A single-resistor transition circuit and voltage regulation method for a converter transformer with on-load voltage regulation

Abstract

The application discloses a single-resistor transition circuit and a voltage regulating method for a converter transformer load regulating switch, 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, a first main contact and the first vacuum tube are connected with a first winding tap of a transformer voltage regulating winding, a second main contact and the third vacuum tube are connected with a second winding tap of the transformer voltage regulating winding, the first vacuum tube and the transition resistor are connected with a movable contact of the first conversion switch, and the transition resistor and the other end of the third vacuum tube are connected with a movable contact of the second conversion switch. The application adopts one transition resistor and three vacuum tubes, in the reciprocating switching process of the transition circuit, 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 alternately, the single transition resistor is used, the design and installation are facilitated, and the insulation distance is ensured, and the application has the advantages of less transition resistor and alternating bearing of auxiliary vacuum contacts.

Description

Technical Field

[0001] This invention relates to the field of on-load tap changer technology, and in particular to a single-resistor 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 UHVDC 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. On-load tap changers often use oil-immersed mechanical contact changers. If a timing mismatch occurs during the switching process, the changer will inevitably extinguish its arc in the oil. Repeated arc extinguishing in the oil will severely contaminate the transformer oil, accumulate carbon, and reduce its insulation performance, ultimately leading to the inability to extinguish the arc in the oil, posing a significant safety risk. Summary of the Invention

[0005] To overcome the problems in the prior art, the purpose of this invention is to propose a single-resistor transition circuit and voltage regulation method for on-load tap changer of converter transformer. It adopts one transition resistor and three vacuum tubes. Both changeover switches operate after the switching process is completed. The components are symmetrically distributed, which can improve the reliability and switching efficiency of on-load tap changer.

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

[0007] A single-resistor 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 and one end of the first vacuum tube are connected to the first winding tap of the transformer voltage regulating winding; one end of the second main contact and one end of the third vacuum tube are connected to the second winding tap of the transformer voltage regulating winding.

[0009] The other end of the first vacuum tube and one end of the transition resistor are connected to the moving contact of the first changeover switch; the other end of the transition resistor and the other end of the third vacuum tube are connected to the moving contact of the second changeover switch.

[0010] The second stationary contact of the first changeover switch and the first stationary contact of the second changeover switch are connected to one end of the second vacuum tube; the first stationary contact of the first changeover switch and the second stationary contact of the second changeover switch are connected to the neutral point lead-out of the on-load tap changer; the other ends of the first main contact, the second main contact, and the second vacuum tube are all connected to the neutral point lead-out of the on-load tap changer.

[0011] 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, and the moving contact of the first changeover switch is connected to the second stationary contact, and the moving contact of the second changeover switch is connected to the second stationary contact, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the first main contact.

[0012] 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, and 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 first stationary contact, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the second main contact.

[0013] 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.

[0014] A voltage regulation method based on the single-resistor transition circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0015] 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 the second stationary contact, and the moving contact of the second changeover switch is connected to the second stationary contact.

[0016] After disconnecting the first main contact, disconnect the second vacuum tube; after the second vacuum tube has completely extinguished its arc, turn on the third vacuum tube. At this time, the first winding tap and the second winding tap are in the bridging position; disconnect the first vacuum tube; after the first vacuum tube has completely extinguished its arc, turn on the second main contact, and the load current flows out from the second winding tap through the second main contact from the neutral point.

[0017] After disconnecting the third vacuum tube, the moving contact of the first changeover switch is moved to the first stationary contact; the moving contact of the second changeover switch is moved to the first stationary contact; the second and third vacuum tubes are turned on, and the on-load tap changer is switched from the first winding tap to the second winding tap.

[0018] Furthermore, when the first winding tap and the second winding tap are in the bridging position, the current flowing through the third vacuum tube is calculated using the following formula:

[0019] I V =I N -I C

[0020] Among them, I V I is the current flowing through the third vacuum tube. C The current flowing through the first vacuum tube is an interstage circulating current, IN This is the load current.

[0021] Furthermore, the current flowing through the first vacuum tube is the interstage circulating current, calculated using the following formula:

[0022] I C =U S / R

[0023] Among them, U S R is the voltage between the on-load tap changer stages, and R is the transition resistance.

[0024] A voltage regulation method based on the single-resistor transition circuit of the on-load tap changer of the converter transformer as described above includes the following steps:

[0025] The second main contact, the second vacuum tube, and the third vacuum tube are all in the ON state, while the first vacuum tube and the first main contact are in the OFF 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 first stationary contact.

[0026] After disconnecting the second main contact, disconnect the second vacuum tube; after the second vacuum tube is completely extinguished, turn on the first vacuum tube. At this time, the first winding tap and the second winding tap are in the bridging position. Disconnect the third vacuum tube; after the third vacuum tube is completely extinguished, turn on the first main contact. The load current flows from the first winding tap through the first main contact out from the neutral point.

[0027] After disconnecting the first vacuum tube, the moving contact of the first changeover switch is moved to the second stationary contact; the moving contact of the second changeover switch is moved to the second stationary contact; the second vacuum tube and the first vacuum tube are connected; the on-load tap changer is switched from the second winding tap to the first winding tap.

[0028] Furthermore, when the first winding tap and the second winding tap are in the bridging position, the current flowing through the first vacuum tube is 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 is the interstage circulating current, 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 beneficial effects:

[0035] The transition circuit of this invention employs one transition resistor and three vacuum tubes. During the reciprocating switching process of the on-load tap changer, the second vacuum tube undertakes the task of interrupting the load current, while the first and third vacuum tubes take turns undertaking the task of interrupting the interstage circulating current. This reduces the switching loss of the interstage circulating current interrupting vacuum tubes, balances the switching capacity of each vacuum tube, and improves the reliability and service life of the on-load tap changer. The use of a single transition resistor facilitates design and installation and ensures the insulation distance. It has the advantages of low transition resistance, alternating load bearing of auxiliary vacuum contacts, and high safety.

[0036] The voltage regulation method of this invention allows the two changeover switches to operate without needing to move during the process of switching the load current from one main contact to the other. The switching action is performed only after the load current has switched between the winding taps, avoiding the situation where the changeover switches interrupt the arc during the switching process. This reduces the degradation of the insulating oil during the long service life of the on-load tap changer, which is conducive to achieving the requirement of maintenance-free operation of the on-load tap changer. The simultaneous operation of the two changeover switches can effectively reduce the mechanical complexity of the on-load tap changer and improve its reliability. 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 single-resistor 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 of the switching process in which the first main contact is disconnected in the single-resistor 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 of the switching process where the second vacuum tube is disconnected in the single-resistor 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 switching process of the third vacuum tube being turned on in the single-resistor 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 of the switching process where the first vacuum tube is disconnected in the single-resistor transition circuit of the on-load tap changer of the converter transformer according to an embodiment of the present invention.

[0043] Figure 6This is a schematic diagram of the switching process in which the second main contact is turned on in the single-resistor 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 switching process where the third vacuum tube is disconnected in the single-resistor 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 of the switching process of the first and second switching switches in the single-resistor 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 of the switching process of the second and third vacuum tubes being turned on in the single-resistor 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 single-resistor transition circuit of the converter transformer according to an embodiment of the present invention, 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 single-resistor transition circuit of the converter transformer according to an embodiment of the present invention, 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 single-resistor 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 single-resistor 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 1As shown, this invention provides a single-resistor transition circuit and voltage regulation method for an on-load tap changer in a converter transformer. It employs one transition resistor and three vacuum tubes. During the reciprocating switching process of the on-load tap changer transition circuit, 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 reduces the switching losses of the interstage circulating current interrupting vacuum tubes, balances the switching capacity of each vacuum tube, and improves the reliability and service life of the on-load tap changer. Two changeover switches are used. During the switching process from one main contact to the other, the two changeover switches do not need to operate. The switching action is performed only after the load current switching process is completed, avoiding the situation where the changeover switches interrupt the arc during the switching process and reducing the possibility of on-load tap changer failure. The use of a single transition resistor facilitates design and installation and ensures insulation distance. It has the advantages of low transition resistance and alternating load bearing by auxiliary vacuum contacts.

[0053] The single-resistor transition circuit for the on-load tap changer of the converter transformer 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's tap-regulating winding; one end of the second main contact MC2 is connected to the second winding tap N+1 of the transformer's tap-regulating winding; one end of the first vacuum tube V1 is connected to the first winding tap N of the transformer's tap-regulating winding, and the other end is connected to one end of the transition resistor R and the moving contact of the first changeover switch T1; one end of the transition resistor R is connected to one end of the first vacuum tube V1 and the moving contact of the first changeover switch T1. The moving contact is connected to one end of the third vacuum tube V3 and 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 voltage regulating winding, and the other end is connected to one end of the transition resistor R and the moving contact of the second changeover switch T2; one end of the second vacuum tube V2 is connected to the second stationary contact 12 of the first changeover switch T1 and the first stationary contact 21 of the second changeover switch; the first stationary contact 11 of the first changeover switch T1 and the second stationary contact 22 of the second changeover switch T2 are both connected to the neutral point lead-out of the on-load tap changer; the other ends of the first main contact MC1, the second main contact MC2, and the second vacuum tube V2 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 open 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 second stationary contact 22, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the first main contact MC1.

[0055] When the second main contact MC2, the second vacuum tube V2, and the third vacuum tube V3 are all in the conducting state, and 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 first stationary contact 21, the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the second main contact MC2.

[0056] The internal switching elements in the single-resistance transition circuit of the on-load tap changer of the converter transformer, namely the first vacuum tube V1, the second vacuum tube V2 and the third vacuum tube V3, can be replaced by single-break vacuum tubes with power electronic components and double-break vacuum tubes that have controllable switching functions.

[0057] A voltage regulation method for a single-resistor 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 second stationary contact 22. 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 second stationary contact 22, the first winding tap N remains connected, and the load current flows out from the neutral point lead-out terminal through the first vacuum tube V1, the second vacuum tube V2, and the first changeover switch T1.

[0060] like Figure 3As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, disconnecting the second vacuum tube V2 and generating an electric arc. The first vacuum tube V1 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 remains open, and the load current flows out from the neutral point lead-out through the first vacuum tube V1, the transition resistor R, and the second changeover switch T2.

[0061] like Figure 4 As shown, the first main contact MC1 remains open, the second main contact MC2 remains open, and the second vacuum tube V2 remains open. After the second vacuum tube V2 completely extinguishes its arc, the third vacuum tube V3 is closed. 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 first winding tap N and the second winding tap N+1 are both connected, and the load current I... N The current flows out from the neutral point terminal through the third vacuum tube V3 and the second changeover switch T2; the transition circuit forms a bridge, that is, the first winding tap N and the second winding tap N+1 are in the bridge position, generating an interstage circulating current I. C The current flowing through the first vacuum tube V1 is the interstage circulating current I. C The current I flowing through the third vacuum tube V3 V3 =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.

[0062] like Figure 5 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 open, and the third vacuum tube V3 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 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 through the third vacuum tube V3 and the second changeover switch T2.

[0063] like Figure 6 As shown, the first main contact MC1 remains open. After the first vacuum tube V1 is completely extinguished, the second main contact MC2 is closed. The first vacuum tube V1 and the second vacuum tube V2 remain open, and the third vacuum tube V3 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 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.

[0064] like Figure 7 As shown, the first main contact MC1 remains open, the second main contact MC2 remains closed, the first vacuum tube V1 and the second vacuum tube V2 remain open, the third vacuum tube V3 is 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 second stationary contact 22, the second winding tap N+1 remains closed, and the load current flows out from the neutral point lead-out terminal through the second main contact MC2.

[0065] like Figure 8 As shown, the first main contact MC1 remains open, the second main contact MC2 remains closed, the first vacuum tube V1, the second vacuum tube V2, and the third vacuum tube V3 remain 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, the second winding tap N+1 remains closed, and the load current flows out from the neutral point lead-out terminal through the second main contact MC2.

[0066] like Figure 9 As shown, the first main contact MC1 remains open, the second main contact MC2 remains closed, the first vacuum tube V1 remains open, the second vacuum tube V2 and the third vacuum tube V3 are closed, 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 second winding tap N+1 remains closed, 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 first stationary contact 21. 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 first stationary contact 21, the second winding tap N+1 remains connected, and the load current flows out from the neutral point lead-out terminal through the third vacuum tube V3, the second vacuum tube V2, and the second changeover switch T2.

[0070] The second main contact MC2 remains open, the first main contact MC1 remains open, disconnecting the second vacuum tube V2 and generating an electric arc. The third vacuum tube V3 remains 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 first stationary contact 21, 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 second changeover switch T2, and the transition resistor R.

[0071] The second main contact MC2 remains open, the first main contact MC1 remains open, and the second vacuum tube V2 remains open. After the second vacuum tube V2 has completely extinguished its arc, the first vacuum tube V1 is closed. 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 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 first vacuum tube V1 and the first changeover switch T1; the transition circuit forms a bridge, generating an interstage circulating current I. C The current flowing through the third vacuum tube V3 is the interstage circulating current I. C The current I flowing through the first vacuum tube V1 V1 =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.

[0072] The second main contact MC2 remains open, the first main contact MC1 remains open, the third vacuum tube V3 is disconnected, generating an electric arc, the second vacuum tube V2 remains open, 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, the first winding tap N is turned on, and the load current flows out from the neutral point lead-out terminal through the first vacuum tube V1 and the first changeover switch T1.

[0073] The second main contact MC2 remains open. After the third vacuum tube V3 is completely extinguished, the first main contact MC1 is closed. The third vacuum tube V3 and the second vacuum tube V2 remain open, while the first vacuum tube V1 remains open. 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 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.

[0074] The second main contact MC2 remains open, the first main contact MC1 remains closed, the third vacuum tube V3 and the second vacuum tube V2 remain open, the first vacuum tube V1 is 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 first stationary contact 21, the first winding tap N remains closed, and the load current flows out from the neutral point lead-out terminal through the first main contact MC1.

[0075] The second main contact MC2 remains open, the first main contact MC1 remains closed, the third vacuum tube V3, the second vacuum tube V2, and the first vacuum tube V1 remain 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 remains open, and the load current flows out from the neutral point lead-out terminal through the first main contact MC1.

[0076] The second main contact MC2 remains open, the first main contact MC1 remains closed, the third vacuum tube V3 remains open, the second vacuum tube V2 and the first vacuum tube V1 are closed, 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 remains closed, 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 single-resistance transition circuit of the on-load tap changer of the converter transformer is a power electronic component with controllable switching function and a double-break vacuum tube, the operating timing of the switching element and the voltage regulation method 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 process is as follows: 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 process is as follows: Figure 11 As shown.

[0080] In embodiments of the present invention, the switching tasks of the on-load tap changer transition circuit 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 12The circuit diagram of a single-resistor 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, is shown below. 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 The circuit diagram is shown below for a single-resistor transition circuit of an on-load tap changer for a converter transformer, wherein the switching element is a double-break vacuum tube, according to an embodiment of the present invention; 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] The transition circuit of this invention employs one transition resistor and three vacuum tubes. During the reciprocating switching process of the transition circuit, the second vacuum tube V2 undertakes the task of interrupting the load current, while the first vacuum tube V1 and the third vacuum tube V3 take turns undertaking the task of interrupting the interstage circulating current. The use of a single transition resistor facilitates design and installation and ensures the insulation distance. It has the advantages of low transition resistance and alternating load bearing of auxiliary vacuum contacts.

[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 single-resistor 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) and one end of the first vacuum tube (V1) are connected to the first winding tap (N) of the transformer voltage regulating winding; one end of the second main contact (MC2) and one end of the third vacuum tube (V3) are connected to the second winding tap (N+1) of the transformer voltage regulating winding. The other end of the first vacuum tube (V1) and one end of the transition resistor (R) are connected to the moving contact of the first changeover switch (T1); the other end of the transition resistor (R) and the other end of the third vacuum tube (V3) are connected to the moving contact of the second changeover switch (T2). The second stationary contact (12) of the first changeover switch (T1) and the first stationary contact (21) of the second changeover switch are connected to one end of the second vacuum tube (V2); the first stationary contact (11) of the first changeover switch (T1) and the second stationary contact (22) of the second changeover switch (T2) are connected to the neutral point lead-out of the on-load tap changer; the other ends of the first main contact (MC1), the second main contact (MC2), and the second vacuum tube (V2) are all connected to the neutral point lead-out of the on-load tap changer. When adjusting the voltage based on the single-resistor transition circuit of the on-load tap changer of the converter transformer, either Method 1 or Method 2 can be used. Method 1 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 second stationary contact (22). After disconnecting the first main contact (MC1), disconnect the second vacuum tube (V2); after the second vacuum tube (V2) has completely extinguished its arc, turn on the third vacuum tube (V3). At this time, the first winding tap (N) and the second winding tap (N+1) are in the bridging position; disconnect the first vacuum tube (V1); after the first vacuum tube (V1) has completely extinguished its arc, 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) out from the neutral point; After disconnecting the third vacuum tube (V3), the moving contact of the first changeover switch (T1) is moved to the first stationary contact (11); the moving contact of the second changeover switch (T2) is moved to the first stationary contact (21); the second vacuum tube (V2) and the third vacuum tube (V3) are turned on, and the on-load tap changer is switched from the first winding tap (N) to the second winding tap (N+1). The second method 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, while 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 the first stationary contact (11), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21). After disconnecting the second main contact (MC2), disconnect the second vacuum tube (V2); after the second vacuum tube (V2) has completely extinguished its arc, turn on the first vacuum tube (V1). At this time, the first winding tap (N) and the second winding tap (N+1) are in the bridging position; disconnect the third vacuum tube (V3); after the third vacuum tube (V3) has completely extinguished its arc, turn on the first main contact (MC1), and the load current flows from the first winding tap (N) through the first main contact (MC1) from the neutral point; After disconnecting the first vacuum tube (V1), the moving contact of the first changeover switch (T1) is moved to the second stationary contact (12); the moving contact of the second changeover switch (T2) is moved to the second stationary contact (22); the second vacuum tube (V2) and the first vacuum tube (V1) are connected; the on-load tap changer is switched from the second winding tap (N+1) to the first winding tap (N).

2. The single-resistor transition circuit for on-load tap changer of a converter transformer according to claim 1, characterized in that, 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 the second stationary contact (12), and the moving contact of the second changeover switch (T2) is connected to the second stationary contact (22), the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the first main contact (MC1).

3. The single-resistor transition circuit for on-load tap changer of a converter transformer according to claim 1, characterized in that, 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), and the moving contact of the second changeover switch (T2) is connected to the first stationary contact (21), the on-load tap changer transition circuit can allow the load current to flow out from the neutral point lead-out terminal through the second main contact (MC2).

4. The single-resistor transition circuit for 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 single-break vacuum tubes, double-break vacuum tubes, or power electronic components with controllable switching functions.

5. A single-resistor transition circuit for an on-load tap changer of a converter transformer according to claim 1, characterized in that, When the first winding tap (N) and the second winding tap (N+1) are in the bridging position using Method 1, the current flowing through the third vacuum tube (V3) is calculated using the following formula: I V =I N -I C Among them, I V I is the current flowing through the third vacuum tube. C The current flowing through the first vacuum tube is an interstage circulating current, I N This is the load current.

6. A single-resistor transition circuit for an on-load tap changer of a converter transformer according to claim 5, characterized in that, The current flowing through the first vacuum tube is the interstage circulating current, 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.

7. A single-resistor transition circuit for an on-load tap changer of a converter transformer according to claim 1, characterized in that, When the first winding tap (N) and the second winding tap (N+1) are in the bridging position using Method 2, the current flowing through the first vacuum tube (V1) is calculated using the following formula: I V =I N +I C Among them, I C The current flowing through the third vacuum tube is an interstage circulating current, I N This is the load current.

8. A single-resistor transition circuit for 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, 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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