Patent Publication Number: US-7902950-B2

Title: System for preventing rupture of transformer tank

Description:
TECHNICAL FIELD 
     The present invention relates, in general, to a rupture prevention system and, more particularly, to a system for preventing a transformer tank from rupturing, which increases the limit of the deformation of a tank constituting a transformer, thus reducing the pressure generated in the transformer, and which increases the number of rupture discs installed per unit area, thus eliminating pressure. 
     BACKGROUND ART 
     Generally, transformers are pieces of electrical equipment which change a voltage to a higher or lower voltage. The transformers are classified into oil-immersed transformers and dry-type transformers according to the kind of insulating material. An oil-immersed transformer filled with insulating oil is widely used. The oil-immersed transformer includes a high-voltage winding, a low-voltage winding, an iron core, insulating oil, a tank, and other components. 
     The oil-immersed transformer is constructed so that electric current is supplied through a bushing mounted to a bushing turret. When a breakdown occurs in the transformer due to abnormal voltage caused by lightning or a switching surge, and thus an arc is generated, some of the insulating oil filled in the tank for insulating or cooling the transformer is instantaneously burnt. Due to the combustion of the insulating oil, the internal pressure in the transformer is suddenly increased. Such pressure ruptures the transformer tank, and air fed through the ruptured portion is supplied to an arc generating part, so that a fire may break out. Further, the insulating oil escapes out of the ruptured tank, thus causing environmental pollution. 
     In order to prevent the tank from rupturing, the conventional method of interrupting the supply of electricity to the transformer has been widely used. However, the tank may rupture even due to the rise in pressure occurring prior to interrupting the electricity supply, and thus a device for mechanically eliminating the pressure is required. Thus, an attempt to eliminate localized pressure has been made using rupture discs. However, in the case of a large transformer, the arc generating point may be far from the rupture discs. Hence, before the pressure eliminating operation using the rupture discs is conducted, the tank may rupture. Further, the number of rupture discs is not sufficient compared to the arc energy, so that the tank may rupture before the pressure eliminating operation is performed. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a system for preventing the rupture of a transformer tank wherever the arc is generated in the tank, which increases a limit of the deformation of a tank constituting a transformer, thus primarily preventing a sudden rise in pressure, and which increases the number of rupture discs installed per unit area, thus preventing the rupture of the tank. 
     Technical Solution 
     In order to accomplish the object, the present invention provides a system for preventing a rupture of a transformer tank, which is provided on a transformer and prevents a rupture of the transformer tank due to a sudden rise in pressure in the transformer. 
     The system includes a support part which is installed in the transformer tank and supports a shielding plate for absorbing a magnetic field so that the shielding plate is not directly attached to the transformer tank. 
     A plurality of rupture discs is mounted, respectively, to a plurality of pipes extending outwards from the transformer tank, and is ruptured when pressure in the transformer tank reaches a predetermined pressure level, thus opening passages. 
     A plurality of relief tanks is vertically installed at a position neighboring the transformer, and is coupled to the pipes, thus providing space for storing insulating oil. 
     Further, an oil gauge is mounted at a lower position in each of the relief tanks, and generates a signal when the insulating oil flows into the relief tank, thus informing a manager of rupture of each of the rupture discs and discharge of the insulating oil. 
     Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Herein, detailed descriptions of known functions or constructions will be omitted so that those skilled in the art can clearly understand the gist of the invention. 
       FIG. 1  is a view showing the construction of a rupture prevention system, according to the preferred embodiment of the present invention,  FIG. 2  is a front view showing part of a transformer equipped with the rupture prevention system of  FIG. 1 ,  FIG. 3  is a perspective view showing the transformer equipped with the rupture prevention system of  FIG. 1 ,  FIG. 4  is a perspective view showing the state where shielding plates are installed by a support part of the present invention, and  FIG. 5  is a detailed view showing portion ‘A’ of  FIG. 4 . 
     Referring to  FIGS. 1 to 5 , a rupture prevention system according to the preferred embodiment of the present invention includes a support part  110 , rupture discs  120 , relief tanks  130 , and oil gauges  140 . Such a rupture prevention system increases the limit of deformation of a transformer tank  10  using the support part  110 , and is provided with a plurality of rupture discs  120 , thus efficiently preventing the transformer tank  10  from rupturing due to a sudden rise in internal pressure. 
     The support part  110  is mounted to the inner surface of the tank  10  constituting the transformer, thus supporting shielding plates  111 . Meanwhile, the shielding plates  111  are installed in the transformer tank  10  to absorb a magnetic field. In the prior art, the shielding plates  111  are directly mounted to the tank  10 , thus increasing the strength of the tank  10 , and reducing the limit of the deformation of the tank  10  due to the pressure. However, according to the present invention, the support part  110  is mounted to the inner surface of the tank  10  so as to prevent the shielding plates  111  from being directly mounted to the tank  10 . The support part  110  serves to support the shielding plates  111 . In a detailed description, the shielding plates  111  are welded to the front surface of the support part  110 . Four corners of the support part  110  are bent backwards a predetermined length, thus providing welding parts  113 . The welding parts  113  are welded to the inner wall of the transformer. Pressure transmitting holes  112  for transmitting pressure to the rupture discs  120  are formed at positions corresponding to pipes  121  on which the rupture discs  120  are mounted. The support part  110  defines space for flowing insulating oil between the welding parts  113  which are bent toward the back of the support part and the inner wall of the transformer, thus helping cool the transformer. The support part  110  prevents the shielding plates  111  from being directly mounted to the tank  10 , thus allowing the tank  10  to sensitively react to variations in internal pressure. Meanwhile, when the effect of the magnetic field is slight and thus the shielding plates are not required, the shielding plates and the support part may be omitted. 
     The rupture discs  120  rupture when the internal pressure of the transformer exceeds a predetermined pressure level, thus eliminating the internal pressure. The rupture discs  120  are mounted respectively on the plurality of pipes  121  extending outwards from the transformer tank  10 . Since the rupture discs  120  mounted to the respective pipes  121  are already known, the detailed description of the rupture discs will be omitted. In the prior art, one to three rupture discs  120  were installed. However, according to the present invention, the deformation of the transformer tank fundamentally reduces the internal pressure for 0.08 seconds when an arc is generated. The remaining pressure is secondarily reduced by the rupture discs which are almost simultaneously operated. Thus, the number of rupture discs is calculated so that the increased pressure does not reach the rupture pressure of the tank. This means that the number of rupture discs is multiplied by a factor of 5 or over, compared to the conventional number of rupture discs per unit area. The rupture discs are uniformly installed throughout the surface of the transformer, so that they are operated regardless of the arc generating position, even in the case the rupture discs are distant from the arc generating position. Moreover, the tank to which the invention is applied is made of a high-strength steel plate that has rupture limit pressure twice as high as a conventional tank. When bushing turrets  20  supplying an electric current to the transformer have a large size, the rupture discs  120  may be installed to eliminate pressure generated in the bushing turrets  20 . In a detailed description, subsidiary pipes  122  are installed to couple the bushing turrets  20  to the relief tanks  130 . The rupture discs  120  are mounted to the subsidiary pipes  122 , and rupture when the internal pressure of the bushing turrets  20  rises and exceeds a predetermined pressure level, thus eliminating the pressure. 
     The relief tanks  130  provide space for storing insulating oil discharged through passages which are formed by the rupture of the rupture discs  120 . The relief tanks having a cylindrical shape are vertically installed at a position neighboring the transformer, and are coupled to the transformer tank  110  via the pipes  121 . A flexible tube  123  which is freely bendable is provided on one end of each pipe  121  and is coupled to the relief tank  130 , thus allowing the pipes  121  to be more easily coupled to the relief tanks  130 . The relief tanks  130  are coupled to each other by coupling pipes  131 . When some of the rupture discs  120  are ruptured and passages are formed, insulating oil flows concentratedly into the associated relief tanks  130 . In order to distribute the insulating oil, the relief tanks  130  are coupled to each other via the coupling pipes  131 , so that the discharged insulating oil is distributed to the several relief tanks  130  to be stored therein. 
     Meanwhile, each of the relief tanks  130  is constructed so that the bottom surface  130   a  of the relief tank is inclined toward each oil gauge  140 . This construction allows the oil gauge  140  to more rapidly detect whether insulating oil is being discharged or not. Further, an opening  132  is formed in the upper end of each relief tank  130  to discharge combustion gas fed together with the insulating oil. The opening  132  is formed toward the transformer  100  to prevent a worker from being injured. A steel net  133  is installed in the opening  132  to prevent impurities, insects, and small animals from entering the opening  132 . Further, a manhole  134  is formed at a predetermined position in each relief tank  130 , so that a worker enters the manhole and thus checks the interior and repairs the oil gauge  140 . 
     The oil gauge  140  is mounted to the lower portion in each relief tank  130 , and generates a signal when the insulating oil flows into the relief tank  130 , thus informing a manager of the rupture of each rupture disc  120  and the discharge of the insulating oil. 
     The operation of the system for preventing the rupture of the transformer tank, which is constructed as described above, will be described in the following. 
     For various reasons, the insulation in the transformer may break and the pressure in the transformer may increase suddenly. At this time, the transformer tank  10  is deformed and thus expands, thus primarily reducing the pressure, because, as described above, the shielding plates  111  are not directly mounted to the transformer tank  10  using the support part  110  so as to increase the limit of the deformation of the transformer tank  10 . The pressure is reduced due to the deformation of the transformer tank  10 , and simultaneously, the rupture discs  120 , which rupture when a pre-determined pressure level is reached, are operated, so that the combustion gas and the insulating oil are discharged through the pipes  121  to the relief tanks  130 , thus eliminating the pressure generated in the transformer. Meanwhile, when the insulating oil discharged through the pipes  121  flows into the relief tanks  130 , the oil gauges  140  generate signals. In response to the signals, a manager can rapidly check the condition of the transformer. 
     Although the preferred embodiment according to the present invention has been disclosed with reference to the accompanying drawings, the invention is not limited to the embodiments illustrated in the drawings, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
     ADVANTAGEOUS EFFECTS 
     As described above, the limit of the deformation of a tank constituting a transformer is increased, and in addition, the number of rupture discs installed per unit area is increased, thus more effectively eliminating internal pressure caused by abnormal voltage. Moreover, even when an arc is generated at a position distant from the rupture discs, the transformer tank is deformed, thus eliminating pressure, therefore allowing the transformer to be more safely manufactured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing the construction of a rupture prevention system, according to the preferred embodiment of the present invention, 
         FIG. 2  is a front view showing part of a transformer equipped with the rupture prevention system of  FIG. 1 , 
         FIG. 3  is a perspective view showing the transformer equipped with the rupture prevention system of  FIG. 1 , 
         FIG. 4  is a perspective view showing the state where shielding plates are installed by a support part of the present invention, and 
         FIG. 5  is a detailed view showing portion ‘A’ of  FIG. 4 . 
     
    
    
     DESCRIPTION OF REFERENCE CHARACTERS OF IMPORTANT PARTS 
     
         
         
           
             ( 10 ): tank ( 20 ): bushing turret 
             ( 100 ): transformer ( 110 ): support part 
             ( 111 ): shielding plate ( 112 ): pressure transmitting hole 
             ( 113 ): welding part 
             ( 120 ): rupture disc ( 121 ): pipe 
             ( 122 ): subsidiary pipe ( 123 ): flexible tube 
             ( 130 ): relief tank ( 131 ): coupling pipe 
             ( 132 ): opening ( 133 ): steel net 
             ( 140 ): oil gauge