Lead bushing and converter transformer for split type on-load tap changer

Abstract

The present invention provides a lead bushing and converter transformer for a split-type on-load tap changer. The lead bushing includes: an insulating cast column; a connection plate sleeved on the outer circumference of the insulating cast column; four current-carrying terminals embedded in the insulating cast column, and the four current-carrying terminals are arranged in a circle on the outer circumference of the grounding column, and the two ends of each current-carrying terminal extend to the two sides of the insulating cast column. The present invention uses a grounding column embedded in the insulating cast column, with both ends extending into the transformer main body oil tank and the auxiliary oil tank, respectively connecting the neutral point of the tap selector and the connection terminal corresponding to the neutral point on the switching switch; and uses four current-carrying terminals embedded in the insulating cast column, respectively connected to the current-carrying contacts of the tap selector and the connection terminals corresponding to the corresponding current-carrying contacts on the switching switch, thereby realizing a reliable electrical connection between the switching switch belonging to the two oil tanks and the tap selector.

Description

Technical Field

[0001] The invention relates to the technical field of power transformers, and in particular to a lead bushing for a split on-load tap changer and a converter transformer. Background Art

[0002] On-load tap changers are usually installed inside transformers. They can achieve transformer voltage regulation without power outage by changing the access position of the voltage regulating winding. They are essential and frequently operated core components of power transformers and converter transformers in DC projects. They play an irreplaceable role in maintaining voltage stability, optimizing power flow distribution, and flexible and economical operation of power systems. Especially for UHV DC transmission projects, converter transformer on-load tap changers are key components necessary to achieve flexible power regulation and efficient and economical operation of DC transmission.

[0003] On-load tap-changers are classified into two typical structures: composite type and combined type. The combined type has a wider range of applications. Figure 1 and Figure 2 As shown, the combined on-load tap changer 1' is composed of a switch 11' and a tap selector 12', which are connected by a voltage regulating lead 13'. The switch 11' and the tap selector 12' are arranged in an integrated manner and installed inside the main oil tank 2' of the transformer / converter body.

[0004] Conventional on-load tapchangers with integrated switching switch / tap selector structure, where the on-load tapchanger is located inside the transformer / converter transformer body, have complex operation and maintenance procedures: In conventional integrated layout, both the switching switch and the tap selector are installed inside the transformer / converter transformer body. Once the switching switch has mechanical or electrical defects, the transformer / converter transformer needs to be shut down for maintenance when replacing the on-load tapchanger. In particular, if there is a problem with the switching switch oil chamber, the transformer / converter transformer oil tank needs to be disassembled and the cover needs to be lifted before the switching switch oil chamber can be replaced. Due to the extremely high requirements for process and environment for on-site disassembly and lifting of the cover, it is basically impossible to carry out on-site. Summary of the invention

[0005] In view of this, the present invention proposes a lead bushing and a converter transformer for a split on-load tap changer, aiming to solve the problem that the existing switching switch and tap selector adopt an integrated structure, which makes the operation and maintenance process complicated.

[0006] On the one hand, the present invention provides a lead bushing for a split-type on-load tap changer, the lead bushing comprising: an insulating cast column, which plays an insulating protection role; a connecting plate, which is sleeved on the outer periphery of the insulating cast column and is used to be connected to an isolation plate between a transformer main body oil tank of a converter transformer and an auxiliary oil tank where a switch is located; a grounding column, which is embedded in the insulating cast column, and the two ends of the grounding column extend to the two sides of the insulating cast column, respectively, and are used to extend into the transformer main body oil tank and the auxiliary oil tank, respectively, so as to respectively connect the neutral point of the tap selector and the upper and lower ends of the switch. A connecting terminal corresponding to the neutral point; four current-carrying terminals are embedded in the insulating cast column, and the four current-carrying terminals are arranged in a circle on the outer circumference of the grounding column, and the two ends of each current-carrying terminal respectively extend to the two sides of the insulating cast column, and are used to extend into the transformer main body oil tank and the auxiliary oil tank respectively, so as to be connected to the current-carrying contacts of the odd and even layers of the tap selector respectively, and the two ends of each current-carrying terminal are used to be connected to the current-carrying contacts of the odd and even layers of the tap selector and the connecting terminals corresponding to the corresponding current-carrying contacts on the switching switch.

[0007] Furthermore, in the above-mentioned split-type on-load tap changer lead bushing, each of the current-carrying terminals is provided with a current transformer, and each of the current transformers is embedded in the insulating cast column. The current transformer is used to collect the load current in real time during the gear switching process of the split-type on-load tap changer to monitor the load current changes during the switching process of the split-type on-load tap changer.

[0008] Furthermore, in the above-mentioned lead bushing for the split on-load tap changer, the current transformer is connected to a controller, which is used to receive the load current collected by the current transformer during the gear switching process of the split on-load tap changer, so as to obtain the odd-numbered current waveform signals and the even-numbered current waveform signals of the A phase and the B phase of the split on-load tap changer, and according to the odd-numbered current waveform signals and the even-numbered current waveform signals of the A phase and the B phase of the split on-load tap changer, based on the switching fault criterion, independently and integratedly judge each current waveform signal, so as to judge whether there is any abnormality in the switching of the split on-load tap changer.

[0009] Further, the lead bushing for the split on-load tap changer described above, based on the switching fault criterion, performs independent and integrated judgments on each current waveform signal, including: if the current waveform signal of at least one gear satisfies the switching circulation time sub-criterion after integration, or the current waveform signal of at least one gear satisfies the waveform discontinuity sub-criterion, or the current waveform signal of at least one gear satisfies the waveform switching discontinuity sub-criterion after integration, or the current waveform signal of at least one gear satisfies the waveform parameter abnormality sub-criterion, then it is determined that there is an abnormality in the switching of the split on-load tap changer.

[0010] Furthermore, in the lead bushing for the split on-load tap changer, the waveform discontinuity sub-criterion includes: if there is a discontinuity in the current waveform signal of at least one gear in the split on-load tap changer, it is determined that there is an abnormality in the switching of the split on-load tap changer.

[0011] Furthermore, for the above-mentioned lead sleeve for the split on-load tap changer, if the switching circulation time of the split on-load tap changer is greater than a preset time value, it is determined that the switching of the split on-load tap changer is abnormal; wherein the preset time value is 15-18 ms, and the switching circulation time of the split on-load tap changer is the time interval during which current flows through the odd-numbered gear positions and the even-numbered gear positions simultaneously during the switching process of the split on-load tap changer.

[0012] Further, in the lead bushing for the split on-load tap changer, the waveform switching discontinuity sub-criteria include: if the split on-load tap changer switches between the odd-numbered current waveform signal of phase A and the even-numbered current waveform signal of phase A, the odd-numbered current waveform signal of phase A and the even-numbered current waveform signal of phase A are integrated, and if there is a waveform discontinuity at the switching point, it is determined that the switching of the split on-load tap changer is abnormal; if the split on-load tap changer switches between the odd-numbered current waveform signal of phase B and the even-numbered current waveform signal of phase B, the odd-numbered current waveform signal of phase B and the even-numbered current waveform signal of phase B are integrated, and if there is a waveform discontinuity at the switching point, it is determined that the switching of the split on-load tap changer is abnormal.

[0013] Further, in the lead bushing for the split-type on-load tap changer, the waveform parameter abnormal sub-criterion includes: if the current waveform signal of at least one gear position in the split-type on-load tap changer satisfies the following formula, it is determined that the switching of the split-type on-load tap changer is normal; otherwise, it is determined that the switching of the split-type on-load tap changer is abnormal;

[0014] ;

[0015] Where i(t) is the actual switching current of the A-phase or B-phase of the split-type on-load tap-changer in odd or even gears, in kA; i 0 (t) is the theoretical switching current of the A-phase or B-phase odd-numbered or even-numbered gear of the split-type on-load tap-changer, in kA; t 1 is a certain moment in the switching process of the split on-load tap changer, in ms; Δt is the time interval for selecting continuous current from a certain moment in the switching process of the split on-load tap changer, in ms.

[0016] Furthermore, in the lead bushing for the split-type on-load tap changer, the insulating casting column is cast by epoxy resin, and the lead bushing is cast in one piece.

[0017] Furthermore, in the above-mentioned lead bushing for the split-type on-load tap changer, the connecting plate is a flange plate structure.

[0018] On the other hand, the present invention further provides a converter transformer provided with the above-mentioned lead bushing for the split-type on-load tap changer.

[0019] Furthermore, the above-mentioned converter transformer also includes: a transformer main body oil tank, the tap selector of the split on-load tap changer is arranged on the top of the transformer main body oil tank; an auxiliary oil tank, which is arranged on one side of the top of the transformer main body oil tank and is arranged at a position close to the tap selector, the switching switch of the split on-load tap changer is arranged inside the auxiliary oil tank, and the lead sleeve for the split on-load tap changer is arranged on the isolation plate between the transformer main body oil tank and the auxiliary oil tank.

[0020] The lead bushing and converter transformer for the split on-load tap changer provided by the present invention realize spatial isolation between the transformer main body oil tank and the auxiliary oil tank by means of an insulating cast column and an isolation plate. The oil circuit is cut off by the oil tank connecting wall and the lead bushing, thereby realizing spatial isolation between the switching switch part and the main oil tank, reducing the degree of influence of the destructive force of the arc fault of the switching switch on the main oil tank. Once a fault occurs, the entire switch does not need to be disassembled, thereby reducing the maintenance cost. The grounding column embedded in the insulating cast column has two ends extending into the transformer main body oil tank and the auxiliary oil tank, respectively connecting the neutral point of the tap selector and the switching switch. The connecting terminal corresponding to the neutral point is connected to the tap selector through four current-carrying terminals embedded in the insulating cast column, which are respectively connected to the current-carrying contacts of the tap selector and the connecting terminals corresponding to the corresponding current-carrying contacts on the switching switch, so as to realize the corresponding connection of the A and B phases of the odd and even gears of the tap selector, and then realize the connection between the tap selector and the switching switch which are respectively arranged in the transformer body oil tank and the auxiliary oil tank, realize the electrical reliable connection between the switching switch and the tap selector, ensure the reliability of current carrying, and solve the problem that the existing switching switch and tap selector adopt an integrated structure so as to complicate the operation and maintenance process.

[0021] Furthermore, the integrated built-in current transformer inside the lead bushing can collect the load current changes of each gear switching of the tap changer in real time, and remotely monitor, diagnose faults and perform preventive maintenance on the operating status of the transformer and split-type on-load tap changer, thereby improving the sensitivity and reliability of electrical protection action.

[0022] Preferably, the lead bushing is integrally cast, which has the advantages of flame retardancy, fire resistance, explosion resistance, etc., and will not produce splashes when punctured, playing an important role in ensuring the safe operation of oil-immersed transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0024] Figure 1 This is a schematic diagram of a conventional integrated structure switching switch in the prior art located inside the main body oil tank;

[0025] Figure 2 It is a structural schematic diagram of a conventional on-load tap changer with an integrated structure of a diverter switch / tap selector in the prior art;

[0026] Figure 3 A schematic diagram of a structure in which a switching switch in a split on-load tap changer in a converter transformer provided by an embodiment of the present invention is located outside the transformer body oil tank;

[0027] Figure 4 A schematic structural diagram of a split on-load tap changer in a converter transformer provided by an embodiment of the present invention;

[0028] Figure 5 A structural schematic diagram of the relative positions between a lead bushing for a split on-load tap changer and a converter transformer provided in an embodiment of the present invention;

[0029] Figure 6 A schematic structural diagram of a lead bushing for a split on-load tap changer provided in an embodiment of the present invention;

[0030] Figure 7 A schematic diagram of the structure of an integrally cast lead bushing for a split-type on-load tap-changer provided by an embodiment of the present invention;

[0031] Figure 8 A wiring diagram corresponding to the first terminal in the current transformer in the lead bushing for the split on-load tap changer provided in an embodiment of the present invention;

[0032] Fig. 9 A wiring diagram corresponding to the second terminal in the current transformer in the lead bushing for the split on-load tap changer provided in an embodiment of the present invention;

[0033] Fig.10 A wiring diagram corresponding to the third terminal in the current transformer in the lead bushing for the split-type on-load tap changer provided in an embodiment of the present invention;

[0034] Fig.11 A wiring diagram corresponding to the fourth terminal in the current transformer in the lead bushing for the split-type on-load tap changer provided in an embodiment of the present invention;

[0035] Fig.12 A waveform diagram of a Y / D connection commutation transformer on-load tap changer provided in an embodiment of the present invention switching a normal load from an odd-numbered gear to an even-numbered gear;

[0036] Fig.13 A waveform diagram of a normal load waveform of a Y / D connection commutation transformer on-load tap changer switching from an even-numbered gear to an odd-numbered gear provided by an embodiment of the present invention;

[0037] Fig.14 Another waveform diagram of the waveform of the Y / Y connection commutation transformer on-load tap changer switching from odd-numbered gears to even-numbered gears when the normal load is switched;

[0038] Fig.15 Another waveform diagram of the waveform of the Y / Y connection commutation transformer on-load tap changer switching from the even-numbered gear to the odd-numbered gear in normal load provided by the embodiment of the present invention;

[0039] Description of reference numerals:

[0040] 1-split on-load tap changer, 11-tap selector, 12-changeover switch, 2-transformer body oil tank, 3-auxiliary oil tank, 4-mechanical drive mechanism, 5-isolating plate, 6-lead bushing, 61-insulating casting, 62-connecting plate, 621-connecting hole, 63-grounding column, 64-current-carrying terminal, 65-current transformer. DETAILED DESCRIPTION

[0041] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] See also Figure 3 and Figure 5 , which shows the preferred structure of the converter transformer provided by the embodiment of the present invention. As shown in the figure, the converter transformer comprises: a split-type on-load tap changer 1, a transformer main body oil tank 2 and an auxiliary oil tank 3; wherein,

[0043] The split on-load tap changer 1 is a split structure, which includes: a tap selector 11 and a switch 12 connected to each other. The switch 12 is arranged at the top of the transformer body oil tank 2, and an auxiliary oil tank 3 is arranged on one side of the top of the transformer body oil tank 2 and near the tap selector 11, and the tap selector 1 is arranged inside the auxiliary oil tank 3. Specifically, the switch 12 of the original on-load tap changer is separated from the transformer body oil tank 2, that is, the tap selector 11 is still placed inside the transformer body oil tank 2, that is, the tap selector 11 and the converter transformer 3 share the transformer body oil tank 2, and the contacts are not energized when the tap selector 11 is in action, which can avoid causing the transformer body oil tank 2 to catch fire. In order to facilitate the later maintenance of the split-type on-load tap changer, preferably, the tap selector 11 is arranged at the top of the transformer body oil tank 2, and the outside of the transformer body oil tank 2 is provided with an auxiliary oil tank 3 at one side of the top and near the tap selector 11, and the tap selector 1 is arranged inside the auxiliary oil tank 3. Further preferably, the auxiliary oil tank 3 is arranged flush with the top cover of the transformer body oil tank 2 to further facilitate the maintenance of the tap selector 1 in the auxiliary oil tank 3, and at the same time, to facilitate the installation and arrangement of the mechanical drive mechanism 4 connected to the tap selector 1 and the transfer switch 2, so that the mechanical drive mechanism 4 can be arranged along the top covers of the tap selector 1 and the transfer switch 2, and can sequentially drive the tap selector 1 and the transfer switch 2 to perform switching actions in sequence.

[0044] A lead bushing 6 for a split on-load tap changer is provided on the isolation plate 5 between the transformer main body oil tank 2 and the auxiliary oil tank 3, which is used to cooperate with the isolation plate 5 to isolate the space between the transformer main body oil tank 2 and the auxiliary oil tank 3, and connect the tap selector 11 and the switching switch 12 to achieve electrical connection between the tap selector 11 and the switching switch 12. Specifically, the isolation plate 5 can be an iron plate structure to achieve spatial isolation between the transformer main body oil tank 2 and the auxiliary oil tank 3; in order to avoid oil leakage at the threading hole caused by threading when the tap selector 11 and the switching switch 12 are connected, the lead bushing 6 is provided on the isolation plate 5, and it can be connected to the isolation plate 5 by bolts and other connectors, so as to ensure the effectiveness of the isolation of the isolation plate 5 through the lead bushing 6 and achieve electrical connection between the tap selectors 11 and the switching switches 12 on both sides. Among them, the setting of the isolation plate 5 and the lead sleeve 6 can realize the isolation between the auxiliary oil tank 3 and the transformer main body oil tank 2, blocking the interconnection of the oil circuit between the auxiliary oil tank 3 and the transformer main body oil tank 2. The switching switch 12 is independently arranged in the auxiliary oil tank 3. Since the auxiliary oil tank 3 is small and has less oil inside, even if the current flowing through the switching switch 12 is abnormal and causes a fire, only the independent oil tank where the switching switch 12 is located will catch fire, which can avoid the transformer main body oil tank 2 from catching fire, thereby improving the safety of the converter transformer 3.

[0045] Continue to see Figures 5 to 7 The lead bushing 6 for the split type on-load tap changer comprises: an insulating cast body 61, a connection plate 62, a grounding column 63 and four current-carrying terminals 64; wherein,

[0046] The insulating cast column 61 plays an insulating and protective role, and the connecting plate 62 is sleeved on the outer periphery of the insulating cast column 61, and is used to connect to the isolation plate 5 between the transformer main body oil tank 2 of the converter transformer and the auxiliary oil tank 3 where the switching switch 12 is located. Specifically, the insulating cast column 61 can be a column structure, which is passed through the isolation plate 5, and the two ends are respectively placed in the transformer main body oil tank 2 and the auxiliary oil tank 3. The insulating cast column 61 is placed on the isolation plate 5, which can not only cooperate with the isolation plate 5 to achieve spatial isolation between the transformer main body oil tank 2 and the auxiliary oil tank 3, but also provide support and insulation. The connecting plate 62 can be fixedly connected to the outer wall of the insulating cast column 61. The connecting plate 62 is an annular plate structure, which is sleeved on the outer periphery of the insulating cast column 61. The connection and fixation between the lead sleeve 6 and the isolation plate 5 can be achieved through the connecting plate 62. Among them, the insulating cast column 61 can be cast with epoxy resin, has good insulation and heat resistance, can withstand high voltage and high temperature environment, can connect different parts of the lead and switch, and ensure current conduction and insulation separation; the connecting plate 62 can be a flange structure, and a number of connecting holes 621 are provided on the connecting plate 62 along its circumference for fixed connection to the isolation plate 5.

[0047] The grounding column 63 is embedded in the insulating casting column 61, and the two ends of the grounding column 63 extend to the two sides of the insulating casting column 61 respectively (such as Figure 6 The grounding column 63 is a grounding column 63, which is used to extend into the transformer main body oil tank 2 and the auxiliary oil tank 3, respectively, to connect the neutral point of the tap selector 11 and the connection terminal corresponding to the neutral point on the switch 12, respectively. Specifically, the grounding column 63 penetrates the insulating casting column 61 along the axial direction of the insulating casting column 61, and the two ends of the grounding column 63 are respectively placed on both sides of the insulating casting column 61, to extend into the transformer main body oil tank 2 and the auxiliary oil tank 3, respectively, and then connect the neutral point of the tap selector 11 and the connection terminal corresponding to the neutral point on the switch 12, respectively. Among them, the grounding column 63 can be coaxially arranged with the insulating casting column 61, so that the lead bushing 6 has a compact structure and reduces its occupied space.

[0048] Four current-carrying terminals 64 are embedded in the insulating cast column 61, and the four current-carrying terminals 64 are arranged in a circle on the outer periphery of the grounding column 63, and the two ends of each current-carrying terminal 64 extend to the two sides of the insulating cast column 61 (such as Figure 6The upper and lower sides shown in the figure are used to extend into the transformer body oil tank 2 and the auxiliary oil tank 3 respectively, so as to be connected to the current-carrying contacts of the odd and even gears of the tap selector 11 respectively, and the two ends of each current-carrying terminal 64 are used to be connected to the current-carrying contacts of the odd and even layers of the tap selector 11 and the connection terminals corresponding to the corresponding current-carrying contacts on the switch 12 respectively. Specifically, the four current-carrying terminals 64 all penetrate the insulating cast column 61 along the axial direction of the insulating cast column 61, and the four current-carrying terminals 64 are arranged in a circumferential manner and evenly on the outer circumference of the grounding column 63, that is, the four current-carrying terminals 64 are evenly and symmetrically arranged on the same circumference, and the circumference of the four current-carrying terminals 64 is coaxially arranged with the grounding column 63, so that the four current-carrying terminals 64 are connected to the corresponding connection terminals respectively, and the compactness of the structure of the lead sleeve is ensured. The four current-carrying terminals 64 are respectively used as the connection terminals of the odd-numbered gears of the A phase, the odd-numbered gears of the B phase, the even-numbered gears of the A phase, and the even-numbered gears of the B phase, so as to respectively realize the connection between the current-carrying contacts corresponding to the odd-numbered gears of the A phase of the tap selector 11 and the connection terminals corresponding to the corresponding current-carrying contacts on the switching switch 12, the connection between the current-carrying contacts corresponding to the odd-numbered gears of the B phase of the tap selector 11 and the connection terminals corresponding to the corresponding current-carrying contacts on the switching switch 12, the connection between the current-carrying contacts corresponding to the even-numbered gears of the A phase of the tap selector 11A and the connection terminals corresponding to the corresponding current-carrying contacts on the switching switch 12, and the connection between the current-carrying contacts corresponding to the even-numbered gears of the B phase of the tap selector 11 and the connection terminals corresponding to the corresponding current-carrying contacts on the switching switch 12, so as to realize the electrical connection between the tap selector 11 and the switching switch 12. Among them, the grounding terminal 63 and the four current-carrying terminals 64 are all used as current-carrying conductors, and can all be independent copper conductors.

[0049] Continue to see Figure 7 In order to collect fault switching current signals in time, preferably, each current-carrying terminal 64 is provided with a current transformer 65, and each current transformer 65 can be embedded in the insulating cast column 61. The current transformer 65 is used to collect the load current in the process of gear switching of the split-type on-load tap changer 1 in real time, so as to monitor the load current changes in the process of switching of the split-type on-load tap changer 1. Specifically, four current transformers 65 are integrated in the lead sleeve 6, which are respectively sleeved on four current-carrying terminals 64. The four current transformers 65 correspond one by one to the four current-carrying terminals 64, and can monitor the load current changes in the process of gear changes of the split-type on-load tap changer 1 in real time. It integrates advanced sensing technology and data transmission modules, which can not only adapt to harsh electrical environments, but also effectively isolate electromagnetic interference between different areas. Among them, the current transformer 65 can be equipped with a secondary current transformer junction box to facilitate the extraction of the collected signal. The wiring diagram of the current transformer 65 can be as shown below. Figures 8 to 11 As shown, in Figures 8 to 11 In the embodiment, the four current-carrying terminals 64 are respectively a first current-carrying terminal, a second current-carrying terminal, a third current-carrying terminal and a fourth current-carrying terminal, namely H1, H2, H3 and H4 respectively.

[0050] It can be seen that by real-time collecting the current of the on-load tap changer switching process through the current transformer 65 embedded in the current-carrying terminal 64, the fault switching current signal can be collected immediately, so that the protection electrical quantity can be effectively operated and the fault can be eliminated.

[0051] In this embodiment, the current transformer 65 may be connected to a controller (not shown in the figure), which is used to receive the load current collected by the current transformer 65 during the gear switching process of the split-type on-load tap changer 1, so as to obtain the odd-numbered gear current waveform signals and the even-numbered gear current waveform signals of the A phase and the B phase of the tap selector 11, and independently and integratedly judge each current waveform signal based on the odd-numbered gear current waveform signals and the even-numbered gear current waveform signals of the A phase and the B phase of the tap selector 11 based on the switching fault judgment criterion, so as to judge whether there is an abnormality in the switching of the split-type on-load tap changer 1. Specifically, during the operation process, the current transformer 65 of the lead bushing 6 can transmit the measured current signal to the controller, so that the controller can analyze and judge the entire action process of the split-type on-load tap changer 1 and the operating state of the transformer according to the obtained current waveform signal, so that the collected current information can be used for remote monitoring, fault diagnosis and preventive maintenance of the operating state of the transformer and the split-type on-load tap changer 1. Among them, the controller can independently and integratedly judge the current waveform signals of each phase based on the odd-numbered current waveform signals and the even-numbered current waveform signals of phase A and phase B of the tap selector 11 based on the switching fault judgment criterion to determine whether there is any abnormality in the switching of the split on-load tap changer.

[0052] It can be seen that according to the current waveform signal obtained by the current transformer 65, based on the switching fault criterion, each current waveform signal is independently and integratedly judged. If the switching fault criterion is met, it is judged that there is an abnormality in the switching of the split-type on-load tap changer, so as to perform fault maintenance. It has the advantages of flame retardancy, fire prevention, explosion prevention, etc., and breakdown will not produce splashes, which plays an important role in ensuring the safe operation of oil-immersed transformers.

[0053] In this embodiment, the current waveform signals of each phase are judged independently and integrated based on the switching fault criterion, including: if the current waveform signal of at least one gear meets the switching circulation time sub-criterion after integration, the current waveform signal of at least one gear meets the waveform switching discontinuity sub-criterion after integration, or the current waveform signal of at least one gear meets the waveform discontinuity sub-criterion, or the current waveform signal of at least one gear meets the waveform parameter abnormality sub-criterion, then it is determined that the switching of the split-type on-load tap changer is abnormal. Specifically, if the odd-numbered gear current waveform signal of phase A of the tap selector 11 and the even-numbered gear current waveform signal of phase A meet the waveform switching discontinuity sub-criterion after integration, or the odd-numbered gear current waveform signal of phase B of the tap selector and the even-numbered gear current waveform signal of phase B meet the waveform switching discontinuity sub-criterion after integration, then it is determined that the switching of the split-type on-load tap changer is abnormal. If at least one of the odd-numbered current waveform signals of phase A, the even-numbered current waveform signals of phase A, the odd-numbered current waveform signals of phase B, and the even-numbered current waveform signals of phase B satisfies the waveform parameter abnormality sub-criteria, it is determined that there is an abnormality in the switching of the split-type on-load tap changer; if at least one of the odd-numbered current waveform signals of phase A, the even-numbered current waveform signals of phase A, the odd-numbered current waveform signals of phase B, and the even-numbered current waveform signals of phase B satisfies the waveform parameter abnormality sub-criteria. If the odd-numbered current waveform signal of phase A of the tap selector 11 and the even-numbered current waveform signal of phase A are integrated to meet the switching circulation time sub-criteria, or the odd-numbered current waveform signal of phase B of the tap selector and the even-numbered current waveform signal of phase B are integrated to meet the switching circulation time sub-criteria, then it is determined that the switching of the split on-load tap changer is abnormal. If the odd-numbered current waveform signal of phase A of the tap selector 11 and the even-numbered current waveform signal of phase A are integrated to meet the switching circulation time sub-criteria, then it is determined that the switching of the split on-load tap changer is abnormal.

[0054] It can be seen that by independently and integratedly judging the current waveform signals of each gear, whether the switching circulation time sub-criteria, the waveform discontinuity sub-criteria, the waveform switching discontinuity sub-criteria and the waveform parameter abnormality sub-criteria are satisfied. If the current waveform signals of any gear or multiple gears satisfy the switching circulation time sub-criteria, the waveform discontinuity sub-criteria, the waveform switching discontinuity sub-criteria or the waveform parameter abnormality sub-criteria, it is judged that there is an abnormality in the switching of the split-type on-load tap changer. Whether there is an abnormality in the switching of the split-type on-load tap changer can be judged through waveform discontinuity analysis and waveform parameter analysis.

[0055] Preferably, the waveform switching discontinuity sub-criteria include: if the split-type on-load tap changer switches between the odd-numbered current waveform signal of the A phase and the even-numbered current waveform signal of the A phase, the odd-numbered current waveform signal of the A phase and the even-numbered current waveform signal of the A phase are integrated, and if there is a waveform discontinuity at the switching point, it is determined that the switching of the split-type on-load tap changer is abnormal; if the split-type on-load tap changer switches between the odd-numbered current waveform signal of the B phase and the even-numbered current waveform signal of the B phase, the odd-numbered current waveform signal of the B phase and the even-numbered current waveform signal of the B phase are integrated, and if there is a waveform discontinuity at the switching point, it is determined that the switching of the split-type on-load tap changer is abnormal. Specifically, in the normal switching state, the odd gear is switched to the even gear, and the load current is first in the odd gear and then transferred to the even gear. Its waveform diagram can be shown as follows Fig.12 and Fig.14 As shown; or when the even gear is switched to the odd gear, the load current is first in the even gear and then transferred to the odd gear. The waveform diagram can be shown as Fig.13 and Fig.15 As shown; if during the switching process, the gear position of the tap changer is inconsistent with the corresponding load current, or there is a load current interruption, it indicates that the tap changer switching is abnormal. Therefore, when switching between the odd-numbered current waveform signal of phase A of the split on-load tap changer and the even-numbered current waveform signal of phase A, the odd-numbered current waveform signal of phase A of the split on-load tap changer and the even-numbered current waveform signal of phase A are integrated. If there is a waveform interruption at the switching location, or when switching between the odd-numbered current waveform signal of phase B of the split on-load tap changer and the even-numbered current waveform signal of phase B, the odd-numbered current waveform signal of phase B of the split on-load tap changer and the even-numbered current waveform signal of phase B are integrated. If there is a waveform interruption at the switching location, it is determined that the switching of the split on-load tap changer is abnormal. That is to say, the two current waveform signals corresponding to the switching of the current waveform signals of each gear are integrated before and after the switching, that is, the odd gears and the even gears corresponding to the current waveform signals of each gear are integrated. If there is a waveform discontinuity at the switching point of the current waveform signal integrated in any gear, that is, there is a waveform discontinuity in time, that is, there is a waveform discontinuity at the switching point of the current waveform signal integrated in at least one of the gears, that is, there is a waveform discontinuity in time, then it is determined that there is an abnormality in the switching of the split-type on-load tap changer.

[0056] It can be seen that by integrating the two current waveform signals corresponding to the switching of the current waveform signals of each gear, and judging whether there is a waveform discontinuity at the switching time, it can be judged whether there is an abnormality in the switching of the split on-load tap changer.

[0057] Preferably, the waveform parameter abnormality sub-criterion includes: if the current waveform signal of at least one gear position in the split-type on-load tap changer satisfies the following formula, it is determined that the switching of the split-type on-load tap changer is normal; otherwise, it is determined that the switching of the split-type on-load tap changer is abnormal;

[0058] ;

[0059] Where i(t) is the actual switching current of the A-phase or B-phase of the split-type on-load tap-changer in odd or even gears, in kA; i 0 (t) is the theoretical switching current of the odd or even gear of phase A and phase B of the split-type on-load tap-changer, in kA; t1 is a certain moment in the switching process of the split-type on-load tap-changer, in ms; Δt is the time interval for selecting continuous current from a certain moment in the switching process of the split-type on-load tap-changer, in ms.

[0060] It can be seen that the switching abnormality of the split on-load tap changer is judged by the amplitude of the current waveform signal. If the amplitude of the current waveform signal does not satisfy the above formula, it is judged that the switching of the split on-load tap changer is abnormal.

[0061] Preferably, the switching circulation time sub-criterion includes: if the switching circulation time of the split on-load tap changer is less than or equal to a preset time value, it is determined that the switching of the split on-load tap changer is normal; otherwise, it is determined that the switching of the split on-load tap changer is abnormal; wherein the preset time value is 15-18 ms, and the switching circulation time of the split on-load tap changer is the time interval during which current flows through the odd-numbered gear positions and the even-numbered gear positions simultaneously during the switching process of the split on-load tap changer.

[0062] Preferably, the waveform discontinuity sub-criterion includes: if there is a discontinuity in the current waveform signal of at least one gear in the split-type on-load tap changer, determining that there is an abnormality in the switching of the split-type on-load tap changer.

[0063] In this embodiment, the split-type on-load tap changer is cast in one piece with a lead bushing, that is, integral casting is adopted, and after positioning by the connection plate 62, the grounding column 63 and the four current-carrying terminals 64, an insulating cast column 61 is formed by pouring epoxy resin, and the lead bushing has the characteristics of flame retardancy and high mechanical strength. Among them, the lead bushing 6 can withstand the impact of 5MJ level arc fault pressure, and has good fireproof and explosion-proof performance. In extreme fault conditions, even if the lead bushing 6 is cracked by impact, no splashes will be generated, and the fault hazard is relatively small.

[0064] In this embodiment, the total length of the lead sleeve 6 can be 800 mm, the outer diameter of the connecting plate 62 can be 800 mm, the maximum diameter of the insulating cast column 61 is 650 mm, the diameter of the four current-carrying terminals 64 is 60 mm, and the diameter of the grounding terminal 63 can be 80 mm; the maximum operating voltage of the lead sleeve 6 is 72.5 kV, the rated current is 1500 A, and the maximum operating pressure is 0.6 MPa.

[0065] In summary, the lead bushing for the split on-load tap changer and the converter transformer provided in this embodiment realize the spatial isolation between the transformer main body oil tank 2 and the auxiliary oil tank 3 by means of the insulating cast column 61 and the isolation plate 5. The oil circuit is cut off by the oil tank connecting wall and the lead bushing, thereby realizing the spatial isolation between the switching switch part and the main oil tank, reducing the degree of influence of the destructive force of the arc fault of the switching switch on the main oil tank. Once a fault occurs, it does not need to be disassembled as a whole, thereby reducing the maintenance cost. The grounding column 63 embedded in the insulating cast column 61 has its two ends extended into the transformer main body oil tank 2 and the auxiliary oil tank 3, respectively connected to the grounding column 63. The neutral point of the tap selector 11 and the connection terminal corresponding to the neutral point on the switch 12 are connected; the four current-carrying terminals 64 embedded in the insulating cast column 61 are respectively connected to the current-carrying contacts of the tap selector 11 and the connection terminals corresponding to the corresponding current-carrying contacts on the switch 12, so as to realize the corresponding connection of the A and B phases of the odd and even gears of the tap selector 11, realize the connection between the tap selector 11 and the switch 12 respectively arranged in the transformer main body oil tank 2 and the auxiliary oil tank 3, realize the electrical reliable connection between the switch and the tap selector, and ensure the reliable current carrying.

[0066] Furthermore, the integrated built-in current transformer inside the lead bushing can collect the load current changes of each gear switching of the tap changer in real time, remotely monitor the operating status of the transformer and the split on-load tap changer 1, diagnose faults and perform preventive maintenance, thereby improving the sensitivity and reliability of electrical protection action.

[0067] Preferably, the lead bushing is integrally cast, has the advantages of flame retardancy, fire resistance, explosion resistance, etc., and will not produce splashes when punctured, playing an important role in ensuring the safe operation of the oil-immersed transformer.

[0068] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0069] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A lead bushing for a split on-load tap changer, characterized in that: include: Insulation casting column plays an insulating and protective role; A connection plate, which is sleeved on the outer periphery of the insulating cast column and is used to connect to the isolation plate between the transformer body oil tank of the converter transformer and the auxiliary oil tank where the switch is located; A grounding column, embedded in the insulating cast column, and the two ends of the grounding column extend to the two sides of the insulating cast column respectively, and are used to extend into the transformer main body oil tank and the auxiliary oil tank respectively, so as to respectively connect the neutral point of the tap selector and the connection terminal corresponding to the neutral point on the switch; Four current-carrying terminals are embedded in the insulating cast column, and the four current-carrying terminals are arranged in a circle on the outer periphery of the grounding column, and the two ends of each current-carrying terminal respectively extend to the two sides of the insulating cast column, and are used to extend into the transformer body oil tank and the auxiliary oil tank respectively, so as to be connected to the current-carrying contacts of the odd and even layers of the tap selector respectively, and the two ends of each current-carrying terminal are used to be connected to the current-carrying contacts of the odd and even layers of the tap selector and the connection terminals corresponding to the corresponding current-carrying contacts on the switch; Each of the current-carrying terminals is provided with a current transformer, and each of the current transformers is embedded in the insulating cast column. The current transformer is used to collect the load current in real time during the gear switching process of the split-type on-load tap changer to monitor the load current change during the switching process of the split-type on-load tap changer; The current transformer is connected to a controller, which is used to receive the load current collected by the current transformer during the gear switching process of the split-type on-load tap changer, so as to obtain the odd-numbered current waveform signals and the even-numbered current waveform signals of the A phase and the B phase of the split-type on-load tap changer, and independently and integratedly judge the current waveform signals according to the odd-numbered current waveform signals and the even-numbered current waveform signals of the A phase and the B phase of the split-type on-load tap changer based on the switching fault judgment criterion, so as to judge whether there is an abnormality in the switching of the split-type on-load tap changer; The switching fault judgment criterion is based on which each current waveform signal is judged independently and integratedly, including: If the current waveform signal of at least one gear satisfies the switching circulation time sub-criterion after integration, or the current waveform signal of at least one gear satisfies the waveform discontinuity sub-criterion, or the current waveform signal of at least one gear satisfies the waveform switching discontinuity sub-criterion after integration, or the current waveform signal of at least one gear satisfies the waveform parameter abnormality sub-criterion, it is determined that the switching of the split on-load tap changer is abnormal; The waveform parameter abnormality sub-criteria include: If the current waveform signal of at least one gear position of the split-type on-load tap changer satisfies the following formula, it is determined that the switching of the split-type on-load tap changer is normal, otherwise, it is determined that the switching of the split-type on-load tap changer is abnormal; ； Wherein, i(t) is the actual switching current of the odd or even gear of phase A and phase B of the split-type on-load tap changer, in kA; i0(t) is the theoretical switching current of the odd or even gear of phase A and phase B of the split-type on-load tap changer, in kA; t1 is a certain moment in the switching process of the split-type on-load tap changer, in ms; Δt is the time interval for selecting continuous current from a certain moment in the switching process of the split-type on-load tap changer, in ms.

2. The lead bushing for the split on-load tap changer according to claim 1, characterized in that: The waveform discontinuity sub-criterion includes: If there is a discontinuity in the current waveform signal of at least one gear of the split-type on-load tap changer, it is determined that there is an abnormality in the switching of the split-type on-load tap changer.

3. The lead bushing for the split on-load tap changer according to claim 1, characterized in that: The switching circulation time sub-criterion includes: If the switching circulation time of the split on-load tap changer is greater than a preset time value, it is determined that the switching of the split on-load tap changer is abnormal; wherein the preset time value is 15-18 ms, and the switching circulation time of the split on-load tap changer is the time interval during which current flows through the odd-numbered gear positions and the even-numbered gear positions simultaneously during the switching process of the split on-load tap changer.

4. The lead bushing for a split on-load tap changer according to claim 1, characterized in that: The waveform switching discontinuity sub-criterion includes: When switching between the odd-numbered current waveform signal of phase A and the even-numbered current waveform signal of phase A of the split on-load tap changer, the odd-numbered current waveform signal of phase A and the even-numbered current waveform signal of phase A of the split on-load tap changer are integrated, and if there is a waveform discontinuity at the switching point, it is determined that the switching of the split on-load tap changer is abnormal; If the split-type on-load tap changer switches between the odd-numbered current waveform signal of phase B and the even-numbered current waveform signal of phase B, the odd-numbered current waveform signal of phase B and the even-numbered current waveform signal of phase B of the split-type on-load tap changer are integrated, and if there is a waveform discontinuity at the switching point, it is determined that there is an abnormality in the switching of the split-type on-load tap changer.

5. The lead bushing for a split on-load tap changer according to any one of claims 1 to 4, characterized in that: The insulating casting column is cast by epoxy resin, and the lead sleeve is cast in one piece.

6. The lead bushing for a split on-load tap changer according to any one of claims 1 to 4, characterized in that: The connecting plate is a flange structure.

7. A converter transformer, characterized in that: A lead bushing for a split on-load tap changer as claimed in any one of claims 1 to 6 is provided.

8. The converter transformer according to claim 7, characterized in that: Also includes: A transformer body oil tank, wherein the tap selector of the split on-load tap changer is arranged at the top of the transformer body oil tank; The auxiliary oil tank is arranged on one side of the top of the transformer main body oil tank and is arranged at a position close to the tap selector. The switching switch of the split on-load tap changer is arranged inside the auxiliary oil tank. The lead sleeve for the split on-load tap changer is arranged on the isolation plate between the transformer main body oil tank and the auxiliary oil tank.

Images