Current transformer

Abstract

The utility model relates to a current transformer which comprises transformer half bodies assembled in a half-and-half mode, and each transformer half body comprises a half shell and a half iron core arranged in the shell. After the two transformer half bodies are assembled, a center hole for a primary side wire to penetrate through is formed, the two ends of the two half shells are connected through fixing pieces in a one-to-one correspondence mode, and the two ends of the two half iron cores abut against each other in a one-to-one correspondence mode; and one half shell is provided with a through hole, so that the secondary winding can penetrate through the through hole after being wound on the half iron core. By adopting a half-and-half assembly structure, compared with a traditional closed-loop structure mutual inductor, a primary side wire does not need to be strenuously penetrated into a closed annular iron core. During installation, the two half bodies of the mutual inductor can be separated firstly, a primary side wire is placed at a proper position, and then the two half bodies are assembled and connected through the fixing piece. The installation difficulty and the time cost are greatly reduced, and the advantages are more obvious under the condition that the space is limited or the wires are arranged in advance.

Description

Technical Field

[0001] This utility model relates to the field of current transformer technology, and in particular to a current transformer. Background Technology

[0002] Zero-sequence current transformers play a crucial role in the operation monitoring and protection of power systems and related electrical equipment. They can detect the zero-sequence current in the system, thus providing key information for equipment fault diagnosis and leakage protection.

[0003] Currently available zero-sequence current transformers have limitations in practical applications. For example, in actual use, it has been found that because existing current transformers adopt a closed-loop structure, wires need to be threaded through them during installation. However, in actual electrical equipment wiring environments, the wires may have already been pre-laid out, and the surrounding space is limited. To accurately thread the wires into the closed-loop current transformer, a lot of time is required to adjust the position and angle of the wires, which is very troublesome and greatly increases the difficulty and time cost of installation. There is room for improvement. Utility Model Content

[0004] In order to overcome at least one of the defects of the prior art, according to one aspect of the present invention, a current transformer is provided, comprising two transformer halves assembled in half, each transformer halves comprising a half-shell and a half-core disposed within the half-shell.

[0005] After the two transformer halves are assembled, a central hole is formed for the primary side conductor to pass through. The two ends of the two half shells are connected one-to-one by fasteners, and the two ends of the two half cores abut one-to-one.

[0006] One of the half-shells has a through hole for the secondary winding to pass through after the half-core is wound.

[0007] In one embodiment of this application, the transformer half-body further includes a semi-shielding shell, the semi-shielding shell being disposed inside the half-shell, and the semi-iron core being disposed inside the semi-shielding shell.

[0008] In one embodiment of this application, the semi-shielding shell is made of permalloy material.

[0009] In one embodiment of this application, an opening is provided at the end of the half-shell for the end of the half-core to pass through, and a sealing ring is provided at the opening.

[0010] In one embodiment of this application, the sealing rings at the same side ends of the two assembled half-shells abut against each other for sealing.

[0011] In one embodiment of this application, the half-shell includes a half-upper cover and a half-bottom shell that are fitted together. The half-bottom shell has a bottom wall, side walls disposed on opposite sides of the bottom wall, and an assembly opening opposite to the bottom wall. The half-upper cover is disposed at the assembly opening.

[0012] In one embodiment of this application, the current transformer is circular in shape and the outer diameter D is in the range of 770mm≤D≤790mm.

[0013] In one embodiment of this application, the two opposite outer sidewalls at both ends of the half-shell are provided with fixing ribs for connection with the fixing member.

[0014] In one embodiment of this application, a break design is formed between the ends of the two half-shells.

[0015] In one embodiment of this application, the half-shell with a through hole is provided with a pair of protective plates on its outer side wall, and the through hole is located between the pair of protective plates.

[0016] In one embodiment of this application, the half-shell is made of aluminum alloy.

[0017] In one embodiment of this application, the half-shell, half-core, and half-shielding shell are C-shaped.

[0018] In summary, the current transformer provided by this utility model has the following technical effects:

[0019] The half-assembly structure eliminates the need for laboriously threading the primary-side conductors into a closed toroidal core, unlike traditional closed-loop current transformers. During installation, the two transformer halves can be separated first, the primary-side conductors placed in the appropriate positions, and then the two halves assembled and connected using fasteners. This significantly reduces installation difficulty and time costs, especially advantageous when space is limited or the conductors have already been pre-arranged. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the current transformer according to an embodiment of the present utility model;

[0021] Figure 2 This is an exploded view of the current transformer according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram showing the disassembled state of the transformer half in the current transformer of this utility model embodiment;

[0023] Figure 4 This is a cross-sectional view of the sealing ring in the current transformer according to an embodiment of the present invention;

[0024] Attached Figures: 1-Inductor half-body, 11-Half-shell, 111-Half-top cover, 112-Half-bottom shell, 1121-Bottom wall, 1122-Side wall, 1123-Assembly port, 12-Half-core, 13-Through hole, 14-Half-shielding shell, 15-Opening, 16-Sealing ring, 17-Fixing rib, 18-Protective plate. Detailed Implementation

[0025] To better understand and implement this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0026] In the description of this utility model, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] The embodiments of this application disclose a current transformer, specifically for use in power systems or communication equipment rooms where leakage current detection is required, and can be specifically a zero-sequence current transformer.

[0029] The following is in conjunction with the appendix Figures 1-4 This paper will describe in detail the specific technical solution of the current transformer in this application.

[0030] Specifically, this current transformer includes two transformer halves 1 assembled in half, each transformer halves 1 including a half shell 11 and a half core 12 disposed within the shell;

[0031] After the two transformer halves 1 are assembled, a central hole is formed for the primary side conductor to pass through. The two halves 11 are connected one-to-one by fasteners, and the two halves 12 are abutted one-to-one.

[0032] One of the half-shells 11 has a through hole 13, which allows the secondary winding to pass through the through hole 13 after the half-core 12 is wound.

[0033] The current transformer of this application operates based on the principle of electromagnetic induction, that is, when current flows through the primary conductor, a magnetic field is generated around it. Since the primary conductor passes through the central hole formed by the assembly of the two transformer halves 1, this magnetic field passes through the two half-cores 12. According to the law of electromagnetic induction, the changing magnetic field induces an electromotive force in the secondary winding of the transformer (which is wound around the half-cores 12), and the secondary winding can pass through the through hole 13. When the secondary winding forms a closed loop, an induced current is generated. By measuring and analyzing the induced current in the secondary winding, information such as the magnitude and phase of the current in the primary conductor can be indirectly obtained, thereby realizing the functions of monitoring and measuring the primary current.

[0034] In this process, the close contact between the two half-cores 12 ensures the integrity of the magnetic circuit, enabling the magnetic field to be effectively conducted in the core, thus improving the efficiency and accuracy of electromagnetic induction.

[0035] To address this, a half-assembly structure is adopted. Compared to traditional closed-loop current transformers, this eliminates the need for laboriously threading the primary-side conductors into a closed toroidal core. During installation, the two transformer halves 1 can be separated first, the primary-side conductors placed in appropriate positions, and then the two halves assembled and connected using fasteners. This significantly reduces installation difficulty and time costs, especially advantageous when space is limited or the conductors have been pre-arranged. For later maintenance and repair, the transformer halves 1 can be easily disassembled for inspection, repair, or replacement of internal components such as the half-core 12 and secondary windings.

[0036] Furthermore, the two ends of the two half-cores 12 are connected one-to-one, a structural design that ensures the continuity and stability of the magnetic circuit of the core. During the operation of the current transformer, a stable magnetic circuit helps to accurately perform electromagnetic induction and reduces measurement errors caused by magnetic circuit instability. At the same time, the two ends of the two half-shells 11 are connected one-to-one by fasteners, making the mechanical structure of the entire transformer more robust. It can withstand certain external mechanical stresses, vibrations, and other interferences, and is less prone to deformation or damage. This improves the reliability of the transformer in complex working environments, ensures its long-term stable operation, and reduces the risk of abnormal operation of the power system or electrical equipment caused by transformer failure.

[0037] Specifically, the number of turns of the primary conductor passing through the center hole of the current transformer can be one, that is, the number of turns of the primary conductor passing through the center hole of the current transformer is one. Of course, in other embodiments, the number of turns can be set according to the actual situation.

[0038] Specifically, the half-shell 11 can be made of aluminum alloy. Previously, current transformer shells were often made of engineering plastics, such as PBT (polybutylene-terephthalate) or ABS (acrylonitrile-butadiene-styrene copolymer). While these materials offer some insulation and ease of processing, they have poor rigidity. In practical applications, especially in harsh environments such as those subject to mechanical impact, significant vibration, or external pressure, the engineering plastic shell is prone to deformation. This deformation can damage internal precision components such as the half-core 12 and windings, affecting the normal operation of the current transformer and leading to inaccurate measurements or even malfunctions.

[0039] In this application, aluminum alloy is used to make the half-shell 11, which enables the current transformer shell to maintain good stability and shape integrity when facing mechanical shock, vibration and external extrusion, effectively resist external forces, protect internal components from damage, ensure long-term reliable operation of the current transformer, and reduce maintenance costs due to shell deformation; at the same time, it can also improve the rigidity of the half-shell 11, and can adapt well to harsh environments.

[0040] Specifically, in a current transformer half-body 1, the current transformer half-body 1 also includes a semi-shielded shell 14, which is disposed within the half-shell 11, and the semi-core 12 is disposed within the semi-shielded shell 14. In many practical application scenarios, such as near large electrical equipment in substations and factories, there are strong magnetic field environments. The shielding measures of traditional current transformers may not be perfect, making them susceptible to interference from strong external magnetic fields. These external magnetic fields affect the change in magnetic flux of the internal core of the current transformer, causing deviations in the electromagnetic induction process, thereby reducing the measurement accuracy of the current transformer and making it impossible to accurately obtain the true information of the primary current, affecting the normal operation and control of the power system or electrical equipment.

[0041] In this regard, the semi-shielded shell 14 provides an additional layer of shielding protection. When a strong magnetic field exists in the external environment, the semi-shielded shell 14 can effectively block or weaken the influence of these magnetic fields on the internal half-core 12. For example, in a substation, numerous high-voltage devices generate strong magnetic fields. The semi-shielded shell 14 can allow the electromagnetic induction process inside the transformer half-core 1 to take place in a relatively stable magnetic field environment, greatly improving the measurement accuracy of the transformer in a strong magnetic field environment. This is of vital importance for ensuring accurate metering, fault detection, and stable operation of the power system, reducing the possibility of misjudgment and erroneous operation caused by external magnetic field interference.

[0042] Specifically, the semi-shielded shell 14 can be made of permalloy. Previously, instrument transformer shielding often used materials such as silicon steel. Silicon steel has relatively low permeability, and in modern electrical environments, especially in the presence of strong magnetic field interference sources (such as near large transformers, high-voltage transmission lines, and large motors), it cannot effectively shield the influence of strong external magnetic fields on the internal electromagnetic induction process of the instrument transformer. Strong magnetic fields can distort the magnetic flux of the instrument transformer core, leading to increased measurement errors and making it impossible to accurately obtain the true parameters of the primary current. This, in turn, affects the metering accuracy, fault diagnosis, and normal operation of protection devices in the power system.

[0043] To address this, permalloy is used, which has extremely high magnetic permeability and can effectively shield strong external magnetic fields. When strong external magnetic field interference exists, the permalloy semi-shielded shell 14 can guide the magnetic field lines along its surface, reducing the magnetic flux entering the interior of the half-core 12, thereby minimizing the interference of external magnetic fields on the electromagnetic induction process of the instrument transformer. In strong magnetic field environments such as substations and large steel plants, instrument transformers using permalloy semi-shielded shells 14 can significantly improve measurement accuracy, ensure the accuracy of current measurement in the power system, and provide reliable data support for the stable operation of the power system, energy metering, and fault diagnosis.

[0044] Specifically, in one half-shell 11, an opening 15 is provided at the end of the half-core 12 for the end of the half-core 12 to pass through, so that the end of the half-core 12 can pass through and abut against the end of the half-core 12 in the other half-shell 11.

[0045] Specifically, a sealing ring 16 is installed at the opening 15. Traditional current transformer designs may lack sufficient protection for the iron core. In some designs, there are no effective sealing and protection measures specifically for the iron core, making it susceptible to external environmental factors. For example, in humid environments, moisture may penetrate the iron core, causing rust or affecting its electromagnetic properties; in dusty environments, dust accumulation may alter the magnetic permeability and other characteristics of the iron core, thus affecting the measurement accuracy and reliability of the current transformer.

[0046] To address this, by creating an opening 15 at the end of the half-shell 11 for the end of the half-core 12 to pass through and installing a sealing ring 16, a relatively closed and stable environment can be provided for the core. Therefore, the sealing ring 16 can effectively prevent harmful factors such as external moisture, dust, and corrosive gases from entering the area where the core is located. For example, in outdoor power equipment, even under harsh weather conditions such as rain and sand erosion, the sealing ring 16 can prevent these external impurities from contacting the core, maintaining the stability of the core's physical and electromagnetic properties, ensuring the long-term stable operation of the transformer, and reducing the performance degradation and failure risk caused by environmental factors affecting the core.

[0047] Specifically, the sealing rings 16 at the same-side ends of the two assembled half-shells 11 abut against each other for sealing. In the structural design of the current transformer, if the seals at the ends of the half-shells 11 cannot work effectively together, sealing leaks can easily occur. For example, relying solely on the sealing ring 16 of a single half-shell 11 for partial sealing may leave tiny gaps at the joint where the two half-shells 11 are assembled. External moisture, dust, harmful gases, etc., may still enter the current transformer through these gaps. This will disrupt the clean, dry, and stable electromagnetic environment inside the current transformer, affecting the normal operation of critical components such as the core and windings, thereby reducing the performance and measurement accuracy of the current transformer.

[0048] In response, the sealing rings 16 at the same side ends of the two assembled half-shells 11 abut against each other, forming a continuous and complete sealing barrier. This design effectively prevents external impurities such as moisture, dust, and corrosive gases from entering the transformer from any direction. External factors, whether horizontal or vertical, are unlikely to breach this sealing barrier. For example, in industrial production workshops where there is a large amount of dust and chemical fumes, this sealing structure ensures that the inside of the transformer remains uncontaminated, maintaining the normal operating environment of the core and windings, and guaranteeing the accuracy and stability of the transformer's measurements.

[0049] Specifically, epoxy resin is filled at the sealing ring 16 of the opening 15 at the end of the housing. However, relying solely on the sealing ring 16 for sealing may result in incomplete sealing. For example, gaps may appear at the contact interface between the sealing ring 16 and the housing opening 15 due to surface roughness, minor dimensional deviations, or wear after long-term use. These gaps become channels for external impurities (such as moisture, dust, and corrosive gases) to enter the transformer, thus affecting its performance and service life.

[0050] To address this, this application uses epoxy resin to fill the opening 15 and the sealing ring 16 at the end of the housing. This effectively fills the tiny gaps between the sealing ring 16 and the housing, tightly bonding the sealing ring 16 to the housing to form a seamless sealing structure. For example, in high-humidity environments, the epoxy resin filling can prevent moisture penetration, ensuring a dry working environment inside the transformer, thereby guaranteeing the normal operation of components such as the core and windings, and improving the accuracy and stability of the transformer measurements.

[0051] Specifically, the semi-shell 11 includes a half-top cover 111 and a half-bottom shell 112 that are fitted together. The half-bottom shell 112 has a bottom wall 1121, side walls 1122 disposed on opposite sides of the bottom wall 1121, and an assembly opening 1123 opposite to the bottom wall 1121. The half-top cover 111 is disposed at the assembly opening 1123. In traditional integrated housing designs, it can be difficult to install components such as the core, shielding shell, and windings into the housing. Furthermore, when maintenance, repair, or replacement of internal components is required, the integrated housing may need to be completely disassembled, which increases the complexity of operation and maintenance time.

[0052] To address this, the semi-shell 11 employs a design where a semi-top cover 111 and a semi-bottom cover 112 fit together, greatly facilitating the installation of internal components (such as the semi-core 12, the semi-shielding shell 14, etc.). During installation, components such as the semi-core 12 can be placed inside the semi-bottom cover 112. Because the semi-bottom cover 112 has a relatively large assembly opening 1123, the operating space is more ample, effectively preventing damage to components during installation. When maintenance or replacement of internal components is required, simply opening the semi-top cover 111 provides easy access, reducing maintenance workload and time. For example, if a potential fault is detected in the semi-core 12, maintenance personnel can quickly open the semi-top cover 111, remove the semi-core 12 for inspection and replacement, without requiring complex disassembly of the entire transformer.

[0053] Specifically, the half-shell 11, half-core 12, and half-shielding shell 14 are all C-shaped. The C-shaped structure offers certain advantages in the manufacturing process. This relatively regular shape facilitates production through mold forming or machining. Whether it's the half-top cover 111, the half-bottom shell 112, or the half-core 12 and half-shielding shell 14, the C-shaped structure makes mold design and manufacturing easier, ensuring product consistency and quality stability. Simultaneously, this standardized C-shaped structure also facilitates mass production and reduces production costs. For example, in injection molding the half-top cover 111 and half-bottom shell 112, the C-shaped mold design is simpler, and the demolding process is easier, thereby improving production efficiency and shortening the production cycle.

[0054] Specifically, the half-top cover 111 and the half-bottom shell 112 are also C-shaped, which can further improve production efficiency and shorten the production cycle.

[0055] Specifically, the two opposite outer side walls 1122 at both ends of the half-shell 11 are provided with fixing ribs 17 for connection with the fixing components. Therefore, the ends of the two half-shells 11 can be fixedly connected by the fixing ribs 17 and the fixing components. During the assembly of the current transformer, without a specially designed and reasonable connection structure, the two half-shells 11 may become loose or displaced after connection. For example, if the half-shells 11 are connected by simple clips, the connection points are prone to fatigue and deformation when the current transformer is subjected to vibration, impact, or long-term mechanical stress, leading to separation of the half-shells 11 or a loose connection, which in turn affects the normal operation of the internal components of the current transformer, reducing the performance and service life of the current transformer.

[0056] To address this, the fixing ribs 17 located at both ends of the half-shell 11 opposite the two outer side walls 1122 provide precise connection positions for the fasteners. When the fasteners (such as bolts and nuts, screws, or clamps) engage with the fixing ribs 17, a stable connection force is generated, tightly fixing the two half-shells 11 together. This connection method can effectively resist various mechanical forces, such as vibration and impact, experienced by the transformer during operation. For example, in outdoor power equipment, even if the transformer is subjected to external interference such as strong winds, the half-shells 11 connected by the fixing ribs 17 and the fasteners can maintain a tight connection, ensuring that the internal components of the transformer, such as the half-core 12 and the half-shielding shell 14, are not affected, thereby guaranteeing the accuracy and stability of the transformer measurements.

[0057] Specifically, a break is designed between the ends of the two half-shells 11. When the metal casing forms a closed loop, an induced current is generated within the metal casing under the influence of an alternating magnetic field. This induced current generates its own magnetic field, which superimposes on the original magnetic field inside the transformer, thus interfering with the normal electromagnetic induction process.

[0058] To address this, a break design is created between the ends of the two half-shells 11, effectively preventing the metal casing from forming a closed loop. This prevents the generation of induced current within the metal casing due to a closed loop during transformer operation, thus avoiding interference from additional magnetic fields on the internal electromagnetic induction process of the transformer. For example, in high-precision current measurement applications, this break design can significantly improve the measurement accuracy of the transformer, enabling more accurate detection of the magnitude and changes in the primary current, and providing reliable data support for metering, protection, and control functions of the power system.

[0059] Specifically, the half-shell 11 with the through hole 13 has a pair of protective plates 18 on its outer side wall 1122, with the through hole 13 located between the pair of protective plates 18. Since the secondary winding will pass through the through hole 13, a connector will be inserted into the through hole 13 during actual assembly. The connector will be specifically connected to the secondary winding. Due to accidental collisions, scratches, or other mechanical damage during the transportation, installation, or daily operation of the transformer, the connector may be damaged.

[0060] In this regard, it can provide effective mechanical protection for the joint. When an accidental collision or scratch occurs, the protective plate 18 will first bear the external force, disperse and buffer the impact force, avoid direct damage to the joint, ensure that the internal components and external lines can be connected smoothly, and maintain the normal working state of the transformer.

[0061] Specifically, this current transformer is circular in shape, and its outer diameter D is within the range of 770mm ≤ D ≤ 790mm. For example, the outer diameter D of this current transformer can be 770mm, 775mm, 780mm, 785mm, or 790mm. Of course, in other embodiments, the outer diameter D of this current transformer can also be other sizes within the range of 770mm ≤ D ≤ 790mm. Thus, current transformers with an outer diameter D within this circular size range of 770mm ≤ D ≤ 790mm can be well adapted to many common power system installation environments. For example, in the distribution cabinets of some conventional industrial substations, the reserved installation space for transformers within this size range can accommodate transformers. Installers can complete the installation smoothly without large-scale modifications to the internal structure of the distribution cabinet, saving installation time and costs, ensuring the rationality of the overall electrical equipment layout, facilitating subsequent maintenance and repair of other equipment, and ensuring that the necessary electrical safety distance requirements are met between various devices.

[0062] More importantly, the circular structure and specific outer diameter of current transformers within this size range allow for suitable cross-sectional area and spatial layout of internal components. For carrying current, this size range ensures that when large currents (up to 2000A, etc.) pass through, the core can effectively concentrate the magnetic field, and the windings can accurately induce the corresponding electromotive force, achieving high-precision current measurement and conversion. This meets the power system's functional requirements for accurate metering and fault monitoring under different current conditions. Furthermore, the relatively symmetrical circular structure contributes to a uniform magnetic field distribution, further improving the stability and accuracy of electromagnetic induction and ensuring the overall excellent performance of the transformer.

[0063] The technical means disclosed in this utility model are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications are also considered within the scope of protection of this utility model.

Claims

1. A current transformer, characterized in that, It includes two transformer halves (1) assembled in half, each transformer halves (1) including a half shell (11) and a half core (12) disposed within the half shell; After the two transformer halves (1) are assembled, a central hole is formed for the primary side conductor to pass through. The two halves (11) are connected one-to-one by fasteners, and the two halves (12) are abutted one-to-one. One of the half-shells (11) has a through hole (13) for the secondary winding to pass through the through hole (13) after the half-core (12) is wound.

2. A current transformer according to claim 1, characterized in that, The transformer half (1) also includes a semi-shielded shell (14), which is disposed inside the half shell (11), and the semi-core (12) is disposed inside the semi-shielded shell (14).

3. A current transformer according to claim 2, characterized in that, The semi-shielded shell (14) is made of permalloy material.

4. A current transformer according to claim 1, characterized in that, The end of the half shell (11) is provided with an opening (15) for the end of the half core (12) to pass through, and a sealing ring (16) is provided at the opening (15).

5. A current transformer according to claim 4, characterized in that, The sealing rings (16) at the ends on the same side of the two assembled half-shells (11) abut against each other to seal.

6. A current transformer according to any one of claims 1-5, characterized in that, The half-shell (11) includes a half-top cover (111) and a half-bottom shell (112) that are fitted together. The half-bottom shell (112) has a bottom wall (1121), side walls (1122) disposed on opposite sides of the bottom wall (1121), and an assembly opening (1123) opposite to the bottom wall (1121). The half-top cover (111) is disposed at the assembly opening (1123).

7. A current transformer according to any one of claims 1-5, characterized in that, The current transformer is circular in shape and its outer diameter D has a range of 770mm≤D≤790mm.

8. A current transformer according to any one of claims 1-5, characterized in that, The two opposite outer sidewalls (1122) at both ends of the half shell (11) are provided with fixing ribs (17) for connection with the fastener; a break design is formed between the ends of the two half shells (11).

9. A current transformer according to any one of claims 1-5, characterized in that, The half-shell (11) with a through hole (13) has a pair of protective plates (18) on its outer side wall (1122), and the through hole (13) is located between the pair of protective plates (18).

10. A current transformer according to any one of claims 1-5, characterized in that, The half-shell (11) is made of aluminum alloy; the half-shell (11), the half-iron core (12) and the half-shielding shell (14) are C-shaped.

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