Vacuum circuit breaker contact gap online aging device and control method

Abstract

The application discloses a vacuum circuit breaker contact gap online aging device and a control method, and relates to the technical field of power protection. The device provided by the application comprises a vacuum circuit breaker, a power taking unit, an oscillation circuit unit and a triggering unit. When the vacuum circuit breaker is in a closing operation, the power taking unit acquires electric energy, and the acquired electric energy is transmitted to the oscillation circuit unit to charge the energy storage subunit. When the vacuum circuit breaker is opened, the arc ignition mechanism is controlled to ignite and conduct the triggering gap. At this time, the circuit breaker is still in the arc burning stage, and the oscillation circuit unit is approximately in a short-circuit state, thereby generating a high-frequency oscillation current. The online aging of the vacuum circuit breaker that has been put into operation is realized, the damage of a high-energy arc to the surface morphology of electrodes in the short-circuit opening process is reduced, and the deterioration of the insulation performance of the circuit breaker is slowed down.

Description

Technical Field

[0001] This application relates to the field of power protection technology, and in particular to an online aging device and control method for the contact gap of a vacuum circuit breaker. Background Technology

[0002] Vacuum circuit breakers rely on vacuum to maintain insulation performance in the contact gap, and their insulation capacity is closely related to the microstructure of the electrode surface. To improve the insulation performance of the contact gap, the commonly used method is to age the contact gap. Aging involves using certain methods to generate an electric arc in the vacuum gap, and by controlling the characteristics of the electric arc energy and frequency, a relatively uniform ablation is produced on the contact surface, thereby removing surface defects.

[0003] Because the arc required for aging will cause the vacuum gap to conduct, current technology can only aging the vacuum circuit breaker when it leaves the factory. Once it is assembled into a vacuum circuit breaker and put into operation, it cannot be aged again. However, various operations during the operation of the vacuum circuit breaker will affect the electrode surface, which will lead to the deterioration of insulation performance and ultimately reduce the service life of the vacuum circuit breaker, affecting the stability of the power system. Summary of the Invention

[0004] This application provides an online aging device and control method for the contact gap of a vacuum circuit breaker, which solves the technical problem of insulation performance degradation of existing vacuum circuit breakers during operation.

[0005] To solve the above-mentioned technical problems, the first aspect of this application provides an online aging device for the contact gap of a vacuum circuit breaker, comprising: a vacuum circuit breaker, an energy harvesting unit, an oscillation circuit unit, and a triggering unit, wherein the vacuum circuit breaker, the oscillation circuit unit, and the triggering unit are connected in sequence to form a circuit breaker circuit;

[0006] One end of the energy harvesting unit is connected to the power line connected to the vacuum circuit breaker through a mutual inductor device to obtain electrical energy from the power line, and the other end is connected to the oscillation circuit unit.

[0007] The triggering unit has a built-in trigger gap and an arc ignition mechanism. The arc ignition mechanism is configured to ignite and conduct the trigger gap when the vacuum circuit breaker is turned off.

[0008] The oscillation circuit unit includes an energy storage subunit and an oscillation current generating subunit. The energy storage subunit is connected to the energy harvesting unit and is used to store the electrical energy acquired by the energy harvesting unit. The oscillation current generating subunit is connected to the energy storage subunit and the triggering unit respectively and is used to output a high-frequency oscillation current to the triggering unit.

[0009] Preferably, it further includes: an ignition control unit;

[0010] The ignition control unit is configured to collect electrical signal data through the mutual inductor when the vacuum circuit breaker is opened.

[0011] Calculate the zero-crossing time of the electrical signal data based on its phase.

[0012] The ignition signal transmission time is determined based on the zero-crossing time, so as to send the ignition signal to the arc ignition mechanism at the transmission time, wherein the transmission time is earlier than the zero-crossing time.

[0013] Preferably, the ignition control unit is further configured to: compare the electrical signal data collected by the mutual inductance device with a preset electrical signal threshold; when the electrical signal data exceeds the electrical signal threshold, collect the electrical signal data and determine the transmission time of the ignition signal based on the electrical signal data.

[0014] Preferably, the electrical signal data specifically includes: the secondary side output voltage of the mutual inductor and / or the loop current data of the circuit breaker circuit.

[0015] Preferably, the oscillation circuit unit is an LC oscillation circuit, the energy storage sub-unit is the energy storage capacitor in the LC oscillation circuit, and the oscillation current generating sub-unit is the oscillation inductor in the energy storage capacitor of the LC oscillation circuit.

[0016] Preferably, the energy storage capacitor is connected in series with the oscillating inductor.

[0017] Meanwhile, a second aspect of this application provides a control method for an online aging device for vacuum circuit breaker contact gaps, applied to the online aging device for vacuum circuit breaker contact gaps as provided in the first aspect of this application, comprising:

[0018] When the vacuum circuit breaker is in closed operation, it obtains electrical energy through the energy harvesting unit and transmits the electrical energy to the oscillation circuit unit to charge the energy storage subunit of the oscillation circuit unit;

[0019] When the vacuum circuit breaker is opened, the arc ignition mechanism in the control trigger unit is ignited, which makes the trigger gap open and causes the energy storage subunit to release electrical energy to the oscillation current generating subunit in the oscillation circuit unit, so that the oscillation current generating subunit generates a high-frequency oscillation current and flows through the vacuum circuit breaker.

[0020] Preferably, the arc ignition mechanism in the control triggering unit ignites the circuit to open the trigger gap, specifically including:

[0021] When the vacuum circuit breaker is opened, the ignition control unit collects electrical signal data through the mutual inductance device;

[0022] Calculate the zero-crossing time of the electrical signal data based on its phase.

[0023] Based on the zero-crossing time, the transmission time of the ignition signal is determined so as to send the ignition signal to the arc ignition mechanism at the transmission time to control the arc ignition mechanism to ignite, wherein the transmission time is earlier than the zero-crossing time.

[0024] Preferably, the transmission time is specifically between 0.5 and 2 ms before the zero-crossing time.

[0025] Preferably, before calculating the zero-crossing time of the electrical signal data based on its phase, the method further includes:

[0026] Based on the electrical signal data collected by the mutual inductance device, the electrical signal data is compared with a preset electrical signal threshold. When the electrical signal data exceeds the electrical signal threshold, the zero-crossing time of the electrical signal data is calculated based on the phase of the electrical signal data.

[0027] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0028] With the device structure provided in this application, when the vacuum circuit breaker is in closed operation, electrical energy is obtained through the energy harvesting unit and transmitted to the oscillation circuit unit to charge the energy storage subunit. When the vacuum circuit breaker is open, the arc ignition mechanism is controlled to ignite and conduct the trigger gap. At this time, the circuit breaker is still in the arc burning stage. Since the arc voltage of the vacuum arc is low, it can be approximated as a conducting state. Then, the two ends of the oscillation circuit unit are approximately in a short-circuit state, generating a high-frequency oscillating current. This realizes the online aging of the vacuum circuit breaker that has been put into operation, thereby reducing the damage to the electrode surface morphology caused by the high-energy arc during the short-circuit breaking process and slowing down the deterioration of the circuit breaker's insulation performance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of an embodiment of an online aging device for the contact gap of a vacuum circuit breaker provided in this application.

[0031] Figure 2 This is a flowchart illustrating an embodiment of a control method for an online aging device for the contact gap of a vacuum circuit breaker provided in this application.

[0032] Figure 3 This is a flowchart illustrating the control logic of the arc ignition mechanism in an embodiment of the control method for an online aging device for the contact gap of a vacuum circuit breaker provided in this application.

[0033] in, Figure 1 The accompanying figure labels are as follows:

[0034] 1. Vacuum circuit breaker; 2. Current transformer; 3. Energy harvesting unit; 4. Oscillating circuit unit; 5. Trigger unit; SG, trigger gap structure; L, oscillating inductor; C, energy storage capacitor; 6. Ignition control unit. Detailed Implementation

[0035] Vacuum circuit breakers rely on vacuum to maintain insulation in the contact gap, and their insulation capacity is closely related to the microstructure of the electrode surface. To improve the insulation performance of the contact gap, aging is often used. This involves generating an electric arc in the vacuum gap and controlling the arc energy and frequency to produce relatively uniform ablation on the contact surface, thereby removing surface defects. Since the arc required for aging causes the vacuum gap to conduct, aging can currently only be performed at the factory. Once assembled and put into operation, aging is no longer possible. However, various operations during the operation of a vacuum circuit breaker can affect the electrode surface and reduce insulation performance, especially high-current breaking. Due to the extremely high energy of the arc during breaking, severe ablation often occurs on the electrode surface, causing the insulation performance of the contact gap of existing vacuum circuit breakers to gradually decrease during operation, even producing millimeter-level macroscopic defects, ultimately leading to circuit breaker damage and affecting the stability of the power system.

[0036] In view of this, embodiments of this application provide an online aging device and control method for the contact gap of a vacuum circuit breaker, which is used to solve the technical problem of insulation performance degradation of existing vacuum circuit breakers during operation.

[0037] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] First, a detailed description of an embodiment of an online aging device for vacuum circuit breaker contact gaps provided in this application is as follows:

[0039] Please see Figure 1This embodiment provides an online aging device for the contact gap of a vacuum circuit breaker 1, including: a vacuum circuit breaker 1, an energy harvesting unit 3, an oscillation circuit unit 4, and a triggering unit 5, wherein the vacuum circuit breaker 1, the oscillation circuit unit 4, and the triggering unit 5 are connected in sequence to form a circuit breaker circuit;

[0040] One end of the energy harvesting unit 3 is connected to the power line connected to the vacuum circuit breaker 1 through a mutual inductor device to obtain electrical energy from the power line, and the other end is connected to the oscillation circuit unit 4.

[0041] The triggering unit 5 has a built-in trigger gap SG and an arc ignition mechanism. The arc ignition mechanism is configured to ignite and conduct the trigger gap SG when the vacuum circuit breaker 1 is opened.

[0042] The oscillation circuit unit 4 includes an energy storage subunit and an oscillation current generating subunit. The energy storage subunit is connected to the energy harvesting unit 3 and is used to store the electrical energy acquired by the energy harvesting unit 3. The oscillation current generating subunit is connected to the energy storage subunit and the triggering unit 5 respectively and is used to output a high-frequency oscillation current to the triggering unit 5.

[0043] It should be noted that the main structure of the device provided in this embodiment includes: a vacuum circuit breaker 1, an energy harvesting unit 3, an oscillation circuit unit 4, and a triggering unit 5, as shown below. Figure 1 As shown, the vacuum circuit breaker 1, the oscillation circuit unit 4, and the triggering unit 5 are connected in sequence to form a circuit breaker circuit. The triggering unit 5 has a built-in trigger gap SG and an arc ignition mechanism. The oscillation circuit unit 4 includes an energy storage subunit and an oscillation current generating subunit. The energy harvesting unit 3 can be connected to the circuit breaker circuit in a branch form. When the vacuum circuit breaker 1 is closed, the current will flow normally through the two ends of the circuit breaker. The energy harvesting unit 3 collects electrical energy through a mutual inductance device. The collected electrical energy is used to charge the energy storage subunit in the oscillation circuit unit 4 to store energy. The output voltage of the energy unit 3 is preferably (800, 1500] V, and the output current is preferably (0.1, 2] mA. When the circuit breaker is broken, the arc ignition mechanism in the trigger unit 5 is controlled to make the trigger gap SG ignite and conduct. Then the energy storage subunit will output electrical energy to the oscillation current generating subunit. At this time, the circuit breaker is still in the arc burning stage. Since the vacuum arc voltage is low, it can be approximately regarded as a conducting state. Then the two ends of the oscillation circuit unit 4 are approximately in a short-circuited state, generating a high-frequency oscillation current to uniformly erode the contact surface and realize online aging.

[0044] The device provided in this embodiment enables online aging of the contact gap of the vacuum circuit breaker 1 that has been put into operation, eliminating surface defects generated on the contact surface during operation and alleviating the decline in insulation performance during the operation of the circuit breaker.

[0045] In some embodiments, the device provided in this application further includes: an ignition control unit 6;

[0046] Ignition control unit 6 is configured to: collect electrical signal data through mutual inductance device when vacuum circuit breaker 1 is opened;

[0047] Calculate the zero-crossing time of the electrical signal data based on its phase.

[0048] The ignition signal transmission time is determined based on the zero-crossing time, so that the ignition signal is sent to the arc ignition mechanism at the transmission time, wherein the transmission time is earlier than the zero-crossing time.

[0049] It should be noted that, to further improve the online aging effect, this application can also add an ignition control unit 6 to the basic structure described above. This unit calculates the zero-crossing time of the electrical signal data based on the phase of the collected electrical signal data, i.e., the time corresponding to the current reaching the zero-crossing point. Based on the zero-crossing time, the ignition signal transmission time is determined, so that the ignition signal is sent to the arc ignition mechanism at the transmission time, thereby more accurately controlling the online aging execution time. By sending a signal before the current reaches the zero-crossing point to ignite the trigger gap SG, the oscillation circuit unit 4 is discharged, thereby introducing a high-frequency oscillating current and reducing the damage to the contact gap insulation performance caused by large current interruption.

[0050] Among them, such as Figure 1 As shown, in this embodiment, both the energy harvesting unit 3 and the ignition control unit 6 use mutual inductance devices to collect electrical energy or electrical signals. The mutual inductance devices can be the same mutual inductance device or different mutual inductance devices. The mutual inductance device can be a current transformer 2.

[0051] More specifically, electrical signal data may include: the secondary side output voltage of the transformer and / or the loop current data of the circuit breaker circuit.

[0052] More specifically, the ignition control unit 6 is also configured to: compare the electrical signal data collected by the mutual inductance device with a preset electrical signal threshold; when the electrical signal data exceeds the electrical signal threshold, collect the electrical signal data and determine the sending time of the ignition signal based on the electrical signal data.

[0053] It should be noted that, in this embodiment, the ignition control unit 6 reads not only the secondary side output voltage of the transformer, but also the tripping command sent by the system to the circuit breaker. The phase detection unit is normally in a locked state to reduce energy consumption. When it detects the tripping command sent by the system to the circuit breaker, it is unlocked and reads the secondary side output voltage of the transformer and / or the circuit current data of the circuit breaker. When the secondary side voltage exceeds the voltage threshold or the current flowing through the main circuit of the circuit breaker exceeds the current threshold, the phase calculation logic is activated. It starts to calculate the current phase based on the detected signal and sends an ignition signal to the trigger gap SG unit before the current crosses zero based on the phase calculation result.

[0054] It should be noted that the preferred method for determining whether the circuit breaker has interrupted a short-circuit current in this embodiment is based on the phase of the main circuit current. Generally, for vacuum circuit breakers, short-circuit currents below 10kA interruption loads are very light and do not require online aging. Online aging is only required when interrupting short-circuit currents above 10kA. Therefore, the threshold can be set to around 10kA. Since the secondary side output voltage and the main circuit current are very close in requirement of the PT, the secondary side output voltage can be used instead of the main circuit current in some embodiments, or both methods can be used together.

[0055] In some embodiments, the oscillation circuit unit is specifically an LC oscillation circuit, the energy storage sub-unit is specifically an energy storage capacitor in the LC oscillation circuit, and the oscillation current generating sub-unit is specifically an oscillation inductor in the energy storage capacitor of the LC oscillation circuit.

[0056] In some embodiments, the energy storage capacitor is connected in series with the oscillating inductor.

[0057] The energy storage capacitor C of the oscillation circuit unit is preferably (600, 2000] pF, and the inductance of the oscillation inductor L is preferably (10, 85] μH.

[0058] The device proposed in this application achieves online aging by introducing a high-frequency pulse current into the contact gap when the circuit breaker interrupts the short-circuit current. The advantages of this method include:

[0059] ① This invention solves the problem that traditional vacuum gap aging technology can only be carried out at the factory and cannot solve the problem of the decline in the insulation performance of the vacuum gap during operation; this application applies a high-frequency pulse current during each short-circuit current interruption of the vacuum circuit breaker, which is equivalent to online aging and effectively alleviates the decline in the insulation performance of the vacuum circuit breaker contact gap caused by short current interruption.

[0060] ② Currently, to address the issue of decreased insulation performance during vacuum gap operation, the common approach is to increase the rated opening distance to improve margin. However, this results in a larger contact opening distance at high voltage levels, leading to a significant increase in the overall size and cost of the circuit breaker. This application solves the problem of decreased insulation performance through online aging, which greatly reduces the rated opening distance at high voltage levels, thereby reducing the overall size and cost of the circuit breaker.

[0061] ③ Introducing a high-frequency pulse current before the short-circuit current crosses zero has the effect of delaying the arc extinction time, which effectively increases the arc extinction gap and helps to improve the high-current breaking capacity of the vacuum circuit breaker.

[0062] The above is a detailed description of an embodiment of an online aging device for vacuum circuit breaker contact gaps provided in this application. The following is a detailed description of an embodiment of a control method for an online aging device for vacuum circuit breaker contact gaps provided in this application, as detailed below:

[0063] Please see Figure 2 This embodiment provides a control method for an online aging device for vacuum circuit breaker contact gaps, applied to the online aging device for vacuum circuit breaker contact gaps as described above in this application. This control method specifically includes:

[0064] Step S1: When the vacuum circuit breaker is in closed operation, it obtains electrical energy through the energy harvesting unit and transmits the electrical energy to the oscillation circuit unit to charge the energy storage subunit of the oscillation circuit unit.

[0065] Step S2: When the vacuum circuit breaker is opened, the arc ignition mechanism in the control trigger unit is ignited to open the trigger gap and cause the energy storage subunit to release electrical energy to the oscillation current generating subunit in the oscillation circuit unit, so that the oscillation current generating subunit generates a high-frequency oscillation current and flows through the vacuum circuit breaker.

[0066] Furthermore, such as Figure 3 As shown, in step S2 of this embodiment, the arc ignition mechanism in the control trigger unit ignites the circuit to make the trigger gap open, specifically including:

[0067] Step S21: When the vacuum circuit breaker is opened, the ignition control unit collects electrical signal data through the mutual inductance device;

[0068] Step S22: Calculate the zero-crossing time of the electrical signal data based on the phase of the electrical signal data;

[0069] Step S23: Determine the sending time of the ignition signal based on the zero-crossing time, so as to send the ignition signal to the arc ignition mechanism at the sending time to control the arc ignition mechanism to ignite; wherein the sending time is earlier than the zero-crossing time.

[0070] Furthermore, the transmission time is specifically between 0.5 and 2 ms before the zero-crossing time.

[0071] Furthermore, the control method provided in this embodiment may further include the following before step S22:

[0072] Step S210: Based on the electrical signal data collected by the mutual inductance device, compare the electrical signal data with the preset electrical signal threshold. If the electrical signal data exceeds the electrical signal threshold, proceed to step S22. If it does not exceed the threshold, there is no need to execute subsequent steps. You can return to any step before step S210 or directly terminate the control process.

[0073] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0074] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0075] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An online aging device for vacuum circuit breaker contact gaps, characterized in that, include: The system includes a vacuum circuit breaker, an energy harvesting unit, an oscillation circuit unit, an ignition control unit, and a triggering unit, wherein the vacuum circuit breaker, the oscillation circuit unit, and the triggering unit are connected in sequence to form a circuit breaker circuit. One end of the energy harvesting unit is connected to the power line connected to the vacuum circuit breaker through a mutual inductor device to obtain electrical energy from the power line, and the other end is connected to the oscillation circuit unit. The triggering unit has a built-in trigger gap and an arc ignition mechanism. The arc ignition mechanism is configured to ignite and conduct the trigger gap when the vacuum circuit breaker is turned off. The oscillation circuit unit includes an energy storage subunit and an oscillation current generating subunit. The energy storage subunit is connected to the energy harvesting unit and is used to store the electrical energy acquired by the energy harvesting unit. The oscillation current generating subunit is connected to the energy storage subunit and the triggering unit respectively and is used to output a high-frequency oscillation current to the triggering unit. The ignition control unit is configured to collect electrical signal data through the mutual inductor when the vacuum circuit breaker is opened. Calculate the zero-crossing time of the electrical signal data based on its phase. The ignition signal transmission time is determined based on the zero-crossing time, so as to send the ignition signal to the arc ignition mechanism at the transmission time, wherein the transmission time is earlier than the zero-crossing time.

2. The online aging device for vacuum circuit breaker contact gaps according to claim 1, characterized in that, The ignition control unit is further configured to: compare the electrical signal data collected by the mutual inductance device with a preset electrical signal threshold; when the electrical signal data exceeds the electrical signal threshold, collect the electrical signal data and determine the ignition signal transmission time based on the electrical signal data.

3. The online aging device for vacuum circuit breaker contact gaps according to claim 1, characterized in that, The electrical signal data specifically includes: the secondary side output voltage of the mutual inductor and / or the loop current data of the circuit breaker circuit.

4. The online aging device for vacuum circuit breaker contact gaps according to claim 1, characterized in that, The oscillation circuit unit is specifically an LC oscillation circuit, the energy storage sub-unit is specifically an energy storage capacitor in the LC oscillation circuit, and the oscillation current generating sub-unit is specifically an oscillation inductor in the LC oscillation circuit.

5. The online aging device for vacuum circuit breaker contact gaps according to claim 4, characterized in that, The energy storage capacitor is connected in series with the oscillating inductor.

6. A control method for an online aging device for vacuum circuit breaker contact gaps, applied to the online aging device for vacuum circuit breaker contact gaps as described in any one of claims 1 to 5, characterized in that, include: When the vacuum circuit breaker is in closed operation, it obtains electrical energy through the energy harvesting unit and transmits the electrical energy to the oscillation circuit unit to charge the energy storage subunit of the oscillation circuit unit; When the vacuum circuit breaker is opened, the arc ignition mechanism in the control trigger unit is ignited, which makes the trigger gap open and causes the energy storage subunit to release electrical energy to the oscillation current generating subunit in the oscillation circuit unit, so that the oscillation current generating subunit generates a high-frequency oscillation current and flows through the vacuum circuit breaker. The arc ignition mechanism in the control triggering unit ignites the circuit, making the trigger gap conductive, specifically including: When the vacuum circuit breaker is opened, the ignition control unit collects electrical signal data through the mutual inductance device; Calculate the zero-crossing time of the electrical signal data based on its phase. Based on the zero-crossing time, the transmission time of the ignition signal is determined so as to send the ignition signal to the arc ignition mechanism at the transmission time to control the arc ignition mechanism to ignite, wherein the transmission time is earlier than the zero-crossing time.

7. The control method for an online aging device for vacuum circuit breaker contact gaps according to claim 6, characterized in that, The transmission time is specifically between 0.5 and 2 ms before the zero-crossing time.

8. The control method for an online aging device for vacuum circuit breaker contact gaps according to claim 6, characterized in that, Before calculating the zero-crossing time of the electrical signal data based on its phase, the following steps are also included: Based on the electrical signal data collected by the mutual inductance device, the electrical signal data is compared with a preset electrical signal threshold. When the electrical signal data exceeds the electrical signal threshold, the zero-crossing time of the electrical signal data is calculated based on the phase of the electrical signal data.

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