An impedance matching fixture for transmitting high frequency signals to power transformer windings

Abstract

The invention discloses an impedance matching fixture for transmitting high-frequency signals to a power transformer winding, comprising: a coaxial terminal, a signal end of the coaxial terminal connected to a clamping mechanism, and a shielding layer connected to a structural member; a hanging mechanism connected to a grounding wire, providing a hanging interface for connecting a test module; a rotating screw used to drive two clamps of the clamping mechanism to move in the same direction or in the opposite direction; an insulating material filling layer used to disconnect the electrical connection between the clamping mechanism and the shielding layer of the coaxial terminal; the bottom of the clamping mechanism is electrically connected to the signal end of the coaxial terminal, and the bottom of the clamping mechanism is mechanically connected to the rotating screw; a clamp is arranged on the upper part of the clamping mechanism, and the electrode of the transformer bushing to be tested is clamped or loosened under the drive of the rotating screw; an impedance matching mechanism is arranged inside the fixture, a first end of the impedance matching mechanism is connected to the clamping mechanism and the signal end of the coaxial terminal, and a second end of the impedance matching mechanism is connected to the ground potential.

Description

Technical Field

[0001] The present invention relates to the technical field of state sensing of power transmission and transformation equipment, and more specifically, to an impedance matching fixture for transmitting high-frequency signals to a winding of a power transformer. Background Art

[0002] Power transformers are key core equipment of the power system. By the end of 2015, the number of 110kV and above transformers in operation in the State Grid system exceeded 39,000. The equipment installation and use volume is huge, and its operating reliability is directly related to the power supply safety of the power system. However, in recent years, transformer winding deformation failures have occurred frequently, ranking first among transformer failures. From 2006 to 2015, the State Grid system had 81 220kV and above transformer damage failures caused by winding deformation, accounting for 33.8% of all transformer failures. Frequent transformer winding deformation failures have led to great concerns about equipment reliability, especially as the scale of the power system becomes larger and larger, the capacity becomes higher and higher, and the system short-circuit current level increases year by year, the hidden dangers of transformer winding deformation failures are more prominent. After the system is short-circuited, how to quickly and effectively detect whether the transformer winding is deformed and avoid transformer failure and damage has become a key issue of concern to the operation and maintenance unit and needs to be solved urgently.

[0003] The frequency response method is currently recognized as the most effective technical means to detect winding deformation, and has achieved good application results in offline detection of transformer winding deformation. One of the problems in the actual application of the frequency response method winding deformation detection device is that the signal transmission path between the detection host and the corresponding bushing of the transformer winding under test is a mixed mode of coaxial line and single-ended line, and the signal attenuation and distortion are relatively serious, which has an adverse effect on the detection results. Summary of the invention

[0004] The technical solution of the present invention provides an impedance matching device for transmitting high-frequency signals to a power transformer winding, so as to solve the problem of how to improve the accuracy of transformer winding deformation detection.

[0005] In order to solve the above problems, the present invention provides an impedance matching fixture for transmitting high-frequency signals to a power transformer winding, the fixture comprising:

[0006] A coaxial terminal, wherein a signal end of the coaxial terminal is connected to a clamping mechanism, a shielding layer of the coaxial terminal is connected to a structural member, and the structural member is at ground potential;

[0007] A hanging mechanism, the hanging mechanism is connected to the ground wire and is used to provide a hanging interface for connecting the test module;

[0008] A rotating screw, the rotating screw is used to drive the two clamping pieces of the clamping mechanism to move in the same direction or in opposite directions;

[0009] An insulating material filling layer, used to disconnect the electrical connection between the clamping mechanism and the shielding layer of the coaxial terminal, the clamping mechanism on a first side of the insulating material filling layer is connected to the signal end of the coaxial terminal, and the clamping mechanism on a second side of the insulating material filling layer is connected to the shielding layer of the coaxial terminal;

[0010] The bottom of the clamping mechanism is electrically connected to the signal end of the coaxial terminal, and the bottom of the clamping mechanism is mechanically connected to the rotating screw. A clamping piece is arranged on the upper part of the clamping mechanism, and clamps or loosens the bushing electrode of the transformer under test under the drive of the rotating screw.

[0011] The impedance matching mechanism is arranged inside the clamp, a first end of the impedance matching mechanism is connected to the clamping mechanism and the signal end of the coaxial terminal, and a second end of the impedance matching mechanism is connected to the ground potential.

[0012] Preferably, the coaxial terminal is N-type.

[0013] Preferably, the hanging mechanisms are multiple groups.

[0014] Preferably, the maximum one-way stroke of the rotating screw is 55 mm, driving the two clamping pieces of the clamping mechanism to achieve an opening distance of 0 to 110 mm.

[0015] Preferably, the insulating material filling layer is a cross-linked polyethylene filling layer, and the relative dielectric constant ε r =2.3~2.4.

[0016] Preferably, the impedance matching mechanism is 50 ohm impedance.

[0017] The device of the technical solution of the present invention is fastened to the bushing electrode where the transformer winding under test is located, and the wiring is completed according to the test requirements of the frequency response method transformer winding deformation detection device, so as to realize the coaxial mode propagation of the signal on the complete transmission path from the detection host to the measured winding bushing, and reduce the attenuation distortion during the signal transmission process. In addition, if there is a test module that needs to be connected to the transformer bushing nearby (such as a transformer winding deformation detection module for wireless communication), it can also be connected to the measured bushing nearby by hanging it on the fixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0019] Figure 1 A schematic diagram of an impedance matching fixture for transmitting high-frequency signals to a power transformer winding according to a preferred embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a transmission line in a coaxial and single-ended mixed mode according to a preferred embodiment of the present invention;

[0021] Figure 3 A schematic diagram of an impedance matching method of a clamp according to a preferred embodiment of the present invention;

[0022] Figure 4 A schematic diagram of the inventive effect of a clamp according to a preferred embodiment of the present invention;

[0023] Figure 5 An implementation example of a clamp according to a preferred embodiment of the present invention; and

[0024] Figure 6 Schematic diagram of the transformer winding amplitude-frequency curve according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0025] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0026] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0027] Figure 1 The figure is a schematic diagram of an impedance matching fixture for transmitting high-frequency signals to a power transformer winding according to a preferred embodiment of the present invention. The detection host and the bushing corresponding to the transformer winding under test are connected by a long-distance lead. Since the signal output end of the detection host is a coaxial structure, and the signal transmission mode of the transformer bushing is a single-ended structure, the connection between the detection host and the bushing corresponding to the winding under test adopts a mixed mode of coaxial transmission line and single-ended transmission line, as shown in the attached figure. Figure 1As shown. According to the transmission line theory, high-frequency excitation signals and response signals are prone to attenuation and distortion when propagating in a single-ended transmission line, and are easily affected by external interference signals. In addition, the single-ended transmission structure destroys the impedance matching structure of the coaxial transmission line, and the standing wave ratio of the high-frequency signal transmission is significantly increased, resulting in serious signal distortion. In summary, the signal transmission method used in the existing frequency response method transformer winding deformation detection device is unreasonable, resulting in low detection accuracy and consistency. In order to solve the above problems, the present invention provides a clamping structure (hereinafter referred to as a clamp) with an impedance matching function, which can separate the signal end and the shielding layer of the coaxial signal terminal through a 50Ω impedance matching circuit, and is fixed on the sleeve electrode through a clamping mechanism, so that the signal end of the coaxial signal terminal is connected to the sleeve electrode, and the shielding layer of the coaxial signal terminal is connected to the ground potential. Through this clamp structure, the full-path coaxial line connection between the winding deformation detection host and the corresponding sleeve of the transformer winding under test can be achieved, thereby improving the signal measurement accuracy and consistency.

[0028] like Figure 1 As shown, the present invention provides an impedance matching fixture for transmitting high-frequency signals to the windings of a power transformer. The embodiments of the present invention include key structures such as a coaxial terminal, a hanging mechanism, a rotating screw, a cross-linked polyethylene filling layer, a clamping mechanism, an impedance matching mechanism, and an impedance matching mechanism.

[0029] A coaxial terminal, a signal end of the coaxial terminal is connected to the clamping mechanism, a shielding layer of the coaxial terminal is connected to a structural member, and the structural member is at ground potential. Preferably, the coaxial terminal is N-type.

[0030] The coaxial terminal of the present invention can use an N-type coaxial terminal, which is installed on an aluminum structure. The signal end of the coaxial terminal is connected to the clamping mechanism, the shielding layer of the coaxial terminal is connected to the aluminum structure, and the aluminum structure is at ground potential as a whole.

[0031] The hanging mechanism is connected to the ground wire and is used to provide a hanging interface for connecting the test module. Preferably, the hanging mechanism is in multiple groups.

[0032] The present invention can have multiple sets of hanging mechanisms, and three sets are used as an example for illustration. The present invention has three sets of hanging mechanisms, which are connected to the ground wire through the through-hole structure and can also serve as hanging interfaces for other test modules to achieve the nearest connection between the test module and the transformer winding under test.

[0033] The rotating screw is used to drive the two clamping pieces of the clamping mechanism to move in the same direction or in the opposite direction. Preferably, the maximum one-way stroke of the rotating screw is 55 mm, and the two clamping pieces of the clamping mechanism are driven to achieve an opening distance of 0 to 110 mm.

[0034] The rotary screw of the present invention is used to drive the two clamping pieces of the clamping mechanism to move in the same direction or in the opposite direction to achieve separation or clamping of the clamping pieces. The screw has a one-way stroke of 55 mm and can drive the clamping pieces to achieve an opening distance of 0 to 110 mm.

[0035] The insulating material filling layer is used to disconnect the electrical connection between the clamping mechanism and the shielding layer of the coaxial terminal. The clamping mechanism on the first side of the insulating material filling layer is connected to the signal end of the coaxial terminal, and the clamping mechanism on the second side of the insulating material filling layer is connected to the shielding layer of the coaxial terminal. Preferably, the insulating material filling layer is a cross-linked polyethylene filling layer, and the relative dielectric constant ε of the cross-linked polyethylene filling layer is r =2.3~2.4.

[0036] The insulating material filling layer of the present invention is a cross-linked polyethylene filling layer, which is used to disconnect the electrical connection between the clamping mechanism and the aluminum structure where the coaxial terminal shielding layer is located. The clamping mechanism on the left side of the filling layer is connected to the signal end of the coaxial terminal, and the aluminum structure on the right side of the filling layer is connected to the shielding layer of the coaxial terminal. r = Cross-linked polyethylene material with a value of 2.3 to 2.4.

[0037] The bottom of the clamping mechanism is electrically connected to the signal end of the coaxial terminal, and the bottom of the clamping mechanism is mechanically connected to the rotating screw. A clamping piece is arranged on the upper part of the clamping mechanism, and the bushing electrode of the transformer to be tested is clamped or loosened under the drive of the rotating screw.

[0038] The bottom of the clamping mechanism of the present invention is reliably electrically connected to the signal end of the coaxial terminal and reliably mechanically connected to the rotating screw. It moves under the drive of the rotating screw. The upper part is composed of two aluminum clips with arc-shaped mechanisms, which can clamp or loosen the bushing electrode of the transformer under test under the drive of the rotating screw. When the bushing electrode is clamped, the electrical connection between the signal end of the coaxial terminal and the bushing electrode can be achieved. At the same time, the clamp can be fixed on the bushing electrode as a whole through the mechanical clamping force, providing a reliable electrical connection point for the connection between the signal line and the ground line and the winding under test during detection.

[0039] The impedance matching mechanism is arranged inside the clamp, the first end of the impedance matching mechanism is connected to the clamping mechanism and the signal end of the coaxial terminal, and the second end of the impedance matching mechanism is connected to the ground potential. Preferably, the impedance matching mechanism is a 50 ohm impedance.

[0040] The impedance matching mechanism of the present invention is built into the fixture and is a two-port network for 50 ohm impedance matching of the high-frequency signal transmission path, one end of which is connected to the clamping mechanism and the signal end of the coaxial terminal, and the other end is connected to the ground potential. After 50Ω impedance matching, the standing wave ratio caused by transmission impedance mismatch when the high-frequency signal is converted from the coaxial transmission mode to the single-ended transmission mode is reduced.

[0041] The schematic diagram of the application of the present invention in the frequency response method transformer winding deformation detection is shown in the attached figure. Figure 4 As shown. The fixture designed in the present invention is fastened and installed on the bushing electrode where the transformer winding to be tested is located, and the wiring is completed according to the test requirements of the frequency response method transformer winding deformation detection device, so that the coaxial mode propagation of the signal on the complete transmission path from the detection host to the measured winding bushing can be achieved, and the attenuation distortion during the signal transmission process can be reduced. In addition, if there is a test module that needs to be connected to the transformer bushing nearby (such as a transformer winding deformation detection module for wireless communication), it can also be connected to the measured bushing nearby by hanging it on the fixture.

[0042] The implementation method of the present invention uses the AX winding of a certain isolation transformer as the test object, installs a fixture on the AX winding bushing, connects to the frequency response method transformer winding deformation detection host, and completes the test wiring and detection according to the DL / T911-2014 "Frequency Response Analysis Method for Power Transformer Winding Deformation" standard. The detection host and the fixture installed on the bushing are connected by a coaxial cable. Through this connection method, the measurement end of the detection host is connected to the winding under test after the fixture is switched and impedance matched. The detection photos are attached. Figure 5 The amplitude-frequency characteristic curve of the measured winding is shown in the attached figure. Figure 6 shown.

[0043] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0044] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / said / the [means, components, etc.]" are to be openly interpreted as at least one instance of the means, components, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. An impedance matching fixture for transmitting high-frequency signals to a power transformer winding, the fixture comprising: A coaxial terminal, wherein a signal end of the coaxial terminal is connected to a clamping mechanism, a shielding layer of the coaxial terminal is connected to a structural member, and the structural member is at ground potential; A hanging mechanism, the hanging mechanism is connected to the ground wire and is used to provide a hanging interface for connecting the test module; A rotating screw, the rotating screw is used to drive the two clamping pieces of the clamping mechanism to move in the same direction or in opposite directions; An insulating material filling layer, used to disconnect the electrical connection between the clamping mechanism and the shielding layer of the coaxial terminal, the clamping mechanism on a first side of the insulating material filling layer is connected to the signal end of the coaxial terminal, and the clamping mechanism on a second side of the insulating material filling layer is connected to the shielding layer of the coaxial terminal; The bottom of the clamping mechanism is electrically connected to the signal end of the coaxial terminal, and the bottom of the clamping mechanism is mechanically connected to the rotating screw. A clamping piece is arranged on the upper part of the clamping mechanism, and clamps or loosens the bushing electrode of the transformer under test under the drive of the rotating screw. The impedance matching mechanism is arranged inside the clamp, a first end of the impedance matching mechanism is connected to the clamping mechanism and the signal end of the coaxial terminal, and a second end of the impedance matching mechanism is connected to the ground potential. 2 . The clamp according to claim 1 , wherein the coaxial terminal is of N type.

3. The clamp according to claim 1, wherein the hanging mechanism is a plurality of groups.

4. According to the clamp of claim 1, the maximum one-way stroke of the rotating screw is 55 mm, driving the two clamping pieces of the clamping mechanism to achieve an opening distance of 0 to 110 mm.

5. The fixture according to claim 1, wherein the insulating material filling layer is a cross-linked polyethylene filling layer, and the relative dielectric constant ε r =2.3~2.

4. The fixture according to claim 1 , wherein the impedance matching mechanism is a 50 ohm impedance.

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