Device and method for measuring voltage across a break of a direct current circuit breaker

Abstract

The application relates to a device and a method for measuring the voltage across the break of a direct current circuit breaker, wherein the freewheeling module comprises a diode D1 and a diode D2 connected in reverse series to measure the voltage in different directions generated across the break of the direct current circuit breaker under different working conditions; the energy releasing module comprises a resistor R1 and a resistor R2 connected in series; the bidirectional high-voltage pulse absorption module comprises a capacitor C1 and a capacitor C2 for absorbing the voltage impact in different directions borne by the break of the direct current circuit breaker, respectively; the energy releasing module and the freewheeling module are connected in parallel and then connected in series with the bidirectional high-voltage pulse absorption module; the voltage isolation sampling module comprises a front-stage sampling resistor R5, a linear photoelectric coupler and a rear-stage sampling resistor R6, the front-stage sampling resistor R5 is connected with the front stage of the linear photoelectric coupler, and the rear-stage sampling resistor R6 is connected with the rear stage of the linear photoelectric coupler.

Description

Technical Field

[0001] This invention belongs to the field of voltage measurement technology for switching electrical equipment, and in particular, it is a device and method for measuring the voltage across the terminals of a DC circuit breaker. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission systems have attracted widespread attention due to their superior performance in renewable energy integration, power system expansion, and improved grid stability. DC circuit breakers, especially medium- and high-voltage DC circuit breakers, are the backbone equipment in DC power systems, responsible for switching operating modes and clearing line faults, and are crucial for ensuring the safe, economical, and flexible operation of DC power systems. Particularly in the rail transit sector, DC circuit breakers are indispensable key protective devices for track traction DC power supply systems. With the large-scale construction of rail transit, the application of track traction DC power supply systems is becoming increasingly widespread, leading to a growing demand for medium- and high-voltage DC circuit breakers with good breaking capacity.

[0003] Arc voltage is an important parameter that can largely reflect the arc-extinguishing performance of medium and high voltage DC circuit breakers. Furthermore, arc voltage can accurately reflect the operating state of the circuit breaker's moving and stationary contacts during the opening process. This is beneficial for the design and development of many artificial zero-crossing type high-voltage, high-capacity DC circuit breakers. Therefore, its measurement has been of great interest to numerous researchers and engineering designers for many years.

[0004] However, in current practical engineering applications, due to the high system voltage levels of DC circuit breakers (taking medium and high voltage DC circuit breakers as examples, their system voltage is at least in the kilovolt range and can even reach tens of kilovolts), once the circuit breaker performs an opening operation, the voltage across the moving and stationary contacts is the corresponding system voltage. Therefore, ordinary low-voltage measurement methods cannot be used to measure the voltage across the moving and stationary contacts. However, if high-voltage measurement methods such as high-voltage probes are used, considering the large range and high graduation of high-voltage probes, it is difficult to guarantee the accuracy of the results when measuring the arc voltage between the moving and stationary contacts formed during the opening process of the circuit breaker, and the error is large.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention proposes a device and method for measuring the voltage across the terminals of a DC circuit breaker. This overcomes the defects and deficiencies of existing measuring devices or instruments, and can accurately measure the arc voltage between the moving and stationary contacts of the circuit breaker during the opening process. It can also withstand the system voltage applied across the terminals of the moving and stationary contacts after the circuit breaker has completed opening, protecting the downstream measuring circuit from damage caused by the high system voltage.

[0007] The objective of this invention is achieved through the following technical solution: a device for measuring the voltage across the terminals of a DC circuit breaker includes a freewheeling module, an energy dissipation module, a bidirectional high-voltage pulse absorption module, a multi-stage surge protection module, and a voltage isolation sampling module, wherein...

[0008] The freewheeling module includes diodes D1 and D2 connected in reverse series to measure the voltage in different directions generated at both ends of the DC circuit breaker under different operating conditions.

[0009] The energy dissipation module includes resistors R1 and R2 connected in series;

[0010] The bidirectional high-voltage pulse absorption module includes capacitors C1 and C2, which absorb voltage surges from different directions at both ends of the DC circuit breaker. The energy dissipation module and the freewheeling module are connected in parallel and then connected in series with the bidirectional high-voltage pulse absorption module. Resistors R1 and R2 serve as energy dissipation resistors for capacitors C1 and C2, respectively.

[0011] The multi-level surge protection module includes,

[0012] The first-level surge protection module includes a varistor RV1, a varistor RV2 and a gas discharge tube. The varistor RV1 and varistor RV2 are connected in series. One end of the gas discharge tube is connected to the equipotential connection point of the varistor RV1 and varistor RV2, and the other end is grounded.

[0013] The second-level surge protection module includes safety capacitors C3 and C4 connected in series, wherein the equipotential bonding point of safety capacitors C3 and C4 is grounded.

[0014] The third-level surge protection module includes a transient voltage suppression diode (TVS) connected in parallel across the second-level surge protection module.

[0015] The voltage isolation sampling module includes a front-stage sampling resistor R5, a linear optocoupler, and a rear-stage sampling resistor R6. The front-stage sampling resistor R5 is connected to the front stage of the linear optocoupler, and the rear-stage sampling resistor R6 is connected to the rear stage of the linear optocoupler.

[0016] In the device for measuring the voltage across the DC circuit breaker terminals, a current-limiting resistor R3 and a current-limiting resistor R4 are respectively provided between the bidirectional high-voltage pulse absorption module and the varistor RV1 and varistor RV2.

[0017] In the device for measuring the voltage across the terminals of a DC circuit breaker, diode D3 is connected between current-limiting resistor R3 and varistor RV1, and diode D4 is connected between current-limiting resistor R4 and varistor RV2.

[0018] In the device for measuring the voltage across the DC circuit breaker terminals, diodes D3 and D4 are further included between the first-stage surge protection module and the second-stage surge protection module to limit the current flow in the circuit.

[0019] In the device for measuring the voltage across the terminals of a DC circuit breaker, the current-limiting resistors R3 and R4 have equal values ​​and are not higher than the kiloohm level.

[0020] In the device for measuring the voltage across the terminals of a DC circuit breaker, the resistor R1, capacitor C1, current-limiting resistor R3, varistor RV1, varistor RV2, current-limiting resistor R4, capacitor C2, and resistor R2 are connected in series to form a loop.

[0021] In the device for measuring the voltage across the terminals of a DC circuit breaker, the values ​​of resistors R1 and R2 are not less than megaohms; the values ​​of capacitors C1 and C2 are equal and not less than microfarads.

[0022] In the device for measuring the voltage across the DC circuit breaker terminals, the operating voltage thresholds of the varistor RV1 and varistor RV2 are consistent and higher than the operating voltage threshold of the gas discharge tube.

[0023] In the device for measuring the voltage across the terminals of a DC circuit breaker, the safety capacitor C3 is the same as the safety capacitor C4.

[0024] The measurement method of the device for measuring the voltage across the terminals of a DC circuit breaker includes the following steps:

[0025] S1: Connect the device for measuring the voltage across the DC circuit breaker contacts to the moving and stationary contacts of the DC circuit breaker. At this time, the voltage across the contacts is Uab.

[0026] S2: When the DC circuit breaker is closed, the voltage at the break point Uab = 0;

[0027] S3: When the DC circuit breaker trips;

[0028] If the DC circuit breaker interrupts a forward current, the break voltage Uab > 0. At this time, the two ends of the DC circuit breaker break start from the arcing state, and the break voltage Uab is the arc voltage. Diode D1 is cut off under reverse voltage, and diode D2 is turned on under forward voltage. Since the arc voltage is less than the operating voltage of each stage of surge protection module, the break voltage Uab signal passes through capacitor C1, current limiting resistor R3, and diode D3 to reach the front-stage sampling resistor R5. The linear optocoupler transmits the voltage signal on the front-stage sampling resistor R5 to the rear-stage sampling resistor R6 through photoelectric conversion. There is a fixed transmission ratio between the voltage values ​​of the front and rear-stage sampling resistors. By measuring the voltage value of the rear-stage sampling resistor R6, the arc voltage at both ends of the DC circuit breaker moving and stationary contacts is measured.

[0029] When the DC circuit breaker extinguishes the arc, the voltage across the break point is equal to the system voltage. Its value is greater than the operating voltage of each level of surge protection module. The varistor, gas discharge tube, and transient voltage suppression tube operate to limit the voltage step by step, ultimately clamping the voltage of the back-end sampling resistor R6 within the acceptable range, protecting the linear optocoupler and the back-end measurement circuit from damage by the system voltage.

[0030] When the system voltage drops, capacitor C1 releases the stored energy through the energy discharge circuit formed by energy discharge resistor R1, varistor RV1, and current limiting resistor R3, in preparation for the next measurement.

[0031] If the DC circuit breaker interrupts the reverse current, the break voltage Uab < 0. The two ends of the DC circuit breaker break start from the arcing state. Diode D1 is forward-biased and conducts, while diode D2 is reverse-biased and cut off. The break voltage Uab signal passes through capacitor C2, current-limiting resistor R4, and diode D4 to reach the front-end sampling resistor R5.

[0032] After the DC circuit breaker extinguishes the arc, the varistor, gas discharge tube, and transient voltage suppressor activate to limit the voltage step by step, ultimately clamping the voltage of the downstream sampling resistor R6 within the acceptable range, protecting the linear optocoupler and downstream measurement circuit from damage by high voltage.

[0033] When the system voltage drops, capacitor C2 releases the stored energy through the energy discharge circuit formed by the energy discharge resistor R2, the varistor RV2, and the current limiting resistor R4, in preparation for the next measurement.

[0034] Compared with existing technologies, the present invention has the following advantages: The device for measuring the voltage across the contacts of a DC circuit breaker described in this invention acquires the arc voltage signal across the moving and stationary contacts during the opening process of the DC circuit breaker through a front-stage sampling resistor R5 before the linear optocoupler. The signal is then converted by photoelectric conversion through the linear optocoupler, transmitting the analog voltage across the front-stage sampling resistor R5 to the rear-stage sampling resistor R6. This achieves the measurement objective while ensuring electrical isolation between the front and rear measurement circuits, reducing interference. Furthermore, the high-voltage pulse absorption module, in conjunction with the first-stage surge protection module, the second-stage surge protection module, and the third-stage surge protection module, jointly suppresses the damage to the measuring device caused by the system voltage across the moving and stationary contacts after the DC circuit breaker opens, protecting the entire measuring device and the safety of the operators. Attached Figure Description

[0035] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0036] In the attached diagram:

[0037] Figure 1 This is a schematic diagram of a device for measuring the voltage across the terminals of a DC circuit breaker according to an embodiment of the present invention.

[0038] Figures 2(a) to 2(b) Figure 2(a) is a schematic flowchart of a measurement method for a device for measuring the voltage across the terminals of a DC circuit breaker according to an embodiment of the present invention. Figure 2(b) shows the measurement process of the arc voltage at the terminals during the opening of the moving and stationary contacts of the DC circuit breaker; Figure 2(c) shows the operation of the measurement device when the terminals are subjected to system voltage after the opening of the moving and stationary contacts of the DC circuit breaker.

[0039] Figure 3 This is a schematic diagram of the test measurement results of a device for measuring the voltage across the terminals of a DC circuit breaker according to an embodiment of the present invention under arcing conditions.

[0040] Figure 4 This is a schematic diagram of the test measurement results of a device for measuring the voltage across the terminals of a DC circuit breaker according to an embodiment of the present invention under arcing conditions.

[0041] Figure 5This is a schematic diagram of the test measurement results of a device for measuring the voltage across the terminals of a DC circuit breaker according to an embodiment of the present invention under simulated high-voltage impact on the system.

[0042] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0043] The following will refer to the appendix. Figures 1 to 5 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0044] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0045] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0046] To better understand, such as Figures 1 to 2(b) As shown, the device for measuring the voltage across the DC circuit breaker terminals includes a freewheeling module, a discharge module, a bidirectional high-voltage pulse absorption module, a multi-stage surge protection module, and a voltage isolation sampling module.

[0047] The freewheeling module consists of diodes D1 and D2 connected in reverse series, and is used to provide a freewheeling circuit for measuring the voltages in different directions generated at both ends of the DC circuit breaker under different operating conditions.

[0048] The energy dissipation module consists of resistors R1 and R2 connected in series. After being connected in series, they are connected in parallel with the freewheeling module, and then connected in series with the high-voltage pulse absorption module. Resistors R1 and R2 serve as energy dissipation resistors for capacitors C1 and C2, respectively, providing them with an energy dissipation circuit.

[0049] The bidirectional high-voltage pulse absorption module consists of capacitor C1 and capacitor C2, which respectively absorb voltage surges from different directions experienced by the two ends of the DC circuit breaker.

[0050] The first-stage surge protection module consists of a varistor RV1, a varistor RV2, and a gas discharge tube. The varistor RV1 and varistor RV2 are connected in series, and one end of the gas discharge tube is connected to the equipotential junction of the varistor RV1 and varistor RV2, while the other end is grounded.

[0051] The second-level surge protection module consists of safety capacitor C3 and safety capacitor C4 connected in series, wherein the equipotential bonding point of C3 and C4 is grounded;

[0052] The third-level surge protection module is composed of transient voltage suppression diodes (TVS), which are connected in parallel across the second-level surge protection module.

[0053] The voltage isolation sampling module consists of a front-end sampling resistor R5, a linear optocoupler, and a rear-end sampling resistor R6. R5 is connected to the front end of the linear optocoupler, and R6 is connected to the rear end of the linear optocoupler.

[0054] The device for measuring the voltage across the DC circuit breaker terminals includes a current-limiting resistor R3 and a current-limiting resistor R4 between the bidirectional high-voltage pulse absorption module and the varistor.

[0055] In the device for measuring the voltage across the DC circuit breaker terminals, between the first-stage surge protection module and the second-stage surge protection module, diodes D3 and D4 are also included to limit the current flow in the circuit.

[0056] In the device for measuring the voltage across the DC circuit breaker terminals, the values ​​of resistors R1 and R2 in the energy dissipation module must not be lower than the megaohm level; the values ​​of capacitors C1 and C2 in the high-voltage pulse absorption module must be equal and not lower than the microfarad level.

[0057] In the device for measuring the voltage across the DC circuit breaker terminals, the operating voltage thresholds of varistor RV1 and varistor RV2 in the first-stage surge protection module should be consistent and slightly higher than the operating voltage threshold of the gas discharge tube; the safety capacitors C3 and C4 in the second-stage surge protection module should have the same specifications; and the operating voltage threshold of the transient voltage suppression diode in the third-stage surge protection module should be selected below the withstand limit of the downstream circuit.

[0058] In the device for measuring the voltage across the DC circuit breaker terminals, the values ​​of the current-limiting resistor R3 and the current-limiting resistor R4 are equal and cannot exceed the kiloohm level.

[0059] In one embodiment, the device for measuring the voltage across the DC circuit breaker terminals includes a freewheeling module, an energy dissipation module, a bidirectional high-voltage pulse absorption module, a multi-stage surge protection module, and a voltage isolation sampling module.

[0060] In this embodiment, as Figure 1 As shown, the freewheeling module consists of diodes D1 and D2 connected in reverse series, and is used to provide a freewheeling circuit for measuring the voltages in different directions generated at both ends of the DC circuit breaker under different operating conditions.

[0061] The energy dissipation module consists of resistors R1 and R2 connected in series. After being connected in series, they are connected in parallel with the freewheeling module, and then connected in series with the high-voltage pulse absorption module. Resistors R1 and R2 serve as energy dissipation resistors for capacitors C1 and C2, respectively, providing them with an energy dissipation circuit.

[0062] The bidirectional high-voltage pulse absorption module consists of capacitor C1 and capacitor C2, which respectively absorb voltage surges from different directions experienced by the two ends of the DC circuit breaker.

[0063] The first-stage surge protection module consists of a varistor RV1, a varistor RV2, and a gas discharge tube. The varistor RV1 and varistor RV2 are connected in series. One end of the gas discharge tube is connected to the equipotential connection point between the varistor RV1 and varistor RV2, and the other end is directly grounded, thereby providing a channel for energy discharge to ground for high-voltage surges.

[0064] The second-level surge protection module consists of safety capacitor C3 and safety capacitor C4 connected in series, wherein the equipotential bonding point of C3 and C4 is directly grounded;

[0065] The third-level surge protection module is composed of transient voltage suppression diodes (TVS), which are connected in parallel across the second-level surge protection module.

[0066] The voltage isolation sampling module consists of a front-end sampling resistor R5, a linear optocoupler, and a rear-end sampling resistor R6. R5 is connected to the front end of the linear optocoupler, and R6 is connected to the rear end of the linear optocoupler. The photoelectric conversion characteristics of the linear optocoupler enable isolated transmission of the front-end voltage analog signal. Between the bidirectional high-voltage pulse absorption module and the varistor, current-limiting resistors R3 and R4 are also included to ensure that the loop current remains within acceptable limits. Between the first-stage surge protection module and the second-stage surge protection module, diodes D3 and D4 are included to limit the current flow in the circuit, ensuring the normal operation of the measuring device by controlling the current flow.

[0067] In one embodiment, in the device for measuring the voltage across the DC circuit breaker terminals, the operating voltage thresholds of the varistor RV1 and varistor RV2 in the first-stage surge protection module should be consistent and slightly higher than the operating voltage threshold of the gas discharge tube; the safety capacitors C3 and C4 in the second-stage surge protection module should have the same specifications; and the operating voltage threshold of the transient voltage suppression diode in the third-stage surge protection module should be selected below the withstand limit of the downstream circuit.

[0068] In one embodiment, the measurement method of the voltage measuring device across the DC circuit breaker terminals is as follows: Figures 2(a) to 2(b) As shown, it includes the following steps:

[0069] S1: Connect the measuring device to both ends of the moving and stationary contacts of the DC circuit breaker, assuming that the voltage across the circuit breaker is Uab at this time;

[0070] S2: When the DC circuit breaker is closed, the resistance between the moving and stationary contacts is only in the micro-ohm range, and its on-state voltage drop and power loss can be ignored, i.e., Uab = 0;

[0071] S3: When the DC circuit breaker trips;

[0072] If the DC circuit breaker interrupts a forward current, then Uab > 0. In this case, the two ends of the DC circuit breaker will begin to arc, and the voltage Uab is the arc voltage. Diode D1 is cut off under reverse voltage, and diode D2 is turned on under forward voltage. Since the arc voltage is less than the operating voltage of each surge protection module, the voltage Uab signal passes through capacitor C1, current-limiting resistor R3, and diode D3 to reach the front-stage sampling resistor R5. The linear optocoupler in the voltage isolation sampling module transmits the voltage signal on the front-stage sampling resistor R5 to the rear-stage sampling resistor R6 through photoelectric conversion. There is a fixed transmission ratio between the voltage values ​​of the front and rear sampling resistors. The value of the transmission ratio depends on the specifications of the linear optocoupler itself. By measuring the voltage value of the rear-stage sampling resistor R6, the arc voltage across the DC circuit breaker can be measured.

[0073] When the DC circuit breaker successfully extinguishes the arc, the voltage across the break point is equal to the system voltage, which is often quite high, much higher than the operating voltage of each surge protection module. Devices such as varistors, gas discharge tubes, and transient voltage suppressors will act quickly, limiting the voltage step by step, and finally clamping the voltage of the back-end sampling resistor R6 within the acceptable range, protecting the linear optocoupler and the back-end circuit from damage by high voltage.

[0074] When the system voltage drops, capacitor C1 releases the stored energy through the energy discharge circuit formed by the energy discharge resistor R1, the varistor RV1, and the current limiting resistor R3, in preparation for the next measurement.

[0075] If the DC circuit breaker interrupts the reverse current, then Uab < 0. Similarly, the two ends of the DC circuit breaker will start from the arcing state. Diode D1 will be forward-biased and conduct, while diode D2 will be reverse-biased and cut off. The voltage Uab signal will pass through capacitor C2, current-limiting resistor R4, and diode D4 to reach the front-end sampling resistor R5.

[0076] Similarly, when the DC circuit breaker extinguishes the arc, devices such as the varistor, gas discharge tube, and transient voltage suppressor will act quickly, limiting the voltage step by step, and finally clamping the voltage of the downstream sampling resistor R6 within the acceptable range, protecting the linear optocoupler and downstream circuit from damage by high voltage.

[0077] When the system voltage drops, capacitor C2 releases the stored energy through the energy discharge circuit formed by the energy discharge resistor R2, the varistor RV2, and the current limiting resistor R4, in preparation for the next measurement.

[0078] This invention, through a rationally designed circuit, acquires the arc voltage signal across the moving and stationary contacts of a DC circuit breaker during the opening process via sampling resistor R5 in the pre-stage of a linear optocoupler. The signal is then converted from electrical voltage to electrical voltage through the linear optocoupler, transmitting the analog voltage across sampling resistor R5 to sampling resistor R6 in the subsequent stage. This achieves the measurement objective while ensuring electrical isolation between the pre- and post-stage measurement circuits, reducing interference. A high-voltage pulse absorption module, in conjunction with first-stage, second-stage, and third-stage surge protection modules, collectively suppresses the damage to the measuring device caused by the system voltage across the moving and stationary contacts after the DC circuit breaker opens, protecting the entire measuring device and the safety of the operators.

[0079] To more effectively demonstrate the advantages of this invention, the above-mentioned measuring device was tested, and the results are attached. Figures 3 to 5 As shown. From Figure 3 and Figure 4 It can be seen that, regardless of whether it is under arcing or arcing conditions, the output voltage of the measuring device in this invention is basically consistent with the actual arc voltage at the moving and stationary contacts of the DC circuit breaker, and the response tracking effect is good, with the error controlled within a reasonable range. From Figure 5 It can be seen that when simulating the impact of system voltage, the output voltage of the measuring device in this invention is within a reasonable range, indicating that the measuring circuit is working normally and has not been broken down. The measuring device in this invention can indeed withstand the impact of higher-level system voltage.

[0080] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A device for measuring the voltage across the terminals of a DC circuit breaker, characterized in that, It includes a freewheeling module, a power dissipation module, a bidirectional high-voltage pulse absorption module, a multi-stage surge protection module, and a voltage isolation sampling module, among which, The freewheeling module includes diodes D1 and D2 connected in reverse series to measure the voltage in different directions generated at both ends of the DC circuit breaker under different operating conditions. The energy dissipation module includes resistors R1 and R2 connected in series; The bidirectional high-voltage pulse absorption module includes capacitors C1 and C2, which absorb voltage surges from different directions at both ends of the DC circuit breaker. The energy dissipation module and the freewheeling module are connected in parallel and then connected in series with the bidirectional high-voltage pulse absorption module. Resistors R1 and R2 serve as energy dissipation resistors for capacitors C1 and C2, respectively. The multi-level surge protection module includes, The first-level surge protection module includes a varistor RV1, a varistor RV2 and a gas discharge tube. The varistor RV1 and varistor RV2 are connected in series. One end of the gas discharge tube is connected to the equipotential connection point of the varistor RV1 and varistor RV2, and the other end is grounded. The second-level surge protection module includes safety capacitors C3 and C4 connected in series, wherein the equipotential bonding point of safety capacitors C3 and C4 is grounded. The third-level surge protection module includes a transient voltage suppression diode (TVS) connected in parallel across the second-level surge protection module. The voltage isolation sampling module includes a front-stage sampling resistor R5, a linear optocoupler, and a rear-stage sampling resistor R6. The front-stage sampling resistor R5 is connected to the front stage of the linear optocoupler, and the rear-stage sampling resistor R6 is connected to the rear stage of the linear optocoupler. A current-limiting resistor R3 and a current-limiting resistor R4 are respectively provided between the bidirectional high-voltage pulse absorption module and the varistor RV1 and varistor RV2. The resistor R1, capacitor C1, current-limiting resistor R3, varistor RV1, varistor RV2, current-limiting resistor R4, capacitor C2, and resistor R2 are connected in series to form a loop. The arc voltage signal at both ends of the moving and stationary contacts of the DC circuit breaker during the opening process is collected through the front-stage sampling resistor R5 in the front stage of the linear optocoupler, and photoelectric conversion is realized through the linear optocoupler to transmit the analog voltage on the front-stage sampling resistor R5 to the rear-stage sampling resistor R6. The first-level surge protection module and the second-level surge protection module also include diodes D3 and D4 to limit the current flow in the circuit.

2. The device for measuring the voltage across the terminals of a DC circuit breaker according to claim 1, characterized in that, The diode D3 is connected between the current-limiting resistor R3 and the varistor RV1, and the diode D4 is connected between the current-limiting resistor R4 and the varistor RV2.

3. The device for measuring the voltage across the terminals of a DC circuit breaker according to claim 1, characterized in that, The values ​​of the current-limiting resistors R3 and R4 are equal and do not exceed the kiloohm level.

4. The device for measuring the voltage across the terminals of a DC circuit breaker according to claim 1, characterized in that, The values ​​of resistors R1 and R2 are not less than megaohms; the values ​​of capacitors C1 and C2 are equal and not less than microfarads.

5. The device for measuring the voltage across the terminals of a DC circuit breaker according to claim 1, characterized in that, The operating voltage thresholds of the varistor RV1 and varistor RV2 are consistent and higher than the operating voltage threshold of the gas discharge tube.

6. The device for measuring the voltage across the terminals of a DC circuit breaker according to claim 1, characterized in that, The safety capacitor C3 is the same as the safety capacitor C4.

7. The measurement method of the apparatus for measuring the voltage across the terminals of a DC circuit breaker according to any one of claims 1-6, characterized in that, It includes the following steps, S1: Connect the device for measuring the voltage across the DC circuit breaker contacts to the moving and stationary contacts of the DC circuit breaker. At this time, the voltage across the contacts is Uab. S2: When the DC circuit breaker is closed, the voltage at the break point Uab = 0; S3: When the DC circuit breaker trips; If the DC circuit breaker interrupts a forward current, the break voltage Uab > 0. At this time, the two ends of the DC circuit breaker break start from the arcing state, and the break voltage Uab is the arc voltage. Diode D1 is cut off under reverse voltage, and diode D2 is turned on under forward voltage. Since the arc voltage is less than the operating voltage of each stage of surge protection module, the break voltage Uab signal passes through capacitor C1, current limiting resistor R3, and diode D3 to reach the front-stage sampling resistor R5. The linear optocoupler transmits the voltage signal on the front-stage sampling resistor R5 to the rear-stage sampling resistor R6 through photoelectric conversion. There is a fixed transmission ratio between the voltage values ​​of the front and rear-stage sampling resistors. By measuring the voltage value of the rear-stage sampling resistor R6, the arc voltage at both ends of the DC circuit breaker moving and stationary contacts can be measured. When the DC circuit breaker extinguishes the arc, the voltage across the break point is equal to the system voltage, which is greater than the operating voltage of each surge protection module. The varistor, gas discharge tube, and transient voltage suppression diode (TVS) limit the voltage step by step, ultimately clamping the voltage of the back-end sampling resistor R6 within the acceptable range, protecting the linear optocoupler and the back-end measurement circuit from damage by the system voltage. When the system voltage drops, capacitor C1 releases the stored energy through the energy discharge circuit formed by energy discharge resistor R1, varistor RV1, and current limiting resistor R3, in preparation for the next measurement. If the DC circuit breaker interrupts the reverse current, the break voltage Uab < 0. The two ends of the DC circuit breaker break start from the arcing state. Diode D1 is forward-biased and conducts, while diode D2 is reverse-biased and cut off. The break voltage Uab signal passes through capacitor C2, current-limiting resistor R4, and diode D4 to reach the front-end sampling resistor R5. After the DC circuit breaker extinguishes the arc, the varistor, gas discharge tube, and transient voltage suppressor diode (TVS) activate to limit the voltage step by step, ultimately clamping the voltage of the downstream sampling resistor R6 within the acceptable range, thus protecting the linear optocoupler and the downstream measurement circuit from damage by high voltage. When the system voltage drops, capacitor C2 releases the stored energy through the energy discharge circuit formed by the energy discharge resistor R2, the varistor RV2, and the current limiting resistor R4, in preparation for the next measurement.

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