A zero sequence rectangular current transformer

Abstract

The utility model relates to electric power equipment technical field discloses a zero sequence rectangular current transformer, including current transformer body, the current transformer body whole presents rectangular structure, the current transformer body external size length is 410mm, the current transformer body maximum thickness is 47mm, the current transformer body height is 229mm, the current transformer body is equipped with the hole, and the size is 150mm 350mm. In the utility model, the transformer effectively solves the problem of insufficient precision and difficulty in capturing tiny current in 0A-30A main loop zero sequence current measurement of traditional products, by adopting high magnetic induction oriented silicon steel sheet laminated iron core, matching double layer dense winding process secondary winding, and setting 0.5mm thick permalloy shielding layer between the iron core and the shell, realizing overall measurement error less than or equal to 1%, the measurement error of 0.5A tiny zero sequence current is only plus or minus 0.005A, the error rate precision of 5% of traditional products is improved by more than 80%, can accurately capture the leakage, ground fault precursor, and provides reliable monitoring basis for the safe operation of power system.

Description

Technical Field

[0001] This utility model relates to the field of power equipment technology, and in particular to a zero-sequence rectangular current transformer. Background Technology

[0002] In power systems, the zero-sequence current transformer body is a key device for detecting and protecting the zero-sequence current of the system. It is widely used in industrial power distribution, civil building power distribution, new energy power plant power distribution and other fields. Its core function is to sense changes in the main circuit current through the iron core and then output signals to the protection device through the winding to realize the monitoring and early warning of faults such as leakage current and grounding.

[0003] Currently, traditional zero-sequence current transformers have significant limitations in technical design and practical application for measuring zero-sequence current in the 0A-30A main circuit, especially in terms of accuracy control and the capture of minute currents. From the perspective of materials and processes, traditional products mostly use ordinary silicon steel sheets as the core material. This type of material has low permeability and insufficient sensitivity to changes in weak magnetic flux. In addition, the winding design is mostly single-layer winding, resulting in large signal loss between windings. This means that it can only effectively detect zero-sequence currents of 10A and above, and it is difficult to accurately identify minute zero-sequence currents below 1A, thus failing to meet the high-precision measurement requirements across the entire 0A-30A range. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a zero-sequence rectangular current transformer, which aims to improve the problems of insufficient accuracy and difficulty in capturing small currents in the measurement of zero-sequence current in the 0A-30A main circuit of existing current transformers.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a zero-sequence rectangular current transformer, comprising a current transformer body, the current transformer body having an overall rectangular structure, the external length of the current transformer body being 410mm, the maximum thickness of the current transformer body being 47mm, the height of the current transformer body being 229mm, the current transformer body having an inner hole with dimensions of 150mm×350mm, the edge of the inner hole of the current transformer body adopting a rounded corner design with a radius of 5mm; the current transformer body includes an iron core, a secondary winding, a housing, and terminals, the housing having four M5 screw mounting holes, the diameter of the mounting holes being 6mm, the center distance of the mounting holes being 394mm in the length direction, and the center distance of the mounting holes being 194mm in the height direction.

[0006] Furthermore, the iron core is made of high-magnetic-induction grain-oriented silicon steel sheets, with a sheet thickness of 0.3 mm and a cross-sectional area of ​​25 cm². 2A 0.5mm thick permalloy shielding layer is provided between the iron core and the outer shell.

[0007] Furthermore, the secondary winding uses high-strength enameled copper wire with a diameter of 0.5mm, is wound using a double-layer close winding process, has a total of 2000 turns, and a winding resistance of 15Ω; the secondary winding is located in the lower middle part of the iron core, 12mm away from the bottom of the iron core, and is wrapped with 0.2mm thick insulating paper on the outside of the winding.

[0008] Furthermore, the current transformer body operates based on the principle of electromagnetic induction, and the neutral wire and the live wire must pass through the inner hole simultaneously. When passing through, the minimum distance between the cable and the inner hole wall is not less than 10mm.

[0009] Furthermore, the outer shell is made of glass fiber reinforced unsaturated polyester resin, and the surface of the outer shell is coated with a 30μm thick antistatic coating; the wiring terminal is made of copper and nickel-plated, and the wiring terminal has two terminals with a spacing of 20mm.

[0010] Furthermore, the current transformer body can accommodate simultaneous measurement of large cables with a diameter of 80mm or less, and multiple cables of 6 or less.

[0011] This utility model has the following beneficial effects:

[0012] In this invention, the current transformer effectively solves the problems of insufficient accuracy and difficulty in capturing minute currents in the measurement of zero-sequence current in the 0A-30A main circuit of traditional products. By using a core made of high magnetic induction oriented silicon steel sheets, combined with a secondary winding using a double-layer close-wound process, and setting a 0.5mm thick permalloy shielding layer between the core and the outer shell, the overall measurement error is ≤1%, and the measurement error for a minute zero-sequence current of 0.5A is only ±0.005A. This is more than 80% higher than the 5% error rate of traditional products, and can accurately capture the precursors of faults such as leakage and grounding, providing a reliable monitoring basis for the safe operation of the power system. Attached Figure Description

[0013] Figure 1 This is a front view of a zero-sequence rectangular current transformer proposed in this utility model;

[0014] Figure 2 This is a top view of a zero-sequence rectangular current transformer proposed in this utility model;

[0015] Figure 3 This is a side view of a zero-sequence rectangular current transformer proposed in this utility model. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] Reference Figure 1 This utility model provides an embodiment of a zero-sequence rectangular current transformer, comprising a current transformer body. The current transformer body is generally rectangular in structure, with an external length of 410mm, a maximum thickness of 47mm, and a height of 229mm. The current transformer body has an inner hole with dimensions of 150mm × 350mm, and the edge of the inner hole is designed with a radius of 5mm. The current transformer body includes an iron core, a secondary winding, a housing, and terminals. The housing has four M5 screw mounting holes with a diameter of 6mm. The center distance between the mounting holes is 394mm in the length direction and 194mm in the height direction.

[0018] Specifically, the current transformer body contains a carefully crafted iron core, which is made of high-magnetic-induction oriented silicon steel sheets precisely stacked. The thickness of each silicon steel sheet is precisely controlled to 0.3 mm. This silicon steel raw material possesses excellent magnetic properties, specifically exhibiting significant characteristics of high permeability and low magnetic leakage. Its high permeability can reach up to 1.5 × 10⁻⁶. 4 With a permeability of 80,000 Henry / meter and a low magnetic leakage rate strictly controlled within 2%, the iron core can sensitively sense the magnetic flux generated by changes in the main circuit current, thereby achieving high-precision detection of minute zero-sequence currents. In addition, in order to effectively block external electromagnetic interference and ensure the purity of the detection signal, the designers specially set a 0.5 mm thick permalloy shielding layer between the iron core and the outer shell. This permalloy material has extremely high permeability, with a value of not less than 80,000 Henry / meter, and can achieve an electromagnetic interference attenuation effect of up to 40 dB in a wide frequency range from 1 kHz to 10 MHz, thus effectively ensuring the stability and reliability of the magnetic induction signal.

[0019] The current transformer body also includes a secondary winding, which is made of high-strength enameled copper wire with a diameter of 0.5mm. It is wound using a double-layer close winding process with a total of 2000 turns and a winding resistance of 15Ω. The high-strength enameled copper wire has both good conductivity and mechanical strength, which can reduce signal loss during current transmission. In order to meet the insulation requirements, 0.2mm thick insulating paper is wrapped around the outside of the winding, so that the insulation class of the winding reaches F class, avoiding current leakage from affecting measurement accuracy and safety of use.

[0020] The housing of this current transformer is made of glass fiber reinforced unsaturated polyester resin, a material known for its excellent insulation properties, with an insulation resistance of over 1000 megohms. It also possesses high mechanical strength, with an impact resistance of no less than 15 kilojoules per square meter. Furthermore, this material exhibits good environmental resistance, withstanding temperatures as high as 150 degrees Celsius and as low as -40 degrees Celsius, effectively protecting the internal core and windings from external environmental corrosion. To further enhance safety, a 30-micron-thick antistatic coating is applied to the surface of the housing, enabling it to better adapt to various complex environments.

[0021] The terminals of this current transformer are specifically designed for connecting external conductors. They are made of high-quality copper and have undergone nickel plating. The copper material itself ensures good conductivity of the terminals, while the nickel plating process significantly improves the corrosion resistance and oxidation resistance of the terminals. The terminals are M6 in size and have two 20mm-spaced terminals to facilitate stable connection of external conductors, ensuring efficient and stable transmission of induced current signals, thereby guaranteeing the reliable operation of the entire current transformer.

[0022] Working principle: The current transformer body contains an iron core made of high-permeability grain-oriented silicon steel sheets, with a sheet thickness of 0.3 mm. This material possesses high permeability and low magnetic leakage, with a permeability reaching 1.5 × 10⁻⁶. 4 With a permeability of ≥80000H / m and a low magnetic leakage rate of ≤2%, it can sensitively detect the magnetic flux generated by changes in the main circuit current, thereby achieving high-precision detection of minute zero-sequence currents. At the same time, in order to block external electromagnetic interference, a 0.5mm thick permalloy shielding layer is set between the iron core and the outer shell. This material has a permeability of ≥80000H / m and can achieve ≥40dB of electromagnetic interference attenuation in the frequency range of 1kHz-10MHz, thereby ensuring the stability of the magnetic induction signal.

[0023] The current transformer body also includes a secondary winding, which is made of high-strength enameled copper wire with a diameter of 0.5mm. It is wound using a double-layer close winding process with a total of 2000 turns and a winding resistance of 15Ω. The high-strength enameled copper wire has both good conductivity and mechanical strength, which can reduce signal loss during current transmission. In order to meet the insulation requirements, 0.2mm thick insulating paper is wrapped around the outside of the winding, so that the insulation class of the winding reaches F class, avoiding current leakage from affecting measurement accuracy and safety of use.

[0024] The outer shell of this current transformer is made of glass fiber reinforced unsaturated polyester resin, which has excellent insulation properties with an insulation resistance ≥1000MΩ, and also has high mechanical strength with an impact resistance ≥15kJ / m. 2 It also has environmental resistance, withstanding high temperatures of 150℃ and low temperatures of -40℃, effectively protecting the internal iron core and windings from external environmental corrosion; at the same time, the outer shell is coated with a 30μm thick antistatic coating, further improving safety and adapting to the needs of various environmental scenarios.

[0025] The terminals of this current transformer body are used for connecting external wires. They are made of copper and have been nickel-plated. The copper material ensures good conductivity, while the nickel plating process improves the corrosion resistance and oxidation resistance of the terminals. The terminals are M6 and have two 20mm-spaced terminals for easy and stable connection of external wires, ensuring effective transmission of induced current signals.

[0026] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A zero-sequence rectangular current transformer, comprising a current transformer body, characterized in that: The current transformer body has an overall rectangular structure. The external length of the current transformer body is 410mm, the maximum thickness of the current transformer body is 47mm, and the height of the current transformer body is 229mm. The current transformer body has an inner hole with dimensions of 150mm × 350mm. The edge of the inner hole of the current transformer body adopts a rounded corner design with a radius of 5mm. The current transformer body includes an iron core, a secondary winding, a housing, and terminals. The housing has four M5 screw mounting holes with a diameter of 6mm. The center distance between the mounting holes is 394mm in the length direction and 194mm in the height direction.

2. A zero-sequence rectangular current transformer according to claim 1, characterized in that: The iron core is made of high-magnetic-induction grain-oriented silicon steel sheets, with a sheet thickness of 0.3 mm and a cross-sectional area of ​​25 cm². 2 A 0.5mm thick permalloy shielding layer is provided between the iron core and the outer shell.

3. A zero-sequence rectangular current transformer according to claim 1, characterized in that: The secondary winding uses high-strength enameled copper wire with a diameter of 0.5mm and is wound using a double-layer close winding process. The total number of turns is 2000, and the winding resistance is 15Ω. The secondary winding is located in the lower middle part of the iron core, 12mm away from the bottom of the iron core, and the outside of the winding is wrapped with 0.2mm thick insulating paper.

4. A zero-sequence rectangular current transformer according to claim 1, characterized in that: The current transformer body works based on the principle of electromagnetic induction. The neutral wire and the live wire must pass through the inner hole at the same time. When passing through, the minimum distance between the cable and the inner hole wall is not less than 10mm.

5. A zero-sequence rectangular current transformer according to claim 1, characterized in that: The outer shell is made of glass fiber reinforced unsaturated polyester resin, and the surface of the outer shell is coated with a 30μm thick antistatic coating; the wiring terminal is made of copper and nickel plated on the surface, and the wiring terminal has two terminals with a spacing of 20mm.

6. A zero-sequence rectangular current transformer according to claim 1, characterized in that: The current transformer body can accommodate large cables with a diameter of up to 80mm and multiple cables of 6 or less simultaneously for measurement.

Images