Voltage break variable protection method and device for high-voltage direct-current transmission line

Abstract

The invention discloses a voltage break variable protection method and device for a high-voltage direct-current transmission line, and belongs to the technical field of direct-current transmission, and the method comprises the steps: obtaining a current first target direct-current voltage and a current target direct-current current of a first transmission line; wherein the first power transmission line is a high-voltage direct-current power transmission line in the high-voltage direct-current power transmission system; determining a first voltage variation and a voltage change rate based on the first target DC voltage, and determining a current variation based on the target DC current; when the product of the first voltage variable quantity and the current variable quantity is smaller than a direction criterion fixed value, the absolute value of the voltage change rate is larger than a change rate fixed value, and the duration when the direct-current voltage of the first power transmission line is lower than the voltage fixed value is larger than or equal to a first duration fixed value, the current variable quantity of the first power transmission line is determined; and controlling a direct-current circuit breaker connected with the first power transmission line to be switched off. According to the method, the homo-polar lightning stroke interference resistance of voltage break variable protection can be effectively improved, and voltage break variable protection maloperation and refusal operation are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current transmission, in particular to a voltage sudden change quantity protection method and device for high-voltage direct current transmission lines. BACKGROUND

[0002] High-voltage direct current transmission technology has developed from traditional two-end high-voltage direct current transmission to multi-end high-voltage direct current transmission and direct current power grid. Multi-end high-voltage direct current transmission projects and direct current power grid projects have multiple high-voltage direct current transmission lines. Different fault handling strategies need to be taken for faults of these high-voltage direct current transmission lines, such as reclosing direct current circuit breakers and fast switches to remove fault lines. Therefore, multi-end high-voltage direct current transmission systems have very high requirements for the reliability and selectivity of direct current transmission line protection to avoid external interference causing misoperation and refusal of direct current transmission line protection.

[0003] The related art method for determining a fault line includes: when line protection action is detected within a preset time after a fault, but no pole protection action is detected, and the electrical quantity relationship of the bus area is detected to meet the fault judgment condition, it is judged that the line side corresponding to the condition that the current sudden change quantity and the change quantity are negative values is the fault line side of the bus area. As can be seen, the related art considers that when the direction of the current sudden change quantity of a certain line is from the bus to the line, the line is a fault line. This method will fail when the same polarity lightning strikes, causing protection refusal of the fault line and protection misoperation of the non-fault line. SUMMARY

[0004] Embodiments of the present application provide a voltage sudden change quantity protection method and device for high-voltage direct current transmission lines, aiming to solve the problem of easy misoperation and refusal of voltage sudden change quantity protection relying on current direction alone, and improve the anti-same-polarity lightning interference performance of direct current voltage sudden change quantity protection.

[0005] In a first aspect, a voltage sudden change quantity protection method for a high-voltage direct current transmission line is provided, comprising:

[0006] obtaining a first target direct current voltage and a target direct current at present of a first transmission line; wherein the first transmission line is a high-voltage direct current transmission line in a high-voltage direct current transmission system;

[0007] determining a first voltage change quantity and a voltage change rate based on the first target direct current voltage, and determining a current change quantity based on the target direct current;

[0008] In a case that the product of the first voltage variation and the current variation is less than the direction criterion value, the absolute value of the voltage variation rate is greater than the variation rate value, and the duration that the DC voltage of the first power transmission line is less than the voltage value is greater than or equal to the first duration value, the DC circuit breaker connected to the first power transmission line is controlled to open.

[0009] In some of the design manners, after the DC circuit breaker connected to the first power transmission line is controlled to open, the method further comprises:

[0010] After the second duration value, the DC circuit breaker is controlled to close.

[0011] In some of the design manners, the first voltage variation is determined based on the first target DC voltage, comprising:

[0012] The first historical DC voltage of the first power transmission line is obtained, and the time interval between the collection time of the first historical DC voltage and the current time is greater than or equal to the first duration value;

[0013] The first voltage variation is determined based on the first target DC voltage and the first historical DC voltage.

[0014] In some of the design manners, the determination of the voltage variation rate comprises:

[0015] The second historical DC voltage of the first power transmission line is obtained, and the time interval between the collection time of the second historical DC voltage and the current time is less than the first duration value;

[0016] The voltage variation rate is determined based on the first target DC voltage, the first historical DC voltage, the collection time of the first historical DC voltage and the current time.

[0017] In some of the design manners, the current variation is determined based on the target DC current, comprising:

[0018] The historical DC current of the first power transmission line is obtained, and the time interval between the collection time of the historical DC current and the current time is greater than or equal to the first duration value;

[0019] The current variation is determined based on the target DC current and the historical DC current.

[0020] In some of the design manners, the direction criterion value is less than or equal to the product of the variation of the DC voltage of the HVDC power transmission line and the variation of the DC current of the HVDC power transmission line when the HVDC power transmission system is in normal operation.

[0021] In some of the design manners, the voltage sudden change protection method further comprises:

[0022] Obtain the current second target DC voltage of the second transmission line, which is a high voltage DC transmission line in a high voltage DC transmission system and belongs to a different pole from the first transmission line;

[0023] Based on the first target DC voltage and the second target DC voltage, determine the common-mode voltage and the second voltage change of the common-mode voltage;

[0024] Based on the second voltage change, the fault occurrence status of the first transmission line is determined.

[0025] In some of these designs, the DC voltage of the first transmission line is positive during normal operation, while the DC voltage of the second transmission line is negative during normal operation.

[0026] Based on the second voltage change, the fault occurrence status of the first transmission line is determined, including:

[0027] If the change in the second voltage is less than the set value of the change, then it is determined that the first transmission line has a fault, and the set value of the change is negative.

[0028] In some of these designs, the DC voltage of the first transmission line is negative during normal operation, while the DC voltage of the second transmission line is positive during normal operation.

[0029] Based on the second voltage change, the fault occurrence status of the first transmission line is determined, including:

[0030] If the change in the second voltage is greater than the absolute value of the change setting, then the first transmission line is determined to have a fault, and the change setting is negative.

[0031] Secondly, a voltage surge protection device for high-voltage direct current transmission lines is provided, comprising:

[0032] The acquisition unit is configured to acquire the current first target DC voltage and the current target DC current of the first transmission line; wherein the first transmission line is a high-voltage DC transmission line in a high-voltage DC transmission system;

[0033] The determining unit is configured to determine a first voltage change and a voltage change rate based on a first target DC voltage, and to determine a current change based on a target DC current;

[0034] The control unit is configured to control the DC circuit breaker connected to the first transmission line to open when the product of the first voltage change and the current change is less than the direction criterion setting, the absolute value of the voltage change rate is greater than the change rate setting, and the duration of the DC voltage of the first transmission line being lower than the voltage setting is greater than or equal to the first duration setting.

[0035] Beneficial effects:

[0036] The solution provided in this application can obtain the current first target DC voltage and the current target DC current of a first transmission line, which is a high-voltage direct current (HVDC) transmission line in a high-voltage direct current (HVDC) transmission system. Then, based on the first target DC voltage, a first voltage change and a voltage change rate are determined, and based on the target DC current, a current change is determined. If the product of the first voltage change and the current change is less than a direction criterion setting, the absolute value of the voltage change rate is greater than a change rate setting, and the duration of the DC voltage of the first transmission line being lower than the voltage setting is greater than or equal to a first duration setting, the DC circuit breaker connected to the first transmission line is controlled to open. By comprehensively considering the magnitude of the product of the DC voltage change and the DC current change, faults in the HVDC transmission line can be accurately identified, effectively improving the resistance to same-polarity lightning interference of voltage surge protection, avoiding false tripping and failure to trip of voltage surge protection, and improving the reliability of voltage surge protection. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of a voltage surge protection method for high-voltage direct current transmission lines provided in an embodiment of this application;

[0039] Figure 2 This is a schematic diagram of the DC line protection measuring points and configuration of a two-end high-voltage DC transmission system provided in an embodiment of this application;

[0040] Figure 3 This is a logic diagram of voltage surge protection for high-voltage direct current transmission lines provided in an embodiment of this application;

[0041] Figure 4 This is a schematic diagram of the structure of the voltage surge protection device for high-voltage direct current transmission lines provided in the embodiments of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0045] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0046] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0047] As mentioned earlier, the relevant technology for identifying faulty lines includes the following method: when a line protection operation is detected within a preset time after the fault, but no polarity protection operation is detected, and the electrical quantity relationship in the busbar area meets the fault judgment conditions, then the line side corresponding to the condition that the current surge and change are negative is determined to be the faulty line side in the busbar area. Therefore, this relevant technology considers a line to be faulty when the direction of the current surge is from the busbar to the line. This method fails during lightning strikes of the same polarity, causing protection failure on the faulty line and maloperation of protection on non-faulty lines.

[0048] In addition, other related technologies involve fault direction identification or fault selection methods for DC transmission lines. For example, one related technology involves a fault location method for multi-terminal flexible DC transmission systems. This method calculates the arrival time of the fault traveling wave at different converter stations, then calculates the distance from the fault point to each converter station based on the time, compares this distance with the line length, and finally achieves fault selection. This method relies on the premise that each converter station is based on a fully synchronized clock and has devices supporting high-speed AD (analog-to-digital converter) sampling to capture the fault traveling wave. Furthermore, it requires accurate calculation of the wave velocity for each line. Deviations in any of these aspects can significantly affect the fault selection result.

[0049] Another related technology involves a fault location method for double-circuit DC lines on the same tower. Its core idea is to calculate the variance of the normalized pole voltage 10 ms after the fault occurs. If the variance exceeds a predetermined value, the pole is considered faulty. Therefore, this method identifies the faulty pole by utilizing the magnitude of the fault voltage.

[0050] In another related technology, the rapid recovery characteristics of DC voltage and the polarity of common-mode voltage are used to identify the faulty pole. This solves the problem of false tripping of DC transmission line protection caused by electromagnetic induction on non-faulty poles. However, it does not involve fault direction identification or fault line selection for DC transmission lines of the same pole.

[0051] As described above, existing methods for identifying fault direction or locating faults in DC transmission lines either require high accuracy in the sampling of secondary devices and the calculation of line wave velocity, or simply compare the amplitude of voltage changes between poles and calculate the direction of current. Therefore, these methods suffer from implementation difficulties or poor anti-interference capabilities. Furthermore, technologies related to DC voltage surge protection do not address fault direction identification.

[0052] This application provides a method and apparatus for voltage surge protection of high-voltage direct current transmission lines, aiming to solve the problem that relying solely on the current direction can easily lead to false tripping and failure to trip of voltage surge protection, and to improve the anti-interference performance of DC voltage surge protection against lightning strikes of the same polarity.

[0053] Figure 1 This is a flowchart of a voltage surge protection method for high-voltage direct current transmission lines provided in an embodiment of this application. Figure 1 As shown, the voltage surge protection method includes the following steps:

[0054] S101: Obtain the current first target DC voltage and the current target DC current of the first transmission line; wherein, the first transmission line is a high-voltage DC transmission line in a high-voltage DC transmission system;

[0055] S103: Determine the first voltage change amount and voltage change rate based on the first target DC voltage, and determine the current change amount based on the target DC current;

[0056] S105: When the product of the first voltage change and the current change is less than the direction criterion setting, the absolute value of the voltage change rate is greater than the change rate setting, and the duration of the DC voltage of the first transmission line being lower than the voltage setting is greater than or equal to the first duration setting, the DC circuit breaker connected to the first transmission line is controlled to open.

[0057] Figure 1 The corresponding embodiment provides a solution that, by comprehensively considering the product of the change in DC voltage and the change in DC current, can accurately identify faults in high-voltage DC transmission lines, effectively improve the ability of voltage surge protection to resist lightning interference of the same polarity, avoid false tripping and failure to trip of voltage surge protection, and improve the reliability of voltage surge protection.

[0058] Steps S101 to S105 will be explained below.

[0059] In step S101, the current first target DC voltage and the current target DC current of the first transmission line are obtained; wherein, the first transmission line is a high-voltage direct current (HVDC) transmission line in a high-voltage direct current (HVDC) transmission system. In one example, the HVDC transmission system includes at least two converter stations. Where each converter station in the HVDC transmission system is two converter stations, the HVDC transmission system can be referred to as a two-terminal HVDC transmission system.

[0060] It needs to be explained that, Figure 1 The implementing entity of the solution provided in the corresponding embodiment can be a voltage surge protection device for the first transmission line. This voltage surge protection device can collect the current first target DC voltage and the current target DC current of the first transmission line.

[0061] Figure 2 This is a schematic diagram of the protection measuring points and configuration of a DC line in a high-voltage DC transmission system provided in an embodiment of this application. (See attached diagram.) Figure 2As shown, the two-terminal high-voltage direct current transmission system includes two converter stations, Station 1 and Station 2, as well as a single-phase DC line and a second-phase DC line. Both the single-phase DC line and the second-phase DC line are high-voltage direct current transmission lines.

[0062] exist Figure 2 In the high-voltage direct current transmission system shown at both ends, the DC current I of the polar DC line is defined. DL1 The positive direction is from the rectifier side to the inverter side, and the DC current I in the second-stage DC line is... DL2 The positive direction is from the inverter side to the rectifier side, and the DC voltage U of the DC line is... DL1 Under normal operation, it is a positive voltage; the DC voltage U of the second-pole DC line is... DL2 The voltage is negative during normal operation. Additionally, independent protection devices are configured for voltage surge protection on both the single-pole DC line and the second-pole DC line.

[0063] The voltage surge protection device on the rectifier side electrode one collects the DC voltage U of the rectifier side electrode DC line. DL1 DC current I of the DC circuit DL1 The voltage surge protection device on the rectifier side electrode two collects the DC voltage U of the DC line on the rectifier side electrode two. DL2 DC current I of the two-pole DC circuit DL2 The voltage surge protection device on the inverter side electrode one collects the DC voltage U of the DC line on the inverter side electrode. DL1 DC current I of the DC circuit DL1 The voltage surge protection device on the inverter side electrode two collects the DC voltage U of the DC line on the inverter side electrode two. DL2 DC current I of the two-pole DC circuit DL2 .

[0064] The high-voltage direct current transmission system in step S101 is Figure 2 In the case of the two-terminal high-voltage direct current transmission system shown, the first transmission line can be any one of the following: rectifier-side pole DC line, rectifier-side pole DC line, inverter-side pole DC line, and inverter-side pole DC line.

[0065] In step S103, the first voltage change amount and voltage change rate are determined based on the first target DC voltage, and the current change amount is determined based on the target DC current.

[0066] Specifically, historical DC voltage and historical DC current of the first transmission line can be acquired. Based on the first target DC voltage and the historical DC voltage, the first voltage change and voltage change rate can be determined, and the current change can be determined based on the target DC current and the historical DC current. In one example, the historical DC voltage includes a first historical DC voltage and a second historical DC voltage. The time interval between the acquisition time of the first historical DC voltage and the historical DC current and the current time t is greater than or equal to a first time duration setpoint T. set The time interval between the second historical DC voltage acquisition time and the current time t is less than the first time duration setpoint T. set It should be understood that the acquisition time of the first historical DC voltage is earlier than the acquisition time of the second historical DC voltage. Specifically, the first duration setpoint T... set The value can be set according to actual needs and is not specifically limited here. Furthermore, the first voltage change is determined based on the first target DC voltage and the first historical DC voltage. The voltage change rate is determined based on the first target DC voltage, the second historical DC voltage, the acquisition time of the second historical DC voltage, and the aforementioned current time.

[0067] like Figure 3 As shown, with U DL_n I represents the DC voltage of the first target sample collected at the current time t. DL_n U represents the target DC current collected at the current time t. DL_k U represents the first historical DC voltage of the first transmission line. DL_h I represents the second historical DC voltage of the first transmission line. DL_m The historical DC current of the first transmission line is represented by ΔU. DL The first voltage change, ΔI DL t represents the change in current. h Indicates the second historical DC voltage U DL_h Taking the acquisition time as an example, the first voltage change ΔU DL =U DL_n -U DL_k The rate of voltage change is (U DL_n -U DL_h ) / (tt h ), Current change ΔI DL =I DL_n -I DL_m .in, Figure 3 This is a schematic diagram of the voltage surge protection logic for high-voltage direct current transmission lines provided in the embodiments of this application.

[0068] It should be noted that in the embodiments of this application, the unit of DC voltage and the amount of change of DC voltage can be kV (kilovolt), the unit of DC current and the amount of change of DC current can be A (ampere), and the unit of voltage change rate can be kV / ms.

[0069] In step S105, the DC circuit breaker connected to the first transmission line is opened when all three of the following conditions are met:

[0070] Condition 1: The first voltage change ΔU determined in step S103 DL With the change in current ΔI DL The product is less than the direction criterion value P set ;

[0071] Condition 2: The absolute value of the voltage change rate determined in step S103 is greater than the change rate setpoint V. set ;

[0072] Condition 3: The DC voltage of the first transmission line is lower than the voltage setting U. set The duration is greater than or equal to the first duration setpoint T set .

[0073] like Figure 3 As shown, if ΔU DL *ΔI DL <P set If condition 1 is satisfied, the output logic is true. If the voltage change rate satisfies |(U DL_n -U DL_h ) / (tt h )|>V set If condition 2 is met, the output logic is true. If the DC voltage of the first transmission line is lower than the voltage setting U... set The duration is greater than or equal to the first duration setpoint T set That is, the DC voltage of the first transmission line at T set The innermost part is less than U set If condition 3 is satisfied, the output is true. When conditions 1, 2, and 3 are all satisfied and all output true, the output of the AND gate is true, triggering the voltage surge protection action, that is, controlling the DC circuit breaker connected to the first transmission line to open. Figure 3 The '&' symbol in the diagram represents the AND gate. set V set T set The value can be set according to actual needs, and no specific limitation is made here.

[0074] It should be noted that only when conditions 2 and 3 are met simultaneously can it be concluded that the DC voltage of the first transmission line experienced a drastic change and occurred within the first time duration setpoint T. setThe voltage remains below the set value U for an extended period. set The abnormal situation does not necessarily mean that the first transmission line has failed, as it could also be caused by external interference, such as lightning strikes of the same polarity. To avoid maloperation or failure to operate the voltage surge protection of the high-voltage direct current transmission line due to external interference, the solution provided in this application includes condition 1. Based on condition 1, the product of the change in DC voltage and the change in DC current can be comprehensively considered. Only when conditions 1, 2, and 3 are simultaneously satisfied is it determined that the first transmission line has failed, thereby controlling the DC circuit breaker connected to the first transmission line to open and disconnect the faulty first transmission line.

[0075] In one implementation, the direction criterion setting P set The change in DC voltage is less than or equal to the product of the change in DC current and the change in DC current of the HVDC transmission line during normal operations such as power ramp-up / amplification and power transfer. This implementation ensures that condition 1 does not occur during normal operations such as power ramp-up / amplification and power transfer, thereby improving the ability of voltage surge protection to resist interference generated by the HVDC transmission system during these normal operations, avoiding false tripping of voltage surge protection, and improving the reliability of voltage surge protection.

[0076] In one embodiment, after controlling the DC circuit breaker connected to the first transmission line to open, the method further includes: controlling the DC circuit breaker to close after an interval of a second time setting. The second time setting can be, for example, a value within the range of [100ms, 999ms], such as 100ms, 300ms, or 500ms, and can be set according to actual needs; no specific limitation is made here. By controlling the DC circuit breaker to close after controlling the opening of the DC circuit breaker connected to the first transmission line and then closing it after an interval of the second time setting, the system can attempt to restore normal line operation through delayed closing, thereby improving the continuity of system power supply.

[0077] In practice, other criteria can also be used to identify faults in the first transmission line.

[0078] For example, in some embodiments, when obtaining the current first target DC voltage of the first transmission line, the current second target DC voltage of the second transmission line can also be obtained. The second transmission line is a high-voltage direct current (HVDC) transmission line in a HVDC transmission system and belongs to a different pole than the first transmission line. Then, based on the first and second target DC voltages, the common-mode voltage and the second voltage change of the common-mode voltage are determined. Finally, based on the second voltage change, the fault occurrence status of the first transmission line is determined. For ease of description, this common-mode voltage will be referred to as the first common-mode voltage below. This implementation can accurately distinguish the faulty pole line, avoid maloperation of non-faulty pole protection, and improve the anti-interference capability of voltage surge protection, ensuring the selectivity and reliability of fault handling.

[0079] Furthermore, the third historical DC voltage of the second transmission line can also be obtained. The time interval between the acquisition time of the third historical DC voltage and the current time t is greater than or equal to the first time duration setpoint T. set When determining the second voltage change, the second common-mode voltage can also be determined based on the first historical DC voltage of the first transmission line and the third historical DC voltage of the second transmission line, and the second voltage change can be determined based on the first common-mode voltage and the second common-mode voltage.

[0080] Take U DL_n U represents the DC voltage of the first target sample collected at the current time t. DL_OP1 U represents the DC voltage of the second target collected at the current time t. DL_k U represents the first historical DC voltage of the first transmission line. DL_OP2 The third historical DC voltage of the second transmission line, t k U DL_k and U DL_OP2 The collection time, U COM (t) represents the first common-mode voltage, U COM (t k ) represents the second common-mode voltage, ΔU COM Taking the second voltage change as an example, U COM (t), U COM (t k ) and ΔU COM The calculation formula is:

[0081] U COM (t)=(U DL_n +U DL_OP1 ) / 2;

[0082] U COM (t k )=(U DL_m +U DL_OP2 ) / 2;

[0083] ΔU COM =U COM (t)-U COM (t k ).

[0084] Furthermore, in one embodiment, when the DC voltage of the first transmission line is positive during normal operation and the DC voltage of the second transmission line is negative during normal operation, determining the fault occurrence of the first transmission line based on the second voltage change includes: if the second voltage change is less than a set change value U... COM_SET Then it is determined that a fault has occurred in the first transmission line, and the change in the set value U COM_SET The value is negative. Taking the first transmission line as an example... Figure 2 The second transmission line is a DC line in the middle. Figure 2 Taking the second-stage DC circuit as an example, when the second voltage change ΔU COM COM_SET When this occurs, it is determined that a fault has occurred in the DC line of that pole. This fault is generally a grounding fault.

[0085] In another embodiment, when the DC voltage of the first transmission line is negative during normal operation and the DC voltage of the second transmission line is positive during normal operation, the fault occurrence of the first transmission line is determined based on the second voltage change, including: if the second voltage change is greater than a set change value U. COM_SET The absolute value of the change indicates that a fault has occurred in the first transmission line, and the change is set to U. COM_SET The value is negative. Taking the first transmission line as an example... Figure 2 The second DC transmission line in the middle is... Figure 2 Taking the DC circuit as an example, when the second voltage change ΔU COM >|U COM_SET When this occurs, it is determined that a fault has occurred in the DC line of pole two. This fault is generally a grounding fault.

[0086] Figure 4 This is a schematic diagram of the voltage surge protection device for high-voltage direct current transmission lines provided in this application embodiment. Figure 4 As shown, the voltage surge protection device includes:

[0087] The acquisition unit 401 is configured to acquire the current first target DC voltage and the current target DC current of the first transmission line; wherein the first transmission line is a high voltage DC transmission line in a high voltage DC transmission system;

[0088] The determining unit 402 is configured to determine a first voltage change amount and voltage change rate based on a first target DC voltage, and to determine a current change amount based on a target DC current;​

[0089] The control unit 403 is configured to control the DC circuit breaker connected to the first transmission line to open when the product of the first voltage change and the current change is less than the direction criterion setting, the absolute value of the voltage change rate is greater than the change rate setting, and the duration of the DC voltage of the first transmission line being lower than the voltage setting is greater than or equal to the first duration setting.

[0090] In some embodiments, the control unit 403 is also configured to: after controlling the opening of the DC circuit breaker connected to the first transmission line, and after a second time interval, control the DC circuit breaker to close.

[0091] In some embodiments, the determining unit 402 is configured to determine a first voltage change based on a first target DC voltage, including:

[0092] Obtain the first historical DC voltage of the first transmission line, wherein the time interval between the acquisition time of the first historical DC voltage and the current time is greater than or equal to a first time duration setting.

[0093] The first voltage change is determined based on the first target DC voltage and the first historical DC voltage.

[0094] In some embodiments, the determining unit 402 is configured to determine the voltage change rate, including:

[0095] The second historical DC voltage of the first transmission line is obtained, and the time interval between the acquisition time of the second historical DC voltage and the current time is less than the first time duration setting.

[0096] Based on the first target DC voltage, the second historical DC voltage, the acquisition time of the second historical DC voltage, and the current time mentioned above, the voltage change rate is determined.

[0097] In some embodiments, the determining unit 402 is configured to determine the current change based on the target DC current, including:

[0098] Obtain the historical DC current of the first transmission line, wherein the time interval between the historical DC current acquisition time and the current time is greater than or equal to the first time duration setting.

[0099] The change in current is determined based on the target DC current and historical DC current.

[0100] In some embodiments, the direction criterion is less than or equal to the product of the change in DC voltage and the change in DC current of the HVDC transmission line during normal operation of the HVDC transmission system.

[0101] In some embodiments, the acquisition unit 401 is further configured to acquire the current second target DC voltage of the second transmission line, the second transmission line being a high voltage DC transmission line in a high voltage DC transmission system and belonging to a different pole from the first transmission line;

[0102] The determining unit 402 is also configured to determine the common-mode voltage and the second voltage change of the common-mode voltage based on the first target DC voltage and the second target DC voltage, and to determine the fault occurrence of the first transmission line based on the second voltage change.

[0103] In some embodiments, the DC voltage of the first transmission line is positive during normal operation, and the DC voltage of the second transmission line is negative during normal operation.

[0104] The determining unit 402 is configured to determine the fault occurrence status of the first transmission line based on a second voltage change, including:

[0105] If the change in the second voltage is less than the set value of the change, then it is determined that the first transmission line has a fault, and the set value of the change is negative.

[0106] In some embodiments, the DC voltage of the first transmission line is negative during normal operation, and the DC voltage of the second transmission line is positive during normal operation.

[0107] The determining unit 402 is configured to determine the fault occurrence status of the first transmission line based on a second voltage change, including:

[0108] If the change in the second voltage is greater than the absolute value of the change setting, then the first transmission line is determined to have a fault, and the change setting is negative.

[0109] It should be noted that other aspects and implementation details of the voltage surge protection device for high-voltage direct current transmission lines provided in some embodiments of this application are the same as or similar to the voltage surge protection method for high-voltage direct current transmission lines described above, and will not be repeated here.

[0110] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0111] The voltage surge protection method and device for high-voltage direct current transmission lines provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for protecting against voltage surges in high-voltage direct current transmission lines, characterized in that, include: Obtain the current first target DC voltage and the current target DC current of the first transmission line; wherein, the first transmission line is a high-voltage DC transmission line in a high-voltage DC transmission system; The first voltage change and voltage change rate are determined based on the first target DC voltage, and the current change is determined based on the target DC current; If the product of the first voltage change and the current change is less than the direction criterion setting, the absolute value of the voltage change rate is greater than the change rate setting, and the duration of the DC voltage of the first transmission line being lower than the voltage setting is greater than or equal to the first duration setting, the DC circuit breaker connected to the first transmission line is controlled to open.

2. The voltage surge protection method according to claim 1, characterized in that, After the DC circuit breaker connected to the first transmission line is opened, the following steps are also included: After the second set interval, the DC circuit breaker is controlled to close.

3. The voltage surge protection method according to claim 1, characterized in that, Determining the first voltage change based on the first target DC voltage includes: Obtain the first historical DC voltage of the first transmission line, wherein the time interval between the acquisition time of the first historical DC voltage and the current time is greater than or equal to the first duration setting. The first voltage change is determined based on the first target DC voltage and the first historical DC voltage.

4. The voltage surge protection method according to claim 1, characterized in that, The steps for determining the rate of voltage change include: Obtain the second historical DC voltage of the first transmission line, wherein the time interval between the acquisition time of the second historical DC voltage and the current time is less than the first time duration setting. The voltage change rate is determined based on the first target DC voltage, the second historical DC voltage, the acquisition time of the second historical DC voltage, and the current time.

5. The voltage surge protection method according to claim 1, characterized in that, Determining the current change based on the target DC current includes: Obtain the historical DC current of the first transmission line, wherein the time interval between the acquisition time of the historical DC current and the current time is greater than or equal to the first time duration setting. The change in current is determined based on the target DC current and the historical DC current.

6. The voltage surge protection method according to claim 1, characterized in that, The direction criterion value is less than or equal to the product of the change in DC voltage and the change in DC current of the high voltage direct current transmission line during normal operation of the high voltage direct current transmission system.

7. The voltage surge protection method according to any one of claims 1-6, characterized in that, Also includes: Obtain the current second target DC voltage of the second transmission line, which is a high-voltage DC transmission line in the high-voltage DC transmission system and belongs to a different pole from the first transmission line; Based on the first target DC voltage and the second target DC voltage, determine the common-mode voltage and the second voltage change of the common-mode voltage; Based on the second voltage change, the fault occurrence of the first transmission line is determined.

8. The voltage surge protection method according to claim 7, characterized in that, The DC voltage of the first transmission line is positive during normal operation, and the DC voltage of the second transmission line is negative during normal operation. Based on the second voltage change, the fault occurrence status of the first transmission line is determined, including: If the second voltage change is less than the change set value, then it is determined that the first transmission line has a fault, and the change set value is negative.

9. The voltage surge protection method according to claim 7, characterized in that, The DC voltage of the first transmission line is negative during normal operation, and the DC voltage of the second transmission line is positive during normal operation. Based on the second voltage change, the fault occurrence status of the first transmission line is determined, including: If the second voltage change is greater than the absolute value of the change setpoint, then it is determined that the first transmission line has a fault, and the change setpoint is negative.

10. A voltage surge protection device for high-voltage direct current transmission lines, characterized in that, include: The acquisition unit is configured to acquire the current first target DC voltage and the current target DC current of the first transmission line; wherein the first transmission line is a high-voltage DC transmission line in a high-voltage DC transmission system; The determining unit is configured to determine a first voltage change amount and a voltage change rate based on the first target DC voltage, and to determine a current change amount based on the target DC current; The control unit is configured to control the DC circuit breaker connected to the first transmission line to open when the product of the first voltage change and the current change is less than a direction criterion setting, the absolute value of the voltage change rate is greater than a change rate setting, and the duration for which the DC voltage of the first transmission line is lower than a voltage setting is greater than or equal to a first duration setting.

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