Three-layer sample structure and method for measuring ionization current characteristics of insulating material
Technical Field
The invention belongs to a measurement technology of ionization current characteristics in an insulating material, and particularly relates to a method for measuring the ionization current characteristics of a material by using a barrier material to block the injection of charges into the material to be measured through an electrode so that the obtained conduction current values are all caused by ionization.
Background
In insulating materials for high voltage direct current transmission equipment, the accumulation of space charge is one of the main causes of dielectric breakdown, and current is an important form of characterization of the insulating properties of the material. In the prior art, current characteristics in dielectric materials can be measured and analyzed using high field conductance systems. The current in a material is caused by the directional migration of carriers, and it is generally considered that at low field strengths, the carriers in the dielectric material are mainly derived from the charges generated by ionization of the material, and at high field strengths, the carriers are mainly derived from the charges injected by the electrodes, but the contribution of ionization to the current is mainly concentrated in qualitative analysis.
In the existing measurement technology for the current characteristics of the insulating material, the source of the conduction current is not only the charge injected at the electrode, but also the charge generated by the ionization of the insulating material, and the factors are interwoven together, so that the current characteristics influenced by the ionization cannot be effectively distinguished, and the research on the current characteristics influenced by the ionization cannot be realized.
Disclosure of Invention
The invention utilizes the limiting effect of the barrier material on the injected charges in the tested material to ensure that the tested current characteristics are all caused by ionization, thereby realizing the research on the ionization characteristics in the insulating material.
In order to achieve the purpose, the invention adopts the following technical scheme:
a three-layer sample structure for measuring ionization current characteristics of an insulating material, comprising:
the first barrier material is positioned above the tested sample and is in close contact with the tested material;
the measured material is the measured target material;
and the second barrier material is positioned below the sample to be tested and is in close contact with the material to be tested.
The dielectric constant of the blocking material is similar to that of the material to be detected, the conductivity is far smaller than that of the material to be detected, and the injection threshold value is higher than that of the material to be detected.
The acoustic impedances of the blocking material and the tested material, namely the sound velocity in the material is multiplied by the density to be similar, and in the aspect of thickness, the proportion of the thickness of the blocking material to the sound velocity of the blocking material is larger than the proportion of the thickness of the tested material to the sound velocity of the tested material.
A current measuring method using the specimen structure for measuring characteristics of ionization current in an insulating material according to claim 1, comprising the steps of:
1) sequentially forming a three-layer sample structure by using a first barrier material, a tested material and a second barrier material;
2) placing the three-layer test structure between a high-voltage electrode and a measuring electrode, and adjusting the electrode to enable the sample to be stably and tightly contacted with the electrode;
3) placing the three-electrode system in a high-temperature oven, wherein the temperature of the oven is adjustable at 20-70 ℃, connecting a high-voltage direct-current power supply, a high-resistance meter and a grounding wire with the three-electrode system, and the high-voltage direct-current power supply is adjustable at-60 kV to +60 kV;
4) closing the oven door, setting the temperature of the high-temperature oven to be 20-80 ℃, and standing for 20-30 minutes to stabilize the temperature of the sample;
5) turning on a high-voltage direct-current power supply, adjusting the voltage within the range of-60 kV to +60kV, measuring the current by using a high-resistance meter, wherein the theoretical measurement range is 1fA to 21mA, and recording and processing the current data on a computer.
Compared with the prior art, the invention has the following beneficial effects:
the invention realizes effective extraction of ionization current in the insulating material by utilizing a three-layer sample structure; the first barrier material and the second barrier material are respectively contacted with the high-voltage electrode and the measuring electrode, and the measured material is clamped in the middle; because the insulating property and the charge injection threshold of the first blocking material and the second blocking material are far higher than those of the tested material, compared with the tested material, the first blocking material can realize the blocking of the charges injected into and extracted from the first electrode into the three-layer sample structure, and the second blocking material can realize the blocking of the charges injected into and extracted from the second electrode into the three-layer sample structure under certain field intensity; the charges from the electrodes are blocked, and no corresponding current is generated; the tested material can generate ionization phenomenon under the action of temperature and electric field due to relatively poor insulating property, and the electric charge generated by ionization moves towards the opposite direction of polarity under the action of the electric field; when the ionized charges move to the interface between the blocking material and the measured material, because the blocking material has the insulation performance far better than that of the measured material, the charges cannot smoothly enter the blocking material to further move, but are blocked at the interface; due to the blocking effect of the blocking material on the injection and extraction of charges of the electrode and the ionization charges in the tested material, all carriers in the tested material can be considered to be derived from the charges generated by the ionization of the tested material; the electric charges generated by ionization directionally move in the tested material to generate current, so that the extraction of the ionization current characteristics in the tested material is realized.
In conclusion, the invention realizes measurement at different temperatures by controlling the temperature of the oven, realizes extraction of ionization current generated by ionization by a three-layer sample structure, and realizes measurement of ionization current characteristics in the insulating material by the system. The invention can research the ionization current characteristics of the insulating material at different temperatures and different field strengths, and provides experimental and theoretical support for the research of the ionization characteristics of the direct-current insulating material.
Drawings
FIG. 1 is a block diagram of a three-layer test structure for measuring ionization current in an insulating material according to the present invention;
FIG. 2 is a block diagram of a three-electrode system for performing current measurement in a test configuration in accordance with the present invention;
FIG. 3 is a block diagram of the structure of a measurement pole, a guard pole and a sample cell according to an embodiment of the present invention;
fig. 4 is a flow chart of the operation of the present invention for measuring the ionized charges in the insulating material at different temperatures.
In the figure: 101 is a first barrier material, 102 is a measured insulation material, and 103 is a second barrier material.
201 is a metal rod, 202 is a spring, 203 is a high-voltage pole, 204 is epoxy protection, 205 is a polytetrafluoroethylene backing plate, 206 is a sample groove, 207 is a protective pole, 208 is a measuring pole, 209 and 218 are connecting wires, 210 is a connecting terminal, 211 is an upper fixing plate, 212 is an epoxy column, 213 is an aluminum support plate, 214 is a high-voltage direct-current power supply, 215 is a 6517b type high-resistance meter, 216 is a computer, and 217 is a sample.
301 is a guard electrode, 302 is a measurement electrode, and 303 is a sample cell.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
There is provided a three-layer specimen structure for measuring ionization current, the structure comprising:
the first barrier material has the conductivity far smaller than that of the tested material, has a higher injection threshold value, is positioned above the tested sample and is in close contact with the tested sample;
the measured material is the measured target material;
the second barrier material has conductivity far smaller than that of the tested material, has a higher injection threshold, is positioned below the tested sample and is in close contact with the tested sample.
There is provided a current measurement system for measuring a current characteristic of an insulating material, the system comprising: the three-electrode measuring system comprises a high-voltage electrode, a measuring electrode and a protective electrode, wherein the high-voltage electrode of the three-electrode measuring system is connected with one end of the high-voltage direct-current power supply, the measuring electrode is connected with one end of the high-resistance meter through a circuit overcurrent protection device, and the protective electrode of the three-electrode measuring system, the other end of the high-resistance meter, the other end of the circuit overcurrent protection device and the other end of the high-voltage direct-current power supply are all grounded; and the signal output end of the high impedance meter is connected with a computer for performing corresponding calculation according to the acquired current signal.
The invention is further improved in that a sample groove is added on the periphery of the three-electrode system, and the height of the sample groove is 10-20 mm.
The invention is further improved in that the three-electrode system is placed in a high-temperature oven during measurement, and the temperature is adjustable from 30 ℃ to 80 ℃.
A test method for measuring the ionization current of an insulating material is provided, which comprises the following steps:
1) sequentially forming a three-layer sample structure by using a first barrier material, a tested material and a second barrier material;
2) placing the three-layer test structure between a high-voltage electrode and a measuring electrode, and adjusting the electrodes to enable the sample to be stably and tightly contacted;
3) the three-electrode system is placed in a high-temperature oven, the temperature range is 30-80 ℃, a high-voltage direct-current power supply, a high resistance meter and a grounding wire are connected with the three electrodes, and the amplitude of the high-voltage direct-current power supply is-60 Kv-plus 60kV adjustable;
4) closing the oven door, setting the temperature of the high-temperature oven, and standing for 20-30 minutes to stabilize the temperature of the sample;
5) and turning on a high-voltage direct-current power supply, regulating voltage, measuring current by using a high-resistance meter, and recording and processing on a computer.
As shown in fig. 1, in order to realize a three-layer measurement structure for measuring ionized charges in a material to be measured, which includes a first barrier material 101, a specimen 102 and a second barrier material 103, the three-layer measurement structure is placed between a high voltage pole 203 and a measurement pole 208 during measurement.
As shown in fig. 2, a three-electrode current measuring system according to an embodiment of the present invention includes: a high voltage electrode 203 for contacting the upper side of the sample 217; the epoxy 204 protects the high voltage electrode 203 and prevents the edge of the electrode from breaking through air; a guard electrode 207 for leaking a current transferred along the surface of the sample, and connected to an aluminum support plate 213 to which a ground line is connected through a connection line 218; 208 is a measuring pole, which is contacted with the lower side of the sample 217 and is connected with a connecting terminal 210 through a connecting wire 209; 206 is a sample groove for measuring liquid materials or solid-liquid mixed materials; the measuring pole 208, the protective pole 209 and the sample groove 206 are all fixed on a polytetrafluoroethylene backing plate 205; 211 is an upper epoxy fixing plate, a hole is arranged in the middle and penetrates through the metal rod 201, the metal rod 201 is connected with a high-voltage direct-current power supply 214 through a protective resistor R2, and the lower side of the metal rod is connected with a high-voltage electrode 203; the spring 202 is sleeved on the metal rod 201 and acts on the high-voltage pole 203 and the upper fixing plate 211 to apply certain pressure to the sample 217; the upper fixing plate 211 and the aluminum support plate 213 are fixed by four epoxy columns 212; the connection terminal 210 is connected with the high resistance meter 215 through a connection line, and the high resistance meter 215 is connected with a computer.
And a sample groove is added on the periphery of the three-electrode system, and the height is 10-20 mm.
As shown in fig. 3, 301 is a guard electrode, 302 is a measurement electrode, and 303 is an oil groove.
As shown in fig. 4, the method of the present invention includes: manufacturing a three-layer sample structure which is respectively a barrier material, a tested material and a barrier material from top to bottom, wherein the three layers of materials are in close contact, and no air bubble exists in the middle; placing the prepared three-layer sample structure between a high-voltage electrode and a measuring electrode, wherein the high-voltage electrode, the sample structure and the measuring electrode are in uniform contact and are pressed tightly by the pressure of a spring; placing the three-electrode system in a high-temperature oven, connecting a high-voltage electrode with a high-voltage direct-current source, connecting an outlet terminal of a measuring electrode with a 6517B type high-resistance meter, and connecting an aluminum support plate with a ground wire; setting the temperature of the oven to be 30 ℃, standing for 20 minutes to enable the temperature of the sample to reach the set temperature of 30 ℃; opening a switch of the high-voltage direct-current source, and adjusting the output voltage to be 18 kV; the current value at the measuring electrode was measured using a model 6517B high resistance meter and conducted to a computer for processing the current data.