JP2001518698A - How to fit power transformers / reactors with high voltage cables - Google Patents

Abstract

The present invention relates to a power transformer / reactor including at least one winding (1, 2, 3). A winding (1, 2, 3) is provided with a conductor, a first semi-conductive layer (14) arranged around the conductor, and a periphery of the first semi-conductive layer (14). Manufactured with a high-voltage cable (10) including a first insulating layer (16) which is provided and a second semiconductive layer (18) disposed around the first insulating layer (16). ing. The second semiconductive layer (18) is directly grounded at n points of each winding (1, 2, 3), where n is an integer and n ≧ 2, Two of the direct ground locations (32, 34) are located at or near both ends of each winding (1, 2, 3), and in the second semiconductive layer (18). Electrical contact is interrupted (20) 2 (n-1) times between both ends. In order to reduce the amplification of the electric field strength at said interruptions (20), each of said interruptions (20) comprises means (24, 24) comprising a second insulating layer (24) and a third semiconductive layer (26). 26) are arranged. The second semiconductive layer (18) of the various phases (1, 2, 3) in each of the interruptions (20) is grounded in a cross-connect (42, 44). In addition, at least one point (36, 38) between the two ends is indirectly grounded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates in a first aspect, to a power transformer / reactor. A second aspect of the invention relates to a method of adapting a high voltage cable to a power transformer / reactor winding.

[0002] Transformers are used in all of the transmission and distribution of electrical energy, the function of which generally allows the exchange of electrical energy between two or more electrical systems having different voltage levels from one another. It is to be. Transformer is 1VA to 100
Available in all power ranges up to the 0 MVA range. Regarding the voltage range,
There are spectra up to the highest transmission voltage currently used. Electromagnetic induction has been used for the transfer of energy between electrical systems.

[0003] Regarding the transmission of electrical energy, for example, a reactor is also included as an essential component for phase compensation and filtering. The transformer / reactor according to the invention belongs to the so-called power transformer / reactor having a rated output in the range of several hundred kVA to more than 1000 MVA and a rated voltage in the range of 3-4 kV to very high transmission voltage. ing. BACKGROUND OF THE INVENTION From a purely general point of view, the main function of a power transformer is generally the electrical energy between two or more electrical systems having different voltages and the same frequency as each other. Is to allow for the exchange.

[0004] Conventional power transformers / reactors include a transformer core, hereinafter referred to as a core, usually formed of laminated (preferably directional) sheets of silicon steel. This core consists of several iron legs connected by a yoke. Several windings, commonly referred to as primary, secondary and regulating windings, are provided around the core legs. For power transformers, these windings are in fact always arranged concentrically and distributed along the length of the iron leg.

[0005] Other types of core structures may be used, such as the core of a so-called core or toroidal transformer. Examples of the core structure are eg DE 4
0414. The core is composed of a conventional magnetizable material such as the directional iron plate and other magnetizable materials such as ferrite, amorphous material, wire strands, or metal tape. It is known that a reactor does not require a magnetizable core.

[0006] The windings constitute one or more coils connected in series, which coils are constituted by several turns connected in series. Generally, a single coil turn constitutes a morphologically continuous unit that is physically separated from the other coils. Insulation systems that are partially on the inside of the coil / winding and partially between the coil / winding and other metal components are generally solid cellulose or closest to the separate conductive element. In the form of a varnish-based insulator, the outer insulator is a solid cellulose insulator, a fluid insulator, and possibly a gaseous insulator. A winding with insulators and possibly large components thus exhibits a large volume which is subject to high electric field strengths occurring inside and around the useful electromagnetic part belonging to the transformer. Detailed knowledge of the properties of the insulating material is required to predetermine the strength of the generated electric field and to obtain dimensions that minimize the risk of electrical failure. Furthermore, it is indispensable to realize an ambient environment that does not cause a change in insulation characteristics and a deterioration in insulation characteristics.

[0007] The most widely used external insulation system for conventional high voltage transformers / reactors at present consists of cellulosic material for solid insulation and transformer oil for fluid insulation. Transformer oil is mainly composed of so-called mineral oil. In addition to this, conventional insulators are relatively complex configurations, and special measures must be taken during manufacture to use the excellent insulation properties of the insulation system.
The insulation system must have a low moisture content, the solid phase in the insulation system must be sufficiently impregnated with the surrounding liquid, and the possibility of gas pockets remaining in the solid phase must be minimized. During manufacture, a special drying process is performed on the entire wound core before the entire wound core is lowered into the tank. After the core is lowered and the tank is sealed, and before the tank is filled with oil, all air in the tank is removed by a special vacuum treatment. This process is relatively time consuming in view of the overall manufacturing process, in addition to requiring extensive use of resources at the workplace.

[0008] The tank surrounding the transformer is formed to be able to withstand a full vacuum, as the process requires that all gas be evacuated so that the tank is approximately in an absolute vacuum. And this involves extra material consumption and manufacturing time. In addition, vacuum treatment is required again during installation on site and the process must be repeated each time the transformer is opened for maintenance or inspection. SUMMARY OF THE INVENTION A power transformer / reactor according to the present invention includes at least one winding, which is typically located around various forms of a magnetizable core. The term “winding” will preferably mean the following to simplify the following specification. This winding is formed of a high voltage cable having a solid insulator. The cable comprises at least one concentrically disposed conductor having a first semiconductive layer disposed thereabout, and a solid first insulating layer disposed around the first semiconductive layer. Are arranged, and an outer second semiconductive layer is arranged around the insulating layer.

Yet another advantage is that the layers are arranged to adhere to each other even when the cable is bent. In this way, proper contact between the layers is achieved over the life of the cable. The second semiconductive layer is directly grounded at n locations in each winding, where n is an integer and n ≧ 2, and two of the direct grounding locations are at opposite ends of each winding. Or it is located near both ends. In the second semiconductive layer, the electrical contact is 2 (n-1).
) Has been interrupted only times. Various phases of second semiconductive layers are grounded in a cross-connect at each of the interruptions.

According to the invention, a method for adapting a high-voltage cable to the windings of a voltage transformer / reactor comprises: directly grounding said second semiconductive layer at n points of each winding; Wherein n is an integer and n ≧ 2, two of said locations being located at or near both ends of each winding; and, between each pair of direct ground locations, a second Obtaining two breaks in the electrical contact in the semiconductive layer; and grounding the second semiconductive layer in a cross-connection at various phases of each of the breaks.

[0011] The use of such a cable means that the area of the transformer / reactor subjected to electric field stress is limited to the solid insulation of the cable. For high voltage applications, the other parts of the transformer / reactor only experience very moderate field strength. Furthermore, the use of such a cable eliminates some of the problems mentioned in the background of the present invention. For example, no tank for the insulating medium and the refrigerant is required. In addition, the insulator is significantly simplified. The assembly time is significantly shorter than the assembly time of a conventional power transformer / reactor. The windings may be manufactured separately, and the power transformer / reactor may be assembled on site.

However, the use of such cables introduces new problems that must be solved. The outer semiconductive layer is directly at or near both ends of the cable such that electrical stresses that occur during both normal operating voltage and transients primarily load only the solid insulator of the cable. Must be grounded. In addition to such a direct ground, the semiconductive layer forms a closed circuit in which current is induced during operation. The resistance of this layer must be large enough so that the resistive losses in this semiconductive layer are negligible.

In addition to this magnetically induced current, a capacitive current will flow into the layer through direct grounding at both ends of the cable. If the resistance of the layer is too high, the capacitive current will be very low, so that during alternating stresses, areas of the power transformer / reactor other than the solid insulation of the winding will be electrically disconnected. To the extent that it is stressed, the potential of each portion of the layer may differ from ground potential. Interrupting electrical contact in the second semiconductive layer between both ends of the cable n times,
Where n is an integer and n ≧ 1 and by grounding the second semiconductive layers at various phases in each of the interruptions in a cross-connect manner, Current is eliminated and power loss is minimized.

An interruption in the second semiconductive layer outside the high voltage cable will result in an increase in the electric field strength at the edge of the second semiconductive layer at the point of interruption. This increase in field strength obviously increases the risk of electrical failure. By placing means including a second insulating layer and a third semiconductive layer at each break in the second semiconductive layer, the risk of this electrical failure is minimized.

[0015] In extreme cases, the windings are subject to rapid transient overvoltages, so that a portion of the outer semi-conductive layer may have undesired electrical transformer areas other than cable insulation. It may have a potential that is stressed. To prevent such situations from occurring, some non-linear elements, such as spark gaps, gas diodes, zener diodes or varistors, are connected between the layer and ground in each phase. By connecting a capacitor between the outer semiconductive layer and ground, undesirable electrical stresses are also prevented. 50H
Even at z, the capacitor reduces voltage stress. This principle of grounding is hereinafter referred to as “indirect grounding”.

The points which are indirectly grounded include: a non-linear element such as, for example, a spark gap or a gas diode; a non-linear element in parallel with a capacitor; a capacitor; or a combination of these three alternatives. Connected to the ground. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 is a cross-sectional view of a high-voltage cable 10 conventionally used for transmitting electrical energy. The high voltage cable 10 shown in this figure may be, for example, a standard XLPE cable 145 kV without a jacket and a screen. The cable 10 used in the present invention is flexible and is described in WO 97/4591.
No. 9 and WO 97/45847 are cables of the kind described in more detail. Additional information on this cable is given in WO 97/45918, WO
97/45930, WO 97/44931. The high voltage cable 10 has a conductor that may comprise one or several strands 12 having a circular cross section, for example, of copper (Cu). These wires 12 are arranged at the center in the high-voltage cable 10. Around the element wire 12, a first semiconductive layer 14 is arranged. Around the first semiconductive layer 14, for example, an XLPE insulator,
Are disposed. Around the first insulating layer 16, a second semiconductive layer 18 is arranged.

In FIG. 1, which shows details of the invention with respect to cable 10, three layers 14, 16, 1
8 are arranged to adhere to each other even when the cable 10 is bent. The cable 10 shown in this figure is flexible and this property is maintained throughout the life of the cable. Thus, in the arrangement according to the invention, the winding is of a type corresponding to a cable comprising a solid extruded insulation of the type currently used for power distribution, such as an XLPE cable or a cable with an EPR insulation. Is preferred. Such a cable includes an inner conductor composed of one or more strands, an inner semiconductive layer surrounding the conductor, a solid insulating layer surrounding the insulating layer, and an outer semiconductive layer surrounding the insulating layer. In the present invention, the cable is flexible, since such a cable is flexible and the technology for the construction according to the invention is basically based on a winding system in which the winding is formed by a cable that is bent during the assembly. Flexibility is an important property. The flexibility of an XLPE cable generally corresponds to a radius of curvature of about 20 cm for a cable of 30 mm diameter and to a radius of curvature of about 65 cm for a cable of 80 mm diameter. In this application, the term "flexible" refers to a radius of curvature of about four times the cable diameter, preferably about eight times the cable diameter.
It means that it is possible to bend from a double to a 12-fold radius of curvature.

The winding must be configured to retain its properties, even when the winding is subjected to thermal or mechanical stresses during bending and operation. For this reason, it is particularly important that the layers remain adhered to each other. In this case, the material properties of each layer are extremely important, and in particular, the elasticity and relative thermal expansion coefficient of each layer are particularly important. For example, in the case of an XLPE cable, the insulating layer is made of cross-linked low density polyethylene, and the semiconductive layer is made of polyethylene mixed with soot and metal particles. The change in volume as a result of temperature fluctuations is completely absorbed as the change in radius of the cable, and the difference in the coefficient of thermal expansion between each layer with respect to the elasticity of these materials is relatively small, so that the radial expansion is It can occur without loss of adhesion between the two.

The above material combinations should be regarded only as examples. Naturally, other conditions satisfying the above conditions and the condition of being semiconductive, that is, having a resistivity within the range of 10 ^-1 to 10 ⁶ Ωcm, for example, having a resistivity of ¹ to 500 Ωcm or 10 to 200 Ωcm. Combinations are also within the scope of the present invention. The insulating layer is made of a solid thermoplastic material such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polybutylene (PB), polymethylpentene (“TPX”), or cross-linked polyethylene (LDP). XLP
It may consist of a cross-linking material such as E) or a rubber such as ethylene propylene rubber (EPR) or silicone rubber.

The inner and outer semiconductive layers may be the same basic material as described above, except that conductive material particles such as soot or metal powder are incorporated. The effect of the mechanical properties of these materials, especially their coefficient of thermal expansion, whether or not soot or metal powder is incorporated, is needed to at least achieve the electrical conductivity required in the present invention. The proportion of soot or metal powder is only relatively small. Therefore, the insulating layer and the semiconductive layer have substantially the same coefficient of thermal expansion.

Ethylene-vinyl acetate copolymer / nitrile rubber (EVA / NBR), butyl-grafted polyethylene, ethylene-butyl acrylate copolymer (EBA), and ethylene-ethyl acrylate copolymer (EEA) are also suitable for the semiconductive layer. It is possible to make up a polymer. Even when different types of materials are used as the base material for each of the layers, it is desirable that the materials have substantially the same coefficient of thermal expansion. This also applies to the above material combinations.

The material has a relatively high elasticity, E <500 MPa, preferably E <20
It has an elastic modulus E of 0 MPa. This elasticity is large enough that small differences between the coefficients of thermal expansion of the materials of the layers are absorbed in radial elasticity, so that cracks and other damage do not appear, and The layers are not separated from each other. The material of each layer is elastic and the adhesion between each layer is at least as large as the weakest material of each layer material.

The conductivity of the two semiconductive layers is large enough to substantially equalize the potential along each layer. The conductivity of the outer semiconductive layer is high enough to confine the electric field within the cable, but low enough not to cause significant losses due to the current induced in the longitudinal direction of that layer. . Thus, each of the two semiconductive layers substantially constitutes one equipotential surface, substantially confining the electric field therebetween.

Of course, nothing prevents the placement of one or more additional semiconductive layers within the insulating layer. FIG. 2A is a partial cross-sectional view of a high-voltage cable having a break in a second semiconductive layer to illustrate the amplification of the electric field strength at the edge of the break. The cross section shown in FIG. 2A extends along the long axis of the high voltage cable. FIG. 2B is a perspective view of a portion of the cable shown in FIG. 2A. Similar parts in FIGS. 2A and 2B are indicated by the same reference numerals. The strands 12 are only schematically shown in FIG. 2A. As shown in FIGS. 2A and 2B, the second semiconductive layer 18 has been removed in a ring around the high voltage cable 10, thus forming a groove 20. Thus, the first insulating layer 16 is exposed in the groove 20. By realizing this break in the electrical contact located between the two ground points in the second semiconductive layer 18, no current will flow and therefore no heat loss due to the induced voltage will occur. However, all interruptions in the second semiconductive layer 18 cause an amplification of the field strength on both sides of the interruption. As shown in FIG. 2A,
The electric field lines are shown (indicated by reference numeral 22). At the edge of the groove 20 there is a concentration of the electric field lines 22 which means that the electric field strength shows a sudden amplification. This unfortunately results in an increased risk of discharge, and therefore the goal is to strive to prevent this discharge from occurring.

FIG. 3 shows a cross section along the cable long axis of a high voltage cable having means for reducing the amplification of the electric field strength at the point of interruption. The high voltage cable 10
As with the high-voltage cable according to FIG. 1, it comprises the following elements: a strand 12, a first semiconductive layer 14, a first insulating layer 16 and a second semiconductive layer 18. As shown in FIG. 3, the second semiconductive layer 18 has been removed in a ring around its periphery, resulting in a groove 20 and exposing the first insulating layer 16. . As shown in FIG. 3, the groove 20 has a downwardly sloping edge, that is, the groove 20 has a width greater than the width in the first insulating layer 16 and the second semiconductive layer 18. On the upper edge of Downwardly sloping edges are advantageous, but grooves 20
For example, it may have a straight edge. The distance between the edge of the second semiconductive layer 18 and the edge of the first insulating layer is shown in FIG. The width b of the groove 20 is preferably 10 mm. In addition to this, the high-voltage cable 10 includes a second insulating layer 24 that is specially applied over the groove 20, so that the groove 20 is filled. The reason for having a beveled edge in the groove 20 is that a special filling of the groove 20 with a suitable insulating material, for example an insulating "self-fusing" ERP tape such as an insulating tape IV-tape® from ABB Kabeldon When the second insulating layer 24 is formed by
This is to prevent a hollow space from being formed at the edge. The second insulating layer 24
The inclined edge of the second semiconductive layer 18 and a part of the second semiconductive layer 18 reaching the inclined edge are covered. In addition to this, the high-voltage cable 10 is, for example, an ABB Kabe
A third semiconductive layer 26, which is in the form of a tape such as the semiconductive tape HL-tape®, IA2352 made by Idon, comprising a third semiconductive layer 26,
One end of the third semiconductive layer 26 covers one edge of the second insulating layer 24,
And second insulating layer 2 so as to have electrical contact with second semiconductive layer 18.
4 is attached. The other end of the third semiconductive layer 26 does not cover the other side of the second insulating layer 24 and stops at a position separated by a distance c from the other end of the second insulating layer 24. At the edges where the second semiconductive layer 24 is not covered by the third semiconductive layer 26, the second insulating layer 24 should be at least 1 mm thick. However, a third semiconductive layer 26 must be extended at the other end over the second semiconductive layer 18 located below the second insulating layer 24 (overlapping). There must be). The distance between the edge of the third semiconductive layer 26 and the edge of the second semiconductive layer 18 in the longitudinal direction of the cable 10 is d, as shown in FIG. Third semiconductive layer 26 should be at least 1 mm thick.

FIG. 4 schematically illustrates the principle of grounding for a three-phase power transformer / reactor according to the invention. The windings have been drawn out for clarity.
In addition, the core of the three-layer power transformer is omitted. The three-phase power transformer comprises three windings 1, 2, 3 realizing various phases 1, 2, 3. Winding 1, 2, 3
Are constituted by the high-voltage cable 10 shown in FIG. Cables for the various phases are shown as 10 ₁ , 10 ₂ , 10 ₃ . The second semiconductive layer 18 of each high voltage cable 10 ₁ , 10 ₂ , 10 ₃ is directly grounded at points 32, 34 located at or near both ends of each winding 1, 2, 3. ing.
Generally speaking, the second semiconductive layer 18 is directly grounded at n locations in each of the windings 1, 2, 3 where n is an integer and n ≧ 2, Two of the direct grounding locations are located at or near both ends of each of the windings 1,2,3. This direct grounding is provided by a galvanic connection to ground. In addition to this,
Electrical contact in the semiconducting layer is interrupted twice for each winding 1, 2, 3 20 ₁₁ , 2
0 _21, 20 _31, 20 _12, 20 _22, 20 ₃₂ are. Electrical contact in the second semiconductive layer 18 is typically interrupted 2 (n-1) times for each winding 1,2,3. Even in the case not shown in FIG. 4, in order to reduce the amplification of the electric field strength at the interruption points 20, the second insulating layer 2 is provided at each of these interruption points 20.
Means 24, 26 comprising a fourth and third semiconductive layer 26 may be arranged. These means 24, 26 are shown in FIG. Second semiconductive layer 1 of three phases 1, 2, 3
8, is grounded by the technique of cross-connection in each of the interrupt location 20 _11, 20 _21, 20 _31, 20 _12, 20 _22, 20 _32. In addition, three phases 1, 2, 3
The second semiconductive layer 18 is indirectly grounded at two points 36, 38. Generally speaking, the number of indirect grounding locations may vary. In the example shown here, indirect grounding is provided by the spark gap 40. Indirect grounding may be performed in a number of different ways, for example, as described above under the heading "Summary of the Invention" and as shown in FIGS. 6a, 6b. Cross connection ground 42, 4
4, the interrupt location 20 _11, 20 _21, 20 _31, 20 _12, 20 _22, 20 ₃₂ are indirectly grounded by which and the spark gap 40 is connected in each phase 1,2,3 a This is realized by two semiconductive layers 18.

The power transformer 30 of FIG. 4 has two interruption points 20 for each of the phases 1, 2, and 3.₁₁, 20 ₁₂ , 20_{twenty one}, 20_{twenty two}, 20₃₁, 20₃₂And therefore each phase 1, 2, 3
Three consecutive portions 18 of the second semiconductive layer 18₁₁, 18₁₂, 18₁₃; 18_{twenty one} , 18_{twenty two}, 18_{twenty three}; 18₃₁, 18₃₂, 18₃₃It has. First interruption point 20 ₁₁ Now, the first portion 18 of the second semiconductor layer 18 of the first phase 1₁₁Is the second phase
Second part 18 of 2_{twenty two}It is connected to the. In addition to this, the first phase 1
Part 18₁₁Is the first part 18 of the other phases 2,3_{twenty one}, 18₃₁Connected to
And it is connected to indirect grounding by a spark gap 40. The first of the second phase 2
Part 18 of_{twenty one}Is the second part 18 of the third phase 3₃₂It is connected to the. In addition to this
The second part 18 of the first phase 1₁₂But indirect grounding by spark gap 40
It is connected to the. Correspondingly, the cross-connected ground is connected to the second interruption point 20.₁₂ , But the description will not be repeated here. Ground in this cross-connect form
Another way to explain is that after the connection from the direct grounding point to the next grounding point
It is to continue. Starting directly at the ground point 32 and thereafter the first of the first phase 1
Part 18₁₁Followed by the first part 18₁₁Is the second part 18 of the second phase 2_{twenty two}To
Connected to this second part 18_{twenty two}Is the third part 18 of the third phase 3₃₃Contact
This third part 18₃₃Is directly connected to the ground point via the point 34.
You. Therefore, part 18_{twenty one}-18₃₂-18₁₃Is directly between both ground points 32 and 34
It is connected to the. Correspondingly, part 18₃₁-18₁₂-18_{twenty three}Is directly grounded
Connected between both locations 32,34. However, power transformers / reactors
The general description of grounding in the form of cross-connects in
This is shown below for the case where there are several.

Generally speaking in terms of one case, the second semiconductive layer 18 is
, 3 where n is an integer and n ≧ 2, and two of the n direct grounds are at both ends of each winding 1, 2, 3 Or near both ends. This means that the electrical contact is 2 (n-1) across the second semiconductive layer 18 in view of the presence of two breaks 20 between each pair having a direct ground. It means that it has been interrupted 20 times. This means that for each winding 1, 2, 3 there are 3 (n-1) parts of the second semiconducting layer 18, where one part is directly at the ground point or interruption. It starts at point 20 and ends at interruption point 20, ie, a direct ground contact.

The interruption points 20 number q of various phases (where 1 ≦ q ≦ 2 (n−1)) are connected to the portion (r + 1) of the second semiconductive layer 18 of the subsequent phase. There is a portion r of the second semiconductive layer 18 of one phase, where 1 ≦ r ≦ 3 (n−1).
In addition, the first phase portion r is connected to the other phase portions r. The last phase portion r and the first phase portion (r + 1) are connected by spark gap 40 to indirect grounding. The above does not apply to r exactly divisible by 3 except for the last part, ie, for a given n, r = 3 (n
This does not apply to r which is -1).

FIG. 5 shows a diagram illustrating the potential of the second semiconductive layer 18 extending along the length of the cable. A power transformer with a Y-connection winding is taken up in this case. In this case, this means that the voltage on the second semiconductive layer of the cable winding decreases linearly from the HV connection to the neutral point under AC voltage. Direct grounding points are denoted by A and D, and two points for cross-connect grounding are denoted by B and C. Furthermore, direct grounding point A, the distance between D is L, the distance between A and B and l _1, the distance between B and C and l _2, C and D l ₃ the distance between the And The ratio between the distances l, l ₂ , l ₃ is l ₁ <l ₂ <l ₃ and, as shown in FIG. Have the same value, the current is zero in the second semiconductive layer, which means that the power loss in the second semiconductive layer will be negligible. The distances l _{1 to} l ₃ and L depend on the dimensions of the wound cable as well as on the thickness and resistance of the second semiconductive layer.

FIGS. 6 a and 6 b each illustrate different elements for achieving indirect grounding. In FIG. 6 a, indirect grounding is provided by a circuit 50 comprising one element 52 having a non-linear voltage-current characteristic connected in parallel to a capacitor 54. In the case shown in this figure, an element 52 having a non-linear voltage-current characteristic is designed to have one spark gap 52. The element 52 may be designed with a gas diode, a Zener diode or a varistor filled with gas. In FIG. 6b, indirect grounding is realized by Zener diode 56.

FIG. 7 shows a conductor, a first semi-conductive layer 14 disposed around the conductor, and a first insulating layer 16 disposed around the first semi-conductive layer. And a second semiconductive layer 18 disposed around the first insulating layer 16.
2 shows a flowchart illustrating a method for adjusting (compare FIG. 1). The method according to the invention comprises several steps described below. The flowchart starts at block 60. The next step is to cause the second semiconductive layer 18 to be indirectly grounded 32, 34 at n locations in each winding 1, 2, 3 in block 62, where n is an integer and n ≧ 2 and 2 out of the n places
Are located at or near both ends of each winding 1,2,3. Then, at block 64, two breaks 20 are realized between each pair of indirect grounding points at electrical contact in the second semiconductive layer 18. Then, block 6
At 6, means 24, 26 are applied to each of the interruptions 20 in the second semiconductive layer 18, these means being adapted to reduce the amplification of the electric field at the interruptions 20 by a second An insulating layer and a third semiconductive layer are provided. Then, at block 68, the second semiconductive layers of the various phases 1, 2, 3 are grounded in a cross-connect manner at each of the breaks 20. Then, at block 70,
At least one location 36, 38 of the second semiconductive layer 18 of each phase 1, 2, 3
Indirectly grounded between both ends. The method ends at block 72. See FIGS. 2-6 for further details regarding this method.

The power transformer / reactor can be manufactured using a magnetizable core or without a magnetizable core. The invention is not limited to the embodiments described above, but can be modified in certain ways within the scope of the appended claims.

[Brief description of the drawings]

FIG. 1 is a sectional view of a high-voltage cable.

FIG. 2A is a partial cross-sectional view of a high voltage cable having a break in a second semiconductive layer to show the amplification of the electric field at the edge of the break.

FIG. 2B is a perspective view of a portion of the cable shown in FIG. 2A.

FIG. 3 is a cross-sectional view along the long axis of the cable of a high-voltage cable having means for reducing the amplification of the electric field strength at the interruption point.

FIG. 4 shows a schematic principle of the grounding of a three-phase power transformer according to the invention.

FIG. 5 is a diagram showing a potential of a second semiconductive layer related to a length of a cable.

FIG. 6 shows different elements for obtaining indirect grounding, respectively.

FIG. 7 is a flowchart of a method for adapting a high-voltage cable according to the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP , KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (72) Inventor Yaksz, Albert Sweden, S-72243 Base Telose, Ecolebergen 13 F-term (reference) 5E058 BB17 5G309 LA20 LA21 MA18 [Continuation of summary] are grounded in the form of cross-connects (42, 44). In addition, at least one point (36, 38) between the two ends is indirectly grounded.

Claims (27)

[Claims] 1. A power transformer / reactor comprising at least one winding (1, 2, 3), wherein said winding (1, 2, 3) comprises a conductor and a conductor surrounding said conductor. A first semiconductive layer (14) disposed, a first insulating layer (16) disposed around the first semiconductive layer (14), and the first insulating layer (16). ), And a second semiconductive layer (18) disposed around the windings (1, 2). 2, 3) are directly grounded (32, 34) where n is an integer and n ≧ 2, and two of the n direct grounded locations ( 32, 34) are each winding (
1, 2, 3), wherein the electrical contact is interrupted 2 (n-1) times between its ends in the second semiconductive layer (18) ( 2
0) and each said phase (1, 2,...) In each of said interruptions (20)
3) The power transformer / reactor according to (3), wherein the second semiconductive layer (18) is grounded in a cross-connect manner (42, 44). 2. The power transformer / reactor according to claim 1, wherein at least one point (36, 38) between the two ends is indirectly grounded (40). 3. A third semiconductive layer (26) for each said interrupt (20) of said second semiconductive layer (18) to reduce the amplification of the electric field strength at said interrupt (20).
2. The power transformer / reactor according to claim 1, further comprising: 4. A trench (20) is formed, wherein the electrical contact in the second semiconductive layer (18) is interrupted and a groove (20) surrounded by the second semiconductive layer (18). As described above, the second semiconductive layer (18) is formed by the first insulating layer (16).
4. The power transformer / reactor according to claim 1, wherein the power transformer / reactor is removed around the high-voltage cable (10). 5. 5. The second insulating layer (24) is disposed on each of the grooves (20), and in addition, the layer (24) is disposed on both sides of each of the grooves (20). And covering a part of the second semiconductive layer (18);
26) is disposed on the second insulating layer (24), and the third semiconductive layer (2)
6) one end covers one edge of the second insulating layer (24) and has an electrical contact with the second semiconductive layer (18); and Conductive layer (26)
Does not cover the other edge of the second insulating layer (24), and is located under the second insulating layer (24). The power transformer / reactor of claim 4, wherein the power transformer / reactor extends along a portion of (18). 6. An edge of said second insulating layer (18) in said groove (20) is sloped such that said groove (20) has a minimum width in said first insulating layer (16). The power transformer / reactor according to claim 5, wherein: 7. The third semiconductive layer (26) comprises the second insulating layer (24).
At the end covering the edge of the second semiconductive layer (18), and the other end of the third semiconductive layer (26) Semiconductive layer (1
7. The power transformer / reactor according to claim 6, wherein the power transformer / reactor is not in mechanical or electrical contact with (8). 8. The cable according to claim 1, wherein the high-voltage cable has a conductor area of 80 to 3000 mm ² and a cable outer diameter of 20 to 250 mm. A power transformer / reactor according to claim 1. 9. The power transformer according to claim 1, wherein there are two interruptions (20) between two successive direct grounding points (32, 34). Reactor. 10. In each said interruption (20) which is connected and indirectly grounded (40), said second semiconductive layer (1) in different phases (1, 2, 3).
8. The method according to claim 1, wherein each cross-connection ground is formed by (8).
A power transformer / reactor according to any one of claims 1 to 8. 11. 2 (n-1) interruptions per phase (20₁₁, 20₁₂;
20_{twenty one}, 20_{twenty two}; 20₃₁, 20₃₂) And therefore the second per phase
3 (n-1) connection portions (18₁₁, 18₁₂, 18₁₃; 18_{twenty one}, 18 _{twenty two} , 18_{twenty three}; 18₃₁, 18₃₂, 18₃₃) And various phases (1, 2, 3
(20) number q (where 1 ≦ q ≦ 2 (n−1))
Phase r (1, 2, 3) of the second semiconductive layer (18) (where 1 ≦ r ≦
3 (n-1)) is a portion (r) of the second semiconductive layer (18) in a subsequent phase.
+1) and the second semiconductor layer (18) in the first phase (1).
) Is a portion r of the second semiconductive layer (18) having another phase (2, 3).
And a portion of the second semiconductive layer (18) of the last phase (3)
And a portion (r + 1) of the second semiconductive layer (18) of the first phase (1).
Are connected to the indirect ground (40), in which case the above-mentioned pattern is
R, which is exactly divisible by 3, excluding the minute, ie, r = 3 (n-1)
11. A power transformer / reactor according to claim 10, wherein:
Tor. 12. The power transformer / reactor according to claim 1, wherein the direct grounding (32, 34) is provided by a galvanic connection to ground. 13. The method according to claim 1, wherein the indirect grounding is provided by a capacitor connected between the second semiconductive layer and ground. The described power transformer / reactor. 14. The device according to claim 1, wherein the indirect grounding is provided by an element connected between the second semiconductive layer and ground and having a non-linear voltage-current characteristic. The power transformer / reactor according to any one of claims 1 to 12. 15. A non-linear voltage-current characteristic (52) connected between said second semiconductive layer (18) and ground and in parallel with a capacitor (54). Power transformer / reactor according to any of the preceding claims, characterized in that it is performed by a circuit (50) comprising elements having: 16. The power transformer / reactor according to claim 15, wherein the indirect grounding is performed by a combination of alternatives according to claims 13 to 15. 17. The element (52) having a non-linear voltage-current characteristic comprises a spark gap (52), a gas-filled gas diode, a Zener diode (52).
56) A power transformer / reactor according to any one of claims 14 to 16, characterized in that it may be designed using varistors. 18. The power transformer / reactor according to claim 1, wherein the power transformer / reactor has a magnetizable core. 19. The power transformer / reactor according to claim 1, wherein the power transformer / reactor is manufactured without a magnetizable core. 20. The method as claimed in claim 1, wherein the layers are arranged so as to adhere to each other even when the cable is bent. Power transformer / reactor. 21. A high voltage cable (10) comprising: a conductor; a first semiconductive layer (14) disposed around the conductor; and a periphery of the first semiconductive layer (14). A power transformer / reactor winding comprising a first insulating layer (16) disposed at a first position and a second semiconductive layer (18) disposed around the first insulating layer (16). A method for conditioning a high-voltage cable (10) for a wire, wherein said second semiconductive layer (18) is directly grounded at n points of each winding (1, 2, 3). (32, 34), wherein n is an integer and n ≧ 2, and n
Two locations (32,34) of the two locations being located at or near both ends of each winding (1,2,3); and in the second semiconductive layer (18) Obtaining two interruptions (20) between each pair of direct grounding points in electrical contact; and, in each said interruption (20), said second semiconductive layer ( 18) grounding in the form of a cross connection. 22. The method according to claim 19, wherein at least one location (3) of each phase between both ends of the second semiconductive layer (18).
22. The method of claim 21, further comprising the step of indirectly grounding (6, 38). 23. The method according to claim 23, further comprising the step of: adding a third semiconductive layer to each of said interrupts (20) in said second semiconductive layer (18) to reduce the amplification of the electric field strength of said interrupt (20). The method according to any one of claims 21 to 22, further comprising the step of performing (26). 24. A trench (2) surrounded by said second semiconductive layer (18).
0) is formed by removing the second semiconductive layer (18) around the high voltage cable (10) until it reaches the first insulating layer (16). Method according to one of claims 21 to 23, wherein step (20) is realized. 25. The step of applying said means (24, 26) is such that each groove (20) is provided such that a portion of said second semiconductive layer (18) on each side of said groove (20) is additionally covered. 20) applying a second insulating layer (24) on top of the second insulating layer (24); one end of the third semiconductive layer (26) covers one edge of the second insulating layer (24); The second semiconductive layer (18) is in electrical contact with the second semiconductive layer (18), and the other end of the third semiconductive layer (18) is connected to the other end of the second insulating layer (24). The second semi-conductive layer (18) located below the second insulating layer (24) without covering the edges
Applying the third semiconductive layer (26) over the second insulating layer (24) so as to extend along a portion of the third semiconductive layer (24). 26. The step of grounding in the form of a cross-connect comprising: connecting the second semiconductive layers of various phases (1, 2, 3) at each of the interruptions (20); and 26. The method according to any one of claims 21 to 25, comprising the step of indirectly grounding. 27. interruptions per one phase 1 the number of (20 _11, 20 _12; 20 _21, 20 ₂₂ 20 _31, 20 ₃₂₎ 2 (n-1) is a number, the per phase one first 2
Connection portions of the semiconductive layer (18 _11, 18 _12, 18 _13; 18 _21, 18 _22, 18 _23; 1
8 ₃₁ , 18 ₃₂ , 18 ₃₃ ) is 3 (n−1), and the step of grounding in the form of the cross connection comprises the interruption (20) number q of various phases (1, 2, 3) (Where 1 ≦ q ≦ 2
(N-1)) said second semiconductive layer (18) in one phase (1, 2, 3)
Connecting a portion r (where 1 ≦ r ≦ 3 (n−1)) to a portion (r + 1) of the second semiconductive layer in a subsequent phase; and a first phase (1) The portion r of the second semiconductive layer (18) is changed to another phase (
2, 3) connecting to a portion r of the second semiconductive layer (18), and a portion r of the second semiconductive layer (18) of a final phase (3) to a first phase ( 1)
And the portion (r + 1) of the second semiconducting layer (18) is connected to the indirect ground (40), in which case the above pattern is exactly divisible by 3 except for the last portion, ie, , R = 3 (n−1), wherein r does not apply.