A current transformer and its anti-interference test method and terminal equipment

Abstract

This application relates to the field of current transformer technology, and discloses a current transformer and its anti-interference testing method and terminal equipment. The current transformer includes: a double-wound coil, an iron core, and a metal shielding layer. The double-wound coil includes a test winding and a secondary winding. The secondary winding is wound on a winding skeleton on the surface of the iron core, and the metal shielding layer wraps around the outside of the secondary winding. The test winding is wound around the outside of the metal shielding layer. When receiving an interference magnetic field, the double-wound coil is used to generate mutually canceling first and second interference electromotive forces based on the secondary winding, and mutually canceling third and fourth interference electromotive forces based on the test winding. This current transformer suppresses magnetic field interference generated by external current through the secondary winding and the test winding. The test winding can reuse the function of the shielding winding, realizing the dual functions of detection calibration and magnetic field shielding, thus ensuring the output accuracy of the current transformer.

Description

Technical Field

[0001] This application relates to the field of current transformer technology, and in particular to a current transformer and its anti-interference testing method and terminal equipment. Background Technology

[0002] Zero-sequence current transformers are key sensing elements for ground fault detection and relay protection in power systems. They induce unbalanced zero-sequence current through a toroidal core with three-phase conductors, and output corresponding voltage / current signals via electromagnetic coupling in the secondary winding. The test winding is used for factory accuracy verification and on-site live calibration to ensure measurement reliability. However, the existing coil winding structure of zero-sequence current transformers has inherent defects: external stray magnetic fields can penetrate the shielding gaps and end leakage magnetic paths, resulting in significant noise superposition in the induced signal, causing maloperation or failure to operate of protection devices. This problem is particularly prominent in high-interference scenarios such as compact switchgear and densely laid multi-circuit installations, and has become a technical bottleneck restricting the upgrading of high-reliability relay protection systems. Summary of the Invention

[0003] In view of this, the present application provides a current transformer and its anti-interference testing method and terminal equipment, which can effectively improve the serious external magnetic field interference problem of the existing winding structure of the current transformer in practical engineering applications.

[0004] In a first aspect, embodiments of this application provide a current transformer, comprising: a double-wound coil, an iron core, and a metal shielding layer, wherein the double-wound coil includes a test winding and a secondary winding; The secondary winding is wound on the winding skeleton on the surface of the iron core, the metal shielding layer is wrapped around the outside of the secondary winding, and the test winding is wound around the outside of the metal shielding layer. When an interfering magnetic field is received, the dual-group parallel-wound coils are used to generate a first interfering electromotive force and a second interfering electromotive force based on the secondary winding, and to generate a third interfering electromotive force and a fourth interfering electromotive force based on the test winding, wherein the first interfering electromotive force and the second interfering electromotive force cancel each other out in the parallel-wound circuit of the secondary winding, and the third interfering electromotive force and the fourth interfering electromotive force cancel each other out in the parallel-wound circuit of the test winding.

[0005] In a first possible embodiment of the first aspect, the secondary winding and the test winding are respectively arranged in the same direction on the winding frame on the surface of the iron core; Both the secondary winding and the test winding are provided with symmetrically wound wires.

[0006] In a second possible embodiment of the first aspect, it further includes: a first insulating layer, a second insulating layer, and a third insulating layer; The first insulating layer is disposed between the secondary winding and the iron core, the second insulating layer is disposed between the secondary winding and the metal shielding layer, and the third insulating layer is disposed between the metal shielding layer and the test winding.

[0007] In a third possible embodiment of the first aspect, it further includes: a protective housing; The protective outer shell is disposed between the secondary winding and the metal shielding layer.

[0008] In a fourth possible embodiment of the first aspect, a load resistor is further included; The load resistor is connected to both ends of the secondary winding.

[0009] In a fifth possible embodiment of the first aspect, the metal shielding layer is provided with an air gap.

[0010] Secondly, embodiments of this application provide an anti-interference test method for a current transformer, including: Establish the first digital model of the aforementioned current transformer and the second digital model of the reference current transformer; Determine the first solution region of the first digital model and the second solution region of the second digital model respectively; After applying excitation sources to the first digital model and the second digital model respectively, the first output data of the current transformer is simulated based on the first solution region, and the second output data of the reference current transformer is simulated based on the second solution region. Based on the comparison results of the first output data and the second output data, it is determined whether the current transformer has passed the anti-interference test.

[0011] In a first possible embodiment of the second aspect, determining the first solution region of the first digital model and the second solution region of the second digital model respectively includes: The components in the first digital model and the second digital model whose electromagnetic field gradient is greater than a preset gradient threshold are respectively divided into meshes; The first solution region and the second solution region are determined based on the first digital model and the second digital model after mesh division, respectively.

[0012] In a second possible embodiment of the second aspect, the first output data includes a first secondary winding voltage, a first test winding current, and a first test winding voltage, and the second output data includes a second secondary winding voltage, a second test winding current, and a second test winding voltage. The step of determining whether the current transformer passes the anti-interference test based on the comparison result of the first output data and the second output data includes: Under the conditions that the voltage of the first secondary winding is greater than the voltage of the second secondary winding, the current of the first test winding is greater than the current of the second test winding, and the voltage of the first test winding is greater than the voltage of the second test winding, the current transformer is determined to have passed the anti-interference test. If the voltage of the first secondary winding is less than or equal to the voltage of the second secondary winding, the current of the first test winding is less than or equal to the current of the second test winding, or the voltage of the first test winding is less than or equal to the voltage of the second test winding, the current transformer is determined to have failed the anti-interference test.

[0013] Thirdly, embodiments of this application provide a terminal device, which includes a processor and a memory. The memory stores a computer program, and the processor executes the computer program to implement the above-described anti-interference test method for current transformers.

[0014] The embodiments of this application have the following beneficial effects: This embodiment of a current transformer includes: a double-wound coil, an iron core, and a metal shielding layer. The double-wound coil includes a test winding and a secondary winding. The secondary winding is wound on a winding frame on the surface of the iron core, and the metal shielding layer wraps around the outside of the secondary winding. The test winding is wound around the outside of the metal shielding layer. When an interference magnetic field is received, the double-wound coil generates a first interference electromotive force (EMF) and a second interference EMF based on the secondary winding, and generates a third interference EMF and a fourth interference EMF based on the test winding. The first and second interference EMFs cancel each other out in the parallel winding circuit of the secondary winding, and the third and fourth interference EMFs cancel each other out in the parallel winding circuit of the test winding. Based on the above scheme, this current transformer suppresses magnetic field interference generated by external current through the secondary winding and the test winding. Simultaneously, the test winding can reuse the function of the shielding winding, achieving a dual function of detection calibration and magnetic field shielding. Without increasing additional windings or manufacturing costs, it significantly improves the magnetic field interference suppression capability and ensures the output accuracy of the current transformer. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A cross-sectional view of the conventional structural arrangement of a reference current transformer according to an embodiment of this application is shown; Figure 2This paper shows a schematic diagram of the conventional winding method for the secondary winding and test winding according to an embodiment of this application; Figure 3 A schematic diagram of the structure of a current transformer according to an embodiment of this application is shown; Figure 4 This illustration shows a schematic diagram of the co-directional parallel winding method of the secondary winding and the test winding according to an embodiment of this application; Figure 5 The schematic diagram illustrating the principle of suppressing external electromagnetic interference by the secondary winding in an embodiment of this application is shown. Figure 6 The schematic diagram illustrating the principle of suppressing external electromagnetic interference by the test winding in an embodiment of this application is shown. Figure 7 This diagram illustrates the induced current in the parallel-wound secondary winding caused by the normal magnetic field generated by the inner conductor in an embodiment of this application. Figure 8 This diagram illustrates the induced current in the parallel-wound test winding caused by the normal magnetic field generated by the inner conductor in an embodiment of this application. Figure 9 A flowchart illustrating the anti-interference test method for a current transformer according to an embodiment of this application is shown; Figure 10 A schematic diagram of a first digital model according to an embodiment of this application is shown; Figure 11 A schematic diagram of a second digital model according to an embodiment of this application is shown; Figure 12 The overall simulation model of the current-carrying conductor and current transformer according to an embodiment of this application is shown; Figure 13 This diagram illustrates the mesh generation results of the first digital model and the current-carrying conductor according to an embodiment of this application. Figure 14 A schematic diagram of the second secondary winding voltage of a reference current transformer according to an embodiment of this application is shown; Figure 15 A schematic diagram of the first and second winding voltages of the current transformer according to an embodiment of this application is shown; Figure 16 A schematic diagram of the second test winding current of a reference current transformer according to an embodiment of this application is shown; Figure 17 A schematic diagram of the first test winding current of a current transformer according to an embodiment of this application is shown; Figure 18 A schematic diagram of the second test winding voltage of a reference current transformer according to an embodiment of this application is shown; Figure 19 A schematic diagram of the first test winding voltage of a current transformer according to an embodiment of this application is shown; Figure 20 A schematic diagram of the magnetic flux density of the second magnetic core according to an embodiment of this application is shown; Figure 21 A schematic diagram of the magnetic flux density of the first magnetic core according to an embodiment of this application is shown.

[0017] Explanation of key component symbols: 100 - Current transformer; 110 - Double-wound coil; 111 - Test winding; 112 - Secondary winding; 120 - Iron core; 130 - Metal shielding layer; 131 - Air gap; 140 - Protective casing. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] The components of the embodiments of this application described and illustrated in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] In the following text, the terms "comprising," "having," and their cognates, which may be used in various embodiments of this application, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more combinations thereof. Furthermore, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0021] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. Terms (such as those defined in commonly used dictionaries) shall be interpreted as having the same meaning as in their contextual meaning in the relevant technical field and shall not be construed as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0022] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] like Figure 1 and Figure 2 As shown, Figure 2 The left side shows the conventional winding method for the secondary winding, and the right side shows the conventional winding method for the test winding. Existing zero-sequence current transformers generally use a single-coil winding structure, with both the secondary and test windings being independently wound single coils. Furthermore, the test winding is typically wound directly on the innermost layer of the transformer core surface. This existing winding structure suffers from severe external magnetic field interference problems in practical engineering applications.

[0024] The following is a detailed explanation of several key issues: Single-coil winding is susceptible to interference from external current and magnetic fields: The secondary winding and test winding are single-coil structures. Stray currents from external power lines and operating currents from surrounding electrical equipment will generate alternating magnetic fields. These external magnetic fields will pass through the transformer windings and core, generating additional electromagnetic induction with the windings. This causes the voltage / current signals output by the secondary windings to be superimposed with interference noise, and the calibration signal of the test windings will also deviate. Ultimately, this reduces the detection accuracy of the transformer and may even cause relay protection devices to malfunction or fail to operate.

[0025] The test winding has a single function and insufficient shielding capability: In traditional structures, the test winding is only used for testing and calibration and has no shielding function. Although the metal shielding layer can suppress external magnetic fields to a certain extent, it can only suppress interference outside the shielding layer. The test winding is located between the iron core and the shielding layer and is still directly exposed to the weak external magnetic field conducted by the iron core. Furthermore, the electromagnetic coupling between the test winding and the secondary winding will also generate stray coupling due to the external magnetic field, further affecting the output accuracy.

[0026] Adding an additional shielding winding increases cost and size: To solve the above-mentioned interference problem, existing technologies often add an independent shielding winding outside the secondary winding. The shielding winding generates a reverse magnetic field to suppress external interference. However, this method requires additional winding processes and copper consumption, which not only increases the manufacturing cost of the instrument transformer, but also increases the overall size of the winding, which limits the miniaturization of the instrument transformer. Furthermore, the superposition of multiple windings leads to a complex electromagnetic structure and increases the difficulty of insulation design between windings.

[0027] In summary, the existing winding structure of zero-sequence current transformers cannot effectively suppress external magnetic field interference without increasing additional cost and volume. Furthermore, the test winding has a single function and fails to fully utilize its electromagnetic characteristics. There is an urgent need to optimize the winding form and arrangement of the windings to significantly improve the anti-external magnetic field interference capability of zero-sequence current transformers while simplifying the structure and controlling costs.

[0028] To address the aforementioned issues, this application provides a current transformer and its anti-interference testing method and terminal equipment. By changing the secondary winding and test winding to a double-sided, parallel winding configuration, magnetic field interference generated by external current is suppressed, thereby improving the transformer's detection accuracy and preventing relay protection devices from malfunctioning or failing to operate. Simultaneously, by moving the test winding from the innermost layer to the outside of the shielding layer, the test winding reuses the function of the shielding winding, achieving a dual function of detection calibration and magnetic field shielding. Furthermore, the electromagnetic coupling between the test winding and the secondary winding eliminates stray coupling generated by the external magnetic field, further improving the current transformer's output accuracy. This current transformer has a simple structure and low manufacturing cost, significantly reducing design costs.

[0029] First, this application provides a current transformer 100. Please refer to... Figure 3 This is a schematic diagram of the structure of the current transformer 100 provided in the embodiment of this application. The current transformer 100 includes: a double-wound coil 110, an iron core 120 and a metal shielding layer 130. The double-wound coil 110 includes a test winding 111 and a secondary winding 112.

[0030] Exemplary, the iron core 120 is the core of the toroidal magnetic circuit, used to concentrate and guide the zero-sequence magnetic flux generated by the primary conductor, enhance the coupling efficiency of the secondary winding 112, and ensure the output linearity and accuracy under rated operating conditions. The secondary winding 112 is wound on the winding skeleton on the surface of the iron core 120, and the metal shielding layer 130 is wrapped around the outside of the secondary winding 112. The test winding 111 is wound around the outside of the metal shielding layer 130.

[0031] In this embodiment, the secondary winding 112 serves as the core sensing unit of the zero-sequence current sensor. The secondary winding 112 is directly wound onto the surface of the iron core 120, and its function is to convert the zero-sequence current in the primary conductor into a standard secondary voltage / current signal. The test winding 111 is no longer used solely for factory testing and on-site calibration; instead, it is externally positioned outside the metal shielding layer 130 and forms an active anti-interference unit with the secondary winding 112. It can sense external interference magnetic fields to generate interference electromotive force, achieving double-layer magnetic shielding in conjunction with the shielding layer; it can also cancel common-mode interference electromotive force while retaining the port voltage signal for accuracy verification. This achieves multiplexing of calibration and anti-interference functions, significantly improving the anti-interference performance of the current transformer 100 without adding complex structures. The metal shielding layer 130 tightly covers the outer side of the secondary winding 112 to block the transmission of the alternating magnetic field from the external space. Its position changes from the outermost layer to the middle layer, located between the secondary winding 112 and the external test winding 111. It not only protects the secondary winding 112 from direct magnetic field penetration, but also provides a magnetic potential reference surface for the external test winding 111, so that the interference electromotive force induced by the test winding 111 can more effectively generate a reverse magnetic flux on the surface of the shielding layer, thereby achieving a synergistic shielding effect with the test winding 111.

[0032] In one embodiment, upon receiving an interfering magnetic field, the dual-group parallel-wound coil 110 is used to generate a first interfering electromotive force (EMF) and a second interfering EMF based on the secondary winding 112, and to generate a third interfering EMF and a fourth interfering EMF based on the test winding 111, wherein the first interfering EMF and the second interfering EMF cancel each other out in the parallel-wound loop of the secondary winding, and the third interfering EMF and the fourth interfering EMF cancel each other out in the parallel-wound loop of the test winding.

[0033] In this embodiment, the amplitudes of the first and second interference electromotive forces are approximately equal but their polarities are opposite, and the amplitudes of the third and fourth interference electromotive forces are approximately equal but their polarities are opposite. Therefore, they can cancel each other out in the parallel winding circuit. Traditional current transformer designs require additional shielding windings to suppress interference, while this application achieves interference sensing and reverse cancellation through the dual sets of parallel windings 110 themselves, saving the design cost of adding independent shielding windings, and also taking into account electromagnetic interference resistance.

[0034] In one embodiment, the secondary winding 112 and the test winding 111 are respectively arranged in the same direction on the winding frame on the surface of the iron core 120. Both the secondary winding 112 and the test winding 111 are provided with symmetrically wound wires.

[0035] In this embodiment, the traditional independent single-coil winding method is abandoned. The secondary winding 112 and test winding 111 of the zero-sequence current transformer 100 are designed as parallel windings on both sides in the same direction. Figure 4 As shown, Figure 4 The left side shows the parallel winding method of the secondary winding in the same direction. Figure 4 The right side shows the parallel winding method of the test windings. Each winding uses two wires / enameled wires wound synchronously on the winding frame on both sides of the magnetic core, in the same direction and with the same pitch, forming an integrated double-group parallel winding coil 110. For example... Figure 5 and 6 As shown, when the interference magnetic field generated by the external current passes through the parallel-wound coil, it will induce interference electromotive forces of approximately equal magnitude and opposite direction in the secondary winding 112 and the test winding 111, respectively. Since the two sets of coils are wound in parallel and have the same electromagnetic characteristics, the interference electromotive forces will cancel each other in the parallel winding circuit, thereby basically eliminating the interference of the external magnetic field on the output signal of the secondary winding 112 and the calibration signal of the test winding 111.

[0036] In one embodiment, the current transformer 100 further includes: a load resistor. As an example, the load resistance Connect the two ends of the secondary winding 112. In this embodiment, the load resistor... Directly connect the two ends of the secondary winding 112 to convert the induced electromotive force into a standard current signal and form a closed measurement circuit.

[0037] In one embodiment, the test winding 111 is wound on the outside of the metal shielding layer 130, serving as the external test winding 111 of the current transformer. It not only retains the original factory testing and field calibration functions but also, due to its location on the outside of the shielding layer, becomes the external shielding winding of the current transformer. The working principle of the test winding 111 utilizing the shielding function is as follows: Figure 6 As shown, the external test winding 111 can directly cut the alternating interference magnetic field of the external space and induce a reverse shielding current in the test winding 111. The reverse magnetic field generated by this current will cancel the conduction of the external magnetic field to the metal shielding layer 130 and the secondary winding 112 in advance, forming a double-layer shielding effect with the metal shielding layer 130. At the same time, the double-group parallel winding structure of the test winding 111 can avoid its own shielding current from causing electromagnetic interference to the secondary winding 112, ensuring the normal induction output of the secondary winding 112.

[0038] In one implementation, such as Figure 7 and 8 As shown, when a real zero-sequence current flows through the primary conductor, the main magnetic flux induced within the toroidal core 120 is axisymmetric and uniformly distributed. Since the secondary winding 112 and the test winding 111 employ a double-sided, parallel winding structure, with each spatial position having the same winding direction, number of turns, and pitch relative to the core 120, the useful electromotive forces induced by this main magnetic flux in the two windings are equal in magnitude and phase, i.e., superimposed in the same direction. At the port of the secondary winding 112, this same-direction electromotive force is directly accumulated and output, effectively enhancing the signal-to-noise ratio. While the test winding 111 also induces a same-direction electromotive force, because it is external and its port is open, it is only used for monitoring or participating in shielding current generation and does not interfere with the secondary output circuit.

[0039] It is understandable that the winding structure exhibits a unidirectional coupling gain for the internal signal (120 main magnetic flux of the iron core) and a reverse cancellation effect for the external interference magnetic field, thus achieving the dual effect of enhancing the beneficial signal without distortion and actively suppressing harmful interference.

[0040] In another embodiment, the number of turns of the secondary winding 112 and the test winding 111 are designed separately according to the rated parameters of the transformer, ensuring that the axes of the two sets of coils coincide during winding. For example, the number of turns of the secondary winding 112 is strictly calculated according to the rated primary current and standard secondary output to ensure the transformation ratio accuracy and load matching; the number of turns of the test winding 111 is set according to the calibration sensitivity requirements, and can be more or less than that of the secondary winding 112 to adapt to different input impedances of the testing instruments.

[0041] In this embodiment, regardless of whether the number of turns is equal, the two windings must maintain complete geometric axis coincidence and strict spatial symmetry during winding, with no radial offset or angular misalignment. This constraint ensures that the induced electromotive force amplitude of each winding to the external interfering magnetic field is highly consistent and the phase is strictly opposite, thus achieving interference cancellation.

[0042] In one embodiment, the metal shielding layer 130 is provided with an air gap 131. In this embodiment, the air gap 131 in the metal shielding layer 130 mainly serves a dual purpose of electromagnetic isolation and impedance regulation. On the one hand, as a low dielectric constant and low loss medium, the air gap 131 can significantly reduce the parasitic capacitance between the shielding layer and adjacent conductors, thereby suppressing high-frequency signal coupling and crosstalk. On the other hand, the air gap 131 changes the equivalent transmission line characteristic impedance of the shielding structure, which helps to achieve impedance matching, reduce signal reflection and standing waves, and improve the integrity of high-speed / RF signals. In addition, the air gap 131 can also alleviate thermal expansion stress, prevent the metal shielding layer 130 from deforming or delaminating due to temperature changes, and enhance structural reliability.

[0043] In one embodiment, the current transformer 100 further includes a first insulating layer, a second insulating layer, and a third insulating layer. Exemplarily, the first insulating layer is disposed between the secondary winding 112 and the core 120, the second insulating layer is disposed between the secondary winding 112 and the metal shielding layer 130, and the third insulating layer is disposed between the metal shielding layer 130 and the test winding 111.

[0044] In this embodiment, high-strength insulation layers are provided between the secondary winding 112 and the iron core 120, between the secondary winding 112 and the metal shielding layer 130, and between the metal shielding layer 130 and the test winding 111. The high-strength insulation layer can be made of polyimide film or epoxy resin insulation material. The thickness of the insulation layer is designed according to the rated operating voltage of the transformer to ensure that the insulation strength between the windings meets the safety standards of power equipment.

[0045] In another embodiment, such as Figure 3 As shown, the current transformer 100 also includes a protective housing 140. Exemplarily, the protective housing 140 is disposed between the secondary winding 112 and the metal shielding layer 130. In this embodiment, the protective housing 140 is provided on the outside of the secondary winding 112 to prevent external mechanical damage. The entire winding is fixed by epoxy resin potting to ensure the stability of the winding form and arrangement, and to avoid winding offset caused by vibration.

[0046] As an example, to verify whether the current transformer 100 has good anti-interference performance, this application provides an anti-interference test method for the current transformer 100. By simulating and comparing the output of the current transformer 100 of this application with that of a reference current transformer in the prior art, the comparison results can be used to verify whether the current transformer 100 of this application has good anti-interference performance.

[0047] For ease of understanding, the following embodiments of this application will be described in terms of... Figure 3Taking the current transformer 100 shown as an example, and referring to the accompanying drawings, the anti-interference test method of the current transformer 100 provided in the embodiments of this application will be described.

[0048] Figure 9 A flowchart illustrating an anti-interference test method for a current transformer 100 according to an embodiment of this application is shown. Exemplarily, the anti-interference test method for the current transformer 100 includes the following steps: S210, establish a first digital model of the current transformer 100 and a second digital model of the reference current transformer in the above embodiment.

[0049] As an example, the digital model is a finite element simulation model of a real current transformer. A first digital model of the current transformer 100 and a second digital model of a reference current transformer can be built in ANSYS Maxwell (ANSYS electromagnetic simulation software). For example... Figure 10 As shown, this is a schematic diagram of the first digital model. Figure 11 The image shown is a schematic diagram of the second digital model.

[0050] In one embodiment, the current transformer 100 includes a core 120, a secondary winding 112, a metal shielding layer 130, and a test winding 111. The finite element simulation material for the core 120 can be nanocrystalline alloy or permalloy strip; the finite element simulation material for the metal shielding layer 130 can be oriented / non-oriented silicon steel laminate; and the finite element simulation materials for the secondary winding 112 and the test winding 111 are both copper enameled wire. Table 1 shows the material parameters for the first digital model finite element simulation. Table 1 Material parameters in finite element simulation

[0051] In this embodiment, by constructing a high-fidelity first digital model and a second digital model in ANSYS Maxwell, a quantifiable, reproducible, and comparable performance evaluation of the two winding configurations under electromagnetic conditions is achieved.

[0052] S220, respectively determine the first solution region of the first digital model and the second solution region of the second digital model.

[0053] In one embodiment, components in the first digital model and the second digital model whose electromagnetic field gradients are greater than a preset gradient threshold are divided into meshes; the first solution region and the second solution region are determined based on the first digital model and the second digital model after mesh division.

[0054] In this embodiment, the mesh generation is a local mesh refinement process implemented for regions with drastic changes in electromagnetic field gradient, such as the 120° corners of the iron core, the ends of the windings, the edges of the shielding layer, and the vicinity of the air gap. Figure 12 As shown, the overall simulation model of the current-carrying conductor and the current transformer is presented. The current-carrying conductor is a current-carrying conductor used in the simulation to simulate external interference sources, such as... Figure 13 The diagram shows the mesh generation results of the first digital model and the current-carrying conductor. During mesh generation, the magnetic flux density gradient or electric field intensity gradient distribution is first extracted, and a preset gradient threshold is set. Manual mesh generation is automatically triggered for regions where the gradient exceeds the limit: a boundary layer mesh is used at the interface between the core 120 and the winding; prism meshes are inserted between the winding conductors; and adaptive surface mapping is enabled for the gaps between the shielding layer laminations. The remaining low-gradient regions retain tetrahedral sparse meshes. Through mesh generation, the region of concentrated electromagnetic energy can be accurately focused, significantly improving the accuracy of the output data of the subsequent analog current transformer 100.

[0055] In another implementation, the solution domain is the computational space defined in the electromagnetic simulation for the transient field-path coupled solver. Its boundary conditions and dimensions directly affect the physical realism of the transient field-path coupled solver. For example, regions with drastic changes in the electromagnetic field gradient can be determined based on the mesh generation results, and then magnetically insulating boundaries can be determined based on these regions. The solution domain can be set to include an air domain extending 3 to 5 times the geometric size of the digital model body, and the outer boundary of the entire solution domain is defined as a magnetically insulating boundary, aiming to fully accommodate the natural decay process of the open magnetic field.

[0056] S230, after applying excitation sources to the first digital model and the second digital model respectively, simulate the first output data of the current transformer 100 based on the first solution region, and simulate the second output data of the reference current transformer based on the second solution region.

[0057] Exemplary, the excitation source is a physically driven signal artificially applied in the electromagnetic simulation, used to simulate the energy input or electromagnetic interference in the actual operation of the current transformer. The excitation source can be set according to the actual operating conditions. For example, the excitation source can be set to a three-phase sinusoidal current or a short-circuit current. The three-phase sinusoidal current serves as the main excitation source, i.e., the main magnetic flux of the iron core, while the short-circuit current serves as the interference excitation source, simulating the electromagnetic interference of adjacent current-carrying conductors on the current transformer 100 in the power system.

[0058] In one embodiment, a transient field-circuit coupled solver is used during the solution process. The resistive-inductive or purely resistive load of the current transformer 100 should be defined in the circuit module. The equivalent two-port inductance elements of the two iron core windings 120 are connected in series in the circuit. The total simulation duration and step size are set in the electromagnetic field module. For example, considering that the period of the sinusoidal excitation current is 20ms, the total simulation duration is set to 120ms and the simulation step size is 0.2ms. The transient field-circuit coupled solver is used to simulate the output data of the zero-sequence current transformer 100.

[0059] S240, based on the comparison result of the first output data and the second output data, determine whether the current transformer 100 has passed the anti-interference test.

[0060] Exemplary, the first output data includes a first secondary winding voltage, a first test winding current, and a first test winding voltage, and the second output data includes a second secondary winding voltage, a second test winding current, and a second test winding voltage.

[0061] In one embodiment, the transient field-circuit coupled solver achieves high-precision simulation through bidirectional collaboration: the nonlinear magnetization, eddy currents, and spatial interference magnetic field coupling of the iron core are accurately modeled using the Finite Element Method (FEM), and the induced electromotive force of each winding is calculated in real time; the two secondary windings 112 are equivalent to series two-port inductors using the Finite Element Method, and connected to an actual resistive-inductive load, while the test winding 111 is connected in a closed loop. Within this framework, the secondary winding voltage is the output voltage generated across the secondary winding 112 after the iron core 120 induces a zero-sequence current, which is used for sampling by the relay protection device; the test winding current is the circulating current induced in the test winding 111 itself by the external interference magnetic field; the test winding voltage is the external port voltage of the test winding 111, reflecting its net induced electromotive force. In this application, the voltage of the test winding is relatively large when the iron core has main magnetic flux, indicating that the interference is effectively suppressed.

[0062] In one embodiment, the current transformer 100 is determined to have passed the anti-interference test when the voltage of the first secondary winding is greater than the voltage of the second secondary winding, the current of the first test winding is greater than the current of the second test winding, and the voltage of the first test winding is greater than the voltage of the second test winding; the current transformer 100 is determined to have failed the anti-interference test when the voltage of the first secondary winding is less than or equal to the voltage of the second secondary winding, the current of the first test winding is less than or equal to the current of the second test winding, or the voltage of the first test winding is less than or equal to the voltage of the second test winding.

[0063] In this embodiment, the higher voltages of the first and second windings indicate that the current transformer 100 suppresses interference without weakening the useful signal, confirming the in-phase superposition effect of the dual-winding on the internal magnetic field. The significantly greater current in the first test winding than the second confirms that the external winding structure successfully induces the active shielding current. The much smaller voltage in the first test winding than the second test winding proves that the interference electromotive force is efficiently canceled between the two windings. These three factors work together to provide a test basis for effective signal enhancement, interference current activation, and net interference voltage suppression, avoiding the risk of misjudgment based on a single indicator.

[0064] In one embodiment, a current transformer 100 with a rated current of 125A is used as an example for modeling. The test conditions are a three-phase unbalanced zero-sequence current of 100mA and an effective value of 125A for external conductor interference current. A schematic diagram of the secondary winding voltage of the reference current transformer is shown below. Figure 14 As shown, the schematic diagram of the first and second winding voltages of the current transformer 100 of this application is as follows: Figure 15 As shown; a schematic diagram of the second test winding current of the reference current transformer is shown below. Figure 16 As shown, the schematic diagram of the first test winding current of the current transformer 100 of this application is as follows: Figure 17 As shown; a schematic diagram of the second test winding voltage of the reference current transformer is shown below. Figure 18 As shown, the schematic diagram of the first test winding voltage of the current transformer 100 of this application is as follows. Figure 19 As shown.

[0065] contrast Figure 14 and 15 It can be seen that the secondary winding voltage of the current transformer 100 in this application has stronger immunity to external interference, and the output voltage is also larger. (Comparison) Figure 16 and Figure 17 It can be seen that the current in the test winding 111 of the reference current transformer is approximately zero, while there is a circulating current in the parallel-wound test winding 111. The currents in the two windings are equal in magnitude but opposite in direction, which can actively shield external electromagnetic interference; in comparison Figure 18 and Figure 19 It can be seen that the induced voltage amplitude in the test winding 111 of this application is relatively large, but for the external port, the voltage values ​​are basically canceled out.

[0066] In another embodiment, the first output data further includes the first magnetic core flux density, and the second output data further includes the second magnetic core flux density, such as... Figure 20 The diagram shown is a schematic representation of the magnetic flux density of the second magnetic core. Figure 21 The diagram shown illustrates the magnetic flux density of the first magnetic core. (Comparison) Figure 20 and Figure 21 It can be seen that the maximum magnetic flux density of the core of the reference current transformer and the current transformer of this application is much smaller than the saturation magnetic flux density, which verifies that the magnetic circuit design of the current transformer of this application has excellent anti-saturation capability.

[0067] In this embodiment, through structural optimization of dual-group parallel winding and external test winding 111, multiple optimizations in technical effect, structure and cost can be achieved compared with the prior art. The specific beneficial effects are as follows: The external magnetic field interference suppression capability is greatly improved, ensuring output accuracy. The dual parallel windings allow the interference electromotive force of the secondary winding 112 and the test winding 111 to cancel each other out, eliminating the interference of the external current magnetic field on the induced signal and calibration signal from the root. The external double-layer shielding formed by the test winding 111 further blocks the conduction path of the external magnetic field. The dual anti-interference design significantly improves the external magnetic field interference suppression capability of the transformer, effectively avoiding maloperation / failure to operate of the relay protection device.

[0068] The test winding 111 and the shielding winding are reused, simplifying the structure: The test winding 111 is moved from the innermost layer to the outer side of the shielding layer, so that the test winding 111 can perform the function of the shielding winding in addition to the detection and calibration function. There is no need to add a separate shielding winding. This breaks the limitation of the traditional single-function winding. The complex structure of the original iron core 120, test winding 111, secondary winding 112, shielding layer and shielding winding is simplified to a simple structure of iron core 120, secondary winding 112, shielding layer and test winding 111. The overall number of winding layers is reduced, the electromagnetic structure is simpler, and the difficulty of insulation design is greatly reduced.

[0069] It retains the original testing and calibration functions and is highly practical: the external arrangement and double-group parallel winding of the test winding 111 do not change its original core testing and calibration functions. The accuracy test of the instrument transformer can be completed through the test winding 111 at the factory. During field operation, the test winding 111 can be used to achieve non-power-off calibration. The operation method is consistent with that of traditional instrument transformers. There is no need to change the operating habits of maintenance personnel. It has strong compatibility and is easy to promote and apply in the power system.

[0070] High winding stability and long service life: The integrated structure of dual parallel windings and epoxy resin potting significantly improves the windings' resistance to vibration and temperature changes, avoiding problems such as coil misalignment and electromagnetic coupling coefficient changes caused by vibration in traditional independent windings. Multi-layer insulation design ensures reliable insulation between windings, effectively preventing partial discharge and insulation aging, and extending the service life of the transformer.

[0071] This application also provides a terminal device, exemplary of which includes a processor and a memory, wherein the memory stores a computer program, and the processor executes the computer program to enable the terminal device to perform the above-described anti-interference test method for the current transformer 100.

[0072] The processor can be an integrated circuit chip with signal processing capabilities. The processor can be a general-purpose processor, including at least one of a Central Processing Unit (CPU), Graphics Processing Unit (GPU), Network Processor (NP), Digital Signal Processor (DSP), Application-Specific Integrated Circuit (ASIC), Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The general-purpose processor can be a microprocessor or any conventional processor, capable of implementing or executing the methods, steps, and logic block diagrams disclosed in the embodiments of this application.

[0073] Memory can be, but is not limited to, Random Access Memory (RAM), Read Only Memory (ROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), and Electrically Erasable Programmable Read-Only Memory (EEPROM). Memory is used to store computer programs, and the processor can execute these programs upon receiving execution instructions.

[0074] This application also provides a computer-readable storage medium for storing the computer program used in the aforementioned terminal device. For example, the computer-readable storage medium may include, but is not limited to, various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0075] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that, in alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0076] In addition, the functional modules or units in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0077] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a smartphone, personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0078] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A current transformer, characterized in that, include: The double-wound coil, the iron core, and the metal shielding layer, wherein the double-wound coil includes a test winding and a secondary winding; The secondary winding is wound on the winding skeleton on the surface of the iron core, the metal shielding layer is wrapped around the outside of the secondary winding, and the test winding is wound around the outside of the metal shielding layer. When an interfering magnetic field is received, the dual-group parallel-wound coils are used to generate a first interfering electromotive force and a second interfering electromotive force based on the secondary winding, and to generate a third interfering electromotive force and a fourth interfering electromotive force based on the test winding, wherein the first interfering electromotive force and the second interfering electromotive force cancel each other out in the parallel-wound circuit of the secondary winding, and the third interfering electromotive force and the fourth interfering electromotive force cancel each other out in the parallel-wound circuit of the test winding.

2. The current transformer according to claim 1, characterized in that, The secondary winding and the test winding are respectively arranged in the same direction on the winding frame on the surface of the iron core; Both the secondary winding and the test winding are provided with symmetrically wound wires.

3. The current transformer according to claim 1, characterized in that, Also includes: First insulating layer, second insulating layer and third insulating layer; The first insulating layer is disposed between the secondary winding and the iron core, the second insulating layer is disposed between the secondary winding and the metal shielding layer, and the third insulating layer is disposed between the metal shielding layer and the test winding.

4. The current transformer according to claim 1, characterized in that, Also includes: Protective casing; The protective outer shell is disposed between the secondary winding and the metal shielding layer.

5. The current transformer according to claim 1, characterized in that, Also includes: Load resistance; The load resistor is connected to both ends of the secondary winding.

6. The current transformer according to claim 1, characterized in that, The metal shielding layer has an air gap.

7. A method for testing the anti-interference capability of a current transformer, characterized in that, include: Establish a first digital model of the current transformer as described in any one of claims 1-6 and a second digital model of the reference current transformer; Determine the first solution region of the first digital model and the second solution region of the second digital model respectively; After applying excitation sources to the first digital model and the second digital model respectively, the first output data of the current transformer is simulated based on the first solution region, and the second output data of the reference current transformer is simulated based on the second solution region. Based on the comparison results of the first output data and the second output data, it is determined whether the current transformer has passed the anti-interference test.

8. The anti-interference test method for a current transformer according to claim 7, characterized in that, The step of determining the first solution region of the first digital model and the second solution region of the second digital model includes: The components in the first digital model and the second digital model whose electromagnetic field gradient is greater than a preset gradient threshold are respectively divided into meshes; The first solution region and the second solution region are determined based on the first digital model and the second digital model after mesh division, respectively.

9. The anti-interference test method for a current transformer according to claim 7, characterized in that, The first output data includes the first secondary winding voltage, the first test winding current, and the first test winding voltage; the second output data includes the second secondary winding voltage, the second test winding current, and the second test winding voltage. The step of determining whether the current transformer passes the anti-interference test based on the comparison result of the first output data and the second output data includes: Under the conditions that the voltage of the first secondary winding is greater than the voltage of the second secondary winding, the current of the first test winding is greater than the current of the second test winding, and the voltage of the first test winding is greater than the voltage of the second test winding, the current transformer is determined to have passed the anti-interference test. If the voltage of the first secondary winding is less than or equal to the voltage of the second secondary winding, the current of the first test winding is less than or equal to the current of the second test winding, or the voltage of the first test winding is less than or equal to the voltage of the second test winding, the current transformer is determined to have failed the anti-interference test.

10. A terminal device, characterized in that, The terminal device includes a processor and a memory, the memory storing a computer program, and the processor executing the computer program to implement the anti-interference test method for the current transformer according to any one of claims 7-9.

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