclosure of Invention

In order to solve the above-mentioned defects in the prior art, the present invention aims to provide a space charge and leakage current combined measurement apparatus and a measurement method thereof, which can be used for simultaneously measuring space charge and leakage current in a flat medium, and have the advantages of high measurement accuracy, good real-time correspondence, and simple and compact structure.

The invention is realized by the following technical scheme.

According to a first aspect of the present invention, there is provided a space charge and leakage current combined measuring device comprising an upper electrode unit, a lower electrode unit, and an external circuit; the upper electrode unit and the lower electrode unit are mutually butted to form a shielding chamber, and a flat plate sample to be tested is arranged between the upper electrode unit and the lower electrode unit; the external circuit is respectively connected with the upper electrode unit and the lower electrode unit to form a current loop;

the programmable switch connected with the external circuit of the upper electrode unit is switched off, the programmable switch connected with the lower electrode unit is switched on, and the leakage current of the flat plate sample to be measured is measured; the programmable switch connected with the upper electrode unit is switched on, the programmable switch connected with the lower electrode unit is grounded, and the space charge of the flat plate sample to be measured is measured.

In one embodiment, the upper electrode unit includes a metal cylinder, an upper electrode, a current limiting resistor, a coupling capacitor, and an epoxy tube; the current-limiting resistor and the coupling capacitor are respectively connected with the upper electrode and are jointly packaged in the metal cylinder, the top of the metal cylinder is provided with an epoxy tube, and the current-limiting resistor is packaged in the epoxy tube.

In one embodiment, the upper electrode is fixed at the center of the lower part of the metal cylinder and slightly protrudes out of the lower surface of the metal cylinder; the bottom of the upper electrode is a semi-conducting layer, and a flat plate sample to be tested is placed below the semi-conducting layer and is in contact with the semi-conducting layer.

In one embodiment, the lower electrode unit includes a lower electrode plate, a current ring, an insulating ring, and a piezoelectric sensor; the upper surface of the lower electrode plate is provided with an annular groove, the bottom surface of the annular groove is provided with a current ring embedded groove, and an insulating ring is arranged below the current ring embedded groove; the piezoelectric sensor is connected to the lower surface of the lower electrode plate.

In one embodiment, the piezoelectric sensor is supported in a sensor shield through a sensor cushion layer, the sensor shield is connected to the lower surface of the lower electrode plate, and the piezoelectric sensor is attached to the center of the lower surface of the lower electrode plate.

In one embodiment, the external circuit comprises a high-voltage pulse power supply and a high-voltage direct-current power supply which are connected with the upper electrode unit, a program-controlled switch connected with the lower electrode unit, an ammeter, a signal amplifier, an oscilloscope and a computer.

In one embodiment, the high-voltage pulse power supply is connected with the coupling capacitor, and the high-voltage direct current power supply is connected with the current-limiting resistor.

In one embodiment, the computer is connected with the piezoelectric sensor through an oscilloscope and a signal amplifier; the computer is connected with the current loop through the ammeter and the program control switch.

According to a second aspect of the present invention, there is provided a method for jointly measuring space charge and leakage current, comprising:

placing a flat plate sample to be tested on a lower electrode plate, and placing a semi-conducting layer between an upper electrode and the flat plate sample to be tested;

the current-limiting resistor is connected with a high-voltage direct-current power supply, and the coupling capacitor is connected with a high-voltage pulse power supply through a program-controlled switch;

the current loop is connected with an ammeter to a computer through a program control switch, and the piezoelectric sensor is sequentially connected with a signal amplifier and an oscilloscope to the computer;

the computer controls the switching period of the program-controlled switch, the period is alternately switched on and off, the ammeter is disconnected when the space charge measuring loop is switched on, the high-voltage pulse is disconnected when the current measuring loop is switched on, and the leakage current and the space charge are jointly measured.

In one embodiment, when the leakage current is measured, the program-controlled switch connected with the high-voltage pulse power supply and the coupling capacitor is disconnected, and the generation of the pulse signal is stopped; the current-limiting resistor is connected with a high-voltage direct-current power supply, and a current loop is connected to a computer through an upper electrode, a semi-conducting layer, a flat plate sample to be tested, a current loop and an ammeter;

when space charge is measured, a high-voltage pulse power supply is connected with a program-controlled switch of a coupling capacitor to collect space charge data, a current-limiting resistor is connected with a high-voltage direct-current power supply, the program-controlled switch grounds a current loop, and a space charge signal passes through an upper electrode, a semi-conducting layer, a flat plate sample to be measured, a piezoelectric sensor, a signal amplifier and an oscilloscope to be transmitted to a computer.

The invention has the advantages that the following technical scheme is adopted:

1. the invention adopts the structure that the upper electrode and the lower electrode surround the sample to form a shielding chamber, which can reduce the interference of electromagnetic waves on measurement and achieve the purposes of improving the measurement precision and reducing the noise.

2. The invention adopts the composite lower electrode unit, and the insulation ring and the current ring in the insulation ring are arranged on the lower electrode plate in a groove, so that the two loops are electrically isolated, and the purposes of reasonable layout in space and interference reduction are achieved.

3. The invention adopts the program control switch, alternately switches on the space charge measuring loop and the current measuring loop in a time-sharing way, and separates the two loops in time, thereby achieving the purposes of reducing pulse interference, improving the current measuring precision and protecting the current measuring equipment.

4. The invention adopts the computer to control the program control switch and collect data, can write program to strictly control the action sequence, and achieves the purposes of accurate time sequence and strong comparability.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic diagram showing the composition of an upper electrode unit and a lower electrode unit of a space charge and leakage current combined measuring device according to the present invention;

FIG. 2 is a schematic diagram of an external circuit according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the external circuit connection for measuring leakage current according to the embodiment of the present invention;

FIG. 4 is a schematic diagram of the external circuit connection for space charge measurement according to the present invention.

Wherein 101 is an epoxy tube, 102 is a metal cylinder, 103 is a coupling capacitor, 104 is a current limiting resistor, 105 is an upper electrode, 106 is a semiconductive layer;

201 is a lower electrode plate, 202 is a current loop, 203 is an insulating loop, 204 is a piezoelectric sensor, 205 is a sensor pad layer, and 206 is a sensor shield;

301 is a high-voltage pulse power supply, 302 is a program-controlled switch, 303 is a high-voltage direct-current power supply, 304 is a flat plate sample to be measured, 305 is an ammeter, 306 is a signal amplifier, 307 is an oscilloscope, and 308 is a computer.

Detailed Description

The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.

As shown in fig. 1, a space charge and leakage current combined measuring device according to the present invention includes an upper electrode unit, a lower electrode unit and an external circuit. The flat plate sample to be measured 304 is positioned between the upper electrode unit and the lower electrode unit, and the upper electrode unit and the lower electrode unit are connected with an external circuit to perform space charge and leakage current combined measurement on the flat plate sample to be measured.

The upper electrode unit comprises a metal cylinder 102, an upper electrode 105, a current-limiting resistor 104, a coupling capacitor 103 and an epoxy tube 101, and the upper electrode 105, the current-limiting resistor 104 and the coupling capacitor 103 are packaged in the metal cylinder 102 by epoxy resin; the upper electrode 105 is fixed at the center of the lower part of the metal cylinder 102 and slightly protrudes out of the lower surface of the metal cylinder 102, the bottom of the upper electrode 105 is a semi-conducting layer 106, and a flat plate sample to be tested is placed below the semi-conducting layer 106 and is in contact with the semi-conducting layer 106; the current-limiting resistor 104 and the coupling capacitor 103 are connected to the upper electrode 105, the top of the current-limiting resistor 104 is packaged in the epoxy tube 101 through epoxy resin, and the top of the coupling capacitor 103 is packaged in the metal cylinder 102 through epoxy resin.

The lower electrode unit comprises a lower electrode plate 201, an insulating ring 203, a current ring 202, a piezoelectric sensor 204, a sensor cushion 205 and a sensor shield 206, wherein the lower electrode plate 201 is positioned below the upper electrode unit and is fixed with a metal shell of the upper electrode unit through a metal screw; the upper surface of the lower electrode plate 201 is provided with an annular groove, and the area of the annular groove corresponds to that of the metal cylinder 102; the insulating ring 203 is fixed in the bottom surface of the annular groove of the lower electrode plate 201, and the current ring 202 is fixed in a concentric annular groove on the insulating ring 203; the piezoelectric sensor 204 is attached to the center of the lower surface of the lower electrode plate 201 and supported by a sensor pad 205; the sensor shield 206 supports the sensor pad 205 and is fixed to the lower electrode plate 201.

The piezoelectric sensor is made of beta-vinylidene fluoride (beta-PVDF) thin films, the thickness range is 50-100 mu m, and both sides of the piezoelectric sensor are plated with silver or aluminum to increase the conductivity. The sensor cushion layer is made of alpha-vinylidene fluoride (alpha-PVDF) and is used for matching acoustic impedance of the piezoelectric sensor and eliminating reflected waves.

As shown in fig. 2, the external circuit includes a high voltage pulse power supply 301, a high voltage dc power supply 303, a program controlled switch 302, an ammeter 305, a signal amplifier 306, an oscilloscope 307 and a computer 308, wherein the high voltage pulse power supply 301 is connected to the coupling capacitor 103; the high-voltage direct-current power supply 303 is connected to the current-limiting resistor 104 and is controlled to be switched on and off by the program-controlled switch 302; the ammeter 305 is connected to the current loop 202 and is controlled to be turned off and on by the program-controlled switch 302; the front end of the signal amplifier 306 is connected to the piezoelectric sensor 204, and the rear end is connected to the oscilloscope 307; both the oscilloscope 307 and the ammeter 305 are connected to a computer 308.

In this embodiment, the pulse width of the high-voltage pulse power supply ranges from 10 ns to 20 ns. And the frequency bandwidth of the signal amplifier is not less than 200 MHz. And the sampling rate of the oscilloscope is not lower than 2.5GS/s, and the bandwidth is not lower than 300 MHz.

The high-voltage pulse power supply generates pulses and applies the pulses to the upper electrode through the coupling capacitor; the high-voltage direct current power supply generates high-voltage direct current which is applied to the upper electrode through the current-limiting resistor; the signal amplifier is connected with the piezoelectric sensor to acquire signals; the signal transmission line is connected with the signal amplifier and the current loop and used for outputting space charge and current information; when the leakage current is measured, the program-controlled switch is connected with a current loop, a high-voltage pulse power supply is disconnected, the generation of a pulse signal is stopped, and an ammeter is protected; when space charge is measured, the program-controlled switch grounds the current loop, and the high-voltage pulse power supply is switched on to acquire space charge data.

Applying direct current high voltage to the upper electrode by using a high-voltage direct current power supply to inject space charge into the medium; the high-voltage pulse power supply applies pulse voltage to the upper electrode to enable the space charge to vibrate by electric field force; the piezoelectric sensor collects vibration signals, converts the vibration signals into electric signals and sends the electric signals to the amplifier for amplification and output; the current loop collects current signals and directly outputs the current signals, and joint measurement of space charge and leakage current is achieved.

The embodiment of the invention provides a space charge and leakage current combined measurement method, which specifically comprises the following steps:

1) placing a flat plate sample 304 to be tested on the lower electrode plate 201, and placing the semi-conducting layer 106 between the upper electrode 105 and the flat plate sample 304 to be tested;

2) a high-voltage direct-current power supply 303 is connected to the current-limiting resistor 104, a high-voltage pulse power supply 301 is connected to the coupling capacitor 103 through a program-controlled switch 302, and specific voltage parameters are set as required;

3) connecting the current loop 202 to an ammeter 305 through a signal transmission line, connecting a signal amplifier 306 to an oscilloscope 307 through a signal transmission line, connecting data lines of the ammeter 305 and the oscilloscope 307 to a computer 308, and setting specific range parameters according to experiment requirements;

4) running a computer acquisition program, setting a switching period of the program control switch 302, and enabling the program control switch to be alternately switched on and off according to the period, wherein the ammeter is disconnected when the space charge measurement loop is switched on, and the high-voltage pulse is disconnected when the leakage current measurement loop is switched on.

Specifically, when the leakage current of the flat plate sample to be measured is measured, as shown in fig. 3, the program-controlled switch 302 connected to the high-voltage pulse power supply 301 and the coupling capacitor 103 is disconnected, and the generation of the pulse signal is stopped; the current limiting resistor 104 is connected with a high voltage direct current power supply 303, and a current loop passes through the upper electrode 105, the semi-conducting layer 106, the to-be-tested flat plate sample 304, the current loop 202 and the ammeter 305 to the computer 308.

When measuring the space charge of the flat plate sample to be measured, as shown in fig. 4, the programmable switch 302 connected to the high-voltage pulse power supply 301 and the coupling capacitor 103 is connected to collect the space charge data, the current-limiting resistor 104 is connected to the high-voltage direct-current power supply 303, the programmable switch grounds the current loop, and the space charge signal is transmitted to the computer 308 through the upper electrode 105, the semi-conducting layer 106, the flat plate sample to be measured 304, the piezoelectric sensor 204, the signal amplifier 306 and the oscilloscope 307.

The invention can realize the combined measurement of space charge and leakage current, avoids the interference of signals and realizes the accurate correspondence of space charge data and current data in time sequence.

The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.