Apparatus for filling oil in a hermetic type oil-filled electric transformer and method for filling oil in a hermetic type oil-filled electric transformer by means of the aforesaid apparatus

Abstract

An apparatus (1) for filling oil in a hermetic type oil-filled electric transformer (100). The apparatus comprises a tank (2) defining a containment chamber (3) open at the top and a connecting mouth (4) defined at its own bottom (2a), a hollow duct (5) arranged in the tank (2) coaxially to the connecting mouth (4), a closure cap (6) arranged above the hollow duct (5). This hollow duct (5) has, at the first lower end (5a), one or more side openings (9) to allow communication of the internal space of the hollow duct (5) with the containment chamber (3) and, at the second upper end (5b), one or more side openings (10) to put in communication the internal space of the hollow duct (5) with the external environment.

Description

[0001] APPARATUS FOR FILLING OIL IN A HERMETIC TYPE OIL-FILLED ELECTRIC TRANSFORMER AND METHOD FOR FILLING OIL IN A HERMETIC TYPE OIL-FILLED ELECTRIC TRANSFORMER BY MEANS OF THE AFORESAID APPARATUS.

[0002] DESCRIPTION

[0003] The present invention relates to an apparatus for filling oil in a hermetic type oil-filled electric transformer.

[0004] Likewise, the present invention relates to a method for filling oil in a hermetic type oil-filled electric transformer by means of the aforesaid apparatus.

[0005] It is known that an oil-filled electric transformer is an electromechanical device used to transform electrical energy from one voltage level to another, in an efficient and safe manner. It is called “oil-filled” because it uses insulating oil (often mineral oil) to cool and insulate its internal components.

[0006] It is also known that there are two types of oil-filled transformers, the hermetic oil-filled transformers and the oil-filled transformers with conservator.

[0007] They are both types of transformers immersed in insulating oil, but they differ in the way they handle the oil volume, cooling system and the thermal expansion of the oil during operation.

[0008] In particular, the hermetic oil-filled transformer is a type of transformer in which the oil is contained in a completely sealed tank. There is no direct contact between the oil and the external air, and therefore the oil is not exposed to humidity or oxygen. The advantages of this type of oil-filled transformer consist in greater protection against oxidation and humidity and reduced maintenance, and therefore it is ideal for harsh environments or where maintenance is complicated.

[0009] However, disadvantageously, such hermetic type oil-filled transformers require an oil filling methodology that is complex and prolonged over time in order to prevent air from being able to flow within the oil circuit of the same transformer together precisely with the oil.

[0010] In fact, in the event that there is an amount of air inside the hermetically closed oil circuit, it could not be vented and this could compromise the insulation and cooling functionality of the oil itself and, consequently, could bring the electrical transformer into a protected state, thus preventing its operation.

[0011] To avoid such phenomena, the oil circuit of a hermetic type oil-filled transformer is filled in an autoclave, connecting the same transformer to a filling circuit and generating a vacuum. This procedure avoids the formation of air bubbles inside the oil circuit. However, this procedure requires a considerable amount of time due to the connection of the transformer to the filling circuit and the generation of the vacuum, and it also requires the constant presence of an operator who monitors from outside the autoclave the filling status of the oil circuit of the electrical transformer until completion thereof.

[0012] On the other hand, as to the oil-filled transformers with conservator, they are equipped with an additional tank, called a conservator, which serves to contain the expansion of the insulating oil during operation. In this system, the oil inside the transformer does not completely fill the main tank, but it is connected to this additional tank that allows better management of changes in temperature and volume of the oil. In addition, this tank prevents air from being able to flow into the oil circuit causing the drawbacks described above.

[0013] However, since in such a conservator tank the oil can come into contact with the air, this can lead to a greater risk of oxidation and degradation of the oil over time, resulting in a greater risk of oil contamination and therefore requiring more frequent maintenance.

[0014] The present invention intends to overcome the aforesaid drawbacks of the prior art.

[0015] In particular, it is an object of the invention to realize an apparatus for filling oil in a hermetic type oil-filled electric transformer that allows to simplify and speed up the filling process of such oil-filled electric transformers.

[0016] Furthermore, it is an object of the invention to realize an apparatus for filling oil in a hermetic type oil-filled electric transformer that does not require the supervision of an operator during such filling process.

[0017] The above objects are achieved by an apparatus according to claim 1.

[0018] Further characteristics of the apparatus according to claim 1 are described in the dependent claims.

[0019] Likewise, these objects are also achieved by the method for filling oil in a hermetic type oil-filled electric transformer by means of the aforesaid apparatus of the invention.

[0020] The aforesaid objects, together with the advantages that will be mentioned hereinafter, are highlighted by the description of an embodiment of the invention, which is given by way of non-limiting example with reference to the attached drawings, where: - fig. 1 depicts an axonometric view from above of an apparatus of the invention for filling oil in a hermetic type oil-filled electric transformer;

[0021] - fig. 2 depicts an axonometric view from below of the apparatus of fig. 1 ; - fig. 3 depicts a first side view of the apparatus of fig. 1 ;

[0022] - fig. 4 depicts a second side view of the apparatus of fig. 1 ;

[0023] - fig. 5 depicts a top view of the apparatus of fig. 1 ;

[0024] - fig. 6 depicts a bottom view of the apparatus of fig. 1 ;

[0025] - fig. 7 depicts a sectional view according to section line VII-VII of the apparatus of fig. 1 ;

[0026] - fig. 8 depicts a sectional view according to section line VIII-VIII of the apparatus of fig. 1;

[0027] - fig. 9 schematically depicts the effect of air and oil outflow within the apparatus of the invention, during the execution of the method of the invention;

[0028] - fig. 10 depicts the apparatus of the invention of fig. 1 applied to a hermetic type oil-filled transformer.

[0029] The apparatus of the invention for filling oil in a hermetic type oil-filled electric transformer is depicted in isolation in figs. 1 to 8 and is associated with the aforesaid hermetic type oil-filled electric transformer 100 in fig. 10, where it is indicated with 1.

[0030] Said apparatus 1 comprises a tank 2 defining a containment chamber 3, open at the top, where said tank 2 comprises, at its own bottom 2a, a connecting mouth 4 for hermetic connection with an opening 101 defined along the oil circuit of the hermetic type oil-filled electric transformer 100.

[0031] According to the preferred embodiment of the invention, said tank 2 has a cylindrical side body 2b connected below the bottom 2a of substantially conical shape, where at the vertex V of the aforesaid bottom 2a the connecting mouth 4 is defined.

[0032] It is not excluded, however, that according to alternative embodiments of the invention the tank 2 may have a shape different from that described for the preferred embodiment, as long as it is able to perform the functions described below.

[0033] The apparatus 1 of the invention further comprises a hollow duct 5 arranged in the tank 2, coaxially to the connecting mouth 4, as visible in figs. 7 and 8. This hollow duct 5 is, in particular, fixed, at a first end 5a, to the bottom 2a of the tank 2. Preferably but not necessarily, the hollow duct 5 has a substantially cylindrical shape.

[0034] In particular, as evident from figs. 7 and 8, this hollow duct 5 has a diameter smaller than the diameter of the side body 2b of the tank 2.

[0035] Furthermore, the apparatus 1 also comprises a closure cap 6 arranged above the hollow duct 5 and fixed to a second end 5b of the same hollow duct 5, so as to tighten the latter above.

[0036] More precisely, preferably but not necessarily, the closure cap 6 has a flat element 7 arranged above the second end 5b of the hollow duct 5 and has a greater extension than the hollow duct 5. Furthermore, this flat element 7 has its own perimeter edge 7a folded towards the inside of the tank 2.

[0037] The function of these characteristics will be clarified during the description of the method for filling the oil circuit of the hermetic type oil-filled transformer 100, by means of the apparatus 1 of the invention.

[0038] Furthermore, according to the preferred embodiment of the invention, the closure cap 6 is fixed to the tank 2 by means of a fixing bar 8.

[0039] According to the invention, the hollow duct 5 has, at its first end 5a, a plurality of side openings 9 to allow communication of the internal space of the same hollow duct 5 with the containment chamber 3.

[0040] It is not excluded that, according to an embodiment variant of the apparatus 1 of the invention, only one side opening 9 is made.

[0041] Furthermore, again according to the invention, the hollow duct 5 has, at its second end 5b, a plurality of side openings 10 to put in communication above the internal space of the hollow duct 5 with the external environment.

[0042] Also in this case, it is not excluded that, according to an embodiment variant of the apparatus 1 of the invention, only a side opening 10 is made.

[0043] The preferred embodiment of the invention further provides that the apparatus 1 comprises a drain pipe 11 having a first end 11a inserted through the connecting mouth 4 and a second end 11b exiting from the bottom 2a of the tank 2, towards the external environment.

[0044] During the execution of the method of the invention, said drain pipe 11 is closed at the second end 11b. This drain pipe is opened when there is a need to empty the containment chamber 3 of the tank 2, i.e. at the end of the method of the invention.

[0045] Finally, preferably but not necessarily, the apparatus 1 of the invention comprises an overflow duct 12 that puts in communication the containment chambers 3 with the external environment and this overflow duct 12 is defined along the tank 2, in particular along the side body 2b, at a lower height of the openings 10, so that the oil level in the aforesaid containment chamber 3 can never reach the height of the aforesaid openings 10.

[0046] As mentioned above, the method for filling oil in a hermetic type oil-filled electric transformer 100 by means of the apparatus 1 of the invention is also part of the invention.

[0047] In particular, this method provides for the following steps:

[0048] - arranging a hermetic type oil-filled electric transformer 100 in an external environment;

[0049] - opening the opening 101 defined along the oil circuit of the hermetic type oil-filled electric transformer 100 and facing upwards;

[0050] - hermetically fixing the connecting mouth 4 of the apparatus 1 to the aforesaid opening 101;

[0051] - filling the tank 2 of the apparatus 1 with oil so as to allow the outflow by gravity of the oil inside the oil circuit of the hermetic type oil-filled electric transformer 100 until the oil circuit is filled;

[0052] - inserting the hermetic type oil-filled electric transformer 100 connected to the apparatus 1 into an autoclave;

[0053] - topping up the tank 2 with oil so that the oil level is higher than the side openings 9 made at the first end 5a of said hollow duct 5 and lower than the side openings 10 made at the second end 5b of the same hollow duct 5, as visible in fig. 9;

[0054] - generating the vacuum in the autoclave;

[0055] - leaving the hermetic type oil-filled electric transformer 100 in the autoclave until the air trapped in the oil circuit has completely escaped through the apparatus 1 ;

[0056] - breaking the vacuum inside the autoclave;

[0057] - disconnecting the apparatus 1 from the hermetic type oil-filled electric transformer 100;

[0058] - hermetically closing the opening 101 of the oil circuit of the hermetic type oil-filled electric transformer 100;

[0059] - removing the hermetic type oil-filled electric transformer 100 from the autoclave. In particular, during the vacuum step inside the autoclave, the air A present inside the oil circuit of the hermetic type oil-filled electric transformer 100 together with a portion of oil O is made to outflow by depression through the hollow duct 5. In this way, the air A escapes through the side openings 10 defined in the second end 5b of the hollow duct 5, while the oil portion O, by knocking against the closure cap 6, falls back down by gravity inside the hollow duct 5 towards the bottom 2a of the tank 2, as schematically represented in fig. 9.

[0060] Advantageously, therefore, with the aforesaid method of the invention for filling the oil circuit, this filling takes place in an external environment and not in an autoclave, as instead provided for by the prior art, without the need to arrange the hermetic type oil-filled electric transformer 100 inside the autoclave, connecting it to the filling system and without the need for the presence of an operator to monitor the filling step in the autoclave once the vacuum has been created in the same autoclave. This considerably reduces the filling time and manpower to perform such a filling operation. Furthermore, advantageously, even if the method of the invention provides for inserting in any case the hermetic type oil-filled electric transformer 100 into the autoclave, this operation takes place with the transformer already filled with oil, and therefore this step of the method can take place without monitoring by an operator, thanks to the use of the apparatus 1 of the invention. Therefore, this air outflow step can also be performed during non-working hours, for example at night.

[0061] In particular, thanks to the fact that, during this air outflow step, the oil, which is accidentally made to outflow from the oil circuit of the transformer, meets along its path the aforesaid closure cap 6 of the apparatus 1 of the invention on which the same oil hits and is redirected inside the tank 2, the oil is prevented from escaping into the autoclave, thus allowing this step to be carried out without the aid of an operator.

[0062] Even more in detail, the fact that the flat element 7 of the closure cap 6 has a greater extension than the hollow duct 5 and the fact that the perimeter edge 7a of the aforesaid flat element 7 is folded towards the inside of the tank 2, prevents any portion of oil that should escape from the openings 10 from being dispersed inside the autoclave. In fact, precisely, even if a portion of oil were to pass through said openings 10, the same portion of oil would be forced by the particular conformation of the aforesaid closure cap 6 towards the inside of the tank 2.

[0063] In addition, the fact of filling the tank 2 with an oil level higher than the side openings 9 prevents air from being able to enter the oil circuit of the hermetic type oil-filled electric transformer 100 during the vacuum step.

[0064] Practically, it has been established that the invention achieves the intended objects.

[0065] In particular, the object of realizing an apparatus for filling oil in a hermetic type oil-filled electric transformer that allows to simplify and speed up the filling process of such oil-filled transformers is achieved.

[0066] Furthermore, the object of realizing an apparatus for filling oil in a hermetic type oil-filled electric transformer that does not require the supervision of an operator during said filling process is also achieved.

Claims

CLAIMS1 ) Apparatus (1 ) for filling oil in a hermetic type oil-filled electric transformer (100), comprising:- a tank (2) defining a containment chamber (3) open at the top, said tank (2) comprising, at its own bottom (2a), a connecting mouth (4) for hermetic connection with an opening (101 ) defined along the oil circuit of said hermetic type oil-filled electric transformer (100);said apparatus (1) being characterized by comprising:- a hollow duct (5) arranged in said tank (2) coaxially to said connecting mouth (4), said hollow duct (5) being fixed, at its own first end (5a), to the bottom (2a) of said tank (2);- a closure cap (6) arranged above said hollow duct (5) and fixed to its own second end (5b) so as to tighten said hollow duct (5) above;said hollow duct (5) having, at said first end (5a), one or more side openings (9) to allow communication of the internal space of said hollow duct (5) with said containment chamber (3), said hollow duct (5) also having, at said second end (5b), one or more side openings (10) to put in communication the internal space of said hollow duct (5) with the external environment.2) Apparatus (1 ) according to claim 1 , characterized in that said tank (2) has a cylindrical side body (2b) connected below said bottom (2a) of substantially conical shape, where, at the vertex (V) of said bottom (2a), said connecting mouth (4) is defined.3) Apparatus (1) according to claim 2, characterized in that said hollow duct (5) has a substantially cylindrical shape with a diameter smaller than the diameter of said side body (2b) of said tank (2).4) Apparatus (1) according to any one of the preceding claims, characterized in that it comprises a drain pipe (11) having a first end (11a) inserted through said connecting mouth (4) and a second end (11 b) exiting from said bottom (2a) of said tank (2).5) Apparatus (1) according to any one of the preceding claims, characterized in that said closure cap (6) has a flat element (7) arranged above said second end (5b) of said hollow duct (5) and having a greater extension than said hollow duct (5), said flat element (7) having its own perimeter edge (7a) folded towards the inside of said tank (2).6) Apparatus (1) according to any one of the preceding claims,characterized in that said closure cap (6) is fixed to said tank (2) by means of one or more fixing bars (8).7) Method for filling oil in a hermetic type oil-filled electric transformer (100) by means of the apparatus (1) according to any one of the preceding claims, characterized by providing for the following steps:- arranging a hermetic type oil-filled electric transformer (100) in an external environment;- opening the opening (101) defined along the oil circuit of said hermetic type oil-filled electric transformer (100) and facing upwards;- hermetically fixing the connecting mouth (4) of said apparatus (1) to said opening (101);- filling said tank (2) of said apparatus (1 ) with oil so as to allow the outflow by gravity of said oil inside said oil circuit of said hermetic type oil-filled electric transformer (100) until said oil circuit is filled;- inserting said hermetic type oil-filled electric transformer (100) connected to said apparatus (1) into an autoclave;- filling said tank (2) with oil so that the level of said oil is higher than the side openings (9) made at said first end (5a) of said hollow duct (5) and is lower than the side openings (10) made at said second end (5b) of said hollow duct (5);- generating the vacuum in said autoclave;- leaving said hermetic type oil-filled electric transformer (100) in said autoclave until the air trapped in said oil circuit has completely escaped through said apparatus (1);- breaking the vacuum inside said autoclave;- disconnecting said apparatus (1) from said hermetic type oil-filled electric transformer (100);- hermetically closing said opening (101 ) of said oil circuit of said hermetic type oil-filled electric transformer (100);- removing said hermetic type oil-filled electric transformer (100) from said autoclave.8) Method according to claim 7, characterized in that, during said vacuum step inside the autoclave, the air (A) present inside said oil circuit of said hermetic type oil-filled electric transformer (100) together with a portion of oil (O) is made to outflow by depression through said hollow duct (5), said air (A)escaping through said one or more side openings (10) defined in said second end (5b) of said hollow duct (5), while said portion of oil (0), by knocking against said closure cap (6), falls back down inside said hollow duct (5) by gravity towards the bottom (2a) of said tank (2).9) Method according to any one of claims 7 or 8 in combination with claim 4, characterized by providing, before said step of decoupling said apparatus (1) from said hermetic type oil-filled electric transformer (100), to empty the oil from said tank (2) by means of said drain pipe (11 ).

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