A CT power supply device, power supply method, fusion terminal and fuse

Abstract

The present invention discloses a CT power supply device, a power supply method, a fusion terminal, and a fuse, relating to the field of wireless power distribution technology. The CT power supply device includes a current transformer, which includes a first current transformer and a second current transformer; both the first current transformer and the second current transformer are provided with an iron core and a secondary winding; the secondary windings of the two are connected in series via a second conductor; the iron core of the first current transformer is a silicon steel sheet iron core, and the iron core of the second current transformer is a Permalloy iron core; the device also includes a first conductor, on which a first switch is connected in series; a fourth conductor, on which a third switch is connected in series; and a control module. The power supply method is implemented based on the power supply device, and the fusion terminal and the fuse both include the power supply device. This solution can effectively broaden the current range of the primary side of the CT power supply, achieve energy acquisition over a wide range, and has the characteristics of good economy and reliable performance.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power distribution, and in particular to a CT power supply device, a power supply method, a fusion terminal and a fuse. Background Art

[0002] A CT power supply (CT induction power supply) device uses a CT (current transformer) installed on a power line to generate power through the principle of electromagnetic induction. The CT power supply also includes a power conversion module. The CT generates an induced voltage on its secondary side by sensing the magnetic field generated by the current in the power line. The power conversion module converts the electrical energy obtained by the CT into direct current (DC) of the required voltage. CT power supply converts the current energy in the conductor into electrical energy that can be used by low-voltage electronic equipment. Compared to battery and solar power supply, CT power supply is maintenance-free, highly environmentally adaptable, and easy to install. Therefore, this power supply method is widely used in high-voltage transmission and distribution and smart grid fields, effectively solving power supply problems in areas where conventional power supply methods are lacking.

[0003] In the existing technology, the working mode of the CT power supply system is: based on the alternating current of the conductor (primary side), the magnetic flux of the iron core in the CT changes, the induced voltage is formed on the secondary side, the rectifier and voltage stabilization circuit works and outputs stable direct current, directly supplies power to the load or stores it in the energy storage element (capacitor or battery). Relevant existing technologies include the technical solution provided by patent application number CN202111176600.X (Name: A high-voltage cable wireless power transmission module optimization method and CT power supply device).

[0004] Taking power drawn from a 10kV AC line as an example, in the above process, factors that affect the CT's effective power draw include:

[0005] When the primary side current is too small, the induced voltage is insufficient and cannot reach the critical voltage value for rectification start of the subsequent power conversion module, causing the power circuit to fail to work;

[0006] When the primary side current is too large, the iron core becomes magnetically saturated, causing the induced voltage to drop suddenly, resulting in irreversible damage or even direct destruction of the device.

[0007] CT power supply technology is crucial to ensuring the stable operation of the smart grid. In order to make CT power supply technology serve the power grid more reliably, it is necessary to further optimize CT power supply technology. Summary of the Invention

[0008] In response to the above-mentioned technical problem of further optimizing CT power supply technology, the present invention provides a CT power supply device, a power supply method, a fusion terminal and a fuse. This solution can effectively broaden the current range of the primary side of the CT power supply, realize energy acquisition in a wide range, and has the characteristics of good economy and reliable performance.

[0009] In response to the above problems, the present invention provides a CT power supply device, power supply method, fusion terminal and fuse to solve the problems through the following technical points: a CT power supply device includes a current transformer, and the current transformer includes a first current transformer and a second current transformer;

[0010] Both the first current transformer and the second current transformer are provided with an iron core and a secondary winding;

[0011] The two secondary windings are connected in series via a second wire;

[0012] The iron core of the first current transformer is a silicon steel sheet iron core, and the iron core of the second current transformer is a Permalloy iron core;

[0013] The invention also includes a first wire having two ends connected to different ends of the secondary winding on the first current transformer, and a first switch is connected in series with the first wire;

[0014] The device further comprises a fourth wire having two ends connected to different ends of the secondary winding on the second current transformer, wherein the fourth wire is connected in series with a third switch;

[0015] It also includes a control module, which is used to collect the current value of the secondary winding on the second current transformer and control the on-off state of the first switch and the third switch based on the current value.

[0016] It is easy to understand that the secondary winding is an induction coil on the iron core, and the structure formed by the two secondary windings connected in series is the secondary coil output end of the current transformer. Different from the prior art, this solution is configured to include a first current transformer and a second current transformer by setting the current transformer to include a first current transformer and a second current transformer, the first current transformer adopts a silicon steel sheet iron core, and the second current transformer adopts a Permalloy iron core, and is configured to include a first wire and a fourth wire, and the corresponding wires are provided with a first switch and a third switch, and also includes a control module, the control module is used to control the on and off state of the corresponding switch to adjust the way in which the power taking device takes power from the transmission cable, so as to broaden the current range of the primary side of the CT power taking and achieve energy acquisition in a wide range. At the same time, it has the purpose of good economy and reliable performance. Specifically:

[0017] For the iron core using conventional silicon steel sheets in the power taking device, when the current of the iron core is small in the busbar (transmission cable (usually considered to be one turn of the primary winding) or the primary winding (according to the required number of turns, such a primary winding needs to be connected in series on the transmission cable)), due to the magnetic permeability and hysteresis loss of the iron core, a large amount of energy is required to establish the magnetic field (the magnetic flux of the iron core is small), resulting in an excessive proportion of its excitation electromotive force. When the induced voltage of the secondary winding cannot reach the critical voltage value for the start of the post-stage rectification, the power taking circuit cannot work, and the power taking device cannot output energy when the busbar current is small, resulting in power taking failure. For the iron core using Permalloy, it has very excellent magnetic permeability performance compared to the iron core of silicon steel sheets, and can effectively take power when the busbar current is small, but due to its saturation And the characteristics of small magnetic density, if the current of the busbar is unstable, when the current value is large, large current magnetic saturation will occur on the core. Since the magnetic flux can no longer increase with the increase of current, it will cause problems such as increased hysteresis loss and eddy current loss. In severe cases, it will cause irreversible damage such as insulation breakdown. At the same time, since Permalloy also has the characteristics of high cost, such as using a larger core area, a longer core magnetic circuit, and a smaller energy output to meet the requirement that the saturation state will not be reached within the full range of the Permalloy core, the implementation cost is high and has the risk of instability. Therefore, the use of Permalloy core may cause thermal runaway of the core, causing irreversible damage to the degradation of the core performance, and continuous thermal runaway will cause insulation failure between high and low voltages, resulting in a short circuit. At the same time, the Permalloy core also has the characteristics of high cost.

[0018] Based on the characteristics of different types of iron cores in the above current transformers, this solution provides the power-taking device as described above. In specific applications, the power-taking device is configured on the transmission cable and draws power from the transmission cable based on the principle of electromagnetic induction. The control module determines the current value on the transmission cable based on the collected current value, and controls the on-off state of the first switch and the third switch based on the current value determination result. When the current value on the transmission cable is less than the first set threshold, the first switch is closed and the third switch is opened. In this state, the first current transformer is isolated from the power-taking circuit and is powered by the second current transformer. After the isolation is completed, the secondary side of the first current transformer is closed. The winding is short-circuited by the first conductor, so the first current transformer can be effectively avoided from causing a decrease in power extraction efficiency. It is easy to understand that the first set threshold is the boundary value at which the current value on the transmission cable is identified as a small current. When setting the first set threshold, it is necessary to set it according to the design parameters of the first current transformer and the second current transformer (for example, considering the cost of the iron core on the second current transformer, when the cross-sectional area of ​​the iron core is larger, it is less likely to be saturated. At this time, the value of the first set threshold can be appropriately increased. Conversely, when the cross-sectional area is smaller, the value of the first set threshold needs to be set to a smaller value); when the current value on the transmission cable is greater than Or when it is equal to the first set threshold and less than the second set threshold, power is taken by any of the following methods: the first switch is closed, the third switch is disconnected, and power is taken by the second current transformer; the first switch is disconnected, the third switch is disconnected, and power is taken by the first current transformer and the second current transformer. The above first set threshold is less than the second set threshold, that is, when it is detected that the current value on the transmission cable is in the range of two set thresholds, power is still only taken by the second current transformer or the first current transformer and the second current transformer are used to take power at the same time. Both of the above methods are: the iron core of the second current transformer has not undergone magnetic saturation. The second method is that under this current value, the first A current transformer can draw power normally to ensure the power supply of the current transformer; when the current value on the transmission cable is greater than or equal to the second set threshold, the first switch is disconnected and the third switch is closed, and the first current transformer draws power. That is, when it is detected that the current value on the transmission cable is greater than or equal to the second set threshold, the first current transformer can draw power normally. To protect the second current transformer, the second current transformer is isolated from the power supply circuit by short-circuiting the output end of the second current transformer. For the second current transformer, since the magnetic flux on the iron core is clamped within a safe value at this time, irreversible degradation of the iron core can be effectively avoided.

[0019] In summary, this solution is based on the characteristics that silicon steel sheets and permalloy have different energies required to establish a magnetic field in the core when used as the core of the current transformer, and the primary side current has obvious differences when the core is magnetically saturated. It provides a technical solution that uses a second current transformer in the small current range, uses the second current transformer to draw power in the medium current range, or uses the first current transformer and the second current transformer to draw power at the same time, and uses the first current transformer to draw power in the large current range (the above division of the small current range, medium current range, and large current range is based on the first set threshold and the second set threshold as the dividing boundary). This solution can effectively broaden the bus / primary side current range applicable to the current transformer while protecting the current transformer itself, thereby realizing wide-range CT power supply.

[0020] At the same time, the structural form of the corresponding power supply line can effectively guarantee the power supply power under the power supply mode of the second current transformer: from a cost perspective, the second current transformer using a Permalloy iron core is generally only set to an iron core with a smaller cross-sectional area, so the power supply power of the second current transformer is relatively small. If the secondary winding of the first current transformer is connected in series to the power supply line in this state, it will have a significant impact on the power supply power.

[0021] In addition, as a person skilled in the art knows, during the power-drawing process, the dynamic condition that determines whether magnetic saturation occurs on the corresponding iron core is the current on the transmission cable / primary winding. In the existing current transformer application technology, the magnitude of this current has a clear correlation with the current value on the secondary winding. This solution is based on the use of a Permalloy iron core in the second current transformer, which has the characteristics of high sensitivity and high response to the current on the transmission cable / primary winding. The current value of the secondary winding is used as the control signal of the current transformer power-drawing mode, which not only makes the power-drawing device have complete functions (no longer requires a separate measuring device for measuring the current on the transmission cable), but also has the characteristic of high reliability in switching the power-drawing mode.

[0022] In addition, this solution includes current transformers with two types of cores, silicon steel sheets and Permalloy. Corresponding to distribution network monitoring and control equipment, even if there is only a small current on the transmission cable, the energy used by the second current transformer can be used to maintain basic functions such as the online status of these devices. For example, for the data processing edge computing function of the fusion terminal when responding to data reporting, and the driving mechanism action function when the fuse performs opening and closing actions, the energy supply of high-energy-consuming components such as the corresponding processor and driving mechanism can be obtained through the first current transformer and stored in the energy storage device. That is, even if the energy storage device such as capacitors and batteries has increased in service life and its capacity has decayed and the first current transformer cannot obtain electricity normally, the electricity collected by the first current transformer can be used to maintain the online function, data viewing function and other communication functions of the distribution network equipment.

[0023] In addition, if only considering the power supply under the low current state of the transmission cable, thanks to the high saturation magnetic density and low loss characteristics of the nanocrystalline iron core, when not pursuing power supply under the smaller transmission cable current, the alternative to the iron core on the second current transformer can be a nanocrystalline iron core. The nanocrystalline iron core can realize power supply under the low current state of the transmission line while not easily forming a magnetic saturation state. However, when considering obtaining the current value, since nanocrystals are more sensitive to mechanical stress than Permalloy, a possible problem is that the nanocrystalline iron core will have a continuous drift problem when used for current value measurement, resulting in uncontrollable stability and accuracy of current value acquisition. With the development of nanocrystalline material technology and iron core assembly technology, nanocrystalline iron cores with stable performance should be considered as an equivalent solution to Permalloy iron cores.

[0024] A further technical solution of the power taking device is:

[0025] The device further comprises a third wire having two ends connected to different ends of the secondary winding of the second current transformer, wherein the third wire is connected in series with a second switch and a resistor;

[0026] The invention also includes a fourth switch, which, when the second switch is closed, acts as an isolating switch for the loop formed by the secondary winding on the second current transformer and the third conductor and the first current transformer, thereby preventing the current generated by the first current transformer from flowing through the resistor;

[0027] The on / off states of the fourth switch and the second switch are both controlled by a control module, and the control module collects the current value of the secondary winding on the second current transformer by measuring the voltage value across the resistor.

[0028] The above scheme further illustrates the structure of the second current transformer. Specifically, when the second current transformer needs to draw power, the third switch and the second switch are disconnected, and the fourth switch is closed. When the current value needs to be obtained, the third switch and the fourth switch are disconnected, and the second switch is closed. That is, the second current transformer can be controlled to switch between the following three states during its use: power-drawing state, current value collection state, non-power-drawing state, and non-current value collection state (for example, the third switch is closed to isolate the second current transformer from the power-drawing circuit, and the second switch is in the disconnected state). In the above scheme, the annular loop is the current value collection loop, and the fourth switch is provided to perform an isolation function to prevent the current generated by the first current transformer from affecting the current value collection accuracy. The on-off states of the fourth switch and the second switch are set to be controlled by the control module. In this way, the control module can determine whether the second current transformer needs to draw energy based on the current value of the transmission line currently detected. When necessary, the current value change trend of the transmission line can be predicted based on the current value on the current transmission line, so as to adjust the power-drawing cycle and the collection cycle of the second current transformer as needed. For example, when the current value of the transmission line is small, it means that the current magnetic saturation margin of the Permalloy core is large. At this time, the power-drawing cycle can be divided into a longer period and the collection cycle can be divided into a shorter period. Under the premise of ensuring the safety of the use of the second current transformer, the second current transformer can be used to draw energy as much as possible; when the current value of the transmission line increases, it means that the current magnetic saturation margin of the Permalloy core is small. At this time, the power-drawing cycle can be divided into a shorter period and the collection cycle can be divided into a longer period. The current value changes are collected at a higher frequency, and the safety of the use of the second current transformer is ensured by sacrificing the power.

[0029] In a specific implementation, if the first terminal of the secondary winding of the second current transformer is connected in series with the secondary winding of the first current transformer via the second wire, the fourth switch can be connected in series with the first terminal. Of course, the fourth switch can also be provided at the terminal on the other side of the secondary winding of the second current transformer. The third wire and the fourth wire are connected in parallel with the terminals at both ends of the secondary winding of the second current transformer.

[0030] The first current transformer and the second current transformer are both configured with a primary winding, and the primary windings of the two are connected in series.

[0031] The above solution is: primary windings are configured in both the second current transformer and the first current transformer. In such an application, the primary windings of each need to be connected in series in the transmission cable, that is, the power-taking device needs to be connected in series on the transmission cable. Compared with traditional applications, this solution can flexibly adjust the number of turns of the primary winding so that the power-taking device has targeted power-taking performance and current value measurement performance.

[0032] Both the first current transformer and the second current transformer use a transmission cable as a primary side winding.

[0033] The above solution is: use the transmission cable as a primary side winding with one turn. This application method can complete the configuration of the power taking device on the transmission cable without disconnecting the transmission cable, which is in line with the installation characteristics of general power taking devices.

[0034] It also includes a rectifier module and an energy storage device. The output end of the current transformer is connected to the AC input end of the rectifier module, and the energy storage device is connected to the DC output end of the rectifier module. The rectifier module is used to convert the AC current obtained by the current transformer into DC power of a set voltage and charge the energy storage device.

[0035] The above solution is: the rectifier module acts as a current conversion module, converts the electric energy obtained by the current transformer into electric energy with set parameters and stores it in an energy storage device, so that the power consumption of the corresponding distribution network equipment is not limited to the output power of the current power-taking device. The energy storage device is a capacitor or a battery.

[0036] This solution also relates to a CT power supply method, which is implemented based on the power supply device described in any one of the above. The power supply device is configured on a transmission cable and draws power from the transmission cable based on the principle of electromagnetic induction.

[0037] The control module determines the current value on the transmission cable according to the collected current value, and controls the on / off state of the first switch and the third switch according to the current value determination result;

[0038] When the current value on the transmission cable is less than the first set threshold, the first switch is closed, the third switch is opened, and the second current transformer draws power;

[0039] When the current value on the transmission cable is greater than or equal to the first set threshold and less than the second set threshold, power is drawn in any of the following ways:

[0040] The first switch is closed, the third switch is opened, and the power is taken from the second current transformer;

[0041] The first switch is disconnected, the third switch is disconnected, and power is obtained from the first current transformer and the second current transformer;

[0042] When the current value on the transmission cable is greater than or equal to the second set threshold, the first switch is opened, the third switch is closed, and power is taken from the first current transformer;

[0043] The first set threshold is smaller than the second set threshold.

[0044] The above power supply method is based on the power supply device, and the current value determination result is the current value result on the transmission cable obtained by the ampere-turn balance principle calculation model based on the current value of the secondary winding on the second current transformer. In summary, this method can effectively broaden the busbar / primary side current range applicable to the current transformer while protecting the current transformer itself, and realize wide-range CT power supply; this solution also has the characteristics of high power supply efficiency; this solution has both current value measurement and power supply functions, and the reliability of power supply mode switching is high; under low current conditions on the transmission cable, the basic functions of the distribution network equipment can be maintained; in this solution, the first current transformer and the second current transformer are powered under different working conditions. While meeting the reliable power supply under low current conditions of the transmission line, the first current transformer with lower setting cost is used to meet the power supply needs under normal circumstances, so that this solution also has the characteristics of good economic use.

[0045] In specific implementation, taking into account the power and cost of the power-taking device, for example, for a 10kV transmission line, the first set threshold is set to 0.5A~1A, and the second set threshold is set to 5A~8A. Under this setting, when the core cost is controllable, according to the current value of the 10kV line under normal circumstances, the current transformer only needs to draw power through the first current transformer under the line operating conditions, and the second current transformer user can deal with simple functions such as online distribution equipment in extreme situations.

[0046] A further technical solution of the power extraction method is:

[0047] When the current value on the transmission cable is less than the first set threshold, the control module executes: using the first sampling frequency to collect the current value of the secondary winding on the second current transformer;

[0048] When the current value on the transmission cable is greater than or equal to the first set threshold and less than the second set threshold, the control module executes: using the second sampling frequency to collect the current value of the secondary winding on the second current transformer;

[0049] The first sampling frequency is lower than the second sampling frequency;

[0050] After the control module collects the current value of the secondary winding on the second current transformer, it calculates the current value on the transmission cable, compares the calculation result with the first set threshold and the second set threshold, and adjusts the way in which the power taking device takes power from the transmission cable according to the comparison result.

[0051] In the above scheme, the current value on the transmission cable is the current value on the transmission cable obtained by calculation after measuring the current value of the secondary winding of the second current transformer. Under non-accident conditions, this current value can most accurately reflect the current situation on the current transmission cable. In this scheme, different sampling frequencies are configured for current value acquisition based on the calculation results of the current value on the transmission cable, which is used to deal with: when it is necessary to use the second current transformer to draw power, according to the current value judgment result on the transmission cable, it is decided to sample the current value according to the first sampling frequency and the second sampling frequency, and set the first sampling frequency Lower than the second sampling frequency. In this way, when the current value is less than the first set threshold value, a lower sampling frequency is used to sample the current value. This application is used to optimize the duration of the power-taking cycle of the second current transformer and reduce the power consumption caused by the current value sampling calculation. When the current value fluctuates between the first set threshold value and the second set threshold value, it means that the current value on the current transmission line is closer to the state that makes the Permalloy core reach magnetic saturation. The second sampling frequency is used for sampling, and the power-taking mode is quickly switched at the expense of power consumption and power-taking time, so as to provide better magnetic saturation protection for the second current transformer.

[0052] The power extraction device is the power extraction device as described above including the fourth switch, the third wire, the second switch and the resistor;

[0053] When power is taken from the second current transformer, the second switch is opened and the fourth switch is closed. When the control module collects the current value, the control module adjusts the power supply and collection period according to the first set threshold value. The current value is collected during the collection period. During the collection period, the second switch is closed and the fourth switch is opened.

[0054] When power is drawn from the first current transformer and the second current transformer, the second switch is opened and the fourth switch is closed. When the control module collects current values, the control module adjusts the power drawing and collection period according to the second set threshold value. The current value is collected during the collection period. During the collection period, the second switch is closed and the fourth switch is opened.

[0055] When power is taken from the first current transformer, the second switch is closed and the fourth switch is opened.

[0056] The above scheme is that, based on the structural setting of the specific current value acquisition structure, the control module realizes the method of switching the power-taking mode of the power-taking device, the power-taking of the second current transformer, and the switching of the acquisition cycle according to the current value on the current transmission line. In the specific implementation, if the second current transformer is currently executing power-taking, it can be set to a power-taking cycle of 100ms continuously. After the power-taking cycle is completed, a collection cycle of 20ms is executed. During the collection cycle, the current value of the set number is collected; when the first current transformer and the second current transformer are used for power-taking, the current value on the current transmission cable is closer to the current that causes the magnetic saturation of the Permalloy core. The power-taking cycle can be set to a continuous 40ms. After the power-taking cycle is completed, a collection cycle of 40ms is executed. During the collection cycle, the current value of the set number is collected. When the first current transformer is used for power-taking, the second current transformer is disconnected from the power-taking circuit under the action of the relevant switch and maintains the closed state of the ring loop. At this time, the second current transformer can be used to complete the current value collection at any time. For those skilled in the art, the above-mentioned settings of the cycle duration are only examples, and those skilled in the art may adopt other duration values ​​according to the performance of the corresponding current transformer and the general variation law of the current on the transmission cable.

[0057] The following provides specific applications of two power-taking devices. Fusion terminals and fuses are two important distribution network devices. The power-taking devices are used to maintain the short-term high-energy-consuming working power supply requirements required by the fusion terminals and fuses, as well as the online power supply requirements of equipment in extreme situations (after the energy storage device is damaged or its performance deteriorates).

[0058] The present solution also relates to a converged terminal, comprising a data processing module and a power supply module for providing electrical energy to the data processing module, wherein the power supply module comprises a power extraction device as described in any one of the above.

[0059] The present solution also relates to a fuse, comprising a switch element for controlling the on-off state of a circuit and a driving mechanism for driving the switch element, and also comprising a power supply module for providing electrical energy to the driving mechanism, wherein the power supply module comprises a power extraction device as described in any one of the above items.

[0060] The present invention has the following beneficial effects:

[0061] This solution can effectively expand the busbar / primary-side current range applicable to the current transformer while protecting the current transformer itself, enabling wide-range CT power supply. This solution also has the characteristics of high power supply efficiency. This solution has both current value measurement and power supply functions, and the reliability of power supply mode switching is high. Under low current conditions on the transmission cable, this solution can maintain the basic functions of the distribution network equipment. This solution is also economical to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic diagram of the circuit principle of a specific embodiment of the CT power supply device described in this solution.

[0063] The figure marks in the accompanying drawings are: 1. transmission cable, 2. primary winding, 3. iron core, 4. secondary winding, 5. first conductor, 6. first switch, 7. second conductor, 8. control module, 9. rectifier module, 10. energy storage device, 11. second current transformer, 12. third conductor, 13. second switch, 14. resistor, 15. third switch, 16. fourth switch, 17. first current transformer, 18. fourth conductor. DETAILED DESCRIPTION

[0064] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments:

[0065] Example 1:

[0066] like Figure 1 As shown, a CT power supply device includes a current transformer, wherein the current transformer includes a first current transformer 17 and a second current transformer 11;

[0067] Both the first current transformer 17 and the second current transformer 11 are provided with an iron core 3 and a secondary winding 4;

[0068] The two secondary windings 4 are connected in series via a second conductor 7;

[0069] The iron core 3 of the first current transformer 17 is a silicon steel sheet iron core, and the iron core 3 of the second current transformer 11 is a Permalloy iron core;

[0070] The first conductor 5 has two ends connected to different ends of the secondary winding 4 on the first current transformer 17, and a first switch 6 is connected in series with the first conductor 5;

[0071] The device further includes a fourth wire 18 having two ends connected to different ends of the secondary winding 4 on the second current transformer 11, and a third switch 15 is connected in series to the fourth wire 18;

[0072] The system further includes a control module 8 for collecting the current value of the secondary winding 4 on the second current transformer 11 and controlling the on / off states of the first switch 6 and the third switch 15 based on the current value.

[0073] It is easy to understand that the secondary winding 4 is an induction coil on the iron core 3, and the structure formed by the two secondary windings 4 connected in series is the secondary coil output end of the current transformer. Different from the prior art, this solution is configured as a current transformer including a first current transformer 17 and a second current transformer 11, the first current transformer 17 adopts a silicon steel sheet iron core, and the second current transformer 11 adopts a permalloy iron core, and is configured to include a first wire 5 and a fourth wire 18, and the corresponding wires are provided with a first switch 6 and a third switch 15, and also includes a control module 8, the control module 8 is used to control the on-off state of the corresponding switch to adjust the way in which the power taking device takes power from the transmission cable 1, so as to broaden the current range of the primary side of the CT power taking and achieve energy acquisition in a wide range. At the same time, it has the purpose of good economy and reliable performance. Specifically:

[0074] For the iron core 3 using conventional silicon steel sheets on the power taking device, since the iron core 3 has a relatively small current in the busbar (transmission cable 1 (usually considered to be one turn of the primary winding 2) or the primary winding 2 (according to the required number of turns, such a primary winding 2 needs to be connected in series with the transmission cable 1)), due to the magnetic permeability and hysteresis loss of the iron core 3, a large amount of energy needs to be consumed to establish the magnetic field (the magnetic flux of the iron core 3 is small), resulting in an excessive proportion of its excitation electromotive force. When the induced voltage of the secondary winding 4 cannot reach the critical voltage value for starting the post-stage rectification, the power taking circuit cannot work, and the power taking device cannot output energy when the busbar current is small, resulting in a phenomenon of power taking failure. For the iron core 3 using Permalloy, it has very excellent magnetic permeability performance compared to the iron core 3 made of silicon steel sheets, and can effectively take power when the busbar current is relatively small, but due to It has the characteristic of small saturation magnetic density. If the current of the busbar is unstable, when the current value is large, a large current magnetic saturation phenomenon will occur on the iron core 3. Since the magnetic flux can no longer increase with the increase of current, it causes problems such as increased hysteresis loss and increased eddy current loss. In severe cases, it causes irreversible damage such as insulation breakdown. At the same time, since Permalloy also has the characteristic of high cost, such as using a larger iron core area, a longer iron core magnetic circuit, and a smaller energy output to meet the requirement of not reaching a saturation state within the full range of the Permalloy iron core, the implementation cost is high and there is a risk of instability. Therefore, when using the Permalloy iron core, it may cause thermal runaway of the iron core 3, causing irreversible damage to the performance degradation of the iron core 3, and continuous thermal runaway will cause insulation failure between high and low voltages, resulting in a short circuit. At the same time, the Permalloy iron core 3 also has the characteristic of high cost.

[0075] Based on the characteristics of the different types of iron cores 3 in the above current transformers, this solution provides a power-taking device as described above. When used specifically, the power-taking device is configured on the transmission cable 1, and draws power from the transmission cable 1 based on the principle of electromagnetic induction; wherein, the control module 8 determines the current value on the transmission cable 1 according to the collected current value, and controls the on-off state of the first switch 6 and the third switch 15 according to the current value determination result; when the current value on the transmission cable 1 is less than the first set threshold value, the first switch 6 is closed and the third switch 15 is disconnected. In this state, the first current transformer 17 is isolated from the power-taking circuit and is powered by the second current transformer 11. After the isolation is completed, the secondary winding 4 of the first current transformer 17 is short-circuited by the first wire 5, so it can be Effectively avoid the first current transformer 17 causing a decrease in power supply efficiency. It is easy to understand that the first set threshold is the boundary value at which the current value on the transmission cable 1 is identified as a small current. When setting the first set threshold, it is necessary to set it according to the design parameters of the first current transformer 17 and the second current transformer 11 (for example, considering the cost of the iron core 3 on the second current transformer 11, when the cross-sectional area of ​​the iron core 3 is larger, it is less likely to be saturated. At this time, the value of the first set threshold can be appropriately increased. Conversely, when the cross-sectional area is smaller, the value of the first set threshold needs to be set to a smaller value). When the current value on the transmission cable 1 is greater than or equal to the first set threshold and less than the second set threshold, power is taken in any of the following ways: The first switch 6 is closed, the third switch 15 is disconnected, and the second current transformer 11 draws power; the first switch 6 is disconnected, the third switch 15 is disconnected, and the first current transformer 17 and the second current transformer 11 draw power. The above first set threshold is less than the second set threshold, that is, when it is detected that the current value on the transmission cable 1 is within the two set threshold intervals, only the second current transformer 11 is still used to draw power, or the first current transformer 17 and the second current transformer 11 are used to draw power at the same time. Both of the above methods are: the iron core 3 of the second current transformer 11 does not undergo magnetic saturation. The second method is that under this current value, the first current transformer 17 can draw power normally to ensure the power supply power of the current transformer; when the current value on the transmission cable 1 is greater than Or equal to the second set threshold, the first switch 6 is disconnected, the third switch 15 is closed, and power is taken from the first current transformer 17. That is, when it is detected that the current value on the transmission cable 1 is greater than or equal to the second set threshold, the first current transformer 17 can take power normally. In order to protect the second current transformer 11, the second current transformer 11 is isolated from the power supply circuit by short-circuiting the output end of the second current transformer 11. For the second current transformer 11, since the magnetic flux on the core 3 is clamped within the safety value at this time (the secondary winding after being short-circuited forms a pure current transformer, and the reverse magnetic potential established by the secondary winding current causes the net magnetic potential of the core to be clamped within the linear region), the irreversible degradation of the core 3 can be effectively avoided.

[0076] In summary, this solution is based on the characteristics that silicon steel sheets and permalloy have different energies required to establish a magnetic field in the core 3 when used as the current transformer core 3, and the primary side current has obvious differences when magnetic saturation of the core 3 occurs. It provides a technical solution that uses the second current transformer 11 in the small current range, uses the second current transformer 11 in the medium current range to draw power, or uses the first current transformer 17 and the second current transformer 11 for power at the same time, and uses the first current transformer 17 for power in the large current range (the above division of the small current range, medium current range, and large current range is based on the first set threshold and the second set threshold as the dividing boundary). This solution can effectively broaden the bus / primary side current range applicable to the current transformer while protecting the current transformer itself, thereby realizing wide-range CT power supply.

[0077] At the same time, the structural form of the corresponding power supply circuit can effectively guarantee the power supply power of the second current transformer 11 under the power supply mode: from a cost perspective, the second current transformer 11 using a Permalloy core is generally only set to a Permalloy core with a smaller cross-sectional area and a longer magnetic circuit, so the power supply power of the second current transformer 11 is relatively small. If the secondary side winding 4 of the first current transformer 17 is connected in series to the power supply circuit in this state, it will have a significant impact on the power supply power.

[0078] In addition, as a person skilled in the art knows, during the power-drawing process, the dynamic condition that determines whether magnetic saturation occurs on the corresponding iron core 3 is the current on the transmission cable 1 / primary winding 2. In the existing current transformer application technology, the magnitude of this current has a clear correlation with the current value on the secondary winding 4. This solution is based on the use of a permalloy iron core 3 in the second current transformer 11, which has the characteristics of high sensitivity and high response to the current on the transmission cable 1 / primary winding 2. The current value of the secondary winding 4 is used as the control signal of the current transformer power-drawing mode, which not only makes the power-drawing device have complete functions (no longer requires a separate measuring device for measuring the current on the transmission cable 1), but also has the characteristic of high reliability in switching the power-drawing mode.

[0079] In addition, this solution includes a current transformer with two types of iron cores 3, silicon steel sheets and permalloy, corresponding to the distribution network monitoring and control equipment. Even if there is only a small current on the transmission cable 1, the energy used by the second current transformer 11 can be used to maintain basic functions such as the online status of these devices. For example, for the data processing edge computing function of the fusion terminal when responding to data reporting and the driving mechanism action function when the fuse performs opening and closing actions, the energy supply of high-energy-consuming components such as the corresponding processor and the driving mechanism can be obtained through the first current transformer 17 and stored in the energy storage device 10. That is, even if the energy storage device 10 such as a capacitor or a battery has increased in service life and its capacity has decayed and the first current transformer 17 cannot obtain electric energy normally, the power collected by the first current transformer 17 can be used to maintain the online function, data viewing function and other communication functions of the distribution network equipment.

[0080] In addition, if only considering the power supply under the low current state of the transmission cable 1, thanks to the high saturation magnetic density and low loss characteristics of the nanocrystalline core 3, when not pursuing power supply under the smaller current of the transmission cable 1, the alternative solution of the core 3 on the second current transformer 11 can be the nanocrystalline core 3. The nanocrystalline core 3 can realize power supply under the low current state of the transmission line while not easily forming a magnetic saturation state. However, when considering obtaining the current value, since nanocrystals are more sensitive to mechanical stress than Permalloy, a possible problem is that the nanocrystalline core 3 will have a continuous drift problem when used for current value measurement, resulting in uncontrollable stability and accuracy of current value acquisition. With the development of nanocrystalline material technology and core 3 assembly technology, the nanocrystalline core 3 with stable performance should be considered as an equivalent solution to the Permalloy core.

[0081] Example 2:

[0082] This embodiment is further refined based on the embodiment 1:

[0083] The third wire 12 has two ends connected to different ends of the secondary winding 4 of the second current transformer 11, and a second switch 13 and a resistor 14 are connected in series to the third wire 12;

[0084] The device further includes a fourth switch 16. When the second switch 13 is closed, the fourth switch 16 acts as an isolating switch between the loop formed by the secondary winding 4 on the second current transformer 11 and the third conductor 12 and the first current transformer 17, thereby preventing the current generated by the first current transformer 17 from flowing through the resistor 14.

[0085] The on / off states of the fourth switch 16 and the second switch 13 are both controlled by the control module 8 , and the control module 8 collects the current value of the secondary winding 4 on the second current transformer 11 by measuring the voltage value across the resistor 14 .

[0086] The above scheme further illustrates the structure of the second current transformer 11. Specifically, when the second current transformer 11 needs to draw power, the third switch 15 and the second switch 13 are opened, and the fourth switch 16 is closed. When the current value needs to be acquired, the third switch 15 and the fourth switch 16 are opened (if the first current transformer 17 needs to draw power during the current value acquisition process, the fourth switch 16 is opened and the third switch 15 is closed), and the second switch 13 is closed. That is, the second current transformer 11 can be controlled to switch between the following three states during its use: power-drawing state, current value acquisition state, non-power-drawing state, and non-current value acquisition state (for example, the third switch 15 is closed to isolate the second current transformer 11 from the power-drawing circuit, and the second switch 13 is in the open state). In the above scheme, the ring loop is the current value acquisition loop, and the fourth switch 16 is provided to perform an isolation function to prevent the current generated by the first current transformer 17 from affecting the current value acquisition accuracy. The on / off states of the fourth switch 16 and the second switch 13 are set to be controlled by the control module 8. In this way, the control module 8 can determine whether the second current transformer 11 needs to draw energy based on the current value of the transmission line currently detected. When necessary, the current value change trend of the transmission line can be predicted based on the current value on the current transmission line, so as to adjust the power-drawing cycle and the collection cycle of the second current transformer 11 as needed. For example, when the current value of the transmission line is small, it means that the current magnetic saturation margin of the Permalloy core is large. At this time, the power-drawing cycle can be divided into longer and the collection cycle can be divided into shorter. Under the premise of ensuring the safety of the use of the second current transformer 11, the second current transformer 11 can be used to draw energy as much as possible; when the current value of the transmission line increases, it means that the current magnetic saturation margin of the Permalloy core is small. At this time, the power-drawing cycle can be divided into shorter and the collection cycle can be divided into longer. The current value changes are collected at a higher frequency, and the safety of the use of the second current transformer 11 is ensured by sacrificing the power.

[0087] In a specific implementation, if the first terminal of the secondary winding 4 of the second current transformer 11 is connected in series with the secondary winding 4 of the first current transformer 17 via the second wire 7, the fourth switch 16 can be connected in series with the first terminal. Of course, the fourth switch 16 can also be provided at the terminal on the other side of the secondary winding 4 of the second current transformer 11. The third wire 12 and the fourth wire 18 are connected in parallel with the terminals at both ends of the secondary winding 4 of the second current transformer 11.

[0088] Example 3:

[0089] This embodiment is further refined based on the embodiment 1:

[0090] The first current transformer 17 and the second current transformer 11 are both equipped with a primary winding 2 , and the primary windings 2 of the two are connected in series.

[0091] The above scheme is: a primary side winding 2 is configured in both the second current transformer 11 and the first current transformer 17. In such an application, the primary side winding 2 of each needs to be connected in series in the transmission cable 1, that is, the power taking device needs to be connected in series on the transmission cable 1. Compared with traditional applications, this scheme can flexibly adjust the number of turns of the primary side winding 2 so that the power taking device has targeted power taking performance and current value measurement performance.

[0092] Example 4:

[0093] This embodiment is further refined based on the embodiment 1:

[0094] Both the first current transformer 17 and the second current transformer 11 use the transmission cable 1 as the primary winding 2 .

[0095] The above solution is: use the transmission cable 1 as a primary side winding 2 with one turn. This application method can complete the configuration of the power taking device on the transmission cable 1 without disconnecting the transmission cable 1, which is in line with the installation characteristics of general power taking devices.

[0096] Example 5:

[0097] This embodiment is further refined based on the embodiment 1:

[0098] It also includes a rectifier module 9 and an energy storage device 10. The output end of the current transformer is connected to the AC input end of the rectifier module 9, and the energy storage device 10 is connected to the DC output end of the rectifier module 9. The rectifier module 9 is used to convert the AC current obtained by the current transformer into DC power of a set voltage and charge the energy storage device 10.

[0099] The above scheme is: the rectifier module 9 acts as a current conversion module, converts the electric energy obtained by the current transformer into electric energy with set parameters and stores it in the energy storage device 10, so that the power consumption of the corresponding distribution network equipment is not limited to the output power of the current power-taking device. The energy storage device 10 is a capacitor or a battery.

[0100] Example 6:

[0101] This embodiment, based on any of the above embodiments, provides a CT power supply method. The power supply method is implemented based on the power supply device described in any of the above embodiments. The power supply device is configured on the transmission cable 1 and draws power from the transmission cable 1 based on the principle of electromagnetic induction.

[0102] The control module 8 determines the current value on the transmission cable 1 according to the collected current value, and controls the on / off state of the first switch 6 and the third switch 15 according to the current value determination result;

[0103] When the current value on the transmission cable 1 is less than the first set threshold, the first switch 6 is closed, the third switch 15 is opened, and the second current transformer 11 draws power;

[0104] When the current value on the transmission cable 1 is greater than or equal to the first set threshold and less than the second set threshold, power is taken in any of the following ways:

[0105] The first switch 6 is closed, the third switch 15 is opened, and the second current transformer 11 draws power;

[0106] The first switch 6 is disconnected, the third switch 15 is disconnected, and power is taken from the first current transformer 17 and the second current transformer 11;

[0107] When the current value on the transmission cable 1 is greater than or equal to the second set threshold, the first switch 6 is opened, the third switch 15 is closed, and the power is taken from the first current transformer 17;

[0108] The first set threshold is smaller than the second set threshold.

[0109] The above power-drawing method is a method based on the power-drawing device, and the current value determination result is the current value result on the transmission cable 1 obtained by the ampere-turn balance principle calculation model based on the current value of the secondary winding 4 on the second current transformer 11. In summary, this method can effectively broaden the busbar / primary side current range applicable to the current transformer while protecting the current transformer itself, thereby realizing wide-range CT power-drawing; this solution also has the characteristics of high power-drawing efficiency; this solution has both current value measurement and power-drawing functions, and the reliability of power-drawing mode switching is high; under low current conditions on the transmission cable 1, the basic functions of the distribution network equipment can be maintained; in this solution, the first current transformer 17 and the second current transformer 11 draw power under different working conditions, while meeting the reliable power-drawing requirements under low current conditions of the transmission line, and utilizing the first current transformer 17 with a lower setting cost to meet the power-drawing needs under normal circumstances, so that this solution also has the characteristics of good economic use.

[0110] In specific implementation, taking into account the power and cost of the power-taking device, for example, for a 10kV transmission line, the first set threshold is set to 0.5A~1A, and the second set threshold is set to 5A~8A. Under this setting, when the cost of the iron core 3 is controllable, according to the current value of the 10kV line under normal circumstances, the current transformer only needs to draw power through the first current transformer 17 under the line operation condition, and the second current transformer 11 user has simple functions such as online distribution equipment in extreme cases.

[0111] Example 7:

[0112] This embodiment is further refined based on embodiment 6:

[0113] When the current value on the transmission cable 1 is less than the first set threshold, the control module 8 executes: using the first sampling frequency to collect the current value of the secondary winding 4 on the second current transformer 11;

[0114] When the current value on the transmission cable 1 is greater than or equal to the first set threshold and less than the second set threshold, the control module 8 executes: using the second sampling frequency to collect the current value of the secondary winding 4 on the second current transformer 11;

[0115] The first sampling frequency is lower than the second sampling frequency;

[0116] After the control module 8 collects the current value of the secondary winding 4 on the second current transformer 11, it calculates the current value on the transmission cable 1, compares the calculation result with the first set threshold and the second set threshold, and adjusts the way in which the power taking device takes power from the transmission cable 1 according to the comparison result.

[0117] In the above scheme, the current value on the transmission cable 1 is the current value on the transmission cable 1 obtained by calculation after the current value of the secondary winding 4 of the second current transformer 11 is measured. Under non-accident conditions, this current value can most accurately reflect the current situation on the current transmission cable 1 (the current value on the transmission cable 1 generally changes linearly). In this scheme, different sampling frequencies are configured for current value acquisition based on the calculation result of the current value on the transmission cable 1, which is used to deal with: when it is necessary to use the second current transformer 11 to draw power, according to the current value judgment result on the transmission cable 1, it is decided to sample the current value according to the first sampling frequency and the second sampling frequency, and the first sampling frequency is set to be lower than The second sampling frequency, so that when the current value is less than the first set threshold value, a lower sampling frequency is used to sample the current value. This application is used to optimize the duration of the power-taking cycle of the second current transformer 11 (the second current transformer 11 is in a non-power-taking working mode when only the current value is sampled) and reduce the power consumption caused by the current value sampling calculation. When the current value fluctuates to an interval value between the first set threshold value and the second set threshold value, it means that the current value on the current transmission line is closer to the state of causing the Permalloy core to reach magnetic saturation. The second sampling frequency is used for sampling, and the power-taking mode is quickly switched at the expense of power consumption and power-taking time, so as to provide better magnetic saturation protection for the second current transformer 11.

[0118] Example 8:

[0119] This embodiment is further refined based on Example 7 and Example 2:

[0120] The power taking device is the power taking device comprising the fourth switch 16, the third wire 12, the second switch 13 and the resistor 14 as described above;

[0121] When the second current transformer 11 draws power, the second switch 13 is opened and the fourth switch 16 is closed. When the control module 8 collects current values, the control module 8 adjusts the power collection and collection period according to the first set threshold value. The current value is collected during the collection period. During the collection period, the second switch 13 is closed and the fourth switch 16 is opened.

[0122] When power is drawn from the first current transformer 17 and the second current transformer 11, the second switch 13 is opened and the fourth switch 16 is closed. When the control module 8 collects current values, the control module 8 adjusts the power drawing and collection period according to the second set threshold value. The current value is collected during the collection period. During the collection period, the second switch 13 is closed and the fourth switch 16 is opened.

[0123] When power is taken from the first current transformer 17 , the second switch 13 is closed and the fourth switch 16 is opened.

[0124] The above scheme is based on the specific structural setting of the current value acquisition structure. The control module 8 implements the method of switching the power supply mode of the power supply device, the power supply of the second current transformer 11 and the acquisition cycle according to the current current value on the current transmission line. In specific implementation, if the second current transformer 11 is currently being used to draw power, the power-drawing cycle can be set to be 100ms continuous. After the power-drawing cycle is completed, a collection cycle of 20ms is executed (the total time required to complete a round of current value collection). During the collection cycle, a set number of current values ​​are collected. When the first current transformer 17 and the second current transformer 11 are used to draw power, the current value on the current transmission cable 1 is closer to the current that causes the Permalloy core to be magnetically saturated. The power-drawing cycle can be set to be 40ms continuous. After the power-drawing cycle is completed, a collection cycle of 40ms is executed. During the collection cycle, a set number of current values ​​are collected. When the first current transformer 17 draws power, the second current transformer 11 is disconnected from the power-drawing circuit under the action of the relevant switch and maintains the closed state of the ring loop. At this time, the second current transformer 11 can be used to complete current value collection at any time. For those skilled in the art, the above-mentioned settings of the cycle duration are only examples, and those skilled in the art may adopt other duration values ​​according to the performance of the corresponding current transformer and the general variation law of the current on the transmission cable 1.

[0125] Example 9:

[0126] This embodiment, based on any one of Examples 1 to 5, provides a specific application of two power-taking devices. The fusion terminal and the fuse are used as two important distribution network devices. The power-taking devices are used to maintain the short-term high-energy-consuming working power supply requirements required by the fusion terminal and the fuse, as well as the online power supply requirements of the equipment in extreme situations (after the energy storage device 10 is damaged or its performance deteriorates).

[0127] This embodiment also relates to a converged terminal, including a data processing module and a power supply module for providing electric energy to the data processing module, wherein the power supply module includes the power supply device as described in any one of the above items.

[0128] The present embodiment also relates to a fuse, including a driving mechanism for controlling a circuit on-off switch element and driving the switch element to operate, and also including a power supply module for providing electrical energy to the driving mechanism, wherein the power supply module includes a power supply device as described in any one of the above. As a person skilled in the art, the existing intelligent fuse has a structural arrangement including a controller, a status (voltage / current, temperature, etc.) sensor, a communication unit, and a driving mechanism. The driving mechanism generally adopts an electromagnetic driver or a motor driver, and its driving mechanism adopts a power supply device as described in any one of the above as a power supply module. When the controller sends an action instruction to the driving mechanism and executes the corresponding action according to the status detection result, it can not only avoid the fuse from blowing in a fault state and reduce the number of fuse maintenance times, but also has the characteristics of rapid action and the ability to provide timely protection for the line compared to the line protection achieved by the fuse blowing.

[0129] Example 10:

[0130] This embodiment provides a more detailed technical solution based on any of the above embodiments:

[0131] For applications that require measuring smaller currents on the transmission cable 1 (0.4 kV), an activation module is configured for the CT power taking device. The activation module is as follows: when the current on the transmission cable 1 is too small, resulting in insufficient magnetic permeability of the iron core 3, and the second current transformer 11 cannot be used to measure and calculate the current value on the transmission cable 1 based on the current value, the activation module uses the electric energy obtained and stored in the energy storage device 10 by the CT power taking device to inject excitation current into the secondary winding 4 of the second current transformer 11, and uses the method of synthesizing magnetic potential to assist in establishing the necessary effective magnetic flux on the iron core 3 of the second current transformer 11, so as to break through the small current value measurement limitation caused by the material properties of the iron core 3.

[0132] Furthermore, the control module 8 can be used to control the activation module to provide excitation current according to the potential of the energy storage device 10. Specifically, when the potential exceeds the set potential threshold, the excitation current is continuously provided to the second current transformer 11 to continuously obtain the current value on the transmission cable 1; when the potential is lower than the set potential threshold, a periodic excitation current power supply mode is adopted to periodically measure the current value (the second current transformer 11 intermittently measures the current value) to reduce the total energy loss during the current value measurement process. However, it should be noted that the excitation current provided cannot be a pulse to maintain a single attenuation of the magnetic field of the iron core 3 (a pulse current input to maintain the effective magnetic field of the iron core 3 in a magnetizing manner after the last injection of excitation current). Such a pulse excitation current injection method will lead to a serious increase in the total energy demand, which is not conducive to maintaining the total measurable time of the current value.

[0133] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific embodiments of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art to which the present invention belongs, other embodiments derived without departing from the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. A CT power supply device, comprising a current transformer, characterized in that: The current transformer comprises a first current transformer (17) and a second current transformer (11); Both the first current transformer (17) and the second current transformer (11) are provided with an iron core (3) and a secondary winding (4); The secondary windings (4) of the two are connected in series via a second wire (7); The iron core (3) of the first current transformer (17) is a silicon steel sheet iron core, and the iron core (3) of the second current transformer (11) is a Permalloy iron core; It also includes a first wire (5) whose two ends are respectively connected to different ends of the secondary winding (4) on the first current transformer (17), and a first switch (6) is connected in series with the first wire (5); It also includes a fourth wire (18) whose two ends are respectively connected to different ends of the secondary winding (4) on the second current transformer (11), and a third switch (15) is connected in series to the fourth wire (18); It also includes a control module (8), which is used to collect the current value of the secondary winding (4) on the second current transformer (11) and control the on-off state of the first switch (6) and the third switch (15) based on the current value.

2. A CT power supply device according to claim 1, characterized in that: It also includes a third wire (12) whose two ends are respectively connected to different ends of the secondary winding (4) of the second current transformer (11), and a second switch (13) and a resistor (14) are connected in series to the third wire (12); The device further comprises a fourth switch (16), which, when the second switch (13) is closed, acts as an isolating switch for the ring loop formed by the secondary winding (4) on the second current transformer (11) and the third conductor (12), and the ring loop and the first current transformer (17), thereby preventing the current generated by the first current transformer (17) from flowing through the resistor (14); The on / off states of the fourth switch (16) and the second switch (13) are both controlled by the control module (8), and the control module (8) collects the current value of the secondary winding (4) on the second current transformer (11) by measuring the voltage value across the resistor (14).

3. A CT power supply device according to claim 1 or 2, characterized in that: The first current transformer (17) and the second current transformer (11) are both provided with a primary winding (2), and the primary windings (2) of the two are connected in series.

4. A CT power supply device according to claim 1 or 2, characterized in that: Both the first current transformer (17) and the second current transformer (11) use a transmission cable (1) as a primary side winding (2).

5. A CT power supply device according to claim 1 or 2, characterized in that: It also includes a rectifier module (9) and an energy storage device (10), wherein the output end of the current transformer is connected to the AC input end of the rectifier module (9), and the energy storage device (10) is connected to the DC output end of the rectifier module (9). The rectifier module (9) is used to convert the AC current obtained by the current transformer into DC power of a set voltage and charge the energy storage device (10).

6. A CT power supply method, characterized in that: The power extraction method is implemented based on the power extraction device according to any one of claims 1 to 5, wherein the power extraction device is arranged on a power transmission cable (1) and extracts power from the power transmission cable (1) based on the principle of electromagnetic induction; The control module (8) determines the current value on the transmission cable (1) based on the collected current value, and controls the on / off state of the first switch (6) and the third switch (15) based on the current value determination result; When the current value on the transmission cable (1) is less than a first set threshold value, the first switch (6) is closed, the third switch (15) is opened, and power is taken from the second current transformer (11); When the current value on the transmission cable (1) is greater than or equal to the first set threshold value and less than the second set threshold value, power is taken in any of the following ways: The first switch (6) is closed, the third switch (15) is opened, and power is taken from the second current transformer (11); The first switch (6) is disconnected, the third switch (15) is disconnected, and power is obtained from the first current transformer (17) and the second current transformer (11); When the current value on the transmission cable (1) is greater than or equal to a second set threshold, the first switch (6) is opened, the third switch (15) is closed, and power is taken from the first current transformer (17); The first set threshold is smaller than the second set threshold.

7. A CT power extraction method according to claim 6, characterized in that: When the current value on the transmission cable (1) is less than a first set threshold value, the control module (8) executes: sampling the current value of the secondary winding (4) on the second current transformer (11) using a first sampling frequency; When the current value on the transmission cable (1) is greater than or equal to a first set threshold value and less than a second set threshold value, the control module (8) executes: sampling the current value of the secondary winding (4) on the second current transformer (11) using a second sampling frequency; The first sampling frequency is lower than the second sampling frequency; After the control module (8) collects the current value of the secondary winding (4) on the second current transformer (11), it calculates the current value on the transmission cable (1), compares the calculated result with the first set threshold value and the second set threshold value, and adjusts the way in which the power taking device takes power from the transmission cable (1) based on the comparison result.

8. A CT power extraction method according to claim 7, characterized in that: The power extraction device is the power extraction device according to claim 2; When the second current transformer (11) draws power, the second switch (13) is disconnected and the fourth switch (16) is closed. When the control module (8) collects the current value, the control module (8) adjusts the power collection and collection cycle according to the first set threshold value, wherein the current value is collected during the collection cycle, the second switch (13) is closed during the collection cycle, and the fourth switch (16) is disconnected. When power is taken from the first current transformer (17) and the second current transformer (11), the second switch (13) is disconnected and the fourth switch (16) is closed. When the control module (8) collects the current value, the control module (8) adjusts the power collection and collection cycle according to the second set threshold value, wherein the current value is collected during the collection cycle, the second switch (13) is closed during the collection cycle, and the fourth switch (16) is disconnected. When power is taken from the first current transformer (17), the second switch (13) is closed and the fourth switch (16) is opened.

9. A converged terminal comprising a data processing module and a power supply module for providing power to the data processing module, characterized in that: The power supply module includes the power extraction device according to any one of claims 1 to 5.

10. A fuse comprising a switch element for controlling the on / off of a circuit and a drive mechanism for driving the switch element, and a power supply module for providing power to the drive mechanism, characterized in that: The power supply module includes the power extraction device according to any one of claims 1 to 5.

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