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Title:
CIRCUIT ARRANGEMENT AND DEVICE FOR LOAD BALANCE OF PARALLEL CONDUCTORS OF AC SYSTEMS
Document Type and Number:
WIPO Patent Application WO/2017/175016
Kind Code:
A1
Abstract:
The object of the invention is a device and self-controlling current arrangement for balancing or sharing of conductor current of parallel conductors or plurality of phase conductor of an alternating current line. Each of the asymmetrically charged parallel conductor (1,2,3...4) has a single current transformer (21, 22,23...24), which have the same turns of secondary windings, which are correctly connected in series by their current direction. Because of the serial connection of the secondary circuit, the secondary currents (13,14,15... 16) will be the same, therefore their excitations will be also identical The properly selected core provides a linear magnetic coupling between the primary and secondary excitations, therefore the primary excitations are also necessarily identical. The primary currents (25,26,27...28) are identical if the primary turns are identical. Which are equal to the current of the asymmetrically charged conductors in the present invention.

Inventors:
GYÖRGY RÓBERT (HU)
Application Number:
PCT/HU2017/000025
Publication Date:
October 12, 2017
Filing Date:
April 03, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GYÖRGY RÓBERT (HU)
International Classes:
H02J3/26
Foreign References:
DE10256324A12004-06-17
CN104901322A2015-09-09
CN105375500A2016-03-02
US3855412A1974-12-17
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Claims:
Claims

1. ) self-controlling circuit arrangement for balancing or distributing asymmetrical current rates in the parallel conductor circuits of an alternating current system, in which at least two of each of the plurality of parallel conductors (1,2,3 ... 4), each have high-permeability rings (5,6,7 ... 8), on which there are winding threaded as secondary coils (9,10,11 ... 12), and these are connected, characterized in that the rings (5,6,7 ... 8) and the coils (9,10,11...12) placed on them form current transformers (21,22,23..24), and the coils of all the current transformers are connected directly in the order (K1-L2, K2-L3, K3- ... -L4, K4-L1) of their terminals, in such a way that the secondary currents (13,14,15 ... 16) flow in the same direction, and the pairs of wires (17,18 ... 19) connecting the secondary terminals of the current transformers are in close proximity, and there are magnetic shieldings (20) around each of the pairs,

2. ) A self-controlling circuit arrangement according to claim 1, characterized in that the current transformer (21,22,23 ... 24) ratios differ from each other.

3. ) A self-controlling circuit arrangement according to any one of claims 1-2 characterized in that at least one of the primary conductors (1,2,3 ... 4) passed through several times in the core (5,6,7 ... 8) of the current transformer (21,22,23 ... 24) to which it belongs.

4. ) A self-controlling circuit arrangement according to any one of claims 1 to 3, characterized in that the current transformers are split-core current transformers.

5.) A self-controlling circuit arrangement according to any one of claims 1 to 4,

characterized in that the interconnecting wire pairs (17,18...19) of secondary windings which lying in close proximity are twisted around one another.

6. ) A self-controlling circuit arrangement according to any one of claims 1 to 5, characterized in that the cross-section or length or material quality or the permissible load or impedance of the parallel primary conductors (1,2,3 ... 4) are different.

7. ) A self-controlling circuit arrangement according to any one of claims 1 to 6, characterized in that it is a single unit (Module 1) of a modular layout, and at least two of these single unit (Module 1, Module 2, Module 3 ... Module m) are arranged in series on the parallel primary conductors (1,2,3 ... 4) of the supply line, in any variations of the circuit arrangement described in claims 1 to 6.

8. ) A self-controlling circuit arrangement according to claim 7, characterized in that at each end of a feed line there are at least one modular unit (Module 1, Module 2, Module 3 ... Module m).

9. ) An apparatus according to any one of claims 1 to 8, characterized in that the self-controlling circuit arrangement is constructed structurally in a single unit.

10. ) An apparatus according to any one of claims 1 to 9, characterized in that the self-controlling circuit arrangement is structurally integrated with a cable head unit or busbar connection unit.

11. ) An apparatus according to any one of claims 1 to 10, characterized in that the self-controlling circuit arrangement is constructed by means of waterproof and dustproof current transformers or in a unitary waterproof and dustproof or submersible encapsulated apparatus (32).

12. ) An apparatus according to any one of claims 1 to 11, characterized in that connection possibilities (41, 42, 43 ... 44) are provided for split conductors (1,2,3 ... 4) or connection possibility (45) for undivided conductor (29).

13. An apparatus according to claim 12, characterized in that the connection possibilities (41, 42, 43 ... 44, 45) are dustproof or waterproof or submersible.

Description:
Circuit arrangement and device for load balance of parallel conductors of AC systems

The object of the invention is a device and self-controlling current arrangement for balancing or sharing of conductor current of parallel conductors or plurality of phase conductor of an alternating current line.

A common task is that high electrical load must be transported between two points in AC systems. In case of high current the phase conductor consists of several parallel-connected conductors, least two of the conductor can be connected in parallel to meet the energy demand of the transmission line. Above a certain cross-section only single core cables and conductors are manufactured. Due to environmental impacts parallel conductors of the same phase transport different currents, despite their same

cross-sections, geometry and load capacity. Typically, a nearby metal body or a high-current conductor has such an environmental impact like this. Due to the asymmetry some conductors are overloaded, while other conductors transported only a fraction of their nominal currents. Therefore the capacity of the power line is reduced to a fraction of the nominal value.

The asymmetry remains mostly hidden, it turns out light, if an individual examination of the parallel conductors or when the overloaded conductor burned down. This triggers further conductor fire and the disaster of the entire transmission line. As a solution additional parallel conductor are added, increasing their numbers as long as the current of the most loaded conductor has fallen below its nominal current. This is an expensive solution and associated with power interruption of the supplied facility or equipment.

The prior art provides a better solution for balancing the asymmetrical current of conductors by series line impedance balancing. This applies in DE10256324 (Al) - 2004-06-17 equipment using magnetic cores with a sufficiently high permeability is arranged around the asymmetrically loaded primary conductors by adjusting of the magnetic efficiency of the magnetic cores.

In patent claims 12 and 13 of DE10256324 (Al) 2004-06-17 the magnetic efficiency of the magnetic cores are influenced by the coil winding and the ends of the coil winding being connected to one another.

Referring to patent claims 8-11 these ends of the coil winding can be connected to one another by ohmic, inductive and / or capacitive components. The impedance of the connected components and the losses of the high magnetic permeability core are transformed to the asymmetrically loaded parallel conductors by the linear magnetic coupling. The series line impedances of the parallel conductors can be set to the same value by varying of the magnetic efficiency of the magnetic cores thereby eliminating asymmetries. The adjusting of the magnetic efficiency can be solved mechanically by the structure of the cores or electrically by winding.

The unbalanced currents of the parallel conductors hide a high risk to operational safety. On the one hand because the operators do not usually observ currents of the individual conductor by built-in measurement, they are checked only occasionally. On the other hand, artificially restored symmetry does not mean the termination of the asymmetry-causing effects. The operator often misses this fact. Therefore, the solution should be simple and failsafe. The symmetry maintenance equipment failure leads to an immediate return to the overload of a nominally loaded transmission line. The solution must follow the changes of the the asymmetry-causing effects caused by external and internal impacts. Typical of these effects that dynamically change over time, for example when starting up other high current conductor located close or when a large metal structure is established nearby. Therefore, the solution must be closed-loop control. DE10256324 (Al) - 2004-06-17 patents based on the same degree of limitation of the conductor currents. But the symmetry can be achieved by other means. The task requires that the balancing follows the dynamically variable degree of asymmetry. And it is preferred that the magnitude of effect is proportional to asymmetry.

Therefore, a closed-loop control-type solution is needed. The object of this invention is a self-controlling circuit arrangement that the most similar to a special case of the unspecified solution characterized by DE10256324 (Al) 2004-06-17 claim 13. The design of the self-controlling circuit arrangement, and the differences listed below exclude or limit the enforcement of the principle of operation of the prior art and provides principle employed by the self-controlling circuit arrangement.

In the prior art the magnetic efficiency of the magnetic cores are influenced by the coil winding and the ends of the coil winding being connected to one another. It does not define the method for connecting, which can be serial, parallel, mixed, direct, through elements, parallel with elements or countercurrent. This leaves open the possibility that it is not necessary for all winding terminal to be in connection.

Due to the enforcement of the principle of magnetic efficiency control, prior art requires such material choice and sizing of elements that prevents the enforcement of the principle of self-controlling circuit arrangement forming the subject of the present invention. And vice versa. The prior art increases the value of the transformed series line impedance by adjusting the magnetic efficiency. This means that the primary concern when selecting magnetic core material is the a high permeability, and more preferably, at least the resulting loss is not detrimental. Therefore, the primary concern when specifying of the the winding is to tolerate the secondary current flowing through winding under all operating conditions, but does not intend to reduce the secondary impedance. For the same reason does not intend to optimize the geometry of the connections and terminals achieving the lowest impedance is available. Indeed, the aim is precisely that to increase the impedance according to the asymmetry in order to limit the primary current.

The self-controlling circuit arrangement forming the subject of the present invention offers solutions to similar but more complex problem. The more complex task is the current balancing or load sharing of the asymmetrically loaded parallel conductors and the solution is the circuit arrangement that implements closed-loop self-controlling.

The self-controlling circuit arrangement according to present invention requires a direct serial connection of devices. It requires all windings to be connected in series by the same direction of the primary currents generated. It requires minimization of the impedance of the serial arrangement. It prohibits the use of the interstitial, parallel and any other way of connection of active or passive circuit elements with the windings of the circuit arrangement. As the object of the present invention seeks to minimize the value of serial impedances transformed to the primary side to reinforce the principle of induced balancing currents, as a side effect weakens the effect of the prior art. The arrangement according to the present invention solves the above-described task by achieving a stable self-controlling process. The feedback and the

symmetry-restoring effect are caused by the special circuit and geometry layout and the material properties of the built-in devices and components and their specification. Operational safety is provided by a simple construction that supports the principle of operation.

The structure and operation of the arrangement according to the invention can be illustrated in the simplest way as follows. Each of the asymmetrically charged parallel conductor has a single current transformer, which have the same turns of secondary windings, which are correctly connected in series by their current direction. Because of the serial connection of the secondary circuit, the secondary currents will be the same, therefore their excitations will be also identical.

The properly selected core provides a linear magnetic coupling between the primary and secondary excitations, therefore the primary excitations are also necessarily identical. The primary currents are identical if the primary turns are identical. Which are equal to the current of the asymmetrically charged conductors in the present invention. The invention is illustrated by the following figures,

FIG. 1 is the most common implementation of the self-controlling load balancer circuit arrangement of parallel conductors

FIG. 2 is the secondary circuit of the self-controlling load balancer circuit arrangement,

FIG. 3 is a system modularity of the self-controlling load balancer circuit arrangement,

FIG. 4a is a load balancer cable head unit or busbar connection unit, which includes the circuit arrangement of the present invention in front view,

FIG. 4b is a load balancer cable head unit or busbar connection unit, which includes the circuit arrangement of the present invention, in top view,

FIG. 5a is a load balancer apparatus, which includes the circuit arrangement of the present invention in waterproof and dustproof design, in front view,

FIG. 5b is a load balancer apparatus, which includes the circuit arrangement of the present invention in waterproof and dustproof design, in top view,

The construction and operation of the solution according to the invention can be described in detail in the following way. A self-controlling circuit arrangement for balancing or distributing asymmetrical current rates in the parallel conductor circuits of an alternating current system, in which at least two of each of the plurality of parallel conductors 1,2,3 ... 4, each have high-permeability rings 5,6,7 ... 8, on which there are winding threaded as secondary coils 9,10,11 ... 12, and these are connected, characterized in that it is the rings and the coils placed on them form current transformers 21,22,23..24, and the coils of all the current transformers are connected directly in the order K1-L2, K2-L3, K3- ... -L4, K4-L1 of their terminals, in such a way that the secondary currents 13,14,15 ... 16 flow in the same direction, and the pairs of wires 17,18 ... 19 connecting the secondary terminals of the current transformers are in close proximity, and there are magnetic shieldings around each of the pairs. The impedances of the secondary windings 9,10,11 ··· 12 need to be minimized by selecting at least five times but practically ten times the size of the cross section which is appropriate for nominal value of the current flowing through them. It is necessary to minimize the impedance of the wires and connections of the coils, including the ohmic contact resistances and the inductive and capacitive impedances due to the length of wires and wiring geometry. Therefore, the angle of the secondary wiring of the current transformers shown in FIG. 2 with the primary conductors 1,2,3 ... 4 is perpendicular. The connecting wires are straight, running between two windings on a straight path and in the same plane, and pairs of connecting cables 17,18 ... 19 cover the smallest possible area. It is preferred that this plane is parallel to the principal direction of the primary conductors 1,2,3 ... 4. The material quality and cross-section of wires and connections are aimed at achieving low impedances.

The figures and descriptions give a general illustration for the arrangement of two or more parallel conductors. Naturally, the only reason for selecting four parallel conductors or an m number of modules was to allow better understanding. The self-controlling load distribution circuit arrangement is a solution for every two or more parallel conductors.

The basis of operation is that due to the serial connection of the secondary coils 9,10,11 ... 12, the direction and magnitude of the secondary currents 13,14,15 ... 16 are vectors of the same. Therefore, due to the same number of turns, the secondary excitations of the current transformers are the same as the following formula: l * N=l b , *N=I C , *N= ...=l n ,*N.

N the number of threads of the secondary coils, l a ,, l b ,, l c ,, l n , represent the secondary currents 13,14,15 ...16.

For transformers it is generally true that their primary and secondary excitations are the same.

I a , *N= l a *1 l 3 , is the secondary current 13 of current transformers of primary conductor 1, N is the number of threads of secondary windings, l a is the primary current 25 of primary conductor 1. This equality is true for all current transformers on all conductors.

In the case of the appropriate magnetic scaling of cores 5,6,7 ... 8, all of the primary excitations of the transformers are also the same.

I * l=l *l=l *1= ...=l *1 l a , l b ,l c ... I n are the primary currents 25,26,27...28, The turn of primary winding is equal to one, because the primary coil is the conductor passing through the core. Primary circuits 1,2,3...4 are connected at both ends, because of the above they must have the same currents l a =l b =l c = ·■■=!„. I is the total current of the undivided conductor and it is equal to the sum of the primary currents 25,26,27 ... 28, with formula l = l a =l b =l c =— =!„■ This provides a self-controlling mechanism for the present invention.

The recognition is that the primary conductors galva nically coupled at both ends form a frame with high-conductivity by means of parallel coupling. In this conductive frame, the secondary excitation of the current transformers can easily provide the same primary currents, due to their serial coupling and due to the low impedances of the secondary circuits and the low loss cores. It is easy to achieve this against the different serial impedances of the primary conductors, and the varying degrees of external influences.

Of course, the magnitude and direction of the total current l of the undivided conductor 29 of FIG. 1 is determined by the LOAD not by the mechanism of self-controlling. The object of the invention through self-controlling mechanism always generates balancing currents with appropriate direction and magnitude which reduce the asymmetry. The balancing current is proportional to the size of the asymmetry.

The inventive step is that current transformers used in the industry are essentially designed for measurement and actuation. Because of the above , these transformers have been designed for long-term operation, and are safe, and work as a key feature with little loss. The arrangement of these elements according to the invention and the way of choice differs from the usual practice, their unusual use, and special design of the secondary circuit altogether allow to restore symmetry in the parallel conductor currents.

Current transformers for measurement and actuation for this solution have to be chosen based on a different criteria. Selection is not based on the value of the maximum primary current in the conductor, but is aimed at achieving the lowest transformed impedance available. For this purpose, the practically ten times over-dimensioning of the nominal primary current of the current transformer, the choice of the ratio, nominal secondary current and nominal power is different from the usual. The design of the serial arrangement of the secondary circuit also aims to minimize the impedances. In addition, the issue of operational safety, in terms of establishment of connections and terminals, are also higher than the standard level, due to the reasons listed in the section on the prior art and the tasks to be solved. A good example for this is that it is not acceptable to use terminal block as terminal of these current transformer or anywhere in the secondary circuit as a connecting solution, as industry routinely applies it. In addition to the advantages of the self-controlling circuit arrangement of the present invention, it also has disadvantages compared to prior art. This is precisely because of the low value of the transformed impedances, it does not increase the series line impedances of the supply line, therefore it does not play a role in limiting short-circuit currents.

The present invention is carried out according to the claim 1, further details are given in the dependent claims 2-13.

One preferred solution can be used when the absolute value of the deviation from the symmetric state is significant, typically reaching 40%. In FIG. 3, the circuit arrangement described above is the first unit Module 1 of a modular arrangement. Repeating the unit in any number m, modular assembly built from module units Modul 1, Modul 2, Modul 3 ... Modul m can be used to increase symmetry.

Another preferred solution can be used in cases where asymmetry is typically greater than 40%. It is worthwhile to find out within what limits it moves over time. Depending on this test, it is possible to design a self-controlling circuit arrangement when the current transformer ratios are different. This solution can also be used as a second module of the modular arrangement, where the first module of the modular arrangement is constructed of current transformers of the same ratio. In this case, the selection of current transformers demands additional requirements because of leakage flux.

In another solution a primary winding is carried out using primary conductor passed through several times in the core of the current transformer. In order to achieve the desired symmetry, different number of turns can be selected for each primary windings. If the circuit arrangement of the present invention consists of these current transformers, then this is an additional tool for choosing different ratio.

The use of different current transformers and the primary winding formed by several turns of the primary conductor make it possible that the parallel conductors can differ in cross-section, length and quality of material, or may differ in impedance for any reason. In this solution, it can be imagined that a

sub-dimensioned feed line is expanded by several different cross-sectional parallel conductors.

The ratio of current transformers can be adjusted in proportion to their permissible currents. As a result, proportions of self-controlling of the load distribution can also be adjusted. The differences in the permissible load capacity of individual conductors can also be due to their different environmental conditions. For example by being outdoors, indoors or by what kind of material or technology they have made, they are single or bundling with other conductors and in which ambient temperature they pass. The next advantageous solution can be applied to a critical facility or equipment whose feed line can never be interrupted. Typically, these are data centers and hospitals or subsistence equipments. It provides solution without interruption in case of asymmetric load of parallel phase-conductors, when the self-controlling circuit arrangement of the present invention is made of split-core current transformers.

Because of the modularity principle, modules can be placed on both ends of the supply line. Thanks to this, a symmetrical modular layout can be created for limiting or filtering disturbances on the supply lines.

Preferably, the self-controlling circuit arrangement of the present invention is structurally integrated with a cable head unit or busbar connection unit shown in FIG. 4. Here, ideal conditions exist for forming the secondary circuit 17, 18 ... 19 and shielding 20, due to primary conductors lying close to each other, due to the small distances and geometry of the arrangement. There are formed easy-to-install 41, 42, 43 ... 44, 45 connectivity options for 1,2,3 ... 4 parallel conductors and for 29 undivided conductor.

Another preferred solution is shown in FIG. 5, where a self-controlling circuit arrangement of the present invention is utilized by using waterproof and dustproof current transformers, or it is enclosed in a unit (32) of waterproof and dustproof equipment. And this apparatus is used for the split phase-conductors of an overhead line, or parallel conductors of an aerial bundled cable or parallel conductors of parallels of ground cables. It is also advantageous to have connection possibilities for both the inputs and the outputs (41, 42, 43 ... 44, 45) for the undivided and the split phase-conductors, which provide the possibility of waterproof and dustproof or submersible mounting. The weather-resistant and the easy to install design make outdoor, underground, underwater use possible. The united arrangement shown in Figures 4a, 4b can be applied at the end of the supply lines, the solution shown in Figures 5a and 5b can be used in intermediate locations. With the fixing point 31, it is possible to arrange regular assembly.

The secondary circuit of the self-controlling arrangement of the present invention can preferably be formed if the interconnecting wire pairs of secondary windings which in close proximity are twisted around one another. The twisted wire pairs complement the effect of magnetic shielding. List of reference marks

1 First parallel primary conductor

2 Second parallel primary conductor

3 Third parallel primary conductor

4 The last primary conductor of at least two of each of the plurality of parallel conductors (Hereinafter referred to as "The last primary conductor")

5 The core of the current transformer of the first parallel primary conductor

6 The core of the current transformer of the second parallel primary conductor

7 The core of the current transformer of the third parallel primary conductor

8 The core of the current transformer of the last parallel primary conductor

9 The secondary coil of the current transformer of the first parallel primary conductor

10 The secondary coil of the current transformer of the second parallel primary conductor

11 The secondary coil of the current transformer of the third parallel primary conductor

12 The secondary coil of the current transformer of the last parallel primary conductor

13 The secondary current of the current transformer of the first parallel primary conductor

14 The secondary current of the current transformer of the second parallel primary conductor

15 The secondary current of the current transformer of the third parallel primary conductor

16 The secondary current of the current transformer of the last parallel primary conductor

17 One of the pairs of wires of the secondary wiring

18 The other pairs of wires of the secondary wiring

19 The third pairs of wires of the secondary wiring

20 Magnetic shielding of secondary wiring

21 The current transformer of the first parallel primary conductor

22 The current transformer of the second parallel primary conductor

23 The current transformer of the third parallel primary conductor

24 The current transformer of the last parallel primary conductor

25 The current of the first parallel primary conductor

26 The current of the second parallel primary conductor

27 The current of the third parallel primary conductor

28 The current of the last parallel primary conductor

29 The undivided primary conductor

31 Possibility of fixing of powder- and water-proof equipment

32 Powder- and water-proof housing

41 The connection possibility of the first parallel primary conductor

42 The connection possibility of the second parallel primary conductor

43 The connection possibility of the third parallel primary conductor

44 The connection possibility of the last parallel primary conductor

45 The connection possibility of the undivided primary conductor

LI The secondary terminal L of the current transformer of the first parallel primary conductor

Kl The secondary terminal K of the current transformer of the first parallel primary conductor

L2 The secondary terminal L of the current transformer of the second parallel primary conductor

K2 The secondary terminal K of the current transformer of the second parallel primary conductor

L3 The secondary terminal L of the current transformer of the third parallel primary conductor

K3 The secondary terminal K of the current transformer of the third parallel primary conductor L4 The secondary terminal L of the current transformer of the last parallel primary conductor K4 The secondary terminal K of the current transformer of the last parallel primary conductor l £ The current of undivided primary conductor

LOAD The load

Modul 1 The first unit of the modular layout

Modul 2 The second unit of the modular layout

Modul 3 The third unit of the modular layout

Modul m The last unit of the modular layout