A device and method for detecting the anti-ablation performance of metal contacts of an on-load tap changer

Abstract

The present invention discloses a device and method for detecting the anti-ablation performance of metal contacts of a load tap changer, comprising an experimental container and a telescopic unit, wherein a metal positive electrode and a metal grounding electrode are installed in the experimental container, the metal positive electrode and the metal grounding electrode are electrically connected to a discharge circuit unit, and the discharge circuit unit is electrically connected to a charging circuit unit; the metal positive electrode and the metal grounding electrode are matched; the telescopic unit is connected to a metal slider; the telescopic unit drives the metal slider to move back and forth, so that the metal contact of the metal positive electrode and the metal grounding electrode are repeatedly turned on and off; the discharge circuit unit is electrically connected to a multi-channel oscilloscope; insulating oil for immersing the metal positive electrode, the metal grounding electrode and the metal slider is added into the experimental container. The present invention can quantitatively analyze the influence of charge release, arc average power, and arc power consumption on contact ablation, analyze the influence of arc breaking speed on contact ablation, and can also be used to quickly screen suitable materials for metal contacts of load tap changers.

Description

Technical Field

[0001] The invention belongs to the technical field of state evaluation and fault diagnosis of on-load tap changers inside oil-immersed power transformers, and in particular relates to a device and method for detecting the ablation resistance of metal contacts of on-load tap changers. Background Art

[0002] On-load tap changer is an important component of large power transformers. It balances the voltage by adjusting the internal contact position of the tap changer, avoiding large-scale voltage fluctuations at the user end, thereby enhancing the stability and reliability of the power grid.

[0003] There are many types of on-load tap changers. According to the different arc extinguishing media, they can be divided into vacuum arc extinguishing and insulating oil arc extinguishing; according to whether the switching switch has an independent oil chamber, it can be divided into combined and composite types. The present invention is applicable to on-load tap changers with arc-extinguishing metal contacts in oil, and is mainly used to study the ablation behavior of the arc on the contacts during the breaking process of the metal contacts. For combined on-load tap changers, the present invention is aimed at the switching switch responsible for completing the current breaking; for composite on-load tap changers, the selection switch and the switching switch are integrated together, and there is also arc behavior during the current breaking process. The content of the present invention is also applicable to composite tap changers. During the breaking process of the load current, arc behavior will occur, which is the simulation experiment object of this patent.

[0004] Under the action of the electric arc, the metal on the surface of the metal contact of the switch will be detached, or suspended in the surrounding insulating medium in the form of metal particles, or dissolved in the insulating oil in the form of ions. In the presence of the electric arc, some metal particles react with impurities in the insulating oil or the aging acid products of some insulating oils, and finally generate metal ions. The presence of suspended metal particles or metal ions in the transformer oil will cause great damage to the internal insulation. Under high temperature and strong electromagnetic environment, the presence of metal ions will catalyze the aging of transformer oil, and the acidic substances in the aging products of transformer oil will in turn further corrode the surface of the metal contact, which is an accumulative process that accelerates damage. For the on-load tap changer, the corrosion of the contact will increase the contact resistance on the surface and increase the relative conductive distance. In some extreme cases, the increase in the conductive distance causes the current to be interrupted prematurely when the current is disconnected, causing internal faults of the transformer. Studying the ablation of the contacts by the arc in the oil is helpful to evaluate the health of the internal contacts, facilitate the operation and maintenance personnel to formulate maintenance plans in a timely and effective manner, and facilitate the selection of appropriate switch contact materials according to their anti-ablation performance. Summary of the invention

[0005] To solve the above problems, the present invention discloses a device and method for detecting the ablation resistance of metal contacts of on-load tap changers. The present invention can quantitatively analyze the influence of charge release on contact ablation, and can also be used to quickly screen suitable materials for metal contacts of on-load tap changers.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A device for detecting the anti-ablation performance of metal contacts of an on-load tap changer comprises an experimental container 10 and a telescopic unit. A metal positive electrode 17 and a metal grounding electrode 18 are installed in the experimental container 10. The metal positive electrode 17 and the metal grounding electrode 18 are electrically connected to a discharge circuit unit, and the discharge circuit unit is electrically connected to a charging circuit unit; the metal positive electrode 17 and the metal grounding electrode 18 are matched; the telescopic unit is connected to a metal slider 23; the telescopic unit drives the metal slider 23 to move back and forth, so that the metal contact of the metal positive electrode 17 and the metal grounding electrode 18 are repeatedly turned on and off; the discharge circuit unit is electrically connected to a multi-channel oscilloscope 15; insulating oil 21 is added into the experimental container 10 to immerse the metal positive electrode 17, the metal grounding electrode 18 and the metal slider 23.

[0008] A further improvement is that the telescopic unit is a linear motor 11, a cylinder or an oil cylinder; the telescopic unit is connected to the metal slider 23 through an insulating connecting rod 12; the side wall 19 of the experimental container 10 is made of plexiglass, and the container top cover 22 of the experimental container 10 is made of a polytetrafluoroethylene plate, and the container top cover 22 is provided with a slot for the insulating connecting rod 12 to move.

[0009] As a further improvement, the charging circuit unit includes an isolation transformer 1, the isolation transformer 1 is electrically connected to a step-up transformer 2, one end of the step-up transformer 2 is connected in series with a protection resistor 3, a rectifier element 4, a capacitor charging circuit breaker 5, and one end of a power capacitor group 6, and the other end is electrically connected to the other end of the power capacitor group 6 and a metal grounding electrode 18.

[0010] As a further improvement, the discharge circuit unit includes a resistive voltage divider 7 connected in parallel with the power capacitor group 6; one end of the resistive voltage divider 7 is connected in series with a capacitor discharge circuit breaker 8, a current limiting resistor 9 and a metal positive electrode 17, and the other end is electrically connected to a metal grounding electrode 18; the resistive voltage divider 7 is electrically connected to a voltmeter 16.

[0011] As a further improvement, an inverter (24) is electrically connected between the capacitor discharge circuit breaker 8 and the current limiting resistor 9; and the multi-channel oscilloscope 15 is electrically connected to the discharge circuit unit through a current transformer 13 and a high-voltage probe 14 of the oscilloscope.

[0012] A method for detecting the ablation resistance performance of metal contacts of an on-load tap changer comprises the following steps:

[0013] Step 1: Use the above-mentioned on-load tap changer metal contact ablation resistance detection device to select the metal contact materials of the metal positive electrode 17 and the metal grounding electrode 18 respectively; place insulating oil in the experimental container 10, cover the container top cover 22, connect the current signal and high-voltage voltage signal probes of the oscilloscope 15 to the discharge circuit unit; weigh the weight of the metal contacts on the metal positive electrode 17 and the metal grounding electrode 18 respectively;

[0014] Step 2: Use a grounding rod to discharge the discharge circuit unit and the charging circuit unit of the on-load tap changer metal contact anti-ablation performance detection device. The discharge method is: use the metal joint of the grounding rod to repeatedly touch the metal part of the on-load tap changer metal contact anti-ablation performance detection device. The operator wears insulating gloves and holds the other end of the grounding rod. After the grounding discharge is completed, proceed to step 3.

[0015] Step 3: disconnect the capacitor discharge circuit breaker 8 and close the capacitor charging circuit breaker 5 to make the charging circuit conductive, turn on the power supply, observe the reading of the voltmeter 16, and after the power capacitor bank 6 reaches the predetermined charging voltage, disconnect the capacitor charging circuit breaker 5 and the power supply; calculate and obtain the corresponding charging amount of the power capacitor bank 6;

[0016] Step 4: Start the linear motor 11, the metal slider 23 starts to reciprocate above the metal electrode, and the discharge circuit breaker 8 is closed. At this time, the discharge circuit unit is started, and the current and voltage waveforms during the discharge process are recorded by the oscilloscope 15;

[0017] Step 5: When the current waveform recorded on the oscilloscope 15 is 0, it is considered that the discharge is completed; turn off the power supply of the linear motor, and put the capacitor charging circuit breaker 5 and the capacitor discharging circuit breaker 8 in the open state;

[0018] Step 6: Repeat steps 2 to 5 n times, where n is the preset number of tests;

[0019] Step 7: Use a high-precision electronic balance to weigh the mass of the metal contacts on the metal positive electrode 17 and the metal grounding electrode 18 respectively, and obtain the mass change Δm before and after the metal contact test; calculate the total charging capacity Q of the power capacitor group 6 after n tests total , then the ablation resistance Q of the metal contact based on the amount of current flow is obtained total / Δm.

[0020] Further improvement, in step 7, the total charge consumed in the arc process Q is obtained by recording the discharge process of the oscilloscope 15. arc :

[0021]

[0022] Where I(t) represents the current waveform recorded by the oscilloscope, ti1 and ti2 represent the start and end time of the i-th arc, respectively, and Q arc represents the total charge consumed during N arc processes, t represents the discharge time; the anti-ablation performance of the metal contact based on the amount of charge passed during the arc process is Q arc / Δm;

[0023] The step 8 is to calculate the accumulated arc energy loss W. total The ratio of the mass change of the metal contact before and after the test is used to obtain the anti-ablation performance of the metal contact based on the power W. total / Δm:

[0024] The current and voltage in the time interval ti1~ti2 of each arc behavior are averaged and processed using the equivalent area method, that is:

[0025]

[0026]

[0027] Average arc power within ti1~ti2:

[0028]

[0029] For N arc behaviors in a complete discharge process, the average power of the discharge is for:

[0030]

[0031] The power consumption W of the i-th arc behavior i for:

[0032]

[0033] The power consumption W of N arc behaviors in a complete discharge process is:

[0034]

[0035] The power consumption W of n complete discharge processes is accumulated to obtain the cumulative arc energy loss W total , thus obtaining the anti-ablation performance of the metal contact based on the power W total / Δm; where I(t) and U(t) represent the current waveform and voltage waveform recorded by the oscilloscope, respectively. It represents the average discharge voltage after mathematical processing. Represents the average discharge current after mathematical processing.

[0036] For further improvement, multiple identical on-load tap changer metal contact anti-ablation performance testing devices are set up, and steps 2 to 7 are repeated respectively. The current and voltage waveforms during each complete discharge process are recorded by an oscilloscope, and the number of arcs generated during the current interruption process is recorded. A set of tests is recorded as 50 complete discharges, and the total discharge amount Q is calculated. total 、Arc discharge quantity Q arc And the average discharge power is The total power consumption of the 50 discharge processes is W, and the ablation mass of the electric shock measured by a high-precision electronic balance is Δm, and the corresponding anti-ablation characteristic related parameter Q is obtained. total / Δm,Q arc / Δm, W / Δm.

[0037] It can be seen that when there is no arc process, only the anti-charge flux loss of the metal contact is compared, Q total -Q arc The larger the value of / Δm, the greater the resistance to charge flux loss.

[0038] For further improvement, when it is necessary to compare the ablation resistance of metal contacts of different materials, the ablation resistance of metal contacts of different materials is compared in pairs, and then arranged in order of size. For metal contacts of two materials, metal A and metal B, the comparison method is as follows: a set of tests is recorded as 50 complete discharges, and the total discharge amount Q corresponding to metal A and metal B is calculated. Atotal , Q Btotal , arc discharge quantity Q Aarc , Q Barc And the average discharge power is The total power consumption during 50 discharges is W A , W B The ablation mass of metal A and metal B measured by high-precision electronic balance is Δm A , Δm B , compare the Q corresponding to metal A and metal B arc The value of / Δm and W / Δm can determine the ablation resistance of metal A and metal B; arc / Δm, W / Δm ratio is larger, its anti-ablation ability is stronger, that is, for the metal material of the metal contact, the greater the arc charge and arc power consumption per unit mass loss, the stronger its ability to withstand arc is.

[0039] Further improvement, when it is necessary to determine the switching frequency according to the metal contact, the number of reciprocating movements per minute of the linear motor 11 in each on-load tap changer metal contact anti-ablation performance detection device is controlled to be different, the metal contact anti-ablation performance is compared in pairs, and then arranged in order of size to obtain the optimal switching frequency of the metal contact; for the on-load tap changer metal contact anti-ablation performance detection device in which the reciprocating numbers of the two linear motors are n1 and n2 respectively, the metal contact anti-ablation performance is compared in pairs. and The size of and size.

[0040] In fact, Q arc / Δm, W / Δm, will show some consistency in value, that is, for the two cases being compared, if the Q of a material is arc / Δm value is large, the corresponding W / Δm, will also be larger, but its physical meaning is different: Q arc / Δm represents the influence of the charge amount during arc discharge, W / Δm represents the influence of arc discharge power consumption, Represents the effect of average arc power.

[0041] Advantages of the present invention:

[0042] 1. Obtain the relevant parameters of the anti-ablation performance of the metal contacts of the on-load tap changer.

[0043] 2. The anti-corrosion performance of the metal contacts of the on-load tap changer can be quickly determined.

[0044] 3. It is convenient to quickly select the appropriate metal contact material for the on-load tap changer. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 : The present invention is divided into 4 functional blocks;

[0046] Figure 2 : The overall framework diagram of the invention device, including the circuit part and the mechanical part;

[0047] Figure 3 : The specific structure of the experimental container containing the electrodes;

[0048] Figure 4 : The conduction condition of the capacitor discharge circuit when the linear motor reciprocates;

[0049] Figure 5 : Schematic diagram of experimental device for AC arc;

[0050] Figure 6 : Schematic diagram of simplified experimental setup for AC arc. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0052] In the present invention, by replacing the experimental container containing the electrode, the material of the metal contact of the electrode is selected to compare the arc erosion resistance of the metal contact of different materials. In the present invention, the total charge amount Q of the capacitor plate can be controlled by adjusting the capacitor charging voltage. total , and the loss mass Δm of the electrode material can be obtained by a high-precision electronic balance, thereby obtaining the corresponding discharge charge Q total The ratio Q to the electrode material loss mass Δm total / Δm, as mentioned above, Q total The value of / Δm can be used to compare the ablation resistance of different metal materials.

[0053] In the present invention, the conduction and disconnection of the positive and negative contacts in the experimental container are realized by a metal slider, and the metal slider is connected to the linear motor through an insulated polytetrafluoroethylene guide rod. The reciprocating motion of the linear motor realizes the repeated movement of the metal slider between the positive and negative contacts, thereby causing the repeated conduction and disconnection between the positive and negative contacts. In this process, the opening and closing of the load current are also realized. This load current is provided by the capacitor in the discharge circuit.

[0054] In the present invention, it should be noted that the effect of a single discharge on the metal contact is negligible. Multiple interval tests are required to produce measurable differences. Taking the mass loss of electrode material as an example, it is more appropriate to test and measure the mass loss at intervals of 50 discharges.

[0055] In the present invention, the electrode material and the metal slider material in the experimental container can be different. The material between the positive and negative electrodes should be the same. The electrode metal and the metal material of the slider can be different. When the metal materials are different, the effect of electrochemical corrosion will be more significant, and additional analysis is required.

[0056] In the present invention, since the metal electrode is immersed in the insulating liquid, it is necessary to consider the influence of the metal material dissolved in the insulating liquid on the discharge process. Quantitative analysis of the concentration of metal elements in the insulating liquid can be obtained by special equipment. It is assumed that the total volume of the insulating liquid is V, and the concentration of metal elements obtained in the sampling is ρ. When the released metal particles are assumed to be uniformly distributed, the mass of the total metal particles in the oil is m2=ρV. Obviously, m1>m2. This is because the aging of the transformer oil causes some metal ions to aggregate and form sludge, which is precipitated at the bottom of the container. The formation of sludge is a very common phenomenon in the transformer oil tank. In the experiment set by this device, appropriate metal micron or nanoparticles can also be added to the insulating oil to analyze its effect on the anti-ablation performance of the metal contact. Some literature records that nanoparticles can increase the breakdown voltage of insulating oil. This device can verify whether it has an improved anti-ablation ability for contacts.

[0057] In the present invention, the number of actions of the linear stepper motor is adjustable from 0 to 120 times / minute. The action frequency set during the experiment is 60 to 120 times / minute, which is equivalent to the time of each reciprocating motion being 0.5s to 1s. The discharge circuit is a typical RC circuit, and its discharge time constant τ=RC. It is generally believed that the discharge process will end within 3τ time. Select appropriate resistance values ​​and capacitor capacitance values, such as R=100Ω, C=20000uF, and the discharge time constant at this time is τ=2s. When the frequency of the linear motor is set to 60 times / minute, the linear motor completes a telescopic operation within 1s, causing the current to be disconnected twice between the metal slider and the conductor. If the frequency is 120 times / minute, the current is disconnected 4 times between the metal slider and the conductor. Because the conducted current is from a dozen A to several dozen A, each process of disconnecting the current will produce a certain arcing effect.

[0058] In the present invention, except for the container containing the electrodes in the measuring circuit, capacitor charging circuit and capacitor discharging circuit, which needs to be specially made, all other parts can be purchased directly, and therefore do not fall within the scope of protection of this patent.

[0059] Method of using the device of the present invention:

[0060] (13.1) As it involves high voltage equipment and power capacitors, each circuit must be discharged using a grounding rod each time it is used. The discharge method is to use the metal joint of the grounding rod to repeatedly touch the metal part of the test device, and the operator wears insulating gloves and holds the other end of the grounding rod. After the grounding discharge is completed, the charging operation can be carried out.

[0061] (13.2) Place an appropriate amount of insulating oil in the electrode container and close the lid. Ensure that the metal slider (23) can reciprocate above the metal electrode. Place the current signal and high voltage signal probes of the oscilloscope in the corresponding positions.

[0062] (13.2) Charging the capacitor: First, confirm whether the two circuit breakers are in the open state at the same time. Close the circuit breaker of the open circuit so that the charging circuit is connected and the circuit breaker of the discharge circuit is still in the open state. Turn on the power supply, adjust the voltage regulator, and observe the reading of the voltmeter. After reaching the predetermined charging voltage, disconnect the circuit breaker of the charging circuit and disconnect the power supply.

[0063] (13.3) Start the linear motor, and the metal slider begins to reciprocate above the metal electrode. The discharge circuit breaker is closed, and the capacitor discharge circuit is started. The current and voltage waveforms during the discharge process are recorded by an oscilloscope.

[0064] (13.4) When the current waveform recorded on the oscilloscope is close to 0, the discharge is considered to be complete. At this time, use the grounding rod to discharge the capacitor and circuit breaker, turn off the power supply of the linear motor, and set the circuit breakers to the open state.

[0065] (13.5) Repeat the steps (13.1) to (13.4).

[0066] (13.6) During the test, record the voltage value of each capacitor charge and calculate the corresponding charge quantity. Record the typical voltage and current waveforms during each complete charge and discharge process.

[0067] (13.7) After accumulating a certain number of experiments, a high-precision electronic balance can be used to weigh the mass change of the metal contact.

[0068] Data processing method:

[0069] (14.1) A complete experimental process: including the charging and discharging process of the power capacitor bank. In a complete experimental process, the slider will work back and forth many times, and the arc will be turned on and off many times.

[0070] (14.2) The total discharge charge is the discharge on the capacitor plates, which is not equal to the discharge of the arc between the contacts. The arc process only occurs in the brief moment when the slider is opened and closed. The voltage and current waveforms in this process will be recorded by the oscilloscope.

[0071] (14.3) When it is necessary to accurately calculate the amount of charge consumed by the arc discharge during each discharge process, it is necessary to consider the integral of the current waveform recorded by the oscilloscope at this moment over time.

[0072]

[0073] Where I(t) represents the waveform recorded by the oscilloscope, ti1 and ti2 represent the start and end time of the i-th arc, respectively, and Q arcIt represents the total charge consumed in N arc processes during a single discharge. Obviously, Q total >Q arc . The arc Q arc The ratio Q to the electrode material loss mass Δm arc / Δm can be used to compare the anti-ablation performance of metal electrode materials, because Q total With Q arc There is a proportional relationship between them, so the above

[006] uses Q total / Δm can also draw similar conclusions. The advantages and disadvantages of the two are that Q total / Δm is relatively rough and can reflect the trend. arc More precision requires more cumbersome detection tools and computational processing.

[0074] (14.4) When it is necessary to accurately calculate the energy generated by the arc discharge during each discharge process, it is necessary to consider the integral of the current waveform recorded by the oscilloscope at this moment over time:

[0075]

[0076] Among them, I(t) and U(t) represent the waveforms recorded by the oscilloscope, ti1 and ti2 represent the start and end time of the i-th arc occurrence, respectively, and W arc It means that in a single discharge process, N arc processes consume energy. Because it is DC charging, the energy stored in the capacitor can be calculated:

[0077]

[0078] Among them, U C Represents the charging voltage of the capacitor. By calculating W arc / W C The ratio of can be used to obtain the statistical law of the arc discharge intensity distribution. The ratio will vary in a certain range. The selection of the upper and lower limits of this range is closely related to the contact material and the contact breaking frequency.

[0079] (14.5) In fact, it is very complicated to accurately calculate the power and power consumption of the arc, because U(t) and I(t) are not standard single functions. In order to simplify the problem, we can take the average value of the current and voltage in the time interval ti1~ti2 and use the equivalent area method to process it, that is:

[0080]

[0081]

[0082] This is a commonly used approximate processing method, which is used here to simplify the calculation of power and power consumption. At this time, the average arc power within ti1~ti2 is:

[0083]

[0084] For N arc behaviors in a complete discharge process, the average discharge power is:

[0085]

[0086] The calculation of single power consumption is:

[0087]

[0088] For N arc behaviors in a complete discharge process:

[0089]

[0090] Replacing the original irregular instantaneous power with the equivalent area method is an approximate mathematical treatment of power consumption, which can greatly simplify the problem. By calculating the accumulated arc energy loss and contact ablation mass W total / Δm, and the average arc power when the arc occurs.

[0091] Multiple identical on-load tap changer metal contact anti-ablation performance testing devices can be set up, and steps 2 to 7 can be repeated respectively. The current and voltage waveforms in each complete discharge process can be recorded by an oscilloscope, and the number of arcs generated during the current interruption process can be recorded. A set of tests is recorded as 50 complete discharges, and the total discharge amount Q is calculated. total 、Arc discharge quantity Q arc And the average discharge power is The total power consumption of the 50 discharge processes is W, and the ablation mass of the electric shock measured by a high-precision electronic balance is Δm, and the corresponding anti-ablation characteristic related parameter Q is obtained. total / Δm,Q arc / Δm, W / Δm

[0092] Take two metal contacts of different materials as an example, which are respectively denoted as metal A and metal B. A set of tests is denoted as 50 complete discharges, and the total discharge amount Q is calculated. Atotal , Q Btotal , arc discharge quantity Q Aarc , Q Barc And the average discharge power is The total power consumption during 50 discharges is W A , W B The mass of electric shock ablation measured by a high-precision electronic balance is Δm A , Δm B , comparing its key parameter Q arc The size of / Δm and W / Δm can determine the anti-ablation ability. Definition Qarc / Δm, W / Δm ratio is larger, its ablation resistance is stronger, that is, for a specific metal material of the contact, the greater the arc charge and arc power consumption per unit mass loss, the stronger its ability to withstand arc is.

[0093] In particular, for the same metal material, since the speed of the slider driven by the linear motor can be adjusted, it is equivalent to adjusting the speed of arc breaking. This equipment can also examine the ablation of electrode metal materials due to different arc breaking speeds. It is worth noting that in the two complete tests, the number of actions per minute of the linear reciprocating motor are n1 and n2 respectively. On the basis of the original, the comparison and The size of and The size can be.

[0094] In fact, Q arc / Δm, W / Δm, will show some consistency in value, that is, for the two cases being compared, if the Q of a material is arc / Δm value is large, the corresponding W / Δm, will also be larger, but its physical meaning is different: Q arc / Δm represents the influence of the charge amount during arc discharge, W / Δm represents the influence of arc discharge power consumption, Represents the effect of average arc power.

[0095] For the application scenario of the present invention under AC conditions, if it is necessary to quantitatively analyze the influence of AC arc erosion, it is necessary to add an inverter (24) to the original discharge circuit, as shown in the attached Figure 5 shown.

[0096] The present invention is applicable to a simplified case of studying the influence of AC arc, as shown in the attached figure. Figure 6 shown.

[0097] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A device for detecting the anti-ablation performance of metal contacts of an on-load tap changer, characterized in that: The invention comprises an experimental container (10) and a telescopic unit. A metal positive electrode (17) and a metal grounding electrode (18) are installed in the experimental container (10). The metal positive electrode (17) and the metal grounding electrode (18) are electrically connected to a discharge circuit unit, and the discharge circuit unit is electrically connected to a charging circuit unit. The metal positive electrode (17) and the metal grounding electrode (18) are matched. The telescopic unit is connected to a metal slider (23). The telescopic unit drives the metal slider (23) to move back and forth, so that the metal contact of the metal positive electrode (17) and the metal contact of the metal grounding electrode (18) are repeatedly turned on and off. The discharge circuit unit is electrically connected to a multi-channel oscilloscope (15). Insulating oil (21) is added into the experimental container (10) to immerse the metal positive electrode (17), the metal grounding electrode (18) and the metal slider (23).

2. The device for detecting the anti-ablation performance of metal contacts of an on-load tap changer according to claim 1, characterized in that: The telescopic unit is a linear motor (11), a cylinder or an oil cylinder; the telescopic unit is connected to a metal slider (23) via an insulating connecting rod (12); the side wall (19) of the experimental container (10) is made of organic glass, the container top cover (22) of the experimental container (10) is made of a polytetrafluoroethylene plate, and a slot is opened on the container top cover (22) for the insulating connecting rod (12) to move.

3. The device for detecting the ablation resistance of metal contacts of an on-load tap changer according to claim 1, characterized in that: The charging circuit unit comprises an isolation transformer (1), the isolation transformer (1) is electrically connected to a step-up transformer (2), one end of the step-up transformer (2) is sequentially connected in series with a protection resistor (3), a rectifier element (4), a capacitor charging circuit breaker (5), and one end of a power capacitor group (6), and the other end is electrically connected to the other end of the power capacitor group (6) and a metal grounding electrode (18).

4. The device for detecting the anti-ablation performance of metal contacts of an on-load tap changer according to claim 3, characterized in that: The discharge circuit unit comprises a resistive voltage divider (7) connected in parallel with the power capacitor group (6); one end of the resistive voltage divider (7) is sequentially connected in series with a capacitor discharge circuit breaker (8), a current limiting resistor (9) and a metal positive electrode (17), and the other end is electrically connected to a metal grounding electrode (18); the resistive voltage divider (7) is electrically connected to a voltmeter (16).

5. The device for detecting the anti-ablation performance of metal contacts of an on-load tap changer according to claim 4, characterized in that: An inverter (24) is electrically connected between the capacitor discharge circuit breaker (8) and the current limiting resistor (9); and the multi-channel oscilloscope (15) is electrically connected to the discharge circuit unit via a current transformer (13) and a high-voltage probe (14) of the oscilloscope.

6. A method for detecting the ablation resistance of metal contacts of an on-load tap changer, characterized in that: The steps include: Step 1, using the on-load tap changer metal contact anti-ablation performance detection device described in any one of claims 1-5, respectively selecting the metal contact materials of the metal positive electrode (17) and the metal grounding electrode (18); placing insulating oil in the experimental container (10), covering the container top cover (22), connecting the current signal and high-voltage voltage signal probe of the oscilloscope (15) to the discharge circuit unit; respectively weighing the weight of the metal contact on the metal positive electrode (17) and the metal grounding electrode (18); Step 2: Use a grounding rod to discharge the discharge circuit unit and the charging circuit unit of the on-load tap changer metal contact anti-ablation performance detection device. The discharge method is: use the metal joint of the grounding rod to repeatedly touch the metal part of the on-load tap changer metal contact anti-ablation performance detection device. The operator wears insulating gloves and holds the other end of the grounding rod. After the grounding discharge is completed, proceed to step 3. Step 3: disconnect the capacitor discharge circuit breaker (8) and close the capacitor charging circuit breaker (5) to make the charging circuit conductive, turn on the power supply, observe the reading of the voltmeter (16), and after the power capacitor group (6) reaches a predetermined charging voltage, disconnect the capacitor charging circuit breaker (5) and disconnect the power supply; calculate and obtain the corresponding charging amount of the power capacitor group (6); Step 4: Start the linear motor (11), the metal slider (23) starts to reciprocate above the metal electrode, and the discharge circuit breaker (8) is closed. At this time, the discharge circuit unit is started, and the current and voltage waveforms during the discharge process are recorded by the oscilloscope (15); Step 5: When the current waveform recorded on the oscilloscope (15) is 0, it is considered that the discharge is completed; turn off the power supply of the linear motor, and place the capacitor charging circuit breaker (5) and the capacitor discharging circuit breaker (8) in the open state; Step 6: Repeat steps 2 to 5 n times, where n is the preset number of tests; Step 7: Use a high-precision electronic balance to weigh the mass of the metal contact on the metal positive electrode (17) and the metal grounding electrode (18) respectively, and obtain the mass change Δm of the metal contact before and after the test; calculate the total charging quantity Q of the power capacitor group (6) after n tests total , then the ablation resistance Q of the metal contact based on the amount of current flow is obtained total / Δm.

7. The method for detecting the ablation resistance of metal contacts of an on-load tap changer according to claim 6, characterized in that: In step 7, the total amount of charge consumed during the arc process Q is obtained by recording the discharge process through the oscilloscope (15). arc : Where I(t) represents the current waveform recorded by the oscilloscope, ti1 and ti2 represent the start and end time of the i-th arc, respectively, and Q arc represents the total charge consumed during N arc processes, t represents the discharge time; the anti-ablation performance of the metal contact based on the amount of charge passed during the arc process is Q arc / Δm; The step 8 is to calculate the accumulated arc energy loss W. total The ratio of the mass change of the metal contact before and after the test is used to obtain the anti-ablation performance of the metal contact based on the power W. total / Δm: The current and voltage in the time interval ti1~ti2 of each arc behavior are averaged and processed using the equivalent area method, that is: Average arc power within ti1~ti2: For N arc behaviors in a complete discharge process, the average power of the discharge is for: The power consumption W of the i-th arc behavior i for: The power consumption W of N arc behaviors in a complete discharge process is: The power consumption W of n complete discharge processes is accumulated to obtain the cumulative arc energy loss W total , thus obtaining the anti-ablation performance of the metal contact based on the power W total / Δm; where I(t) and U(t) represent the current waveform and voltage waveform recorded by the oscilloscope, respectively. It represents the average discharge voltage after mathematical processing. Represents the average discharge current after mathematical processing.

8. The method for detecting the ablation resistance of metal contacts of an on-load tap changer according to claim 7, characterized in that: Set up multiple identical on-load tap changer metal contact anti-ablation performance testing devices, repeat steps 2 to 7 respectively, record the current and voltage waveforms during each complete discharge process through an oscilloscope, and record the number of arcs generated during the current interruption process. Record a set of tests as 50 complete discharges, and calculate the total discharge amount Q total 、Arc discharge quantity Q arc And the average discharge power is The total power consumption of the 50 discharge processes is W, and the ablation mass of the electric shock measured by a high-precision electronic balance is Δm, and the corresponding anti-ablation characteristic related parameter Q is obtained. total / Δm,Q arc / Δm, W / Δm.

9. The method for detecting the ablation resistance of metal contacts of an on-load tap changer according to claim 8, characterized in that: When it is necessary to compare the ablation resistance of metal contacts of different materials, the ablation resistance of metal contacts of different materials is compared in pairs, and then arranged in order of size. For two of the metal contacts, metal A and metal B, the comparison method is as follows: a set of tests is recorded as 50 complete discharges, and the total discharge amount Q corresponding to metal A and metal B is calculated. Atotal , Q Btotal , arc discharge quantity Q Aarc , Q Barc And the average discharge power is The total power consumption during 50 discharges is W A , W B The ablation mass of metal A and metal B measured by high-precision electronic balance is Δm A , Δm B , compare the Q corresponding to metal A and metal B arc The value of / Δm and W / Δm can determine the ablation resistance of metal A and metal B; arc / Δm, W / Δm ratio is larger, its anti-ablation ability is stronger, that is, for the metal material of the metal contact, the greater the arc charge and arc power consumption per unit mass loss, the stronger its ability to withstand arc is.

10. The method for detecting the ablation resistance of metal contacts of an on-load tap changer according to claim 9, characterized in that: When it is necessary to determine the switching frequency according to the metal contact, the number of reciprocating movements per minute of the linear motor (11) in each on-load tap changer metal contact anti-ablation performance detection device is controlled to be different, the metal contact anti-ablation performance is compared in pairs, and then arranged in order of size to obtain the optimal switching frequency of the metal contact; for the on-load tap changer metal contact anti-ablation performance detection device in which the number of reciprocating movements of the two linear motors is n1 and n2 respectively, the metal contact anti-ablation performance is compared in pairs, and the metal contact anti-ablation performance is compared in order of size. and The size of and size.

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