A on-load tap-changer single isolation contact transition circuit and voltage regulation method

Abstract

A on-load tap-changer single isolation contact transition circuit and voltage regulation method, comprising a first main current-carrying switch, a second main current-carrying switch and a transfer switch; the first end of the first main current-carrying switch, the first end of the first transition resistor and the first static contact of the transfer switch are all connected to the first winding tap of the transformer voltage regulating winding; the first end of the second main current-carrying switch, the first end of the second transition resistor and the second static contact of the transfer switch are all connected to the second winding tap of the transformer voltage regulating winding; the second end of the first main current-carrying switch, the second end of the second main current-carrying switch, the second end of the third switching element and the second end of the fourth switching element are all connected to the neutral point lead-out end of the on-load tap-changer. The present invention uses two transition resistors to limit the current, so that while the recovery voltage of the switching element is relatively low, the inter-stage short-circuit current during the switching process is reduced; at the same time, it can carry a symmetric reciprocating time sequence, and during the forward and reverse reciprocating switching process, the action time sequence is mirror-symmetric, without a mechanical track-changing mechanism.

Description

Technical Field

[0001] The present invention belongs to the technical field of on-load tap-changers, and particularly relates to a single isolation contact transition circuit and a voltage regulation method for an on-load tap-changer. Background Art

[0002] An on-load tap-changer is a key component inside a power transformer, which can operate under the excitation or load state of the transformer. By changing several tap points led out from the transformer winding, the effective turns ratio is changed, so as to adjust the output voltage without interrupting the load current. On-load tap-changers are widely used, especially in the converter transformers of UHV DC transmission projects to ensure the rated firing angle of the converter during normal operation.

[0003] Most of the on-load tap-changers equipped with early power transformers adopted the high-speed resistance switching principle and relied on copper-tungsten arc contacts for load conversion; such oil-immersed non-vacuum on-load tap-changers switched frequently, and the arc contacts were correspondingly severely burned, and the carbonization and pollution speed of the oil was relatively fast, so it increased the daily maintenance and regular overhaul workload for the power supply department. Vacuum on-load tap-changers mainly use vacuum tubes to extinguish arcs, avoiding the carbonization and pollution of the oil during arc extinguishing in oil; due to the short opening and arcing time, low arc voltage, small arc energy consumption of the vacuum tube and the recondensation of the contact metal vapor, the contact burning and corrosion can be minimized. Power electronic on-load tap-changers use power electronic components to replace vacuum tubes to achieve no open circuit arc operation during on-load switching.

[0004] An on-load tap-changer consists of a switching switch, a tap selector and an electric mechanism; among them, the switching switch has an independent oil chamber and is the key component for the on-load tap-changer to achieve on-load switching, and its core is to adopt a transition circuit. Vacuum on-load tap-changers can be divided into single-contact circuits, double-contact circuits, triple-contact circuits and quadruple-contact circuits according to the number of their vacuum tubes; there are two types of single-resistance and double-resistance transitions according to the number of their transition resistors; there are single-break and double-break contacts according to the number of their contact breaks; the above various combinations can form different types of vacuum on-load tap-changer transition circuits. The switching elements in the transition circuit can be single-break vacuum contacts, double-break vacuum contacts, power electronic components, etc.; different transition circuits have different switching time sequences to achieve on-load voltage regulation, and the switching tasks of each switching element will also be different. The topological structure of the transition circuit has a significant impact on the reliability of the on-load tap-changer switching process, as well as the failure rate and electrical life of the switch.

[0005] In the existing transition circuit of the on-load tap-changer in vacuum, the control timings for switching from the winding tap N to the winding tap N+1 and from the winding tap N+1 to the winding tap N are asymmetric. During the mechanical reciprocating movement of the switching core, the cam mechanism needs to achieve lifting and track changing, thus increasing the complexity of mechanical manufacturing and the failure rate of switch use. Summary of the Invention

[0006] The object of the present invention is to provide a transition circuit with a single isolation contact and a voltage regulation method for an on-load tap-changer. This transition circuit can effectively limit the inter-stage short-circuit current during the switching process and can carry a symmetric reciprocating timing. In the mechanical on-load tap-changer adopting the transition circuit and the voltage regulation method, the action timings are mirror-symmetric during the forward and reverse reciprocating switching, and no mechanical track-changing mechanism is required.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A transition circuit with a single isolation contact for an on-load tap-changer includes a first main current-carrying switch, a second main current-carrying switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor, a second transition resistor, and a change-over switch;

[0009] Among them, the first end of the first main current-carrying switch, the first end of the first transition resistor, and the first static contact of the change-over switch are all connected to the first winding tap of the transformer voltage-regulating winding; the first end of the second main current-carrying switch, the first end of the second transition resistor, and the second static contact of the change-over switch are all connected to the second winding tap of the transformer voltage-regulating winding;

[0010] The first ends of the first switching element and the second switching element are both connected to the moving contact of the change-over switch;

[0011] The second end of the first switching element and the first end of the third switching element are both connected to the second end of the first transition resistor;

[0012] The second end of the second switching element and the first end of the fourth switching element are both connected to the second end of the second transition resistor;

[0013] The second ends of the first main current-carrying switch, the second main current-carrying switch, the third switching element, and the fourth switching element are all connected to the neutral point lead-out end of the on-load tap-changer.

[0014] Further, the first switching element, the second switching element, the third switching element, and the fourth switching element are single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable on-off functions.

[0015] Further, the power electronic component with controllable on-off function is a thyristor or an insulated gate bipolar transistor.

[0016] Further, the first switching element and the second switching element are used to break the load current; the third switching element and the fourth switching element are used to break the inter-stage circulating current.

[0017] Further, the first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap and the second winding tap of the transformer voltage regulating winding are bridged.

[0018] Further, when the first main current-carrying switch, the first switching element, and the third switching element are all in the conducting state; the moving contact of the changeover switch is connected to the first static contact, and the second main current-carrying switch, the second switching element, and the fourth switching element are all in the off state, the on-load tap-changer transition circuit can make the load current flow out from the first winding tap through the first main current-carrying switch and the neutral point lead-out terminal; when the second main current-carrying switch, the second switching element, and the fourth switching element are all in the conducting state; the moving contact of the changeover switch is connected to the second static contact; and the first main current-carrying switch, the first switching element, and the third switching element are all in the off state, the on-load tap-changer transition circuit can make the load current flow out from the second winding tap through the second main current-carrying switch and the neutral point lead-out terminal.

[0019] A voltage regulation method based on the above on-load tap-changer single isolation contact transition circuit includes the following steps:

[0020] The first main current-carrying switch, the first switching element, and the third switching element are all in the conducting state, and the moving contact of the changeover switch is connected to the first static contact; the second main current-carrying switch, the second switching element, and the fourth switching element are all in the off state;

[0021] Disconnect the first main current-carrying switch, disconnect the first switching element, leave the moving contact of the changeover switch vacant, conduct the fourth switching element, disconnect the third switching element, connect the moving contact of the changeover switch to the second static contact, conduct the second switching element; conduct the second main current-carrying switch;

[0022] The load current flows out from the second winding tap through the second main current-carrying switch and the neutral point lead-out terminal, and the on-load tap-changer switches from the first winding tap to the second winding tap.

[0023] A voltage regulation method based on the above on-load tap-changer single isolation contact transition circuit includes the following steps:

[0024] The second main current-carrying switch, the second switching element, and the fourth switching element are all in the conducting state; the moving contact of the changeover switch is connected to the second static contact; the first main current-carrying switch, the first switching element, and the third switching element are all in the off state;

[0025] Disconnect the second main current-carrying switch, disconnect the second switching element, leave the moving contact of the changeover switch vacant, conduct the third switching element, disconnect the fourth switching element, connect the moving contact of the changeover switch to the first static contact, conduct the first switching element, conduct the first main current-carrying switch, and the load current flows out from the neutral point lead-out terminal through the first main current-carrying switch from the second winding tap, and the on-load tap-changer switches from the second winding tap to the first winding tap.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The transition circuit in the present invention adopts a single isolation changeover switch and uses the first transition resistor and the second transition resistor to limit the current, which can effectively limit the inter-stage short-circuit current during the switching process, and at the same time can carry the symmetric reciprocating time sequence. During the forward and reverse reciprocating switching process of the mechanical on-load tap-changer adopting the transition circuit and the voltage regulation method, the action time sequence is mirror-symmetrical and no mechanical rail-changing mechanism is required. In the single-isolation contact transition circuit of the on-load tap-changer provided by the present invention, a changeover switch is adopted, which can not only play the role of electrical isolation, but also serve as the protection switch of the switching element to prevent the failure of the switching element to interrupt the current.

[0028] The voltage regulation method of the transition circuit in the present invention has a mirror-symmetrical action time sequence during the forward and reverse reciprocating switching process, avoiding the mechanical structure rail-changing operation; the transition circuit uses two transition resistors to limit the current, making the recovery voltage of the switching element lower while reducing the inter-stage short-circuit current during the switching process. In the present invention, the first switching element and the second switching element alternately take on the task of interrupting the load current, and the third switching element and the fourth switching element alternately take on the task of interrupting the inter-stage circulating current, reducing the working loss degree of a single switching element, balancing the switching capacity between the switching elements, and reducing the failure rate of the switching elements. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required to be used in the description of the embodiments or the prior art; obviously, the following drawings are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0030] Figure 1 FIG. is a circuit diagram of an on-load tap-changer transition circuit according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0035] Figure 6 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0036] Figure 7 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0037] Figure 8 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0038] Figure 9 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0039] Figure 10 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0040] Figure 11 Schematic diagram of the on-off states of each switch in the on-load tap-changer transition circuit according to an embodiment of the present invention during the process of the load being switched from winding tap N to winding tap N + 1;

[0041] Figure 12 Schematic diagram of the on-off states of each switch in the on-load tap-changer transition circuit according to an embodiment of the present invention during the process of the load being switched from winding tap N + 1 to winding tap N;

[0042] Figure 13 Circuit diagram of the on-load tap-changer single isolation contact transition circuit with a power electronic component as the switching element according to an embodiment of the present invention;

[0043] Figure 14 Circuit diagram of the on-load tap-changer single isolation contact transition circuit with a double-break vacuum contact as the switching element according to an embodiment of the present invention. Detailed implementation mode

[0044] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0046] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0047] A on-load tap-changer single isolation contact transition circuit according to an embodiment of the present invention includes: a first main current-carrying switch, a second main current-carrying switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor, a second transition resistor, and a change-over switch. Among them, the first end of the first main current-carrying switch, the first end of the first transition resistor, and the first stationary contact of the change-over switch are all connected to the first winding tap N of the transformer voltage regulating winding; the first end of the second main current-carrying switch, the first end of the second transition resistor, and the second stationary contact of the change-over switch are all connected to the second winding tap N+1 of the transformer voltage regulating winding; the first ends of the first switching element and the second switching element are both connected to the moving contact of the change-over switch; the second end of the first switching element and the first end of the third switching element are both connected to the second end of the first transition resistor; the second end of the second switching element and the first end of the fourth switching element are both connected to the second end of the second transition resistor; the second ends of the first main current-carrying switch, the second main current-carrying switch, the third switching element, and the fourth switching element are all connected to the neutral point lead-out end of the on-load tap-changer.

[0048] Further, the conversion switch forms a single-pole triple-throw switch. The moving contact of the conversion switch is connected to the first static contact on the N side of the first winding tap to form the first working state of the switch. The moving contact of the conversion switch is connected to the second static contact on the N+1 side of the second winding tap to form the second working state of the switch. The moving contact of the conversion switch is left vacant and not connected to either the first static contact or the second static contact to form the third working state of the switch.

[0049] Further, the first switching element, the second switching element, the third switching element, and the fourth switching element can be single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable on-off functions (such as thyristors or insulated gate bipolar transistors).

[0050] In the embodiment of the present invention, the first main current-carrying switch and the second main current-carrying switch are used for long-term current-carrying of the load current; the first switching element and the second switching element are used for alternately interrupting the load current; the third switching element and the fourth switching element are used for alternately interrupting the inter-stage circulating current. The first transition resistor and the second transition resistor are used to limit the inter-stage circulating current simultaneously when bridging the first winding tap N and the second winding tap N+1 of the transformer voltage regulating winding. Exemplarily, the actual selection specifications of each component are determined by the actual working conditions of the transition circuit.

[0051] As Figure 1 shown, for the on-load tap-changer single-isolation contact transition circuit in the embodiment of the present invention, taking the single-break vacuum tube as an example for the switching element, it includes: the first main current-carrying switch MC1, the second main current-carrying switch MC2, the first vacuum tube V1, the second vacuum tube V2, the third vacuum tube V3, the fourth vacuum tube V4, the first transition resistor R1, the second transition resistor R2, and the conversion switch T.

[0052] Among them, the first end of the first main current-carrying switch MC1, the first end of the first transition resistor R1, and the first static contact 11 of the conversion switch are all connected to the first winding tap N of the transformer voltage regulating winding; the first end of the second main current-carrying switch MC2, the first end of the second transition resistor R2, and the second static contact 12 of the conversion switch T are all connected to the second winding tap N+1 of the transformer voltage regulating winding; the first ends of the first vacuum tube V1 and the second vacuum tube V2 are both connected to the moving contact of the conversion switch T; the second end of the first vacuum tube V1 and the first end of the third vacuum tube V3 are both connected to the second end of the first transition resistor R1; the second end of the second vacuum tube V2 and the first end of the fourth vacuum tube V4 are both connected to the second end of the second transition resistor R2; the second ends of the first main current-carrying switch MC1, the second main current-carrying switch MC2, the second end of the third vacuum tube V3, and the second end of the fourth vacuum tube V4 are all connected to the neutral point lead-out end of the on-load tap-changer.

[0053] In an embodiment of the present invention, when the first main current-carrying switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the conducting state; the moving contact of the changeover switch T is connected to the first static contact 11 on the N side of the first winding tap, and it is in the first working state; when the second main current-carrying switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 are all in the off state, the on-load tap-changer transition circuit can make the load current flow out from the neutral point lead-out terminal through the first main current-carrying switch MC1 from the first winding tap N. When the second main current-carrying switch MC2, the second vacuum tube V2, and the fourth vacuum tube V are all in the conducting state; the moving contact of the changeover switch T is connected to the second static contact 12 on the N+1 side of the second winding tap, and it is in the second working state; when the first main current-carrying switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the off state, the on-load tap-changer transition circuit can make the load current flow out from the neutral point lead-out terminal through the second main current-carrying switch MC2 from the second winding tap N+1.

[0054] In an embodiment of the present invention, the transition circuit adopts a single isolation changeover switch and uses two transition resistors to limit the current, which can effectively limit the inter-stage short-circuit current during the switching process and can also carry the symmetric reciprocating time sequence. The mechanical on-load tap-changer adopting the transition circuit and the voltage regulation method has a mirror-symmetric action time sequence during the positive and negative reciprocating switching process and does not require a mechanical track-changing mechanism. Specifically, in the single-isolation contact transition circuit of the on-load tap-changer provided by the embodiment of the present invention, a changeover switch is designed, which can not only play an electrical isolation role but also serve as a protection switch for the vacuum tube to prevent the failure of the vacuum tube from being unable to interrupt the current. During the positive and negative reciprocating switching process of the transition circuit and its voltage regulation method, the action time sequence is mirror-symmetric, avoiding the mechanical structure track-changing operation; the transition circuit is designed with two transition resistors to limit the current, while reducing the voltage of the vacuum tube recovery, reducing the inter-stage short-circuit current during the switching process.

[0055] In an embodiment of the present invention, the first vacuum tube and the second vacuum tube alternately take on the task of interrupting the load current, and the third vacuum tube and the fourth vacuum tube alternately take on the task of interrupting the inter-stage circulating current, reducing the working loss degree of a single vacuum tube, balancing the switching capacity between vacuum tubes, and reducing the failure rate of vacuum tubes.

[0056] A voltage regulation method for a single-isolation contact transition circuit of an on-load tap-changer according to an embodiment of the present invention is described by taking a single-break vacuum tube as an example. When the on-load tap-changer switches from the current transformer winding tap to a preselected new transformer winding tap, that is, the switching process from the first winding tap N to the second winding tap N+1 is as follows:

[0057] The first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the conducting state; the moving contact of the transfer switch T is connected to the first static contact 11 on the N side of the first winding tap, and is in the first working state; the second main current - conducting switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 are all in the off state;

[0058] Disconnect the first main current - conducting switch MC1;

[0059] Disconnect the first vacuum tube V1 to generate an arc;

[0060] After the first vacuum tube V1 is completely extinguished, move the first working state where the moving contact of the transfer switch T is connected to the first static contact 11 to the third working state where the moving contact of the transfer switch is vacant;

[0061] Conduct the fourth vacuum tube V4;

[0062] Disconnect the third vacuum tube to generate an arc;

[0063] After the third vacuum tube V3 is completely extinguished, move the third working state where the moving contact of the transfer switch is vacant to the second working state where the moving contact of the transfer switch is connected to the second static contact 12;

[0064] Conduct the second vacuum tube V2;

[0065] Conduct the second main current - conducting switch MC2;

[0066] The load current flows out from the neutral - point lead - out terminal through the second main current - conducting switch from the second winding tap N + 1, and the switching process of the on - load tap - changing switch from the first winding tap N to the second winding tap N + 1 ends.

[0067] The voltage - regulating method of a transition circuit with a single - isolation contact for an on - load tap - changing switch according to an embodiment of the present invention is illustrated by taking a single - break - port vacuum tube as an example. The switching process of the on - load tap - changing switch from the second winding tap N + 1 to the first winding tap N is as follows:

[0068] The second main current - conducting switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 are all in the conducting state; the moving contact of the transfer switch T is connected to the second static contact 12 on the N + 1 side of the second winding tap, and is in the second working state; the first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the off state;

[0069] Disconnect the second main current - conducting switch MC2;

[0070] Disconnect the second vacuum tube V2 to generate an arc;

[0071] After the second vacuum tube V2 is completely extinguished, the second working state where the moving contact of the transfer switch T is connected to the second stationary contact 12 is changed to the third working state where the moving contact of the transfer switch is vacant;

[0072] Turn on the third vacuum tube V3;

[0073] Turn off the fourth vacuum tube V4 to generate an arc;

[0074] After the fourth vacuum tube is completely extinguished, the third working state where the moving contact of the transfer switch T is vacant is changed to the first working state where the moving contact of the transfer switch T is connected to the first stationary contact 12;

[0075] Turn on the first vacuum tube V1;

[0076] Turn on the first main current-carrying switch MC1;

[0077] The load current flows out from the neutral point lead-out terminal through the first main current-carrying switch from the second winding tap N, and the switching process of the on-load tap-changer from the second winding tap N+1 to the first winding tap N ends.

[0078] The voltage regulation method of a transition circuit with a single isolation contact for an on-load tap-changer according to an embodiment of the present invention is described by taking a single-break vacuum tube as an example; when the on-load tap-changer switches from the winding tap N to the winding tap N+1, the voltage regulation method is as follows:

[0079] As Figure 2 shown, the first main current-carrying switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the on state; the moving contact of the transfer switch T is connected to the first stationary contact 11 on the side of the first winding tap N, and is in the first working state; the second main current-carrying switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 are all in the off state; the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the first main current-carrying switch MC1 from the first winding tap N.

[0080] As Figure 3 shown, disconnect the first main current-carrying switch MC1, and keep the first vacuum tube V1 and the third vacuum tube V3 on; keep the moving contact of the transfer switch T connected to the first stationary contact 11 on the side of the first winding tap N, and keep the first working state; keep the second main current-carrying switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 off; the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the transfer switch T, the first vacuum tube V1, and the third vacuum tube V3.

[0081] As Figure 4As shown, the first main current - conducting switch MC1 remains open, disconnecting the first vacuum tube V1 to generate an arc, and the third vacuum tube V3 remains conducting; the moving contact of the transfer switch T is connected to the first static contact 11 on the N - side of the first winding tap, maintaining the first operating state; the second main current - conducting switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 remain open; the winding tap N is connected, and the load current flows out from the neutral - point lead - out terminal through the first transition resistor R1 and the third vacuum tube V3.

[0082] As Figure 5 shown, the first main current - conducting switch MC1 remains open, the first vacuum tube V1 remains open, and the third vacuum tube V3 remains conducting; after the first vacuum tube V1 is completely extinguished, the first operating state where the moving contact of the transfer switch T is connected to the first static contact 11 is changed to the third operating state where the moving contact of the transfer switch is vacant; the second main current - conducting switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 remain open; the winding tap N is connected, and the load current flows out from the neutral - point lead - out terminal through the first transition resistor R1 and the third vacuum tube V3.

[0083] As Figure 6 shown, the first main current - conducting switch MC1 remains open, the first vacuum tube V1 remains open, and the third vacuum tube V3 remains conducting; the moving contact of the transfer switch T is vacant, in the third operating state; the second main current - conducting switch MC2 and the second vacuum tube V2 remain open; the fourth vacuum tube V4 is made conducting, both the winding tap N and the winding tap N + 1 are connected, and the load current I N flows out from the neutral - point lead - out terminal through the third vacuum tube V3, the first transition resistor R1 and the fourth vacuum tube V4, the second transition resistor R2 respectively; the transition circuit forms a bridge connection, generating an inter - stage circulating current I C ; the current I V3 flowing through the third vacuum tube V3 is I N =I C / 2 + I V4 ; the current I N flowing through the fourth vacuum tube V4 is I C =I C / 2 - I C ; where I C =U S / (R1 + R2), and the U S is the on - load tap - changer step voltage.

[0084] As Figure 7 shown, the first main current - conducting switch MC1 remains open, the first vacuum tube V1 remains open, disconnecting the third vacuum tube V3 to generate an arc; the moving contact of the transfer switch T is vacant, in the third operating state; the second main current - conducting switch MC2 and the second vacuum tube V2 remain open; the fourth vacuum tube V4 remains conducting, the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the second transition resistor R2 and the fourth vacuum tube V4.

[0085] As Figure 8 shown, the first main current - conducting switch MC1 remains open, and the first vacuum tube V1 and the third vacuum tube V3 remain open; the moving contact of the change - over switch is moved from the third operating state where it is vacant to the second operating state where it is connected to the second static contact 12; the second main current - conducting switch MC2 and the second vacuum tube V2 remain open, the fourth vacuum tube V4 remains conducting, the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the second transition resistor R2 and the fourth vacuum tube V4.

[0086] As Figure 9 shown, the first main current - conducting switch MC1 remains open, and the first vacuum tube V1 and the third vacuum tube V3 remain open; the moving contact of the change - over switch is connected to the second static contact 12, maintaining the second operating state; the second main current - conducting switch MC2 remains open, the fourth vacuum tube V4 remains conducting, the second vacuum tube V2 is made conducting, the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the second vacuum tube V2 and the fourth vacuum tube V4.

[0087] As Figure 10 shown, the first main current - conducting switch MC1 remains open, and the first vacuum tube V1 and the third vacuum tube V3 remain open; the moving contact of the change - over switch is connected to the second static contact 12, maintaining the second operating state; the second vacuum tube V2 and the fourth vacuum tube V4 remain conducting, the second main current - conducting switch MC2 is made conducting, the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal from the second winding tap N + 1 through the second main current - conducting switch MC2.

[0088] When the on - load tap - changer switches from the winding tap N + 1 to the winding tap N, the switching process is symmetric to the switching process when the on - load tap - changer switches from the winding tap N to the winding tap N + 1. The specific voltage - regulating method is as follows:

[0089] The second main current - conducting switch MC2, the second vacuum tube V2, and the fourth vacuum tube V4 are all in the conducting state; the moving contact of the change - over switch T is connected to the second static contact 12 on the side of the second winding tap N + 1, being in the second operating state; the first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 are all in the open state; the winding tap N + 1 is connected, and the load current flows out from the second winding tap N + 1 through the second main current - conducting switch MC2 from the neutral - point lead - out terminal.

[0090] The second main current - conducting switch MC2 is disconnected, and the second vacuum tube V2 and the fourth vacuum tube V4 remain conducting; the moving contact of the change - over switch T is connected to the second static contact 12 on the side of the second winding tap N + 1, maintaining the second operating state; the first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 remain open; the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the change - over switch T, the second vacuum tube V2, and the fourth vacuum tube V4.

[0091] The second main current - conducting switch MC2 remains open, disconnecting the second vacuum tube V2 to generate an arc, while the fourth vacuum tube V4 remains conducting; the moving contact of the transfer switch T is connected to the second static contact 12 on the N + 1 side of the second winding tap, maintaining the second working state; the first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 remain open; the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the second transition resistor R2 and the fourth vacuum tube V4.

[0092] The second main current - conducting switch MC2 remains open, the second vacuum tube V2 remains open, and the fourth vacuum tube V4 remains conducting; after the second vacuum tube V2 is completely extinguished, the operation of the second working state where the moving contact of the transfer switch T is connected to the second static contact 12 changes to the third working state where the moving contact of the transfer switch is vacant; the first main current - conducting switch MC1, the first vacuum tube V1, and the third vacuum tube V3 remain open; the winding tap N + 1 is connected, and the load current flows out from the neutral - point lead - out terminal through the second transition resistor R2 and the fourth vacuum tube V4.

[0093] The second main current - conducting switch MC2 remains open, the second vacuum tube V2 remains open, and the fourth vacuum tube V4 remains conducting; the moving contact of the transfer switch T is vacant, being in the third working state; the first main current - conducting switch MC1 and the first vacuum tube V1 remain open; the third vacuum tube V3 is made conducting, and both the winding tap N + 1 and the winding tap N are connected, and the load current I N flows out from the neutral - point lead - out terminal through the fourth vacuum tube V4, the second transition resistor R2 and through the third vacuum tube V3, the first transition resistor R1 respectively; the transition circuit forms a bridge connection, generating an inter - stage circulating current I C ; the current I V3 flowing through the fourth vacuum tube V4 is I N / 2+I C , and the current I V4 flowing through the third vacuum tube V3 is I N / 2 - I C ; where I C = U S / (R1 + R2), and the U S is the on - load tap - changer step voltage.

[0094] The second main current - conducting switch MC2 remains open, the second vacuum tube V2 remains open, the fourth vacuum tube V4 is disconnected to generate an arc; the moving contact of the transfer switch T is vacant, being in the third working state; the first main current - conducting switch MC1 and the first vacuum tube V1 remain open; the third vacuum tube V3 remains conducting, the winding tap N is connected, and the load current flows out from the neutral - point lead - out terminal through the first transition resistor R1 and the third vacuum tube V3.

[0095] The second main current-carrying switch MC2 remains open, and the second vacuum tube V2 and the fourth vacuum tube V4 remain open; the moving contact of the changeover switch is moved from the idle third operating state to the first operating state where it is connected to the first static contact 11; the first main current-carrying switch MC1 and the first vacuum tube V1 remain open, the third vacuum tube V3 remains conducting, the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the first transition resistor R1 and the third vacuum tube V3.

[0096] The second main current-carrying switch MC2 remains open, and the second vacuum tube V2 and the fourth vacuum tube V4 remain open; the moving contact of the changeover switch is connected to the first static contact 11, maintaining the first operating state; the first main current-carrying switch MC1 remains open, the third vacuum tube V3 remains conducting, the first vacuum tube V1 is made conducting, the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the changeover switch T, the first vacuum tube V1, and the third vacuum tube V3.

[0097] The second main current-carrying switch MC2 remains open, and the second vacuum tube V2 and the fourth vacuum tube V4 remain open; the moving contact of the changeover switch is connected to the first static contact 11, maintaining the first operating state; the first vacuum tube V1 and the third vacuum tube V3 remain conducting, the first main current-carrying switch MC1 is made conducting, the winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the first main current-carrying switch MC1 from the first winding tap N.

[0098] When the on-load tap-changer switches from tapping on the winding N tap to tapping on the winding N+1 tap, the transition circuit conversion procedure is as Figure 11 shown;

[0099] When the on-load tap-changer switches from tapping on the winding N+1 tap to tapping on the winding N tap, the transition circuit conversion procedure is as Figure 12 shown;

[0100] When the internal switching element in the on-load tap-changer single isolation contact transition circuit is a power electronic element with controllable on / off function (such as thyristor or insulated gate bipolar transistor) or a double-break vacuum tube, the action timing and voltage regulation method of the switching element are the same and will not be elaborated.

[0101] In the embodiment of the present invention, the switching tasks of the on-load tap-changer transition circuit using vacuum tubes are shown in the following table:

[0102]

[0103] where, I N is the load current; U S is the voltage between poles of the on-load tap-changer; both R1 and R2 are transition resistors.

[0104] As Figure 13 shown, onlyFigure 1 The single-break vacuum tube in Figure 1 is replaced with a power electronic component with controllable on / off. The other components are the same as those in Figure 1 , with the same operation timing, and the same functions and effects as the transition circuit shown in

[0105] As Figure 14 shown, only the single-break vacuum tube in Figure 1 is replaced with a double-break vacuum tube. The other components are the same as those in Figure 1 , with the same operation timing, and the same functions and effects as the transition circuit shown in Figure 1 , which will not be elaborated here.

[0106] As described above, this is only the best specific implementation mode of the present invention. However, the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the technical field of the present invention within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A voltage regulating method for a single isolating contact transition circuit of an on-load tap changer, characterized in that: The on-load tap changer single isolating contact transition circuit includes a first main current-carrying switch, a second main current-carrying switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor, a second transition resistor and a transfer switch; The first end of the first main pass-through switch, the first end of the first transition resistor, and the first static contact of the transfer switch are all connected to the first winding tap of the transformer voltage regulating winding; the first end of the second main pass-through switch, the first end of the second transition resistor, and the second static contact of the transfer switch are all connected to the second winding tap of the transformer voltage regulating winding; The first end of the first switching element and the first end of the second switching element are both connected to the moving contact of the transfer switch; The second end of the first switching element and the first end of the third switching element are both connected to the second end of the first transition resistor; The second end of the second switching element and the first end of the fourth switching element are both connected to the second end of the second transition resistor; The second end of the first main pass-through switch, the second end of the second main pass-through switch, the second end of the third switching element, and the second end of the fourth switching element are all connected to the neutral point lead-out terminal of the on-load tap changer; The voltage regulation method comprises the following steps: The first main through-current switch, the first switching element and the third switching element are all in the on state, and the movable contact of the transfer switch is connected to the first static contact; the second main through-current switch, the second switching element and the fourth switching element are all in the off state; Disconnect the first main through-current switch, disconnect the first switching element, leave the moving contact of the transfer switch unconnected, connect the fourth switching element, disconnect the third switching element, connect the moving contact of the transfer switch to the second static contact, connect the second switching element, and connect the second main through-current switch; The load current flows out from the second winding tap through the second main current-carrying switch from the neutral point lead-out terminal, and the on-load tap changer switches from the first winding tap to the second winding tap.

2. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 1, characterized in that: The first switch element, the second switch element, the third switch element and the fourth switch element are single-break vacuum tubes, double-break vacuum tubes or power electronic elements with controllable on-off functions.

3. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 2, characterized in that: The power electronic component with controllable on-off function is a thyristor or an insulated gate bipolar transistor.

4. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 1, characterized in that: The first switch element and the second switch element are used to interrupt the load current; the third switch element and the fourth switch element are used to interrupt the inter-stage circulating current.

5. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 1, characterized in that: The first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap and the second winding tap of the transformer voltage regulating winding are bridged.

6. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 1, characterized in that: When the first main through-current switch, the first switching element and the third switching element are all in the on state; the moving contact of the transfer switch is connected to the first static contact, and the second main through-current switch, the second switching element and the fourth switching element are all in the off state, the transition circuit can enable the load current to flow from the first winding tap through the first main through-current switch and out from the neutral point lead-out end; when the second main through-current switch, the second switching element and the fourth switching element are all in the on state; the moving contact of the transfer switch is connected to the second static contact; and the first main through-current switch, the first switching element and the third switching element are all in the off state, the transition circuit can enable the load current to flow from the second winding tap through the second main through-current switch and out from the neutral point lead-out end.

7. A voltage regulation method for a single isolating contact transition circuit of an on-load tap changer, characterized in that: The on-load tap changer single isolating contact transition circuit includes a first main current-carrying switch, a second main current-carrying switch, a first switching element, a second switching element, a third switching element, a fourth switching element, a first transition resistor, a second transition resistor and a transfer switch; The first end of the first main pass-through switch, the first end of the first transition resistor, and the first static contact of the transfer switch are all connected to the first winding tap of the transformer voltage regulating winding; the first end of the second main pass-through switch, the first end of the second transition resistor, and the second static contact of the transfer switch are all connected to the second winding tap of the transformer voltage regulating winding; The first end of the first switching element and the first end of the second switching element are both connected to the moving contact of the transfer switch; The second end of the first switching element and the first end of the third switching element are both connected to the second end of the first transition resistor; The second end of the second switching element and the first end of the fourth switching element are both connected to the second end of the second transition resistor; The second end of the first main pass-through switch, the second end of the second main pass-through switch, the second end of the third switching element, and the second end of the fourth switching element are all connected to the neutral point lead-out terminal of the on-load tap changer; The voltage regulation method comprises the following steps: The second main through-current switch, the second switching element and the fourth switching element are all in the on state; the movable contact of the transfer switch is connected to the second static contact; the first main through-current switch, the first switching element and the third switching element are all in the off state; The second main pass-through switch is turned off, the second switching element is turned off, the moving contact of the transfer switch is left vacant, the third switching element is turned on, the fourth switching element is turned off, the moving contact of the transfer switch is connected to the first static contact, the first switching element is turned on, the first main pass-through switch is turned on, the load current flows from the second winding tap through the first main pass-through switch and out of the neutral point lead-out terminal, and the on-load tap changer switches from the second winding tap to the first winding tap.

8. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 7, characterized in that: The first switch element, the second switch element, the third switch element and the fourth switch element are single-break vacuum tubes, double-break vacuum tubes or power electronic elements with controllable on-off functions; The power electronic component with controllable on-off function is a thyristor or an insulated gate bipolar transistor.

9. The voltage regulation method for a single isolating contact transition circuit of an on-load tap changer according to claim 7, characterized in that: The first switch element and the second switch element are used to interrupt the load current; the third switch element and the fourth switch element are used to interrupt the inter-stage circulating current; The first transition resistor and the second transition resistor are used to limit the inter-stage circulating current when the first winding tap and the second winding tap of the transformer voltage regulating winding are bridged.

10. The voltage regulating method for a single isolating contact transition circuit of an on-load tap changer according to claim 7, characterized in that: When the first main through-current switch, the first switching element and the third switching element are all in the on state; the moving contact of the transfer switch is connected to the first static contact, and the second main through-current switch, the second switching element and the fourth switching element are all in the off state, the transition circuit can enable the load current to flow from the first winding tap through the first main through-current switch and out from the neutral point lead-out end; when the second main through-current switch, the second switching element and the fourth switching element are all in the on state; the moving contact of the transfer switch is connected to the second static contact; and the first main through-current switch, the first switching element and the third switching element are all in the off state, the transition circuit can enable the load current to flow from the second winding tap through the second main through-current switch and out from the neutral point lead-out end.

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