A single-resistance symmetrical transition circuit and voltage regulation method for an on-load tap changer

Abstract

The present invention discloses a single-resistance symmetrical transition circuit and voltage regulation method for an on-load tap changer. The transition circuit includes: a first main contact, a second main contact, a main vacuum contact, a first auxiliary vacuum contact, a second auxiliary vacuum contact, a first isolating switch, a second isolating switch, a conversion switch and a transition resistor. There are two auxiliary switch elements in the transition circuit, which take turns to interrupt the inter-pole circulating current during the on-load switching process. The switching process is symmetrical, and the two auxiliary switch elements have the same task of interrupting the current, which reduces the switching loss of the auxiliary switch elements and can balance the switching capacity of the main switch elements and the auxiliary switch elements. Only one transition resistor is used in the transition circuit, which is convenient for design and installation and ensures the insulation distance. Two isolating switches are designed, which can not only play an electrical isolation role, but also serve as a protection switch for the auxiliary switch elements to prevent the failure of the auxiliary switch elements to interrupt the current after failure.

Description

Technical Field

[0001] The invention relates to the technical field of on-load tap changers, and in particular to a single-resistance symmetrical transition circuit and a voltage regulation method for an on-load tap changer. Background Art

[0002] The on-load tap changer is a key component inside the power transformer. It can operate under the transformer excitation or load state. By changing the number of taps connected to the transformer winding, the effective turns ratio is changed 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 transformer of the UHV DC transmission project 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 principle of high-speed resistance switching and relied on copper-tungsten arc contacts for load conversion. This type of oil-immersed non-vacuum on-load tap changer is frequently switched, and the arc contact burns more seriously. The carbonization and pollution of the oil are fast, which increases the workload of daily maintenance and regular inspection for the power supply department. The vacuum on-load tap changer mainly uses vacuum tubes to achieve arc extinguishing, avoiding the carbonization and pollution of the oil caused by the arc extinguishing in the oil; due to the short arc breaking time, low arc voltage, low arc energy consumption and recondensation of contact metal vaporization, the contact burnout and corrosion can be minimized. The power electronic on-load tap-changer replaces the vacuum tube with power electronic components to achieve arc-free operation during on-load switching.

[0003] The on-load tap changer consists of a transfer switch, a tap selector and an electric mechanism. The transfer switch has an independent oil chamber and is the key component for the tap changer to achieve on-load switching. Its core is the use of a transition circuit. Vacuum on-load tap changers can be divided into single-contact circuits, double-contact circuits, three-contact circuits and four-contact circuits according to the number of vacuum tubes; there are single-resistance and double-resistance transitions according to the number of transition resistors; there are single-break and double-break according to the number of contact breaks; the above combinations can constitute 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 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.

[0004] In the transition circuit of the on-load tap changer, there are main on-off switch elements that only bear the task of breaking load current and auxiliary switch elements that only bear the task of breaking inter-stage circulating current. In the actual UHV DC transmission project, the load current flowing through the on-load tap changer of the converter transformer is about 500-600A, and the inter-stage circulating current flowing through the transition resistor during the switching process is about 900-1000A. The circulating current broken by the auxiliary switch element at a single time is significantly greater than the load current broken by the main on-off switch element, resulting in an unbalanced breaking task between the auxiliary switch element and the main on-off switch element. Summary of the invention

[0005] The present invention proposes a single-resistance symmetrical transition circuit and a voltage regulation method for an on-load tap changer, wherein the components are symmetrically distributed and the switching sequence is symmetrical, the reliability and switching efficiency of the on-load tap changer can be improved, and the circuit has the advantages of less transition resistance and alternate load of auxiliary switch components.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A single-resistance symmetrical transition circuit of an on-load tap changer, comprising: a first main contact, a second main contact, a main vacuum contact, a first auxiliary vacuum contact, a second auxiliary vacuum contact, a first isolating switch, a second isolating switch, a transfer switch, a transition resistor, a first winding tap of a transformer voltage regulating winding, a second winding tap of the transformer voltage regulating winding, and a neutral point lead-out terminal of the on-load tap changer;

[0008] Among them, the first main contact, the first auxiliary vacuum contact and the first static contact in the transfer switch are connected to the first winding tap of the transformer voltage regulating winding, the other end of the first auxiliary vacuum contact is connected to one end of the first isolating switch, the second auxiliary vacuum contact, one end of the second main contact and the second static contact in the transfer switch are connected to the second winding tap of the transformer voltage regulating winding, one end of the main vacuum contact is connected to the moving contact in the transfer switch, the other end of the second auxiliary vacuum contact is connected to one end of the second isolating switch, the other ends of the first isolating switch and the second isolating switch are connected to one end of the transition resistor, and the other ends of the first main contact, the main vacuum contact, the transition resistor and the second main contact are all connected to the neutral point lead-out terminal of the on-load tap changer.

[0009] Furthermore, when the first main contact is turned on, the second main contact is turned off, the main vacuum contact is turned on, the first auxiliary vacuum contact is turned off from the second auxiliary vacuum contact, the moving contact in the transfer switch is connected to the first static contact, the first isolating switch is turned on, and the second isolating switch is turned off, the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the first main contact.

[0010] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are disconnected, the moving contact in the transfer switch is connected to the first static contact, the first isolating switch is turned on, and the second isolating switch is disconnected, the first winding tap is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch and the main vacuum contact.

[0011] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are turned on, the moving contact in the transfer switch is connected to the first static contact, the first isolating switch is turned on, and the second isolating switch is disconnected, the first winding tap is connected, and the load current continues to flow out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch and the main vacuum contact.

[0012] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is disconnected, an arc is generated, the first auxiliary vacuum contact and the second auxiliary vacuum contact are turned on, the moving contact in the transfer switch is connected to the first static contact, the first isolating switch is turned on, and when the second isolating switch is disconnected, the first winding tap is connected, and the load current flows out through the first auxiliary vacuum contact, the first isolating switch, the transition resistor and the neutral point lead-out terminal of the on-load tap changer.

[0013] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is disconnected, the first auxiliary vacuum contact and the second auxiliary vacuum contact are turned on, and when the arc in the main vacuum contact is completely extinguished, the moving contact in the conversion switch is rotated to connect with the second static contact, the first isolating switch is turned on, and when the second isolating switch is disconnected, the first winding tap is connected, and the load current flows out through the first auxiliary vacuum contact, the first isolating switch, the transition resistor and the neutral point lead-out terminal of the on-load tap changer.

[0014] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are turned on, the moving contact in the transfer switch is connected to the second static contact, the first isolating switch is turned on, and the second isolating switch is disconnected, the first winding tap and the second winding tap are both connected, and the load current flows out through the transfer switch, the main vacuum contact and the neutral point lead-out terminal of the on-load tap changer.

[0015] Furthermore, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are disconnected, the moving contact in the transfer switch is connected to the second static contact, the first isolating switch is turned on, and the second isolating switch is disconnected, the second winding tap is connected, and the load current flows out through the transfer switch, the main vacuum contact and the neutral point lead-out terminal of the on-load tap changer.

[0016] Further, the first main contact is disconnected, the second main contact is disconnected, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are disconnected, the moving contact in the transfer switch is connected to the second static contact, and when the arc in the first auxiliary vacuum contact is completely extinguished, the first disconnector is disconnected, and when the second disconnector is turned on, the second winding tap is connected, and the load current flows out through the transfer switch, the main vacuum contact and the neutral point lead-out terminal of the on-load tap changer;

[0017] The first main contact is disconnected, the second main contact is turned on, the main vacuum contact is turned on, the first auxiliary vacuum contact and the second auxiliary vacuum contact are disconnected, the moving contact in the transfer switch is connected to the second static contact, the first isolating switch is disconnected, and the second isolating switch is turned on. The second winding tap is connected, and the load current flows out through the second main contact and the neutral point lead-out terminal of the on-load tap changer.

[0018] A voltage regulation method for a single-resistance symmetrical transition circuit of an on-load tap changer comprises the following steps:

[0019] The first main contact is turned on, the second main contact is turned off, the first auxiliary vacuum contact is turned off, the second auxiliary vacuum contact is turned off, the main vacuum contact is turned on, the first isolating switch is turned on, the second isolating switch is turned off, and when the conversion switch is connected to the first winding tap, the first main contact is turned off, the first auxiliary vacuum contact is turned on, the second auxiliary vacuum contact is turned on, and the main vacuum contact is turned off to generate an arc; after the main vacuum contact is completely extinguished, the conversion switch is controlled to connect the main vacuum contact to the second winding tap; then the main vacuum contact is turned on, the first auxiliary vacuum contact is turned off, and the second auxiliary vacuum contact is turned off to generate an arc; after the first auxiliary vacuum contact is completely extinguished, the first isolating switch is turned off and the second isolating switch is turned on; the second main contact is turned on to allow the load current to flow out from the second winding tap through the second main contact from the neutral point lead-out terminal of the on-load tap changer;

[0020] The second main contact is turned on, the first main contact is turned off, the first auxiliary vacuum contact is turned off, the second auxiliary vacuum contact is turned off, the first disconnector is turned on, the main vacuum contact is turned on, the second disconnector is turned on, and when the conversion switch is connected to the second winding tap, the second main contact is turned off, the first auxiliary vacuum contact is turned on, and the second auxiliary vacuum contact is turned on; then the main vacuum contact is turned off to generate an arc; after the main vacuum contact is completely extinguished, the conversion switch is controlled to connect the main vacuum contact to the first winding tap; then the main vacuum contact is turned on, the first auxiliary vacuum contact is turned off, and the second auxiliary vacuum contact is turned off to generate an arc; after the second auxiliary vacuum contact is completely extinguished, the first disconnector is turned on, and the second disconnector is turned off; then the first main contact is turned on to allow the load current to flow out from the first winding tap through the first main contact from the neutral point lead-out terminal of the on-load tap changer.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention arranges a first auxiliary vacuum contact and a second auxiliary vacuum contact to alternately interrupt the inter-stage circulating current in the process of on-load switching. The switching process is symmetrical, and the first auxiliary vacuum contact and the second auxiliary vacuum contact have the same current interruption task, which reduces the switching loss of the auxiliary switch element and can balance the switching capacity between the first main contact and the first auxiliary vacuum contact and between the second main contact and the second auxiliary vacuum contact. Only one transition resistor is used, which is convenient for design and installation and ensures the insulation distance. By arranging two first isolating switches and the second isolating switches, both electrical isolation can be achieved and the auxiliary switch element can be used as a protection switch to prevent the failure of the auxiliary switch element to be unable to interrupt the current after failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0024] Figure 1 A circuit diagram of a transition circuit of an on-load tap changer according to the present invention;

[0025] Figure 2 It is a schematic diagram of the switching action of disconnecting the first main contact in the transition circuit of the on-load tap changer of the present invention;

[0026] Figure 3 It is a schematic diagram of the switching action of the auxiliary vacuum contact conducting in the transition circuit of the on-load tap changer of the present invention;

[0027] Figure 4 It is a schematic diagram of the switching action of disconnecting the main vacuum contact in the transition circuit of the on-load tap changer of the present invention;

[0028] Figure 5 It is a schematic diagram of the switching action of the transfer switch in the transition circuit of the on-load tap changer of the present invention;

[0029] Figure 6 It is a schematic diagram of the switching action of the main vacuum contact being turned on in the transition circuit of the on-load tap changer of the present invention;

[0030] Figure 7 It is a schematic diagram of the switching action of disconnecting the auxiliary vacuum contact in the transition circuit of the on-load tap changer of the present invention;

[0031] Figure 8 It is a schematic diagram of the switching action of the isolating switch in the transition circuit of the on-load tap changer of the present invention;

[0032] Fig. 9 It is a schematic diagram of the switching action of the second main contact being turned on in the transition circuit of the on-load tap changer of the present invention;

[0033] Fig.10It is a schematic diagram of the on-off of each switch in the transition circuit of the on-load tap changer of the present invention during the process of the load switching from winding tap N to winding tap N+1;

[0034] Fig.11 It is a schematic diagram of the on-off of each switch in the transition circuit of the on-load tap changer of the present invention during the process of the load switching from the winding tap N+1 to the winding tap N;

[0035] Fig.12 A circuit diagram of a single-resistance symmetrical transition circuit of an on-load tap changer in which the switch element is a power electronic element according to an embodiment of the present invention;

[0036] Fig.13 The circuit diagram is a single-resistance symmetrical transition circuit of an on-load tap changer whose switching element is a double-break vacuum contact according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, the present invention provides a single-resistance symmetrical transition circuit and a voltage regulation method for an on-load tap changer. There are two auxiliary switch elements in the transition circuit, which take turns to interrupt the inter-stage circulating current during the on-load switching process. The switching process is symmetrical, and the two auxiliary switch elements have the same current interruption task, which reduces the switching loss of the auxiliary switch elements and can balance the switching capacity of the main switch elements and the auxiliary switch elements. Only one transition resistor is used in the transition circuit, which is convenient for design and installation and ensures the insulation distance. Two isolating switches are designed, which can not only play an electrical isolation role, but also serve as protection switches for the auxiliary switch elements to prevent the failure of the auxiliary switch elements to interrupt the current after failure.

[0039] See also Figure 1 The switch element is explained by taking a single-break vacuum contact as an example. The single-resistance symmetrical transition circuit of the on-load tap changer includes: the first main contact MC1, the second main contact MC2, the main vacuum contact V1, the first auxiliary vacuum contact V2, the second auxiliary vacuum contact V3, the first isolating switch Z1, the second isolating switch Z2, the conversion switch T, the transition resistor R, the first winding tap N of the transformer voltage regulating winding, the second winding tap N+1 of the transformer voltage regulating winding, and the neutral point lead-out terminal of the on-load tap changer. The conversion switch T includes a moving contact, a first static contact 11 and a second static contact 12.

[0040] Among them, one end of the first main contact MC1 is connected to the first winding tap N of the transformer voltage regulating winding; one end of the second main contact MC2 is connected to the second winding tap N+1 of the transformer voltage regulating winding; one end of the main vacuum contact V1 is connected to the moving contact in the conversion switch T; one end of the first auxiliary vacuum contact V2 is respectively connected to the first winding tap N of the transformer voltage regulating winding and the first static contact 11 in the conversion switch T, and the other end is connected to one end of the first disconnector Z1; one end of the second auxiliary vacuum contact V3 is respectively connected to the second winding tap N+1 of the transformer voltage regulating winding and the second static contact 12 in the conversion switch T, and the other end is connected to one end of the second disconnector Z2; the other ends of the first disconnector Z1 and the second disconnector Z2 are both connected to one end of the transition resistor R; the other ends of the first main contact MC1, the second main contact MC2, the main vacuum contact V1 and the transition resistor R are all connected to the neutral point lead-out end of the on-load tap changer.

[0041] When the first main contact MC1, the main vacuum contact V1 and the first disconnector Z1 are all in the on state, the second disconnector Z2, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are all in the off state, and the conversion switch T is connected to the first winding tap N, the on-load tap changer transition circuit can make the load current flow out from the neutral point lead-out terminal of the on-load tap changer through the first main contact MC1.

[0042] When the second main contact MC2, the main vacuum contact V1 and the second isolating switch Z2 are all in the on state, the first isolating switch Z1, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are all in the off state, and the second static contact 12 in the conversion switch T is connected to the second winding tap N+1, the on-load tap changer transition circuit can make the load current flow out from the neutral point lead-out terminal of the on-load tap changer through the second main contact MC2.

[0043] The internal switch element in the single-resistance symmetrical transition circuit of the on-load tap changer can be replaced by a power electronic element with controllable on-off function (including a thyristor switch or an insulated gate bipolar transistor switch) and a double-break vacuum contact instead of a single-break vacuum contact.

[0044] A voltage regulation method for a single-resistance symmetrical transition circuit of an on-load tap changer is described by taking a single-break vacuum contact 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:

[0045] like Figure 1As shown, the first main contact MC1 is turned on, the second main contact MC2 is turned off, the main vacuum contact V1 is turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are turned off, the moving contact in the transfer switch T is connected to the first static contact 11, the first isolating switch Z1 is turned on, and the second isolating switch Z2 is turned off. The first winding tap N is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the first main contact MC1.

[0046] like Figure 2 As shown, the first main contact MC1 is disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, the moving contact in the transfer switch T remains connected to the first static contact 11, the first disconnector Z1 remains on, and the second disconnector Z2 remains off. The winding tap N continues to be connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0047] like Figure 3 As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are turned on, the moving contact in the transfer switch T remains connected to the first static contact 11, the first disconnector Z1 remains on, and the second disconnector Z2 remains off. The first winding tap N continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0048] like Figure 4 As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 is disconnected, an arc is generated, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain on, the moving contact in the transfer switch T remains connected to the first static contact 11, the first disconnector Z1 remains on, and the second disconnector Z2 remains off. The winding tap N continues to be connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the first auxiliary vacuum contact V2, the first disconnector Z1, and the transition resistor R.

[0049] like Figure 5As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains disconnected, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain on, and when the arc in the main vacuum contact V1 is completely extinguished, the moving contact in the transfer switch T is rotated to connect with the second static contact 12, the first disconnector Z1 remains on, and the second disconnector Z2 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 of the on-load tap changer through the first auxiliary vacuum contact V2, the first disconnector Z1, and the transition resistor R.

[0050] like Figure 6 As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 is turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain turned on, the moving contact in the transfer switch T remains connected to the second static contact 12, the first isolating switch Z1 remains turned on, and the second isolating switch Z2 remains disconnected. The winding tap N and the winding tap N+1 are both turned on, and the load current I N The current flows out from the neutral point of the on-load tap changer through the conversion switch T and the main vacuum contact V1; the transition circuit forms a bridge, generating an interstage circulating current I C The current flowing through the first auxiliary vacuum contact V2 is the interstage circulating current I C , the current I flowing through the main vacuum contact V1 V =I N -I C ; where I C =U S / R, U S is the on-load tapchanger level voltage.

[0051] like Figure 7 As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are disconnected, the moving contact in the transfer switch T remains connected to the second static contact 12, the first disconnector Z1 remains on, and the second disconnector Z2 remains off. The winding tap N+1 is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0052] like Figure 8As shown, the first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, and the moving contact in the transfer switch T remains connected to the second static contact 12. When the arc in the first auxiliary vacuum contact V2 is completely extinguished, the first disconnector Z1 is disconnected and the second disconnector Z2 is turned on. The winding tap N+1 is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0053] like Fig. 9 As shown, the first main contact MC1 remains disconnected, the second main contact MC2 is turned on, the main vacuum contact V1 remains turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, the moving contact in the transfer switch T remains connected to the second static contact 12, the first disconnector Z1 remains disconnected, and the second disconnector Z2 remains turned on. The winding tap N+1 is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the second main contact MC2.

[0054] The internal switch element in the single-resistance symmetrical transition circuit of the on-load tap changer can be replaced by a power electronic element with controllable on-off function (including a thyristor switch or an insulated gate bipolar transistor switch) and a double-break vacuum contact instead of a single-break vacuum contact.

[0055] Taking a single-break vacuum contact as an example, when the on-load tap changer switches from winding tap N+1 to winding tap N, the switching process is symmetrical with the switching process of the on-load tap changer switching from winding tap N to winding tap N+1. The voltage regulation method is as follows:

[0056] The first main contact MC1 is disconnected, the second main contact MC2 is turned on, the main vacuum contact V1 is turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are disconnected, the moving contact in the transfer switch T is connected to the second static contact 12, the first isolating switch Z1 is disconnected, and the second isolating switch Z2 is turned on. The winding tap N+1 is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the second main contact MC2.

[0057] The first main contact MC1 remains disconnected, the second main contact MC2 is disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, the moving contact in the transfer switch T remains connected to the second static contact 12, the first disconnector Z1 remains disconnected, and the second disconnector Z2 remains on. The winding tap N+1 continues to be connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0058] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are turned on, the moving contact in the transfer switch T remains connected to the second static contact 12, the first disconnector Z1 remains disconnected, and the second disconnector Z2 remains on. The winding tap N+1 continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0059] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 is disconnected, an arc is generated, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain on, the moving contact in the transfer switch T remains connected to the second static contact 12, the first disconnector Z1 remains disconnected, and the second disconnector Z2 remains on. The winding tap N+1 continues to be connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the second auxiliary vacuum contact V3, the second disconnector Z2, and the transition resistor R.

[0060] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains disconnected, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain on, and when the arc in the main vacuum contact V1 is completely extinguished, the moving contact in the transfer switch T is rotated to connect with the first static contact 11, the first isolating switch Z1 remains disconnected, and the second isolating switch Z2 remains on. The winding tap N+1 continues to be connected, and the load current continues to flow out from the neutral point lead-out terminal of the on-load tap changer through the second auxiliary vacuum contact V3, the second isolating switch Z2, and the transition resistor R.

[0061] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 is turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain turned on, the moving contact in the transfer switch T remains connected to the first static contact 11, the first isolating switch Z1 remains disconnected, and the second isolating switch Z2 remains turned on. The winding tap N and the winding tap N+1 are both turned on, and the load current I N The current flows out from the neutral point of the on-load tap changer through the conversion switch T and the main vacuum contact V1; the transition current forms a bridge, generating an inter-stage circulating current I C The current flowing through the second auxiliary vacuum contact V3 is the interstage circulating current I C , the current I flowing through the main vacuum contact V1 V =I N +I C ; where I C =U S / R, said U S is the on-load tapchanger level voltage.

[0062] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 are disconnected, the moving contact in the transfer switch T remains connected to the first static contact 11, the first disconnector Z1 remains disconnected, and the second disconnector Z2 remains on. The winding tap N is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0063] The first main contact MC1 remains disconnected, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, the moving contact in the transfer switch T remains connected to the first static contact 11, and when the arc in the second auxiliary vacuum contact V3 is completely extinguished, the first disconnector Z1 is turned on and the second disconnector Z2 is turned off. The winding tap N is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the transfer switch T and the main vacuum contact V1.

[0064] The first main contact MC1 is turned on, the second main contact MC2 remains disconnected, the main vacuum contact V1 remains turned on, the first auxiliary vacuum contact V2 and the second auxiliary vacuum contact V3 remain disconnected, the moving contact in the transfer switch T remains connected to the first static contact 11, the first disconnector Z1 remains turned on, and the second disconnector Z2 remains disconnected. The winding tap N is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the first main contact MC1.

[0065] When the internal switch element in the single-resistance symmetrical transition circuit of the on-load tap changer is a power electronic element with controllable on-off function (including a thyristor switch or an insulated gate bipolar transistor switch) and a double-break vacuum contact, the action timing and voltage regulation method of the switch element are consistent and will not be repeated.

[0066] In the embodiment of the present invention, the switching tasks of the transition circuit of the on-load tap changer using vacuum contacts are shown in Table 1 below:

[0067] Table 1 Switching tasks

[0068]

[0069] Among them, I N is the load current; U S is the on-load tap changer level voltage; R is the transition resistance.

[0070] When the on-load tap changer switches from winding N tapping to winding N+1 tapping, the transition circuit conversion process is as follows: Fig.10 As shown;

[0071] When the on-load tap changer switches from winding N+1 tapping to winding N tapping, the transition circuit conversion process is as follows: Fig.11 As shown;

[0072] Fig.12 The circuit diagram of the single-resistance symmetrical transition circuit of the on-load tap changer whose switch element is a power electronic element is shown in FIG. Fig.12 As shown, only Figure 1 The single-break vacuum contact in the power supply is replaced with a power electronic component with controllable on / off function (including a thyristor switch or an insulated gate bipolar transistor switch), and other components are the same as Figure 1 The components are the same, the action sequence is consistent, and the functions and effects are the same Figure 1 The transition circuits shown are the same and will not be described in detail.

[0073] Fig.13 The circuit diagram is a single-resistance symmetrical transition circuit of an on-load tap changer whose switching element is a double-break vacuum contact; Fig.13 As shown, only Figure 1 The single-break vacuum contact in the system is replaced with a double-break vacuum contact, and other components are the same as Figure 1 The components are the same, the action sequence is consistent, and the functions and effects are the same Figure 1 The transition circuits shown are the same and will not be described in detail.

[0074] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A single-resistance symmetrical transition circuit for an on-load tap changer, characterized in that: include: The first main contact (MC1), the second main contact (MC2), the main vacuum contact (V1), the first auxiliary vacuum contact (V2), the second auxiliary vacuum contact (V3), the first disconnector (Z1), the second disconnector (Z2), the change-over switch (T), the transition resistor (R), the first winding tap (N) of the transformer voltage regulating winding, the second winding tap (N+1) of the transformer voltage regulating winding, and the neutral point lead-out terminal of the on-load tap changer; The first main contact (MC1), the first auxiliary vacuum contact (V2) and the first static contact (11) in the conversion switch (T) are connected to the first winding tap (N) of the transformer voltage regulating winding, the other end of the first auxiliary vacuum contact (V2) is connected to one end of the first isolating switch (Z1), the second auxiliary vacuum contact (V3), one end of the second main contact (MC2) and the second static contact (12) in the conversion switch (T) are connected to the second winding tap (N+1) of the transformer voltage regulating winding, and the main vacuum contact (V2) is connected to the second main contact (MC2). One end of the contact (V1) is connected to the moving contact in the transfer switch (T), the other end of the second auxiliary vacuum contact (V3) is connected to one end of the second disconnector (Z2), the other ends of the first disconnector (Z1) and the second disconnector (Z2) are connected to one end of the transition resistor (R), and the other end of the first main contact (MC1), the other end of the main vacuum contact (V1), the other end of the transition resistor (R) and the other end of the second main contact (MC2) are all connected to the neutral point lead-out terminal of the on-load tap changer; The first main contact (MC1) is turned on, the second main contact (MC2) is turned off, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are turned off, the moving contact in the conversion switch (T) is connected to the first static contact (11), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is turned off, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the first main contact (MC1); When the first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are disconnected, the moving contact in the conversion switch (T) is connected to the first static contact (11), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the first winding tap (N) is connected, and the load current flows out from the neutral point lead-out terminal of the on-load tap changer through the conversion switch (T) and the main vacuum contact (V1).

2. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are turned on, the moving contact in the conversion switch (T) is connected to the first static contact (11), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the first winding tap (N) is connected, and the load current continues to flow out from the neutral point lead-out terminal of the on-load tap changer through the conversion switch (T) and the main vacuum contact (V1).

3. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is disconnected, an arc is generated, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are turned on, the moving contact in the conversion switch (T) is connected to the first static contact (11), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the first winding tap (N) is connected, and the load current flows out through the first auxiliary vacuum contact (V2), the first isolating switch (Z1), the transition resistor (R) and the neutral point lead-out terminal of the on-load tap changer.

4. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is disconnected, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are turned on, and when the arc in the main vacuum contact (V1) is completely extinguished, the moving contact in the conversion switch (T) is rotated to connect with the second static contact (12), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the first winding tap (N) is connected, and the load current flows out through the first auxiliary vacuum contact (V2), the first isolating switch (Z1), the transition resistor (R) and the neutral point lead-out terminal of the on-load tap changer.

5. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are turned on, the moving contact in the conversion switch (T) is connected to the second static contact (12), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the first winding tap (N) and the second winding tap (N+1) are both connected, and the load current flows out through the conversion switch (T), the main vacuum contact (V1) and the neutral point lead-out terminal of the on-load tap changer.

6. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are disconnected, the moving contact in the conversion switch (T) is connected to the second static contact (12), the first isolating switch (Z1) is turned on, and the second isolating switch (Z2) is disconnected, the second winding tap (N+1) is connected, and the load current flows out through the conversion switch (T), the main vacuum contact (V1) and the neutral point lead-out terminal of the on-load tap changer.

7. The single-resistance symmetrical transition circuit of an on-load tap changer according to claim 1, characterized in that: The first main contact (MC1) is disconnected, the second main contact (MC2) is disconnected, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are disconnected, the moving contact in the conversion switch (T) is connected to the second static contact (12), and when the arc in the first auxiliary vacuum contact (V2) is completely extinguished, the first disconnector (Z1) is disconnected, and when the second disconnector (Z2) is turned on, the second winding tap (N+1) is connected, and the load current flows out through the conversion switch (T), the main vacuum contact (V1) and the neutral point lead-out terminal of the on-load tap changer; The first main contact (MC1) is disconnected, the second main contact (MC2) is turned on, the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) and the second auxiliary vacuum contact (V3) are disconnected, the moving contact in the conversion switch (T) is connected to the second static contact (12), the first isolating switch (Z1) is disconnected, and the second isolating switch (Z2) is turned on, the second winding tap (N+1) is connected, and the load current flows out through the second main contact (MC2) and the neutral point lead-out terminal of the on-load tap changer.

8. A voltage regulation method for a single-resistance symmetrical transition circuit of an on-load tap changer, characterized in that: The following steps are involved: The first main contact (MC1) is turned on, the second main contact (MC2) is turned off, the first auxiliary vacuum contact (V2) is turned off, the second auxiliary vacuum contact (V3) is turned off, the main vacuum contact (V1) is turned on, the first isolating switch (Z1) is turned on, the second isolating switch (Z2) is turned off, and when the conversion switch (T) is connected to the first winding tap (N), the first main contact (MC1) is turned off, the first auxiliary vacuum contact (V2) is turned on, the second auxiliary vacuum contact (V3) is turned on, and the main The vacuum contact (V1) is disconnected to generate an arc; after the main vacuum contact (V1) is completely extinguished, the conversion switch (T) is controlled to connect the main vacuum contact (V1) with the second winding tap (N+1); then the main vacuum contact (V1) is turned on, the first auxiliary vacuum contact (V2) is disconnected, and the second auxiliary vacuum contact (V3) is disconnected to generate an arc; after the first auxiliary vacuum contact (V2) is completely extinguished, the first isolating switch (Z1) is disconnected and the second isolating switch (Z2) is turned on; The second main contact (MC2) is turned on, so that the load current flows out from the second winding tap (N+1) through the second main contact (MC2) and from the neutral point lead-out terminal of the on-load tap changer; The second main contact (MC2) is turned on, the first main contact (MC1) is turned off, the first auxiliary vacuum contact (V2) is turned off, the second auxiliary vacuum contact (V3) is turned off, the first isolating switch (Z1) is turned off, the main vacuum contact (V1) is turned on, the second isolating switch (Z2) is turned on, and when the conversion switch (T) is connected to the second winding tap (N+1), the second main contact (MC2) is turned off, the first auxiliary vacuum contact (V2) is turned on, and the second auxiliary vacuum contact (V3) is turned on; then the main vacuum contact (V1) is turned off to generate an arc; when the main vacuum contact (V1) is turned on, the arc is generated. ) after the arc is completely extinguished, the conversion switch (T) is controlled to connect the main vacuum contact (V1) with the first winding tap N; then the main vacuum contact V1 is turned on, the first auxiliary vacuum contact (V2) is disconnected, and the second auxiliary vacuum contact (V3) is disconnected to generate an arc; after the second auxiliary vacuum contact (V3) is completely extinguished, the first isolating switch (Z1) is turned on and the second isolating switch (Z2) is disconnected; then the first main contact (MC1) is turned on to allow the load current to flow out from the first winding tap (N) through the first main contact (MC1) from the neutral point lead-out terminal of the on-load tap changer.

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