A transition circuit and voltage regulation method for an on-load tap-changer without conversion contacts

Abstract

The present invention discloses a transition circuit and a voltage regulation method for a on-load tap-changer without a conversion contact, belonging to the technical field of on-load tap-changers. Taking a single-break vacuum tube as an example, the transition circuit includes: a first main current-carrying switch, a second main current-carrying switch, a first vacuum tube, a second vacuum tube, a third vacuum tube, a fourth vacuum tube, and a transition resistor. The first vacuum tube and the second vacuum tube take turns to undertake the task of breaking the load current, and the third vacuum tube and the fourth vacuum tube take turns to undertake the task of breaking the inter-stage circulating current, and the switching program is symmetric; the transition circuit is completely composed of switching elements and a transition resistor, avoiding the problem of arc extinction in oil caused by using a mechanical contact conversion switch, thereby effectively improving the safety and electrical life of the on-load tap-changer.

Description

Technical Field

[0001] The present invention relates to the technical field of on-load tap changers, and particularly relates to a transition circuit and a voltage regulation method for an on-load tap changer without a conversion contact. Background Art

[0002] An on-load tap changer is a key component inside a power transformer and can operate under the excitation or load state of the transformer. By changing several taps led out from the transformer winding, the effective turns ratio is changed, so as to adjust the output voltage without interrupting the load current. The on-load tap changer has a wide range of applications, especially in the converter transformers of UHV DC transmission projects to ensure the rated trigger angle of the converter during normal operation. 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. For this type of oil-immersed on-load tap changer, the switching is frequent, and the arc contacts are correspondingly severely burned, and the carbonization and pollution speed of the oil are relatively fast, thus increasing the daily maintenance and regular overhaul workload for the power supply department. The vacuum on-load tap changer mainly uses vacuum tubes to extinguish the arc, avoiding the carbonization and pollution of the oil caused by arc extinguishing in the 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. The power electronic on-load tap changer replaces the vacuum tube with power electronic components to achieve no open-circuit arc operation during the on-load switching process.

[0003] The 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. Its core is to adopt a transition circuit. The vacuum on-load tap changer can be divided into a single-contact circuit, a double-contact circuit, a triple-contact circuit and a quadruple-contact circuit according to the number of its vacuum tubes; there are two types of single-resistance and double-resistance transitions according to the number of its transition resistors; there are single-break and double-break contacts according to the number of its contact breaks; the above various combinations can form different types of transition circuits for the vacuum on-load tap changer. 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 for realizing on-load voltage regulation, and the switching tasks of each switching element will also be different. The topological structure of the transition circuit has an obvious impact on the reliability of the on-load tap changer switching process, as well as the failure rate and electrical life of the switch.

[0004] The existing on-load tap changers all adopt oil-immersed mechanical contact switches, which are likely to cause the mechanical structure of the switching switch to be complex in action. Once there is a timing coordination error, it will inevitably lead to the arc extinguishing of the switching switch in the oil. After multiple arc extinguishings in the oil, the transformer oil will be severely polluted, carbon produced and accumulated, and the insulation performance will be reduced, and then the arc in the oil cannot be extinguished, posing a great safety risk. Summary of the Invention

[0005] The object of the present invention is to provide a transition circuit and a voltage regulation method for an on-load tap-changer without conversion contacts, so as to overcome the defects existing in the prior art. The transition circuit of the present invention realizes on-load switching voltage regulation completely by switching elements and transition resistors, avoiding the problem of arc extinction in oil caused by using a mechanical contact switch, thereby improving the reliability and electrical life of the on-load tap-changer.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A transition circuit for an on-load tap-changer without conversion contacts, taking a single-break vacuum tube as an example for the switching element. The transition circuit includes: a first main current-carrying switch, a second main current-carrying switch, a first vacuum tube, a second vacuum tube, a third vacuum tube, a fourth vacuum tube, and a transition resistor;

[0008] Wherein, one end of the first main current-carrying switch is connected to the first winding tap of the transformer voltage regulating winding; one end of the second main current-carrying switch is connected to the second winding tap of the transformer voltage regulating winding; one end of the third vacuum tube is respectively connected to the first winding tap of the transformer voltage regulating winding and the first main current-carrying switch, and the other end is respectively connected to the first vacuum tube and the transition resistor; one end of the first vacuum tube is respectively connected to the third vacuum tube and the transition resistor; one end of the fourth vacuum tube is respectively connected to the second winding tap of the transformer voltage regulating winding and the second main current-carrying switch, and the other end is respectively connected to the second vacuum tube and the transition resistor; one end of the second vacuum tube is respectively connected to the fourth vacuum tube and the transition resistor; one end of the transition resistor is respectively connected to the third vacuum tube and the first vacuum tube, and the other end is respectively connected to the fourth vacuum tube and the second vacuum tube; the other ends of the first main current-carrying switch, the second main current-carrying switch, the first vacuum tube, and the second vacuum tube are all connected to the neutral point lead-out end of the on-load tap-changer.

[0009] During the reciprocating switching process of the on-load tap-changer transition circuit, the first vacuum tube and the second vacuum tube take turns to undertake the task of interrupting the load current, and the third vacuum tube and the fourth vacuum tube take turns to undertake the task of interrupting the inter-stage circulating current, thereby 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; at the same time, since the transition circuit is completely composed of switching elements and transition resistors, there is no problem of arc extinction in oil, improving the reliability and electrical life of the on-load tap-changer.

[0010] Preferably, when the first main current-carrying switch, the third vacuum tube, the first vacuum tube, and the second vacuum tube are all in the conducting state, and the second main current-carrying switch and the fourth vacuum tube 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 end through the first main current-carrying switch.

[0011] Preferably, when the second main current-carrying switch, the first vacuum tube, the fourth vacuum tube, and the second vacuum tube are all in the conducting state, and the first main current-carrying switch and the third vacuum tube are both in the off state, the on-load tap-changer transition circuit can make the load current flow out from the neutral point terminal through the second main current-carrying switch.

[0012] Preferably, the internal switching elements in the on-load tap-changer transition circuit without conversion contacts can be replaced by power electronic elements with controllable on-off functions (including thyristor switches or insulated gate bipolar transistor switches) and double-break vacuum tubes instead of single-break vacuum tubes.

[0013] A voltage regulation method for an on-load tap-changer transition circuit without conversion contacts is illustrated by taking a single-break vacuum tube as an example. When the on-load tap-changer switches from the current transformer winding tap to the preselected new transformer winding tap, that is, the switching process from the first winding tap to the second winding tap is as follows:

[0014] The first main current-carrying switch, the third vacuum tube, the first vacuum tube, and the second vacuum tube are all in the conducting state, and the second main current-carrying switch and the fourth vacuum tube are both in the off state;

[0015] Disconnect the first main current-carrying switch;

[0016] Disconnect the first vacuum tube to generate an arc;

[0017] After the first vacuum tube is completely extinguished, turn on the fourth vacuum tube;

[0018] Disconnect the third vacuum tube to generate an arc;

[0019] After the third vacuum tube is completely extinguished, turn on the first vacuum tube;

[0020] Turn on the second main current-carrying switch to make the load current I N flow out from the second winding tap through the second main current-carrying switch from the neutral point, and the switching process of the on-load tap-changer from the first winding tap to the second winding tap ends.

[0021] The switching process of the on-load tap-changer from the second winding tap to the first winding tap is as follows:

[0022] The second main current-carrying switch, the first vacuum tube, the fourth vacuum tube, and the second vacuum tube are all in the conducting state, and the first main current-carrying switch and the third vacuum tube are both in the off state;

[0023] Disconnect the second main current-carrying switch;

[0024] Disconnect the second vacuum tube to generate an arc;

[0025] After the second vacuum tube is completely extinguished, turn on the third vacuum tube;

[0026] Disconnect the fourth vacuum tube to generate an arc;

[0027] After the fourth vacuum tube is completely extinguished, turn on the second vacuum tube;

[0028] Turn on the first main current-carrying switch so that the load current I N flows out from the first winding tap through the first main current-carrying switch from the neutral point, and the switching process of the on-load tap-changer from the second winding tap to the first winding tap ends.

[0029] When the internal switching elements in the transition circuit of the on-load tap-changer without conversion contacts are power electronic elements with controllable on-off functions (including thyristor switches or insulated gate bipolar transistor switches) and double-break vacuum tubes, the action timing and voltage regulation method of the switching elements are the same and will not be elaborated here.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The transition circuit of the present invention is completely composed of switching elements and transition resistors, and there is no problem of arc extinction in oil; the first vacuum tube and the second vacuum tube take turns to undertake the task of breaking the load current, and the third vacuum tube and the fourth vacuum tube take turns to undertake the task of breaking the inter-stage circulating current. The switching program is symmetric, which reduces the working loss degree of a single switching element, balances the switching capacity between the switching elements, and reduces the failure rate of the switching elements; only one transition resistor is used in the transition circuit, and the circuit is simple, which is convenient for design and installation and ensures the insulation distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 is the circuit diagram of the on-load tap-changer transition circuit according to the embodiment of the present invention;

[0034] Figure 2 is the schematic diagram of the switching process of the on-load tap-changer transition circuit according to the embodiment of the present invention;

[0035] Figure 3 is the schematic diagram of the switching process of the on-load tap-changer transition circuit according to the embodiment of the present invention;

[0036] Figure 4Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0038] Figure 6 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0039] Figure 7 Schematic diagram of the switching process of the on-load tap-changer transition circuit according to an embodiment of the present invention;

[0040] Figure 8 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 switching from winding tap N to winding tap N + 1;

[0041] Figure 9 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 switching from winding tap N + 1 to winding tap N;

[0042] Figure 10 Circuit diagram of the on-load tap-changer transition circuit without conversion contacts with power electronic components as the switching elements according to an embodiment of the present invention;

[0043] Figure 11 Circuit diagram of the on-load tap-changer transition circuit without conversion contacts with double-break vacuum tubes as the switching elements according to an embodiment of the present invention. Detailed implementation manners

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] 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 with reference to 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.

[0046] It should be noted that the terms "first", "second", etc. in the description, claims and the above drawings of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. 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 that includes 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.

[0047] Figure 1 It is a circuit diagram of a tap-changer transition circuit without a transfer contact according to an embodiment of the present invention. As Figure 1As shown in the figure, the present invention provides a transition circuit and a voltage regulation method for a on-load tap-changer without a conversion contact. The transition circuit is completely composed of switching elements and a transition resistor, and there is no problem of arc extinction in oil. The first vacuum tube V1 and the second vacuum tube V2 take turns to undertake the task of breaking the load current, and the third vacuum tube V3 and the fourth vacuum tube V4 take turns to undertake the task of breaking the inter-stage circulating current. The switching program is symmetrical, which reduces the working burnout degree of a single switching element, balances the switching capacity between the switching elements, and reduces the failure rate of the switching elements. Only one transition resistor is used in the transition circuit, and the circuit is simple, which is convenient for design and installation and ensures the insulation distance. For the transition circuit of the on-load tap-changer without a conversion contact of the present invention, the switching elements are illustrated by taking a single-break vacuum tube as an example, and include a first main current-carrying switch MC1, a second main current-carrying switch MC2, a third vacuum tube V3, a first vacuum tube V1, a fourth vacuum tube V4, a second vacuum tube V2, and a transition resistor R. Wherein, one end of the first main current-carrying switch MC1 is connected to the first winding tap N of the transformer voltage regulating winding; one end of the second main current-carrying switch MC2 is connected to the second winding tap N+1 of the transformer voltage regulating winding; one end of the third vacuum tube V3 is respectively connected to the first winding tap N of the transformer voltage regulating winding and the first main current-carrying switch MC1, and the other end is respectively connected to the first vacuum tube V1 and the transition resistor R; one end of the first vacuum tube V1 is respectively connected to the third vacuum tube V3 and the transition resistor R; one end of the fourth vacuum tube V4 is respectively connected to the second winding tap N+1 of the transformer voltage regulating winding and the second main current-carrying switch MC2, and the other end is respectively connected to the second vacuum tube V2 and the transition resistor R; one end of the second vacuum tube V2 is respectively connected to the fourth vacuum tube V4 and the transition resistor R; one end of the transition resistor R is respectively connected to the third vacuum tube V3 and the first vacuum tube V1, and the other end is respectively connected to the fourth vacuum tube V4 and the second vacuum tube V2; the other ends of the first main current-carrying switch MC1, the second main current-carrying switch MC2, the first vacuum tube V1, and the second vacuum tube V2 are all connected to the neutral point lead-out end of the on-load tap-changer. During the reciprocating switching process, the first vacuum tube V1 and the second vacuum tube V2 take turns to undertake the task of breaking the load current, and the third vacuum tube V3 and the fourth vacuum tube V4 take turns to undertake the task of breaking the inter-stage circulating current, thereby 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. At the same time, since the transition circuit is completely composed of switching elements and a transition resistor, there is no problem of arc extinction in oil, which improves the reliability and electrical life of the on-load tap-changer.

[0048] When the first main current-carrying switch MC1, the third vacuum tube V3, the first vacuum tube V1, and the second vacuum tube V2 are all in the conducting state, and the second main current-carrying switch MC2 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 end through the first main current-carrying switch MC1.

[0049] When the second main current-carrying switch MC2, the first vacuum tube V1, the fourth vacuum tube V4, and the second vacuum tube V2 are all in the conducting state, and the first main current-carrying switch MC1 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.

[0050] The internal switching elements in the on-load tap-changer transition circuit without conversion contacts can be replaced by power electronic elements with controllable on-off functions (including thyristor switches or insulated gate bipolar transistor switches) and double-break vacuum tubes instead of single-break vacuum tubes.

[0051] A voltage regulation method for the on-load tap-changer transition circuit without conversion contacts is illustrated by taking a single-break vacuum tube as an example; when the on-load tap-changer switches from winding tap N to winding tap N + 1, the voltage regulation method is as follows:

[0052] As Figure 1 shown, the first main current-carrying switch MC1, the third vacuum tube V3, the first vacuum tube V1, and the second vacuum tube V2 are all in the conducting state, and the second main current-carrying switch MC2 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.

[0053] As Figure 2 shown, the first main current-carrying switch MC1 is turned off, the second main current-carrying switch MC2 remains off, the third vacuum tube V3, the first vacuum tube V1, and the second vacuum tube V2 remain conducting, and the fourth vacuum tube V4 remains off. The winding tap N continues to be connected, and the load current flows out from the neutral point lead-out terminal through the third vacuum tube V3 and the first vacuum tube V1.

[0054] As Figure 3 shown, the first main current-carrying switch MC1 remains off, the second main current-carrying switch MC2 remains off, the first vacuum tube V1 is turned off to generate an arc, the third vacuum tube V3 and the second vacuum tube V2 remain conducting, and the fourth vacuum tube V4 remains off. The winding tap N continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal through the third vacuum tube V3, the transition resistor R, and the second vacuum tube V2.

[0055] As Figure 4 shown, the first main current-carrying switch MC1 remains off, the second main current-carrying switch MC2 remains off. After the arc in the first vacuum tube V1 is completely extinguished, the fourth vacuum tube V4 is turned on, and the third vacuum tube V3 and the second vacuum tube V2 remain conducting. Both the winding tap N and the winding tap N + 1 are connected, and the load current I NFlow out from the neutral point lead through the fourth vacuum tube V4 and the second vacuum tube V2; the transition circuit forms a bridge connection to generate an inter-stage circulating current I C ; the current flowing through the third vacuum tube V3 is the inter-stage circulating current I C ; the current flowing through the second vacuum tube V2 is the load current I N ; the current I V flowing through the fourth vacuum tube V4 N = I C - I C ; where I S = U S / R, and the U

[0056] As Figure 5 shown, the first main current-carrying switch MC1 remains open, the second main current-carrying switch MC2 remains open, the third vacuum tube V3 is disconnected to generate an arc, the first vacuum tube V1 remains open, and the fourth vacuum tube V4 and the second vacuum tube V2 remain conducting. The winding tap N + 1 continues to be connected, and the load current continues to flow out from the neutral point lead through the fourth vacuum tube V4 and the second vacuum tube V2

[0057] As Figure 6 shown, the first main current-carrying switch MC1 remains open, the second main current-carrying switch MC2 remains open. After the arc in the third vacuum tube V3 is completely extinguished, the first vacuum tube V1 is made conducting, the third vacuum tube V3 remains open, and the fourth vacuum tube V4 and the second vacuum tube V2 remain conducting. The winding tap N + 1 continues to be connected, and the load current continues to flow out from the neutral point lead through the fourth vacuum tube V4 and the second vacuum tube V2

[0058] As Figure 7 shown, the first main current-carrying switch MC1 remains open, the second main current-carrying switch MC2 is made conducting, the third vacuum tube V3 remains open, and the first vacuum tube V1, the fourth vacuum tube V4, and the second vacuum tube V2 remain conducting. The winding tap N + 1 is connected, and the load current flows out from the neutral point lead through the second main current-carrying switch MC2

[0059] 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 of the on-load tap-changer from the winding tap N to the winding tap N + 1. The specific voltage regulation method is as follows:

[0060] The second main current-carrying switch MC2, the first vacuum tube V1, the fourth vacuum tube V4, and the second vacuum tube V2 are all in the conducting state, and the first main current-carrying switch MC1 and the third vacuum tube V3 are both in the open state; the winding tap N + 1 is connected, and the load current flows out from the neutral point lead through the second main current-carrying switch MC2

[0061] Disconnect the second main current-carrying switch MC2, keep the first main current-carrying switch MC1 disconnected, keep the first vacuum tube V1, the fourth vacuum tube V4, and the second vacuum tube V2 conducting, and keep the third vacuum tube V3 disconnected. The winding tap N+1 continues to be connected, and the load current flows out from the neutral point lead-out terminal through the fourth vacuum tube V4 and the second vacuum tube V2.

[0062] Keep the first main current-carrying switch MC1 disconnected, keep the second main current-carrying switch MC2 disconnected, disconnect the second vacuum tube V2 to generate an arc, keep the first vacuum tube V1 and the fourth vacuum tube V4 conducting, and keep the third vacuum tube V3 disconnected. The winding tap N+1 continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal through the fourth vacuum tube V4, the transition resistor R, and the first vacuum tube V1.

[0063] Keep the first main current-carrying switch MC1 disconnected, keep the second main current-carrying switch MC2 disconnected. After the arc in the second vacuum tube V2 is completely extinguished, turn on the third vacuum tube V3, and keep the first vacuum tube V1 and the fourth vacuum tube V4 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 and the first vacuum tube V1; the transition circuit forms a bridge connection to generate an inter-stage circulating current I C ; the current flowing through the fourth vacuum tube V4 is the inter-stage circulating current I C ; the current flowing through the first vacuum tube V1 is the load current I N ; the current flowing through the third vacuum tube V3 is I V = I N + I C ; where I C = U S / R, and the U S is the on-load tap-changer step voltage.

[0064] Keep the first main current-carrying switch MC1 disconnected, keep the second main current-carrying switch MC2 disconnected, disconnect the fourth vacuum tube V4 to generate an arc, keep the second vacuum tube V2 disconnected, and keep the third vacuum tube V3 and the first vacuum tube V1 conducting. The winding tap N is connected, and the load current flows out from the neutral point lead-out terminal through the third vacuum tube V3 and the first vacuum tube V1.

[0065] Keep the first main current-carrying switch MC1 disconnected, keep the second main current-carrying switch MC2 disconnected. After the arc in the fourth vacuum tube V4 is completely extinguished, turn on the second vacuum tube V2, keep the fourth vacuum tube V4 disconnected, and keep the third vacuum tube V3 and the first vacuum tube V1 conducting. The winding tap N continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal through the third vacuum tube V3 and the first vacuum tube V1.

[0066] Turn on the first main current-carrying switch MC1, keep the second main current-carrying switch MC2 off, keep the fourth vacuum tube V4 off, and keep the third vacuum tube V3, the first vacuum tube V1, and the second vacuum tube V2 on. The winding tap N is connected, and the load current flows out from the neutral point lead through the first main current-carrying switch MC1.

[0067] When the internal switch elements in the on-load tap-changer transition circuit without conversion contacts are power electronic components with controllable on-off functions (including thyristor switches or insulated gate bipolar transistor switches) and double-break vacuum tubes, the action timing and voltage regulation method of the switch elements are the same and will not be elaborated here.

[0068] When the on-load tap-changer switches from the winding N tap connection to the winding N + 1 tap connection, the schematic diagram of the transition circuit conversion procedure is as Figure 8 shown;

[0069] When the on-load tap-changer switches from the winding N + 1 tap connection to the winding N tap connection, the schematic diagram of the transition circuit conversion procedure is as Figure 9 shown;

[0070] 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:

[0071]

[0072] Among them, I N is the load current; U S is the on-load tap-changer step voltage; R is the transition resistance.

[0073] Figure 10 is the circuit diagram of the on-load tap-changer transition circuit without conversion contacts with power electronic components as the switch elements according to the embodiment of the present invention, as Figure 10 shown. Only replace the single-break vacuum tube in Figure 1 with a power electronic component with controllable on-off. Other components are the same as those in Figure 1 , the action timing is the same, and the function and role are the same as those of the transition circuit shown in Figure 1 and will not be elaborated here.

[0074] Figure 11 is the circuit diagram of the on-load tap-changer transition circuit without conversion contacts with double-break vacuum tubes as the switch elements according to the embodiment of the present invention; as Figure 11 shown. Only replace the single-break vacuum tube in Figure 1 with a double-break vacuum tube. Other components are the same as those in Figure 1 , the action timing is the same, and the function and role are the same as those of the transition circuit shown in Figure 1 and will not be elaborated here.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of its protection. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that after reading the present invention, various changes, modifications or equivalent substitutions can still be made to the specific implementation manners of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A transition circuit for an on-load tap-changer without transfer contacts, characterized in that, Including: A first main current-carrying switch (MC1), a second main current-carrying switch (MC2), a first vacuum tube (V1), a second vacuum tube (V2), a third vacuum tube (V3), a fourth vacuum tube (V4), and a transition resistor (R); Wherein, one end of the first main current-carrying switch (MC1) is connected to the first winding tap (N) of the transformer voltage regulating winding; one end of the second main current-carrying switch (MC2) is connected to the second winding tap (N + 1) of the transformer voltage regulating winding; one end of the third vacuum tube (V3) is respectively connected to the first winding tap (N) of the transformer voltage regulating winding and one end of the first main current-carrying switch (MC1), and the other end of the third vacuum tube (V3) is respectively connected to one end of the first vacuum tube (V1) and one end of the transition resistor (R); one end of the fourth vacuum tube (V4) is respectively connected to the second winding tap (N + 1) of the transformer voltage regulating winding and one end of the second main current-carrying switch (MC2), and the other end of the fourth vacuum tube (V4) is respectively connected to one end of the second vacuum tube (V2) and the other end of the transition resistor (R); the other ends of the first main current-carrying switch (MC1), the second main current-carrying switch (MC2), the first vacuum tube (V1), and the second vacuum tube (V2) are all connected to the neutral point lead-out end of the on-load tap-changer; The following method is used to realize the switching from the first winding tap (N) to the second winding tap (N + 1), including: The first main current-carrying switch (MC1), the third vacuum tube (V3), the first vacuum tube (V1), and the second vacuum tube (V2) are all in the conducting state, and the second main current-carrying switch (MC2) and the fourth vacuum tube (V4) are all in the off state; Disconnect the first main current-carrying switch (MC1); Disconnect the first vacuum tube (V1) to generate an arc; After the first vacuum tube (V1) is completely extinguished, conduct the fourth vacuum tube (V4); Disconnect the third vacuum tube (V3) to generate an arc; After the third vacuum tube (V3) is completely extinguished, conduct the first vacuum tube (V1); Turn on the second main current-carrying switch (MC2) to make the load current I N flow out from the neutral point through the second main current-carrying switch (MC2) from the second winding tap (N + 1), and the switching process of the on-load tap-changer from the first winding tap (N) to the second winding tap (N + 1) ends; The following method is used to realize the switching from the second winding tap (N + 1) to the first winding tap (N), including: The second main current-carrying switch (MC2), the first vacuum tube (V1), the fourth vacuum tube (V4), and the second vacuum tube (V2) are all in the conducting state, and the first main current-carrying switch (MC1) and the third vacuum tube (V3) are all in the off state; Disconnect the second main current-carrying switch (MC2); Disconnect the second vacuum tube (V2) to generate an arc; After the second vacuum tube (V2) is completely extinguished, conduct the third vacuum tube (V3); Disconnect the fourth vacuum tube (V4) to generate an arc; After the fourth vacuum tube (V4) is completely extinguished, conduct the second vacuum tube (V2); Turn on the first main current-carrying switch (MC1) to make the load current I N flow out from the neutral point through the first main current-carrying switch (MC1) from the first 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.

2. The on-load tap-changer transition circuit without a conversion contact according to claim 1, wherein When the first main current-carrying switch (MC1), the third vacuum tube (V3), the first vacuum tube (V1), and the second vacuum tube (V2) are all in the conducting state, and the second main current-carrying switch (MC2) and the fourth vacuum tube (V4) are both 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).

3. The on-load tap-changer transition circuit without a conversion contact according to claim 1, characterized in that, When the second main current-carrying switch (MC2), the first vacuum tube (V1), the fourth vacuum tube (V4), and the second vacuum tube (V2) are all in the conducting state, and the first main current-carrying switch (MC1) and the third vacuum tube (V3) are both 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).

4. The on-load tap-changer transition circuit without conversion contacts according to claim 1, characterized in that, The first vacuum tube (V1), the second vacuum tube (V2), the third vacuum tube (V3), and the fourth vacuum tube (V4) adopt single-break vacuum tubes or double-break vacuum tubes, and the first vacuum tube (V1), the second vacuum tube (V2), the third vacuum tube (V3), and the fourth vacuum tube (V4) can be replaced by power electronic components with controllable on-off functions.

5. A voltage regulation method using the on-load tap-changer transition circuit without a conversion contact according to any one of claims 1-4, characterized in that, When the first main current-carrying switch (MC1), the third vacuum tube (V3), the first vacuum tube (V1), and the second vacuum tube (V2) are all in the conducting state, and the second main current-carrying switch (MC2) and the fourth vacuum tube (V4) are both in the off state, the on-load tap-changer transition circuit makes the load current flow out from the first winding tap (N) through the first main current-carrying switch (MC1) from the neutral point, and the on-load tap-changer switches from the second winding tap (N + 1) to the first winding tap (N); When the second main current-carrying switch (MC2), the first vacuum tube (V1), the fourth vacuum tube (V4), and the second vacuum tube (V2) are all in the conducting state, and the first main current-carrying switch (MC1) and the third vacuum tube (V3) are both in the off state, the on-load tap-changer transition circuit makes the load current flow out from the second winding tap (N + 1) through the second main current-carrying switch (MC2) from the neutral point, and the on-load tap-changer switches from the first winding tap (N) to the second winding tap (N + 1).

6. The voltage regulation method of the transition circuit of the on-load tap-changer without conversion contacts according to claim 5, characterized in that When switching from the first winding tap (N) to the second winding tap (N + 1), it includes:[[]]END]] The first main current-carrying switch (MC1), the third vacuum tube (V3), the first vacuum tube (V1), and the second vacuum tube (V2) are all in the conducting state, and the second main current-carrying switch (MC2) and the fourth vacuum tube (V4) are both in the off state; Disconnect the first main current-carrying switch (MC1); Disconnect the first vacuum tube (V1) to generate an arc; After the first vacuum tube (V1) is completely extinguished, turn on the fourth vacuum tube (V4); Disconnect the third vacuum tube (V3) to generate an arc; After the third vacuum tube (V3) is completely extinguished, turn on the first vacuum tube (V1); Turn on the second main current-carrying switch (MC2) to make the load current I N flow out from the neutral point through the second main current-carrying switch (MC2) from the second winding tap (N + 1), and the switching process of the on-load tap-changer from the first winding tap (N) to the second winding tap (N + 1) ends.

7. A voltage regulation method for a transition circuit of an on-load tap-changer without a conversion contact according to claim 5, characterized in that, When switching from the second winding tap (N + 1) to the first winding tap (N), it includes:[[]]END]] The second main current-carrying switch (MC2), the first vacuum tube (V1), the fourth vacuum tube (V4), and the second vacuum tube (V2) are all in the conducting state, while the first main current-carrying switch (MC1) and the third vacuum tube (V3) are both in the off state; Disconnect the second main current-carrying switch (MC2); Disconnect the second vacuum tube (V2) to generate an arc; After the second vacuum tube (V2) is completely extinguished, turn on the third vacuum tube (V3); Disconnect the fourth vacuum tube (V4) to generate an arc; After the fourth vacuum tube (V4) is completely extinguished, turn on the second vacuum tube (V2); Turn on the first main current-carrying switch (MC1) to make the load current I N flow out from the neutral point through the first main current-carrying switch (MC1) from the first 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.

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