A on-load tap-changer series load single-resistance transition circuit and voltage regulation method

Abstract

A series load single-resistance transition circuit and voltage regulation method for an on-load tap-changer, including a first main current-carrying switch; the first end of the first main on-off switch is connected to the first end of the first switching element, and the second end of the first main on-off switch is connected to the first end of the third switching element, the first end of the transition resistor, the first end of the fourth switching element, and the first end of the second main current-carrying switch. The second end of the first switching element and the second end of the third switching element are both connected to the first static contact of the change-over switch. The second end of the transition resistor is connected to the moving contact of the change-over switch. The second end of the second main current-carrying switch is connected to the first end of the second switching element, and the second end of the second switching element and the second end of the fourth switching element are both connected to the second static contact of the change-over switch. In the transition circuit, two load current breaking elements break the load current alternately, and the working loss degrees of the two circulating current breaking elements are the same, improving the reliability and electrical life of the on-load tap-changer.

Description

Technical Field

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

[0002] An on-load tap-changer is a key component inside a power transformer, which can operate and change the connection of several tap points led out from the transformer winding under the excitation or load state of the transformer to change the effective turns ratio, so as to adjust the output voltage without interrupting the load current. The on-load tap-changer has a wide range of applications, especially in the converter transformers of UHV DC transmission projects to ensure the rated trigger angle of the converter during normal operation. Most of the on-load tap-changers equipped with early power transformers adopted the high-speed resistance switching principle and relied on copper-tungsten arc contacts for load conversion. Such oil-immersed non-on-load tap-changers have frequent switching, and the arc contacts are correspondingly severely burned, and the carbonization and pollution speed of the oil are relatively fast, so it increases the daily maintenance and regular overhaul workload for the power supply department. The vacuum on-load tap-changer mainly uses vacuum tubes to extinguish the arc, avoiding the carbonization and pollution of the oil during arc extinction in the oil; due to the short opening and arcing time, low arc voltage, small arc energy consumption of the vacuum tube and the recondensation of the contact metal vapor, the contact burn and corrosion can be minimized. The power electronic on-load tap-changer replaces the vacuum tube with power electronic components to achieve no open circuit arc operation during the on-load switching process.

[0003] The on-load tap-changer is composed of a switching switch, a tap selector and an electric mechanism. Among them, the switching switch has an independent oil chamber and is the key component for the on-load tap-changer to achieve on-load switching. Its core is the adoption of a transition circuit. The vacuum on-load tap-changer can be divided into a single-contact circuit, a double-contact circuit, a triple-contact circuit and a quadruple-contact circuit according to the number of its vacuum tubes; there are two types of single-resistance and double-resistance transitions according to the number of its transition resistors; there are single-break and double-break contacts according to the number of its contact breaks; the above various combinations can form various vacuum on-load tap-changer transition circuits. The switching elements in the transition circuit can be single-break vacuum contacts, double-break vacuum contacts, power electronic components, etc.; different transition circuits have different switching timings to achieve on-load switching voltage regulation, and the switching tasks of each switching element will also be different. The topological structure of the transition circuit has an obvious impact on the reliability of the on-load tap-changer switching process, as well as the failure rate and electrical life of the switch.

[0004] In the transition circuit of on-load tap-changer, there are a load current vacuum circuit breaker that only undertakes the task of breaking the load current and a circulating current vacuum circuit breaker that only undertakes the task of breaking the inter-stage circulating current. In the actual UHV DC transmission project, the load current flowing through the on-load tap-changer of the converter transformer is about 500 - 600A, and the inter-stage circulating current flowing through the transition resistor during the switching process is about 900 - 1000A. The circulating current interrupted by the circulating current vacuum circuit breaker in a single interruption is significantly greater than the load current interrupted by the load current vacuum circuit breaker, resulting in an unbalanced interruption task between the load current vacuum circuit breaker and the circulating current vacuum circuit breaker. Summary of the Invention

[0005] The present invention proposes an on-load tap-changer series load single-resistor transition circuit and a voltage regulation method, which have the advantages of fewer transition resistors, dual configuration of both the circulating current vacuum circuit breaker and the load current vacuum circuit breaker, and alternately cutting off the current. The component distribution is symmetrical, and the switching time sequence is symmetrical, which can improve the reliability and switching efficiency of the on-load tap-changer.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] An on-load tap-changer series load single-resistor transition circuit includes a first main current-carrying switch and a second main current-carrying switch, a first switching element and a second switching element as circulating current breaking elements, a third switching element and a fourth switching element as load current switching elements, a change-over switch, and a transition resistor;

[0008] Wherein, the first end of the first main current-carrying switch is connected to the first end of the first switching element, the second end of the first main current-carrying switch is connected to the first end of the third switching element, the first end of the transition resistor, the first end of the fourth switching element, and the first end of the second main current-carrying switch. The second end of the first switching element and the second end of the third switching element are both connected to the first static contact of the change-over switch. The second end of the transition resistor is connected to the moving contact of the change-over switch. The second end of the second main current-carrying switch is connected to the first end of the second switching element, and the second ends of the second switching element and the fourth switching element are both connected to the second static contact of the change-over switch.

[0009] Further, it also includes a first disconnector, and the second end of the third switching element is connected to the first static contact of the change-over switch through the first disconnector.

[0010] Further, it also includes a second disconnector, and the second end of the fourth switching element is connected to the second static contact of the change-over switch through the second disconnector.

[0011] Further, the first switching element, the second switching element, the third switching element, and the fourth switching element are single-break vacuum circuit breakers, double-break vacuum circuit breakers, or power electronic components with controllable on-off functions.

[0012] Further, it further includes a on-load tap-changer regulating winding. The second end of the second main current-carrying switch and the first end of the second switching element are both connected to the tap of the second winding of the on-load tap-changer regulating winding, and the first end of the first main current-carrying switch and the first end of the first switching element are both connected to the tap N of the first winding of the on-load tap-changer regulating winding.

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

[0014] Further, the third switching element is used to interrupt the load current during the process of switching from the first winding tap to the second winding tap, and the fourth switching element is used to interrupt the load current during the process of switching from the second winding tap to the first winding tap;

[0015] The first switching element is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the first winding tap N to the second winding tap, and the second switching element is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the second winding tap to the first winding tap;

[0016] The transition resistor is used to limit the inter-stage circulating current during the switching of the transition circuit when the first winding tap and the second winding tap are bridged.

[0017] A voltage regulation method based on the above on-load tap-changer series load single-resistor transition circuit includes the following steps:

[0018] The first main current-carrying switch, the third switching element, and the first switching element are in the conducting state, and the second main current-carrying switch, the fourth switching element, and the second switching element are in the off state;

[0019] Disconnect the first main current-carrying switch, switch the transfer switch from the vacant position to the first stationary contact, conduct the second switching element, disconnect the third switching element, conduct the fourth switching element, disconnect the first switching element, switch the transfer switch from the first stationary contact to the vacant position, conduct the second main current-carrying switch, and the on-load tap-changer switches from the regulating first winding tap to the regulating second winding tap.

[0020] A voltage regulation method based on the above on-load tap-changer series load single-resistor transition circuit, where the second main current-carrying switch is in the conducting state, the first main current-carrying switch is in the off state, the fourth switching element is in the conducting state, the third switching element is in the off state, the second switching element is in the conducting state, and the first switching element is in the off state;

[0021] Disconnect the second main current-carrying switch, switch the transfer switch from the vacant position to the second static contact, turn on the first switching element, turn off the fourth switching element, turn on the third switching element, turn off the second switching element, switch the transfer switch from the second static contact to the vacant position, turn on the first main current-carrying switch, and the on-load tap-changer switches from the voltage-regulating second winding tap to the voltage-regulating first winding tap.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The present invention provides an on-load tap-changer series load single-resistance transition circuit and a voltage regulation method. There are two load current breaking elements in the transition circuit, which break the load current alternately; there are two circulating current breaking elements, which break the inter-stage circulating current during the on-load switching process alternately. The switching program is symmetrical, and the working loss degrees of the two circulating current breaking elements are the same, reducing the switching loss of the circulating current breaking elements, being able to balance the switching capacities of the load current breaking elements and the circulating current breaking elements, and greatly improving the electrical life of the on-load tap-changer.

[0024] Furthermore, a first disconnecting switch and a second disconnecting switch are provided in the circuit to play a role in disconnecting the circuit connection when the circuit breaker fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the circuit diagram of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0026] Figure 2 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0027] Figure 3 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0028] Figure 4 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0029] Figure 5 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0030] Figure 6 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0031] Figure 7 is the schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0032] Figure 8Schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0033] Figure 9 Schematic diagram of the switching process of the on-load tap-changer series load single-resistance transition circuit of the present invention;

[0034] Figure 10 Schematic diagram of the on-off states of each switch in the on-load tap-changer series load single-resistance transition circuit of the present invention during the process of the load switching from the winding tap N to the winding tap N + 1;

[0035] Figure 11 Schematic diagram of the on-off states of each switch in the on-load tap-changer series load single-resistance transition circuit of the present invention during the process of the load switching from the winding tap N + 1 to the winding tap N;

[0036] Figure 12 Circuit diagram of the on-load tap-changer series load single-resistance transition circuit with power electronic components as the switching elements according to an embodiment of the present invention;

[0037] Figure 13 Circuit diagram of the on-load tap-changer series load single-resistance transition circuit with double-break vacuum circuit breakers as the switching elements according to an embodiment of the present invention;

[0038] Figure 14 Circuit diagram of the on-load tap-changer series load single-resistance transition circuit according to the present invention, with an example disconnecting switch added to the circuit to achieve electrical isolation. Detailed implementation manners

[0039] The present invention will be described in detail below with reference to the accompanying drawings.

[0040] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] Figure 1 This is the circuit diagram of the on-load tap-changer series load single-resistance transition circuit of the present invention. As Figure 1 shown, the present invention provides an on-load tap-changer series load single-resistance transition circuit. There are two load current breaking elements in the transition circuit, which break the load current alternately; there are two circulating current breaking elements, which break the inter-stage circulating current during the on-load switching process. The switching program is symmetrical, and the working loss degrees of the two circulating current breaking elements are the same, which reduces the switching loss of the circulating current breaking elements, can balance the switching capacities of the load current breaking elements and the circulating current breaking elements, and greatly improves the electrical life of the on-load tap-changer.

[0043] Specifically, the on-load tap-changer series load single-resistance transition circuit of the present invention includes: a first main current-carrying switch MC1 and a second main current-carrying switch MC2, a first switching element V1 and a second switching element V2 as circulating current breaking elements, a third switching element V3 and a fourth switching element V4 as load current switching elements, a change-over switch T, and a transition resistor R.

[0044] Among them, the first end of the first main current-carrying switch MC1 is connected to the first end of the first switching element V1 and the first tapping of the voltage regulating first winding N. The second end of the first main current-carrying switch MC1 is connected to the neutral point lead-out end, the first end of the third switching element V3, the first end of the transition resistor R, the first end of the fourth switching element V4, the first end of the second main current-carrying switch MC2 and the neutral point lead-out end. The second end of the first switching element V1 and the second end of the third switching element V3 are both connected to the first static contact 11 of the change-over switch T. The second end of the transition resistor R is connected to the moving contact of the change-over switch T. The second end of the second main current-carrying switch MC2 is connected to the first end of the second switching element V2. The second end of the second switching element V2 and the second end of the fourth switching element V4 are both connected to the second static contact 12 of the change-over switch T.

[0045] The first terminal of the third switching element V3, the first terminal of the transition resistor R, the first terminal of the fourth switching element V4, the second terminal of the first main current-carrying switch MC1, and the first terminal of the second main current-carrying switch MC2 are all connected to the neutral point lead-out terminal of the on-load tap-changer.

[0046] The second terminal of the second main current-carrying switch MC2 and the first terminal of the second switching element V2 are both connected to the tap N+1 of the second regulating winding of the on-load tap-changer.

[0047] Preferably, it further includes a first disconnector Z1. The second terminal of the third switching element V3 is connected to the first static contact 11 of the change-over switch T via the first disconnector Z1.

[0048] Preferably, it further includes a second disconnector Z2. The second terminal of the fourth switching element V4 is connected to the second static contact 12 of the change-over switch T via the second disconnector Z2.

[0049] Preferably, the first switching element V1, the second switching element V2, the third switching element V3, and the fourth switching element V4 are single-break vacuum circuit breakers, double-break vacuum circuit breakers, or power electronic components with controllable on-off functions.

[0050] Specifically, the change-over switch T has a first static contact 11, a second static contact 12, and an operating arm (moving contact). The first static contact 11 is connected to one end of the first switching element V1 and one end of the third switching element V3. The other end of the first switching element V1 is the tap N of the first regulating winding. The second static contact 12 is connected to one end of the circulating current vacuum circuit breaker V2 and one end of the fourth switching element V4. The other end of the second switching element V2 is the tap N+1 of the second regulating winding. The operating arm is connected to either the first static contact 11 or the second static contact 12. The operating arm can also be in a vacant state, neither connected to the first static contact 11 nor the second static contact 12.

[0051] During use, the first main current-carrying switch MC1 is used for long-term carrying of the load current from the tap N of the first regulating winding of the on-load tap-changer to the neutral point lead-out terminal. The main current-carrying switch MC2 is used for long-term carrying of the load current from the tap N+1 of the second regulating winding of the on-load tap-changer to the neutral point lead-out terminal.

[0052] The third switching element V3 is used to break the load current during the switching from the tap N of the first winding to the tap N+1 of the second winding. The fourth switching element V4 is used to break the load current during the switching from the tap N+1 of the second winding to the tap N of the first winding.

[0053] The first switching element V1 is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the first winding tap N to the second winding tap N+1, and the second switching element V2 is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the second winding tap N+1 to the first winding tap N.

[0054] The transition resistor R is used to limit the inter-stage circulating current during the switching of the transition circuit when the first winding tap N and the second winding tap N+1 are bridged.

[0055] In the on-load tap-changer, additional disconnectors can be added at any position to achieve electrical isolation.

[0056] Specifically, the working process and principle of the on-load tap-changer series load single-resistor transition circuit of the present invention will be described in detail below with reference to the accompanying drawings: When the on-load tap-changer is in the first winding tap N, as Figure 1 shown, when the first main current-carrying switch MC1 is in the conducting state, the second main current-carrying switch MC2 is in the off state, the third switching element V3 is in the conducting state, the fourth switching element V4 is in the off state, the first switching element V1 is in the conducting state, the second switching element V2 is in the off state, the operating arm of the change-over switch T is vacant, and the on-load tap-changer transition circuit can make the load current flow out from the neutral point lead-out terminal through the first main current-carrying switch MC1.

[0057] When the on-load tap-changer switches from the first voltage-regulating winding tap N to the second voltage-regulating winding tap N+1, taking the first switching element V1, the second switching element V2, the third switching element V3, and the fourth switching element V4 as single-break vacuum circuit breakers as an example, the operation steps of the transition circuit include:

[0058] As Figure 2 shown, disconnect the first main current-carrying switch MC1, and the load current I N flows through the first switching element V1 and the third switching element V3 and flows out from the neutral point.

[0059] As Figure 3 shown, switch the operating arm of the change-over switch T from the vacant position to the first stationary contact 11.

[0060] As Figure 4 shown, turn on the second switching element V2.

[0061] As Figure 5 shown, disconnect the third switching element V3, cut off the load current I N , an arc is generated in the third switching element V3, and after the arc is extinguished, the load current I N flows out from the neutral point through the first switching element V1, the first stationary contact 11 of the change-over switch T, and the transition resistor R in sequence, and the recovery voltage U across the third switching element V3V1 = I N × R.

[0062] As Figure 6 shown, after the arc in the third switching element V3 is completely extinguished, turn on the fourth switching element V4, and the transition circuit is simultaneously connected to the first winding tap N and the second winding tap N+1 to form a bridge connection, generating an inter-stage circulating current I C = U S / R. At this time, the load current is transferred to flow out from the second winding tap N+1. The load current flows through the second switching element V2 and the fourth switching element V4 and flows out from the neutral point. The current in the first switching element V1 is the inter-stage circulating current I C .

[0063] As Figure 7 shown, turn off the first switching element V1 to cut off the inter-stage circulating current and generate an arc. The load current flows through the second switching element V2 and the fourth switching element V4 and flows out from the neutral point. The recovery voltage across the first switching element Vl is U V1 = U S .

[0064] As Figure 8 shown, after the arc in the first switching element V1 is completely extinguished, move the operating arm of the transfer switch T from the first stationary contact 11 to the vacant position. The load current flows through the second switching element V2 and the fourth switching element V4 and flows out from the neutral point.

[0065] As Figure 9 shown, close the second main current-carrying switch MC2. The load current I N flows out through the second main current-carrying switch MC2. At the same time, the second switching element V2 and the fourth switching element V4 are connected in parallel, and the switching operation from the voltage-regulating first winding tap N to the voltage-regulating second winding tap N+1 ends.

[0066] The second main current-carrying switch MC2 is in the on state, the first main current-carrying switch MC1 is in the off state, the fourth switching element V4 is in the on state, the third switching element V3 is in the off state, the second switching element V2 is in the on state, the first switching element V1 is in the off state, the operating arm of the transfer switch T is vacant, and the on-load tap-changer transition circuit can make the load current flow out from the neutral point terminal through the second main current-carrying switch MC2.

[0067] When the on-load tap-changer switches from the voltage-regulating second winding tap N+1 to the voltage-regulating first winding tap N, taking the first switching element V1, the second switching element V2, the third switching element V3, and the fourth switching element V4 as single-break vacuum circuit breakers as an example, the operation steps of the transition circuit include:

[0068] Turn off the second main current-carrying switch MC2. The load current IN flows out from the neutral point through the second switching element V2 and the fourth switching element V4;

[0069] Switch the operating arm of the change-over switch T from the vacant position to the second static contact 12;

[0070] Turn on the first switching element V1;

[0071] Disconnect the load current vacuum circuit breaker V4 to cut off the load current I N , an arc is generated in V4, and after the arc is extinguished, the load current I N flows out from the neutral point successively through the circulating current vacuum circuit breaker V2, the second static contact 12 of the change-over switch T, and the transition resistor R. The recovery voltage U across the load current vacuum circuit breaker V4 V1 = I N × R;

[0072] After the arc in the fourth switching element V4 is completely extinguished, turn on the third switching element V3. The transition circuit is simultaneously connected to the first winding tap N and the second winding tap N + 1 to form a bridge connection, generating an inter-stage circulating current I C = U S / R. At this time, the load current is transferred to flow out from the first winding tap N. The load current flows out from the neutral point through the first switching element V1 and the third switching element V3, and the current in the second switching element V2 is the inter-stage circulating current I C ;

[0073] Disconnect the second switching element V2 to cut off the inter-stage circulating current and generate an arc. The load current flows out from the neutral point through the first switching element V1 and the third switching element V3. The recovery voltage across the second switching element V2 is U V2 = U S ;

[0074] After the arc in the second switching element V2 is completely extinguished, switch the operating arm of the change-over switch T from the second static contact 12 to the vacant position. The load current flows out from the neutral point through the first switching element V1 and the third switching element V3;

[0075] Close the first main current-carrying switch MC1, and the load current I N flows out through the first main current-carrying switch MC1. At the same time, the first switching element V1 and the third switching element V3 are connected in parallel, and the switching operation from the second tapped winding of the voltage regulator N + 1 to the first tapped winding of the voltage regulator N ends.

[0076] When the internal switching elements in the on-load tap-changer series load single-resistor transition circuit are power electronic elements with controllable on-off functions and double-break vacuum circuit breakers, the action sequence and voltage regulation method of the switching elements are the same and will not be elaborated here.

[0077] When the on-load tap-changer switches from the tap N of the first winding to the tap N+1 of the second winding, the transition circuit conversion procedure is as follows Figure 10 as shown

[0078] When the on-load tap-changer switches from the tap N+1 of the second winding to the tap N of the first winding, the transition circuit conversion procedure is as follows Figure 11 as shown

[0079] In the embodiments of the present invention, the switching tasks of the on-load tap-changer transition circuit are shown in Table 1 below

[0080] Table 1 N to N+1 switching tasks of the on-load tap-changer transition circuit

[0081]

[0082] wherein, I N is the load current; U S is the inter-tap voltage of the on-load tap-changer; R is the transition resistance

[0083] See Figure 12 , which is the circuit diagram of the on-load tap-changer series load single-resistance transition circuit with a power electronic component as the switching element according to the embodiments of the present invention. Only replace the single-break vacuum circuit breaker in Figure 1 with a power electronic component with controllable on-off. The other components are the same as those in Figure 1 , the action timing is the same, and the functions and effects are also the same as those of the transition circuit shown in Figure 1 , so details are not described herein

[0084] See Figure 13 , which is the circuit diagram of the on-load tap-changer series load single-resistance transition circuit with a double-break vacuum circuit breaker as the switching element according to the embodiments of the present invention; only replace the single-break vacuum circuit breaker in Figure 1 with a double-break vacuum circuit breaker. The other components are the same as those in Figure 1 , the action timing is the same, and the functions and effects are also the same as those of the transition circuit shown in Figure 1 , so details are not described herein

[0085] See Figure 14 , which is the circuit diagram of the on-load tap-changer series load single-resistance transition circuit according to the present invention, with an example disconnector added to the circuit to play an electrical isolation role; the example first disconnector Z1 and the second disconnector Z2 are added to the circuit to disconnect the circuit connection when the circuit breaker fails. Adding disconnectors in other positions has the same effect, so details are not described herein

[0086] In one embodiment of the present invention, a voltage regulation method for a series-loaded single-resistance transition circuit of an on-load tap-changer is provided, including the following steps: Taking a single-break vacuum circuit breaker as an example, the transition circuit includes a first main current-carrying switch MC1, a second main current-carrying switch MC2, a third switching element V3, a fourth switching element V4, a first switching element V1, a second switching element V2, a transfer switch T, and a transition resistor R. The method is as follows:

[0087] The on-load tap-changer switches from the voltage regulation first winding tap N to the voltage regulation second winding tap N + 1, including:

[0088] The first main current-carrying switch MC1 is in the conducting state, the second main current-carrying switch MC2 is in the off state, the third switching element V3 is in the conducting state, the fourth switching element V4 is in the off state, the first switching element V1 is in the conducting state, the second switching element V2 is in the off state, and the moving arm of the transfer switch T is vacant;

[0089] Disconnect the first main current-carrying switch MC1;

[0090] Switch the transfer switch T from the vacant state to the first stationary contact 11;

[0091] Turn on the second switching element V2;

[0092] Disconnect the third switching element V3 to generate an arc;

[0093] After the arc in the third switching element V3 is completely extinguished, turn on the fourth switching element V4;

[0094] Disconnect the first switching element V1 to generate an arc;

[0095] After the arc in the first switching element V1 is completely extinguished, switch the transfer switch T from the first stationary contact 11 to the vacant state;

[0096] Turn on the second main current-carrying switch MC2.

[0097] The on-load tap-changer switches from the voltage regulation second winding tap N + 1 to the voltage regulation first winding tap N, including:

[0098] The second main current-carrying switch MC2 is in the conducting state, the first main current-carrying switch MC1 is in the off state, the fourth switching element V4 is in the conducting state, the third switching element V3 is in the off state, the second switching element V2 is in the conducting state, the first switching element V1 is in the off state, and the moving arm of the transfer switch T is vacant;

[0099] Disconnect the second main current-carrying switch MC2;

[0100] Switch the transfer switch T from the vacant state to the second stationary contact 12;

[0101] Turn on the first switching element V1;

[0102] Turn off the fourth switching element V4 to generate an arc;

[0103] After the arc in the fourth switching element V4 is completely extinguished, turn on the third switching element V3;

[0104] Turn off the second switching element V2 to generate an arc;

[0105] After the arc in the second switching element V2 is completely extinguished, switch the transfer switch T from the second stationary contact 12 to the vacant position;

[0106] Turn on the first main current-carrying switch MC1.

[0107] When the internal switching elements in the on-load tap-changer series load single-resistance transition circuit are power electronic elements with controllable on-off functions and double-break vacuum circuit breakers, the action timing and voltage regulation method of the switching elements are the same.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A voltage regulation method for a transition circuit of a on-load tap-changer with a series load single resistor, characterized in that, The voltage regulation method is based on a series-loaded single-resistance transition circuit of an on-load tap-changer. The transition circuit includes: a first main current-carrying switch (MC1) and a second main current-carrying switch (MC2), a first switching element (V1) and a second switching element (V2) serving as circulating current breaking elements, a third switching element (V3) and a fourth switching element (V4) serving as load current switching elements, a change-over switch (T), and a transition resistor (R). Among them, the first end of the first main current-carrying switch (MC1) is connected to the first end of the first switching element (V1). The second end of the first main current-carrying switch (MC1) is connected to the first end of the third switching element (V3), the first end of the transition resistor (R), the first end of the fourth switching element (V4), and the first end of the second main current-carrying switch (MC2). The second end of the first switching element (V1) and the second end of the third switching element (V3) are both connected to the first static contact (11) of the change-over switch (T). The second end of the transition resistor (R) is connected to the moving contact of the change-over switch (T). The second end of the second main current-carrying switch (MC2) is connected to the first end of the second switching element (V2). The second end of the second switching element (V2) and the second end of the fourth switching element (V4) are both connected to the second static contact (12) of the change-over switch T. The voltage regulation method includes the following steps: The first main current-carrying switch (MC1), the third switching element (V3), and the first switching element (V1) are placed in the conducting state, and the second main current-carrying switch (MC2), the fourth switching element (V4), and the second switching element (V2) are placed in the off state. Disconnect the first main current-carrying switch (MC1), switch the change-over switch (T) from the vacant position to the first static contact (11), conduct the second switching element (V2), disconnect the third switching element (V3), conduct the fourth switching element (V4), disconnect the first switching element (V1), switch the change-over switch (T) from the first static contact (11) to the vacant position, conduct the second main current-carrying switch (MC2), and the on-load tap-changer switches from the first voltage regulating winding tap (N) to the second voltage regulating winding tap (N + 1).

2. The voltage regulation method of a on-load tap-changer series load single resistor transition circuit according to claim 1, characterized in that, It also includes a first disconnector (Z1). The second end of the third switching element (V3) is connected to the first static contact (11) of the change-over switch (T) via the first disconnector (Z1).

3. The voltage regulation method of the on-load tap-changer series load single-resistance transition circuit according to claim 1 or 2, characterized in that, It also includes a second disconnector (Z2). The second end of the fourth switching element (V4) is connected to the second static contact (12) of the change-over switch (T) via the second disconnector (Z2).

4. The voltage regulation method of the on-load tap-changer series load single-resistance transition circuit according to claim 1, characterized in that, The first switching element (V1), the second switching element (V2), the third switching element (V3), and the fourth switching element (V4) are single-break vacuum circuit breakers, double-break vacuum circuit breakers, or power electronic components with controllable on-off functions.

5. The voltage regulation method of the on-load tap-changer series load single-resistance transition circuit according to claim 1, characterized in that, It further includes a on-load tap-changer regulating winding. The second end of the second main current-carrying switch (MC2) and the first end of the second switching element (V2) are both connected to the on-load tap-changer regulating second winding tap (N + 1), and the first end of the first main current-carrying switch (MC1) and the first end of the first switching element (V1) are both connected to the on-load tap-changer regulating first winding tap (N).

6. The voltage regulation method of the on-load tap-changer series load single-resistance transition circuit according to claim 1, characterized in that It further includes an on-load tap-changer. The first end of the third switching element (V3), the first end of the transition resistor (R), the first end of the fourth switching element (V4), the second end of the first main current-carrying switch (MC1), and the first end of the second main current-carrying switch (MC2) are all connected to the neutral point lead-out end of the on-load tap-changer.

7. The voltage regulation method of the on-load tap-changer series load single-resistance transition circuit according to claim 1, characterized in that, The third switching element (V3) is used to interrupt the load current during the process of switching from the first winding tap (N) to the second winding tap (N + 1), and the fourth switching element (V4) is used to interrupt the load current during the process of switching from the second winding tap (N + 1) to the first winding tap (N). The first switching element (V1) is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the first winding tap N to the second winding tap (N + 1), and the second switching element (V2) is used to interrupt the inter-stage circulating current during the bridging of the transition circuit when switching from the second winding tap (N + 1) to the first winding tap (N). The transition resistor (R) is used to limit the inter-stage circulating current when the first winding tap (N) and the second winding tap (N + 1) are bridged during the transition circuit switching process.

8. A voltage regulation method for a on-load tap-changer series load single-resistance transition circuit, characterized in that, The voltage regulation method is based on an on-load tap-changer series load single-resistor transition circuit. The transition circuit includes: the first main current-carrying switch (MC1) and the second main current-carrying switch (MC2), the first switching element (V1) and the second switching element (V2) as circulating current interruption elements, the third switching element (V3) and the fourth switching element (V4) as load current switching elements, a change-over switch (T), and a transition resistor (R). Among them, the first end of the first main current-carrying switch (MC1) is connected to the first end of the first switching element (V1). The second end of the first main current-carrying switch (MC1) is connected to the first end of the third switching element (V3), the first end of the transition resistor (R), the first end of the fourth switching element (V4), and the first end of the second main current-carrying switch (MC2). The second end of the first switching element (V1) and the second end of the third switching element (V3) are both connected to the first static contact (11) of the change-over switch (T). The second end of the transition resistor (R) is connected to the moving contact of the change-over switch (T). The second end of the second main current-carrying switch (MC2) is connected to the first end of the second switching element (V2). The second end of the second switching element (V2) and the second end of the fourth switching element (V4) are both connected to the second static contact (12) of the change-over switch T. The voltage regulation method includes the following steps: The second main current-carrying switch (MC2) is in the conducting state, the first main current-carrying switch (MC1) is in the off state, the fourth switching element (V4) is in the conducting state, the third switching element (V3) is in the off state, the second switching element (V2) is in the conducting state, and the first switching element (V1) is in the off state; Open the second main current-carrying switch (MC2), switch the transfer switch (T) from the vacant position to the second stationary contact (12), turn on the first switching element (V1), turn off the fourth switching element (V4), turn on the third switching element (V3), turn off the second switching element (V2), switch the transfer switch (T) from the second stationary contact (12) to the vacant position, turn on the first main current-carrying switch (MC1), and the on-load tap changer switches from the voltage regulating second winding tap (N + 1) to the voltage regulating first winding tap (N).

Images