Low-voltage side grading ring for field partial discharge test of extra-high voltage transformer

Abstract

The utility model discloses a low-voltage side grading ring for an extra-high voltage transformer on-site partial discharge test, which comprises an outer grading cover, the outer grading cover is an annular shell, a fixed connecting bar is arranged in the annular shell, two sides of the lower end of the fixed connecting bar are fixedly connected with the annular shell through two symmetrical lower support connecting rods respectively, and the lower support connecting rods are fixedly connected with the outer grading cover. The two sides of the upper end of the fixed connection row are fixedly connected with the annular shell through four upper supporting connection rods which are symmetrical in pairs. The fixed connection bar is fixed with a wiring terminal at the top end of the extra-high voltage transformer bushing through a bolt; the outer voltage-sharing cover is provided with an anti-corona wire installation hand hole, and an electric lead of the anti-corona wire passes through the anti-corona wire installation hand hole and is fixedly connected with the wiring terminal. The grading ring provided by the utility model can be reliably fixed at the top end of the sleeve, meets the requirement of stably connecting an anti-corona wire at the position of a wiring terminal of the sleeve, and is simple and reliable in structure and convenient to operate.

Description

Technical Field

[0001] The utility model relates to the technical field of high-voltage electrical appliance accessories, in particular to a low-voltage side grading ring used for on-site partial discharge testing of ultra-high voltage transformers. Background Art

[0002] The statements herein merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Transformers are important equipment for transmitting and converting electric energy in power systems. Before a new or expanded transformer is put into operation, a long-term induction withstand voltage partial discharge test needs to be carried out to detect whether the transformer winding and insulation quality meet the use requirements and ensure the normal operation of the equipment. The partial discharge measurement test is carried out for no less than 1 hour under the condition of voltage (Ur is the rated voltage of the winding). In order to ensure the scientific and accurate results of the partial discharge test, the background noise needs to be eliminated as much as possible on site, that is, the background value of the partial discharge should be kept as low as possible. At the same time, during the test, the test equipment itself, the anti-corona wire for the test, the test grading ring, etc. should be prevented from generating partial discharge, which will cause interference to the partial discharge signal and affect the judgment of the partial discharge results. Therefore, it is particularly important to control the overall partial discharge background of the test circuit.

[0004] At present, the test principle of partial discharge of UHV transformer is as follows: Figure 1 As shown, a variable frequency power supply with adjustable frequency is used to supply power to the low voltage side of the excitation transformer SB. The high voltage side of the excitation transformer SB outputs a high voltage to the compensation reactor L and the low voltage side of the tested transformer. The compensation reactor L is used to compensate for the reactive power of the tested transformer during operation. In addition, Cf is a capacitive voltage divider, Co is the bushing capacitance, and Zm is the detection impedance.

[0005] At present, the grading rings on the low-voltage side (110kV) used for partial discharge tests of UHV main transformers all use the grading rings used for ordinary 110kV transformers. The grading rings are hollow in the middle. During installation, they are put from the top of the high-voltage bushing down onto the terminal at the top of the bushing. During this process, the terminal originally installed on the top of the bushing needs to be removed, which is a large workload, difficult to work at heights, and poses a great safety hazard. The above-mentioned traditional grading ring structure is not suitable for the actual needs of the low-voltage side of the UHV main transformer, which is mainly reflected in the following two aspects: First, since the partial discharge test of the UHV main transformer needs to be pressurized on the low-voltage side, the pressurized lead uses a special 150mm diameter anti-corona wire. The grading ring needs to be able to firmly connect the anti-corona wire to the terminal at the top of the bushing, and the end of the anti-corona wire needs to be inserted into the grading ring to avoid local discharge. However, the current traditional grading rings are mainly bell-shaped structures or double-layer annular cylinder structures. When the grading ring is connected to the anti-corona wire, it mainly relies on the inner conductor of the anti-corona wire. After the wire is connected to the bushing terminal, it is tightened. The wire mouth of the anti-corona wire cannot be inserted into the equalizing ring. The end of the anti-corona wire and the outer side of the equalizing ring are tightened by tension, which is easy to loosen. Therefore, the current traditional equalizing ring structure does not meet the actual test use requirements; second, the equalizing ring with a bell-shaped structure or a double-layer annular cylinder structure is pressed on the bushing by its own gravity, and there is no reliable connection structure between the equalizing ring and the terminal. In the work site with strong wind, the anti-corona wire will swing due to the wind, and the equalizing ring will also shake. During the shaking, abnormal partial discharge signals will be generated due to poor contact. That is, in order to maintain a good partial discharge background, it is necessary to ensure that the equalizing ring, anti-corona wire, and terminal are firmly connected to each other during the entire test process, but the current traditional equalizing ring does not meet the above use requirements. Utility Model Content

[0006] In view of the above-mentioned problems and defects existing in the prior art, the utility model provides a low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers, which solves the problem that the lead wires and the grading ring at the end of the low-voltage side bushing are not firmly installed during the partial discharge test of the ultra-high voltage transformer, which easily generates partial discharge interference signals. The grading ring can be reliably fixed on the top of the bushing and meets the requirement of firmly connecting the anti-corona wire at the bushing terminal position. It has a simple and reliable structure and is easy to operate.

[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0008] A low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers comprises an outer grading cover, which is an annular shell. A fixed connection row is arranged inside the annular shell. The two sides of the lower end of the fixed connection row are fixedly connected to the annular shell by two symmetrical lower supporting connecting rods, and the two sides of the upper end of the fixed connection row are fixedly connected to the annular shell by four upper supporting connecting rods that are symmetrical in pairs; the fixed connection row is fixed to the top terminal of the ultra-high voltage transformer bushing by bolts; the outer grading cover is provided with an anti-corona wire installation hand hole, and the anti-corona wire conductive wire passes through the anti-corona wire installation hand hole and is fixedly connected to the terminal.

[0009] Through the above design, the outermost outer voltage-equalizing cover is used to achieve a uniform electric field, and the fixed connecting row is bolted to the wiring terminal at the top of the bushing to achieve conductive and fixing effects. The hand hole for installing the anti-corona wire is designed to facilitate the firm installation of the internal lead of the anti-corona wire and the wiring terminal of the bushing.

[0010] According to a further technical solution, the diameter of the outer pressure equalizing cover is not greater than 1000 mm, and the outer pressure equalizing cover is formed by integrally pressing an aluminum plate with a smooth surface.

[0011] According to a further technical solution, the annular shell has a truncated cone-shaped arcuate side wall, and the upper and lower ends of the side wall are bent inward to form an upper ring and a lower ring respectively.

[0012] According to a further technical solution, the upper ring and the lower ring are concentric, and the diameter of the upper ring is smaller than the diameter of the lower ring.

[0013] A further technical solution is that one end of two symmetrical lower supporting connecting rods is fixedly connected to the lower end of the fixed connecting row, and the other end is fixedly connected to the lower ring edge; one end of four symmetrical upper supporting connecting rods is fixedly connected to the upper end of the fixed connecting row, and the other end is fixedly connected to the upper ring edge.

[0014] The upper and lower supporting connecting rods are arranged to connect and fix the connecting row and the outer pressure equalizing cover, thereby playing a supporting and fixing role.

[0015] According to a further technical solution, the fixed connection row is provided with fixed through holes, and the fixed through holes are long strip-shaped through holes.

[0016] By setting the fixed through holes, the terminals can be flexibly adjusted according to the sizes and positions of different wiring terminals, so as to facilitate the fixed installation of the outer voltage-equalizing cover, the fixed connection row and the sleeve wiring terminals.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] 1. The utility model proposes a low-voltage side grading ring for on-site partial discharge test of ultra-high voltage transformers. The grading ring is fixedly connected to an outer grading cover and a fixed connecting row through a plurality of supporting connecting rods, and the fixed connecting row is fixed to the bushing terminal bolts. The anti-corona wire is inserted into the grading ring through the installation hand hole on the outer grading cover and fixedly connected to the bushing terminal. The installation demand of the anti-corona wire for partial discharge test of ultra-high voltage main transformer is met, and the grading ring, the anti-corona wire and the bushing top terminal are firmly connected, thereby effectively ensuring the partial discharge effect.

[0019] 2. The voltage-equalizing ring proposed by the utility model is easy to install and has a simple and reliable structure. It can be firmly installed without removing the terminal at the end of the bushing. It can avoid the shaking caused by external influences such as wind in the traditional voltage-equalizing ring test to generate interference signals, and has high reliability in suppressing partial discharge background. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0021] Figure 1 It is a wiring diagram of a partial discharge test of a main transformer in the prior art;

[0022] Figure 2 It is a structural side view of a low-voltage side grading ring used for on-site partial discharge testing of ultra-high voltage transformers according to the utility model;

[0023] Figure 3 It is a cross-sectional schematic diagram of a low-voltage side grading ring for on-site partial discharge testing of an ultra-high voltage transformer according to the utility model;

[0024] Figure 4 It is a structural top view of a low-voltage side grading ring for on-site partial discharge testing of an ultra-high voltage transformer according to the utility model.

[0025] Among them, 1. External pressure-equalizing cover; 2. Upper supporting connecting rod; 3. Lower supporting connecting rod; 4. Fixed connecting row; 5. Fixed through hole; 6. Hand hole for installing anti-corona wire. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] like Figure 2 , Figure 3 and Figure 4 As shown, the utility model discloses a low-voltage side grading ring for on-site partial discharge test of ultra-high voltage transformer, comprising an outer grading cover 1, which is an annular shell, and a fixed connection row 4 is arranged inside the annular shell, and the two sides of the lower end of the fixed connection row 4 are fixedly connected to the annular shell by two symmetrical lower supporting connecting rods 3, and the two sides of the upper end of the fixed connection row 4 are fixedly connected to the annular shell by four upper supporting connecting rods 2 which are symmetrical in pairs; the fixed connection row 4 is fixed to the top terminal of the ultra-high voltage transformer bushing by bolts, and an anti-corona wire installation hand hole 6 is provided on the outer grading cover 1, and the anti-corona wire conductive wire (abbreviated as anti-corona wire) passes through the anti-corona wire installation hand hole 6 and is fixedly connected to the terminal.

[0029] Furthermore, the outer pressure equalizing cover 1 is formed by pressing a smooth aluminum plate in one piece, and the outermost outer pressure equalizing cover 1 is used to achieve a uniform electric field. In addition, considering that the oversized pressure equalizing ring is likely to affect the safety distance from other surrounding equipment, the diameter of the outer pressure equalizing cover 1 is preferably not greater than 1000 mm in this embodiment.

[0030] Furthermore, the annular shell has a truncated cone-shaped side wall, and the upper and lower ends of the side wall are bent inward to form an upper ring and a lower ring respectively. By designing the side wall to bend inward, the curvature of the outer side of the equalizing ring is guaranteed to be uniform, without sharp corners and burrs, so as to avoid the problems of tip discharge and corona discharge. In addition, the upper ring and the lower ring are of the same body structure, the upper and lower rings are concentric, and the diameter of the upper ring is smaller than the diameter of the lower ring. The design of the annular shell can ensure the equalizing effect and facilitate installation. One end of the two symmetrical lower supporting links is fixedly connected to the lower end of the fixed connection row, and the other end is fixedly connected to the edge of the lower ring. One end of the four symmetrical upper supporting links is fixedly connected to the upper end of the fixed connection row, and the other end is fixedly connected to the edge of the upper ring; preferably, the fixed connection is welded. By setting the upper and lower supporting rods, the outer voltage-equalizing cover and the fixed connection row inside it are fixedly connected to play a supporting and fixing role; on this basis, the fixed connection row is bolted to the top terminal of the casing to play a conductive and fixing role, and the anti-corona wire installation hand hole is designed to facilitate the firm installation of the internal lead of the anti-corona wire and the casing terminal. Through the above design, the voltage-equalizing ring, the anti-corona wire and the casing top terminal are firmly connected to ensure the partial discharge effect.

[0031] Furthermore, the fixed connection row 4 is provided with a fixed through hole 5, which is a long strip-shaped through hole. By providing the fixed through hole and adopting the bolt connection method, the connection between the fixed connection row and the terminal can be flexibly adjusted according to the size and position of different terminals, so as to facilitate the fixed installation of the outer voltage equalizing cover, the fixed connection row and the sleeve terminal.

[0032] The specific working process of the utility model is as follows:

[0033] Step 1: Before use, check the appearance of the pressure equalizing ring to confirm that there is no abnormality in the appearance and that the supporting connecting rods are not broken.

[0034] Step 2: Use a lifting ring to install it on any two symmetrical upper supporting rods, and use a crane to lift the lifting ring to lift the pressure equalizing ring above the casing; or manually lift the pressure equalizing ring to the casing side and slowly place it on the top of the casing.

[0035] Step 3: Hold the voltage-equalizing ring by hand, and use screws and bolts to fasten the voltage-equalizing ring fixing connection row and the wiring terminal at the top of the bushing together.

[0036] Step 4: Insert the test anti-corona wire through the anti-corona wire installation hand hole on the voltage-equalizing ring, firmly tie the conductive wire of the anti-corona wire to the wiring terminal through the installation hand hole, and tighten the anti-corona wire.

[0037] Step 5: Check the fixation of the voltage-equalizing ring, anti-corona wire and terminal block. The installation is complete after confirmation.

[0038] Step 6: After the test, remove the pressure equalizing ring in the reverse order.

[0039] The utility model proposes a low-voltage side grading ring for on-site partial discharge test of ultra-high voltage transformer, which is fixedly connected to an outer grading cover and a fixed connecting row by multiple supporting connecting rods, and is fixed to the bushing terminal by bolts. The anti-corona wire is inserted into the interior of the grading ring through the installation hand hole on the outer grading cover and is fixedly connected to the bushing terminal. The installation requirement of the anti-corona wire for partial discharge test of ultra-high voltage main transformer is met, and the grading ring, the anti-corona wire and the bushing top terminal are firmly connected, thereby effectively ensuring the partial discharge effect.

[0040] Although the above describes the specific implementation methods of the utility model in combination with the accompanying drawings, it is not intended to limit the scope of protection of the utility model. Technical personnel in the relevant field should understand that on the basis of the technical solution of the utility model, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the utility model.

Claims

1. A low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers, characterized in that: It includes an external pressure-equalizing cover, which is an annular shell. A fixed connection row is arranged inside the annular shell. Both sides of the lower end of the fixed connection row are fixedly connected to the annular shell by two symmetrical lower supporting connecting rods, and both sides of the upper end of the fixed connection row are fixedly connected to the annular shell by four symmetrical upper supporting connecting rods; the fixed connection row is fixed to the top terminal of the UHV transformer bushing by bolts; an anti-corona wire installation hand hole is arranged on the external pressure-equalizing cover, and the anti-corona wire conductive wire passes through the anti-corona wire installation hand hole and is fixedly connected to the terminal.

2. The low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers according to claim 1 is characterized in that: The annular shell has a truncated cone-shaped arcuate side wall, and the upper and lower ends of the side wall are bent inward to form an upper ring and a lower ring respectively.

3. The low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers as claimed in claim 2 is characterized in that: The upper ring and the lower ring are concentric, and the diameter of the upper ring is smaller than the diameter of the lower ring.

4. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 2 is characterized in that: One end of the two symmetrical lower supporting link rods is fixedly connected to the lower end of the fixed connection row, and the other end is fixedly connected to the lower ring edge.

5. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 2 is characterized in that: One end of four upper supporting link rods which are symmetrical in pairs is fixedly connected to the upper end of the fixed connection row, and the other end is fixedly connected to the upper ring edge.

6. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 1 is characterized in that: The diameter of the outer pressure equalizing hood is not greater than 1000 mm.

7. The low-voltage side grading ring for on-site partial discharge testing of ultra-high voltage transformers according to claim 1 is characterized in that: The upper and lower supporting connecting rods are fixedly connected to the fixed connecting row and the outer pressure equalizing cover by welding.

8. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 1 is characterized in that: The outer pressure equalizing cover is formed by integrally pressing an aluminum plate with a smooth surface.

9. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 1, characterized in that: The fixed connection row is provided with fixed through holes.

10. The low voltage side grading ring for on-site partial discharge test of UHV transformer according to claim 9, characterized in that: The fixing through hole is a long strip through hole.

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