WO2022213550A1

WO2022213550A1 - Neutral-point earthing reactor having magnetism enhancement structure

Info

Publication number: WO2022213550A1
Application number: PCT/CN2021/119316
Authority: WO
Inventors: 禹云长; 禹东泽
Original assignee: 吴江变压器有限公司
Priority date: 2021-09-07
Filing date: 2021-09-18
Publication date: 2022-10-13
Also published as: CN113744969B; CN113744969A

Abstract

Disclosed in the present invention is a neutral-point earthing reactor having a magnetism enhancement structure. The neutral-point earthing reactor comprises an oil tank, a hollow coil, which is arranged inside the oil tank and has no core limb, and a rectangular iron yoke, wherein four iron yoke edges are sequentially connected end to end, and comprise an upper yoke located at the top of the hollow coil, a first side yoke located on one side of the coil, a lower yoke located at the bottom of the hollow coil and a second side yoke located on the other side of the coil; the first side yoke, the second side yoke and the center axis of the coil are parallel and coplanar; and the center axis of the coil passes through the center point of the iron yoke, and magnetic lines of force generated after the coil is energized all pass through the iron yoke. An aluminum shielding cylinder in the prior art is replaced with the iron yoke made of a silicon steel sheet, and since the silicon steel sheet has high magnetic permeability, a magnetic circuit outside the coil can be closed, such that the reactance of the same coil is greater, and a magnetism enhancement effect is achieved. Resistance loss and eddy current loss are small such that the number of turns of the coil can be smaller, thereby saving on copper wires and greatly reducing costs.

Description

A Neutral Grounding Reactor with Magnetizing Structure

Application field

The invention relates to the field of reactor manufacturing, in particular to a neutral point grounding reactor with a magnetization enhancement structure.

Background technique

The current reactor is mainly the structure of iron core and coil, but because the reactance value of iron core type reactor is relatively large, when the magnetic density is high, the iron core will be saturated, resulting in the reduction of the iron core reactor value, which will affect the reactor's performance. use. The neutral point grounding reactor has very hard excitation characteristics. Generally speaking, when the current is ten times the rated current, its reactance is still linear, and the reactance value will not decrease, so the neutral point grounding reactor generally It is not provided with an iron core, and is directly set as an air-core coil without an iron core. In order to prevent the magnetic flux from entering the steel plate of the fuel tank after the air-core coil is energized, whether it is an iron-core reactor or a neutral grounding reactor, it is necessary to perform magnetic shielding to prevent the magnetic flux from entering the tank wall and causing the tank wall to overheat. In an iron-core reactor, the iron core is generally connected with a magnetic shield to perform magnetic shielding. For example, Chinese patent CN110349730 discloses a magnetic circuit structure of an iron-core reactor. However, in the neutral grounding reactor, since there is no iron core, the magnetic shielding method can only be adjusted. Generally, the magnetic shielding is performed by a shielding cylinder. The shielding cylinder is generally made of aluminum. The shielding cylinder generally consists of a closed cylinder surrounding the inner surface of the tank wall and shielding plates arranged at the upper and lower ends of the hollow coil; the strong eddy current diamagnetism generated by the shielding cylinder is used to prevent the magnetic flux from entering the steel plate of the fuel tank, thereby protecting the The fuel tank steel plate does not overheat.

However, there are still many drawbacks in using the shielding cylinder in the neutral point grounding reactor. The shielding cylinder is demagnetized by inductive eddy current, so the loss will be large, and the mutual inductance to the air-core coil is demagnetized, and the total loss increases. big. According to the experiment, the total inductance decreased by about 17% when the shielding cylinder was used for shielding. That is to say, in order to make the air-core coil reach the expected working state, it is necessary to increase the number of turns of the air-core coil by 17% to increase the self-inductance of the air-core coil. At the same time, since the distance between the shielding cylinder and the air-core coil must be a passageway for the magnetic flux, generally speaking, the height of the cylinder body needs to be 1.2 to 1.5 times the height of the air-core coil, and its inner diameter is larger than the outer diameter of the air-core coil. About 800mm; while the shielding plate set at the upper and lower ends of the air-core coil, its outer limit is larger than the outer diameter of the air-core coil, and the distance from the top of the air-core coil is about 440mm; and the thickness of the aluminum material used in the shielding cylinder needs to be 12mm or 16mm; the overall volume of the shielding cylinder can be seen It is huge, and the product volume and manufacturing cost also need to be greatly increased accordingly.

SUMMARY OF THE INVENTION

The invention overcomes the disadvantages of high total loss and high cost in the production of neutral point grounding reactors in the prior art, and provides a neutral point grounding reactor with a magnetization structure. The scheme is: a neutral point grounding reactor with a magnetization structure, which includes: an oil tank, an air-core coil without an iron core set inside the oil tank, and a rectangular iron yoke, the iron yoke includes four iron yoke sides, four iron yoke sides, and four iron yoke sides. Each of the iron yokes is connected end-to-end, including an upper yoke on the top of the hollow coil, a first side yoke on one side of the coil, a lower yoke on the bottom of the hollow coil, and a second yoke on the other side of the coil. The second side yoke on the side; the first side yoke, the second side yoke and the central axis of the hollow coil are parallel and coplanar; the central axis of the hollow coil passes through the center point of the iron yoke, All the magnetic lines of force generated after the air-core coil is energized pass through the iron yoke.

In a preferred embodiment of the present invention, the iron yoke is composed of a plurality of iron yoke laminations, and the material of the iron yoke is silicon steel.

In a preferred embodiment of the present invention, the vertical section of at least one side of the iron yoke is an arcuate arc, and the arc surface of the side of the iron yoke is away from the hollow coil.

In a preferred embodiment of the present invention, the thicknesses of the four iron yoke sides of the iron yoke are equal, and the thickness δ of the iron yoke sides is obtained by formula 1:

Among them, B is the magnetic flux density, r is the _inner radius of the air-core coil, and p is the radial thickness of the air-core coil;

in,

is the total magnetic flux generated by the air-core coil, the total magnetic flux

Obtained by Equation 2:

Among them, w is the number of turns of the air-core coil, k is the magnetization coefficient, and I is the air-core coil current;

Among them, L is the inductance generated when the air-core coil is energized without magnetic shielding, and the inductance L is obtained by formula 3:

Among them, h is the reactance height, and r is the _outer radius of the hollow coil.

In a preferred embodiment of the present invention, the length of the lower yoke is equal to the length of the upper yoke, and the length l of the _upper yoke is obtained by formula 4:

Among them, _next to γ is the rated insulation distance of the side yoke;

The height of the first side yoke is equal to the height of the second side yoke, and the height of the first side yoke and the height l of the second _side yoke are obtained by formula 5:

l _side =h+ _γup + _γfollowing formula 5;

Among them, the _upper γ is the rated insulation distance of the upper yoke, and the _{lower γ is the rated insulation distance of} the lower yoke.

In a preferred embodiment of the present invention, it further includes a fastening frame for clamping and fixing the iron yoke, the fastening frame is a cube frame composed of several fastening plates, and the iron yoke is placed on the side of the fastening frame. Inside, the fastening frame includes two rectangular frames and several connecting plates for connecting the two rectangular frames, one of the rectangular frames is arranged along the circumference of the upper yoke, and the other rectangular frame is arranged along the circumference of the upper yoke. In the circumferential arrangement of the lower yoke, the connecting plate is fixedly connected to the four corners of the rectangular frame to clamp the first side yoke and the second side yoke.

In a preferred embodiment of the present invention, a plurality of reinforcing plates are arranged on the top surface or/and the bottom surface of the fastening frame, and the reinforcing plates are arranged along the lamination direction of the iron yoke.

In a preferred embodiment of the present invention, both the iron yoke and the fastening frame are insulated connections.

In a preferred embodiment of the present invention, one end of the fastening plate is electrically connected to the other fastening plates, and the other end is electrically connected to the other fastening plates.

The present invention solves the defects existing in the background technology, and the present invention has the following beneficial effects:

(1) In the present invention, since the iron yoke passes through all the magnetic lines of force and the iron yoke itself is a continuous closed structure, the effect of magnetic shielding can be achieved, and the magnetic circuit will not enter the tank wall of the fuel tank, thereby causing the fuel tank to heat up. That is to say, there is a fundamental difference from the magnetic shielding principle in the prior art.

(2) In the present invention, the iron yoke processed from the silicon steel sheet has small resistance loss and eddy current loss, has high magnetic permeability, and has a magnetizing effect, so the magnetic circuit outside the air-core coil can be closed, so that the reactance of the same air-core coil is larger. , so the air-core coil can take a smaller number of turns.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, the drawings of other embodiments can also be obtained according to these drawings without creative efforts.

1 is a front view of a neutral-point grounding reactor with a magnetization-enhancing structure according to an embodiment of the present invention;

FIG. 2 is a left side view of a neutral point grounding reactor with a magnetizing structure according to an embodiment of the present invention;

3 is a top view of a neutral point grounding reactor with a magnetization enhancement structure according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a fastening frame of a neutral point grounding reactor with a magnetization enhancement structure according to an embodiment of the present invention.

Reference numerals are described as follows: 10, fuel tank; 101, tank wall; 20, hollow coil; 201, lead wire; 30, iron yoke; 301, upper yoke; 302, lower yoke; 303, first side yoke; 304, second Side yoke; 40, fastening frame; 401, rectangular frame; 402, connecting plate; 403, reinforcing plate.

Detailed ways

In order to be able to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Therefore, it only shows the structure related to the present invention, and it should be noted that the embodiments of the present application and the features of the embodiments can be combined with each other without conflict.

In the description of this application, it should be understood that the terms "center", "portrait", "horizontal", "top", "bottom", "front", "rear", "left", "right", " The orientations or positional relationships indicated by vertical, horizontal, top, bottom, inner, and outer are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and The description is simplified rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second" etc. may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; it can be mechanical connection or electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the related drawings. The preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure is provided.

Referring to FIGS. 1-3 , a neutral point grounding reactor with a magnetizing structure according to the present invention includes: a fuel tank 10 , an air-core coil 20 without an iron core arranged inside the fuel tank 10 , and a rectangular iron yoke 30. The iron yoke 30 includes four iron yoke sides, and the four iron yoke sides are connected end-to-end, including an upper yoke 301 located at the top of the air-core coil 20, a first side yoke 303 located on one side of the air-core coil 20, and a first side yoke 303 located on the air-core coil 20 The bottom yoke 302 and the second side yoke 304 on the other side of the hollow coil 20; as shown in FIG. 3, the first side yoke 303, the second side yoke 304 and the central axis of the hollow coil 20 are parallel and coplanar; The central axis of the coil 20 passes through the center point of the iron yoke 30 , and the magnetic field lines generated after the air-core coil 20 is energized pass through the iron yoke 30 .

Here, since the iron yoke 30 passes through all the magnetic lines of force generated by the air-core coil 20 and the iron yoke 30 itself is a closed-loop structure, according to the principle of magnetic field shielding, the iron yoke 30 will shield the magnetic field generated after the air-core coil 20 is energized. Naturally, the fuel tank wall 101 of the fuel tank 10 is outside the magnetic field, so that safety hazards such as heat generation will not be caused. The upper yoke 301 and the lower yoke 302 are connected by a side yoke, and there is no need to conduct magnetism through air, so the magnetic resistance is extremely small, and the magnetization can be increased to a greater extent.

Referring to FIG. 1 , at the same time, the iron yoke 30 can seal the magnetic field lines generated by the electromagnetic air-core coil 20 inside, thereby improving the efficiency. In addition, the iron yoke 30 is composed of several iron yoke sheets that are closely stacked, and since the iron yoke 30 is made of silicon steel sheets, the silicon steel sheets have higher magnetic permeability, so they can have a better magnetization effect.

As for the iron yoke 30 made of silicon steel sheet, firstly, the material cost of the silicon steel sheet itself is much lower than that of the aluminum shielding component; secondly, because the iron yoke 30 has a magnetization effect, the air-core coil 20 can be saved. The number of turns, that is, while the working effect of the air-core coil 20 remains unchanged, the amount of copper material used in the air-core coil 20 can also be saved, thereby saving a lot of costs.

For example, for example, if the air-core coil 20 itself needs to reach a certain working state, 10 turns of the air-core coil 20 are required, and when a shielding cylinder is used, 12 turns of the air-core coil 20 are needed to balance the loss, and the iron yoke 30 made of silicon steel sheet is used to carry out the process. For magnetic shielding and magnetization, only 9 turns or even 8 turns of the air-core coil 20 are required. Compared with the two, the cost of copper materials and the cost of magnetic shielding materials are greatly reduced, and the volume and weight are also greatly reduced. In the neutral point grounding reactor with a magnetization enhancement structure according to the present invention, the air-core coil 20 is an air-core coil 20 , that is, an iron core column is not provided inside the air-core coil 20 . And the two leads 201 of the air-core coil 20 can be drawn out from the front and rear sides of the iron yoke 30 .

1-3, regarding the size of the iron yoke 30, the thicknesses of the four iron yoke sides of the iron yoke 30 are equal. First, most of the magnetic flux of the air-core coil 20 is distributed in the equivalent solenoid (also It is within the circumference of the hollow coil 20); secondly, when the stack thickness of the iron yoke 30 is about the diameter of the equivalent solenoid, through finite element analysis, about 0.7 times the total magnetic flux can enter the iron yoke 30. Therefore, the thickness δ of the iron yoke side is calculated by formula 1:

Among them, r is the _inner radius of the air-core coil 20, p is the radial thickness of the air-core coil 20 (that is, the outer radius minus the inner radius), B is the magnetic flux density, the preset magnetic density B=1.4T,

The total magnetic flux generated for the air-core coil 20;

As long as the thickness of the iron yoke edge is above the calculated value, it meets the requirements of magnetic shielding, and the specific excess can be determined according to the convenience of fixing the connecting parts.

total flux

It needs to be obtained by formula 2:

Wherein, w is the number of turns of the air-core coil 20, k is the magnetization coefficient, where k is generally taken as 0.06, I is the current of the air-core coil 20; L is the inductance generated when the air-core coil 20 is energized without magnetic shielding, the inductance I passes Equation 3 obtains:

Among them, h is the reactance height.

The length of the lower yoke 302 is equal to the length of the upper yoke 301, and the length l of the _upper yoke 301 is:

Among them, _next to γ is the rated insulation distance of the side yoke;

The height of the first side yoke 303 is equal to the height of the second side yoke 304, and the height of the first side yoke 303 and the height l of the second _side yoke 304 are:

l _side =h+ _γup + _γfollowing formula 5;

Wherein, the _upper γ is the rated insulation distance of the upper yoke 301 , and the _{lower γ is the rated insulation distance of} the lower yoke 302 .

Specifically, the insulation distance is determined by the voltage level of the reactor. Generally speaking, the head-end voltage levels of the reactor are 110kV, 66kV and 35kV, and the terminal voltage is generally 35kV. Taking the highest head-end voltage of 110kV as an example, its insulation The distance is 80mm, and the insulation distance corresponding to the terminal voltage of 35kV is 60mm. Compared with the 440mm in the prior art, the volume of the body is greatly reduced, which also saves a lot of cost.

The cross section of the iron yoke 30 , that is, the magnetic conductive cross section is generally rectangular, or the vertical cross section of at least one side of the iron yoke is an arc shape. Here, the cross-section of the upper yoke 301 is an arched arc as an example, and the arc surface of the iron yoke side is the side away from the hollow coil 20 . The thickness on both sides of the edge increases towards the middle.

Specifically, since the iron yoke 30 itself is made of silicon steel sheets with high magnetic permeability, and the thickness of the laminations is increased in the middle of the sides of the iron yoke, the magnetic resistance can be reduced to a certain extent. Moreover, since the magnetic flux passing through the middle of the iron yoke side is the most, the middle of the iron yoke side can be thickened to balance the magnetic flux, so that the magnetic flux passing through the iron yoke 30 is relatively uniform, avoiding a certain iron yoke 30 Excessive magnetic flux on it leads to problems such as temperature rise.

As shown in FIG. 4 , in order to overcome the problem that the iron yoke 30 may be loosely installed and fall off when the reactor operates to generate noise or vibration, according to the neutral point grounding reactor with a magnetization enhancement structure according to the present invention, Also includes a fastening frame 40 for clamping and fixing the iron yoke 30, the fastening frame 40 is a cubic frame composed of several fastening plates, the iron yoke 30 is placed inside the fastening frame 40, and the fastening frame 40 includes two rectangular frames 401 and a plurality of connecting plates 402 for connecting the two rectangular frames 401, one rectangular frame 401 is arranged along the circumference of the upper yoke, the other rectangular frame 401 is arranged along the circumference of the lower yoke, and the connecting plates 402 are fixedly connected to the rectangular frame 401. The four corners are used to clamp the first side yoke 303 and the second side yoke 304 . Several reinforcing plates 403 are disposed on the top surface or/and the bottom surface of the fastening frame 40 , and the reinforcing plates 403 are arranged along the lamination direction of the iron yoke 30 .

Here, the fastening bracket 40 is mainly to increase the anti-vibration capability of the iron yoke 30 . The fastening frame 40 can be tightly clamped in the lamination direction and the thickness direction of the upper yoke 301 and the lower yoke 302, and also tightly clamped in the thickness direction of the first side yoke 303 and the second side yoke 304, increasing the iron yoke 30 working reliability.

Both the iron yoke 30 and the fastening frame 40 are connected with insulation. One end of the fastening plate is electrically connected with other fastening plates, and the other end is insulated with other fastening plates.

Specifically, the four connecting plates 402 are all insulated with the top rectangular frame, and are all electrically connected with the bottom rectangular frame. The four sides of the rectangular frame are all connected at both ends to the other fastening sides, wherein one end is an electrical connection and the other end is an insulating connection. All the metal parts in the fastener frame 40 of the present invention are grounded at only one point, and there are no short-circuit rings in any orientation.

To sum up, the neutral point grounding transformer with a magnetization enhancement structure according to the present invention has the advantages of low cost, low loss, strong stability and good reliability.

The above examples only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

A neutral point grounding reactor with a magnetization enhancement structure is characterized in that it includes: an oil tank, a hollow coil without an iron core column arranged inside the oil tank, and a rectangular iron yoke, the iron yoke includes four iron yoke sides, four iron yoke sides The sides of the iron yoke are connected end to end, including an upper yoke located at the top of the hollow coil, a first side yoke located on one side of the coil, a lower yoke located at the bottom of the hollow coil, and the other side of the coil. the second side yoke; the first side yoke, the second side yoke and the central axis of the hollow coil are parallel and coplanar; the central axis of the hollow coil passes through the center point of the iron yoke, so The magnetic lines of force generated after the air-core coil is energized all pass through the iron yoke.
The neutral point grounding reactor with a magnetization enhancement structure according to claim 1, wherein the iron yoke is composed of a plurality of iron yoke sheets, and the material of the iron yoke sheets is silicon steel.
A neutral point grounding reactor with a magnetization enhancement structure according to claim 2, characterized in that: the thicknesses of the four iron yoke sides of the iron yoke are equal, and the thickness δ of the iron yoke sides is calculated by formula 1 get:

Among them, B is the magnetic flux density, r is the inner radius of the air-core coil, and p is the radial thickness of the air-core coil;

in,
is the total magnetic flux generated by the air-core coil, the total magnetic flux
Obtained by Equation 2:

Among them, w is the number of turns of the air-core coil, k is the magnetization coefficient, and I is the air-core coil current;

Among them, L is the inductance generated when the air-core coil is energized without magnetic shielding, and the inductance L is obtained by formula 3:

Among them, h is the reactance height, and r is the outer radius of the hollow coil.
A neutral point grounding reactor with a magnetization enhancement structure according to claim 3, wherein the length of the lower yoke is equal to the length of the upper yoke, and the length l of the upper yoke 4 Get:

Among them, next to γ is the rated insulation distance of the side yoke;

The height of the first side yoke is equal to the height of the second side yoke, and the height of the first side yoke and the height l of the second side yoke are obtained by formula 5:

l side =h+ γup + γfollowing formula 5;

Among them, the upper γ is the rated insulation distance of the upper yoke, and the lower γ is the rated insulation distance of the lower yoke.
A neutral point grounding reactor with a magnetization enhancement structure according to claim 1, characterized in that it further comprises a fastening frame for clamping and fixing the iron yoke, and the fastening frame is composed of several fastening plates a cube frame, the iron yoke is placed inside the fastening frame, the fastening frame includes two rectangular frames and a plurality of connecting plates for connecting the two rectangular frames, one of the rectangular frames is along the The upper yoke is arranged in the circumferential direction, the other rectangular frame is arranged along the circumferential direction of the lower yoke, and the connecting plate is fixedly connected to the four corners of the rectangular frame to clamp the first side yoke and the second yoke. Second yoke.
A neutral point grounding reactor with a magnetization enhancement structure according to claim 5, characterized in that: a plurality of reinforcing plates are arranged on the top surface or/and the bottom surface of the fastening frame, and the reinforcing plates are arranged along the The lamination direction of the iron yoke is arranged.
The neutral point grounding reactor with a magnetization enhancement structure according to claim 5, wherein the iron yoke and the fastening frame are all connected with insulation.
A neutral point grounding reactor with a magnetization enhancement structure according to claim 5, characterized in that: one end of the fastening plate is electrically connected to other fastening plates, and the other end is insulated from the other fastening plates connect.