A circuit breaker with a function of switching in and out a current limiting reactor (LR)

Abstract

The application provides a circuit breaker with a current limiting reactor LR switching function, comprising a mechanical switch K1, a first thyristor D1, a current limiting reactor LR, a coupling inductor LO and a power supply VDD; the positive pole of the mechanical switch K1 is connected with the current limiting reactor LR, the first thyristor D1 and the power supply VDD respectively; the negative pole of the mechanical switch K1 is connected with the current limiting reactor LR, the first thyristor D1 and a vacuum switch K2 through the primary side of the coupling inductor LO respectively; the negative pole of the vacuum switch K2 is connected with the negative pole of the power supply VDD through a load R. In the rated operation of the circuit breaker, the current only passes through the mechanical switch and the vacuum switch, so that the system loss is reduced and the energy transmission efficiency of the circuit breaker is improved; in the fault state, the current limiting reactor is put into operation, which can limit the rising rate of the system fault current, thereby providing favorable guarantee for the circuit breaker to remove the fault; and the rate of the fault transient current transferred from the mechanical switch to the current limiting reactor is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit breakers, in particular to a circuit breaker with a current limiting reactor LR switching function. BACKGROUND

[0002] With the wide application of DC power supply technology in new energy, electric vehicles, high voltage direct current transmission (HVDC) and DC microgrid, etc., the protection problem of DC system has been increasingly concerned. As a key protection device in the DC system, the DC mechanical circuit breaker can effectively cut off the fault current and protect the power equipment from damage.

[0003] However, compared with the AC system, the current in the DC system has no natural zero point, and the rapid rise of the fault current and the maintenance of the arc make the design and implementation of the DC circuit breaker face many challenges. The DC mechanical circuit breaker is an important fault isolation device in the DC system, mainly composed of a mechanical switch K1 and an auxiliary commutation loop. The mechanical switch K1, as the main current path, is responsible for breaking the DC fault current, while the auxiliary commutation loop is used to realize current commutation and energy dissipation. During the breaking process, the fault current is first transferred to the energy absorption element (such as resistance or metal oxide varistor MOV) through the auxiliary commutation loop, thereby reducing the current when the mechanical switch K1 breaks and reducing the difficulty of arc maintenance. After commutation is completed, the mechanical switch K1 is quickly disconnected to realize complete isolation of the circuit.

[0004] With the increase of fault breaking current in the DC system, higher requirements are put forward for the circuit breaker to break the fault. When a short circuit fault occurs in the DC system, the fault current rises rapidly, and if the fault is not isolated in time, it will cause serious harm to the system. As a current limiting device, the current limiting reactor LR can limit the rising rate of the fault current in the fault transient state. At present, the structure of the circuit breaker with current limiting function is to connect the current limiting reactor LR in series in the rated current circuit. When operating at rated current, the current limiting reactor LR flows through the rated current. Therefore, it will increase the loss of the circuit breaker and put higher requirements on the power of the current limiting reactor LR. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application provides a circuit breaker with a current limiting reactor LR switching function. The present application can make the current limiting reactor LR only work in the fault breaking state, and the current is conducted by the mechanical switch K1 when operating stably.

[0006] The technical scheme of the present application is: a circuit breaker with a current limiting reactor LR switching function, comprising a mechanical switch K1, a first thyristor D1, a current limiting reactor LR, a coupling inductor LO, and a power supply VDD; the positive pole of the mechanical switch K1 is connected with one end of the current limiting reactor LR, the anode of the first thyristor D1, and the positive pole of the power supply VDD respectively; the negative pole of the mechanical switch K1 is connected with one end of the primary side of the coupling inductor LO;

[0007] the other end of the primary side of the coupling inductor LO is connected with the negative pole of the power supply VDD through a load R.

[0008] As a preferred, the other end of the primary side of the coupling inductor LO is also connected with one end of an inductor L1, the other end of the inductor L1 is connected with the anode of a second thyristor D2 through a second capacitor C2; the cathode of the second thyristor D2 is connected with the negative pole of the power supply VDD through a load R.

[0009] As a preferred, the other end of the primary side of the coupling inductor LO is also connected with a lightning arrester F, the other end of the lightning arrester F is connected with the negative pole of the power supply VDD through a load R.

[0010] As a preferred, the secondary side of the coupling inductor LO is also connected with a third thyristor D3 and a first capacitor C1 in series.

[0011] As a preferred, when the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on; the first thyristor D1 and the second thyristor D2 are in an off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2.

[0012] When the circuit breaker is in a fault breaking state, the third thyristor D3 is triggered, the first capacitor C1 starts to discharge, and a voltage is induced on the primary side of the coupling inductor LO, therefore, the branch voltage of the mechanical switch K1 and the primary side of the coupling inductor LO rises, and then, by triggering the conduction and the off of the first thyristor D1, the current is commutated from the mechanical switch K1 to the current limiting reactor LR, so that the current limiting reactor LR plays a current limiting role.

[0013] The present application has the following advantages:

[0014] 1. When the circuit breaker of the present application is in a rated operation, the current only flows through the mechanical switch and the vacuum switch, which reduces the system loss and improves the energy transmission efficiency of the circuit breaker.

[0015] 2. When the circuit breaker of the present application is in a fault state, the current limiting reactor is put into operation, which can limit the rising rate of the system fault current, thereby providing a favorable guarantee for the circuit breaker to remove the fault.

[0016] 3. The present invention adopts a coordinated approach of a mechanical switch, a coupled inductor and a first thyristor to increase the rate at which the fault transient current is transferred from the mechanical switch to the current-limiting reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit structure diagram of the circuit breaker of the present invention;

[0018] Figure 2 This is a current waveform diagram of the mechanical switch K1 when simulating fault current interruption in an embodiment of the present invention;

[0019] Figure 3 This is a current waveform diagram of the first thyristor D1 when simulating fault current interruption in an embodiment of the present invention;

[0020] Figure 4 This is a current waveform diagram of the current limiting reactor LR when simulating fault current interruption in an embodiment of the present invention;

[0021] Figure 5 This is a current waveform diagram of the vacuum switch K2 when simulating fault current interruption according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0023] like Figure 1 As shown, the present invention provides a circuit breaker with a current limiting reactor LR switching function, comprising a mechanical switch K1, a first thyristor D1, a current limiting reactor LR, a coupling inductor LO, and a power supply VDD; the positive electrode of the mechanical switch K1 is respectively connected to one end of the current limiting reactor LR, the anode of the first thyristor D1, and the positive electrode of the power supply VDD; the negative electrode of the mechanical switch K1 is connected to one end of the primary side of the coupling inductor LO;

[0024] The other end of the primary side of the coupling inductor LO is connected to the current limiting reactor LR, the cathode of the first thyristor D1, and the positive electrode of the vacuum switch K2 respectively; the negative electrode of the vacuum switch K2 is connected to the negative electrode of the power supply VDD through the load R.

[0025] The other end of the primary side of the coupling inductor LO is also connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the anode of the second thyristor D2 via the second capacitor C2; the cathode of the second thyristor D2 is connected to the negative electrode of the power supply VDD via the load R.

[0026] The other end of the primary side of the coupling inductor LO is also connected to the lightning arrester F, and the other end of the lightning arrester F is connected to the negative electrode of the power supply VDD via the load R.

[0027] The coupling inductor LO secondary side is also connected in series with a third thyristor D3 and a first capacitor C1.

[0028] When the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on, and the first thyristor D1 and the second thyristor D2 are in an off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2.

[0029] When the circuit breaker is in a fault breaking state, when the system is in a fault breaking state, the mechanical switch K1 and the vacuum switch K2 start to open, and the first thyristor D1, the second thyristor D2 and the third thyristor D3 are triggered to be turned on. The coupling inductor LO primary side induces a voltage, and the voltage of the branch formed by the mechanical switch K1 rises, so that the current can be transferred from the mechanical switch K1 to the first thyristor D1. The first thyristor D1 is turned off when the current is zero, and the current is transferred to the current limiting reactor LR. The current limiting reactor LR plays a role of fault current limiting, thereby limiting the rise of the fault current. The second capacitor C2 starts to discharge after the second thyristor D2 is triggered to be turned on. When the capacitor discharge current is equal to the system fault current, the vacuum switch K2 current drops to 0 and is turned off. The system residual energy is dissipated through the arrester F, and when the system energy dissipation ends, the circuit breaker breaking is completed.

[0030] In order to verify the embodiment, a simulation model is built in simulation software to verify the breaking response of the system rated current 4kA and the circuit breaking fault current 40kA in the embodiment. In this simulation test, the power supply voltage is 1.5kV, the simulated circuit breaking fault occurs at t=50ms, and the circuit breaker starts to act at t=50ms.

[0031] From Figures 2 to 5 It can be seen that, due to the fast conduction of the first thyristor D1 in the fault state, the current of the mechanical switch K1 is quickly transferred to the first thyristor D1, and the current quickly drops to 0, and the current of the first thyristor D1 quickly rises. After the first thyristor D1 is turned off, the current is transferred to the current limiting reactor LR, and the current limiting reactor LR limits the rise rate of the fault current. After the vacuum switch K2 is broken, the current of the current limiting reactor LR drops to 0. In the simulation, the short-circuit current is set to 40kA, but in the actual breaking process, the circuit breaker starts to act when the fault current rises to about 5.5kA, and the current of the vacuum switch K2 gradually decreases to 0 and is turned off. The simulation verifies the current limiting effect of the current limiting reactor, and verifies the feasibility of the commutation mode of the embodiment.

[0032] Compared with the traditional mechanical vacuum circuit breaker, the circuit breaker with a current limiting reactor in the embodiment can limit the fault current rising rate, thereby reducing the harm of the fault current to the system. Compared with the method of directly connecting the current limiting reactor in series to the system, the current limiting reactor is switched in the embodiment, and the current limiting reactor only flows through the fault current in the fault breaking state, so that the circuit breaker has high energy transmission efficiency in the steady state operation, and the current limiting reactor only needs to conduct the fault transient current and does not need to work in the rated operation state for a long time, so that the power demand of the current limiting reactor can be reduced.

[0033] The above embodiments and descriptions in the specification are only to illustrate the principles and the best embodiments of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A circuit breaker with a line reactor (LR) switching function, characterized in that, It comprises a mechanical switch K1, a first thyristor D1, a current-limiting reactor LR, a coupling inductor LO and a power supply VDD; the positive pole of the mechanical switch K1 is connected with one end of the current-limiting reactor LR, the anode of the first thyristor D1 and the positive pole of the power supply VDD respectively; the negative pole of the mechanical switch K1 is connected with one end of the primary side of the coupling inductor LO; the other end of the primary side of the coupling inductor LO is connected with the negative pole of the power supply VDD through the second capacitor C2 and the anode of the second thyristor D2 respectively; the other end of the primary side of the coupling inductor LO is also connected with the lightning arrester F; the secondary side of the coupling inductor LO is also connected with the first capacitor C1 in series. When the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on; the first thyristor D1 and the second thyristor D2 are in an off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2; When the circuit breaker is in a fault breaking state, the mechanical switch K1 and the vacuum switch K2 start to open, the first thyristor D1, the second thyristor D2 and the third thyristor D3 are triggered to turn on; the voltage induced by the primary side of the coupling inductor LO rises, so the current is transferred from the mechanical switch K1 to the first thyristor D1, the first thyristor D1 is turned off when the current is zero, and the current is transferred to the current-limiting reactor LR, which plays a role of fault current limiting to limit the rise of the fault current; the second capacitor C2 starts to discharge after the second thyristor D2 is triggered to turn on, and the vacuum switch K2 is turned off when the capacitor discharge current is equal to the system fault current; The system residual energy is dissipated through the lightning arrester F, and the circuit breaker breaking is completed when the system energy dissipation ends.

2. The circuit breaker with a function of limiting reactor (LR) switching according to claim 1, characterized in that: The other end of the primary side of the coupling inductor LO is also connected with one end of the inductor L1, the other end of the inductor L1 is connected with the anode of the second thyristor D2 through the second capacitor C2; the cathode of the second thyristor D2 is connected with the negative pole of the power supply VDD through the load R.

3. The circuit breaker with a function of limiting reactor (LR) switching according to claim 2, characterized in that: The other end of the primary side of the coupling inductor LO is also connected with the lightning arrester F; the other end of the lightning arrester F is connected with the negative pole of the power supply VDD through the load R.

4. The circuit breaker with a current limiting reactor (LR) switching function according to claim 1, characterized in that: The secondary side of the coupling inductor LO is also connected with the first capacitor C1 in series. The secondary side of the coupling inductor LO is also connected with the first capacitor C1 in series.

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