EP3499527B1

EP3499527B1 - Barrier support for supporting an electrically insulating barrier between windings of a dry insulated electric transformer

Info

Publication number: EP3499527B1
Application number: EP18211487.6A
Authority: EP
Inventors: Andrea Giorgio Colombo; Simone Zara
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-12-14
Filing date: 2018-12-11
Publication date: 2020-10-28
Anticipated expiration: 2038-12-11
Also published as: ES2847959T3; EP3499527A1

Description

BACKGROUND

The present invention relates to the field of resin-insulated dry electric transformers. In particular, the present invention relates to an electrical transformer of the aforesaid type with an electrically insulating barrier interposed between the low voltage winding and the medium voltage winding. More particularly, the present invention relates to a barrier support configured to support an insulating barrier between a low voltage winding and a medium voltage winding in a medium to low voltage electrical transformer.

STATE OF THE ART

The electric network provides users with electricity in the form of an alternating voltage, generally called "low voltage". This low voltage typically has an amplitude of the order of some hundred volts. However, in the case of large users such as factories, shopping center or the like, electricity can be supplied in the form of "medium voltage", whose amplitude is typically of the order of tens of thousands Volt. In this case, the user uses an electric transformer to convert the medium voltage coming from the electric network into low voltage.
As is known, a transformer is an electric machine suitable for transforming an input voltage (and the input current associated thereto) into an output voltage (and into an output current associated thereto).
Typically, a transformer comprises a primary winding and a secondary winding. The primary and secondary windings are electrically insulated from each other and are coupled by a magnetic circuit; for example, the primary and secondary windings can be wound concentrically on a magnetic core.
An alternating input voltage applied to the ends of the primary winding induces a magnetic flux in the magnetic core. In turn, this magnetic flux induces an alternating output voltage at the ends of the secondary winding. As is well known, the ratio between the amplitude of the output voltage and the amplitude of the input voltage is equal to the ratio between the number of turns of the secondary winding and the number of turns of the primary winding.
Since the electrical power in generally supplied as a three-phase voltage, medium to low voltage transformers typically comprise three elements, commonly referred to as "columns". Each column comprises a magnetic core, a primary winding and a secondary winding, to transform a phase of the medium input voltage into a respective phase of the low output voltage.
Typically, the magnetic cores are formed by a plurality of sheets made of magnetic material (for example, oriented grain silicon) coated with an insulating material, packed and tightened against each other. The magnetic cores of the columns are not independent of each other but are branches of a single magnetic circuit with three branches. The cores of the columns are connected to each other at both ends by means of rectilinear yokes, also formed by the above mentioned sheets.
Moreover, typically, the magnetic core is pressed at the yokes by means of a pair of horizontal elements (made, for example, in the form of steel sections), commonly referred to as "yoke clamps", connected together by crossbars. Pressing devices configured to press the transformer columns, in particular the medium voltage winding contained in the casing, are then attached to the yoke clamps.
In order to fix a known pressing device to a yoke clamp typically a screw is generally used coupled with two nuts, in turn coupled with respective counter-nuts to prevent loosening. In addition, typically, washers are used to improve the locking of the nuts. The pressure exerted by the device on the medium voltage winding of the transformer is regulated by screwing the screw and the nuts.
From the Italian patent 0001427304 (application No. 102014902311923 of 25.11.2014) in the name of the same Applicants, a pressing device is known for a resin-insulated dry electric transformer, said pressing device being configured to block a winding (of medium and/or low voltage) with respect to a yoke clamp.
US 6160464 A discloses a resin winding for a high voltage transformer.
US 2013/127582 A1 describes a dry transformer having at least two windings.
CN 205 621 582 U discloses a dry type distribution transformer.
KR 2011 0031682 discloses a spacer of a mold transformer.

SUMMARY OF THE INVENTION

The Applicants have noted that on some occasions it is desirable to provide greater insulation between the low voltage winding and the medium voltage winding in a transformer.
According to the Applicants, such insulation can be provided by interposing an electrically insulating barrier between the low voltage winding and the medium voltage winding in a resin-insulated dry transformer.
This electrically insulated barrier may be in the form of a plate of an electrically insulated material curved so as to form a tube with a circular section with a diameter and a thickness such as to be interposed between the two windings.
The main objective of the insulating barrier is to be able to reduce the distance between primary winding and secondary winding. Thanks to this system, dimensions and cost can be reduced, leaving the transformer mechanical and electrical features unaltered.
The Applicants have also set the objective of providing a support for supporting, at least at the bottom but preferably also at the top, the barrier of electrically insulating material in a simple, practical, robust manner.
The Applicants have also set the objective of providing a support for the barrier that could be associated with the existing components of a resin insulated dry transformer.
In general terms, the present invention provides an organ configured to support an insulating barrier between the two windings of a resin insulated dry transformer. Advantageously, the organ according to the invention is configured so as to be hooked and supported by a pressing device of the type known from Italian patent no. 0001427304 , and/or from its centering member and/or a spacer.
The present invention provides a barrier support configured to support an electrically insulating barrier between a first winding and a second winding of an resin-insulated dry electric transformer, the barrier support comprising a vertical body and a horizontal leg connected together substantially at 90°, wherein said horizontal leg is configured so as to couple in a removable way to a pressing device or to a part thereof.
According to an aspect of the invention, a system comprising a pressing device and a barrier support is described.
The pressing device of the system is configured to be arranged between a column of a resin insulated dry electric transformer and a yoke clamp for an insulated dry electric transformer. The pressing device is configured to lock a winding with respect to a yoke clamp, said pressing device comprising a first body and a second body, wherein the first body and the second body are configured to translate away with respect to each other in a guided manner to block the column with respect to the yoke clamp.
The barrier support of the system is configured to support, at the top and/or at the bottom, a barrier, in the form of a plate of electrically insulating material, between a first winding and a second winding of said electrical transformer, the barrier support comprising a vertical body and a horizontal leg connected together substantially at 90°, wherein said horizontal leg is configured so as to be coupled in a removable way to the pressing device, wherein said horizontal leg comprises two half-legs shaped to form a circle arc opening, and wherein said vertical body comprises a pair of substantially parallel walls separated by a slot, said walls forming a housing for said barrier.
Preferably, the half legs are configured to open one to the other during the phase in which the barrier support is coupled to the first or second body of the pressing device.
The circle arc extends, for example, to an angle greater than 185° and less than 200°.
Preferably, the horizontal leg comprises a root part with a cut open toward the circle arc opening.
In embodiments, the vertical body further comprises an additional wall substantially parallel to said pair of walls to form a further slot which defines a further housing for a further barrier in the form of a plate of electrically insulating material.
Preferably, the substantially parallel walls are curved.
Advantageously, the barrier support is made of thermoplastic resin with self-extinguishing characteristics.
In embodiments, the first body comprises a substantially cylindrical body with an upper base, a lower base and a side surface and wherein the second body is mushroom-shaped with a cap and a shank; the pressing device further comprises a first threaded member and a second threaded member configured to cooperate with each other; wherein said second threaded member is connected to said second body in such a way that their mutual rotation is prevented; said first threaded member engages said first body so that a rotation thereof in a first direction causes the two bodies to move away and a rotation thereof in a second direction causes the two bodies to move closer together; and the shank of said second body has a non-circular cross-section and said first body comprises a corresponding main hole with a cross-section complementary to that of the shank.
The shank can have a hexagonal cross-section, square, triangular, pentagonal, octagonal, circular with one or more facets, oval or elliptical. The main hole of the first body has, correspondingly, a hexagonal, square, triangular, pentagonal, octagonal, circular section with one or more facets, oval or elliptical.
According to another aspect, the present invention relates to a resin-insulated dry electric transformer comprising: windings blocked with respect to yoke clamps; a plurality of systems, with each system comprising a pressing device and a barrier support; and electrically insulating barriers, wherein each electrically insulating barrier is in the form of a plate of electrically insulating material and wherein at least one of said systems is a system of the aforementioned type.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will become fully clear in the light of the following detailed description, given as a non-limiting example, to be read with reference to the accompanying drawings wherein:

Figure 1 is a schematic sectional view of a pressing device in its closed configuration;
Figure 2 is a schematic sectional view of the device of Figure 1 in its open configuration;
Figure 3 is an axonometric and sectional view of the device of Figure 1 in its open configuration;
Figures 4a-4d are four views of the lower body of the device of Figure 1;
Figures 5a-5d are four views of the upper body of the device of Figure 1;
Figure 6 is a schematic view showing a plurality of pressing devices in a resin-insulated dry electric transformer;
Figures 7 and 8 are two axonometric views of a barrier support according to a first embodiment of the present invention;
Figures 9.1 and 9.2 are two plan views of the barrier support of Figures 7 and 8;
Figure 10 is an axonometric view of the barrier support of the first embodiment with a barrier portion;
Figure 11 is an axonometric view of a barrier support according to a second embodiment;
Figure 12 is an axonometric view of the barrier support of Figure 11 with two barrier portions;
Figure 13 is an axonometric view of a barrier support according to a third embodiment;
Figure 14 is an axonometric view of the barrier support of Figure 13 with three barrier portions;
Figure 15 is an axonometric view of the barrier support according to the first embodiment mounted to a pressing device; and
Figure 16 is an exploded view of the components of Figure 15.

DETAILED DESCRIPTION

The Figures, or some of them, may not be in scale.
In order to illustrate the barrier support according to the invention, a detailed description of a pressing device 1 (also simply referred "device" hereinafter) for an electrical transformer will be provided herein below with reference to Figures 1-6.
With reference initially to Figures 1, 2 and 3, the device 1 comprises a lower body 2 and an upper body 3 cooperating with each other to move closer or to move away. The device 1 further comprises a threaded member, for example a screw 4 and nut 5 assembly, for translating reciprocally the upper body 3 with respect to the lower body 2.
The lower body 2 (Figures 4a-d) comprises a substantially cylindrical body with an upper base 21, a lower base 22 and a side surface 23. The side surface 23 is preferably shaped with one or more small diameter openings 231. Preferably the openings 231 are curved and do not form corners.
Preferably, the lower body 2 comprises a main blind hole 24 which develops for a portion of the longitudinal axis and which is open towards the upper base 21. Preferably, the main blind hole 24 has a hexagonal section as shown in Figures 4b and 4c.
Preferably, a pin 25 extends from the bottom of the main blind hole 24 towards the upper open base 21. The pin 25 preferably has a longitudinal axis that coincides with the axis 2-2 of the lower body 2. Preferably, the pin 25 has a hexagonal cross section. Between the lateral surface of the pin 25 and the side surface of the main blind hole 24 there is a free space 241 such that a hexagonal crown section guide is created for the lower body shank 3 which will be described below. The pin 25 may be solid or it may be lightened and formed by spoke walls 251 converging towards the longitudinal axis of the pin.
The lower base 22 of the lower body 2 is suitably shaped to cooperate with an adapter. For example, as shown in the various Figures, a secondary blind hole 26 with hexagonal section is provided with a central projection 27 having a hexagonal section, separated from the side surface of the secondary blind hole 26 so as to form a free space 261 with a hexagonal crown section .
The lower body 2 is preferably made of thermoplastic resin or similar material. Suitable materials are, for example, Nylon PA 6/66 (possibly filled with fibers or glass spheres in a variable percentage, for example between 30 and 60%), PBT (Polybutylene terephthalate), PPA, PPS or the like. In particular, it is preferable to use one of the aforesaid materials with self-extinguishing characteristics. Advantageously it can be made by molding.
According to embodiments, the lower body 2 has a height (measured in the longitudinal direction) between about 50 and 100 mm. For example it can be about 50-60 mm.
According to embodiments, the main blind hole 24 has a depth of about 40 mm.
According to embodiments, between the lateral surface of the pin 25 and the side surface of the main blind hole 24 there is a crown of a few millimeters (4-5 mm).
According to embodiments, the pin extends longitudinally within the main blind hole for a percentage between 50% and 75% of the depth of the main blind hole.
Preferably, the axis of the main blind hole 24, of the secondary blind hole 26, of the pin 25 and of the central boss 27 coincides.
The upper body 3 (Figures 5a-d) is preferably mushroom-shaped with a cap 31 and a shank 32. The cap 31 is preferably a thick circular-shaped disk, with a central through hole 311.
The shank 32 of the upper body 3 is preferably shaped with a hollow cylinder and communicates with the through hole 311 of the cap 31. Preferably, near the cap 31 a seat 322 is provided for a nut or another similar member.
Preferably, the shank 32 of the upper body 3 has a hexagonal section with a size slightly smaller than that of the main blind hole 24 of the lower body 2 so that the shank 32 can fit into it and the two bodies 2, 3 translate one respect to the other, substantially without mutual rotation. Preferably, the wall thickness of the shank 32 is such that it can enter and slide into the free space 241 with a hexagonal crown section, which acts as a guide for it.
The upper body 3 is preferably made of thermoplastic resin or the like material. Advantageously, it can be made by molding.
According to embodiments, the upper body 3 has a height (measured in the longitudinal direction) between about 50 mm and about 100 mm. For example it can be about 60 mm. The shank 32 may have a height of about 45-55 mm or in any case corresponding to the depth of the main blind hole 24 of the lower body 2. In this way, as will be better explained herein below and as shown in Figure 1, the shank 32 may be completely recessed in the main blind hole 24 and the cap 31 may rest against the upper surface 21 of the lower body 2.
The cap 31 of the upper body 3 may be of a diameter substantially equal to the diameter of the upper surface 21 of the lower body 2.
The upper body 3 is preferably made of thermoplastic resin or the like material. Suitable materials are, for example, Nylon PA 6/66 (possibly filled with fibers or glass spheres in a variable percentage, for example between 30 and 60%), PBT (Polybutylene terephthalate), PPA, PPS or the like. In particular, it is preferable to use one of the aforesaid materials with self-extinguishing characteristics.
Preferably, as shown in Figures 1, 2 and 3, the pressing device 1 further comprises a screw 4 and a nut 5. The nut 5 is preferably mounted recessed in the seat 322 of the upper body 3. The screw 4 protrudes above the cap 31 of the upper body 3. The screw 4 may have, for example, a hexagonal head. The lower end 41 of the shank of the screw 4, when the device 1 is assembled, rests against the upper end 251 of the pin 25, as shown in Figures 1, 2 and 3.
Although a specific embodiment has been described and illustrated in which the upper body has a hexagonal shank 32 (and the main blind hole 24 and/or the pin 25 has/have a corresponding complementary section), other shapes are possible which prevent a reciprocal rotation between the upper body and the lower body. For example, the shank can have a square, triangular, pentagonal, octagonal, circular section with one or more facets, oval, elliptical, ....
The pressing device 1 can be used between the columns C of a resin insulated dry electric transformer T and the yoke clamps P (Fig. 6). Typically, at least eight pressing devices (four upper and four lower) are used for each column. Figure 6 schematically shows a side of a transformer T and then shows half of the commonly used pressing devices 1.
With reference now to Figures 7, 8, 9 and 10, a first embodiment of the barrier support 101 according to the present invention will now be described. The barrier support 100 has a generally L-shape with a vertical body 110 and a horizontal leg 120. The terms "horizontal" and "vertical" refer to the member in use.
The vertical body 110 and the horizontal leg 120 are preferably at about 90° with respect to each other.
The connection area between the vertical body 110 and the horizontal leg 120 is preferably reinforced by a roughly triangular stiffener 130. Preferably, two triangular stiffeners 130 are provided.
According to the first embodiment, the vertical body 110 is preferably formed by two substantially parallel walls (also called "blades") 111, 112 which define a slot 113 open at the top and at the sides but closed at the bottom as indicated by the number 114 in Figure 7. The two parallel walls 111, 112, closed at the bottom, define a housing for a plate of electrically insulating material which forms the barrier B (visible in Figure 10) between the low voltage winding and the medium voltage winding.
Advantageously, the two blades 111, 112 are curved so that the plate of insulating material B which forms the electrically insulating barrier assumes a circular configuration (Figure 10) as the space between the two windings.
The horizontal leg 120 comprises a common root 121 and two half- legs 122, 123, more visible in Figures 9. The two half- legs 122, 123 are separated by a cut 124 which substantially departs from the root 121 and is open in the opposite direction.
The two half- legs 122, 123 define a circular opening 125. Preferably, the circular opening 125 has a greater extension than a semicircumference. Preferably, the opening angle of the opening 125 corresponds to an angle of at least 185° but more preferably at least 190°. Preferably, the opening angle of the opening 125 corresponds to an angle lower than about 200°.
The barrier support 101 is preferably made of thermoplastic resin or the like material. Suitable materials are, for example, Nylon PA 6/66 (possibly filled with fibers or glass spheres in a variable percentage, for example between 30 and 60%), PBT (Polybutylene terephthalate), PPA, PPS or the like. In particular, it is preferable to use one of the aforesaid materials with self-extinguishing characteristics.
The barrier support 100 is configured to be snap-locked in a removable manner to the pressing device 1 or to a spacer 7. In particular, the two half- legs 122 and 123 have a certain degree of elasticity and are able to open to accommodate the part with reduced diameter (openings 231) of the lateral surface 23 of the lower body 2. The elasticity of the material causes the semi-legs 122 and 123 to close again when the reduced-diameter part is embraced by the half-legs. In this way, the barrier support 101 is snapped to the pressing device 1 or to a uplift or centering support thereof. The barrier support 101 according to the first embodiment is shown coupled to a uplift of a pressing device in Figure 15 or in the exploded view of Figure 16.
The barrier support 101 can be used indifferently to support a single plate barrier B both at the bottom and at the top. It is sufficient to turn the blades up or down.
The thickness of the horizontal leg 120 of the barrier support 101 is such as to allow the horizontal leg to be inserted into the opening 231 of the lower body of the pressing device and to remain held at the top and at the bottom.
Among the advantages of the present invention there is also the fact that the barrier support 101 thus configured can be coupled to the pressing device 1 in a plurality of positions. Therefore, once the transformer is mounted and the windings are locked with the pressing devices 1, the barrier plate can be inserted and the barrier supports 101 can be blocked to support the barrier itself.
Figures 11 and 12 show a second embodiment of the barrier support 102 of the present invention. The barrier support 102 is very similar to the barrier support 101 and therefore a detailed description will not be repeated. The difference mainly lies in the fact that the vertical body 110 comprises three blades 111, 112, 115 which define two slots 113 open at the top and at the sides but closed at the bottom as indicated by the number 114.
As shown in Figure 12, in each of the slots 113 a barrier B can be inserted, typically comprising a plate of an electrically insulating material. In this way, the barrier comprises two concentric plates for even greater protection against electric shocks, parasitic currents or the like.
Figures 13 and 14 show a third embodiment of the barrier support 103 of the present invention. The barrier support 103 is very similar to the barrier support 101 and therefore a detailed description will not be repeated. The difference mainly lies in the fact that the vertical body 110 comprises four blades 111, 112, 115 and 116 which define two slots 113 open at the top and at the sides but closed at the bottom as indicated by the number 114.
As shown in Figure 12, in each of the slots 113 a barrier B can be inserted, typically comprising a plate of an electrically insulating material. In this way, the barrier comprises three concentric plates B for even greater protection against electric shocks, parasitic currents or the like.
The barrier is an electrically insulating material such as fiberglass or any thermoplastic material.

Claims

A system comprising
a pressing device (1) configured to be arranged between a column (C) of a resin insulated dry electric transformer (T) and a yoke clamp (P), said pressing device (1) comprising a first body (2) and a second body (3), wherein the first body (2) and the second body (3) are configured to translate away with respect to each other in a guided manner to block the column (C) with respect to the yoke clamp (P),
a barrier support (101, 102, 103) configured to support, at the top and/or at the bottom, a barrier (B), in the form of a plate of electrically insulating material, between a first winding and a second winding of said electrical transformer (T), the barrier support (101, 102, 103) comprising a vertical body (110) and a horizontal leg (120) connected to each other substantially at 90°, wherein said horizontal leg (120) is configured so as to be coupled removably to the pressing device (1), wherein said horizontal leg (120) comprises two half-legs (122, 123) shaped so as to form a circular arc opening (125), and wherein said vertical body (110) comprises a pair of substantially parallel walls (111, 112) separated by a slit (113), said walls (111, 112) forming a housing for said barrier (B).
The system of claim 1, wherein said half-legs (122, 123) are configured to open relative to one another in the phase in which said barrier support (101, 102, 103) is coupled to the first or to the second body of the pressing device (1).
The system of claim 1 or 2, wherein said arc of circle extends for an angle greater than 185° and less than 200°.
The system of any of claims 1-3, wherein said horizontal leg (120) comprises a root part (121) with a cut (124) open towards said circular arc opening (125).
The system of claim 1, wherein said vertical body (110) further comprises a further wall (115, 116) substantially parallel to said pair of walls (111, 112) to form a further slit (113) which defines a further housing for a further barrier (B), in the form of a plate of electrically insulating material.
The system of any of the previous claims, wherein said substantially parallel walls (111, 112, 115, 116) are curved.
The system of any of the previous claims, wherein said barrier support (101, 102, 103) is made of thermoplastic resin with self-extinguishing characteristics.
The system of any of the previous claims, wherein the first body (2) comprises a substantially cylindrical body with an upper base (21), a lower base (22) and a side surface (23) and wherein the second body (3) is shaped like a mushroom with a cap (31) and a shank (32);
wherein the pressing device (1) further comprises a first threaded member (4) and a second threaded member (5) configured to cooperate with each other; wherein said second threaded member (5) is connected to said second body (3) so that their mutual rotation is prevented;
wherein said first threaded member (4) engages said first body (2) so that its rotation in a first direction causes the two bodies (2, 3) to move away and a rotation thereof in a second direction causes the two bodies (2, 3) to move closer; and
wherein said shank (32) of the second body (3) has a non-circular cross-section and said first body (2) comprises a corresponding main hole (24) with a cross-section complementary to that of the shank (32).
The system of claim 8, wherein said shank (32) has a hexagonal, square, triangular, pentagonal, octagonal, circular cross-section with one or more facets, oval or elliptical and wherein said main hole (24) of the first the body has, correspondingly, a hexagonal, square, triangular, pentagonal, octagonal, circular section with one or more facets, oval or elliptical.
An insulated dry electric transformer (T) comprising: windings (C) blocked with respect to yoke clamps (P); a plurality of systems, with each system comprising a pressing device (1) and a barrier support (101, 102, 103); and electrically insulating barriers (B), wherein each electrically insulating barrier (B) is in the form of a plate of electrically insulating material and wherein at least one of said systems is a system (1) according to any one of claims 1-9.