Patent Application
20120056702
This application claims benefit of Serial No. 10380114.8, filed 3 Sep. 2010 in the European Patent Office and which application is incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.
The present invention refers to a measurement and protective high, medium and low voltage transformer of the type comprising a magnetic core with primary and secondary windings, all of which are molded on the outside with resin, with the formation of a single-piece outer enclosure made of resin, the main objective of the present invention consisting in obtaining a transformer design with all safety guarantees and durability in particular in ambient conditions of high or extremely high humidity.
High, medium or low voltage transformers of this type are devices that are usually installed at various points of high or medium voltage lines of an electrical distribution network.
Measurement transformers are mainly used for installing instruments, counters y protective relays in medium or high voltage circuits, and their task is to insulate measurement or relay circuits, thus allowing greater standardization in the construction of counters, instruments or relays.
The process for manufacturing conventional high, medium or low voltage transformers consists in manufacturing the core and windings and molding the outer enclosure of the transformer with resin. The primary and secondary connections go out from the core. These primary and secondary connections are precisely the ones that are particularly susceptible to becoming easily damaged by external influences, thus impairing the entire functioning of the transformer.
Accordingly, one of the main drawbacks of this type of transformers is their high susceptibility in humid conditions and environments or in immersed environments, due to the fact that they are not sufficiently prepared for withstanding such extreme circumstances, which means that transformers of this type can become totally or partially damaged when continuously or sporadically exposed to such humid environments.
Taking into account that these transformers are installed in various types of terrain, usually inside larger rooms for protection (usually referred to as “stations”), it is easy to understand that climatic conditions such as rain, flooding or humidity can cause flooding in these stations, thus inevitably affecting the correct functioning of the transformer(s) housed on the inside and causing the electrical protective devices of the entire electrical zone or area to become interrupted until repair of the breakdown can be achieved and the electrical service resumed.
The solution to solving this problem has previously consisted in insulating the entire outer area of the station, preferentially made of concrete, in which the voltage transformers are installed, from water and humidity by applying and sealing a water-insulating material or element. However, such a solution involves very high costs necessary for sealing the entire outer surroundings of the transformer station.
For all these reasons, the objective of the present invention is to overcome the disadvantages associated with the prior art and provide a new method of constructing low, medium and high voltage transformers capable of withstanding ambient conditions of very high humidity with potential flooding, and withstanding immersion in water without failing or breaking down.
The present invention proposes a high, medium or low voltage transformer comprising a magnetic core with primary and secondary windings and primary and secondary connections of the transformer, with the special feature that all these elements are molded while they are completely embedded in a mass of resin, thus forming the entire outer single-piece enclosure or housing of the transformer, so that at least the inner part of the terminals of the corresponding primary and secondary connections of the transformer remain completely embedded in said mass of resin, so that the contact surface of the primary connection and the secondary connection(s) with the housing are completely insulated from water, said transformer being suitable for immersion in water and also for withstanding conditions in humid environments at extremely high hydrophilic levels.
The primary connection of the transformer is arranged in the upper part of the transformer, whereas the secondary connections of the transformer are located in the lower part. Said connections can be connectors (that is, metal terminals) or simply cables, depending on the type of transformer. The secondary connection(s) mentioned preferably go in pairs, i.e., they can be 2, 4, 6, etc., although there can also be only one.
As mentioned above, if the primary and secondary connections are conductors (that is, metal terminals), at least an inner portion of the terminals of the corresponding primary and secondary connections of the transformer are completely embedded and trapped in said mass of resin; however, according to a second embodiment of the invention, said primary and secondary connections can be simple cables, so that a portion of said cables is completely embedded and trapped in said mass of resin, so that the contact surface of the corresponding cables together with the single-piece housing are completely insulated from water.
Said resin layer which forms the outer housing of the transformer is manufactured by resin molding technology. If the connections are made via connectors, said connectors are placed at the appropriate position inside the mold insert before the molding operation of the resin, so that the resin is poured onto said connector, and the latter remains partially embedded inside the mass of resin with its front part. Precisely said front part is the one that is used for connection to an external connector.
The type of resin used for molding the outer housing to a single-piece is preferably an epoxy type resin, which has excellent properties as electrical insulator, although alternatively other resins with equivalent properties can also be used.
The wall thickness of the mass of resin up to the winding is a function of the required insulating voltage en each type of transformer and can range, for example, from a few millimetres to a few centimetres.
Optionally, this resin housing can be coated on the outside with a metallized layer, suitable for preventing adverse effects from external influences that act on the transformer during its lifetime and also act as mass and thus serve as electric insulator.
According to a second embodiment of the invention, said resin housing can be coated on the outside with a silicone layer or a similar material, in order to provide a higher degree of insulation against water.
According to a third embodiment of the invention, said resin housing can be coated on the outside with a metallized layer, and said layer can be coated on the outside with a second silicone layer, in order to provide double insulation or protection against external influences and against water.
Both layers (metallized layer and silicone layer) are applied by spraying methods or other equivalent painting methods.
An earth connection will also be available and arranged close to the secondary connection.
Optionally, the magnetic core with the primary and secondary windings can initially be placed inside a plastic housing arranged around the entire core of the transformer or part of it, which serves as support for certain auxiliary elements. This is followed by molding them inside the resin mold insert, which, upon setting, forms the outer resin housing to a single piece.
Advantageously, it has been found in an empirical trial that this transformer can be immersed in water down to a depth of 20 metres without suffering damage and can also withstand the conditions of humid environments at extremely high hydrophilic levels.
It goes without saying that the outer configuration of the transformer enclosure can vary according to the transformer specifications in each case, preference being given to a substantially outer prismatic configuration.
The process of constructing the transformer disclosed by the present invention mainly comprises the steps of:
Preferably, the molding operation of the mass of resin is carried out under vacuum.
The main elements will now be described in detail, all of which will be accompanied by a number in the attached figures; (10) transformer, (11) mass of resin, (12) outer metallic or silicone coating, (13) magnetic core, (14) windings, (15) cover of the primary connector (16), (16) primary connector, (16′) primary cable, (18) secondary connectors, (18′) secondary cables, (19) mounting base, (20) openings for the anchoring means, (21) cable of the primary circuit, (22) cable of the secondary circuit.
In one of the preferred embodiments of the invention, as can be seen from
In the special case of the embodiments of
In the special case of the embodiment of
In the special case of the second embodiment corresponding to
After having sufficiently described the present invention with reference to the attached figures, it goes without saying that any modifications which are deemed convenient can be made to the invention, as long as the essential aspects of the present invention, which is summarized in the following claims, are not changed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10380114.8 | Sep 2010 | EP | regional |
