Three vacuum tube transition circuit and voltage regulation method of converter transformer on-load tap changer

Abstract

The application discloses a three-vacuum tube transition circuit of a converter transformer on-load tap changer and a voltage regulating method, which comprises a first vacuum tube, a second vacuum tube, a third vacuum tube, a first conversion switch, a second conversion switch and a transition resistor, one end of a first main contact, one end of the first vacuum tube and a first static contact of the second conversion switch are connected with a first winding tap of a transformer voltage regulating winding, one end of a second main contact, one end of the third vacuum tube and a second static contact of the second conversion switch are connected with a second winding tap of the transformer voltage regulating winding, and one end of the second vacuum tube is connected with a moving contact of the second conversion switch. The application adopts three vacuum tubes, in the reciprocating switching process, the second vacuum tube undertakes the task of breaking the load current, the first vacuum tube and the third vacuum tube undertake the task of breaking the inter-stage circulating current in turn, and the breaking loss and the switching capacity of each vacuum tube are balanced; the two conversion switches can play a backup safety protection function, so that the reliability and safety are improved.

Description

Technical Field

[0001] This invention relates to the field of on-load tap changer technology, and particularly to a three-vacuum tube transition circuit and voltage regulation method for an on-load tap changer of a converter transformer. Background Technology

[0002] On-load tap changers are key components inside power transformers. They can operate under transformer excitation or load conditions, changing the effective turns ratio by altering the connections of several taps led out from the transformer windings, thus regulating the output voltage without interrupting the load current. On-load tap changers have a wide range of applications, especially in converter transformers in ultra-high voltage direct current (UHVDC) transmission projects, to ensure the rated firing angle of the converter during normal operation. Early power transformers mostly used on-load tap changers based on high-speed resistance switching, relying on copper-tungsten arc contacts for load switching. These oil-immersed, non-vacuum on-load tap changers involved frequent switching, resulting in relatively severe arc contact burn-out and rapid oil carbonization and contamination, thus increasing the workload of daily maintenance and periodic inspections for power supply departments. Vacuum-type on-load tap changers primarily use vacuum tubes to extinguish the arc, avoiding the carbonization and contamination of the oil caused by arc extinguishing in oil. Due to the short arc breaking time, low arc voltage, low arc energy consumption, and recondensation of contact metal vapors in the vacuum tube, contact burn-out and corrosion can be minimized. Power electronic on-load tap changers replace vacuum tubes with power electronic components to achieve arc-free operation during on-load switching.

[0003] An on-load tap changer consists of a switching switch, a tap selector, and an electric mechanism. The switching switch, with its independent oil chamber, is the key component for on-load switching, and its core is the use of a transition circuit. Vacuum-type on-load tap changers can be classified according to the number of vacuum tubes: single-contact, double-contact, three-contact, and four-contact circuits; according to the number of transition resistors: single-resistor and double-resistor transitions; and according to the number of contact breaks: single-break and double-break, etc. Various combinations of these can form various transition circuits for vacuum-type on-load tap changers. The vacuum tubes 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 switching voltage regulation, and the switching tasks of each vacuum tube will also differ. The topology 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 on-load tap changer transition circuit, there is a main switching vacuum tube that is only responsible for interrupting the load current and an auxiliary vacuum tube that is only responsible for interrupting the interstage circulating current. In actual ultra-high voltage direct current transmission projects, the load current flowing through the on-load tap changer of the converter transformer is about 500-600A, and the interstage circulating current flowing through the transition resistor during the switching process is about 900-1000A. The circulating current interrupted by the auxiliary vacuum tube in a single operation is significantly greater than the load current interrupted by the main switching vacuum tube, resulting in an imbalance in the interruption tasks of the auxiliary and main switching vacuum tubes. Summary of the Invention

[0005] To overcome the problems in the prior art, the purpose of this invention is to propose a three-vacuum tube transition circuit and voltage regulation method for an on-load tap changer of a converter transformer. It uses three vacuum tube elements, and two auxiliary vacuum tubes alternately interrupt the circulating current to balance the interruption loss of the vacuum tubes. The two changeover switches can serve as backup safety protection measures for the vacuum tubes, thereby improving the reliability and service life of the on-load tap changer.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A three-vacuum tube transition circuit for an on-load tap changer of a converter transformer includes a first main contact, a second main contact, a first vacuum tube, a second vacuum tube, a third vacuum tube, a first changeover switch, a second changeover switch, and a transition resistor;

[0008] Wherein, one end of the first main contact, one end of the first vacuum tube, and the first stationary contact of the second changeover switch are all connected to the first winding tap of the transformer voltage regulating winding; one end of the second main contact, one end of the third vacuum tube, and the second stationary contact of the second changeover switch are all connected to the second winding tap of the transformer voltage regulating winding.

[0009] One end of the second vacuum tube is connected to the moving contact of the second changeover switch;

[0010] One end of the transition resistor and the first stationary contact of the first changeover switch are both connected to the other end of the first vacuum tube.

[0011] The other end of the transition resistor and the second stationary contact of the first changeover switch are both connected to the other end of the third vacuum tube.

[0012] The other end of the first main contact, the other end of the second main contact, the other end of the second vacuum tube, and the moving contact of the first changeover switch are all connected to the neutral point lead-out of the on-load tap changer.

[0013] Furthermore, when the first main contact, the first vacuum tube, and the second vacuum tube are all in the conducting state, and the third vacuum tube and the second main contact are in the disconnected state, the moving contact of the first changeover switch is connected to the second stationary contact of the first changeover switch, and the moving contact of the second changeover switch is connected to the first stationary contact of the second changeover switch, the load current flows from the first winding tap through the first main contact to the neutral point lead-out terminal.

[0014] Furthermore, when the second main contact, the second vacuum tube, and the third vacuum tube are all in the conducting state, and the first vacuum tube and the first main contact are in the disconnected state, the moving contact of the first changeover switch is connected to the first stationary contact of the first changeover switch, and the moving contact of the second changeover switch is connected to the second stationary contact of the second changeover switch, the current flows from the second winding tap through the second main contact to the neutral point lead-out terminal.

[0015] Furthermore, the first vacuum tube, the second vacuum tube, and the third vacuum tube are single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable switching functions.

[0016] A voltage regulation method for the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0017] The first main contact, the first vacuum tube, and the second vacuum tube are all in the conducting state, while the third vacuum tube and the second main contact are in the disconnected state. The moving contact of the first changeover switch is connected to its second stationary contact, and the moving contact of the second changeover switch is connected to its first stationary contact.

[0018] Disconnect the first main contact; disconnect the second vacuum tube to generate an arc; after the second vacuum tube has completely extinguished its arc, connect the moving contact of the second changeover switch to the second stationary contact; turn on the second vacuum tube, at which point the first winding tap and the second winding tap are in a bridging position; disconnect the first vacuum tube to generate an arc; after the first vacuum tube has completely extinguished its arc, connect the moving contact of the first changeover switch to the first stationary contact; turn on the third vacuum tube; turn on the second main contact, and the load current flows from the second winding tap through the second main contact to the neutral point, and the on-load tap changer switches from the first winding tap to the second winding tap.

[0019] Furthermore, when the first winding tap and the second winding tap are in the bridging position, the current I flowing through the second vacuum tube... V Calculated using the following formula:

[0020] I V =I N -I C

[0021] Among them, I N I is the load current. C The current flowing through the first vacuum tube is an interstage circulating current.

[0022] Furthermore, the interstage circulation is calculated using the following formula:

[0023] I C =U S / R;

[0024] Among them, U S R is the voltage between the on-load tap changer stages, and R is the transition resistance.

[0025] A voltage regulation method for the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0026] The second main contact, the second vacuum tube, and the third vacuum tube are all in the conducting state, the first vacuum tube and the first main contact are in the disconnected state, the moving contact of the first changeover switch is connected to the first stationary contact, and the moving contact of the second changeover switch is connected to the second stationary contact.

[0027] Disconnect the second main contact; disconnect the second vacuum tube to generate an arc; after the second vacuum tube has completely extinguished its arc, connect the moving contact of the second changeover switch to the first stationary contact; turn on the second vacuum tube, at which point the second winding tap and the first winding tap are in a bridging position; disconnect the third vacuum tube to generate an arc; after the third vacuum tube has completely extinguished its arc, connect the moving contact of the first changeover switch to the second stationary contact of the first changeover switch; turn on the first vacuum tube; turn on the first main contact, and the load current flows from the first winding tap through the first main contact to the neutral point, and the on-load tap changer switches from the second winding tap to the first winding tap.

[0028] Furthermore, when the second winding tap and the first winding tap are in the bridging position, the current I flowing through the second vacuum tube... V Calculated using the following formula:

[0029] I V =I N +I C

[0030] Among them, I C The current flowing through the third vacuum tube is an interstage circulating current, I N This is the load current.

[0031] Furthermore, the current flowing through the third vacuum tube, the interstage circulating current, is calculated using the following formula:

[0032] I C =U S / R

[0033] Among them, U S R is the voltage between the on-load tap changer stages, and R is the transition resistance.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The transition circuit of this invention employs three vacuum tube elements. During the reciprocating switching process, the second vacuum tube is responsible for interrupting the load current, while the first and third vacuum tubes take turns interrupting the interstage circulating current. This reduces the switching losses of the auxiliary vacuum tubes, balances the interrupting losses and switching capacity of each vacuum tube, and improves the service life of the on-load tap changer. Two changeover switches are used, whose mechanical contacts can be designed to have oil-based arc-extinguishing capability, serving as backup safety protection for the vacuum tubes, thereby improving the reliability and safety of the on-load tap changer. A single transition resistor is used, facilitating design and installation and ensuring insulation distance.

[0036] The voltage regulation method of the present invention enables the transition circuit to achieve a reciprocating switching process of the load current between the first winding tap and the second winding tap. The vacuum tube realizes the current interruption. The switching action of the two switching switches is after the corresponding vacuum tube interrupts the current, which can serve as a backup safety protection measure in case of vacuum tube failure. When the transition circuit is in the bridging position, the interstage circulating current is limited by the transition resistor. The auxiliary vacuum tube only needs to interrupt the circulating current, avoiding the condition of the interrupted circulating current superimposed on the load current, thus ensuring the maximum reliability under overload. Attached Figure Description

[0037] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0038] Figure 1 A circuit diagram of a three-vacuum tube transition circuit for an on-load tap changer of a converter transformer according to an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram showing the first main contact being open in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram showing the second vacuum tube disconnected in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the operation of the second switching switch in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram showing the conduction of the second vacuum tube in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0043] Figure 6 This is a schematic diagram showing the first vacuum tube being disconnected in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0044] Figure 7 This is a schematic diagram of the operation of the first switching switch in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0045] Figure 8 This is a schematic diagram showing the conduction of the third vacuum tube in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0046] Figure 9 This is a schematic diagram showing the conduction of the second main contact in the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0047] Figure 10 This is a schematic diagram of the on-load tap changer of a converter transformer according to an embodiment of the present invention, showing the switching of each switch in the three-vacuum tube transition circuit during the process of switching the load from the first winding tap N to the second winding tap N+1.

[0048] Figure 11 A schematic diagram of the on-load tap changer of a converter transformer according to an embodiment of the present invention, showing the switching of each switch in the three-vacuum tube transition circuit during the process of switching the load from the second winding tap N+1 to the first winding tap N.

[0049] Figure 12 A circuit diagram of a three-vacuum tube transition circuit for an on-load tap changer of a converter transformer, wherein the switching element is a power electronic component, according to an embodiment of the present invention.

[0050] Figure 13 This is a circuit diagram of a three-vacuum tube transition circuit for an on-load tap changer of a converter transformer, wherein the switching element is a double-break vacuum tube, according to an embodiment of the present invention. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings.

[0052] like Figure 1 As shown, this invention provides a three-vacuum tube transition circuit for an on-load tap changer of a converter transformer. This transition circuit uses three vacuum tube elements. During the reciprocating switching process, the second vacuum tube V2 is responsible for interrupting the load current, while the first vacuum tube V1 and the third vacuum tube V3 take turns interrupting the interstage circulating current. This balances the interruption losses and switching capacity of each vacuum tube, improving the service life of the on-load tap changer. After the corresponding vacuum tube interrupts the current, the mechanical contacts of the two switching switches can be designed to have oil-based arc extinguishing capability, serving as a backup safety protection measure for the vacuum tubes, thereby improving the reliability and safety of the on-load tap changer.

[0053] The three-vacuum tube transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention includes a first main contact MC1, a second main contact MC2, a first vacuum tube V1, a second vacuum tube V2, a third vacuum tube V3, a first changeover switch T1, a second changeover switch T2, and a transition resistor R; wherein, one end of the first main contact MC1 is connected to the first winding tap N of the transformer regulating winding; one end of the second main contact MC2 is connected to the second winding tap N+1 of the transformer regulating winding; one end of the first vacuum tube V1 is connected to the first winding tap N of the transformer regulating winding, and the other end of the first vacuum tube V1 is connected to one end of the transition resistor R and the first stationary contact 11 of the first changeover switch T1; one end of the second vacuum tube V2 is connected to the moving contact of the second changeover switch T2; one end of the third vacuum tube V3 is connected to the second winding tap N+1 of the transformer regulating winding, and the other end is connected to one end of the transition resistor R and the second stationary contact of the first changeover switch T1. 12 Connections; One end of the transition resistor R is connected to one end of the first vacuum tube V1 and the first stationary contact 11 of the first changeover switch T1, and the other end is connected to one end of the third vacuum tube V3 and the second stationary contact 12 of the first changeover switch T1; The first stationary contact 11 of the first changeover switch T1 is connected to one end of the first vacuum tube V1 and one end of the transition resistor R, and the second stationary contact 12 of the first changeover switch T1 is connected to one end of the third vacuum tube V3 and the other end of the transition resistor R; The first stationary contact 21 of the second changeover switch T2 is connected to the first winding tap N of the transformer voltage regulating winding, and the second stationary contact 22 of the second changeover switch T2 is connected to the second winding tap N+1 of the transformer voltage regulating winding; The moving contact of the second changeover switch T2 is connected to one end of the second vacuum tube V2; The first main contact MC1, the second main contact MC2, the other end of the second vacuum tube V2, and the moving contact of the first changeover switch T1 are all connected to the neutral point lead-out of the on-load tap changer.

[0054] When the first main contact MC1, the first vacuum tube V1, and the second vacuum tube V2 are all in the conducting state, and the third vacuum tube V3 and the second main contact MC2 are in the disconnected state, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the on-load tap changer transition circuit can enable the load current to flow from the first winding tap N through the first main contact MC1 to the neutral point lead-out terminal.

[0055] When the second main contact MC2, the second vacuum tube V2, and the third vacuum tube V3 are all in the conducting state, the first vacuum tube V1 and the first main contact MC1 are in the open state, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the on-load tap changer transition circuit can enable the load current to flow from the second winding tap N+1 through the second main contact MC2 to the neutral point lead-out terminal.

[0056] The internal switching element in the three-vacuum tube transition circuit of the on-load tap changer can be replaced by a single-break vacuum tube with a power electronic component that has a controllable on / off function and a double-break vacuum tube.

[0057] A voltage regulation method for a three-vacuum tube transition circuit of an on-load tap changer in a converter transformer is illustrated using a single-break vacuum tube as an example. When the on-load tap changer switches from tap N of the first winding to tap N+1 of the second winding, the voltage regulation method is as follows:

[0058] like Figure 1 As shown, the first main contact MC1 is in the ON state, the second main contact MC2 is in the OFF state, the first vacuum tube V1 and the second vacuum tube V2 are in the ON state, and the third vacuum tube V3 is in the OFF state. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N is turned on, and the load current flows out from the neutral point lead-out terminal through the first main contact MC1.

[0059] like Figure 2 As shown, the first main contact MC1 is disconnected, the second main contact MC2 remains disconnected, the first vacuum tube V1 and the second vacuum tube V2 remain conducting, the third vacuum tube V3 remains disconnected, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the first winding tap N remains connected, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0060] like Figure 3 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, disconnecting the second vacuum tube V2 and generating an arc. The first vacuum tube V1 remains on, the third vacuum tube V3 remains off, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the first winding tap N remains on, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the transition resistor R, and the first changeover switch T1.

[0061] like Figure 4As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains on, the second vacuum tube V2 remains off, and the third vacuum tube V3 remains off. After the arc in the second vacuum tube V2 is extinguished, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, and the moving contact of the first changeover switch T1 is connected to its second stationary contact 12. The first winding tap N remains on, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the transition resistor R, and the first changeover switch T1.

[0062] like Figure 5 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains closed, the second vacuum tube V2 is closed, the third vacuum tube V3 remains open, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the first winding tap N and the second winding tap N+1 are both closed, and the load current I... N The current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2; at this time, the first winding tap and the second winding tap are in the bridging position, the transition circuit forms a bridge, and an interstage circulating current I is generated. C The current flowing through the first vacuum tube V1 is the interstage circulating current I. C The current I flowing through the second vacuum tube V2 V =I N -I C ; where I C =U S / R, the U S This refers to the interstage voltage of the on-load tap changer.

[0063] like Figure 6 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, disconnecting the first vacuum tube V1 and generating an electric arc. The second vacuum tube V2 remains on, and the third vacuum tube V3 remains off. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0064] like Figure 7As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains open, the second vacuum tube V2 remains open, and the third vacuum tube V3 remains open. After the arc in the first vacuum tube V1 is extinguished, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains open, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0065] like Figure 8 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, the first vacuum tube V1 remains open, the second vacuum tube V2 remains open, the third vacuum tube V3 is turned on, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the second winding tap N+1 remains open, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0066] like Figure 9 As shown, the first main contact MC1 remains open, while the second main contact MC2 is turned on. The first vacuum tube V1 remains open, the second vacuum tube V2 remains on, and the third vacuum tube V3 remains on. The moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out terminal through the second main contact MC2.

[0067] When the on-load tap changer switches from the second winding tap N+1 to the first winding tap N, the switching process is symmetrical to the switching process when the on-load tap changer switches from the first winding tap N to the second winding tap N+1. The voltage adjustment method is as follows:

[0068] The second main contact MC2 is in the ON state, the first main contact MC1 is in the OFF state, the third vacuum tube V3 and the second vacuum tube V2 are in the ON state, the first vacuum tube V1 is in the OFF state, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, and the moving contact of the second changeover switch T2 is connected to its second stationary contact 22. The second winding tap N+1 is turned on, and the load current flows out from the neutral point lead-out terminal through the second main contact MC2.

[0069] The second main contact MC2 is disconnected, the first main contact MC1 remains disconnected, the third vacuum tube V3 and the second vacuum tube V2 remain conducting, the first vacuum tube V1 remains disconnected, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the second winding tap N+1 remains connected, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0070] The second main contact MC2 remains open, the first main contact MC1 remains open, disconnecting the second vacuum tube V2 and generating an arc. The third vacuum tube V3 remains on, the first vacuum tube V1 remains off, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, the moving contact of the second changeover switch T2 is connected to its second stationary contact 22, the second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the transition resistor R, and the first changeover switch T1.

[0071] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains on, the second vacuum tube V2 remains off, and the first vacuum tube V1 remains off. After the arc in the second vacuum tube V2 is extinguished, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, and the moving contact of the first changeover switch T1 is connected to its first stationary contact 11. The second winding tap N+1 remains on, and the load current flows out from the neutral point lead-out through the third vacuum tube V3, the transition resistor R, and the first changeover switch T1.

[0072] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains closed, the second vacuum tube V2 is turned on, the first vacuum tube V1 remains open, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, both the first winding tap N and the second winding tap N+1 are connected, and the load current I... N The current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2; at this time, the second winding tap and the first winding tap are in the bridging position, the transition circuit forms a bridge, and an interstage circulating current I is generated. C The current flowing through the third vacuum tube V3 is the interstage circulating current I. C The current I flowing through the second vacuum tube V2 V =I N +I C ; where I C =U S / R, the U S This refers to the interstage voltage of the on-load tap changer.

[0073] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 is disconnected, generating an arc, the second vacuum tube V2 remains on, the first vacuum tube V1 remains off, the moving contact of the first changeover switch T1 is connected to its first stationary contact 11, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the first winding tap N remains on, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0074] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains open, the second vacuum tube V2 remains on, and the first vacuum tube V1 remains open. After the arc in the third vacuum tube V3 is extinguished, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N remains on, and the load current flows out from the neutral point lead-out through the second changeover switch T2 and the second vacuum tube V2.

[0075] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 remains open, the second vacuum tube V2 remains open, the first vacuum tube V1 is turned on, the moving contact of the first changeover switch T1 is connected to its second stationary contact 12, the moving contact of the second changeover switch T2 is connected to its first stationary contact 21, the first winding tap N remains open, and the load current flows out from the neutral point lead-out terminal through the second changeover switch T2 and the second vacuum tube V2.

[0076] The second main contact MC2 remains open, while the first main contact MC1 is turned on. The third vacuum tube V3 remains open, the second vacuum tube V2 remains on, and the first vacuum tube V1 remains on. The moving contact of the first changeover switch T1 is connected to its second stationary contact 12, and the moving contact of the second changeover switch T2 is connected to its first stationary contact 21. The first winding tap N remains on, and the load current flows out from the neutral point lead-out terminal through the first main contact MC1.

[0077] When the internal switching element in the three-vacuum tube transition circuit of the on-load tap changer is replaced with a power electronic element and a double-break vacuum tube with controllable switching function, the operating timing and voltage regulation method of the switching element are the same, and will not be described again.

[0078] When the on-load tap changer switches from tap N of the first winding to tap N+1 of the second winding, the transition circuit switching procedure is shown in the diagram below. Figure 10 As shown.

[0079] When the on-load tap changer switches from tap N+1 of the second winding to tap N of the first winding, the transition circuit switching procedure is shown in the diagram below. Figure 11 As shown.

[0080] In embodiments of the present invention, the switching tasks of the on-load tap changer transition circuit of the commutator using a vacuum tube are shown in the following table:

[0081]

[0082] Among them, I N U is the load current; S R is the interstage voltage of the on-load tap changer; R is the transition resistance.

[0083] Figure 12 The circuit diagram is shown below for a three-vacuum tube transition circuit of an on-load tap changer for a converter transformer, wherein the switching element is a power electronic component, according to an embodiment of the present invention. Figure 12 As shown, only Figure 1 The single-break vacuum tube in the middle is replaced with a power electronic component with controllable switching function, and other components are the same as those in the middle. Figure 1 The components are the same, the timing of their operation is consistent, and they are the same as those in the original text. Figure 1 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0084] Figure 13 This is a circuit diagram of a three-vacuum tube transition circuit for an on-load tap changer of a converter transformer, wherein the switching element is a double-break vacuum tube, according to an embodiment of the present invention; as follows: Figure 13 As shown, only Figure 1 The single-break vacuum tube in the middle is replaced with a double-break vacuum tube, and other components are the same as those in the middle. Figure 1 The components are the same, the timing of their operation is consistent, and they are the same as those in the original text. Figure 1 The function and role of the transition circuit shown are the same, and will not be repeated here.

[0085] This invention employs three vacuum tube elements. During the reciprocating switching process, the second vacuum tube V2 is responsible for interrupting the load current, while the first vacuum tube V1 and the third vacuum tube V3 take turns interrupting the interstage circulating current, thus balancing the interruption loss and switching capacity of each vacuum tube. The two changeover switches can serve as backup safety protection functions, thereby improving the reliability and safety of the on-load tap changer.

[0086] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention, such as adding a disconnecting switch to the existing vacuum tube circuit to play an electrical isolation and protection role, should be covered within the protection scope of the present invention.

Claims

1. A three-vacuum-tube transition circuit for an on-load tap changer of a converter transformer, characterized in that, It includes a first main contact (MC1), a second main contact (MC2), a first vacuum tube (V1), a second vacuum tube (V2), a third vacuum tube (V3), a first changeover switch (T1), a second changeover switch (T2), and a transition resistor (R); Wherein, one end of the first main contact (MC1), one end of the first vacuum tube (V1) and the first stationary contact (21) of the second changeover switch (T2) are all connected to the first winding tap (N) of the transformer voltage regulating winding; one end of the second main contact (MC2), one end of the third vacuum tube (V3) and the second stationary contact (22) of the second changeover switch (T2) are all connected to the second winding tap (N+1) of the transformer voltage regulating winding; One end of the second vacuum tube (V2) is connected to the moving contact of the second changeover switch (T2); One end of the transition resistor (R) and the first stationary contact (11) of the first changeover switch (T1) are both connected to the other end of the first vacuum tube (V1); The other end of the transition resistor (R) and the second stationary contact (12) of the first changeover switch (T1) are both connected to the other end of the third vacuum tube (V3); The other end of the first main contact (MC1), the other end of the second main contact (MC2), the other end of the second vacuum tube (V2), and the moving contact of the first changeover switch (T1) are all connected to the neutral point lead-out of the on-load tap changer. When the first main contact (MC1), the first vacuum tube (V1) and the second vacuum tube (V2) are all in the conducting state, the third vacuum tube (V3) and the second main contact (MC2) are in the open state, the moving contact of the first changeover switch (T1) is connected to the second stationary contact (12) of the first changeover switch (T1), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21) of the second changeover switch (T2), the load current flows from the first winding tap (N) through the first main contact (MC1) to the neutral point lead-out terminal; When the second main contact (MC2), the second vacuum tube (V2), and the third vacuum tube (V3) are all in the conducting state, the first vacuum tube (V1) and the first main contact (MC1) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the first stationary contact (11) of the first changeover switch (T1), and the moving contact of the second changeover switch (T2) is connected to the second stationary contact (22) of the second changeover switch (T2), the current flows from the second winding tap (N+1) through the second main contact (MC2) to the neutral point lead-out terminal.

2. The three-vacuum tube transition circuit for an on-load tap changer of a converter transformer according to claim 1, characterized in that, The first vacuum tube (V1), the second vacuum tube (V2), and the third vacuum tube (V3) are either single-break vacuum tubes or double-break vacuum tubes.

3. A voltage regulation method based on the three-vacuum tube transition circuit of the on-load tap changer of the converter transformer as described in claim 1, characterized in that, Includes the following steps: The first main contact (MC1), the first vacuum tube (V1), and the second vacuum tube (V2) are all in the conducting state, the third vacuum tube (V3) and the second main contact (MC2) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the second stationary contact (12), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21). Disconnect the first main contact (MC1); disconnect the second vacuum tube (V2) to generate an arc; after the second vacuum tube (V2) is completely extinguished, connect the moving contact of the second changeover switch (T2) to the second stationary contact (22); turn on the second vacuum tube (V2), at which time the first winding tap and the second winding tap are in the bridging position; disconnect the first vacuum tube (V1) to generate an arc; after the first vacuum tube (V1) is completely extinguished, connect the moving contact of the first changeover switch (T1) to the first stationary contact (11); turn on the third vacuum tube (V3); turn on the second main contact (MC2), and the load current flows from the second winding tap (N+1) through the second main contact (MC2) to the neutral point, and the on-load tap switch switches from the first winding tap (N) to the second winding tap (N+1).

4. The voltage regulation method for the three-vacuum tube transition circuit of an on-load tap changer of a converter transformer according to claim 3, characterized in that, When the first winding tap and the second winding tap are in the bridging position, the current I flowing through the second vacuum tube (V2) is... V Calculated using the following formula: I V =I N -I C Among them, I N I is the load current. C It is an interstage circulation.

5. The voltage regulation method for the three-vacuum tube transition circuit of an on-load tap changer of a converter transformer according to claim 4, characterized in that, Interstage circulation is calculated using the following formula: I C =U S / R; Among them, U S R is the voltage between the on-load tap changer stages, and R is the transition resistance.

6. A voltage regulation method for a three-vacuum tube transition circuit of an on-load tap changer for a converter transformer as described in claim 5, characterized in that, Includes the following steps: The second main contact (MC2), the second vacuum tube (V2), and the third vacuum tube (V3) are all in the conducting state, the first vacuum tube (V1) and the first main contact (MC1) are in the disconnected state, the moving contact of the first changeover switch (T1) is connected to the first stationary contact (11), and the moving contact of the second changeover switch (T2) is connected to the second stationary contact (22). Disconnect the second main contact (MC2); disconnect the second vacuum tube (V2) to generate an electric arc; after the second vacuum tube (V2) has completely extinguished the arc, connect the moving contact of the second changeover switch (T2) to the first stationary contact (21); Turn on the second vacuum tube (V2), at which time the second winding tap and the first winding tap are in the bridging position; turn off the third vacuum tube (V3) to generate an arc; after the third vacuum tube (V3) completely extinguishes the arc, the moving contact of the first changeover switch (T1) is connected to the second stationary contact (12) of the first changeover switch (T1); turn on the first vacuum tube (V1); turn on the first main contact (MC1), and the load current flows from the first winding tap (N) through the first main contact (MC1) to the neutral point, and the on-load tap switch switches from the second winding tap (N+1) to the first winding tap (N).

7. The voltage regulation method for the three-vacuum tube transition circuit of an on-load tap changer of a converter transformer according to claim 6, characterized in that, When the second winding tap and the first winding tap are in the bridging position, the current I flowing through the second vacuum tube (V2) is... V Calculated using the following formula: I V =I N +I C Among them, I C For interstage circulation, I N This is the load current.

8. The voltage regulation method for the three-vacuum tube transition circuit of an on-load tap changer of a converter transformer according to claim 7, characterized in that, The current flowing through the third vacuum tube is the interstage circulating current, which is calculated using the following formula: I C =U S / R Among them, U S R is the voltage between the on-load tap changer stages, and R is the transition resistance.

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