Front-inserted fuse three-phase integrated voltage transformer and manufacturing method

Abstract

The present invention discloses a front-insert type three-phase integrated voltage transformer and a processing method thereof. Main components such as three main voltage transformers, one zero-sequence voltage transformer core, a high-voltage shielding device, a low-voltage shielding device, a fuse and its connection components are fixed in a mold using appropriate jigs, and are cast and molded with epoxy resin. After the surface of the voltage transformer casting is sprayed with metal shielding, insulating paint is sprayed for protection. By using a brand-new structure, a brand-new design concept and optimizing the electric field distribution, the partial discharge of the front-insert type three-phase integrated ferromagnetic resonance-proof (4PT principle) fully shielded voltage transformer with 24 kV fuses on the outer surface is far lower than the requirements of national and international standards, and can effectively prevent the occurrence of ferromagnetic resonance, reducing the economic losses of users. When the fuse needs to be replaced, the voltage transformer can be completely not moved, and only the primary cable head connecting the voltage transformer to the cabinet needs to be removed and the metal bolt unscrewed to take out the fuse.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement and protection of power systems, and particularly to a front-insert type three-phase integrated voltage transformer applicable to the 24 kV voltage level and a processing method thereof. Background Art

[0002] For the voltage transformers used in 24 kV voltage level box-type gas-insulated metal-enclosed switchgear cabinets and ring network power supply load switchgear cabinets (hereinafter referred to as "ring network cabinets"), three single-phase voltage transformers are usually configured. Although a harmonic eliminator is configured, the harmonic elimination effect of this method is not good and it is easy to cause the transformer to burn out, and at the same time, it brings certain economic losses to users. And some manufacturers will configure a zero-sequence voltage transformer with three single-phase voltage transformers to prevent ferromagnetic resonance. Although this method can effectively prevent the occurrence of resonance, arranging three single-phase voltage transformers and a zero-sequence voltage transformer requires a large space.

[0003] Moreover, in the power system, there are often some force majeure factors that cause the fuse of the voltage transformer to blow. At this time, the fuse needs to be replaced. Affected by the structure, for the traditional fully shielded voltage transformer on the outer surface, considering the shielding effect and electric field distribution, the fuse inlet and outlet of the traditional fully shielded voltage transformer are on the opposite side of the primary high-voltage end (i.e., the rear end of the transformer). When replacing the fuse, it is necessary to remove the fixing screws of the voltage transformer bottom plate and the cabinet body and remove the primary high-voltage cable elbow, and then pull the voltage transformer out of the cabinet body, use tools to remove the blind head at the rear end of the voltage transformer and unscrew the fixing fuse bolt to take out the fuse. After the replacement is completed, the voltage transformer needs to be "returned the same way". The whole process not only wastes time and manpower, but may even scratch the metal layer on the outer surface of the voltage transformer, causing the electric field distribution on its outer surface to change and forming a hidden danger.

[0004] Moreover, the 24 kV voltage transformer has a large insulation margin requirement, a large fuse diameter, and integrates the zero-sequence PT to form a three-phase integrated anti-ferromagnetic resonance (4PT principle) voltage transformer. Considering its outer surface sprayed with metal shielding, the electric field distribution is extremely complex, and it is extremely difficult to pass the partial discharge test. Therefore, the existing shielding structure cannot meet the use requirements. Summary of the Invention

[0005] An improvement is made in view of at least one defect of the prior art. The present invention provides a front-insert type three-phase integrated voltage transformer, which solves the problems of easy resonance, large space occupation, and the shielding structure not meeting the equipment use requirements of the voltage transformer under the 24 kV voltage level.

[0006] The technical solution adopted by the present invention is a front-inserted three-phase integrated voltage transformer for fuses, which includes 3 main voltage transformers, 1 zero-sequence voltage transformer, a high-voltage shielding device, a low-voltage shielding device, a fuse and its connection components, a secondary outlet box and a mounting base plate. The common ends of the 3 main voltage transformers are connected together by a metal conducting rod. The common ends of the 3 main voltage transformers are connected to the primary winding on the body of the zero-sequence voltage transformer through a connecting wire. The 3 main voltage transformers are respectively connected to secondary embedded nuts through secondary leads. The secondary embedded nuts are installed in the secondary outlet box. The high-voltage shielding device includes a front-segment high-voltage shielding device and a rear-segment high-voltage shielding device. The fuse and its connection components include a fuse, a metal nut, a metal contact, a spring, a first conducting rod, and a metal connecting piece. A fuse cavity is horizontally arranged above the main voltage transformer. The front end of the fuse cavity is connected to the metal nut, and the rear end of the fuse cavity is installed with the metal contact. The metal contact is of a ring structure. The front side of the metal contact is provided with an external thread for threaded connection with the rear-segment high-voltage shielding device. The rear side of the metal contact is provided with an internal thread for screwing connection with the spring. The rear end of the metal contact is connected to the first conducting rod. The metal wiring piece is connected to the body of the main voltage transformer. The first conducting rod is of a special-shaped rod structure. The two ends of the first conducting rod are respectively welded to the metal contact and the metal wiring piece, and the three are fixed together at the spatial position required by the design requirements. The fuse is placed in the fuse cavity, and the rear end abuts against the spring and is connected to the body of the voltage transformer through the first conducting rod and the metal wiring piece. The front end is tightly fixed by a metal bolt in the metal nut. The rear side of the metal nut is provided with an external thread for threaded connection with the front-segment high-voltage shielding device. The front-segment high-voltage shielding device is sleeved with a low-voltage shielding device. Other structures except the mounting base plate are fixed in a mold according to the design position and formed into a transformer body through resin casting. The lower part of the transformer body is connected to the mounting base plate.

[0007] Preferably, the two end faces on the opposite sides of the front-segment high-voltage shielding device and the rear-segment high-voltage shielding device do not contact.

[0008] Preferably, an anti-tracking umbrella skirt is provided at the upper end of the zero-sequence voltage transformer, and a second conducting rod is embedded in the center of the anti-tracking umbrella skirt and connected to the primary coil of the zero-sequence voltage transformer.

[0009] Preferably, the metal nut is located inside the TYPE-C external cone.

[0010] Preferably, the outer surface of the metal conducting rod at the common end of the 3 main voltage transformers is coated with semiconductor self-adhesive tape and semiconductor crepe paper.

[0011] Preferably, the outer surface of the transformer body is sprayed with metal shielding and then sprayed with insulating paint.

[0012] Preferably, the outer surfaces of the metal contact and the metal nut are both coated with semiconductor self-adhesive tape and semiconductor crepe paper.

[0013] Preferably, the outer surface of the high-voltage shielding device is sandblasted and then sprayed with semiconductor paint.

[0014] A front-inserted three-phase integrated voltage transformer for a fuse has the following processing method steps:

[0015] Step 1: Fix the high-voltage shielding net on the metal nut to form the front-section high-voltage shielding device;

[0016] Step 2: Screw the rear-section high-voltage shielding device onto the external thread of the metal contact to form the rear-section high-voltage shielding device;

[0017] Step 3: Fix the two sections of the high-voltage shielding device in the mold through a suitable tooling;

[0018] Step 4: Fix the bodies of 3 main voltage transformers and the body of 1 zero-sequence voltage transformer in the mold;

[0019] Step 5: Weld the end of the secondary lead of the voltage transformer to the secondary embedded nut and fix it on the mold;

[0020] Step 6: Connect half of the coils of the 3 main voltage transformers of the voltage transformer through a metal conducting rod to form the common end of the main voltage transformer;

[0021] Step 7: Connect the common end of the main voltage transformer to the primary winding of the zero-sequence voltage transformer through a connecting wire;

[0022] Step 8: Fix the first conducting rod, metal connecting piece, and metal contact by welding or riveting;

[0023] Step 9: Connect and fix the metal connecting piece to the primary wire of the other half of the main voltage transformer coil;

[0024] Step 10: Pass the low-voltage shielding device through the front-section high-voltage shielding device of the fuse and fix it on the mold;

[0025] Step 11: Fix one end of the second conducting rod to the primary coil of the zero-sequence voltage transformer, and then fix the other end of the second conducting rod on the mold;

[0026] Step 12: Pour with epoxy resin to form a casting body with a fuse cavity, TYPE-C external cone, anti-climbing umbrella skirt, and secondary outlet box, and then spray the outer surface with metal shielding and protective paint to form the voltage transformer body for standby;

[0027] Step 13: Fix the mounting base plate on the voltage transformer body with screws;

[0028] Step 14: Fix the metal nameplate on the secondary outlet box with screws;

[0029] Step 15: Tighten the secondary outgoing line waterproof joint on the secondary outgoing line box to complete the production.

[0030] The beneficial effects of the present invention are as follows: By using a new structure, a new design concept, and optimizing the electric field distribution, the partial discharge of the fully shielded voltage transformer on the outer surface of the 24kV fuse front-inserted three-phase integrated anti-ferromagnetic resonance (4PT principle) is far lower than the requirements of national and international standards, and it can effectively prevent the occurrence of ferromagnetic resonance, reducing the economic losses of users. When the fuse needs to be replaced, the voltage transformer can be completely not moved, and only the primary cable head connecting the voltage transformer to the cabinet needs to be removed and the metal bolt screwed out to take out the fuse. The connection between the voltage transformer and the switch cabinet is a cable connection method, which can ignore the stress on the primary high-voltage end, improve the operation stability of the product, and the placement position and placement angle of the voltage transformer have a large selection range, which can effectively prevent the occurrence of ferromagnetic resonance and make it more convenient for operators to replace the fuse. Description of the Drawings

[0031] Figure 1 It is a schematic cross-sectional structure diagram of the voltage transformer body.

[0032] Figure 2 It is a side view of the fuse front-inserted three-phase integrated voltage transformer.

[0033] Figure 3 It is a front view of the fuse front-inserted three-phase integrated voltage transformer.

[0034] Figure 4 It is a schematic diagram of the connection of the common terminal of the fuse front-inserted three-phase integrated voltage transformer.

[0035] Markings in the figure: 1 - metal nut, 2 - front-section high-voltage shielding device, 3 - low-voltage shielding device, 4 - epoxy resin, 5 - rear-section high-voltage shielding device, 6 - metal connecting piece, 7 - fuse, 8 - fuse cavity, 9 - spring, 10 - metal contact, 11 - first conductive rod, 12 - second conductive rod, 13 - anti-tracking umbrella skirt, 14 - main voltage transformer body, 15 - secondary outgoing line box, 16 - secondary embedded nut, 17 - zero-sequence voltage transformer body, 18 - installation base plate, 19 - TYPE-C external cone, 20 - secondary outgoing line waterproof joint, 21 - main voltage transformer common terminal, 22 - connecting wire, 23 - metal conductive rod, 24 - metal bolt. Detailed Embodiment

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Usually, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations. The "front end" and "front side" mentioned in the text refer to Figure 1 the right side in the view direction, and the "rear end" and "rear side" refer to Figure 1 the left side in the view direction.

[0037] As Figure 1 shown, a front-inserted three-phase integrated voltage transformer for a fuse includes 3 main voltage transformers, 1 zero-sequence voltage transformer, a high-voltage shielding device, a low-voltage shielding device 3, a fuse and its connection components, a secondary outlet box 15, and a mounting base plate 18. The common terminals 21 of the 3 main voltage transformers are connected together by a metal conducting rod 23. The common terminals 21 of the 3 main voltage transformers are connected to the primary winding on the body 17 of the zero-sequence voltage transformer through a connecting wire 22. The 3 main voltage transformers are respectively connected to the secondary embedded nuts 16 through secondary leads. The secondary embedded nuts 16 are installed in the secondary outlet box 15. A fuse and its connection components are provided above each main voltage transformer. As Figure 4 shown, the outer surface of the metal conducting rod 23 of the common terminals 21 of the 3 main voltage transformers is coated with a semiconductor self-adhesive tape and a semiconductor crepe paper. As Figure 2 and Figure 3 shown, an anti-tracking umbrella skirt 13 is provided above the body 17 of the zero-sequence voltage transformer. A second conducting rod 12 is embedded in the center of the anti-tracking umbrella skirt 13 and connected to the primary coil of the zero-sequence voltage transformer. Structures other than the mounting base plate 18 are fixed in a mold at the designed positions and then poured with epoxy resin 4 to form a transformer body. After spraying a metal shield on the outer surface of the transformer body, an insulating paint is sprayed. The lower part of the transformer body is connected to the mounting base plate 18.

[0038] As Figure 1As shown, the high-voltage shielding device includes a front-section high-voltage shielding device 2 and a rear-section high-voltage shielding device 5. There is a gap and no contact between the two end faces on the opposite sides of the front-section high-voltage shielding device 2 and the rear-section high-voltage shielding device 5. The outer surfaces of the high-voltage shielding device are all treated by sandblasting and then sprayed with semiconductor paint. The high-voltage shielding device can shield the irregular high-voltage electric field generated by external factors such as the fuse 7 within the fuse cavity 8. The fuse and its connection components include a fuse 7, a metal nut 1, a metal contact 10, a spring 9, a first conductive rod 11, and a metal connection piece 6. A fuse cavity 8 is horizontally arranged above the main voltage transformer. The front end of the fuse cavity 8 is connected to the metal nut 1, and the rear end of the fuse cavity 8 is installed with the metal contact 10. The metal contact 10 is of an annular structure. There is an external thread on the front side of the metal contact 10 for threaded connection with the rear-section high-voltage shielding device 5, and there is an internal thread on the rear side of the metal contact 10 for screwing connection with the spring 9. The rear end of the metal contact 10 is connected to the first conductive rod 11. The metal connection piece 6 is connected to the body 14 of the main voltage transformer. The first conductive rod 11 is of a special-shaped rod structure. The three are fixed together to form a path at the spatial positions required by the design by welding the two ends of the first conductive rod 11 to the metal contact 10 and the metal connection piece 6 respectively. The fuse 7 is placed within the fuse cavity 8. The rear end of the fuse 7 abuts against the spring 9 and is connected to the body 14 of the voltage transformer through the first conductive rod 11 and the metal connection piece 6. The front end of the fuse 7 is tightly fixed by the metal bolt 24 within the metal nut 1. The metal nut 1 is located inside the TYPE-C external cone 19, and the front end face of the metal nut 1 is flush with the end face of the TYPE-C external cone 19. There is an external thread on the rear side of the metal nut 1 for threaded connection with the front-section high-voltage shielding device 2. A low-voltage shielding device 3 is sleeved outside the front-section high-voltage shielding device 2. The outer surfaces of the metal contact 10 and the metal nut 1 are both coated with semiconductor self-adhesive tape and semiconductor crepe paper.

[0039] As Figures 1 to 4 , the processing method steps of a front-inserted three-phase integrated voltage transformer of a fuse are as follows:

[0040] Step 1: Fix the high-voltage shielding net on the metal nut 1 to form the front-section high-voltage shielding device 2;

[0041] Step 2: Screw the rear-section high-voltage shielding device 5 onto the external thread of the metal contact 10 to form the rear-section high-voltage shielding device 5;

[0042] Step 3: Fix the two sections of high-voltage shielding devices in the mold through a suitable fixture;

[0043] Step 4: Fix 3 bodies 14 of the main voltage transformer and 1 body 17 of the zero-sequence voltage transformer in the mold;

[0044] Step 5: Weld the end of the secondary lead of the voltage transformer to the secondary embedded nut 16 and fix it on the mold;

[0045] Step 6: Connect half of the coils of the three main voltage transformers of the voltage transformer through the metal conducting rod 23 to form the main voltage transformer common terminal 21;

[0046] Step 7: Connect the main voltage transformer common terminal 21 to the primary winding of the zero-sequence voltage transformer through the connecting wire 22;

[0047] Step 8: Fix the first conducting rod 11, the metal connecting piece 6, and the metal contact 10 by welding or riveting;

[0048] Step 9: Connect and fix the metal connecting piece 6 to the primary wire of the other half of the coil of the main voltage transformer;

[0049] Step 10: Pass the low-voltage shielding device 3 through the front-section high-voltage shielding device 2 of the fuse and then fix it on the mold;

[0050] Step 11: Fix one end of the second conducting rod 12 to the primary coil of the zero-sequence voltage transformer, and then fix the other end of the second conducting rod 12 on the mold;

[0051] Step 12: Pour through the epoxy resin 4 to form a casting body with a fuse cavity 8, a TYPE-C external cone 19, an anti-creeper umbrella skirt 13, and a secondary outlet box 15, and then spray metal shielding and protective paint on the outer surface to form the voltage transformer body for standby;

[0052] Step 13: Fix the mounting base plate 18 on the voltage transformer body with screws;

[0053] Step 14: Fix the metal nameplate on the secondary outlet box 15 with screws;

[0054] Step 15: Screw the secondary outlet waterproof joint 20 onto the secondary outlet box 15 to complete the production.

[0055] The user only needs to remove the cable elbow and unscrew the metal bolt to take out the fuse 7 for replacement, without the cumbersome operations such as removing the voltage transformer from the cabinet, which saves time and effort and is extremely convenient.

[0056] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A three-phase integrated voltage transformer with front plug-in fuse, characterized in that: It includes 3 main voltage transformers, 1 zero-sequence voltage transformer, a high-voltage shielding device, a low-voltage shielding device, fuses and their connecting components, a secondary outlet box and a mounting base plate. The common ends of the 3 main voltage transformers are connected together by a metal conductive rod. The common ends of the 3 main voltage transformers are connected to the primary winding on the body of the zero-sequence voltage transformer through a connecting wire. The 3 main voltage transformers are respectively connected to secondary embedding nuts through secondary leads. The secondary embedding nuts are installed in the secondary outlet box. The high-voltage shielding device includes a front-segment high-voltage shielding device and a rear-segment high-voltage shielding device. The fuses and their connecting components include fuses, metal nuts, metal contacts, springs, first conductive rods, and metal connecting pieces. A fuse cavity is horizontally arranged above the main voltage transformer. The front end of the fuse cavity is connected to the metal nut, and the rear end of the fuse cavity is installed with a metal contact. The metal contact is of a ring structure. There is an external thread on the front side of the metal contact for threaded connection with the rear-segment high-voltage shielding device, and an internal thread on the rear side of the metal contact for screwing connection with the spring. The rear end of the metal contact is connected to the first conductive rod. The metal connection piece is connected to the body of the main voltage transformer. The first conductive rod is of a special-shaped rod structure. The two ends of the first conductive rod are respectively welded to the metal contact and the metal connection piece to fix the three together at the spatial positions required by the design requirements. The fuse is placed in the fuse cavity, and the rear end abuts against the spring and is connected to the body of the voltage transformer through the first conductive rod and the metal connection piece. The front end is tightly fixed by a metal bolt in the metal nut. There is an external thread on the rear side of the metal nut for threaded connection with the front-segment high-voltage shielding device. The front-segment high-voltage shielding device is sleeved with a low-voltage shielding device. Other structures except the mounting base plate are fixed in the mold according to the design positions and formed into a transformer body through resin casting. The lower part of the transformer body is connected to the mounting base plate.

2. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, characterized in that: The two end faces on the opposite sides of the front-segment high-voltage shielding device and the rear-segment high-voltage shielding device do not contact.

3. The front-inserted three-phase integrated voltage transformer according to claim 1, wherein: An anti-creeper umbrella skirt is provided at the upper end of the zero-sequence voltage transformer. A second conductive rod is embedded in the center of the anti-creeper umbrella skirt and connected to the primary coil of the zero-sequence voltage transformer.

4. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, wherein: The metal nut is located inside the outer cone of the TYPE-C.

5. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, characterized in that: The outer surface of the metal conductive rod at the common ends of the 3 main voltage transformers is coated with semiconductor self-adhesive tape and semiconductor crimped paper.

6. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, wherein: The outer surface of the transformer body is sprayed with metal shielding and then sprayed with insulating paint.

7. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, wherein: The outer surfaces of the metal contact and the metal nut are both coated with semiconductor self-adhesive tape and semiconductor crimped paper.

8. The front-insert type three-phase integrated voltage transformer according to claim 1, characterized in that: The outer surfaces of the high-voltage shielding devices are all sandblasted and then sprayed with semiconductor paint.

9. The fuse front-inserted three-phase integrated voltage transformer according to claim 1, characterized in that, The processing method steps are as follows: Step 1: Fix the high-voltage shielding net on the metal nut to form the front-segment high-voltage shielding device; Step 2: Screw the rear-segment high-voltage shielding device onto the external thread of the metal contact to form the rear-segment high-voltage shielding device; Step 3: Fix the two segments of high-voltage shielding devices in the mold through a suitable fixture; Step 4: Fix the bodies of 3 main voltage transformers and the body of 1 zero-sequence voltage transformer in the mold; Step 5: Weld the end of the secondary lead of the voltage transformer to the secondary embedding nut and fix it on the mold; Step 6: Connect half of the coils of the three main voltage transformers of the voltage transformer through a metal conducting rod to form the common terminal of the main voltage transformer; Step 7: Connect the common terminal of the main voltage transformer to the primary winding of the zero-sequence voltage transformer through a connecting wire; Step 8: Fix the first conducting rod, metal connecting piece, and metal contact by welding or riveting; Step 9: Connect and fix the metal connecting piece to the primary wire of the other half of the coil of the main voltage transformer; Step 10: Pass the low-voltage shielding device through the front-section high-voltage shielding device of the fuse and fix it on the mold; Step 11: Fix one end of the second conducting rod to the primary coil of the zero-sequence voltage transformer, and then fix the other end of the second conducting rod on the mold; Step 12: Pour with epoxy resin to form a casting body with a fuse cavity, TYPE-C external cone, anti-climbing umbrella skirt, and secondary outlet box, and then spray metal shielding and protective paint on the outer surface to form the voltage transformer body for standby; Step 13: Fix the mounting base plate on the voltage transformer body with screws; Step 14: Fix the metal nameplate on the secondary outlet box with screws; Step 15: Screw the secondary outlet waterproof joint on the secondary outlet box to complete the production.

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