Converter valve lightning arrester state monitoring system

Abstract

The invention belongs to the field of state monitoring of lightning arresters, and particularly relates to a state monitoring system of a converter valve lightning arrester. Comprising a state monitoring subsystem and a device used for respectively controlling on-off of bypass branches of valve groups in the lightning arrester. The aging monitoring branch circuit is used for being connected in parallel with a branch circuit, in which valve banks and fuses are connected in series, in the lightning arrester; the first resistor is used for being connected in series with the branch circuit in which the valve banks and the fuses are connected in series; a third resistor and a second resistor of which the resistance is equal to that of the first resistor are connected in series in the aging monitoring branch; the resistance value of the third resistor is smaller than or equal to the volt-ampere ratio of the to-be-monitored valve group corresponding to the set voltage value; the monitoring control unit is used for triggering the control device to bypass other valve groups when the value of the terminal voltage reaches a set voltage value when the power device operates in a negative voltage interval, and judging that the lightning arrester is aged if the current value of the valve group to be monitored is greater than the current value of the third resistor; the set voltage value is greater than a voltage value corresponding to a low-impedance state of the lightning arrester.

Description

Technical Field

[0001] The present invention belongs to the field of condition monitoring of lightning arresters, and particularly relates to a condition monitoring system for a converter valve lightning arrester. Background Art

[0002] The HCC converter valve, namely the Hybrid Commutated Converter, is a new type of DC transmission technology based on the Integrated Gate Commutated Thyristor (IGCT) technology. This technology has obvious advantages compared with the traditional Line Commutated Converter (LCC). First of all, the HCC converter valve can maintain the advantages of large capacity, low cost, low loss and high reliability similar to those of the LCC conventional DC, which means that while improving the power transmission efficiency, it can also control the construction and operation costs.

[0003] In the module-level topology of this HCC converter valve, there are parallel fusing lightning arresters (i.e., lightning arresters containing fuses inside), and through this fusing lightning arrester, power device modules such as IGCT modules can be protected from being damaged due to withstanding turn-off overvoltage. However, if the lightning arrester of the power device module ages, a series of serious problems may occur. For example: Since the main function of the lightning arrester is to protect equipment from lightning overvoltage and system overvoltage impacts. When the lightning arrester ages, the performance of its internal components will decline, resulting in a reduction in protection performance; and after the lightning arrester ages, its dielectric performance will decline, and partial discharge is likely to occur, which will further lead to internal arc discharge of the lightning arrester, not only accelerating the aging of components, but also possibly causing more serious electrical faults.

[0004] However, once the fusing lightning arrester ages, the power device module may lose its protection function due to the aging failure of the lightning arrester. Summary of the Invention

[0005] The purpose of the present invention is to provide a condition monitoring system for a converter valve lightning arrester to solve the problem in the prior art that when the fusing lightning arrester ages, the power device module may lose its protection function due to the aging failure of the lightning arrester.

[0006] To achieve the above purpose, the present invention provides a condition monitoring system for a converter valve lightning arrester, which system includes a condition monitoring subsystem and a control device for respectively controlling the on-off of bypass branches of each valve group in the lightning arrester; The status monitoring subsystem includes an aging monitoring branch connected in parallel with the branch in which each valve group and fuse are connected in series in the arrester, a first resistor connected in series in the branch in which each valve group and fuse are connected in series, and a monitoring control unit; a third resistor and a second resistor with the same resistance value as the first resistor are connected in series in the aging monitoring branch; the resistance value of the third resistor is less than or equal to the volt-ampere ratio of the volt-ampere characteristic curve before aging of a single valve group to be monitored corresponding to the set voltage value; the monitoring control unit is configured to, during the process that the power device module of the converter valve operates in the negative voltage range, when the value of the terminal voltage of the power device module reaches the set voltage value, trigger the control device to bypass other valve groups in the arrester of the power device module except the single valve group to be monitored, and then if the current value of the single valve group to be monitored is greater than the current value of the third resistor, determine that the arrester is aging; the set voltage value is greater than the voltage value corresponding to the low impedance state of the arrester.

[0007] Beneficial effects: The present invention provides a brand-new state monitoring system for a converter valve arrester. The system mainly consists of a state monitoring subsystem and bypass branches of each valve group connected thereto (a control device for controlling its on-off is provided on the bypass branch; when the value of the terminal voltage of the power device module reaches the set voltage value, other valve groups in the arrester except the valve group to be measured are bypassed through this bypass device to avoid affecting the state monitoring of the valve group to be measured). The aging of a single valve group in the arrester is monitored through a loop including the arrester state monitoring subsystem and the single valve group in the arrester. Since the resistive current can reflect the aging condition of the valve group, the system adopts the following structure and its corresponding monitoring method for monitoring: A resistor is provided in the arrester state monitoring subsystem, and the third resistor (the resistance value of the third resistor is less than or equal to the volt-ampere ratio of the volt-ampere characteristic curve before aging of the single valve group to be monitored corresponding to the set voltage value) is a resistor connected in parallel with the single valve group to be measured, and the branch where it is located is the aging monitoring branch, and a second resistor is also connected in series on this branch; the third resistor is used as a control group for the single valve group to be measured (that is, the current value corresponding to the third resistor remains unchanged, while the current value corresponding to the single valve group to be monitored will change with the aging of the valve group, so the third resistor is actually used to compare the current values with the resistance value of the single valve group to be monitored). During the process when the power device operates in the negative voltage range, when the terminal voltage value of the arrester meets the set voltage value corresponding to the valve group presenting a low impedance state (creating an environment for the valve group to withstand high voltage and making it work in a low resistance state), for the first resistor as the control group, the resistive current flowing through the first resistor does not change. If the resistive current flowing through the single valve group to be monitored relatively increases (that is, the resistive current flowing through the valve group is greater than the resistive current flowing through the first resistor), it is determined that the valve group has aged. Its current value can effectively reflect the aging state of the valve group, and further reflect the aging state of the arrester (that is, if it is determined that the valve group has aged, it can be determined that the arrester has aged). Thus, the aging of the arrester can be detected in a timely manner, facilitating the timely handling operation of the aging arrester, thereby avoiding the loss of the protection function of the power device module due to the aging of the arrester and causing damage to the power device module or other serious consequences.

[0008] Furthermore, the state monitoring subsystem further includes a voltage comparator for respectively acquiring the terminal voltages of the first and second resistors and comparing them; The manner in which the monitoring and control unit determines whether the current value of the single valve group to be monitored is greater than the current value of the third resistor includes: If the comparison result output by the voltage comparator is that the terminal voltage of the first resistor is greater than the terminal voltage of the second resistor, it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor; otherwise, it is determined that the current value of the single valve group to be monitored is not greater than the current value of the third resistor.

[0009] Further, the resistance values of the second resistor and the first resistor are less than that of the third resistor, and the difference between the third resistor and the first and second resistors is greater than a set difference value.

[0010] Further, the monitoring and control unit is further configured to determine, when the forward voltage of the power device terminal passes through zero, whether the voltage across the fuse in the arrester accounts for a proportion greater than a set proportion threshold of the total voltage of the branch in the arrester where the valve bank and the fuse are connected in series. If it is greater, it is determined that the arrester fails; otherwise, it is determined that the arrester does not fail.

[0011] Further, the state monitoring subsystem further includes a fuse monitoring branch connected in parallel with the branch in the arrester where the valve bank and the fuse are connected in series; a fourth resistor and a fifth resistor are connected in series on the fuse monitoring branch; the resistance values of the fifth resistor and the fourth resistor are set such that the ratio of the voltage across the fifth resistor to the total voltage of the fuse monitoring branch is consistent with the set proportion threshold; it further includes a voltage comparator for respectively acquiring the voltages across the fuse and the fifth resistor and comparing them; The method for the monitoring and control unit to determine whether the voltage across the fuse in the arrester is greater than the set proportion threshold includes: if the comparison result output by the voltage comparator is that the voltage value across the fuse is greater than the voltage value across the fifth resistor, it is determined that the voltage across the fuse in the arrester is greater than the set proportion threshold; otherwise, it is determined that the voltage across the fuse in the arrester is not greater than the set proportion threshold.

[0012] Further, it further includes a power extraction module for extracting power from the power device module to supply power to the state monitoring system.

[0013] Further, the set voltage value is less than the voltage value corresponding to the fusing current value of the fuse in the arrester in the volt-ampere characteristic curve before aging of a single valve bank to be monitored.

[0014] Further, the control device includes a bypass switch.

[0015] Further, it further includes a human-machine interaction module for displaying the determination result of the monitoring and control unit. Description of the Drawings

[0016] Figure 1 It is the volt-ampere characteristic curve diagram of the arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention; Figure 2 It is a comparison example diagram of the volt-ampere characteristic curves of the arrester before and after aging in the embodiment of the state monitoring system of the converter valve arrester of the present invention; Figure 3 It is a schematic diagram of the voltage waveform of the IGCT module within a single cycle operation interval in the embodiment of the state monitoring system of the converter valve arrester of the present invention; Figure 4It is an application example diagram of the state monitoring system of the converter valve arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention applied to the IGCT module; Figure 5 It is a connection example diagram of the state monitoring system of the converter valve arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention for aging state monitoring of the arrester; Figure 6 It is a flow chart of the state monitoring system of the converter valve arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention for aging state monitoring of the arrester; Figure 7 It is a connection example diagram of the state monitoring system of the converter valve arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention for fault state monitoring of the arrester; Figure 8 It is a flow chart of the state monitoring system of the converter valve arrester in the embodiment of the state monitoring system of the converter valve arrester of the present invention for fault state monitoring of the arrester. Detailed implementation mode

[0017] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] Embodiment of the state monitoring system of the converter valve arrester This embodiment provides a technical solution of a state monitoring system for a converter valve arrester. The components of the system include a state monitoring subsystem and bypass branches that respectively control each valve group in the arrester (each bypass branch is provided with a control device for controlling its on-off). When it is necessary to monitor a certain single valve group, the control device is triggered to bypass other valve groups except this valve group to avoid affecting the monitoring of this valve group. The state monitoring subsystem is used to perform aging monitoring on the valve group to be monitored; the total current of the arrester consists of two parts: resistive current and capacitive current, and the aging state is mainly reflected by the resistive current. Therefore, by obtaining the value of the resistive current corresponding to the valve group to be monitored in the arrester and comparing it with the value of the current corresponding to the reference resistor (the reference resistor is connected in parallel with the valve group to be monitored, and both the branch where the reference resistor is located and the branch where the valve group to be monitored is located are provided with two resistors with equal resistance values), it can be determined whether this valve group is aging; since the aging monitoring process is in the negative voltage range and the voltage becomes smaller as it approaches zero. Since the resistance of the valve group is increasing, referring to Ohm's law, normally the resistive current corresponding to the valve group should be smaller than the current corresponding to the reference resistor and should not be greater than the current corresponding to the reference resistor; therefore, during the aging monitoring process, if it is detected that the resistive current corresponding to this valve group is greater than the current corresponding to the reference resistor, it is determined that this valve group is aging.

[0019] Specifically, taking the protection of an IGCT module (i.e., an integrated gate-commutated thyristor module, which is a type of power device module) through a fuseable MOV (i.e., a lightning arrester in which the valve bank is composed of MOV varistors connected in series, and other types of varistors such as SiC can also be connected in series in addition to MOV in the lightning arrester) as an example, the fuseable MOV is connected in parallel across the IGCT in the IGCT module, and its voltage-current characteristic is as Figure 1 shown. The area enclosed by this curve can be divided into four sub-regions according to the impedance state presented by the lightning arrester based on the terminal voltage value of the lightning arrester. The division is as follows: 1) When the terminal voltage value is less than V1, that is, when in sub-regions 1 and 2, the lightning arrester presents a high impedance state, and the current is small at this time; 2) When the terminal voltage value is greater than or equal to V1, that is, when in sub-regions 3 and 4, the lightning arrester presents a low impedance state, and a large discharge current is released at this time.

[0020] In summary, V1 is the voltage-current ratio of the voltage-current characteristic curve of a single valve bank to be monitored before aging corresponding to the set voltage value. Meeting the condition of being greater than V1 means that the lightning arrester presents a low impedance state and a large discharge current is released.

[0021] Specifically, in this embodiment, the fuseable MOV (i.e., the lightning arrester) can be divided into two parts. One part is the fuse, and the other part is a certain number of valve banks. The fuse does not bear pressure during operation compared to other parts. Taking the branches of valve bank 1, valve bank 2, and the fuse as an example, by modulating the ratio of valve bank 1 and valve bank 2, the parameter value of valve bank 2 can be set while keeping the overall parameters of the fuseable MOV unchanged, so as to modulate the state where the voltage V on valve bank 2 is greater than V1 when other valve banks are bypassed (that is, the total voltage originally divided by valve bank 1 and valve bank 2 is all applied across valve bank 2, so that valve bank 2 presents a low impedance state due to bearing short-term high voltage); if other valve banks also need to be monitored for aging, the parameter value setting is the same as that of valve bank 2. In other embodiments, the number of valve banks can also be divided according to actual needs.

[0022] The comparison of the voltage-current characteristics of the lightning arrester before and after aging is as Figure 2As shown in the figure. After aging, compared with before aging, when the arrester is at the same voltage, its corresponding current is larger, which is equivalent to a decrease in resistance. Since the deterioration of the arrester is mainly manifested as an increase in resistive current, while the increase in total current is relatively small (that is, the change in total current is small and difficult to monitor), the aging state of the arrester is mainly fed back through the resistive current. The total current of the arrester consists of two parts: resistive current and capacitive current. When the arrester operates within sub-region 1 and sub-region 2, the capacitive current accounts for a relatively large proportion in the total current (that is, about 80%), and the resistive current accounts for a very small proportion (that is, specifically, the change is in the microampere level), and it is difficult to monitor the resistive current (that is, if the total current is monitored at this time, the change in the monitored total current is mainly due to the change in capacitive current); when the operating voltage of the arrester increases and the arrester operates within sub-region 3 and sub-region 4, the capacitive current and voltage increase in proportion, but the increasing speed of the resistive current is very large, which is an exponential level of the increasing speed of the voltage. Therefore, the change in the total current within sub-region 3 and 4 can represent the change in the resistive current. This solution monitors the total current state of the arrester within sub-region 3 or sub-region 4 and uses this state as the basis for the aging state of the arrester.

[0023] During the unlocking and operation of the converter valve, the voltage waveform of the IGCT module is as Figure 3 shown. To shorten the time for the valve group in the arrester to operate within sub-region 3 and sub-region 4 and reduce the current flowing through the circuit when the bypass is disconnected, the monitoring of the aging state of the arrester is selected to be carried out within the negative voltage range. The minimum negative voltage of the IGCT is V2. Therefore, for the valve group in the arrester, the parameter requirement for setting V1 is: V1 < |V2|.

[0024] As Figure 4 shown, the system specifically includes a state monitoring subsystem and a controller for respectively controlling the on / off of the bypass branches of each valve group in the arrester.

[0025] As Figure 5As shown in the figure, the condition monitoring subsystem includes an aging monitoring branch that is connected in parallel with the branch in which each valve group and fuse are connected in series in the arrester, a first resistor that is connected in series in the branch in which each valve group and fuse are connected in series, and a monitoring control unit; a third resistor (i.e., resistor R3) and a second resistor (i.e., resistor R2) with a resistance value equal to that of the first resistor (i.e., resistor R1) are connected in series in the aging monitoring branch; the resistance value of the third resistor is greater than the volt-ampere ratio of the volt-ampere characteristic curve of a single valve group to be monitored before aging corresponding to a set voltage value (this set voltage value is called V3, which is less than the voltage value corresponding to the fuse melting current value in the arrester in the volt-ampere characteristic curve of a single valve group to be monitored before aging); in this embodiment, R3 = V3 / I2 + K, K ≤ 0; where I2 is the current value corresponding to the set voltage value V3 in the volt-ampere characteristic curve of valve group 2, and V3 / I2 is the volt-ampere ratio of the volt-ampere characteristic curve of a single valve group to be monitored before aging corresponding to the set voltage value V3; K is a selected aging parameter, and through this aging parameter, it can be concluded that the resistance of the valve disc becomes smaller after aging; R3 should be selected as a resistor with a resistance value smaller than the volt-ampere ratio of the valve disc; the monitoring control unit is used to trigger the control device to bypass other valve groups except the single valve group to be monitored when the voltage value at the IGCT module terminal reaches the set voltage value during the process that the IGCT operates in the negative voltage range, and then if the current value of the single valve group to be monitored is greater than the current value of the third resistor, it is determined that the arrester is aging; the above set voltage value is greater than the voltage value corresponding to the low impedance state of the arrester.

[0026] As Figure 6As shown, taking valve group 1 and valve group 2 in a certain arrester as an example, when the valve control system receives the information that the converter valve voltage V satisfies the arrester aging state detection condition (i.e., V < V1), the aging state monitoring process is started; the aging state detection of the arrester adopts the method of module polling detection. The valve control system sends the same arrester state detection signal containing module address information to all modules in the converter valve; when the module-level IGCT control unit monitors that the address information in the arrester state monitoring signal corresponds to its own module address, the aging state detection of the arrester is started; the module-level IGCT control unit monitors the IGCT terminal voltage. When the voltage V = V3, the bypass switch closing signal is sent to the state monitoring subsystem, and the bypass switch 6 (i.e., the control device includes the bypass switch, and the bypass switch 6 is the bypass switch used to control the disconnection of the bypass branch of valve group 1) is controlled to close through the monitoring control unit in the subsystem, and valve group 1 is bypassed. Wherein, V1 < V3 < V4 is set, and V4 is the voltage corresponding to the current I1 in the volt-ampere characteristic curve of arrester valve group 2; that is, this set voltage value is less than the voltage value corresponding to the fusing current value of the fuse in the arrester in the volt-ampere characteristic curve of a single valve group before aging to be monitored. Wherein, the current I1 is the fusing current value of the fuse; by monitoring the current flowing through valve group 2, the aging state evaluation of the arrester (i.e., determining whether the arrester is aging) is completed, and the corresponding state signal is sent to the IGCT control unit; when the module-level IGCT control unit monitors the positive zero-crossing of the IGCT terminal voltage, the bypass switch opening signal is sent to the monitoring control unit, and the monitoring control unit controls the bypass switch 6 to open, completing the aging state detection of the arrester for one module. The resistance values of the above-mentioned second resistor and the first resistor are less than that of the third resistor, and the difference between the third resistor and the first and second resistors is greater than the set difference value; that is, the resistance value relationship among R1, R2, and R3 is: R1 = R2 and the resistance value of R3 is much larger than that of R1 and R2. Because the aging monitoring process is in the negative voltage range, the valve group voltage is approaching zero, that is, gradually decreasing to 0, and according to Figure 2 the volt-ampere characteristic curve, it can be seen that when the voltage becomes smaller, the resistance of the corresponding valve group 2 becomes larger. Thus, the current flowing through valve group 2 gradually becomes smaller compared with the current flowing through R3 in the negative voltage range. Therefore, in the detection process, combined with the characteristic that the resistance decreases after aging compared with before aging (i.e., after aging compared with before aging, when the arrester is at the same voltage, its corresponding current is larger), if the current flowing through valve group 2 is greater than the current flowing through R3, it indicates that valve group 2 shows the characteristic of decreasing resistance, and it can be determined that valve group 2 is aging, and further determine that the arrester is aging.

[0027] The state monitoring subsystem also includes a voltage comparator for respectively obtaining the terminal voltages of the first and second resistors (the terminal voltage of a device refers to the potential difference across the two ends of the device, that is, the voltage across the two ends of the device) and comparing them; the monitoring control unit determines whether the current value of a single valve group to be monitored is greater than the current value of the third resistor in the following ways: if the comparison result output by the voltage comparator is that the terminal voltage of the first resistor is greater than the terminal voltage of the second resistor, it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor; otherwise, it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor.

[0028] The specific way to compare the current value flowing through a single valve group to be monitored and the current value flowing through the third resistor R3 through the voltage comparator is as follows: compare the terminal voltage values of R1 and R2 through the voltage comparator. When VR1≥VR2 (VR1 is the terminal voltage value of R1; VR2 is the terminal voltage value of R2), the comparator outputs '1', indicating that it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor; in other states, it outputs '0', indicating that it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor.

[0029] Referring to Ohm's law, if VR1≥VR2, then IR1≥IR2, that is, the current value of the single valve group to be monitored is greater than the current value of R3. Otherwise, it is determined that the current value of the single valve group to be monitored is not greater than the current value of R3. The state monitoring subsystem sends this signal to the IGCT control unit to feedback the aging state of the fuseable MOV (i.e., arrester).

[0030] Such as Figure 7 As shown, the monitoring control unit is also used to determine whether the ratio of the terminal voltage of the fuse in the arrester to the total voltage of the branch in the arrester in series with the valve group and the fuse is greater than the set ratio threshold when the IGCT terminal voltage is positively zero-crossing. If it is greater, it is determined that the arrester has a fault; otherwise, it is determined that the arrester has no fault.

[0031] The state monitoring subsystem also includes a fuse monitoring branch in parallel with the branch in the arrester in series with the valve group and the fuse; a fourth resistor R4 and a fifth resistor R5 are connected in series on the fuse monitoring branch; the resistance values of the fifth resistor and the fourth resistor are set so that the ratio of the terminal voltage of the fifth resistor to the total voltage of the fuse monitoring branch is consistent with the set ratio threshold; it also includes a voltage comparator for respectively obtaining the terminal voltages of the fuse and the fifth resistor and comparing them; The monitoring control unit determines whether the terminal voltage of the fuse in the arrester is greater than the set ratio threshold in the following ways: if the comparison result output by the voltage comparator is that the terminal voltage value of the fuse is greater than the terminal voltage value of the fifth resistor, it is determined that the terminal voltage of the fuse in the arrester is greater than the set ratio threshold; otherwise, it is determined that the terminal voltage of the fuse in the arrester is not greater than the set ratio threshold.

[0032] Specifically, when the converter valve voltage meets the arrester fault state detection condition, the valve control system sends an arrester fault state monitoring signal to all modules in the converter valve. When the module-level IGCT control unit (which belongs to the existing components for controlling IGCT and can also be simply referred to as the IGCT control unit or the module-level control unit) monitors the arrester fault state monitoring signal, it activates the state monitoring system to implement the arrester fault state detection function. The IGCT control unit monitors the IGCT terminal voltage. When the voltage crosses zero in the positive direction, it sends a fault detection start signal to the state monitoring subsystem. The state monitoring subsystem monitors the voltage of the fuse to complete the assessment of the arrester fault state and sends the corresponding state signal to the IGCT control unit. When the arrester is in a fault state, the IGCT control unit shields the active turn-off current function. When the module-level IGCT control unit controls the conduction of the IGCT, it sends a fault detection end signal to the state monitoring subsystem to end the arrester fault monitoring for this cycle. When the converter valve voltage meets the arrester fault monitoring condition, all modules perform fault detection every cycle and feedback the state signal to the valve control system.

[0033] The fault state detection process of the arrester is as Figure 8 shown. According to the working principle of the fusible MOV, its fuse plays a role in protecting the arrester. In the event of an overcurrent fault, the fuse will blow first, so the fuse state is used as the arrester fault state.

[0034] When the fuse is normal, there is basically no voltage across its two ends. Therefore, the state of the arrester can be feedback by monitoring the voltage across the fuse. By selecting the parameters of R4 and R5, a pressure-bearing ratio is calibrated (the calibrated pressure-bearing ratio is the set ratio threshold corresponding to the ratio of the voltage across the fuse in the arrester to the total voltage of the branch in the arrester where the valve group and the fuse are connected in series).

[0035] In this embodiment, when the voltage across the fuse is greater than the voltage of R5, the output of voltage comparator 2 is '1', indicating that it is determined that the voltage across the fuse in the arrester is greater than the set ratio threshold; in other cases, the output is '0', indicating that it is determined that the voltage across the fuse in the arrester is not greater than the set ratio threshold. The state monitoring subsystem sends this signal to the IGCT control unit to feedback the fault state of the fusible MOV.

[0036] In this embodiment, the system further includes a power-taking module for taking power from the IGCT module to supply power to the state monitoring subsystem. Specifically, as Figure 4As shown, the state monitoring subsystem is built-in with a power-taking module. This module is connected to the power-taking loop formed by the resistor-capacitor loop through the wiring ① and ④ to achieve power-taking from high potential. In other embodiments, the state monitoring subsystem can also be powered by means of built-in button batteries, new energy power generation, or external power supplies, etc., without taking power from the IGCT module through the power-taking module.

[0037] In addition, the state monitoring system of the converter valve arrester in this embodiment further includes a human-machine interaction module, which is used to display the determination results of the monitoring and control unit. For example, when the monitoring and control unit determines that the arrester is aging, the determination result of the aging of the arrester is displayed to achieve the effect of timely prompting; the same is true when the monitoring and control unit determines that the arrester fails. The determination result of the failure of the arrester is displayed. The specific display method can be realized by outputting through the human-machine interface, sending alarm signals, etc., and will not be elaborated here.

[0038] It should be understood that the above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention.

Claims

1. A state monitoring system for a converter valve arrester, characterized in that: It includes a state monitoring subsystem and a control device for controlling the on and off of the bypass branches of each valve group in the arrester; The state monitoring subsystem includes an aging monitoring branch connected in parallel with a branch in which various valve groups and fuses are connected in series in the lightning arrester, a first resistor connected in series in the branch in which various valve groups and fuses are connected in series, and a monitoring control unit; a third resistor and a second resistor with a resistance equal to the first resistor are connected in series in the aging monitoring branch; the resistance of the third resistor is less than or equal to the volt-ampere ratio of the volt-ampere characteristic curve of the single valve group to be monitored before aging corresponding to the set voltage value; the monitoring control unit is used to trigger the control device to bypass other valve groups in the lightning arrester of the power device module except the single valve group to be monitored when the power device module of the converter valve is operating in the negative pressure range when the value of the terminal voltage of the power device module reaches the set voltage value, and if the current value of the single valve group to be monitored is greater than the current value of the third resistor, it is determined that the lightning arrester is aged; the set voltage value is greater than the voltage value corresponding to the low impedance state of the lightning arrester.

2. The state monitoring system for converter valve arrester according to claim 1, characterized in that: The state monitoring subsystem also includes a voltage comparator for respectively obtaining the terminal voltages of the first resistor and the second resistor and comparing them; The monitoring control unit determines whether the current value of the single valve group to be monitored is greater than the current value of the third resistor in the following manner: if the comparison result output by the voltage comparator is that the terminal voltage of the first resistor is greater than the terminal voltage of the second resistor, then it is determined that the current value of the single valve group to be monitored is greater than the current value of the third resistor; otherwise, it is determined that the current value of the single valve group to be monitored is not greater than the current value of the third resistor.

3. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: The resistance values ​​of the second resistor and the first resistor are smaller than the third resistor, and the difference between the third resistor and the first and second resistors is greater than a set difference value.

4. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: The monitoring control unit is also used to determine whether the ratio of the terminal voltage of the fuse in the lightning arrester to the total voltage of the branch in which the valve group and the fuse are connected in series in the lightning arrester is greater than a set ratio threshold when the IGCT terminal voltage passes through zero in the positive direction. If so, it is determined that the lightning arrester has a fault; otherwise, it is determined that the lightning arrester has not a fault.

5. The state monitoring system for converter valve arrester according to claim 4, characterized in that: The state monitoring subsystem further comprises a fuse monitoring branch connected in parallel with a branch in which a valve group and a fuse are connected in series in the arrester; a fourth resistor and a fifth resistor are arranged in series on the fuse monitoring branch; the resistance values ​​of the fifth resistor and the fourth resistor are set so that the ratio of the terminal voltage of the fifth resistor to the total voltage of the fuse monitoring branch is consistent with a set proportional threshold; and a voltage comparator is further comprised for respectively obtaining and comparing the terminal voltages of the fuse and the fifth resistor; The monitoring control unit determines whether the terminal voltage of the fuse in the arrester is greater than the set proportional threshold value, including: if the comparison result output by the voltage comparator is that the terminal voltage value of the fuse is greater than the terminal voltage value of the fifth resistor, then it is determined that the terminal voltage of the fuse in the arrester is greater than the set proportional threshold value; Otherwise, it is determined that the terminal voltage of the fuse in the arrester is not greater than the set proportional threshold.

6. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: It also includes a power taking module for taking power from the IGCT module to supply power to the state monitoring system.

7. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: The set voltage value is smaller than the voltage value corresponding to the fusing current value of the fuse in the arrester in the volt-ampere characteristic curve of the single valve group to be monitored before aging.

8. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: The control device includes a bypass switch.

9. The state monitoring system for converter valve arrester according to claim 1 or 2, characterized in that: It also includes a human-computer interaction module for displaying the determination results of the monitoring control unit.

Images