A state monitoring system for converter valve arrester

Abstract

The present invention belongs to the field of state monitoring of lightning arresters, and specifically relates to a state monitoring system for a converter valve lightning arrester. The system comprises a state monitoring subsystem and a device for separately controlling the on / off switching of bypass branches of various valve groups within the lightning arrester. The subsystem comprises an aging monitoring branch connected in parallel with a branch in which various valve groups and fuses are connected in series within the lightning arrester, a first resistor connected in series with 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 having a resistance equal to the first resistor are connected in series within the aging monitoring branch. The resistance of the third resistor is less than or equal to the volt-ampere ratio of the valve group to be monitored corresponding to a set voltage value. The monitoring control unit is configured to trigger a control device to bypass other valve groups when the terminal voltage reaches a set voltage value when the power device is operating in a negative voltage range. If the current value of the valve group to be monitored is greater than the current value of the third resistor, the lightning arrester is determined to be aged. The set voltage value is greater than the voltage value corresponding to the low impedance state of the lightning arrester.

Description

Technical Field

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

[0002] The HCC converter valve, or Hybrid Commutated Converter (HCC), is a new type of DC transmission technology based on integrated gate-commutated thyristor (IGCT) technology. This technology offers significant advantages over traditional line-commutated converter valves (LCC). First, the HCC converter valve maintains the high capacity, low cost, low losses, and high reliability advantages of conventional LCC DC transmission. This improves power transmission efficiency while also controlling construction and operating costs.

[0003] This HCC converter valve module-level topology includes parallel-connected fusible arresters (i.e., arresters with built-in fuses). These arresters protect power device modules, such as IGCT modules, from damage caused by shutdown overvoltage. However, aging of the arresters in these modules can lead to serious problems. For example, since the primary function of an arrester is to protect equipment from lightning overvoltages and system overvoltages, aging degrades the performance of its internal components, reducing its protective performance. Furthermore, aging degrades its dielectric properties, making partial discharge more likely, leading to arcing within the arrester. This accelerates component aging and can also cause more serious electrical failures.

[0004] However, once the fusible arrester ages, the power device module may fail due to the aging of the arrester, thereby losing the protection function for the power device module. Summary of the Invention

[0005] The purpose of the present invention is to provide a state monitoring system for a converter valve arrester, which is used to solve the problem in the prior art that when a fusible arrester ages, a power device module may fail due to the aging of the arrester, thereby losing the protection function of the power device module.

[0006] To achieve the above-mentioned object, the present invention provides a state monitoring system for a converter valve arrester, the system comprising a state monitoring subsystem and a control device for separately controlling the on / off of the bypass branches of each valve group in the arrester;

[0007] The status 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 that of 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 the other valve groups in the lightning arrester of the power device module except the single valve group to be monitored when the terminal voltage value of the power device module reaches the set voltage value during the operation of the power device module of the converter valve in the negative pressure range, 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.

[0008] Beneficial effect: The present invention provides a new state monitoring system for converter valve lightning arresters, which is mainly composed of a state monitoring subsystem and bypass branches of each valve group connected thereto (a control device for controlling its on and off is provided on the bypass branch; when the voltage at the terminal of the power device module reaches a set voltage value, the other valve groups in the lightning arrester except the valve group to be tested are bypassed through the bypass device to avoid affecting the state monitoring of the valve group to be tested); whether the single valve group is aging is monitored through a circuit including the lightning arrester state monitoring subsystem and a single valve group in the lightning arrester. Because the resistive current can reflect the aging of the valve group, the system adopts the following structure and corresponding monitoring method for monitoring: a resistor is provided in the arrester status monitoring subsystem, wherein a third resistor (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) is a resistor connected in parallel with the single valve group to be tested. The branch in which the third resistor is located is the aging monitoring branch, and the second resistor is also connected in series with the branch; the third resistor is used as a control group for the single valve group to be tested (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 value with the resistance value of the single valve group to be monitored). During the operation of the power device in the negative voltage range, when the terminal voltage value of the arrester meets the set voltage value corresponding to the low impedance state of the valve group (that is, creating an environment for the valve group to withstand high voltage, so that it operates in a low resistance state), for the first resistor serving as the control group, the resistive current flowing through the first resistor does not change. If the resistive current flowing through a single valve group to be monitored increases (i.e., the resistive current flowing through the valve group is greater than the resistive current flowing through the first resistor), the valve group is determined to have aged. This current value effectively reflects the aging status of the valve group, and thus the aging status of the arrester (i.e., if the valve group is aged, the arrester is also aged). This allows for timely detection of arrester aging and facilitates timely treatment of the aged arrester, thus preventing the arrester from losing its protective function for the power device module due to aging, resulting in damage to the power device module or other serious consequences.

[0009] Furthermore, the state monitoring subsystem further includes a voltage comparator for respectively obtaining the terminal voltages of the first and second resistors and comparing them;

[0010] 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.

[0011] Furthermore, 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.

[0012] Furthermore, the monitoring and 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 terminal voltage of the power device 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.

[0013] Furthermore, the condition monitoring subsystem further includes a fuse monitoring branch connected in parallel with a branch in the arrester to which the valve group 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 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 included for respectively obtaining and comparing the terminal voltages of the fuse and the fifth resistor;

[0014] The monitoring control unit determines whether the terminal voltage of the fuse in the lightning arrester is greater than the set proportional threshold value in the following manner: 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 lightning arrester is greater than the set proportional threshold value; otherwise, it is determined that the terminal voltage of the fuse in the lightning arrester is not greater than the set proportional threshold value.

[0015] Furthermore, it also includes a power supply module for drawing power from the power device module to supply power to the status monitoring system.

[0016] Furthermore, the set voltage value is smaller than the voltage value corresponding to the breaking current value of the fuse in the arrester in the volt-ampere characteristic curve of the single valve group to be monitored before aging.

[0017] Furthermore, the control device includes a bypass switch.

[0018] Furthermore, it also includes a human-computer interaction module for displaying the determination results of the monitoring control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a volt-ampere characteristic curve of the arrester in the embodiment of the state monitoring system for the converter valve arrester of the present invention;

[0020] Figure 2 This is a comparative example diagram of the volt-ampere characteristic curves of the arrester before and after aging in an embodiment of the state monitoring system for the converter valve arrester of the present invention;

[0021] Figure 3Schematic diagram of the voltage waveform of the IGCT module in a single cycle operation interval in an embodiment of the state monitoring system for converter valve arrester of the present invention;

[0022] Figure 4 This is an example diagram of an application of the converter valve arrester state monitoring system in an embodiment of the present invention applied to an IGCT module;

[0023] Figure 5 This is a connection example diagram of a converter valve arrester state monitoring system for monitoring the arrester's aging state in an embodiment of the converter valve arrester state monitoring system of the present invention;

[0024] Figure 6 This is a flow chart of the converter valve arrester state monitoring system in an embodiment of the converter valve arrester state monitoring system of the present invention for monitoring the arrester aging state;

[0025] Figure 7 This is a connection diagram illustrating an embodiment of a state monitoring system for a converter valve arrester according to the present invention, in which the state monitoring system for a converter valve arrester performs fault state monitoring on the arrester;

[0026] Figure 8 This is a flow chart of the converter valve arrester state monitoring system in the converter valve arrester state monitoring embodiment of the present invention for monitoring the arrester fault state. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Embodiment of a state monitoring system for converter valve arrester

[0029] This embodiment provides a technical solution for a condition monitoring system for a converter valve arrester. The system comprises a condition monitoring subsystem and bypass branches that control each valve group within the arrester (each bypass branch is equipped with a control device for controlling its on / off state). When monitoring of a single valve group is required, the control device is triggered to bypass all other valve groups except that group to avoid affecting the monitoring of that valve group. The condition monitoring subsystem monitors the aging of the valve group to be monitored. The total current of the arrester consists of two components: resistive current and capacitive current, and the aging status is primarily reflected by the resistive current. Therefore, by obtaining the resistive current value corresponding to the valve group to be monitored within the arrester and comparing it with the current value corresponding to a reference resistor (the reference resistor is connected in parallel with the valve group to be monitored, and the branch containing the reference resistor and the branch containing the valve group to be monitored are both equipped with two resistors of equal resistance), the aging of the valve group can be determined. Because the aging monitoring process occurs within the negative pressure range, the voltage decreases as it approaches zero. Since the resistance of the valve group is increasing, referring to Ohm's law, under normal circumstances, 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 the valve group is greater than the current corresponding to the reference resistor, it is determined that the valve group is aged.

[0030] Specifically, taking the IGCT module (i.e., integrated gate-commutated thyristor module, a type of power device module) protected by a fusible MOV (i.e., a lightning arrester formed by a valve group consisting of MOV valve plates connected in series, in addition to MOVs, the lightning arrester can also be connected in series with SiC or other types of valve plates) as an example, the IGCT module contains a fusible MOV connected in parallel at both ends of the IGCT, and its volt-ampere characteristics are as follows: Figure 1 As shown, the area contained in the curve can be divided into four sub-areas according to the impedance state of the arrester presented by the terminal voltage value of the arrester. The division is as follows:

[0031] 1) When the terminal voltage is less than V1, that is, in sub-areas 1 and 2, the arrester is in a high impedance state, and the current is small at this time;

[0032] 2) When the terminal voltage is greater than or equal to V1, that is, in sub-areas 3 and 4, the arrester is in a low impedance state and discharges a large current.

[0033] In summary, V1 is 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. If it is greater than V1, the lightning arrester will be in a low impedance state and discharge a large current.

[0034] Specifically, in this embodiment, the fusible MOV (i.e., lightning arrester) can be divided into two parts: one is the fuse, and the other is a certain number of valve groups. The fuse, unlike the other parts, is not subject to pressure during operation. Taking the branch circuit consisting of valve group 1, valve group 2, and the fuse as an example, by modulating the ratio of valve group 1 and valve group 2, the parameter values ​​of valve group 2 can be set while the overall parameters of the fusible MOV remain unchanged. This allows the voltage V across valve group 2 to be adjusted to ensure that it remains greater than V1 while the other valve groups are bypassed (even if the total voltage originally divided by valve groups 1 and 2 is applied across valve group 2, causing valve group 2 to exhibit a low impedance due to the short-term high voltage). If aging monitoring is also required for the other valve groups, the parameter values ​​can be set similarly to valve group 2. In other embodiments, the number of valve groups can be divided according to actual needs.

[0035] The comparison of the volt-ampere characteristics of the arrester before and after aging is as follows: Figure 2 As shown. After aging, when the arrester is at the same voltage as before aging, the corresponding current is greater, equivalent to a decrease in resistance. Since arrester degradation is primarily manifested by an increase in resistive current, while the increase in total current is smaller (i.e., small changes in total current make it difficult to monitor), the arrester's aging status is primarily reflected through resistive current. The arrester's total current consists of resistive and capacitive currents. When the arrester operates within sub-regions 1 and 2, the capacitive current accounts for a large proportion of the total current (approximately 80%), while the resistive current accounts for a small proportion (specifically, changes in the microampere range), making it difficult to monitor the resistive current (i.e., if the total current is monitored at this time, the changes in the total current are primarily due to changes in the capacitive current). When the arrester's operating voltage increases, causing the arrester to operate within sub-regions 3 and 4, the capacitive current and voltage increase proportionally, but the resistive current increases at a much higher rate, exponentially increasing with the voltage. Therefore, changes in the total current within sub-regions 3 and 4 can represent changes in the resistive current. This solution monitors the full current status of the arrester within sub-area 3 or sub-area 4 and uses this status as the basis for the arrester aging status.

[0036] When the converter valve is unlocked, the voltage waveform of the IGCT module is as follows: Figure 3 To shorten the time the arrester's valve group operates in sub-areas 3 and 4 and reduce the current flowing through the circuit when the bypass is disconnected, the arrester's aging status is monitored within the negative voltage range. The minimum negative voltage of the IGCT is V2. Therefore, for the arrester's valve group, the parameter requirement for setting V1 is: V1 < |V2|.

[0037] like Figure 4 As shown, the system specifically includes a state monitoring subsystem and a control device for separately controlling the on / off of the bypass branches of each valve group in the arrester.

[0038] like Figure 5 As shown, the state monitoring subsystem includes an aging monitoring branch for being connected in parallel with a branch in which each valve group and fuse are connected in series in the arrester, a first resistor for being 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) having a resistance equal to that of the first resistor (i.e., resistor R1) are connected in series in the aging monitoring branch; the resistance of the third resistor is greater than a set voltage value (the set voltage value is called V3, which is less than a voltage value corresponding to the melting current value of the fuse in the arrester in the volt-ampere characteristic curve of the single valve group to be monitored before aging) corresponding to the volt-ampere ratio (in this embodiment, R3=V3 / I2+K, K≤0; where I2 is the volt-ampere characteristic of the valve group 2) of the volt-ampere characteristic curve of the single valve group to be monitored before aging. The current value corresponding to the set voltage value V3 in the volt-ampere characteristic curve, V3 / I2 is 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 V3; K is the selected aging parameter, through which it can be concluded that the valve plate presents a trend of decreasing resistance after aging; R3 should be selected as a resistor with a resistance smaller than the volt-ampere ratio of the valve plate); the monitoring and control unit is used to trigger the control device to bypass the other valve groups except the single valve group to be monitored when the value of the IGCT module terminal voltage reaches the set voltage value during the operation of the IGCT in the negative pressure range. 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 above-mentioned set voltage value is greater than the voltage value corresponding to the low impedance state of the lightning arrester.

[0039] like Figure 6As shown in the figure, 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 meets 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 this 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. It is set that V1 < V3 < V4, 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. 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 point 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 of 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 valve group 2 corresponding increases. Thus, the current flowing through valve group 2 gradually becomes smaller compared with the current flowing through R3 in the negative voltage range. Therefore, during the detection process, combined with the characteristic that the resistance decreases after aging compared with before aging (that is, 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 means that valve group 2 shows the characteristic of decreasing resistance, and it can be determined that valve group 2 is aging, and then it can be determined that the arrester is aging.

[0040] 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 between the two ends of the device, that is, the voltage between the two ends of the device) 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 greater than the current value of the third resistor.

[0041] Specifically, the voltage comparator is used to compare the current value flowing through the single valve group to be monitored and the current value flowing through the third resistor R3 as follows: the terminal voltage values ​​of R1 and R2 are compared 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 the current value of the single valve group to be monitored is greater than the current value of the third resistor; in other states, the output is '0', indicating that the current value of the single valve group to be monitored is greater than the current value of the third resistor.

[0042] According to Ohm's law, if VR1 ≥ VR2, then IR1 ≥ IR2, indicating that the current value of the single valve group being monitored is greater than the current value of R3. Otherwise, the current value of the single valve group being monitored is determined to be less than the current value of R3. This signal is sent to the IGCT control unit through the condition monitoring subsystem, providing feedback on the aging status of the fusible MOV (i.e., lightning arrester).

[0043] like 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 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 crosses 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.

[0044] The condition monitoring subsystem further includes a fuse monitoring branch connected in parallel with a branch in the arrester to which the valve group and the fuse are connected in series; 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 a set proportional threshold; and a voltage comparator for respectively obtaining and comparing the terminal voltages of the fuse and the fifth resistor.

[0045] The monitoring and control unit determines whether the terminal voltage of the fuse in the lightning arrester is greater than the set proportional threshold value in the following manner: 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 lightning arrester is greater than the set proportional threshold value; otherwise, it is determined that the terminal voltage of the fuse in the lightning arrester is not greater than the set proportional threshold value.

[0046] Specifically, when the converter valve voltage meets the arrester fault state detection condition, the valve control system sends a lightning arrester fault state monitoring signal to all modules in the converter valve. When the module-level IGCT control unit (which belongs to the existing component that controls the IGCT and can also be referred to as the IGCT control unit or module-level control unit) monitors the lightning arrester fault state monitoring signal, it turns on the state monitoring system to implement the lightning arrester fault state detection function. The IGCT control unit monitors the IGCT terminal voltage, and 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 lightning arrester fault state and sends the corresponding state signal to the IGCT control unit. When the lightning arrester is in a fault state, the IGCT control unit disables the active current shutdown function. When the module-level IGCT control unit controls the IGCT to conduct, it sends a fault detection end signal to the state monitoring subsystem to end the lightning arrester fault monitoring of this cycle. When the converter valve voltage meets the arrester fault monitoring condition, all modules perform fault detection in each cycle and feed back the state signal to the valve control system.

[0047] The arrester fault status detection process is as follows Figure 8 According to the working principle of the fusible MOV, its fuse plays the role of protecting the lightning arrester. When an overcurrent fault occurs, the fuse will melt first. Therefore, the fuse status is regarded as the lightning arrester fault status.

[0048] When the fuse is operating normally, its terminals are essentially unaffected by voltage. Therefore, monitoring the fuse terminal voltage provides feedback on the arrester's status. By selecting the parameters for R4 and R5, a pressure-bearing ratio is calibrated (the calibrated pressure-bearing ratio is equivalent to the set proportional threshold corresponding to the ratio of the terminal voltage of the arrester fuse to the total voltage of the arrester branch circuit connected in series with the valve group and fuse).

[0049] In this embodiment, when the voltage across the fuse terminals is greater than the voltage across R5, voltage comparator 2 outputs a '1', indicating that the arrester's fuse terminal voltage is greater than the set proportional threshold. Otherwise, the output is a '0', indicating that the arrester's fuse terminal voltage is not greater than the set proportional threshold. The condition monitoring subsystem sends this signal to the IGCT control unit, providing feedback on the fusible MOV fault status.

[0050] In this embodiment, the system further includes a power supply module for drawing power from the IGCT module to supply power to the state monitoring subsystem. Figure 4 As shown, the condition monitoring subsystem includes a built-in power supply module that connects the module to the power supply circuit formed by the resistor-capacitor loop via connections ① and ④ in the figure to achieve high-voltage power supply. In other embodiments, the condition monitoring subsystem can also be powered by a built-in button battery, renewable energy generation, or an external power supply, eliminating the need to draw power from the IGCT module through the power supply module.

[0051] In addition, the status monitoring system of the converter valve lightning arrester in this embodiment also includes a human-computer interaction module, which is used to display the judgment results of the monitoring control unit. For example, when the monitoring control unit determines that the lightning arrester is aged, the judgment result of the lightning arrester aging is displayed to achieve a timely prompt effect; similarly, when the monitoring control unit determines that the lightning arrester is faulty, the judgment result of the lightning arrester is faulty is displayed. The specific display method can be achieved through human-computer interface output, sending alarm signals, etc., which will not be repeated here.

[0052] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention.

Claims

1. A state monitoring system for a converter valve arrester, characterized in that: It includes a status monitoring subsystem and a control device for controlling the on and off of the bypass branches of each valve group in the arrester; The status 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 that of 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 the other valve groups in the lightning arrester of the power device module except the single valve group to be monitored when the terminal voltage value of the power device module reaches the set voltage value during the operation of the power device module of the converter valve in the negative pressure range, 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 further includes a voltage comparator for respectively obtaining the terminal voltages of the first and second resistors 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 and 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 crosses 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 condition monitoring subsystem further includes a fuse monitoring branch connected in parallel with a branch in the arrester to which the valve group 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 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 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 lightning arrester is greater than the set proportional threshold value in a manner 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 determining that the terminal voltage of the fuse in the lightning 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 condition 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 condition 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.

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