An arc current generating device for testing internal arc faults in instrument transformers

Abstract

This specification discloses an arc current generating device for testing internal arc faults in instrument transformers, relating to the field of instrument transformer testing technology. The device comprises a first current conductor, a second current conductor, a high-voltage power supply panel and a low-voltage power supply panel, a low-voltage arc ignition device, and a short-time current testing device. The high-voltage power supply panel is connected to the first current conductor, and the low-voltage power supply panel is connected to the second current conductor. The two ends of the short-time current testing device are respectively connected to the first current conductor and the second current conductor. The low-voltage arc ignition device is arranged within the circuit formed by the high-voltage power supply panel, the low-voltage power supply panel, and the short-time current testing device, and includes conductive particles and a filament. The two ends of the filament are respectively connected to the high-voltage power supply panel and the low-voltage power supply panel. This invention addresses the problems of existing instrument transformer internal arc fault testing methods having a large impact on the power grid and high cost.

Description

Technical Field

[0001] This specification relates to the field of instrument transformer testing technology, and in particular to an arc current generating device for testing internal arc faults in instrument transformers. Background Technology

[0002] According to relevant national standards, the internal arc fault test is applicable to oil-immersed or gas-insulated instrument transformers with Um ≥ 72.5kV. The purpose of the test is to simulate a short circuit within the high-voltage electrical equipment caused by insulation defects in the power system, verifying whether the equipment meets a certain safety level. The test procedure is as follows: 1. An arc shield and a 1-3mm diameter conductor (fuse) for generating the arc are installed between the high-voltage and low-voltage panels inside the sample. 2. The impedance of the test circuit is tested by passing the expected current. The effective value of the expected current should not exceed the test current value, enough to melt the arc-generating fuse, but the arc should not damage the sample. 3. The test current is passed between the high-voltage and low-voltage panels of the sample according to the short-time current test procedure. 4. After the test, the condition of the sample is observed to determine the safety level met by the sample.

[0003] During an internal arc fault test, an arc will be generated briefly after the conductor that produces the arc melts. To maintain the arc, the shortest possible distance between the two ends of the transformer panel is required to maintain the breakdown low voltage. For 110kV~220kV transformers, the shortest distance between the internal high-voltage electrodes and the ground electrode is usually 20mm~30mm. The test voltage to maintain the test current is usually 30kV~40kV. Currently, there are two methods to achieve this test in China: one is to conduct the test on a dedicated line in a 220kV or 500kV power grid transmission system; the other is to use a large generator set to generate electricity and then output it. Regardless of the method, the output of the equipment used for the test must simultaneously meet the requirements of high voltage and high current. Moreover, the impact of the equipment on the power grid during the test is huge (or the cost of generator start-up, operation and maintenance is huge). Currently, the highest voltage level of instrument transformers that can be tested in China is 500kV. There is no capability to test instrument transformers with higher voltage levels. Ordinary short-time current test devices have low-voltage ports, with rated voltages of only a few hundred volts (usually less than 1000V), which cannot meet the test requirements. Summary of the Invention

[0004] This specification provides an arc current generating device for testing internal arc faults in instrument transformers, which solves the problems of existing testing methods for internal arc faults in instrument transformers having a large impact on the power grid and being costly.

[0005] To solve this technical problem, this specification provides the following technical solution:

[0006] On one hand, an arc current generating device for testing internal arc faults in instrument transformers is provided, comprising a first current conductor, a second current conductor, a high-voltage power shield and a low-voltage power shield, a low-voltage arc ignition device, and a short-time current testing device, wherein:

[0007] The high-voltage power supply is connected to the first current conductor, and the low-voltage power supply is connected to the second current conductor; the two ends of the short-time current test device are respectively connected to the first current conductor and the second current conductor; the low-voltage arc ignition device is arranged in the circuit formed by the high-voltage power supply, the low-voltage power supply, and the short-time current test device, and includes conductive particles and a filament, the two ends of which are respectively connected to the high-voltage power supply and the low-voltage power supply.

[0008] The low-voltage arc-ignition device is used to trigger an ignition device arranged inside or outside the conductive particles to make the conductive particles evenly distributed between the high-voltage power screen and the low-voltage power screen to form a conductive particle sol.

[0009] The short-time current testing device is used to start and output current after the formation of conductive particulate sol, so as to melt the filament and form a continuous test arc current between the high-voltage power supply and the low-voltage power supply.

[0010] On the other hand, a method for generating arc current for testing internal arc faults in instrument transformers is provided, including:

[0011] Connect the high-voltage power supply to the first current conductor, connect the low-voltage power supply to the second current conductor, and connect the two ends of the short-time current test device to the first current conductor and the second current conductor respectively; arrange the low-voltage arc ignition device in the circuit formed by the high-voltage power supply, the low-voltage power supply, and the short-time current test device, including conductive particles and a filament, and connect the two ends of the filament to the high-voltage power supply and the low-voltage power supply respectively.

[0012] Triggering a detonation device arranged inside or outside the conductive particles, so that the conductive particles are evenly distributed between the high-voltage power supply and the low-voltage power supply, forming a conductive particle sol;

[0013] The short-time current test device is activated to output current, causing the filament to melt and creating a continuous test arc current between the high-voltage and low-voltage power panels.

[0014] The above-mentioned technical solutions adopted in this specification can achieve the following beneficial effects:

[0015] By igniting conductive particles to form a sol between the electrodes, the actual breakdown field strength is greatly reduced due to the unstable nature of the particle movement. Simultaneously, the distribution of conductive particles between the electrodes significantly shortens the distance between the test electrodes, resulting in a substantial reduction in the port voltage of the short-time current test device. Therefore, while fully meeting the test requirements stipulated in relevant national standards, internal arc fault tests can be completed using the low-voltage port of a common short-time current test device, greatly reducing the capacity and cost of the test equipment, and significantly mitigating the impact of the test equipment on the power grid during testing. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of this specification and form part of this specification, illustrate exemplary embodiments and are used to explain this specification, but do not constitute an undue limitation thereof. In the drawings:

[0017] Figure 1 This is a schematic diagram of an arc current generating device for testing internal arc faults in a current transformer, provided in Embodiment 1 of this specification.

[0018] Figure 2 This is a schematic diagram of the low-voltage arc-starting device provided in Embodiment 2 of this specification;

[0019] Figure 3 This is a flowchart illustrating an arc current generation method for testing internal arc faults in a current transformer, as provided in Embodiment 3 of this specification. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this specification will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0021] The technical solutions provided in the various embodiments of this specification are described in detail below with reference to the accompanying drawings.

[0022] Example 1

[0023] This specification provides an embodiment of an arc current generating device for testing internal arc faults in instrument transformers. The device includes a first current conductor, a second current conductor, a high-voltage power shield and a low-voltage power shield, a low-voltage arc ignition device, and a short-time current testing device.

[0024] like Figure 1As shown, the high-voltage power supply is connected to the first current conductor, and the low-voltage power supply is connected to the second current conductor; the two ends of the short-time current test device are respectively connected to the first current conductor and the second current conductor; the low-voltage arc ignition device is arranged in the circuit formed by the high-voltage power supply, the low-voltage power supply, and the short-time current test device, and includes conductive particles and a filament, the two ends of which are respectively connected to the high-voltage power supply and the low-voltage power supply.

[0025] A low-voltage arc-ignition device is used to trigger an initiation device arranged inside or outside the conductive particles to make the conductive particles evenly distributed between the high-voltage and low-voltage power screens to form a conductive particle sol.

[0026] A short-time current testing device is used to start and output current after the formation of conductive particulate sol, causing the filament to melt and forming a continuous test arc current between the high-voltage and low-voltage power panels.

[0027] In this embodiment, the current-carrying cross-section of the high-voltage and low-voltage power panels is determined based on the test current value within a 1-second duration.

[0028] In this embodiment, the resistivity of the conductive particles is not less than 2.8 x 10⁻⁶. -8 For ohm-meters, the diameter should not exceed 10 micrometers, and the release space concentration should not be less than 10%. Based on this, smaller diameter particles or larger release space concentrations can further reduce the breakdown field strength of the electric shield, thereby enabling a more effective reduction in the capacity of the short-time current test device.

[0029] In this embodiment, the conductive particles include graphene powder.

[0030] In this embodiment, the release space of the graphene powder is 3-5 times the current-carrying cross-sectional space of the high-voltage and low-voltage power supply panels.

[0031] In this embodiment, the detonation device is a miniature blasting device built into the conductive particles or an external pressure release device.

[0032] In this embodiment, the high-voltage and low-voltage shields are arranged at points where the electric field is concentrated or where the insulation is weak, such as between the primary conductor of the transformer and the low-voltage shield, or between the primary conductor of the transformer and the ground of the enclosure, or between the high-voltage flange of the transformer and the grounding pipe.

[0033] In this embodiment, the filament is arranged between or to the side of the high-voltage and low-voltage power panels, and the conductive particles are placed side by side or opposite to the filament.

[0034] In summary, based on data from the internal arc fault testing laboratory, the breakdown field strength under a uniform electric field with different media (insulating oil, SF6) between electrodes ranges from 30 to 50 kV / mm. Under the interference of a burning wire, the breakdown field strength is approximately 1.33 kV / mm. Under particulate interference, the breakdown field strength significantly decreases to 66 V / mm or even lower. This means that by igniting conductive particles to form a sol between the electrodes, the actual breakdown field strength is greatly reduced due to the unstable nature of the particle movement. Simultaneously, the distribution of conductive particles between the electrodes significantly shortens the distance between the test electrodes during the test, and the port voltage of the short-time current testing device is also greatly reduced. Therefore, while fully meeting the relevant national standard requirements, the internal arc fault test can be completed using the low-voltage port of a common short-time current testing device, greatly reducing the capacity and cost of the testing equipment, and significantly mitigating the impact of the testing equipment on the power grid during the test.

[0035] Example 2

[0036] Based on Example 1, this example provides another arc current generating device for testing internal arc faults in instrument transformers. The device includes a first current conductor, a second current conductor, a high-voltage power shield and a low-voltage power shield, a low-voltage arc ignition device, and a short-time current testing device.

[0037] The high-voltage power supply is connected to the first current conductor, and the low-voltage power supply is connected to the second current conductor; the two ends of the short-time current test device are respectively connected to the first current conductor and the second current conductor; the low-voltage arc ignition device is arranged in the circuit formed by the high-voltage power supply, the low-voltage power supply, and the short-time current test device, and includes conductive particles and a filament, the two ends of which are respectively connected to the high-voltage power supply and the low-voltage power supply.

[0038] A low-voltage arc-ignition device is used to trigger an initiation device arranged inside or outside the conductive particles to uniformly distribute the conductive particles between a high-voltage power supply and a low-voltage power supply to form a conductive particle sol.

[0039] A short-time current testing device is used to start and output current after the formation of conductive particulate sol, causing the filament to melt and forming a continuous test arc current between the high-voltage and low-voltage power panels.

[0040] In this embodiment, the high-voltage and low-voltage power shields are typically located where the field strength of the transformer is concentrated or where the insulation is weak, such as between the primary conductor of the transformer and the low-voltage shield, between the primary conductor of the transformer and the enclosure ground, and between the high-voltage flange of the transformer and the grounding pipe. The current-carrying cross-section of the power shield should not be less than: the test current value converted to 1 second (A) / 160 A / mm 2 (copper).

[0041] In this embodiment, as Figure 2The low-voltage arc-ignition device shown includes graphene powder and a filament. The filament and graphene powder pack are pre-embedded before the test. The filament is placed between or to the side of the high-voltage and low-voltage electrical panels. The graphene powder pack is placed side-by-side or opposite to the filament, or horizontally arranged with the current conductors near the electrical panels. A miniature explosive device is built into the graphene powder pack. The explosive force required for the miniature explosive device to meet the release space requirements is: m·g·d = 0.003 J, where m is the mass of graphene (in kilograms), g is the acceleration due to gravity, and d is the distance between the electrical panels (in meters).

[0042] In this embodiment, the graphene powder release space is generally calculated as 3-5 times the current-carrying cross-sectional space of the test electrical panel. For example, the distance between the high-voltage and low-voltage electrical panels is 3cm, and the effective current-carrying cross-section of the electrical panel is 3cm. 2 The release space of graphene powder is within 27 cm. 3 -45 cm 3 between.

[0043] In this embodiment, the parameters of the graphene powder or other conductive particles are selected as follows: resistivity not less than 2.8 x 10⁻⁶. -8 Ohm-meter (resistivity of metallic aluminum); diameter not greater than 10 micrometers, release space concentration 10%.

[0044] In this embodiment, the mass of graphene powder released is as follows: based on a release space concentration of 10% and a graphite density of 2.25 g / cm³. 3 Free up 45 cm of space 3 The required amount of graphene powder is approximately 10 grams.

[0045] like Figure 2 As shown, in this embodiment, the maximum diameter of the graphite powder is less than or equal to 1 micrometer, the particle spacing is less than 0.1 micrometer, and a 9 cubic centimeter graphite aerosol can be formed after blasting.

[0046] In summary, by arranging graphene powder packets with a burning filament and a built-in micro-explosion device between the high-voltage and low-voltage panels inside the instrument transformer, and triggering the detonation device during the test, the graphene powder is uniformly distributed between the high-voltage and low-voltage panels to form a graphene sol. Due to the extremely small gaps between the graphite particles, the breakdown distance between the high-voltage and low-voltage panels is significantly shortened. During the test, only the low-voltage port of a common short-time current test device needs to be energized to form the standard-specified arc current between the high-voltage and low-voltage panels. That is, under the premise of fully meeting the relevant national standard test requirements, the internal arc fault test can be completed using the low-voltage port of a common short-time current test device, greatly reducing the capacity and cost of the test equipment, and also significantly reducing the impact of the test equipment on the power grid during the test.

[0047] Example 3

[0048] Figure 3This is a flowchart illustrating a method for generating arc current in an arc fault testing device for an instrument transformer, as provided in Embodiment 3 of this specification. The method includes the following steps:

[0049] Step 302: Connect the high-voltage power supply to the first current conductor, connect the low-voltage power supply to the second current conductor, and connect the two ends of the short-time current test device to the first current conductor and the second current conductor respectively; arrange the low-voltage arc ignition device in the circuit formed by the high-voltage power supply, the low-voltage power supply, and the short-time current test device, including conductive particles and a filament, and connect the two ends of the filament to the high-voltage power supply and the low-voltage power supply respectively.

[0050] Step 304: Trigger the detonation device arranged inside or outside the conductive particles to make the conductive particles evenly distributed between the high voltage screen and the low voltage screen, forming a conductive particle sol.

[0051] Step 306: Start the short-time current test device to output current, causing the fuse to melt and forming a continuous test arc current between the high-voltage and low-voltage power panels.

[0052] Furthermore, prior to step 304, the following is also included:

[0053] A preset current is passed through the current conductor, and the impedance of the current transformer test circuit is measured.

[0054] Based on the impedance of the current transformer test circuit, the port voltage parameters of the short-time current test device are calculated. These port voltage parameters are used for parameter setting when starting the short-time current test device.

[0055] It should be noted that one implementation of steps 302-306 can be:

[0056] A graphene powder pack containing a filament and a built-in micro-explosion device is arranged between the high-voltage and low-voltage electrical panels inside the instrument transformer.

[0057] The impedance of the transformer test circuit is measured by the expected current, and the port voltage parameters of the short-time current test device are calculated.

[0058] Trigger the micro-explosion device to allow graphene powder to be evenly distributed between the high-voltage and low-voltage power panels to form a graphite sol.

[0059] Set the port voltage parameters of the short-time current test device, start the output current of the short-time current test device to make the fuse melt and generate a test arc current. At the same time, the graphite sol between the high-voltage and low-voltage panels can form a continuous test arc current.

[0060] After the test, observe the condition of the sample and determine what safety level the sample meets.

[0061] In summary, by arranging graphene powder packets with a burning filament and a built-in micro-explosion device between the high-voltage and low-voltage panels inside the instrument transformer, and triggering the detonation device during the test, the graphene powder is uniformly distributed between the high-voltage and low-voltage panels to form a graphene sol. Due to the extremely small gaps between the graphite particles, the breakdown distance between the high-voltage and low-voltage panels is significantly shortened. During the test, only the low-voltage port of a common short-time current test device needs to be energized to form the standard-specified arc current between the high-voltage and low-voltage panels. That is, under the premise of fully meeting the relevant national standard test requirements, the internal arc fault test can be completed using the low-voltage port of a common short-time current test device, greatly reducing the capacity and cost of the test equipment, and also significantly reducing the impact of the test equipment on the power grid during the test.

[0062] The above description is merely an embodiment of this specification and is not intended to limit this specification. Various modifications and variations can be made to this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of the claims of this specification.

Claims

1. An arc current generating device for an internal arc fault test of a transformer, characterized by The application relates to a short-time current test device for a transformer, which comprises a first current lead, a second current lead, a high-voltage electric screen and a low-voltage electric screen, a low-voltage arc ignition device and the short-time current test device. The high-voltage electric screen is connected with the first current lead, the low-voltage electric screen is connected with the second current lead, two ends of the short-time current test device are respectively connected with the first current lead and the second current lead, the low-voltage arc ignition device is arranged in a loop formed by the high-voltage electric screen, the low-voltage electric screen and the short-time current test device, and the low-voltage arc ignition device comprises conductive particles and a burning wire, and two ends of the burning wire are respectively connected with the high-voltage electric screen and the low-voltage electric screen. The low-voltage arc ignition device is used for making the conductive particles uniformly distributed between the high-voltage electric screen and the low-voltage electric screen to form a conductive particle sol by igniting the igniting device arranged inside or outside the conductive particles. The short-time current test device is used for starting and outputting current by the low-voltage port of the short-time current test device after the conductive particle sol is formed, so that the burning wire is fused, and a continuous test arc current is formed between the high-voltage electric screen and the low-voltage electric screen.

2. The apparatus of claim 1, wherein, The minimum cross section of the high-voltage electric screen and the low-voltage electric screen is determined according to the test current value in 1 second.

3. The apparatus of claim 1, wherein, The resistivity of the conductive particles is not less than 2.8 x 10 -8 Ohm-m, the diameter should be not more than 10 microns, the release space concentration should be not less than 10%.

4. The apparatus of claim 1, wherein, The conductive particles comprise graphene powder.

5. The apparatus of claim 4, wherein, The release space range of the graphene powder is 3-5 times of the through-flow cross section space of the high-voltage electric screen and the low-voltage electric screen.

6. The apparatus of claim 1, wherein, The igniting device adopts a micro explosion device arranged in the conductive particles or an external pressure release device.

7. The apparatus of claim 1, wherein, The high-voltage electric screen and the low-voltage electric screen are arranged at a place where an electric field is concentrated or insulation is weak of the transformer.

8. The apparatus of claim 1, wherein, The conductive particles and the burning wire are arranged side by side or oppositely.

9. An arc current generating method applied to the arc current generating device for the internal arc fault test of a transformer according to claim 1, characterized by, The application relates to a short-time current test device for a transformer, which comprises a first current lead, a second current lead, a high-voltage electric screen and a low-voltage electric screen, a low-voltage arc ignition device and the short-time current test device. The high-voltage electric screen is connected with the first current lead, the low-voltage electric screen is connected with the second current lead, two ends of the short-time current test device are respectively connected with the first current lead and the second current lead, the low-voltage arc ignition device is arranged in a loop formed by the high-voltage electric screen, the low-voltage electric screen and the short-time current test device, and the low-voltage arc ignition device comprises conductive particles and a burning wire, and two ends of the burning wire are respectively connected with the high-voltage electric screen and the low-voltage electric screen. The low-voltage arc ignition device is used for making the conductive particles uniformly distributed between the high-voltage electric screen and the low-voltage electric screen to form a conductive particle sol by igniting the igniting device arranged inside or outside the conductive particles. The short-time current test device is used for starting and outputting current by the low-voltage port of the short-time current test device after the conductive particle sol is formed, so that the burning wire is fused, and a continuous test arc current is formed between the high-voltage electric screen and the low-voltage electric screen. Before the igniting device arranged inside or outside the conductive particles is ignited to make the conductive particles uniformly distributed between the high-voltage electric screen and the low-voltage electric screen to form a conductive particle sol, the application further comprises the following steps:

10. The method of claim 9, wherein, A preset current is input to the current lead, and the impedance of a transformer test loop is measured; According to the impedance of the transformer test loop, the port voltage parameter of the short-time current test device is calculated, and the port voltage parameter is used for parameter setting when the short-time current test device is started. ​

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