Line fault determination method, device, equipment and storage medium

Abstract

The present disclosure relates to the technical field of power transmission, and in particular provides a method, apparatus, device, and storage medium for determining a line fault. The method includes: when it is determined that a fault has occurred in the line to be protected, extracting first voltage values and second voltage values corresponding to each sampling moment within a preset time window; determining a metric coefficient based on the first voltage value and the second voltage value; and determining the fault location of the line to be protected based on the metric coefficient and the protection setting value. By using the voltage values on both sides of the line within a time window after the fault and calculating the voltage values based on the proposed metric coefficient, and determining the fault range based on the metric coefficient, compared with traditional current differential protection, it can quickly and reliably identify internal and external faults, and also has a certain sensitivity to high-resistance faults, improving the speed of existing pilot protection and meeting the four requirements of relay protection.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power transmission, and particularly to a method, device, equipment, and storage medium for determining line faults. Background Art

[0002] Flexible DC transmission technology has advantages such as strong controllability, high power quality, and flexible operation modes compared with traditional high-voltage DC transmission. Therefore, this technology will reliably become a powerful tool for solving the problems of flexible grid connection and consumption of long-distance external power transmission systems for new energy bases. Compared with AC power transmission, the DC transmission system is a "low-inertia" system, where the fault current develops rapidly, and the transmission line will become the part with the highest fault probability in the system due to crossing different climate zones. Therefore, it is necessary to study a safe and reliable line protection scheme.

[0003] In the related art, for flexible DC transmission, double-ended quantity protection is often adopted. The double-ended quantity protection mainly uses pilot current differential protection, which can better make up for the deficiencies of single-ended quantity protection and ensure absolute selectivity and reliability. However, considering the influence of distributed capacitance, this protection requires a certain delay to operate, which greatly expands the scope of fault isolation and removal. Summary of the Invention

[0004] To solve the above technical problems, the present disclosure provides a method, device, equipment, and storage medium for determining line faults, which can quickly and reliably identify the fault range of the zone, and also has a certain sensitivity to high-resistance faults, improving the speed of the existing pilot protection and meeting the four requirements of relay protection.

[0005] In a first aspect, the present disclosure provides a method for determining a line fault, the method comprising: when it is determined that a fault has occurred in the line to be protected, extracting a first voltage value and a second voltage value corresponding to each sampling moment within a preset time window; determining a metric coefficient based on the first voltage value and the second voltage value; and determining the fault location of the line to be protected based on the metric coefficient and the protection setting value.

[0006] In a second aspect, the present disclosure provides a device for determining a line fault, the device comprising: a voltage value extraction module, configured to extract a first voltage value and a second voltage value corresponding to each sampling moment within a preset time window when it is determined that a fault has occurred in the line to be protected; a metric coefficient calculation module, configured to determine a metric coefficient based on the first voltage value and the second voltage value; and a fault range determination module, configured to determine the fault location of the line to be protected based on the metric coefficient and the protection setting value.

[0007] In a third aspect, the present disclosure provides an electronic device, which includes: one or more processors; a storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the line fault determination method in the first aspect as described above.

[0008] In a fourth aspect, the present disclosure provides a storage medium, which may be a computer-readable storage medium, on which a computer program is stored. The feature is that when the program is executed by a processor, it implements the line fault determination method in the first aspect as described above.

[0009] The technical solutions provided by the embodiments of the present disclosure have the following advantages compared with the prior art:

[0010] The embodiments of the present disclosure provide a line fault determination method, device, equipment and storage medium. The method includes: when it is determined that a fault occurs in the line to be protected, extracting the first voltage value and the second voltage value corresponding to each sampling moment within a preset time window; determining a metric coefficient based on the first voltage value and the second voltage value; and determining the fault location of the line to be protected based on the metric coefficient and the protection setting value. By using the voltage values on both sides of the line within a time window after the fault and calculating the voltage values based on the proposed metric coefficient, and determining the fault range based on the metric coefficient, compared with traditional current differential protection, it can quickly and reliably identify internal and external faults, and also has a certain sensitivity to high-resistance faults, improving the speed of existing pilot protection and meeting the four requirements of relay protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure.

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0013] Figure 1 It is a flowchart of a line fault determination method provided by an embodiment of the present disclosure;

[0014] Figure 2 It is a flowchart of another line fault determination method provided by an embodiment of the present disclosure;

[0015] Figure 3Schematic diagram of the ±500kV new energy transmission system via flexible DC provided by the embodiments of the present disclosure;

[0016] Figure 4 Schematic diagram of the first voltage value and the calculated value of its Metric coefficient when a fault occurs at different positions within the area provided by the embodiments of the present disclosure;

[0017] Figure 5 Schematic diagram of the first voltage value and the calculated value of its Metric coefficient when a fault occurs at different positions outside the area provided by the embodiments of the present disclosure;

[0018] Figure 6 Schematic diagram of the structure of the line fault determination device provided by the embodiments of the present disclosure;

[0019] Figure 7 Schematic diagram of the structure of the electronic device provided by the embodiments of the present disclosure. Detailed implementation manners

[0020] In order to more clearly understand the above objects, features and advantages of the present disclosure, the solutions of the present disclosure will be further described below. It should be noted that, without conflict, the embodiments of the present disclosure and the features in the embodiments may be combined with each other.

[0021] Many specific details are set forth in the following description in order to fully understand the present disclosure, but the present disclosure may be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present disclosure, rather than all of the embodiments.

[0022] As used herein, the term "including" and its variants are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0023] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order of the functions executed by these devices, modules or units or the interdependent relationship.

[0024] It should be noted that the modifications of "one" and "multiple" mentioned in the present disclosure are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise clearly specified in the context, it should be understood as "one or more".

[0025] The line fault determination method provided by the embodiments of the present disclosure will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0026] Figure 1 The figure is a flowchart of a method for determining a line fault in an embodiment of the present disclosure. This embodiment is applicable to the situation of identifying faults in a DC transmission line. This method can be executed by a line fault determination device, which can be implemented in a software and / or hardware manner, and can be configured in an electronic device.

[0027] As Figure 1 shown, the method for determining a line fault provided by the embodiment of the present disclosure mainly includes steps S101 - S103.

[0028] S101. When it is determined that a fault has occurred in the line to be protected, extract the first voltage value and the second voltage value corresponding to each sampling moment within a preset time window.

[0029] The above line can be understood as a transmission line in a power system, which can be a DC transmission line or an AC transmission line. Optionally, the above line is a flexible DC transmission line. The line to be protected refers to the DC transmission line for which the line fault determination method provided by the embodiment is used for fault identification. Taking the above line to be protected as a DC transmission line as an example. When using DC transmission technology, it is necessary to convert the alternating current of the power plant into direct current through a rectifier, and then transmit the direct current through a DC line to an inverter, which converts the direct current into alternating current for users to use. The above line to be protected can be understood as the line for transmitting direct current between the rectifier and the inverter. A fault in the line to be protected may be a ground fault, a short - circuit fault, etc.

[0030] In order to identify faults and protect the line to be protected, it is necessary to periodically measure or detect the line parameters in the line to be protected. After the line fault determination method is started, the line parameters are measured periodically, and the time interval between two adjacent sampling moments is a sampling period.

[0031] The preset time window can be understood as a time interval after a fault occurs in the line to be protected. Further, the preset time window refers to a time interval starting from the moment when a fault occurs in the line to be protected. The length of the preset time window can be preset according to empirical values. The length of the preset time window can also be dynamically adjusted according to the fault location of the line to be protected.

[0032] In a specific implementation, the preset time window is the time interval between a first moment and a second moment, where the first moment is the moment when it is determined that a fault has occurred in the line to be protected, and the second moment is the earliest arrival moment of the second voltage backward traveling wave after the protection start is calibrated using the wavelet transform modulus maximum.

[0033] In this embodiment, when it is determined that a fault occurs in the line to be protected, the moment when the fault occurs in the line to be protected is recorded as the first moment t1. The earliest arrival moment of the second voltage backward traveling wave after the protection starts can be calibrated by using the wavelet transform modulus maximum as the second moment t2. Among them, the first moment t1 is less than the second moment t2.

[0034] The time interval between the first moment t1 and the second moment t2 is used as the preset time window. Specifically, the preset time window can be expressed by formula (1).

[0035] T=t2 - t1 (1)

[0036] Among them, T is the length of the preset time window after dynamic adjustment; t2 is the earliest arrival moment of the second voltage backward traveling wave after the protection starts calibrated by using the wavelet transform modulus maximum method; t1 is the moment when the fault occurs in the line to be protected.

[0037] Dynamically adjusting the length of the preset time window according to the fault location of the line to be protected can avoid the influence of subsequent traveling waves on the Metric coefficient and improve the accuracy of the fault range.

[0038] The first voltage value can be understood as the voltage value of the rectifier side of the DC transmission line in the L mode, and the second voltage value can be understood as the voltage value of the inverter side of the DC transmission line in the L mode. The L mode can be understood as the line voltage of the DC transmission line. The voltage value of the rectifier side can refer to the voltage value input by the rectifier to the line to be protected, and the voltage value of the inverter side can refer to the voltage value input by the line to be protected to the inverter.

[0039] The voltage value of the DC transmission line in the L mode can be calculated by formula (2).

[0040]

[0041] Among them, V L is the voltage value of the DC transmission line in the L mode, V po is the measured positive pole voltage value, V Npo is the rated positive pole voltage value, V ne is the measured negative pole voltage value, V Nne is the rated negative pole voltage value.

[0042] The rated positive pole voltage value refers to the rated value of the positive pole voltage when the line to be protected is operating normally, and the rated negative pole voltage value refers to the rated value of the negative pole voltage when the line to be protected is operating normally. Among them, the rated positive pole voltage value and the rated negative pole voltage value are determined by the transmission capacity of the line to be protected itself. For example: if the line to be protected is a 1000KV high-voltage transmission line, then the rated positive pole voltage value is 1000KV, and the rated negative pole voltage value is -1000KV.

[0043] In a possible implementation, for each sampling moment, obtain the first positive-pole voltage value and the first negative-pole voltage value of the line to be protected at the rectifier side; obtain the second positive-pole voltage value and the second negative-pole voltage value of the line to be protected at the inverter side; calculate the first voltage value based on the first positive-pole voltage value, the first negative-pole voltage value, and the L-mode voltage formula; calculate the second voltage value based on the second positive-pole voltage value, the second negative-pole voltage value, and the L-mode voltage formula.

[0044] The positive-pole voltage value refers to the positive-pole voltage value of the line to be protected, and the negative-pole voltage value refers to the negative-pole voltage value of the line to be protected. Among them, the measured positive-pole voltage value is positive, and the measured negative-pole voltage value is negative.

[0045] The first positive-pole voltage value refers to the positive-pole voltage value measured at the rectifier side of the line to be protected, the first negative-pole voltage value refers to the negative-pole voltage value measured at the rectifier side of the line to be protected, the second positive-pole voltage value refers to the positive-pole voltage value measured at the inverter side of the line to be protected, and the second negative-pole voltage value refers to the negative-pole voltage value measured at the inverter side of the line to be protected.

[0046] For each sampling moment, collect the first positive-pole voltage value, the first negative-pole voltage value, the second positive-pole voltage value, and the second negative-pole voltage value. Take the first positive-pole voltage value as the measured positive-pole voltage value and the first negative-pole voltage value as the measured negative-pole voltage value, and substitute them into the above formula (2) for calculation to obtain the first voltage value; take the second positive-pole voltage value as the measured positive-pole voltage value and the second negative-pole voltage value as the measured negative-pole voltage value, and substitute them into the above formula (2) for calculation to obtain the second voltage value.

[0047] After determining that a fault has occurred in the line to be protected and calculating the preset time window, determine all sampling moments included in the preset time window. For each sampling moment, obtain the first voltage value on the DC side of the HVDC transmission line in the L mode and the second voltage value on the inverter side corresponding to each sampling moment.

[0048] In one embodiment, during the operation of the line to be protected, for each sampling moment, measure the first positive-pole voltage value and the first negative-pole voltage value of the rectifier side of the DC output line, and substitute the first positive-pole voltage value and the first negative-pole voltage value into formula (2) to obtain the first voltage value on the rectifier side in the L mode corresponding to this sampling moment. Measure the second positive-pole voltage value and the second negative-pole voltage value of the inverter side of the DC output line, and substitute the second positive-pole voltage value and the second negative-pole voltage value into formula (2) to obtain the second voltage value on the inverter side in the L mode corresponding to this sampling moment. After determining that a fault has occurred in the line to be protected and calculating the preset time window, extract the first voltage value on the rectifier side in the L mode and the second voltage value on the inverter side corresponding to each sampling moment included in the preset time window as the first voltage value and the second voltage value corresponding to each sampling moment.

[0049] In another embodiment, during the operation of the line to be protected, for each sampling moment, the first positive voltage value and the first negative voltage value of the rectifier side of the DC output line are measured and recorded, and the second positive voltage value and the second negative voltage value of the inverter side of the DC output line are measured. After determining that a fault has occurred in the line to be protected and calculating a preset time window, the first positive voltage value and the first negative voltage value of the rectifier side included in each sampling moment within the preset time window are extracted, as well as the second positive voltage value and the second negative voltage value of the inverter side. For each sampling moment included in the preset time window, the first positive voltage value and the first negative voltage value are substituted into formula (2) to obtain the first voltage value of the rectifier side in the L mode corresponding to this sampling moment. The second positive voltage value and the second negative voltage value are substituted into formula (2) to obtain the second voltage value of the inverter side in the L mode corresponding to this sampling moment.

[0050] S102. Determine the Metric coefficient of the metric standard based on the first voltage value and the second voltage value.

[0051] The Metric coefficient refers to substituting the first voltage value and the second voltage value of each sampling moment into the Metric formula to obtain a value, which is used to determine whether the fault that occurred is an internal fault or an external fault.

[0052] The Metric coefficient can be calculated using all the first voltage values and second voltage values extracted within the preset time window. When there are many sampling moments within the preset time window, that is, when the number of first voltage values and second voltage values is large, a part of the first voltage values and second voltage values can be selected to calculate the Metric coefficient.

[0053] In a specific implementation, the Metric coefficient is calculated by formula (3):

[0054]

[0055] where k is the kth sampling moment, a k is the first voltage value at the kth sampling moment, b k is the second voltage value at the kth sampling moment, that is, the second voltage value of the inverter side in the L mode. Metric(a k , a k ) is the Metric coefficient at the kth sampling moment, a i is the first voltage value at the ith sampling moment, that is, the first voltage value of the rectifier side in the L mode at the ith sampling moment, b iis the second voltage value at the i-th sampling moment, that is, the second voltage value on the inverter side in the L mode at the i-th sampling moment, where 0 < i < n, and n is the number of samplings within the preset time window. In a specific implementation, to ensure the accuracy of the calculation of this Metric coefficient, the value of n is taken as 20.

[0056] This embodiment provides a calculation method for the Metric coefficient, providing an identification criterion for judging internal and external faults in the area to quickly and reliably identify internal and external faults.

[0057] S103. Determine the fault location of the line to be protected based on the Metric coefficient and the protection setting value.

[0058] Protection setting value Metric set refers to a reference value preset for evaluating the fault range. Further, the protection setting value Metric set needs to consider the influence of line attenuation and distortion, and the transformation error of the voltage transformer on the protection setting. The Metric coefficient satisfies the fault identification criterion and thus realizes the judgment of internal and external faults.

[0059] The fault location of the line to be protected refers to the specific location of the fault on the line to be protected. Specifically, the fault location of the line to be protected includes whether the fault is an internal fault in the area and whether the fault is an external fault outside the area. Among them, an internal fault refers to a fault between the line circuit breakers at both ends of the line where the series compensation device is located, and an external fault is a fault outside the line circuit breakers at both ends of the line where the series compensation device is located. In other words, an internal fault is a fault that occurs between this section of the line to be protected, that is, a fault that occurs between this section of the line between the rectifier side and the inverter side; an external fault is a fault that occurs in other lines outside the line to be protected, that is, a fault that occurs in other lines outside this section of the line between the rectifier side and the inverter side.

[0060] Determining the fault location of the line to be protected based on the Metric coefficient and the protection setting value includes: determining whether the fault of the line to be protected is an internal fault or an external fault based on the magnitude relationship between the Metric coefficient and the protection setting value.

[0061] Specifically, determining the fault location of the line to be protected based on the Metric coefficient and the protection setting value includes: if the Metric coefficient is greater than the protection setting value, it is determined that an internal fault has occurred in the line to be protected; if the Metric coefficient is less than the protection setting value, it is determined that an external fault has occurred in the line to be protected.

[0062] In one implementation, the Metric coefficient is compared with the protection setting value. If the Metric coefficient is greater than or equal to the protection setting value, it is determined that a fault occurs within the line to be protected, that is, a fault between this section of the line to be protected; if the Metric coefficient is less than the protection setting value, it is determined that a fault occurs outside the line to be protected, that is, a fault occurs in other lines outside the line to be protected.

[0063] In another implementation, the difference between the Metric coefficient and the protection setting value is calculated. If the difference is greater than 0, or infinitely close to 0, it is determined that a fault occurs within the line to be protected. If the difference is much less than 0, it is determined that a fault occurs outside the line to be protected.

[0064] Furthermore, the discrimination method for the fault location of the line to be protected can be implemented by formula (4).

[0065]

[0066] Among them, Metric is the Metric coefficient calculated in S102; Metric set is the preset protection setting value.

[0067] Specifically, when a fault occurs within the zone, the calculated value of the Metric coefficient is approximately the protection setting value; when a fault occurs outside the zone, the calculated value of the Metric coefficient is much less than the protection setting value.

[0068] The embodiments of the present disclosure provide a method for determining a line fault. The method includes: when it is determined that a fault occurs in the line to be protected, extracting the first voltage value and the second voltage value corresponding to each sampling moment within a preset time window; determining the metric standard Metric coefficient based on the first voltage value and the second voltage value; and determining the fault location of the line to be protected based on the Metric coefficient and the protection setting value. By using the voltage values at the rectifier side and the inverter side of the transmission line within a time window after the fault, and calculating the voltage values based on the proposed Metric coefficient, and determining the fault range based on the Metric coefficient, compared with the traditional current differential protection, it can quickly and reliably identify faults inside and outside the zone, and also has a certain sensitivity to high-resistance faults, improving the speed of the existing pilot protection and meeting the four requirements of relay protection.

[0069] Based on the above embodiments, the embodiments of the present application further optimize the method for determining a line fault, such as Figure 2 shown, the optimized method for determining a line fault includes the following steps:

[0070] S201. Obtain the third voltage value of the line to be protected at N sampling moments.

[0071] Among them, the third voltage value includes the voltage value in the L mode of the line to be protected; and / or, the third voltage value includes: the voltage value in the Z mode of the circuit to be protected. Among them, the voltage value in the L mode may include the voltage value on the rectifier side in the L mode or the voltage value on the inverter side in the L mode; the voltage value in the Z mode may include the voltage value on the rectifier side in the Z mode or the voltage value on the inverter side in the Z mode.

[0072] Among them, the specific value of N can be set according to the actual situation. Further, N is an odd number, that is, the current sampling moment is the middle value of N sampling moments. For example: when N is 5, the N sampling moments include the (k - 1)-th sampling moment, the (k - 2)-th sampling moment, the k-th sampling moment, the (k + 1)-th sampling moment, and the (k + 2)-th sampling moment.

[0073] Among them, the k-th sampling moment is the current sampling moment, the (k - 1)-th sampling moment is the sampling moment at an interval of one sampling period before the k-th sampling moment, the (k - 2)-th sampling moment is the sampling moment at an interval of two sampling periods before the k-th sampling moment, the (k + 1)-th sampling moment is the sampling moment at an interval of one sampling period after the k-th sampling moment, and the (k + 2)-th sampling moment is the sampling moment at an interval of two sampling periods after the k-th sampling moment.

[0074] The calculation method of the voltage value in the L mode can refer to the description in the above embodiments, and will not be elaborated in the embodiments of the present application.

[0075] Next, the calculation method of the voltage value in the Z mode will be described.

[0076] The voltage value of the DC transmission line in the Z mode can be calculated by formula (5).

[0077]

[0078] Among them, V Z is the voltage value of the DC transmission line in the Z mode, V po is the measured positive pole voltage value, V Npo is the rated positive pole voltage value, V ne is the measured negative pole voltage value, V Nne is the rated negative pole voltage value.

[0079] In a possible implementation manner, for each sampling moment, obtain the first positive pole voltage value and the first negative pole voltage value of the line to be protected on the rectifier side; obtain the second positive pole voltage value and the second negative pole voltage value of the line to be protected on the inverter side; calculate the voltage value of the Z mode rectifier side based on the first positive pole voltage value, the first negative pole voltage value, and the Z mode voltage formula; calculate the voltage value of the Z mode inverter side based on the second positive pole voltage value, the second negative pole voltage value, and the Z mode voltage formula.

[0080] For each sampling moment, the first positive electrode voltage value, the first negative electrode voltage value, the second positive electrode voltage value, and the second negative electrode voltage value are collected. The first positive electrode voltage value is used as the measured positive electrode voltage value, and the first negative electrode voltage value is used as the measured negative electrode voltage value, and they are substituted into the above formula (3) for calculation to obtain the voltage value of the rectifier side in the Z mode; the second positive electrode voltage value is used as the measured positive electrode voltage value, and the second negative electrode voltage value is used as the measured negative electrode voltage value, and they are substituted into the above formula (3) for calculation to obtain the voltage value of the inverter side in the Z mode.

[0081] S202. Calculate the composite voltage value at the current sampling moment based on the third voltage values at N sampling moments, where the N sampling moments include the current sampling moment.

[0082] Among them, the composite voltage value is the judgment basis for determining whether the line to be protected has a fault. The composite voltage value is determined by the ratio of the third voltage value at non-current sampling moments to the third voltage value at the current sampling moment.

[0083] When the non-current sampling moment is a sampling moment before the current sampling moment, calculate the first sum value of the ratios of the third voltage values at each non-current sampling moment to the third voltage value at the current sampling moment; when the non-current sampling moment is a sampling moment after the current sampling moment, calculate the second sum value of the ratios of the third voltage values at each non-current sampling moment to the third voltage value at the current sampling moment; take the difference between the above first sum value and the second sum value as the composite voltage value.

[0084] Specifically, calculate the ratio of the third voltage value at the (k - 2)th sampling moment to the third voltage value at the kth sampling moment as the fourth ratio, calculate the ratio of the third voltage value at the (k - 1)th sampling moment to the third voltage value at the kth sampling moment as the fifth ratio, calculate the ratio of the third voltage value at the (k + 1)th sampling moment to the third voltage value at the kth sampling moment as the sixth ratio, and calculate the ratio of the third voltage value at the (k + 2)th sampling moment to the third voltage value at the kth sampling moment as the seventh ratio. Take the sum value of the fourth ratio and the fifth ratio, then subtract the sixth ratio, and then subtract the seventh ratio to obtain a value as the composite voltage value.

[0085] In a specific implementation manner, the composite voltage value at the current sampling moment is calculated through formula (6):

[0086]

[0087] Among them, R u(k) is the composite voltage value at the current sampling moment, V(k - 1) is the third voltage value at the (k - 1)-th sampling moment, V(k - 2) is the third voltage value at the (k - 2)-th sampling moment, V(k) is the voltage sampling value at the current sampling moment, V(k + 1) is the third voltage value at the (k + 1)-th sampling moment, and V(k + 2) is the third voltage value at the (k + 2)-th sampling moment.

[0088] In S201, the third voltage value includes the voltage value in the L mode and / or the voltage value in the Z mode. Substitute the voltage value in the L mode at the (k - 2)-th sampling moment, the voltage value in the L mode at the (k - 1)-th sampling moment, the voltage value in the L mode at the k-th sampling moment, the voltage value in the L mode at the (k + 1)-th sampling moment, and the voltage value in the L mode at the (k + 2)-th sampling moment into the above formula (6) to calculate the composite voltage value in the L mode.

[0089] Substitute the voltage value in the Z mode at the (k - 2)-th sampling moment, the voltage value in the Z mode at the (k - 1)-th sampling moment, the voltage value in the Z mode at the k-th sampling moment, the voltage value in the Z mode at the (k + 1)-th sampling moment, and the voltage value in the Z mode at the (k + 2)-th sampling moment into the above formula (6) to calculate the composite voltage value in the Z mode.

[0090] S203. When the composite voltage value is greater than the composite voltage setting value, determine that a fault has occurred in the line to be protected.

[0091] In specific implementation, if the composite voltage value at the current sampling moment is greater than or equal to the composite voltage setting threshold, it is determined that a fault has occurred in the new energy transmission system via VSC-HVDC, and the start time is recorded as t1, and this start time t1 is used to determine the preset time window later.

[0092] Since in S202, the composite voltage value in the L mode and the composite voltage value in the Z mode may be calculated simultaneously. Among them, the composite voltage value in the L mode has a corresponding composite voltage setting value in the L mode, and the composite voltage value in the Z mode has a corresponding composite voltage setting value in the Z mode. Among them, the composite voltage setting value in the L mode and the composite voltage setting value in the Z mode may be the same or different. The composite voltage setting value in the L mode and the composite voltage setting value in the Z mode can be set according to the actual situation, and the embodiments of the present application do not specifically limit them.

[0093] If the composite voltage value in the L mode at the current sampling moment is greater than the composite voltage setting threshold in the L mode, or the composite voltage value in the Z mode at the current sampling moment is greater than the composite voltage setting threshold in the Z mode, it is determined that a fault has occurred in the new energy transmission system via VSC-HVDC, and the start time is recorded as t1, and this start time t1 is used to determine the preset time window later.

[0094] If the composite voltage value in the L mode at the current sampling moment is less than the composite voltage setting threshold in the L mode, and the composite voltage value in the Z mode at the current sampling moment is less than the composite voltage setting threshold in the Z mode, it indicates that no fault has occurred. According to the method provided in S204 - S205, calculate the composite voltage value at the next sampling moment, and determine whether a fault has occurred in the line to be protected at the next sampling moment.

[0095] S204. In the case of determining that a fault has occurred in the line to be protected, extract the first voltage value and the second voltage value corresponding to each sampling moment within a preset time window.

[0096] S205. Determine the Metric coefficient of the measurement standard based on the first voltage value and the second voltage value.

[0097] S206. Determine the fault location of the line to be protected based on the Metric coefficient and the protection setting value.

[0098] The execution processes of S204 - S206 provided in the embodiments of the present application are the same as those of S101 - S103 provided in the above embodiments. For details, reference can be made to the descriptions in the above embodiments, and no further elaboration will be provided in the embodiments of the present application.

[0099] S207. Calculate the pole selection parameter based on the positive - pole voltage and the negative - pole voltage of the line to be protected.

[0100] In the above steps, it is determined whether a fault has occurred in the line to be protected and the location of the fault. S207 - S208 are used to determine the fault type. The pole selection parameter is the basis for judging the fault type. The positive - pole voltage of the line to be protected can be the measured positive - pole voltage value at the rectifier side of the line to be protected, and the negative - pole voltage can be the measured negative - pole voltage value at the rectifier side of the line to be protected. Alternatively, the positive - pole voltage of the line to be protected can be the measured positive - pole voltage value at the inverter side of the line to be protected, and the negative - pole voltage can be the measured negative - pole voltage value at the inverter side of the line to be protected.

[0101] In a possible implementation, the pole selection parameter is determined by the sum of the third ratios at multiple sampling moments, where the third ratio is the ratio of the absolute value of the positive - pole voltage to the absolute value of the negative - pole voltage.

[0102] Specifically, for each sampling moment, calculate the ratio of the measured absolute value of the positive - pole voltage to the measured absolute value of the negative - pole voltage as the third ratio. The number of third ratios is the same as the number of sampling moments. Add up the third ratios at each sampling moment to obtain the pole selection parameter.

[0103] The pole selection parameter is calculated by formula (7):

[0104]

[0105] Among them, C is the pole selection parameter at the k-th sampling moment, and V po (k) is the measured positive pole voltage value at the k-th sampling moment, and |V ne (k)| is the measured negative pole voltage value at the k-th sampling moment, and M represents the set of sampling moments after the fault occurs.

[0106] S208. Determine the fault type of the system to be protected based on the relationship between the pole selection parameter and the set value of the pole selection parameter.

[0107] Among them, the fault types include positive pole grounding fault, negative pole grounding fault, and bipolar short-circuit fault. A positive pole grounding fault can be understood as a fault where the positive pole of the line is connected to the ground, a negative pole grounding fault can be understood as a fault where the negative pole of the line is connected to the ground, and a bipolar short-circuit fault can be understood as a fault where the positive pole and the negative pole of the line are connected.

[0108] In a possible implementation manner, determining the fault type of the system to be protected based on the relationship between the pole selection parameter and the set value of the pole selection parameter includes: if the pole selection parameter is greater than the set value of the pole selection parameter, determine that the fault type of the system to be protected is a positive pole grounding fault; if the pole selection parameter is less than the reciprocal of the set value of the pole selection parameter, determine that the fault type of the system to be protected is a negative pole grounding fault; if the pole selection parameter is greater than the reciprocal of the set value of the pole selection parameter and less than the set value of the pole selection parameter, determine that the fault type of the system to be protected is a bipolar short-circuit fault.

[0109] The determination of the fault type is determined by formula (8):

[0110]

[0111] Among them, C is the calculated pole selection parameter; Vpo is the measured positive pole voltage value, Vne is the measured negative pole voltage value; C set is the set value of the pole selection parameter, which is set to 1.25.

[0112] In specific implementation, this pole selection coefficient is constructed based on the internal relationship between the positive and negative voltages, and the threshold setting is simple and reliable.

[0113] When S208 determines that the fault is an in-zone fault, calculate the pole selection parameter according to the measured positive pole voltage value and the measured negative pole voltage value. If the calculated pole selection parameter is greater than the set value of the pole selection parameter, it is a positive pole grounding fault. Therefore, the circuit breaker disconnects the positive pole line to clear the in-zone fault. Similarly, when the calculated pole selection parameter is less than the set value of the pole selection parameter, it is a negative pole grounding fault. Therefore, the circuit breaker disconnects the negative pole line to clear the in-zone fault. If it is determined to be a bipolar short-circuit fault, the circuit breaker disconnects the positive and negative pole lines to clear the in-zone fault.

[0114] The following uses a specific example to perform simulation verification on the line fault determination method provided by this application. As Figure 3 shown in the figure is a schematic diagram of a ±500 kV new energy transmission system via a flexible DC link built on PSCAD / EMTDC. Among them, the rectifier side adopts constant DC voltage control, and the inverter side adopts constant active power control; the length of the DC line is 500 km; the overhead line adopts a frequency-variable parameter model; the inductance value of the current-limiting reactor Lb = 100 mH; the protection sampling frequency is 10 kHz, that is, Ts = 100 μs.

[0115] As Figure 4 shown in the figure are the first voltage value on the rectifier side in the L mode, the second voltage value on the inverter side in the L mode, and the calculated value of its Metric coefficient when a fault occurs at different positions within the zone. As Figure 5 shown in the figure are the first voltage value, the second voltage value, and the calculated value of its Metric coefficient when a fault occurs at different positions outside the zone in this example. The simulation curves at different fault positions are all based on the Figure 3 built PSCAD / EMTDC simulation model. When a fault occurs at different positions, the dynamic time window lengths determined by wavelet transform modulus maxima are different. The L-mode voltages under different time window lengths have obvious differences between internal and external faults: during internal faults, they are similar and have small differences; during external faults, they are dissimilar and have large differences. Therefore, based on the line fault determination method provided by the embodiments of this application, the fault situation of the transmission line can be effectively judged, and a safe, reliable, and fast pilot protection method can be formed.

[0116] Specifically, as shown in Table 1 below, faults with different fault positions, different transition resistances, and different fault types are set for the new energy transmission system via a flexible DC link in the Figure 3 . In addition, the fault distances in Table 1 all refer to the distances from the fault point to the rectifier side:

[0117] Table 1

[0118]

[0119]

[0120]

[0121] It can be seen from Table 1 that the line fault determination method provided by this application can reliably identify internal and external faults, and also has high sensitivity to high-resistance faults.

[0122] In summary, the embodiments of this application utilize the sampled values of the L-mode voltages on both sides of the line within a time window after a fault, and calculate the sampled values based on the Metric coefficient. Compared with traditional current differential protection, this method can quickly and reliably identify internal and external faults, and also has a certain sensitivity to high-resistance faults.

[0123] Figure 6 The following is a schematic structural diagram of a line fault determination device in an embodiment of the present disclosure. As Figure 6 shown, the line fault determination device 60 provided in the embodiment of the present disclosure mainly includes: a voltage value extraction module 61, a Metric coefficient calculation module 62, and a fault range determination module 63.

[0124] Among them, the voltage value extraction module 61 is configured to extract a first voltage value and a second voltage value corresponding to each sampling moment within a preset time window when it is determined that a fault occurs in the line to be protected; the Metric coefficient calculation module 62 is configured to determine a metric standard Metric coefficient based on the first voltage value and the second voltage value; the fault range determination module 63 is configured to determine the fault location of the line to be protected based on the Metric coefficient and the protection setting value.

[0125] The embodiment of the present disclosure provides a line fault determination device, which is used to execute the following process: when it is determined that a fault occurs in the line to be protected, extract a first voltage value and a second voltage value corresponding to each sampling moment within a preset time window; determine a metric standard Metric coefficient based on the first voltage value and the second voltage value; determine the fault location of the line to be protected based on the Metric coefficient and the protection setting value. By using the voltage values on both sides of the line within a time window after the fault and calculating the voltage values based on the proposed Metric coefficient, and determining the fault range based on the Metric coefficient, compared with the traditional current differential protection, it can quickly and reliably identify internal and external faults, and also has a certain sensitivity to high-resistance faults, improving the speed of the existing pilot protection and meeting the four requirements of relay protection.

[0126] In a possible implementation manner, it further includes: a voltage value calculation module, configured to, for each sampling moment, obtain a first positive pole voltage value and a first negative pole voltage value of the line to be protected at the rectifier side; obtain a second positive pole voltage value and a second negative pole voltage value of the line to be protected at the inverter side; calculate a first voltage value based on the first positive pole voltage value, the first negative pole voltage value, and the L-mode voltage formula; calculate a second voltage value based on the second positive pole voltage value, the second negative pole voltage value, and the L-mode voltage formula.

[0127] In a possible implementation manner, the L-mode voltage mode is:

[0128]

[0129] where V L is the voltage value of the DC transmission line in the L mode, V po is the measured positive pole voltage value, V Npo is the rated positive pole voltage value, Vne To measure the negative voltage value, V Nne is the rated negative voltage value.

[0130] In a possible implementation, it further includes: a fault discrimination module, configured to obtain the third voltage value of the line to be protected at N sampling moments; calculate the composite voltage value at the current sampling moment based on the third voltage values at the N sampling moments, where the N sampling moments include the current sampling moment; and determine that a fault has occurred in the line to be protected when the composite voltage value is greater than the composite voltage setting value.

[0131] In a possible implementation, the composite voltage value at the current sampling moment is calculated by the following formula:

[0132]

[0133] where R u (k) is the composite voltage value at the current sampling moment, V(k - 1) is the third voltage value at the (k - 1)-th sampling moment, V(k - 2) is the third voltage value at the (k - 2)-th sampling moment, V(k) is the voltage sampling value at the current sampling moment, V(k + 1) is the third voltage value at the (k + 1)-th sampling moment, and V(k + 2) is the third voltage value at the (k + 2)-th sampling moment.

[0134] In a possible implementation, the preset time window is the time interval between the first moment and the second moment, where the first moment is the moment when it is determined that a fault has occurred in the line to be protected, and the second moment is the earliest arrival moment of the second voltage backward traveling wave after the protection start is calibrated using the wavelet transform modulus maximum.

[0135] In a possible implementation, the Metric coefficient is calculated by the following formula:

[0136]

[0137] where k is the k-th sampling moment, a k is the first voltage value at the k-th sampling moment, b k is the second voltage value at the k-th sampling moment, Metric(a k ,a k ) is the Metric coefficient at the k-th sampling moment, a i is the first voltage value at the i-th sampling moment, b i is the second voltage value at the i-th sampling moment, where 0 < i < n and n is the number of samplings within the preset time window.

[0138] In a possible implementation manner, the fault range determination module 63 is specifically configured to determine that an in-zone fault occurs on the line to be protected if the Metric coefficient is greater than the protection setting value; and determine that an out-of-zone fault occurs on the line to be protected if the Metric coefficient is less than the protection setting value.

[0139] In a possible implementation manner, it further includes: a fault type determination module, configured to calculate a pole selection parameter based on the positive voltage and the negative voltage of the line to be protected; and determine the fault type of the system to be protected based on the relationship between the pole selection parameter and the pole selection parameter setting value.

[0140] In a possible implementation manner, the pole selection parameter is determined by the sum value of the third ratios at multiple sampling moments, where the third ratio is the ratio of the absolute value of the positive voltage to the absolute value of the negative voltage.

[0141] In a possible implementation manner, the fault type determination module is specifically configured to determine that the fault type of the system to be protected is a positive pole grounding fault if the pole selection parameter is greater than the pole selection parameter setting value; determine that the fault type of the system to be protected is a negative pole grounding fault if the pole selection parameter is less than the reciprocal of the pole selection parameter setting value; and determine that the fault type of the system to be protected is a bipolar short circuit fault if the pole selection parameter is greater than the reciprocal of the pole selection parameter setting value and less than the pole selection parameter setting value.

[0142] The line fault determination device provided by the embodiments of the present application can execute the line fault determination method provided by any embodiment of the present application, and has corresponding functional modules and beneficial effects for executing the method.

[0143] Figure 7 It is a schematic structural diagram of an electronic device provided in this embodiment. The electronic device may include a line fault determination device, such as Figure 7 shown. The electronic device 700 includes a processor 710, a memory 720, an input device 730, and an output device 740; the number of processors 710 in the electronic device may be one or more, Figure 7 taking one processor 710 as an example; the processor 710, the memory 720, the input device 730, and the output device 740 in the electronic device may be connected through a bus or other means, Figure 7 taking the connection through the bus as an example.

[0144] The memory 720, being a computer-readable storage medium, can be used to store software programs, computer-executable programs, and modules, such as the program instructions / modules corresponding to the data transmission method in the embodiments of the present invention. The processor 710 executes various functional applications and data processing of the electronic device by running the software programs, instructions, and modules stored in the memory 720, that is, implements the line fault determination method provided by the embodiments of the present invention.

[0145] The memory 720 may mainly include a program storage area and a data storage area. Among them, the program storage area can store an operating system and application programs required for at least one function; the data storage area can store data created according to the use of the terminal, etc. In addition, the memory 720 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage devices. In some instances, the memory 720 may further include a memory remotely set relative to the processor 710, and these remote memories can be connected to the electronic device through a network. Examples of the above network include but are not limited to the Internet, enterprise intranets, local area networks, mobile communication networks, and combinations thereof.

[0146] The input device 730 can be used to receive input digital or character information, and generate key signal inputs related to the user settings and function controls of the electronic device, and may include a keyboard, a mouse, etc. The output device 740 may include a display device such as a display screen.

[0147] This embodiment also provides a storage medium containing computer-executable instructions, and the computer-executable instructions are used to implement the line fault determination method provided by the embodiments of the present invention when executed by a computer processor.

[0148] Of course, for a storage medium containing computer-executable instructions provided by the embodiments of the present invention, the computer-executable instructions are not limited to the method operations as described above, and can also execute the related operations in the line fault determination method provided by any embodiment of the present invention.

[0149] Through the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software and necessary general hardware. Of course, it can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such an understanding, the technical solution of the present invention, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a floppy disk, a read-only memory (ROM), a random access memory (RAM), a flash memory (FLASH), a hard disk, or an optical disc of a computer, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0150] It should be noted that in the embodiments of the above search device, the various units and modules included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be realized; in addition, the specific names of the functional units are only for the convenience of mutual distinction and do not limit the protection scope of the present invention.

[0151] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0152] The above are only the specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments described herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A line fault determination method, characterized in that: The method comprises: In the case of determining that a fault occurs in the line to be protected, extracting the first voltage value and the second voltage value corresponding to each sampling moment in the preset time window; extracting the first voltage value and the second voltage value corresponding to each sampling moment, including: for each sampling moment, obtaining the first positive pole voltage value and the first negative pole voltage value of the line to be protected on the rectifier side; obtaining the second positive pole voltage value and the second negative pole voltage value of the line to be protected on the inverter side; calculating the first voltage value based on the first positive pole voltage value, the first negative pole voltage value and the L-mode voltage formula; calculating the second voltage value based on the second positive pole voltage value, the second negative pole voltage value and the L-mode voltage formula; wherein the L-mode voltage formula is: Among them, V L is the voltage value of the DC transmission line in L mode, V po To measure the positive voltage, V Npo is the rated positive voltage, V ne To measure the negative voltage, V Nne is the rated negative voltage value; A metric coefficient is determined based on the first voltage value and the second voltage value; wherein the metric coefficient is calculated by the following formula: where k is the k-th sampling moment, a k is the first voltage value at the k-th sampling moment, b k is the second voltage value at the k-th sampling moment, Metric(a k , b k ) is the Metric coefficient at the k-th sampling moment, a i is the first voltage value at the i-th sampling moment, b i is the second voltage value at the i-th sampling moment, where 0 < i < n and n is the number of samplings within a preset time window; The fault location of the line to be protected is determined based on the Metric coefficient and the protection setting value.

2. The method according to claim 1, characterized in that The step of determining that a fault occurs on the line to be protected includes: Acquire a third voltage value of the line to be protected at N sampling moments; Calculating a composite voltage value at a current sampling moment based on the third voltage values ​​at the N sampling moments, wherein the N sampling moments include the current sampling moment; When the composite voltage value is greater than the composite voltage setting value, it is determined that a fault occurs in the line to be protected.

3. The method according to claim 2, characterized in that The composite voltage value at the current sampling moment is calculated by the following formula: Among them, R u V(k) is the composite voltage value at the current sampling moment, V(k-1) is the third voltage value at the k-1th sampling moment, V(k-2) is the third voltage value at the k-2th sampling moment, V(k) is the voltage sampling value at the current sampling moment, V(k+1) is the third voltage value at the k+1th sampling moment, and V(k+2) is the third voltage value at the k+2th sampling moment.

4. The method according to claim 1, characterized in that: The preset time window is the time interval between the first moment and the second moment, wherein the first moment is the moment when the fault of the line to be protected is determined, and the second moment is the earliest arrival moment of the second voltage reverse wave after the protection is started by calibrating the wavelet transform modulus maximum.

5. The method according to claim 1, characterized in that The determining the fault location of the line to be protected based on the Metric coefficient and the protection setting value includes: If the Metric coefficient is greater than the protection setting value, it is determined that an in-zone fault occurs on the line to be protected; If the Metric coefficient is less than the protection setting value, it is determined that an out-of-zone fault occurs on the line to be protected.

6. The method according to any one of claims 1 to 5, characterized in that: Also includes: Calculating a pole selection parameter based on the positive pole voltage and the negative pole voltage of the line to be protected; Based on the relationship between the pole selection parameter and the pole selection parameter setting value, the fault type of the system to be protected is determined.

7. The method according to claim 6, characterized in that The pole selection parameter is determined by the sum of third ratios at multiple sampling moments, wherein the third ratio is the ratio of the absolute value of the positive pole voltage to the absolute value of the negative pole voltage.

8. The method according to claim 6, characterized in that The determining the fault type of the system to be protected based on the relationship between the pole selection parameter and the pole selection parameter setting value includes: If the pole selection parameter is greater than the pole selection parameter setting value, determining that the fault type of the system to be protected is a positive pole grounding fault; If the pole selection parameter is less than the inverse of the pole selection parameter setting value, determining that the fault type of the system to be protected is a negative pole grounding fault; If the pole selection parameter is greater than the inverse of the pole selection parameter setting value, and the pole selection parameter is less than the pole selection parameter setting value, it is determined that the fault type of the system to be protected is a bipolar short circuit fault.

9. A line fault determination device, characterized in that: The device comprises: A voltage value extraction module is used to extract the first voltage value and the second voltage value corresponding to each sampling moment within a preset time window when it is determined that a fault occurs in the line to be protected; extracting the first voltage value and the second voltage value corresponding to each sampling moment includes: for each sampling moment, obtaining the first positive pole voltage value and the first negative pole voltage value of the line to be protected on the rectifier side; obtaining the second positive pole voltage value and the second negative pole voltage value of the line to be protected on the inverter side; calculating the first voltage value based on the first positive pole voltage value, the first negative pole voltage value and the L-mode voltage formula; calculating the second voltage value based on the second positive pole voltage value, the second negative pole voltage value and the L-mode voltage formula; wherein the L-mode voltage formula is: Among them, V L is the voltage value of the DC transmission line in L mode, V po To measure the positive voltage, V Npo is the rated positive voltage, V ne To measure the negative voltage, V Nne is the rated negative voltage value; The metric coefficient calculation module is used to determine the metric coefficient based on the first voltage value and the second voltage value; wherein the metric coefficient is calculated by the following formula: where k is the k-th sampling moment, a k is the first voltage value at the k-th sampling moment, b k is the second voltage value at the k-th sampling moment, Metric(a k , b k ) is the Metric coefficient at the k-th sampling moment, a i is the first voltage value at the i-th sampling moment, b i is the second voltage value at the i-th sampling moment, where 0 < i < n and n is the number of samplings within a preset time window; A fault range determination module is used to determine the fault location of the line to be protected based on the Metric coefficient and the protection setting value.

10. An electronic device, characterized in that: The electronic device comprises: one or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the line fault determination method according to any one of claims 1 to 8.

11. A storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the line fault determination method according to any one of claims 1 to 8 is implemented.

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