CN115394541A - Current transformer shielding case and installation method thereof - Google Patents
Current transformer shielding case and installation method thereof Download PDFInfo
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- CN115394541A CN115394541A CN202211106379.5A CN202211106379A CN115394541A CN 115394541 A CN115394541 A CN 115394541A CN 202211106379 A CN202211106379 A CN 202211106379A CN 115394541 A CN115394541 A CN 115394541A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
- H01F27/36—Electric or magnetic shields or screens
- H01F27/366—Electric or magnetic shields or screens made of ferromagnetic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F38/00—Adaptations of transformers or inductances for specific applications or functions
- H01F38/20—Instruments transformers
- H01F38/22—Instruments transformers for single phase ac
- H01F38/28—Current transformers
- H01F38/30—Constructions
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
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- Manufacturing & Machinery (AREA)
- Transformers For Measuring Instruments (AREA)
Abstract
The invention discloses a current transformer shielding case and an installation method thereof, wherein the shielding case comprises three parts, namely a shielding cylinder, a shielding ring and a shielding pipe, the shielding cylinder consists of two arc tile-shaped shielding sheets, the shielding ring consists of two sector-shaped shielding sheets, and the shielding pipe is of a tubular openable structure; the shielding structure has the advantages of convenient manufacture, quick installation, good shielding performance, safety and reliability.
Description
Technical Field
The invention relates to a current transformer shield cover applied to the fields of electrical metering detection, electrical safety protection and electrical fire monitoring detection, in particular to a high-precision current transformer and a residual current transformer, and also relates to an installation method of the shield cover.
Background
The current transformer works based on the electromagnetic induction principle and is used for detecting the current of a primary loop; the residual current transformer based on kirchhoff current law is used for detecting the residual current of a primary circuit. Due to the fact that magnetic permeability of all parts of a magnetic core used by the transformer is different, winding density of a secondary loop coil cannot be absolutely uniform, the magnetic core of the open-close type current transformer needs to be cut, and the like, the electromagnetic induction intensity between a primary loop and a secondary loop is unbalanced. Specifically, for a current transformer, particularly a high-precision open-close type current transformer, under the condition that the current of a primary loop is not changed, the primary loop is positioned at different positions in a through hole, and the induced electromotive force intensity generated by a secondary loop is different; for the residual current transformer, under the condition that the actual residual current of the primary circuit is not changed, the primary circuit is positioned at different positions in the through hole, the induced electromotive force intensity generated by the secondary circuit of the residual current transformer is different, and the unbalance phenomenon of the residual current transformer is very serious because the working current of the primary circuit is very large and the detected residual current is very small. The performance of inhibiting the unbalance phenomenon is called as the balance performance of the current transformer, and the improvement of the balance performance of the current transformer is an important technical means for improving the measurement accuracy of the current transformer, particularly a high-precision current transformer and a residual current transformer.
In order to improve the balance performance of the current transformer, a method of arranging a shielding cover made of soft magnetic materials at the periphery of the secondary loop coil is adopted, and a good effect can be achieved. But the problems of complex structure, troublesome installation, poor safety, high processing difficulty, low cost performance and the like generally exist.
For example, chinese patent No. 2016101124000 discloses a method and a device for improving balance of an open type residual current transformer, which is characterized in that: the method comprises the following steps: a. according to the thickness and performance requirements of the three-phase electric wire, selecting a matched open type residual current transformer and a matched shielding sheet; b. tightly winding a shielding sheet on the three-phase power line, and adhering and fixing the shielding sheet by using a viscous force device in order to prevent the shielding sheet from rebounding; c. installing an open type residual current transformer, closing an opening part of the open type residual current transformer, verifying that the open type residual current transformer can normally work, and positioning a shielding sheet in a circular hole of the open type residual current transformer; d. disassembling the viscous force device to enable the shielding sheet to rebound and attach to the inner surface of the circle center aperture of the open type residual current transformer; e. and the reinforcing piece is arranged between the inner side of the shielding piece and the three-phase electric wire, so that the shielding piece is tightly combined with the inner surface of the circle center aperture of the open type residual current transformer. The invention improves the balance performance of the open-close type residual current transformer by a method of winding the soft magnetic shielding sheet, but has the following problems: the installation is troublesome; the effective aperture of the primary loop becomes significantly smaller; the shielding effect needs to be improved; particularly, the soft magnetic material for manufacturing the shielding sheet is usually a conductive material, and the conductive shielding sheet is wound in a narrow distribution box, so that the potential safety hazard is great.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the current transformer shielding case which can be applied to various closed current transformers and various open-close current transformers, is convenient to manufacture, quick to install, good in shielding effect, safe and reliable, and the installation method thereof.
In order to solve the technical problem, the invention is realized by the following technical scheme comprising the steps.
A current transformer shielding case consists of three parts.
The first part is made of flaky soft magnetic materials and is manufactured into a cylindrical shielding cylinder; each shielding cylinder consists of two arc tile-shaped shielding sheets, and in order to ensure the shielding effect, the head and tail connecting parts are mutually overlapped when the two shielding sheets are combined into a closed shielding cylinder; the shape and size of the combined shielding cylinder are matched with those of the through holes of the primary loop of the current transformer; the length of the shielding cylinder is determined according to the requirement of shielding performance, and the longer the length is, the better the shielding effect is; the shielding cylinder is arranged between a secondary loop coil and a primary loop through hole shell in the current transformer and can also be arranged in the primary loop through hole; when the shielding cylinder is installed inside the current transformer, the size of the shielding cylinder is limited by the size of the inner space of the transformer.
The second part selects flaky soft magnetic materials to manufacture a gasket-shaped shielding ring; each shielding ring consists of two sector-shaped shielding sheets, and in order to ensure the shielding effect, the head and tail connecting parts are mutually overlapped when the two shielding sheets are combined into a closed shielding ring; the shape and size of the inner hole of the combined shielding ring are matched with the shape and size of the through hole of the primary loop of the current transformer; the shape of the shielding ring is determined according to the shape of the current transformer and the shielding performance requirement, and the larger the shielding ring is, the better the shielding effect is; the shielding ring is arranged between a secondary loop coil inside the current transformer and the end surface shell of the current transformer, and can also be arranged outside two end surfaces of the current transformer; when the shielding ring is installed inside the current transformer, the size of the shielding ring is limited by the size of the inner space of the transformer.
A third part, selecting a sheet soft magnetic material with good elasticity, and manufacturing a tubular shielding tube according to the shape and the size of the through hole of the primary loop of the current transformer; the shielding pipe is of an openable structure, and in order to ensure the shielding effect, the head and tail connecting parts at the opening are mutually overlapped; the shape of the shielding pipe is consistent with that of the through hole of the current transformer, and the size of the shielding pipe is slightly larger than that of the through hole of the current transformer under the condition of natural resilience; the length of the shielding pipe is determined according to the requirement of shielding performance, and the longer the length is, the better the shielding effect is; the shielding tube is arranged in a through hole of a primary loop of the current transformer.
The shielding cylinder is preferably a high permeability soft magnetic material.
The shape of the shielding cylinder may be circular, square or other shapes.
The head-to-tail connecting parts of the two arc tile-shaped shielding sheets combined into the shielding cylinder are mutually overlapped, and the length of the overlapped part after the installation is generally not more than 20mm, preferably 3 to 10mm.
The shield coil is preferably a high permeability soft magnetic material.
The outer shape and inner bore of the shield can be circular, square or other shapes.
The head and tail connecting parts of the two sector-shaped shielding sheets combined into the shielding ring are mutually overlapped, and the length of the overlapped part after the installation is generally not more than 20mm, and preferably 3 to 10mm.
The shielding tube is preferably made of a soft magnetic material with high elasticity and high magnetic permeability.
The shape of the shielding tube may be circular, square or other shape.
The end-to-end connection portions of the openings of the shielding pipes are overlapped with each other, and the length of the overlapped portion is generally not more than 30mm, preferably 10 to 20mm after the installation.
The surface of the shielding pipe is made with a layer of insulating material, so that the safety during installation and use can be improved, the layer of insulating material has an antirust function, and the service life of the product is prolonged.
The installation method of the invention comprises the following steps:
the built-in shielding cylinder and the built-in shielding ring can be only installed when the mutual inductor is manufactured, and the built-in shielding cylinder and the built-in shielding ring can be installed during manufacturing or can be installed in an engineering field; when the shielding pipe is used for the closed current transformer, the shielding pipe can be installed during manufacturing or can be installed on the engineering site, and when the shielding pipe is used for the open-close current transformer, the shielding pipe can only be installed on the engineering site.
The mounting method mainly refers to a mounting method of the shielding pipe in an engineering field, and during construction, when the current transformer is already mounted on a primary loop, the mounting method of the shielding pipe comprises the following steps:
a. opening the shielding pipe, wrapping the primary loop, and rebounding the shielding pipe to naturally close the primary loop; b. pinching the shielding pipe to make the shielding pipe slightly smaller than a primary loop through hole of the current transformer, inserting the shielding pipe into the primary loop through hole of the current transformer, and positioning the current transformer approximately at the middle position of the shielding pipe in the length direction; c. and releasing the shielding pipe to be attached in the primary loop through hole of the current transformer, and fixing the shielding pipe when needed.
The shielding cylinder, the shielding ring and the shielding pipe can be combined at will or used independently; preferably: the number of the built-in type shielding cylinder, the built-in type shielding ring and the shielding pipe is 6, namely, the built-in type shielding cylinder, the built-in type shielding ring, the built-out type shielding ring, the built-in type shielding ring and the shielding pipe, the built-in type shielding cylinder, the built-in type shielding pipe and the shielding pipe.
The shielding cylinder can be used by a plurality of phase sleeves simultaneously.
The shielding ring can be used by overlapping a plurality of shielding rings simultaneously.
The shielding tube can be used in a plurality of sleeving ways.
The invention has the advantages that: the invention breaks through the limitation of the prior art, fully utilizes the mechanical property and the electromagnetic property of the shielding material, greatly simplifies the installation and use method of the engineering site, is suitable for all open-close type current transformers and closed type current transformers, and has the advantages of good shielding property, safety, reliability, quick and convenient installation and the like.
Drawings
FIG. 1 is a schematic diagram showing the operation of opening the shielding pipe and enclosing the shielding pipe in a loop.
Fig. 2 is a schematic structural view of a shielding tube attached in a through hole of a primary loop of a current transformer.
Fig. 3 is a schematic structural view of a fan-shaped shielding sheet attached to the outside of the end face of the current transformer.
Fig. 4 is a schematic structural diagram of a structure in which two fan-shaped shielding plates are combined into a complete external shielding ring, and the whole external shielding ring is attached to the outside of the end face of the current transformer.
Fig. 5 is a schematic view showing a structure in which a shield pipe and two outer-fitted shield rings are mounted.
Fig. 6 is a schematic diagram showing an internal structure of the open/close type current transformer with the built-in type shield cylinder installed.
In fig. 1 to 6, 1, a primary circuit; 2. a current transformer; 3. a shielding tube; 4. a shielding ring; 5. a shielding cylinder; 6. a secondary loop coil.
Detailed Description
The following description of the embodiments of the invention refers to the accompanying drawings.
Example 1: the current transformer 2 is applied to a closed high-precision current transformer 2, the diameter of a through hole is 45mm, the length of the through hole is 25mm, and the current of a primary loop 1 is measured by using the current transformer 2; setting the diameter of a wire of the primary loop 1 to be about 10mm, setting the primary loop 1 at the central position of a through hole of the current transformer 2, adjusting the current of the primary loop 1 to enable the display value of an ammeter to be 100.00A, and locking the current of the primary loop 1 at the moment to be kept unchanged; the position of the primary circuit 1 in the circular through hole is slowly moved, and the test results are as follows according to different shielding conditions:
a. when the shielding tube 3, the shielding ring 4 and the shielding cylinder 5 are not used, the measured value is changed from 99.80A to 100.20A, and the measurement error is about 0.20 percent;
b. when the length of the shielding pipe 3 is 25mm, the shielding ring 4 is not arranged, and the length of the built-in shielding cylinder 5 is 21mm, the measured value is changed from 99.90A to 100.10A, and the measurement error is about 0.10 percent;
c. the length of the shield tube 3 was 35mm, the inner diameter of the exterior shield ring 4 was 45mm, the outer diameter was 70mm, and the measurement value varied from 99.94A to 100.06A without the shield tube 5, with a measurement error of 0.06%.
Example 2: the method is applied to the open-close type high-precision current transformer 2, and the other steps are the same as those of the embodiment 1, and the test results are as follows:
a. when the shielding pipe 3, the shielding ring 4 and the shielding cylinder 5 are not arranged, the measured value is changed from 99.1A to 100.9A, and the measurement error is about 0.9%;
b. when the length of the shielding pipe 3 is 25mm, the shielding ring 4 is not arranged, and the length of the built-in shielding cylinder 5 is 21mm, the measured value is changed from 99.6A to 100.4A, and the measurement error is about 0.4 percent;
c. the length of the shield pipe 3 was 35mm, the inner diameter of the exterior shield ring 4 was 45mm, the outer diameter was 70mm, and the measurement value varied from 99.8A to 100.2A without the shield tube 5, with a measurement error of about 0.2%.
Example 3: the method is applied to a closed residual current transformer 2, the diameter of a through hole is 45mm, the length of the through hole is 25mm, and the residual current of a primary circuit 1 is measured by using the residual current transformer 2; the primary loop 1 consists of two wires with the diameter of about 10mm, the working current of the primary loop 1 is 100A/50HZ, the actual residual current of the primary loop 1 is zero, and the two wires of the primary loop 1 are respectively arranged at the farthest ends of the diameter of the circular through hole; keeping the positions of two wires of the primary loop 1 unchanged, slowly rotating the residual current transformer 2 by taking the center of the through hole as the center of a circle, and according to different shielding conditions, obtaining the following test results:
a. when the shielding tube 3, the shielding ring 4 and the shielding cylinder 5 are not arranged, the residual current peak value is 25mA;
b. the length of the shielding tube 3 is 25mm, the shielding ring 4 is not arranged, and when the length of the built-in shielding cylinder 5 is 21mm, the peak value of the residual current is 12mA;
c. the length of the shielding tube 3 is 35mm, the inner diameter of the external shielding ring 4 is 45mm, the outer diameter of the external shielding ring is 70mm, and when the shielding cylinder 5 is not arranged, the peak value of the residual current is 5mA.
Example 4: the method is applied to the open-close type residual current transformer 2, and the other steps are the same as those of the embodiment 3, and the test results are as follows:
a. when the shielding tube 3, the shielding ring 4 and the shielding cylinder 5 are not arranged, the residual current peak value is 170mA;
b. the length of the shielding tube 3 is 25mm, the shielding ring 4 is not arranged, and when the length of the built-in shielding cylinder 5 is 21mm, the peak value of the residual current is 55mA;
c. the length of the shielding tube 3 is 35mm, the inner diameter of the external shielding ring 4 is 45mm, the outer diameter of the external shielding ring is 70mm, and when the shielding cylinder 5 is not arranged, the peak value of the residual current is 23mA.
Example 5: the method is applied to an open-close type residual current transformer 2, the side length of a rectangular through hole is 55mm × 125mm, the length of the through hole is 25mm, and the residual current of a primary loop 1 is measured by using the residual current transformer 2; the primary loop 1 consists of two wires with the diameter of about 10mm, the working current of the primary loop 1 is 100A/50HZ, the actual residual current of the primary loop 1 is zero, and the two wires of the primary loop 1 are respectively and closely attached to the middle points of two long edges of the rectangular through hole; keeping the positions of two wires of the primary loop 1 unchanged, slowly rotating the residual current transformer 2 by taking the center of the through hole as the center of a circle, and according to different shielding conditions, obtaining the following test results:
a. when the shielding tube 3, the shielding ring 4 and the shielding cylinder 5 are not arranged, the residual current peak value is 230mA;
b. the length of the shielding tube 3 is 50mm, the shielding ring 4 is not arranged, and when the shielding cylinder 5 is not arranged, the residual current peak value is 67mA;
c. the length of the shielding tube 3 is 50mm, the rectangular inner side length of the external shielding ring 4 is 55mm 125mm, the rectangular outer side length is 95mm 165mm, and when the shielding cylinder 5 is not arranged, the residual current peak value is 43mA.
In the above embodiment, the shielding tube 3 is made of mu-metal sheet with high elasticity and high magnetic permeability, and the shielding ring 4 and the shielding cylinder 5 are made of 50/470 silicon steel sheet.
In the above embodiment, the shield tube 3 and the external shield ring 4 are fixed to the transformer 2 by high-quality industrial double-sided tape.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (9)
1. A current transformer shielding case is composed of three parts and is characterized in that: the three parts are composed of a shielding cylinder arranged between a secondary loop and a primary loop of the current transformer, shielding rings arranged on two end faces of the current transformer and shielding pipes arranged in through holes of the primary loop of the current transformer.
2. The current transformer shield of claim 1, wherein: the shielding cylinder, the shielding ring and the shielding pipe can be combined and used at will.
3. A current transformer shield according to claim 1 or claim 2, wherein: the shielding cylinder, the shielding ring and the shielding pipe can be used independently.
4. A current transformer shield according to claim 1, 2 or 3, wherein: the shielding cylinder is composed of two arc tile-shaped shielding sheets, and the head and tail connecting parts are mutually overlapped when the two shielding sheets are combined into a closed cylindrical shielding cylinder.
5. A current transformer shield according to claim 1, 2 or 3, wherein: the shielding ring is composed of two sector-shaped shielding sheets, and when the two shielding sheets are combined into a closed gasket-shaped shielding ring, the head and tail connecting parts are mutually overlapped.
6. A current transformer shield according to claim 1, 2 or 3, wherein: the shielding pipe is of a tubular openable structure, and the head and tail connecting parts at the opening are mutually overlapped.
7. A current transformer shield according to claim 1, 2, 3 or 6, wherein: the shielding tube is made of soft magnetic material with good elasticity.
8. A current transformer shield according to claim 1, 2, 3 or 6, wherein: the shield tube has a size slightly larger than that of the primary circuit through hole in a naturally resilient state.
9. A method for installing a current transformer shielding case mainly refers to a method for installing a shielding pipe on an engineering site, and is characterized in that: the method comprises the following steps:
a. opening the shielding pipe, wrapping the primary loop, and rebounding the shielding pipe to naturally close the primary loop;
b. pinching the shielding pipe to make the shielding pipe slightly smaller than a primary loop through hole of the current transformer, inserting the shielding pipe into the primary loop through hole of the current transformer, and positioning the current transformer approximately at the middle position of the shielding pipe in the length direction;
c. and releasing the shielding pipe to be attached in the primary loop through hole of the current transformer, and fixing the shielding pipe when needed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211106379.5A CN115394541A (en) | 2022-09-11 | 2022-09-11 | Current transformer shielding case and installation method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211106379.5A CN115394541A (en) | 2022-09-11 | 2022-09-11 | Current transformer shielding case and installation method thereof |
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| CN115394541A true CN115394541A (en) | 2022-11-25 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116718862A (en) * | 2023-08-07 | 2023-09-08 | 杭州得明电子有限公司 | Shielding effect detection method for flyback transformer shielding layer |
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2022
- 2022-09-11 CN CN202211106379.5A patent/CN115394541A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116718862A (en) * | 2023-08-07 | 2023-09-08 | 杭州得明电子有限公司 | Shielding effect detection method for flyback transformer shielding layer |
| CN116718862B (en) * | 2023-08-07 | 2023-10-27 | 杭州得明电子有限公司 | Shielding effect detection method for flyback transformer shielding layer |
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