Mechanical DC circuit breaker and method

Abstract

The mechanical direct-current circuit breaker is composed of a main current branch, a current transfer branch and an energy dissipation branch, the main current branch comprises a mechanical switch, an A side connected with one end of the mechanical switch and serving as a leading-in end to be connected with a high potential, and a B side connected with the other end of the mechanical switch and serving as a leading-out end to be connected with a low potential; the current transfer branch is connected with the main current branch in parallel, the current transfer branch comprises a multiplexing repulsion device, a thyristor and a capacitor which are connected in series, and the multiplexing repulsion device comprises a connecting rod connected with a mechanical switch contact, a repulsion disc connected with the connecting rod and a repulsion coil which is arranged above the repulsion disc and is used for electromagnetically driving the repulsion disc to move up and down; the repulsive force disc is connected with the mechanical switch contact through a connecting rod so as to drive the mechanical switch to be turned on and turned off through vertical movement of the repulsive force disc. The energy dissipation branch is connected in parallel with the main current branch, and the energy dissipation branch comprises a lightning arrester.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current circuit breakers, and in particular to a mechanical direct current circuit breaker and a method. Background Art

[0002] In today's context of growing energy demand and continuous optimization of energy structure, the power system is undergoing profound changes and development. As DC transmission technology has shown significant advantages in long-distance large-capacity transmission, new energy access, and urban power grid power supply, its application scope is becoming increasingly wide. However, the characteristics of the DC system itself also bring a series of extremely challenging problems to the design and operation of power equipment.

[0003] The fault current in the DC system rises very quickly. There is no natural zero crossing point in the DC system. Once the fault current is generated, it is difficult to extinguish itself. Traditional air-type DC circuit breakers have a long breaking time, large size, and high cost, while pure solid-state DC circuit breakers have large conduction losses and difficulty in heat dissipation, and often cannot meet the requirements of actual applications. Mechanical DC circuit breakers combine the advantages of both and can better cope with real-world applications. On the one hand, they can be quickly disconnected, and on the other hand, the rated current loss is significantly reduced. The present invention optimizes the circuit breaker structure, can reduce the switch load, and effectively improve the reliability of the circuit breaker.

[0004] For traditional mechanical DC circuit breakers, when opening the circuit breaker, it is necessary to control the current transfer branch to be conductive, the main current branch switch to be disconnected, and the current to be commutated from the main current branch of the circuit breaker to the current transfer branch. This process is carried out with the help of a pre-energy storage capacitor. During this process, the mechanical switch is subjected to arcing, which can easily cause damage to the switch, and the time should be minimized. The shutdown process requires that after the arc is extinguished at the break, the capacitor quickly builds up voltage, and then forces the current to be commutated to the energy dissipation branch. The break will be subjected to the rapidly built-up voltage after the arc is extinguished, which may cause the break to break, making it impossible to interrupt the current and causing commutation failure, which will have a serious impact on the circuit system.

[0005] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0006] In view of the deficiencies or defects of the above-mentioned prior art, a mechanical DC circuit breaker and method are provided, which can automatically disconnect the mechanical switch of the main current branch by utilizing the action of a repulsion disk during the commutation process, thereby accelerating the commutation speed and improving the circuit breaker's shut-off capability; the withstand voltage capability is improved by utilizing capacitors in combination with thyristor control; during the entire fault handling process, only the thyristor needs to be controlled to be turned on, thereby simplifying the control process, and the DC circuit breaker can remove the fault faster, more safely and more reliably.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A mechanical DC circuit breaker consists of a main current branch, a current transfer branch and an energy dissipation branch, wherein: The main current branch includes a mechanical switch, an A side connected to one end of the mechanical switch as an input terminal connected to a high potential, and a B side connected to the other end of the mechanical switch as an output terminal connected to a low potential; The current transfer branch is connected in parallel with the main current branch, and the current transfer branch includes a multiplexed repulsion device, a thyristor and a capacitor connected in series, and the multiplexed repulsion device includes a connecting rod connected to the mechanical switch contact, a repulsion disk connected to the connecting rod, and a repulsion coil arranged above the repulsion disk to electromagnetically drive the repulsion disk to move up and down, and the repulsion disk is connected to the mechanical switch contact through the connecting rod to drive the mechanical switch to be turned on and off through the up and down movement of the repulsion disk; The energy dissipation branch is connected in parallel with the main current branch, and the energy dissipation branch includes a lightning arrester.

[0009] In the mechanical DC circuit breaker, the capacitor is a pre-charge capacitor.

[0010] In the mechanical DC circuit breaker, the capacitor can withstand positive and reverse voltages.

[0011] In the mechanical DC circuit breaker, the connecting rod is made of insulating material, the repulsion disk is made of metal material and is insulated from the repulsion coil.

[0012] In the mechanical DC circuit breaker, the repulsion coil is fixed and a limiting component is provided in the downward movement stroke of the repulsion disk.

[0013] In the mechanical DC circuit breaker, the mechanical switch includes a vacuum high-speed mechanical switch, an air high-speed mechanical switch or a SF6 gas-filled high-speed mechanical switch.

[0014] In the mechanical DC circuit breaker, the thyristor is replaced by an IGBT component, an IGCT component, an IEGT component, a GTO component or other fully-controlled power devices and components thereof.

[0015] In the mechanical DC circuit breaker, the arrester includes a metal oxide arrester or a detachable arrester, and the metal oxide arrester includes a fully insulated composite jacket metal oxide arrester, a line type metal oxide arrester or a gapless line type metal oxide arrester.

[0016] The breaking method of the mechanical DC circuit breaker comprises the following steps: During normal operation, the mechanical switch of the main current branch is closed, and the system current flows through the mechanical switch to the lead-out terminal. At this time, the thyristor remains in a blocked state, the current transfer branch is disconnected, the capacitor has no closed loop and cannot be discharged, the voltage across the arrester does not reach its action value, and the arrester is in a high-impedance state, causing the energy dissipation branch to be disconnected; When a fault current occurs, the current in the main current branch increases. When it increases to the set value, an action command is sent, and the thyristor in the current transfer branch receives the action signal and turns on. The capacitor, the main current branch, the repulsion coil, and the thyristor form a closed loop, and the capacitor discharges through the closed loop. In this process, the current flowing through the repulsion coil increases, and a magnetic field with increased magnetic induction intensity is formed around it, and eddy currents are formed in the repulsion disk, thereby generating electromagnetic repulsion between the repulsion coil and the repulsion disk. The electromagnetic repulsion acts on the connecting rod to drive the mechanical switch of the main current branch to turn off, and an arc appears at the port of the mechanical switch. Current, and at the same time, the capacitor discharges in the main current branch to generate a current in the opposite direction to the fault current. The current in the main current branch drops to the zero point, and at this time, the opening distance of the mechanical switch break under the action of repulsion extinguishes the arc, the current in the main current branch drops to zero, the mechanical switch is turned off, and the fault current is transferred to the current transfer branch; under the action of the fault current, a forward voltage is formed at both ends of the capacitor of the current transfer branch and increases, and the voltage at both ends of the current transfer branch increases. When it increases to a predetermined degree, the lightning arrester is converted from a high-impedance state to a low-impedance state, the fault current is transferred to the energy dissipation branch, and the thyristor is turned off.

[0017] In the breaking method, when the current of the main current branch drops to zero, the repulsion disk is fixed so that it cannot move upward.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The capacitor of the present invention is discharged through the repulsion coil. On the one hand, a repulsion effect is generated between the repulsion coil and the repulsion disk, driving the mechanical switch to turn off; on the other hand, a reverse current is formed on the main current branch, which offsets the fault current, and can regulate the current change rate of the main current branch current when it passes through zero, thereby achieving reliable arc extinguishing, completing the fault current breaking and voltage establishment. When the fault current is switched to the capacitor branch, the capacitor is charged, and the capacitor directly provides the voltage for the current transfer branch to transfer to the energy dissipation branch, and the current transfer speed is faster. The capacitor is used in conjunction with the thyristor to control the discharge to the repulsion tripping coil, thereby improving the withstand voltage capability; the control process is simplified, and the DC circuit breaker handles faults faster, more conveniently and reliably.

[0019] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0021] In the attached picture: Figure 1 It is a topological schematic diagram of the present invention; Figure 2 It is a structural schematic diagram of the present invention; Figure 3(a) to Figure 3(d) 3(a) is a current schematic diagram of the present invention, wherein FIG3(b) is a current schematic diagram of normal flow, FIG3(c) is a current schematic diagram of the thyristor being turned on and the pre-charge capacitor being discharged, FIG3(d) is a current schematic diagram of the mechanical switch being opened, and FIG3(d) is a current schematic diagram of the current being commutated to the energy dissipation branch.

[0022] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0024] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0025] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0026] For a better understanding, Figure 1 to Figure 3(d) As shown, a mechanical DC circuit breaker consists of a main current branch, a current transfer branch and an energy dissipation branch, wherein: The main current branch includes a mechanical switch, an A side connected to one end of the mechanical switch as an input terminal connected to a high potential, and a B side connected to the other end of the mechanical switch as an output terminal connected to a low potential; The current transfer branch is connected in parallel with the main current branch, and the current transfer branch includes a multiplexed repulsion device, a thyristor and a capacitor connected in series, and the multiplexed repulsion device includes a connecting rod connected to the mechanical switch contact, a repulsion disk connected to the connecting rod, and a repulsion coil arranged above the repulsion disk to electromagnetically drive the repulsion disk to move up and down, and the repulsion disk is connected to the mechanical switch contact through the connecting rod to drive the mechanical switch to be turned on and off through the up and down movement of the repulsion disk; The energy dissipation branch is connected in parallel with the main current branch, and the energy dissipation branch includes a lightning arrester.

[0027] In a preferred embodiment of the mechanical DC circuit breaker, the capacitor is a pre-charge capacitor.

[0028] In a preferred embodiment of the mechanical DC circuit breaker, the capacitor can withstand positive and reverse voltages.

[0029] In a preferred embodiment of the mechanical DC circuit breaker, the connecting rod is made of an insulating material, and the repulsion disk is made of a metal material and is insulated from the repulsion coil.

[0030] In a preferred embodiment of the mechanical DC circuit breaker, the repulsion coil is fixed and a limiting component is provided in the downward movement stroke of the repulsion disk.

[0031] In a preferred embodiment of the mechanical DC circuit breaker, the mechanical switch includes a vacuum high-speed mechanical switch, an air high-speed mechanical switch or a SF6 gas-filled high-speed mechanical switch.

[0032] In a preferred embodiment of the mechanical DC circuit breaker, the thyristor is replaced by an IGBT component, an IGCT component, an IEGT component, a GTO component or other fully-controlled power devices and components thereof.

[0033] In a preferred embodiment of the mechanical DC circuit breaker, the arrester includes a metal oxide arrester or a detachable arrester, and the metal oxide arrester includes a fully insulated composite jacket metal oxide arrester, a line type metal oxide arrester or a gapless line type metal oxide arrester.

[0034] The breaking method of the mechanical DC circuit breaker includes the following steps: During normal operation, the mechanical switch of the main current branch is closed, and the system current flows through the mechanical switch to the lead-out terminal. At this time, the thyristor remains in a blocked state, the current transfer branch is disconnected, the capacitor has no closed loop and cannot be discharged, the voltage across the arrester does not reach its action value, and the arrester is in a high-impedance state, causing the energy dissipation branch to be disconnected; When a fault current occurs, the current in the main current branch increases. When it increases to the set value, an action command is sent, and the thyristor in the current transfer branch receives the action signal and turns on. The capacitor, the main current branch, the repulsion coil, and the thyristor form a closed loop, and the capacitor discharges through the closed loop. In this process, the current flowing through the repulsion coil increases, and a magnetic field with increased magnetic induction intensity is formed around it, and eddy currents are formed in the repulsion disk, thereby generating electromagnetic repulsion between the repulsion coil and the repulsion disk. The electromagnetic repulsion acts on the connecting rod to drive the mechanical switch of the main current branch to turn off, and an arc appears at the port of the mechanical switch. Current, and at the same time, the capacitor discharges in the main current branch to generate a current in the opposite direction to the fault current. The current in the main current branch drops to the zero point, and at this time, the opening distance of the mechanical switch break under the action of repulsion extinguishes the arc, the current in the main current branch drops to zero, the mechanical switch is turned off, and the fault current is transferred to the current transfer branch; under the action of the fault current, a forward voltage is formed at both ends of the capacitor of the current transfer branch and increases, and the voltage at both ends of the current transfer branch increases. When it increases to a predetermined degree, the lightning arrester is converted from a high-impedance state to a low-impedance state, the fault current is transferred to the energy dissipation branch, and the thyristor is turned off.

[0035] In a preferred implementation of the breaking method, when the current in the main current branch drops to zero, the repulsion disk is fixed so that it cannot move upward.

[0036] In one embodiment, the mechanical DC circuit breaker is composed of a main current branch, a current transfer branch, an energy dissipation branch and a repulsion device. The main current branch is composed of a mechanical switch, which is mainly responsible for the normal flow of the circuit; the current transfer branch is composed of a repulsion coil, a thyristor and a pre-charge capacitor; the energy dissipation branch is composed of a lightning arrester; the repulsion device is composed of a repulsion disk and a connecting rod. The specific structure of the single current direction is as follows Figure 2 shown.

[0037] (1) The main current branch, current transfer branch and energy dissipation branch are connected in parallel. Side A is connected to a high potential as the lead-in end, and side B is connected to a low potential as the lead-out end.

[0038] (2) The repulsion disk is connected to the mechanical switch contact through a connecting rod. The repulsion disk can drive the mechanical switch to turn on and off by moving it up and down, and the connecting rod is insulated and non-conductive.

[0039] (3) The repulsion disk is made of metal material and is placed under the repulsion coil and insulated from the repulsion coil. The repulsion coil is fixed and the repulsion disk can be moved up and down. It should be ensured that the repulsion disk will be stuck and cannot move upward freely after moving downward a sufficient distance. The upward movement can be controlled after the fault is eliminated.

[0040] (4) The capacitor is a pre-charged capacitor and can withstand positive and reverse voltages.

[0041] Figure 3(a) to Figure 3(d) This is a flow chart of the breaking principle of the circuit breaker in the present invention. As shown in Figure 3(a), when the system is working normally, the mechanical switch of the main current branch is closed, and the system current flows through the mechanical switch to the lead-out terminal. At this time, the thyristor is turned off, the current transfer branch is equivalent to an open circuit, and the pre-charge capacitor has no closed loop and cannot be discharged. At this time, the voltage across the lightning arrester is relatively small, and the lightning arrester is in a high-impedance state, which is equivalent to an open circuit.

[0042] As shown in Figure 3(b), when a fault current occurs, the current in the main circuit increases rapidly. When it increases to a certain set value, the host computer sends an action command, and the thyristor of the current transfer branch receives the action signal and turns on. The pre-charge capacitor forms a closed loop with the main current branch, the repulsion coil, and the thyristor, and the pre-charge capacitor discharges through this loop. In this process, the current flowing through the repulsion coil increases, and a magnetic field with increased magnetic induction intensity is formed around it, and eddy currents are formed in the repulsion disk, thereby generating a strong electromagnetic repulsion between the repulsion coil and the repulsion disk. The repulsion acts on the connecting rod to drive the mechanical switch of the main current branch to turn off, but due to the existence of the main current branch current, an arc current will appear at the mechanical switch port. At the same time, the discharge of the pre-charge capacitor generates a current in the main current loop that is opposite to the fault current. The current of the main current branch drops rapidly to the zero point, and at this time, under the action of the repulsion force, the mechanical switch break has a sufficient opening distance, the arc is extinguished, the mechanical switch is turned off, the current of the main current branch drops to zero, and the fault current is transferred to the current transfer branch. At this time, the repulsion disk is fixed so that it cannot move upward.

[0043] Subsequently, as shown in Figure 3(c), the mechanical switch opens and the fault current is transferred to the current transfer branch. Under the action of the fault current, a positive voltage is formed at both ends of the capacitor of the current transfer branch and gradually increases. The voltage at both ends of the current transfer branch gradually increases. When it increases to a certain extent, the arrester changes from a high-resistance state to a low-resistance state, and the fault current gradually transfers to the energy dissipation branch.

[0044] Finally, as shown in Figure 3(d), the fault current is transferred to the energy dissipation branch, the thyristor is turned off, and the excess energy of the system is released through the energy dissipation branch, completing the fault current removal.

[0045] The mechanical switch is a high-speed mechanical switch, and a vacuum high-speed mechanical switch, an air high-speed mechanical switch, a SF6 or other gas-filled high-speed mechanical switch with arc extinguishing capability can be used. The thyristor components used in the main current branch and the current transfer branch can be replaced by IGBT components, IGCT components, IEGT components, GTO components or other fully-controlled power devices and their components. The energy dissipation circuit includes but is not limited to a single or multiple combination of the following devices: metal oxide arresters, line-type metal oxide arresters, gapless line-type metal oxide arresters, fully insulated composite jacket metal oxide arresters, and removable arresters.

[0046] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0047] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A mechanical DC circuit breaker, characterized in that: It consists of the main current branch, the current transfer branch and the energy dissipation branch, among which, The main current branch includes a mechanical switch, an A side connected to one end of the mechanical switch as an input terminal connected to a high potential, and a B side connected to the other end of the mechanical switch as an output terminal connected to a low potential; The current transfer branch is connected in parallel with the main current branch, and the current transfer branch includes a multiplexed repulsion device, a thyristor and a capacitor connected in series, and the multiplexed repulsion device includes a connecting rod connected to the mechanical switch contact, a repulsion disk connected to the connecting rod, and a repulsion coil arranged above the repulsion disk to electromagnetically drive the repulsion disk to move up and down, and the repulsion disk is connected to the mechanical switch contact through the connecting rod to drive the mechanical switch to be turned on and off through the up and down movement of the repulsion disk; The energy dissipation branch is connected in parallel with the main current branch, and the energy dissipation branch includes a lightning arrester.

2. The mechanical DC circuit breaker according to claim 1, characterized in that: Preferably, the capacitor is a pre-charge capacitor.

3. The mechanical DC circuit breaker according to claim 1, characterized in that: The capacitor can withstand positive and reverse voltages.

4. The mechanical DC circuit breaker according to claim 1, characterized in that: The connecting rod is made of insulating material, and the repulsion disk is made of metal material and is insulated from the repulsion coil.

5. The mechanical DC circuit breaker according to claim 1, characterized in that: The repulsion coil is fixed and a limiting component is provided in the downward moving stroke of the repulsion disc.

6. The mechanical DC circuit breaker according to claim 1, characterized in that: The mechanical switch includes a vacuum high-speed mechanical switch, an air high-speed mechanical switch or a SF6 gas-filled high-speed mechanical switch.

7. The mechanical DC circuit breaker according to claim 1, characterized in that: The thyristor is replaced by an IGBT component, an IGCT component, an IEGT component, a GTO component or other fully-controlled power devices and components thereof.

8. The mechanical DC circuit breaker according to claim 1, characterized in that: The arrester includes a metal oxide arrester or a detachable arrester, and the metal oxide arrester includes a fully insulated composite jacket metal oxide arrester, a line type metal oxide arrester or a gapless line type metal oxide arrester.

9. The method for breaking a mechanical DC circuit breaker according to any one of claims 1 to 8, characterized in that: It includes the following steps, During normal operation, the mechanical switch of the main current branch is closed, and the system current flows through the mechanical switch to the lead-out terminal. At this time, the thyristor remains in a blocked state, the current transfer branch is disconnected, the capacitor has no closed loop and cannot be discharged, the voltage across the arrester does not reach its action value, and the arrester is in a high-impedance state, causing the energy dissipation branch to be disconnected; When a fault current occurs, the current in the main current branch increases. When it increases to the set value, an action command is sent. The thyristor in the current transfer branch receives the action signal and turns on. The capacitor forms a closed loop with the main current branch, the repulsion coil, and the thyristor. The capacitor discharges through the closed loop. In this process, the current flowing through the repulsion coil increases, and a magnetic field with increased magnetic induction intensity is formed around it, and eddy currents are formed in the repulsion disk, thereby generating an electromagnetic repulsion between the repulsion coil and the repulsion disk. The electromagnetic repulsion acts on the connecting rod to drive the mechanical switch of the main current branch to turn off, and an arc current appears at the port of the mechanical switch. At the same time, the capacitor discharges in the main current branch to generate a current in the opposite direction of the fault current. The current in the main current branch drops to the zero point, and at this time, the opening distance of the mechanical switch break under the action of the repulsion force causes the arc to extinguish, the current in the main current branch drops to zero, the mechanical switch is turned off, and the fault current is transferred to the current transfer branch. Under the action of the fault current, a forward voltage is formed at both ends of the current transfer branch capacitor and increases, and the voltage at both ends of the current transfer branch increases. When it increases to a predetermined level, the lightning arrester changes from a high-resistance state to a low-resistance state, the fault current is transferred to the energy dissipation branch, and the thyristor is turned off.

10. The breaking method according to claim 9, characterized in that: When the current in the main current branch drops to zero, the repulsion disk is fixed so that it cannot move upward.

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