Busbar compensator for current conductors

Abstract

This utility model pertains to electrical engineering, specifically to compensating devices, and is used to eliminate vibration loads, compensate for displacements, and compensate for thermal expansion of busbars. The technical result is uniform current distribution over the disk surface while maintaining uniform mechanical load distribution across the entire circular profile of the busbar when stresses arise in the structure. To achieve this, the busbar compensator comprises two compensating disks, each containing two rows of circular openings connected by a stack of conductive plates. Each row contains seven openings, the centers of which are offset between the rows and relative to the midpoint of the distance between the openings in the row. The stack is made of 32 plates. 3 fig.

Description

[0001] The utility model relates to the field of electrical engineering, namely to the design of busbar compensators (flexible current conductors) used in high-current electrical circuits to compensate for thermal expansion, vibrations and electrodynamic forces.

[0002] The device can be used in the conductors of generators, synchronous compensators, powerful electric motors, distribution devices and other power equipment operating at currents from units to tens of kiloamperes.

[0003] Various designs of busbar compensators are known from the prior art, intended for creating a flexible electrical connection between elements of busbars.

[0004] The most common type is a multilayer flexible compensator, consisting of two contact plates (lugs) and a stack of thin metal plates (tapes) welded to these lugs. These compensators are widely used for connecting transformers, generators, and switchgear and are available with contact plates of standard widths (100, 200, 250 mm) (AC No. 191664). However, in such designs, the contact plates have a simple shape, and the mounting holes are typically arranged in a single row, which does not ensure optimal current distribution across the flexible package and can lead to localized overheating.

[0005] A known conductor compensator, according to Author's Certificate No. 191664, consists of two parts, one inside the other, with an elastic conductive element (sawtooth springs or Z-shaped inserts) placed between them. This solution is aimed at ensuring reliable current collection during coaxial movement of the conductor parts. However, this design is intended for tubular conductors and does not address the issue of uniform current distribution in disc contact assemblies.

[0006] A flexible current-carrying adapter-compensator is known, according to patent No. 2450089, comprising two busbar packages made of flexible metal strips of different metals with contact plates. This solution is aimed at eliminating internal losses at the junctions of dissimilar metals, but does not optimize the geometry of the mounting holes in the contact elements themselves.

[0007] A compensator is known, consisting of two parts with a built-in elastic element between them [Patent No. 106441].

[0008] From patent No. 2079942, a design of a high-reliability conductor for its use in seismic conditions is known, containing sections connected by couplings having compensators for axial movements.

[0009] A conductor is known according to patent JP 2010110186, containing sections connected by a coupling, wherein compensators for axial movements of the section relative to the coupling body are located in the coupling body, each compensator is made in the form of a zigzag plate, the ends of which are connected to the sections by bolts.

[0010] A busbar is known comprising conductive busbars, the adjacent contacts of which are located in a coupling housing and connected by at least one compensator for axial displacement of the sections in the coupling, and one additional coupling with an angular displacement compensator. Each axial displacement compensator is made of a plurality of copper plates connected to each other at their ends, forming a rigid parallelepiped-shaped element at each end (in the area of ​​​​the rigid connection of the plates). These elements are rigidly connected by bolted connections to the corresponding busbar contacts. In the middle section of the compensator, there are gaps between the plates, allowing one plate to shift relative to the other plate during the process of compensating for the displacement of the busbar sections. Each plate in its middle section is zigzag-shaped, curved away from the longitudinal axis of the coupling housing.Essentially, each axial displacement compensator for busbar sections is a compression spring operating within a variable range of elongation and contraction as the sections move axially due to heating during busbar operation (Patent No. 2439764). The busbar also includes a coupling with an angular displacement compensator, ensuring that the angle α changes within specified limits. Changes in angle α occur during busbar operation due to mechanical stress.

[0011] A known design of a thermal expansion compensator for a molded busbar with three busbars. The compensator consists of two insulated blocks with contact outlets for the busbars, housed in a protective casing. Electrical and mechanical connection of the blocks is achieved by elastic elements (one for each busbar), which are a set of 60 adjacent plates, 0.2 mm thick, covered with insulation [2: p. 130]

[0012] The installation of expansion joints and temperature compensators on busbars at section joints is known. Expansion joints, typically telescopic, are installed every 10-15 m at section joints. Temperature compensators on busbars are installed opposite the telescopic screen compensators [1: p. 25].

[0013] A compensator in the form of an annular plate of constant and variable thickness is known (Patents No. 1562652, No. 2382940, No. 2808070).

[0014] A closed conductor with a continuous shell is known, containing a current-carrying busbar secured to insulators, shielded by a shell with compensating elements, wherein the shell is made with profiling of circular compensating ridges (Patent No. 73555).

[0015] The TENE and TENP series shielded busbars are rated for voltages up to 35 kV and rated for currents up to 37.5 kA. They are designed for electrical connections in three-phase alternating current (AC) circuits with a frequency of 50 Hz at electrical installations at nuclear power plants and other electric power stations. The busbars are modular and comprise straight sections, angled and branch sections, sections with built-in equipment, sections with bushing insulators, apparatus connection units, splice units, units for insulating the casings from metal structures, units with air cooling circulation control devices, and units for sealing the remaining portion of the openings. All connections between the busbars and casings are welded (electrically continuous). The entire route of the busbar is welded. Forced air cooling is provided for the TENP busbars.A linear expansion compensator is installed on the buses and screen shells to compensate for linear changes caused by temperature changes (https: / / www.zeim.ru / production / tokoprovody / tene / ).

[0016] The shielded current conductor compensator of the TENE and TENP series is adopted as a prototype.

[0017] In known solutions, the arrangement of holes on the disks is either not specifically regulated (Patent No. 2123749), or is performed according to standard designs (one row, uniform pitch), which does not allow achieving an optimal combination of electrodynamic, thermal and mechanical characteristics under high current loads.

[0018] Therefore, there is a need to create a busbar compensator that ensures uniform current distribution across all plates of the stack, minimal eddy current losses, reduced mechanical stress on the disks and stable electrical contact over a wide range of operating temperatures and vibration loads.

[0019] The technical problem consists of expanding the arsenal of tools for a specific purpose, which is solved by creating a technical solution that is an alternative to a known solution (creating a variant of a known solution).

[0020] The technical result provided by the utility model consists of uniform current distribution over the surface of the disk while maintaining uniform distribution of the mechanical load when stresses arise in the structure over the entire circular profile of the busbars.

[0021] The task that the utility model is aimed at solving is the creation of a busbar compensator for a current conductor with an optimized geometry of the location of the fastening holes in the compensator disks.

[0022] The specified result is achieved by the fact that in a busbar compensator of a current-carrying conductor, containing two compensating disks, each of which contains two rows of circular holes connected by a package of conductive plates, each row contains seven holes, the centers of which are shifted between the rows and relative to the middle of the distance between the holes in the row, and the plate package is made of 32 plates.

[0023] The centers of the holes are offset relative to each other between adjacent rows - at an angle of at least 25°, and relative to the middle of the distance between the holes in one row - at an angle of at least 51°.

[0024] The choice of minimum values ​​of offset angles of 25° and 51° is due to experimental studies.

[0025] An offset angle of at least 25° between adjacent rows of holes is a critical parameter determining the relative position of current-carrying points and influencing the magnetic fields generated by currents flowing through welded joints. Studies have shown that at angles less than 25°, there is a sharp increase in the unevenness of current distribution between parallel branches, leading to localized overheating and accelerated aging of contact joints. Furthermore, at angles less than 25°, eddy current losses in the disk body increase significantly compared to the optimal conditions. In the preferred embodiment, the angle ranges from 25° to 45°. The upper limit of the range is selected based on changes in the load vector. When the angle exceeds 45°, the bridge begins to operate predominantly in bending, which, under dynamic loads, leads to the accumulation of microcracks in stress concentration zones near the edges of the holes.

[0026] An offset angle of the hole centers relative to the midpoint of the distance between the holes in a single row of less than 51° determines the width of the bridges between the holes and affects the shunt currents circulating through the disk body. At angles less than 51°, the bridge width becomes insufficient to ensure mechanical strength under cyclic thermal loads—stresses in the bridges exceed the permissible values ​​for copper alloys. Simultaneously, parasitic conductive loops arise in the disk body, reducing the efficiency of the flexible plate pack. In the preferred embodiment, the angle ranges from 51° to 75°. Exceeding 75° results in the bridges between the holes in the disk becoming thinner than the technologically permissible minimum, which makes the disk prone to failure, leads to an increase in the active resistance of the compensator, and, as a result, to its overheating under rated load currents.In addition, the nature of friction in the package changes, the sliding of the plates is replaced by their mutual biting due to an excessively sharp bending angle, a sudden movement of the plates occurs, leading to impact loads on the equipment terminals, and irreversible deformation of the plates.

[0027] The number of holes per row (7) is chosen to ensure uniform pressure on the plate pack across the entire width of the disk (at least 200 mm) and to create a sufficient total contact area to accommodate high currents. With fewer holes, the distance between the mounting points exceeds the permissible limit, resulting in loose contact at the outer plates of the pack and overheating.

[0028] Circular holes are chamfered or radiused to reduce stress concentration.

[0029] The number of plates in the package (32) and their dimensions (length not less than 236 mm, width not less than 200 mm) are selected based on typical current loads (up to 10 kA and above) and connection flexibility requirements. A width of 200 mm is standard for high-power busbars and ensures the required current-carrying capacity. A length of at least 236 mm ensures sufficient compensating capacity for thermal expansion and vibration. The length-to-width ratio (from 1.0 to 1.3) creates an optimal balance between flexibility and mechanical strength of the package.

[0030] These features are essential, since each of them is necessary to achieve the technical result, and their combination allows for a synergistic effect - the creation of a conductor with optimal technical characteristics.

[0031] The disks act as current-carrying flanges. They are used to supply current to a stack of flexible plates. The disks are connected to each other by a stack of 32 conductive plates. The plates are made of electrical copper with a thickness of 0.3 to 1.0 mm. In an optimal design, the ratio of the plate length to its width is between 1.0 and 1.3. The disks are made of copper or copper alloy.

[0032] The stack plates are connected to the disks by welding through circular holes. To reduce stress concentration around the holes, chamfers or radial transitions can be made. The stack plates are made of electrical copper with a thickness of 0.3 mm to 1.0 mm. The optimal plate length-to-width ratio is between 1.0 and 1.3. The stack plates are connected to the disks by welding through circular holes.

[0033] The specific hole geometry ensures uniform current distribution (so that the current spreads evenly across the disk and passes into the plates without overheating) and mechanical compensation (this hole arrangement allows the disks and plates to dampen vibrations and compensate for thermal expansion, without creating bending forces at the weld joint). The angles are calculated to maximize the number of plates in a stack for a given disk diameter and minimize stray magnetic fields (eddy currents) in the disk itself.

[0034] The design is not a standard busbar, but an engineering product designed for specific high-power electrical equipment where current load, flexibility and compensation of mechanical stress are important.

[0035] A review of patent documents and non-patent literature suggests that none of the prior art solutions simultaneously possesses all the distinctive features of the proposed compensator. No source specifies minimum angle values ​​of 25° and 51° in combination with the proposed minimum number of holes.

[0036] The essence of the utility model is explained by drawings:

[0037] Fig. 1 - general view of the busbar with the installed busbar compensator;

[0038] Fig. 2 - busbar compensator;

[0039] Fig. 3 - compensating disk.

[0040] The claimed utility model operates as follows.

[0041] The electric current is supplied to one of the compensating disks. The double-row arrangement of the mounting holes and their optimal angular orientation ensures uniform current distribution across the disk surface and transmission to each of the 32 plates in the stack.

[0042] The specified angular parameters minimize eddy currents in the disk body and prevent the formation of parasitic conductive loops between adjacent holes. As a result, the current flows through the flexible plates, ensuring maximum conductivity.

[0043] During thermal expansion of equipment components, vibrations, and mechanical displacements, the plate pack deforms, compensating for these effects and preventing the transfer of destructive forces to the disks and their mounting points. The optimal length-to-width ratio of the plates (1.0-1.3) ensures sufficient flexibility while maintaining mechanical strength.

[0044] During operation, due to the uniform current distribution and the optimal width of the bridges between the holes in the disks, no stress concentration zones arise, which prevents fatigue failure of the material under cyclic thermal loads.

[0045] During normal operation, the outer shell of the conductor and its internal structural elements are exposed to climatic factors and vibrations caused by natural electromagnetic influences during the flow of electric current. This causes thermal expansion of the material and mechanical stress within the structure.

[0046] In emergency conditions, external short-circuit currents lead to increased heat generation and abnormal mechanical vibrations of busbar structural elements. During seismic impacts, mechanical displacement of structural elements occurs at the site of seismic hazard. Mechanical impacts on the structure can lead to destruction of busbar elements.

[0047] The use of busbar compensator 1 ensures damping of mechanical movements of busbar nodes during temperature deformations of metal under the influence of external mechanical and climatic factors, as well as in emergency conditions such as seismic hazard and short-circuit current flowing through the busbar.

[0048] The busbar compensator dimensions are selected based on the possible radial and longitudinal movement of the busbars within ±50 mm under any impact. Two rows of seven plate compensators, consisting of 32 plates in the shell (2) and secured in two rows of openings (4), evenly distribute the mechanical load across the entire circumferential profile of the busbars when stresses arise in the structure due to thermal expansion, seismic impacts, and short-circuit currents.

[0049] The utility model is industrially applicable, as it can be manufactured using standard metalworking equipment. The design does not require any unique materials or technologies and can be implemented at any electrical engineering company that produces busbars.

[0050] Literature

[0051] 1. Ivanovsky D.A. Improvement of methods and technical means for diagnosing support insulators of complete shielded busbars. Cand. Sci. (Eng.) Dissertation, Novocherkassk, 2024.

[0052] 2. Moskvichev E.V., Eremin N.V. Calculation and experimental analysis of deformation of the compensator of temperature expansion of a busbar with cast insulation / / Journal of Siberian Federal University. Engineering & Technologies, 2018,11(2), 128-137.

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