Ground fault detection protection method, system and device

Abstract

The invention relates to the technical field of power system detection and protection, and discloses a ground fault detection and protection method, system and device. The method comprises the following steps: according to a sampling frequency fT, respectively collecting currents of a head end and a tail end of the DC filter to obtain a head end current sequence and a tail end current sequence; according to the head end current sequence and the tail end current sequence, an absolute value obtained by differencing the head end current and the tail end current collected at the same moment is divided by a set coefficient C to obtain a point-line distance D; according to the time window length T, accumulating the point-line distances D calculated by the corresponding head end current and tail end current to obtain the sum Ds of the point-line distances; and determining the fault type according to the sum Ds of the point-line distances and the setting value Dset. According to the method, the fault of the power transmission line can be monitored in real time by collecting the currents at the head end and the tail end of the direct current filter, when the fault occurs, the currents at the head end and the tail end of the direct current filter synchronously change, the sum Ds of the point-line distances obtained through calculation is matched and compared with the setting value Dset, and the fault type can be rapidly judged; the efficiency and accuracy of fault type judgment are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system detection and protection, and in particular to a ground fault detection and protection method, system and device. Background Art

[0002] The high-voltage direct current transmission system has the advantages of large transmission capacity, long transmission distance, low loss, and flexible control. It can effectively realize the transmission of a large amount of new energy across multiple regions. The DC filter can effectively filter out characteristic harmonics and "escort" the safe and stable operation of the new power system. In the process of converting AC to DC, based on the grid-commutated converter (LCC), rich characteristic harmonics (600Hz, 1200Hz, 1800Hz, etc.) will inevitably be generated and injected into the DC line. Characteristic harmonics can cause serious harm to the power system: such as causing communication interference, heating of DC-side power equipment, reduced power quality, and malfunction of DC transmission line protection.

[0003] When a ground fault occurs in a DC filter, the filtering effect of the DC filter may be affected at the least, or it may cause overvoltage or overcurrent, thereby damaging the DC filter, and even cause the high-voltage DC transmission system to shut down, resulting in huge energy and economic losses.

[0004] At present, DC filters usually use current differential protection to identify various types of ground faults. However, in actual operation, when a high-voltage capacitor has a high-resistance ground fault, the differential protection has problems such as insufficient reliability and poor sensitivity. With the continuous improvement of the transmission capacity of new energy, high-voltage DC filter ground fault protection with excellent performance is becoming increasingly important to ensure the safe and stable operation of the power system. Summary of the invention

[0005] The present invention provides a ground fault detection and protection method, system and device, aiming to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a ground fault detection and protection method, system and device, which can effectively improve the efficiency, accuracy and reliability of judging the fault type.

[0006] In a first aspect, the present invention provides a ground fault detection and protection method, which is applied to a high voltage DC transmission line equipped with a DC filter, comprising the following steps:

[0007] According to the sampling frequency f T , respectively collecting the current at the head end and the tail end of the DC filter to obtain a head end current sequence and a tail end current sequence;

[0008] According to the head-end current sequence and the tail-end current sequence, the absolute value of the difference between the head-end current and the tail-end current collected at the same time is calculated and then divided by the set coefficient C to obtain the point-line distance D;

[0009] According to the time window length T, the point-to-line distance D calculated by the corresponding head-end current and tail-end current is accumulated to obtain the sum of the point-to-line distances D s ;

[0010] According to the sum of the distances between points and lines D s With the setting value D set to determine the type of fault.

[0011] According to some embodiments of the present invention, the method further includes the following steps: when it is determined that the fault type is a DC filter grounding fault, executing a protection action.

[0012] According to some embodiments of the present invention, the sum of the point-to-line distances D s With the setting value D set The step of determining the size of the fault type includes the following steps:

[0013] Get the set value D set ;

[0014] Determine the sum of the distances between points and lines D s With the setting value D set The size of the point-line distance D s Greater than the set value D set , it is determined to be a DC filter grounding fault; when the sum of the point-line distance D s Less than or equal to the set value D set , it is determined to be a non-DC filter area fault.

[0015] According to some embodiments of the present invention, the setting value D set For: D set =0.12*f T *T(3).

[0016] According to some embodiments of the present invention, the sampling frequency f T It is 2000~100000Hz, and the time window length T is 0.001~0.020s.

[0017] According to some embodiments of the present invention, the first-end current sequence is: i H ={i H (1),i H (2),…,i H (j),…,i H (N)}; the tail current sequence is: i L ={i L (1),i L (2),…,i L (j),…,i L(N)}; the unit of current is ampere, j is an integer, j∈[1,N], and N is the total number of sampling points.

[0018] According to some embodiments of the present invention, the point-to-line distance D and the sum of the point-to-line distance D s They are calculated by the following formulas:

[0019]

[0020] Among them, k and z are integers, k∈[z,z+N T -1], z∈[1,N],N T is the total number of sampling points within the time window length T, i H (z) is the first sampling head current within the time window length T, i L (z) is the tail current of the first sample within the time window length T.

[0021] According to some embodiments of the present invention, the coefficient is set d is the saturation correction coefficient, d = 1 or

[0022]

[0023] In a second aspect, the present invention provides a ground fault detection and protection system, which is applied to a high voltage DC transmission line equipped with a DC filter, comprising:

[0024] The parameter acquisition module is used to obtain the sampling frequency f T , respectively collecting the current at the head end and the tail end of the DC filter to obtain a head end current sequence and a tail end current sequence;

[0025] A first calculation module is used to calculate the absolute value of the difference between the head-end current and the tail-end current collected at the same time according to the head-end current sequence and the tail-end current sequence, and then divide it by a set coefficient C to obtain a point-line distance D;

[0026] The second calculation module is used to accumulate the point-to-line distance D calculated by the corresponding head-end current and tail-end current according to the time window length T to obtain the sum of the point-to-line distances D s ;

[0027] The third calculation module is used to calculate the sum of the point-line distance D s With the setting value D set to determine the type of fault.

[0028] In a third aspect, the present invention provides a computer device, comprising a memory and a processor, wherein the processor implements the above-mentioned ground fault detection and protection method when executing a computer program stored in the memory.

[0029] The beneficial effects of the present invention are as follows: by collecting the current at both ends of the DC filter, the fault of the transmission line can be monitored in real time. When a fault occurs, the current at both ends of the DC filter will change synchronously, and the sum of the point-line distance D calculated by the calculation s and with the setting value D set By comparison, the fault type can be quickly determined, effectively improving the efficiency and accuracy of determining the fault type; in addition, the method of the present invention not only has a low sampling frequency, but also the adopted protection device hardware is easy to implement. Compared with the existing ground fault detection method, it not only simplifies the structure, but also effectively reduces the amount of protection calculations and shortens the fault type determination time, and has the characteristics of high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of the steps of the ground fault detection and protection method of the present invention;

[0031] Figure 2 Another step flow chart of the ground fault detection and protection method of the present invention;

[0032] Figure 3 A schematic diagram of the structure of a triple-tuned DC filter in a high-voltage DC power transmission system used in the present invention;

[0033] Figure 4 The current trajectory distribution diagram of the DC filter used in the present invention at both ends during normal operation;

[0034] Figure 5 The high voltage capacitor C of the DC filter used in the present invention 1 Ground fault occurs in the area 1 The current trajectory distribution diagram at both ends of the time;

[0035] Figure 6 The high voltage capacitor C of the DC filter used in the present invention 1 With inductance L 1 A ground fault occurs between 2 The current trajectory distribution diagram at both ends of the time;

[0036] Figure 7 The inductance L of the DC filter used in the present invention 1 With capacitor C 2 A ground fault occurs between 3 The current trajectory distribution diagram at both ends of the time;

[0037] Figure 8 The capacitor C of the DC filter used in the present invention 2 With inductance L 3 A ground fault occurs between 4The current trajectory distribution diagram at both ends of the time;

[0038] Fig. 9 It is a structural schematic diagram of a ground fault detection and protection system of the present invention;

[0039] Fig.10 The figure is a schematic diagram of the structure of a computer device of the present invention.

[0040] Reference numerals: DC filter 110 , high voltage DC transmission line 120 , parameter acquisition module 210 , first calculation module 220 , second calculation module 230 , memory 320 , processor 310 . DETAILED DESCRIPTION

[0041] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in combination with the embodiments and drawings to fully understand the purpose, scheme and effect of the present invention.

[0042] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to another feature, or it can be indirectly fixed or connected to another feature. It should be noted that, unless otherwise specified, when a feature is referred to as being "electrically connected" or "electrically connected" to another feature, the two features can be directly connected through pins, or connected through cables, or connected by wireless transmission. The specific electrical connection method belongs to the general method of those skilled in the art, and those skilled in the art can realize the connection as needed. The singular forms of "a", "said" and "the" used herein are also intended to include the majority form, unless the context clearly indicates other meanings. In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments, not for limiting the present invention. The term "and / or" used herein includes any combination of one or more related listed items.

[0043] It should be understood that, although the term first, second, third etc. may be adopted to describe various elements in the present disclosure, these elements should not be limited to these terms. These terms are only used to distinguish the same type of elements from each other. For example, without departing from the scope of the present disclosure, the first element may also be referred to as the second element, and similarly, the second element may also be referred to as the first element. The use of any and all examples or exemplary language ("for example", "such as" etc.) provided herein is only intended to better illustrate embodiments of the present invention, and unless otherwise required, the scope of the present invention will not be limited.

[0044] Reference Figure 1In a first aspect, the present invention provides a ground fault detection and protection method, which is applied to a high voltage DC transmission line 120 equipped with a DC filter 110, and comprises the following steps:

[0045] Step S100: According to the sampling frequency f T , respectively collect the current at the head end and the tail end of the DC filter 110 to obtain the head end current sequence i H and the tail current sequence i L ;

[0046] In the high-voltage direct current transmission system, the head end and the tail end of the direct current filter 110 are respectively equipped with current collection devices, such as current transformers. By using the corresponding current transformers, according to the set sampling frequency, the currents at the head and tail ends of the direct current filter 110 can be collected in real time, and then the head end current sequence i can be obtained. H ={i H (1),i H (2),…,i H (j),…,i H (N)} and the tail current sequence i L ={i L (1),i L (2),…,i L (j),…,i L (N)}, where the current unit of the collected data is ampere, j is an integer, j∈[1,N], and N is the total number of sampling points;

[0047] Step S200: According to the first-end current sequence i H and the tail current sequence i L , the absolute value of the difference between the head-end current and the tail-end current collected at the same time is calculated and then divided by the set coefficient C to obtain the point-line distance D;

[0048] The system collects the first-end current sequence i H ={i H (1),i H (2),…,i H (j),…,i H (N)} and the tail current sequence i L ={i L (1),i L (2),…,i L (j),…,i L (N)}, the absolute value of the difference between the head-end current and the tail-end current collected at the corresponding moment is divided by the set coefficient C to obtain the point-line distance D. According to step S200, it can be obtained that the point-line distance D is calculated by the following formula:

[0049]

[0050] That is, the point-line distance corresponding to the first set of collected sample points Then the corresponding point-line distances are

[0051] Step S300: According to the time window length T, the point-to-line distance D calculated by the corresponding head-end current and tail-end current is accumulated to obtain the sum of the point-to-line distances D. s ;

[0052] According to the time window length T obtained by the system, the number of sampling points in the corresponding time can be determined. By accumulating the point-to-line distances calculated by the head-end current and tail-end current collected at the corresponding moment, the sum of the point-to-line distances D in the corresponding time window length T can be obtained. s According to step S300, it can be obtained that within the corresponding time window length T, the sum of the point-line distances D s It is calculated by the following formula:

[0053]

[0054] Among them, k and z are integers, k∈[z,z+N T -1], z∈[1,N],N T is the total number of sampling points within the time window length T, i H (z) is the first sampling head current within the time window length T, i L (z) is the tail current of the first sample within the time window length T;

[0055] Step S400: according to the sum of the point-line distance D s With the setting value D set size to determine the fault type;

[0056] By comparing the sum of the point-line distances D in the corresponding time window length T s With the setting value D set By looking at the size of , we can know whether a fault occurs within the corresponding time window length T, and we can determine the type of fault that occurs. After determining the type of fault, the system can decide whether to perform a protection action.

[0057] In addition, it should be noted that step S100, step S200, step S300 and step S400 of the present invention may be repeatedly executed in real time, so as to monitor the high voltage direct current transmission system in real time. When the corresponding fault type in step S400 is met, the protection action is executed to ensure the stability of the system. Similarly, when executing step S200, a step may be added:

[0058] Step S210, calculate the absolute value of the difference between the head-end current and the tail-end current collected at the same time, and compare the absolute value of the difference with the set comparison value. When the absolute value of the difference is greater than or equal to the set range, continue to execute steps S300 and S400, otherwise, directly continue to execute step S200,

[0059] In this way, the efficiency of system monitoring can be further improved, and the load on the system can be further reduced, thereby further improving reliability.

[0060] Reference Figure 2 In some embodiments of the present invention, the following steps are also included:

[0061] Step S500: When it is determined that the fault type is a DC filter grounding fault, a protection action is executed.

[0062] Similarly, it can be known that step S100, step S200, step S300, step S400 and step S500 of the present invention can be repeatedly executed in real time, so as to monitor the high voltage direct current transmission system in real time. When the corresponding fault type in step S400 is met, step S500 is executed, that is, the protection action is executed to ensure the stability of the system. Similarly, when executing step S200, a step can be added:

[0063] Step S210, calculate the absolute value of the difference between the head-end current and the tail-end current collected at the same time, and compare the absolute value of the difference with the set comparison value. When the absolute value of the difference is greater than or equal to the set range, continue to execute steps S300, S400 and S500, otherwise, directly continue to execute step S200.

[0064] In this way, the efficiency of system monitoring can be further improved, and the load on the system can be further reduced, thereby further improving reliability.

[0065] In some embodiments of the present invention, step S400 includes the following steps:

[0066] Step S410: Obtaining the set value D set ;

[0067] Step S420: Determine the sum of the point-line distances D s With the setting value D set The size of the point-line distance D s Greater than the set value D set , it is determined to be a DC filter grounding fault; when the sum of the point-line distance D s Less than or equal to the set value D set , then it is determined to be the non-DC filter area fault setting value D set.

[0068] In some embodiments of the present invention, the setting value D set for:

[0069] D set =0.12*f T *T (3).

[0070] According to the real-time set sampling frequency f s and time window length T to set value D set By making real-time adjustments, the adaptability of the present invention can be improved, and the transmission lines in different situations can be adapted. At the same time, the accuracy of judging the type of transmission line fault can be improved to improve reliability. In addition, it can be known that the designer can directly input a fixed value as the setting value D in advance according to the actual situation of the transmission line and combined with experience. set When executing the above step S400, the present invention can directly make a judgment based on the set value.

[0071] In some embodiments of the present invention, the sampling frequency f T It is 2000~100000Hz, and the time window length T is 0.001~0.020s.

[0072] In some embodiments of the present invention, the first-end current sequence is: i H ={i H (1),i H (2),…,i H (j),…,i H (N)};

[0073] The tail current sequence is: i L ={i L (1),i L (2),…,i L (j),…,i L (N)};

[0074] The unit of current is ampere, j is an integer, j∈[1,N], and N is the total number of sampling points.

[0075] In some embodiments of the present invention, the point-to-line distance D and the sum of the point-to-line distance D s They are calculated by the following formulas:

[0076]

[0077] Among them, k and z are integers, k∈[z,z+N T -1], z∈[1,N],N T is the total number of sampling points within the time window length T, i H(z) is the first sampling head current within the time window length T, i L (z) is the tail current of the first sample within the time window length T.

[0078] In some embodiments of the present invention, the coefficient is set d is the saturation correction coefficient, d = 1 or

[0079]

[0080] Specifically, when a serious ground fault occurs in the high-voltage capacitor area of ​​the DC filter 110, the head-end current transformer will be saturated because the current value it measures is too large. When the saturation problem exists, the traditional current differential protection will malfunction. Therefore, when the saturation correction coefficient is When the fault detection accuracy is further improved, the reliability of fault type determination can be further improved.

[0081] The beneficial effects of the present invention are as follows: by collecting the current at both ends of the DC filter 110, the fault of the transmission line can be monitored in real time. When a fault occurs, the current at both ends of the DC filter 110 will change synchronously, and the sum of the point-line distance D calculated by the calculation will be s and with the setting value D set By comparison, the fault type can be quickly determined, effectively improving the efficiency and accuracy of determining the fault type; in addition, the method of the present invention not only has a low sampling frequency, but also the adopted protection device hardware is easy to implement. Compared with the existing ground fault detection method, it not only simplifies the structure, but also effectively reduces the amount of protection calculations and shortens the fault type determination time, and has the characteristics of high reliability.

[0082] The theoretical basis of the fault criterion proposed by the present invention is as follows:

[0083] Reference Figure 3 , is a schematic diagram of the structure of a three-tuned DC filter 110 applied to a high-voltage DC transmission system of the present invention, the rated voltage of the high-voltage DC transmission system is ±800kV, and the rated current is 4kA; 2 / 12 / 39 Parameters of the three-tuned DC filter 110: C 1 =1.05μF, L 1 =9.847mH, C 2 =3.286μF, L 2 =82.95mH, R 1 =3095Ω, C 3 =5.105μF, L 3 =11.745mH; T C1 、T C2The current transformers at the head and tail ends of the DC filter 110 are provided. In this example, the corresponding current transformers T C1 and current transformer T C2 The measured current i of the first end of the DC filter 110 is H and the tail current i L , f 1 、f 2 、f 3 and f 4 is the ground fault point set on the DC filter 110, f 5 It is a grounding fault point set on the high-voltage direct current transmission line 120 .

[0084] When the DC filter 110 is operating normally, according to Kirchhoff's current law, the head-end current i H With the tail current i L There is the following relationship: i H =i L ;

[0085] The tail current i L The sampling point is used as the x coordinate, and the first-end current i H The sampling point is taken as the y coordinate, and the current trajectory is the straight line y=x passing through the origin, such as Figure 4 Therefore, when the DC filter 110 operates normally, the point-to-line distance D calculated by formula (1) should be 0.

[0086] When a ground fault occurs in the DC filter 110, the fault current flows into the ground through the grounding point. According to Kirchhoff's current law, the head-end current i H With the tail current i L are no longer equal, that is, the point-to-line distance D calculated according to formula (1) is no longer 0. The current trajectory distribution at the ends of the DC filter 110 under different fault types is as follows: Figures 5 to 8 As shown, it can be known that it is consistent with the theoretical analysis. Therefore, there is a significant difference between the point-line distance characteristics when the DC filter 110 is operating normally and when it has a ground fault. The above characteristics can be used to construct a ground fault protection method applied to the DC filter 110.

[0087] Specifically, Figure 3 As a specific embodiment, in this example, the current sampling frequency f T =2000Hz, time window length T = 5ms, then the setting value D can be calculated by formula (3): set =1.2.

[0088] Specifically, for ease of explanation, in the embodiment of the present invention, a DC filter grounding fault is referred to as an intra-zone fault, and a non-DC filter area fault is referred to as an extra-zone fault.

[0089] Embodiment 1: The fault type is the high voltage capacitor C of the DC filter 110 1 Different types of ground faults occur.

[0090] Table 1 High voltage capacitor C of DC filter 110 1 Simulation results when different types of ground faults occur

[0091]

[0092] Table 1 shows the high voltage capacitor C of the DC filter 110 1 When different types of ground faults occur, the simulation results obtained by executing step S100, step S200, step S300, step S400 and step S500 in the present invention are as follows. In Table 1, α is the high voltage capacitor C 1 When a ground fault occurs in the upper arm, the fault point and the current transformer T C1 The capacitance between the bridge arm and the bridge arm accounts for the percentage of the total capacitance of the bridge arm; β is the high-voltage capacitor C 1 When a ground fault occurs in the lower bridge arm, the capacitance between the fault point and the top of the lower bridge arm accounts for a percentage of the total capacitance of the bridge arm.

[0093] It can be seen from Table 1 that when the high voltage capacitor C of the DC filter 110 1 When a ground fault occurs, the sum of the point-to-line distances D is S Both are greater than the set value D set (1.2), the ground fault protection criterion is met, and the fault type is determined to be a DC filter ground fault, that is, an intra-zone fault. The protection has the advantages of high reliability and is not affected by transition resistance.

[0094] Embodiment 2: The fault type is that the non-high voltage capacitor of the DC filter 110 has different types of grounding.

[0095] Table 2 Simulation results when different types of ground faults occur in the non-high voltage capacitor area of ​​DC filter 110

[0096]

[0097] Table 2 shows simulation results obtained by executing step S100, step S200, step S300, step S400 and step S500 in the present invention when different types of grounding faults occur in the non-high voltage capacitor of the DC filter 110.

[0098] It can be seen from Table 2 that when a ground fault occurs in the non-high voltage capacitor area of ​​the DC filter 110, the sum of the point-to-line distances D is S Both are greater than the set value D set(1.2), the ground fault protection criterion is met, and the fault type is determined to be a DC filter ground fault, that is, an intra-zone fault. The protection has the advantages of high reliability and is not affected by transition resistance.

[0099] Embodiment 3: The fault type is grounding faults occurring at different positions of the positive pole of the high-voltage direct current transmission line 120 .

[0100] Table 3 Ground faults at different locations of the positive pole of HVDC transmission line 120 5 Simulation results

[0101]

[0102] Table 3 shows the ground faults f occurring at different locations of the positive pole of the HVDC transmission line 120 5 When executing the simulation results obtained according to step S100, step S200, step S300, step S400 and step S500 in the present invention.

[0103] It can be seen from Table 3 that when a ground fault occurs at different positions of the positive pole of the high-voltage direct current transmission line 120, the sum of the point-to-line distances D is S They are all 0, which meets the ground fault protection criterion. The fault type is determined to be an out-of-zone fault, that is, a ground fault in the non-DC filter 110 area. The protection has the advantages of high reliability and is not affected by transition resistance.

[0104] Combining the simulation results of Table 1, Table 2 and Table 3, it can be seen that the present invention can correctly distinguish between DC filter grounding faults (in-zone faults) and non-DC filter regional faults (out-of-zone faults), has high reliability, fast judgment speed, low sampling frequency, and is not affected by the fault location and the transition resistance of the fault point.

[0105] It can be known that the present invention has the characteristics of strong resistance to transition resistance, and utilizes the full characteristic current at both ends of the DC filter 110 to realize the judgment of the DC filter grounding fault, with good protection selectivity and high reliability; and the sampling frequency is low, and only the current at the two ends needs to be sampled in real time, the structure is simple and easy to implement, so the reliability is high, and compared with the existing technology, the present invention does not need to extract single or combined information such as the amplitude, frequency, phase, etc. of the full characteristic current, which effectively reduces the amount of calculation of fault detection protection and shortens the fault judgment time, thereby effectively improving the efficiency and accuracy of fault detection.

[0106] Reference Fig. 9In a second aspect, the present invention provides a ground fault detection and protection system, which is applied to a high voltage DC transmission line 120 equipped with a DC filter 110 branch, and includes a parameter acquisition module 210, a first calculation module 220, a second calculation module 230, a third calculation module 240 and a fourth calculation module 250; the parameter acquisition module 210 calculates the ground fault according to the sampling frequency f T , respectively collect the current at the head end and the tail end of the DC filter 110 to obtain the head end current sequence i H and the tail current sequence i L The first calculation module 220 is used to calculate the current sequence i according to the first end H and the tail current sequence i L , the absolute value of the difference between the head-end current and the tail-end current collected at the same time is calculated and then divided by the set coefficient C to obtain the point-line distance D; the second calculation module 230 is used to accumulate the point-line distance D calculated by the corresponding head-end current and tail-end current according to the time window length T to obtain the sum of the point-line distances D s The third calculation module 240 is used to calculate the sum of the point-line distance D s With the setting value D set to determine the type of fault.

[0107] It can be known that the contents in the above-mentioned ground fault detection and protection method embodiments are all applicable to the present system embodiments, the functions specifically implemented by the embodiments of the present invention are the same as those in the above-mentioned ground fault detection and protection method embodiments, and the beneficial effects achieved are also the same as those achieved by the above-mentioned ground fault detection and protection method embodiments.

[0108] Reference Fig.10 In a third aspect, the present invention provides a computer device, including a memory 320 and a processor 310, wherein the processor 310 implements the above-mentioned ground fault detection and protection method when executing a computer program stored in the memory 320.

[0109] Similarly, the contents of the above-mentioned ground fault detection and protection method embodiment are applicable to the present device embodiment. The functions specifically implemented by the present device embodiment are the same as those of the above-mentioned method embodiment, and the beneficial effects achieved are also the same as those achieved by the above-mentioned ground fault detection and protection method embodiment.

[0110] It should be appreciated that the method steps in the embodiments of the present invention can be implemented or implemented by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer readable memory. The ground fault detection protection method can use standard programming techniques. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if necessary, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. In addition, for this purpose, the program can be run on a programmed dedicated integrated circuit.

[0111] Furthermore, the operations of the processes described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The processes described herein (or variations and / or combinations thereof) may be performed under the control of one or more computer systems configured with executable instructions, and may be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) that is executed collectively on one or more processors, by hardware, or a combination thereof. A computer program includes a plurality of instructions that may be executed by one or more processors.

[0112] Further, the method can be implemented in any type of computing platform that is operably connected to a suitable computer, including but not limited to a personal computer, a minicomputer, a mainframe, a workstation, a network or distributed computing environment, a separate or integrated computer platform, or in communication with a charged particle tool or other imaging device, etc. Various aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, an optical read and / or write storage medium, a RAM, a ROM, etc., so that it can be read by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the process described herein. In addition, the machine-readable code, or a portion thereof, can be transmitted via a wired or wireless network. When such media includes instructions or programs that implement the above steps in conjunction with a microprocessor or other data processor, the invention herein includes these and other different types of non-transitory computer devices. When programmed according to the methods and techniques of the present invention, the present invention can also include the computer itself.

[0113] The computer program can be applied to input data to perform the functions herein, thereby converting the input data to generate output data stored in a non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the present invention, the converted data represents physical and tangible objects, including specific visual depictions of physical and tangible objects produced on the display.

[0114] The above are only preferred embodiments of the present invention. The present invention is not limited to the above embodiments. As long as the technical effects of the present invention are achieved by the same means, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention. Within the scope of protection of the present invention, its technical solutions and / or implementation methods may have various modifications and changes.

Claims

1. A ground fault detection and protection method, applied to a high voltage DC transmission line equipped with a DC filter, characterized in that: The following steps are involved: According to the sampling frequency f T , respectively collecting the current at the head end and the tail end of the DC filter to obtain a head end current sequence and a tail end current sequence; According to the head-end current sequence and the tail-end current sequence, the absolute value of the difference between the head-end current and the tail-end current collected at the same time is calculated and then divided by the set coefficient C to obtain the point-line distance D; According to the time window length T, the point-to-line distance D calculated by the corresponding head-end current and tail-end current is accumulated to obtain the sum of the point-to-line distances D s ; According to the sum of the distances between points and lines D s With the setting value D set to determine the type of fault.

2. The ground fault detection and protection method according to claim 1, characterized in that: The following steps are also included: When it is determined that the fault type is a DC filter grounding fault, a protection action is performed.

3. The ground fault detection and protection method according to claim 1, characterized in that: The sum of the distances between points and lines D s With the setting value D set The size of the fault to determine the type of fault includes the following steps: Get the setting value D set ; Determine the sum of the distances between points and lines D s With the setting value D set The size of the point-line distance D s Greater than the set value D set , it is determined to be a DC filter grounding fault; when the sum of the point-line distance D s Less than or equal to the set value D set , it is determined to be a non-DC filter area fault.

4. The ground fault detection and protection method according to any one of claims 1 to 3 is characterized in that : Setting value D set for: D set =0.12*f T *T (3)。 5. The ground fault detection and protection method according to any one of claims 1 to 3, characterized in that: Sampling frequency f T It is 2000~100000Hz, and the time window length T is 0.001~0.020s.

6. The ground fault detection and protection method according to any one of claims 1 to 3, characterized in that: The first-end current sequence is: i H ={i H (1),i H (2),…,i H (j),…,i H (N)}; The tail current sequence is: L ={i L (1),i L (2),…,i L (j),…,i L (N)}; The unit of current is ampere, j is an integer, j∈[1,N], and N is the total number of sampling points.

7. The ground fault detection and protection method according to any one of claims 1 to 3, characterized in that: The distance between a point and a line D and the sum of the distance between a point and a line D s They are calculated by the following formulas: Among them, k and z are integers, k∈[z,z+N T -1], z∈[1,N],N T is the total number of sampling points within the time window length T, i H (z) is the first sampling head current within the time window length T, i L (z) is the tail current of the first sample within the time window length T.

8. The ground fault detection and protection method according to claim 7, characterized in that: Setting coefficient d is the saturation correction coefficient, d = 1 or 9. A ground fault detection and protection system, applied to a high voltage DC transmission line equipped with a DC filter, characterized in that: include: The parameter acquisition module is used to obtain the sampling frequency f T , respectively collecting the current at the head end and the tail end of the DC filter to obtain a head end current sequence and a tail end current sequence; A first calculation module is used to calculate the absolute value of the difference between the head-end current and the tail-end current collected at the same time according to the head-end current sequence and the tail-end current sequence, and then divide it by a set coefficient C to obtain a point-line distance D; The second calculation module is used to accumulate the point-to-line distance D calculated by the corresponding head-end current and tail-end current according to the time window length T to obtain the sum of the point-to-line distances D s ; The third calculation module is used to calculate the sum of the point-line distance D s With the setting value D set to determine the type of fault.

10. A computer device comprising a memory and a processor, characterized in that: When the processor executes the computer program stored in the memory, the ground fault detection and protection method according to any one of claims 1 to 8 is implemented.

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