Novel power distribution network single-phase earth fault line selection method and related device

Abstract

The embodiment of the invention relates to the field of power protection, and provides a novel power distribution network single-phase earth fault line selection method and a related device, and the method comprises the steps: generating a current traveling wave, and transmitting the current traveling wave to each line in a power distribution network after the power distribution network breaks down; detecting three-phase voltage data after current traveling wave propagation is carried out on each line in the power distribution network; performing fault phase selection according to the three-phase voltage data of the bus in the power distribution network to obtain a fault phase selection result; if the fault phase selection result is a single-phase earth fault, line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line, and a line mode high-frequency instantaneous energy set is obtained; and the fault line in the power distribution network is determined according to the line mode high-frequency instantaneous energy set, the fault line can be determined according to the line mode high-frequency instantaneous energy, and the accuracy of determining the fault line is improved.

Description

Technical Field

[0001] The present application relates to the field of power protection technology, and in particular to a novel single-phase ground fault line selection method and related devices for a power distribution network. Background Art

[0002] As an important carrier of electric energy transmission, the distribution network is also a key link for power users. The stability and safety of its operation are most perceived by the society. Due to the large scale of the distribution network and its distribution in various complex cultural and geographical environments, the equipment and lines are easily affected by the environment, weather and various human factors, resulting in frequent distribution network failures. With the development of social economy, the distribution network is evolving more and more in the direction of multiple branches to meet the diversified power needs of a wider area. This can better meet the needs of users under the new market situation and improve the economy of the power system. However, the complexity of the topological structure of the multi-branch distribution network means that if a failure is not handled in time, it may more seriously threaten the reliable operation of the power system.

[0003] In the actual operation of the distribution network, single-phase grounding faults are particularly common, accounting for more than half. Protected by the neutral point non-effective grounding device of the distribution network, the system can continue to operate after this type of fault occurs, and will not immediately cause the system to lose power. However, the fault may further deteriorate over a long period of operation, causing more serious short-circuit problems, and even endangering the system insulation, posing a threat to the safe and stable operation of the power system. Especially in urban distribution networks, with the large-scale application of cables and the increase in cable hybrid lines, the system lines are growing rapidly, and the fault capacitance current is increasing, making fault handling more complicated and difficult.

[0004] Therefore, it is particularly important to further improve the accuracy of fault line selection in the distribution network to address this problem. Rapidly and accurately locating and isolating the fault line can not only shorten the power outage time, reduce the scope of power outage, and improve power supply reliability, but also avoid serious accidents caused by the expansion of faults and ensure the safe and stable operation of the power system.

[0005] Traditional line selection methods often use zero-sequence steady-state quantities to select fault lines. The system grounding mode and operation mode have a great influence and interference on the line selection results, and lack flexibility in the face of the flexible grounding power system that is being widely used. In comparison, the transient traveling wave line selection method is not easily affected by the above problems. However, the existing traveling wave line selection method is easily affected by high-resistance grounding, traveling wave total reflection, noise, traveling wave head calibration accuracy, line parameter changes, network topology and other poor grounding conditions, and there are technical problems such as low line selection accuracy. Summary of the invention

[0006] The embodiment of the present application provides a novel single-phase grounding fault line selection method and related device for a distribution network, which can calculate the line mode high-frequency instantaneous energy of each line based on the three-phase voltage data after current traveling wave propagation in each line, and determine the faulty line based on the line mode high-frequency instantaneous energy, thereby improving the accuracy of faulty line determination.

[0007] A first aspect of an embodiment of the present application provides a novel single-phase ground fault line selection method for a power distribution network, the method comprising:

[0008] After a fault occurs in the distribution network, a current traveling wave is generated and propagates to each line in the distribution network;

[0009] Detecting three-phase voltage data after current traveling wave propagation in each line of the distribution network;

[0010] Perform fault phase selection according to the three-phase voltage data of the busbar in the distribution network to obtain the fault phase selection result;

[0011] If the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set;

[0012] A fault line in the distribution network is determined according to the line mode high frequency instantaneous energy set.

[0013] In this example, after a fault occurs in the distribution network, a current traveling wave is generated and propagated to each line in the distribution network; the three-phase voltage data of each line in the distribution network after the current traveling wave propagates is detected; the fault phase is selected according to the three-phase voltage data of the bus in the distribution network to obtain a fault phase selection result; if the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set; the fault line in the distribution network is determined according to the line mode high-frequency instantaneous energy set, so that the line mode high-frequency instantaneous energy of each line can be calculated according to the three-phase voltage data after the current traveling wave propagates in each line, and the faulty line is determined according to the line mode high-frequency instantaneous energy, thereby improving the accuracy of determining the faulty line.

[0014] In a possible implementation, the method of calculating the line mode high-frequency instantaneous energy corresponding to each line according to the three-phase voltage data of each line to obtain the line mode high-frequency instantaneous energy set includes:

[0015] The line mode high frequency instantaneous energy corresponding to each line is calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set:

[0016]

[0017] Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

[0018] In a possible implementation, determining a fault line in a distribution network according to the line mode high frequency instantaneous energy set includes:

[0019] Extracting the maximum line mode high frequency instantaneous energy from the line mode high frequency instantaneous energy set;

[0020] The line corresponding to the maximum line mode high frequency instantaneous energy is determined as a faulty line.

[0021] In a possible implementation, after a fault occurs in the distribution network, generating a current traveling wave to propagate to each line in the distribution network includes:

[0022] After a fault occurs in the distribution network, obtain the peak moment of the neutral point voltage;

[0023] At the peak moment of the neutral point voltage, a parallel resistor is connected to generate a current traveling wave through the parallel resistor and propagates to each line in the distribution network.

[0024] In a possible implementation, after determining the fault line in the distribution network according to the line mode high frequency instantaneous energy set, the method further includes:

[0025] Determining a fault point interval of the fault line;

[0026] The fault point interval is displayed.

[0027] A second aspect of an embodiment of the present application provides a novel single-phase ground fault line selection device for a power distribution network, the device comprising:

[0028] A generating unit, used to generate a current traveling wave and propagate it to each line in the distribution network after a fault occurs in the distribution network;

[0029] A detection unit, used to detect three-phase voltage data after current traveling wave propagation in each line in the distribution network;

[0030] A processing unit, used for performing fault phase selection according to three-phase voltage data of a busbar in a distribution network to obtain a fault phase selection result;

[0031] A calculation unit, for calculating the line mode high-frequency instantaneous energy corresponding to each line according to the three-phase voltage data of each line if the fault phase selection result is a single-phase grounding fault, and obtaining a line mode high-frequency instantaneous energy set;

[0032] A determination unit is provided for determining a fault line in the distribution network according to the line mode high frequency instantaneous energy set.

[0033] In a possible implementation, the computing unit is specifically configured to:

[0034] The line mode high frequency instantaneous energy corresponding to each line is calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set:

[0035]

[0036] Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

[0037] In a possible implementation manner, the determining unit is specifically configured to:

[0038] Extracting the maximum line mode high frequency instantaneous energy from the line mode high frequency instantaneous energy set;

[0039] The line corresponding to the maximum line mode high frequency instantaneous energy is determined as a faulty line.

[0040] In a possible implementation, the generating unit is specifically used for:

[0041] After a fault occurs in the distribution network, obtain the peak moment of the neutral point voltage;

[0042] At the peak moment of the neutral point voltage, a parallel resistor is connected to generate a current traveling wave through the parallel resistor and propagates to each line in the distribution network.

[0043] In a possible implementation, after determining the fault line in the distribution network according to the line mode high frequency instantaneous energy set, the device is further used to:

[0044] Determining a fault point interval of the fault line;

[0045] The fault point interval is displayed.

[0046] A third aspect of an embodiment of the present application provides a terminal, comprising a processor, an input device, an output device and a memory, wherein the processor, input device, output device and memory are interconnected, wherein the memory is used to store a computer program, the computer program comprises program instructions, and the processor is configured to call the program instructions to execute the step instructions in the first aspect of the embodiment of the present application.

[0047] The fourth aspect of the embodiments of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program for electronic data exchange, wherein the computer program enables a computer to execute part or all of the steps described in the first aspect of the embodiments of the present application.

[0048] A fifth aspect of the embodiments of the present application provides a computer program product, wherein the computer program product includes a non-transitory computer-readable storage medium storing a computer program, and the computer program is operable to cause a computer to execute some or all of the steps described in the first aspect of the embodiments of the present application. The computer program product may be a software installation package. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1A A schematic flow chart of a novel method for selecting a line for a single-phase ground fault in a power distribution network is provided for an embodiment of the present application;

[0051] Figure 1B A flowchart of a method for determining a business product is provided for an embodiment of the present application;

[0052] Figure 2 A schematic diagram of a 10kV distribution network model is provided for an embodiment of the present application;

[0053] Figure 3 A schematic diagram of a small resistance perturbation traveling wave transmission process is provided for an embodiment of the present application;

[0054] Figure 4 A schematic diagram for comparing zero-mode traveling waves and line-mode traveling waves of a faulty line and a normal line is provided for an embodiment of the present application;

[0055] Figure 5 A schematic diagram of the reflection and refraction process of a traveling wave through impedance grounding is provided for an embodiment of the present application;

[0056] Figure 6 A wavelet time-frequency diagram is provided for an embodiment of the present application;

[0057] Figure 7 A schematic diagram of the structure of a terminal provided in an embodiment of the present application;

[0058] Figure 8A structural schematic diagram of a business product determination device is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0060] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0061] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0062] See also Figure 1A , Figure 1A The present invention provides a flow chart of a novel method for selecting a line for a single-phase ground fault in a power distribution network. Figure 1A As shown in the figure, the new distribution network single-phase grounding fault line selection method includes:

[0063] 101. When a fault occurs in the distribution network, a current traveling wave is generated and propagates to each line in the distribution network.

[0064] Specifically, after a fault occurs in the distribution network, the peak moment of the neutral point voltage is obtained, and then a parallel resistor is connected at the peak moment of the neutral point voltage to generate a current traveling wave through the parallel resistor to propagate to each line in the distribution network. The distribution network includes a busbar and multiple lines.

[0065] 102. Detect three-phase voltage data after current traveling wave propagation in each line in the distribution network.

[0066] The three-phase voltage data can be obtained by performing three-phase voltage detection with a voltage detector set on each line. Specifically, the three-phase voltage data can be obtained by performing detection at the head end of the feeder of each line. Of course, current detection can also be performed to obtain three-phase current data.

[0067] 103. Perform fault phase selection based on the three-phase voltage data of the busbar in the distribution network to obtain a fault phase selection result.

[0068] When performing fault phase selection, a general fault phase selection method may be used to process the fault phase selection result. According to the fault phase selection result, when a phase a or b phase fault occurs, mode 1 or mode 2 current may be selected as a research object; when a phase C fault occurs, mode 2 current may be selected as a research object.

[0069] 104. If the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set.

[0070] The line mode high frequency instantaneous energy corresponding to each line can be calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set:

[0071]

[0072] Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

[0073] 105. Determine a fault line in the distribution network according to the line mode high frequency instantaneous energy set.

[0074] Specifically, the maximum line mode high frequency instantaneous energy may be extracted from the line mode high frequency instantaneous energy set, and then the line corresponding to the maximum line mode high frequency instantaneous energy is determined as the faulty line.

[0075] In a possible implementation, after determining the fault line in the distribution network according to the line mode high-frequency instantaneous energy set, the method further includes: determining the fault point interval of the fault line; and displaying the fault point interval. After determining the fault line, the fault point location analysis can be performed on the fault line to obtain the fault point interval, which is the location interval. Displaying the fault point interval can prompt the maintenance personnel the location of the fault, so as to facilitate subsequent maintenance processing.

[0076] In this example, after a fault occurs in the distribution network, a current traveling wave is generated and propagated to each line in the distribution network; the three-phase voltage data of each line in the distribution network after the current traveling wave propagates is detected; the fault phase is selected according to the three-phase voltage data of the bus in the distribution network to obtain a fault phase selection result; if the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set; the fault line in the distribution network is determined according to the line mode high-frequency instantaneous energy set, so that the line mode high-frequency instantaneous energy of each line can be calculated according to the three-phase voltage data after the current traveling wave propagates in each line, and the faulty line is determined according to the line mode high-frequency instantaneous energy, thereby improving the accuracy of determining the faulty line.

[0077] In a specific embodiment, the present application also provides another novel method for selecting a line for a single-phase ground fault in a power distribution network, which is as follows:

[0078] Step 1: Analyze the impact of the multi-outlet structure of the distribution network and the line branch nodes on traveling wave transmission

[0079] See also Figure 1B and Figure 2 , Figure 1B A 10kV distribution network model is shown. Figure 2 The small resistance perturbation traveling wave transmission process is shown in Figure 2. Figure 1B and Figure 2 As an example, the distribution network system of line L 1 , L 2 , L 3 , L 4 , L 5 and L 6 The wave impedance is Z C1 , Z C2 , Z C3 , Z C4 , Z C5 and Z C6 , L 1 , L 2 , L 3 and L 4 It is connected through busbar M, and L 4 , L 5 and L 6 The connection is achieved through the branch node P. Assuming that a small resistance disturbance occurs at the neutral point of the busbar, the incident voltage traveling wave U 11 Before the end of each line, there is no voltage on the remaining lines. C0 is the initial wave impedance, Z CMΣ is the wave impedance of the busbar.

[0080] When the incident traveling wave U11 When moving from the busbar to the direction of each outgoing line to the busbar M, a reflected traveling wave U 12 , its movement direction and U 11 On the contrary; at the same time, a refracted traveling wave U will be generated at the busbar end 13 , U 23 , U 33 and U 43 , its movement direction and U 11 Consistent. 43 When moving to the branch node P, L 4 A reflected traveling wave U 42 , its movement direction and U 43 On the contrary; at the same time, L 5 and L 6 A refracted traveling wave U will be generated 53 and U 63 , its movement direction and U 23 Consistent.

[0081] The refraction and reflection coefficients at the busbar M and the branch node P can be expressed by equations (1) and (2) respectively.

[0082]

[0083]

[0084] In formula (1): M and γ M are the reflection coefficient and refraction coefficient of the fault traveling wave at the busbar M respectively; ρ P and γ P are the reflection coefficient and refraction coefficient of the fault traveling wave at the branch node P, respectively. Based on this, all refracted and reflected waves can be expressed as the incident wave U 11 It is expressed as:

[0085]

[0086] When the size of the voltage traveling wave is determined, the reflected current traveling wave and the refracted current traveling wave can be easily calculated based on the wave impedance of each line. The above-mentioned laws of refraction and reflection of the voltage traveling wave also apply to the current traveling wave. The number of outgoing lines and branch nodes has an impact on the refraction and reflection of the voltage and current traveling waves. The wave impedance of each line connected to the bus and branch nodes directly affects the amplitude of the refraction and reflection traveling waves. The wave impedance will change according to the frequency of the traveling wave, causing the refraction and reflection coefficient of the traveling wave to change with the frequency. Therefore, the degree of refraction and reflection of traveling wave components of different frequencies at the bus and branch nodes is different, resulting in large differences in the time-frequency of fault traveling waves detected by the traveling wave detection devices on different lines.

[0087] Obviously, after a period of time after the fault occurs, a small resistor is put into use, and the zero-mode traveling wave in the distribution network is transmitted to the fault point to generate a reflected line-mode traveling wave. The line-mode traveling wave is refracted by the busbar and then transmitted to the normal lines. Figure 3 Draw the line mode current traveling wave diagram of the small resistance disturbance generated at the head end of different lines under line fault conditions. Figure 4 The zero-mode traveling wave and line-mode traveling wave of the faulty line and the normal line are compared. The line-mode traveling wave component generated by the faulty line after the small resistance disturbance is more obvious, and its amplitude is much greater than that of the normal line.

[0088] Step 2: Construct a transient energy model of line-mode voltage direction traveling waves based on disturbances

[0089] When the zero-mode traveling wave signal encounters an impedance mismatch point, its reflection coefficient ρ is:

[0090]

[0091] In formula (4): Z T is the characteristic impedance of the signal transmission end; Z 0 is the characteristic impedance of the signal terminal.

[0092] The reflection and refraction process of traveling waves through impedance grounding is as follows Figure 5 As shown in the figure, when a single-phase grounding fault occurs at the feeder node and its grounding resistance is R, the propagation and distribution of the traveling wave present complex characteristics. Part of the traveling wave will penetrate the other side of point A and the fault point and continue to propagate. During the propagation process, the traveling wave will consume part of the energy on the resistance R. Another part of the traveling wave will return from point A along the line. The wave impedance of the fault point can be regarded as an equivalent impedance formed by the parallel connection of the resistance R and the wave impedance Z1, and its reflection coefficient βu and refraction coefficient αu are as follows:

[0093]

[0094]

[0095]

[0096] According to the fault traveling wave transmission theory, the transmission function characterizes the transmission attenuation of the distribution line, including the attenuation, distortion and transmission delay information during the fault traveling wave transmission process. Its transmission function is approximately equivalent to equation (8) and equation (9):

[0097] A(s)=e -γ(s)·x (8)

[0098]

[0099] e is a natural constant.

[0100] Therefore, the line wave impedance can be defined to construct the high-frequency instantaneous energy of the traveling wave in the following form:

[0101]

[0102] In formula (9), k a is the amplitude attenuation coefficient per unit length; τ a is the unit length distortion coefficient; is the traveling wave transmission delay coefficient, H(ω) is the busbar refraction-reflection coefficient, Z f is the line wave impedance, n is the number of branch lines in the distribution network, i f (ω) is the bus disturbance current traveling wave, x is the input signal, s is the frequency domain signal, I f is the frequency domain current, T(*) is the general energy calculation formula, and γ is the refractive index.

[0103] According to the above formula, we deduce that there is an inverse relationship between the amplitude of the fault traveling wave line mode voltage and the frequency and its square. If the line mode voltage amplitude or the 3 / 2 power of its modulus is used as the energy operator for extraction, the low-frequency information is mainly used, while the instantaneous high-frequency information in the line mode traveling wave is ignored. In order to accurately capture the difference in the instantaneous energy of the traveling wave between the fault line and the normal line, the product of the amplitude of each frequency component of the line mode traveling wave and the 3 / 2 power of the frequency is innovatively selected as the new transient energy. This improved transient energy takes into account low-frequency information and also focuses on the extraction of instantaneous high-frequency information, reflecting the energy characteristics of the traveling wave more comprehensively. By comparing the difference in the instantaneous energy of the traveling wave between the fault line and the normal line, the fault line can be selected and located more effectively, and the operating reliability and stability of the power system can be improved. The expression of each frequency component of the instantaneous energy of the traveling wave is formula (11).

[0104]

[0105] When a small resistor is inserted to induce traveling wave disturbance signals, these signals will propagate toward the fault point. During this process, the amplitude changes of the three-phase currents are consistent. According to the principle of Karen Bell transformation, no line mode component is generated in the system, and only the zero mode component propagates along the line. On a sound line, only the existence of the zero mode component can be detected. When the traveling wave signal reaches the fault point, a sudden change in the line mode component will occur. This component will be reflected back to the head end of the line and captured by the detection device. The current traveling waves of the other two phases will continue to propagate along the line to the end. The line mode component detected at the head end must come from the fault point. When the line mode traveling wave of the faulty line passes through the bus, refraction and attenuation will occur. The instantaneous energy of the line mode traveling wave of the faulty line in the high frequency part

[0106] This feature provides an important basis for identifying and locating faults. The line mode traveling wave of the faulty line will be refracted and attenuated after passing through the busbar, and the instantaneous energy of the line mode traveling wave in the high frequency part will obviously exceed that of the normal line.

[0107] It can be seen that the line mode traveling wave refraction signal is a full-band signal with a continuous spectrum. When a fault occurs, due to the frequency-dependent characteristics of the distribution parameters of the distribution line, as the distance to the fault increases, the high frequency band of the fault traveling wave is severely attenuated, and the farther the fault distance is, the stronger the line attenuation effect is. Through the combined effects of bus boundary refraction and full-length transmission attenuation of the transmission line, the high-frequency signal will be greatly attenuated when passing through the bus boundary, which can amplify the transient energy difference of the line mode traveling wave between the sound line and the fault line. Accurately describing the change trend of the refracted traveling wave frequency component can reliably select the line.

[0108] In each line, the high-frequency instantaneous energy of the line mode signal of the traveling wave reflected by a small resistance disturbance is significantly different between the fault line and the normal line. Only at the fault point of the fault line will the line mode traveling wave signal be refracted and reflected. The line mode traveling wave refracted from the faulty feeder to the normal feeder through the boundary of the bus line is relatively weak. Therefore, the present invention selects the high-frequency instantaneous energy of the line mode traveling wave at the head end of each feeder as the criterion for fault line selection.

[0109] Step 3: Extract the high-frequency instantaneous energy difference of the line mode traveling wave under disturbance

[0110] In view of the significant attenuation effect of the bus boundary on the high-frequency energy of the traveling wave, the high-frequency transient energy of the line-mode voltage traveling wave of the faulty feeder detected at the head end will be significantly greater than the high-frequency transient energy of the traveling wave at the head end of the normal feeder, and its low-frequency energy will be almost similar due to the weak bus attenuation. If only the amplitude is used as the basis to calculate the instantaneous energy, its high-frequency energy will be significantly smaller than the low-frequency energy; if only the full-band energy of the fault traveling wave is used for fault detection, it may lead to misjudgment. For this reason, it is necessary to re-derive a new characteristic index to amplify the difference in line-mode high-frequency energy detected at the head end between the healthy feeder and the faulty feeder, so as to achieve rapid and accurate identification of the fault line selection.

[0111] In order to accurately describe the changing trend of line mode traveling wave transient energy, the relationship between the line mode traveling wave transient energy of the sound line and the fault line and the frequency is analyzed, and the formula is derived to obtain:

[0112]

[0113] According to the transient energy derivative function (12) of the traveling wave line mode, the fault line is a When x>0, its derivative function is greater than 0, and the transient energy of the line-mode traveling wave increases monotonically; when 1-ωτ aWhen \(x \lt 0\), the derivative of the transient traveling wave energy of the line mode decreases monotonically. Therefore, when a line fault occurs, there is a maximum value in the energy of each frequency component of the refracted line-mode traveling wave generated by the small-resistance disturbance. Thus, when this frequency component is selected as the main frequency component, the transient instantaneous energy of its line-mode traveling wave will decrease monotonically when exceeding this main frequency component. This main frequency component is defined as \(\omega\). o For a sound line, its bus refraction coefficient decreases monotonically with the increase of frequency, \(H'(\omega)\lt0\), \(0\lt H(\omega)\lt1\). Therefore, the first half of it has the same change trend as that of the fault line, and there is also a maximum value in the transient energy of its line-mode traveling wave, and the overall trend decreases monotonically.

[0114] Obviously, from the above analysis process of the transient energy of the line-mode traveling wave, it can be concluded that the high-frequency instantaneous energies of the fault line and the sound line are significantly different due to the high-frequency filtering characteristics of the line boundary.

[0115] According to Figure 6 In [reference], from the wavelet time-frequency diagram, it can be seen that for the line-mode traveling wave signal of the fault line between 1 - 100 kHz, using the product of the line-mode traveling wave amplitude and the 3 / 2 power of the frequency can increase the proportion of the high-frequency component in the traveling wave signal spectrum and increase the transient energy of the line-mode traveling wave to make the difference from the normal line larger.

[0116] In this step, frequency information is introduced from the perspective of transient energy, and the product of the line-mode traveling wave amplitude and the 3 / 2 power of a specific frequency band is used to describe the transient energy. By amplifying the differences in high-frequency and low-frequency energies between the fault line and the sound line, the line-mode voltage direction traveling wave high-frequency instantaneous transient energy method proposed in this scheme highlights the high-frequency and low-frequency energy characteristics in the fault state and the difference in high-frequency instantaneous energies between the normal feeder and the fault feeder, which better lays a foundation for designing the subsequent line selection criterion.

[0117] Step 4: Design of line selection criterion

[0118] According to the foregoing steps, it can be obtained that the line boundary system of the distribution network bus has strong high-frequency refraction attenuation characteristics. When a small resistance is inserted, zero-mode traveling waves will be generated and propagate to each feeder, and the disturbance traveling waves show a consistent change trend in the three-phase current amplitudes. Only zero-mode traveling waves propagate along each line, and the zero-mode traveling waves will reach the fault point of the fault line and generate line-mode components. Other normal feeders only generate weak traveling waves at the end of the line or at the node of the cable-overhead line. The high-frequency transient energy of the refracted line-mode component of the fault line is significantly higher than that of the normal line. Therefore, a line selection method based on the high-frequency instantaneous energy of the line-mode traveling wave at the head end can be designed to distinguish between the fault line and the sound line.

[0119] In the scenario of high-resistance fault, the signal of the fault traveling wave is relatively weak, and the signal of the high-frequency transient traveling wave is even lower. Using traditional methods to identify the polarity and amplitude of traveling waves may increase the risk of misjudgment. If only the traveling wave integral ratio method is used, the line selection may fail because the positive and negative traveling waves are very close. The time-frequency energy of the line mode traveling wave at the head end of the distribution network is selected as the research object. Here, this method selects the high-frequency instantaneous energy of the line mode traveling wave with small resistance disturbance as the criterion for line selection, and uses the product of the instantaneous amplitude of the traveling wave and the 3 / 2 power of the instantaneous frequency to calculate the high-frequency instantaneous energy of the line mode current traveling wave.

[0120] The instantaneous energy of the line mode traveling wave reflected by the fault line can be described as:

[0121]

[0122] The instantaneous energy of the traveling wave detected by the monitoring point of the sound line is:

[0123]

[0124] Due to the strong high-frequency traveling wave attenuation characteristics of the busbar boundary, the refracted line mode traveling wave generated by the small resistance disturbance will be significantly attenuated after entering the busbar, especially the reflected line mode traveling wave between 80kHz and 100kHz. Since the traveling wave sensor is installed at the head end of each distribution network branch line, the high-frequency component of the fault traveling wave detected at the head end of the fault feeder is not affected by the busbar boundary. The line mode traveling waves detected by other normal feeders are all obtained by the refraction and attenuation of the fault feeder through the busbar boundary. Through the high-frequency transient energy of the traveling wave constructed in this chapter, the line selection criterion can be designed as formula (16):

[0125]

[0126] Among them, E i and E j are the high-frequency instantaneous energies on the ith and jth lines in the distribution network respectively, and g is the average of the high-frequency instantaneous energies of the remaining lines excluding the maximum value in the line. Since the high-frequency instantaneous energy of the faulty line is significantly greater than that of other normal lines, the high-frequency instantaneous energies of the line mode traveling waves at the head ends of all normal lines are subtracted, and the difference is also significantly greater than the sum of the average energies of other normal feeders. In this case, the line is a faulty line. When the high-frequency instantaneous energy of the refracted line mode voltage traveling wave of the faulty feeder satisfies the above formula, and its difference is still greater than the sum of the average values ​​of other normal feeders, the ith line can be determined to be a faulty line.

[0127] Step 5: Line selection process design

[0128] The specific implementation steps of the specific line selection method process proposed by the present invention are described as follows:

[0129] 1) After a single-phase grounding fault occurs, the system senses a high-resistance fault through the arc suppression coil grounding method, and selects the peak moment of the neutral point voltage to connect a small parallel resistor, which will generate a current traveling wave and propagate to the line.

[0130] 2) After a small resistor is connected to the neutral point, detect the three-phase current and voltage data of each line at the head end of each feeder.

[0131] 3) Use the bus three-phase voltage to select the fault phase. According to the fault phase selection results, when a phase a or b fault occurs, the 1-mode or 2-mode current can be selected as the research object; when a phase C fault occurs, the 2-mode current is selected as the research object.

[0132] 4) When it is determined that a single-phase grounding fault occurs in the distribution network, the S transform is selected and the Teager energy operator is used to calculate the instantaneous energy of the voltage traveling wave in each line frequency band. The calculation formula of the Teager energy operator is:

[0133]

[0134] In the above formula, E is the high-frequency instantaneous energy of the line mode within the frequency band; Tz is the sampling time; ωa-ωb is the frequency band selection range; (t, ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the ω frequency band at time t. The high-frequency instantaneous energy of the line mode voltage traveling wave signal is used to judge the line fault. At this time, the line with the highest instantaneous energy is the faulty line.

[0135] For the above embodiments, please refer to Figure 7 , Figure 7 A schematic diagram of the structure of a terminal provided in an embodiment of the present application, such as Figure 7 As shown, it includes a processor, an input device, an output device and a memory, which are connected to each other, wherein the memory is used to store a computer program, the computer program includes program instructions, the processor is configured to call the program instructions, and the program includes instructions for executing the following steps;

[0136] After a fault occurs in the distribution network, a current traveling wave is generated and propagates to each line in the distribution network;

[0137] Detecting three-phase voltage data after current traveling wave propagation in each line of the distribution network;

[0138] Perform fault phase selection according to the three-phase voltage data of the busbar in the distribution network to obtain the fault phase selection result;

[0139] If the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set;

[0140] A fault line in the distribution network is determined according to the line mode high frequency instantaneous energy set.

[0141] The above mainly introduces the scheme of the embodiment of the present application from the perspective of the execution process on the method side. It is understandable that in order to realize the above functions, the terminal includes a hardware structure and / or software module corresponding to the execution of each function. Those skilled in the art should easily realize that, in combination with the units and algorithm steps of each example described in the embodiments provided herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0142] The embodiment of the present application can divide the terminal into functional units according to the above method example. For example, each functional unit can be divided according to each function, or two or more functions can be integrated into one processing unit. The above integrated unit can be implemented in the form of hardware or in the form of software functional units. It should be noted that the division of units in the embodiment of the present application is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0143] In line with the above, see Figure 8 , Figure 8 The present invention provides a schematic diagram of a novel single-phase ground fault line selection device for a power distribution network. Figure 8 As shown, the device comprises:

[0144] A generating unit 301 is used to generate a current traveling wave and propagate it to each line in the distribution network after a fault occurs in the distribution network;

[0145] The detection unit 302 is used to detect the three-phase voltage data after the current traveling wave propagation is performed on each line in the distribution network;

[0146] The processing unit 303 is used to perform fault phase selection according to the three-phase voltage data of the busbar in the distribution network to obtain a fault phase selection result;

[0147] The calculation unit 304 is used to calculate the line mode high-frequency instantaneous energy corresponding to each line according to the three-phase voltage data of each line if the fault phase selection result is a single-phase grounding fault, and obtain the line mode high-frequency instantaneous energy set;

[0148] The determination unit 305 is configured to determine a fault line in the distribution network according to the line mode high frequency instantaneous energy set.

[0149] In a possible implementation, the calculation unit 304 is specifically configured to:

[0150] The line mode high frequency instantaneous energy corresponding to each line is calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set:

[0151]

[0152] Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

[0153] In a possible implementation, the determining unit 305 is specifically configured to:

[0154] Extracting the maximum line mode high frequency instantaneous energy from the line mode high frequency instantaneous energy set;

[0155] The line corresponding to the maximum line mode high frequency instantaneous energy is determined as a faulty line.

[0156] In a possible implementation, the generating unit 301 is specifically configured to:

[0157] After a fault occurs in the distribution network, obtain the peak moment of the neutral point voltage;

[0158] At the peak moment of the neutral point voltage, a parallel resistor is connected to generate a current traveling wave through the parallel resistor and propagates to each line in the distribution network.

[0159] In a possible implementation, after determining the fault line in the distribution network according to the line mode high frequency instantaneous energy set, the device is further used to:

[0160] Determining a fault point interval of the fault line;

[0161] The fault point interval is displayed.

[0162] An embodiment of the present application also provides a computer storage medium, wherein the computer storage medium stores a computer program for electronic data exchange, and the computer program enables a computer to execute part or all of the steps of any new method for selecting a single-phase grounding fault line in a distribution network as recorded in the above method embodiments.

[0163] An embodiment of the present application also provides a computer program product, which includes a non-transitory computer-readable storage medium storing a computer program, and the computer program enables a computer to execute part or all of the steps of any new distribution network single-phase grounding fault line selection method recorded in the above method embodiments.

[0164] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0165] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0166] In the several embodiments provided in the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only schematic, such as the division of the units, which is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the device or unit can be electrical or other forms.

[0167] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0168] In addition, the functional units in the various embodiments of the application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware or in the form of software program modules.

[0169] If the integrated unit is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a memory, including a number of instructions to enable a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned memory includes: U disk, read-only memory (ROM), random access memory (RAM), mobile hard disk, disk or optical disk and other media that can store program codes.

[0170] A person of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable memory, which can include: a flash drive, a read-only memory, a random access memory, a magnetic disk or an optical disk, etc.

[0171] The embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A novel single-phase ground fault line selection method for distribution network, characterized in that: The method comprises: After a fault occurs in the distribution network, a current traveling wave is generated and propagates to each line in the distribution network; Detecting three-phase voltage data after current traveling wave propagation in each line of the distribution network; Perform fault phase selection according to the three-phase voltage data of the busbar in the distribution network to obtain the fault phase selection result; If the fault phase selection result is a single-phase grounding fault, the line mode high-frequency instantaneous energy corresponding to each line is calculated according to the three-phase voltage data of each line to obtain a line mode high-frequency instantaneous energy set; A fault line in the distribution network is determined according to the line mode high frequency instantaneous energy set.

2. The novel single-phase ground fault line selection method for distribution network according to claim 1 is characterized in that: The method of calculating the line mode high-frequency instantaneous energy corresponding to each line according to the three-phase voltage data of each line to obtain the line mode high-frequency instantaneous energy set includes: The line mode high frequency instantaneous energy corresponding to each line is calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set: Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

3. The novel single-phase ground fault line selection method for distribution network according to claim 2 is characterized in that: The determining of a fault line in the distribution network according to the line mode high frequency instantaneous energy set comprises: Extracting the maximum line mode high frequency instantaneous energy from the line mode high frequency instantaneous energy set; The line corresponding to the maximum line mode high frequency instantaneous energy is determined as a faulty line.

4. The novel single-phase ground fault line selection method for distribution network according to any one of claims 1 to 3, characterized in that: After a fault occurs in the distribution network, a current traveling wave is generated and propagated to each line in the distribution network, including: After a fault occurs in the distribution network, obtain the peak moment of the neutral point voltage; At the peak moment of the neutral point voltage, a parallel resistor is connected to generate a current traveling wave through the parallel resistor and propagates to each line in the distribution network.

5. The novel single-phase ground fault line selection method for distribution network according to claim 4 is characterized in that: After determining the fault line in the distribution network according to the line mode high frequency instantaneous energy set, the method further includes: Determining a fault point interval of the fault line; The fault point interval is displayed.

6. A new type of single-phase ground fault line selection device for distribution network, characterized in that: The device comprises: A generating unit, used to generate a current traveling wave and propagate it to each line in the distribution network after a fault occurs in the distribution network; A detection unit, used to detect three-phase voltage data after current traveling wave propagation in each line in the distribution network; A processing unit, used for performing fault phase selection according to three-phase voltage data of a busbar in a distribution network to obtain a fault phase selection result; A calculation unit, for calculating the line mode high-frequency instantaneous energy corresponding to each line according to the three-phase voltage data of each line if the fault phase selection result is a single-phase grounding fault, and obtaining a line mode high-frequency instantaneous energy set; A determination unit is provided for determining a fault line in the distribution network according to the line mode high frequency instantaneous energy set.

7. The novel single-phase ground fault line selection device for power distribution network according to claim 6 is characterized in that: The computing unit is specifically used for: The line mode high frequency instantaneous energy corresponding to each line is calculated by the method shown in the following formula to obtain the line mode high frequency instantaneous energy set: Where E is the line mode high frequency instantaneous energy within the frequency band, Tz is the sampling time, ωa-ωb is the frequency band selection range, and U(t,ω) is the instantaneous amplitude of the refracted line mode voltage traveling wave in the three-phase voltage data at the ω frequency band at time t.

8. The novel single-phase ground fault line selection device for power distribution network according to claim 7 is characterized in that: The determining unit is specifically used for: Extracting the maximum line mode high frequency instantaneous energy from the line mode high frequency instantaneous energy set; The line corresponding to the maximum line mode high frequency instantaneous energy is determined as a faulty line.

9. A terminal, characterized in that: The invention comprises a processor, an input device, an output device and a memory, wherein the processor, the input device, the output device and the memory are interconnected, wherein the memory is used to store a computer program, the computer program comprises program instructions, and the processor is configured to call the program instructions to execute the new distribution network single-phase grounding fault line selection method as described in any one of claims 1 to 5.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor, the processor executes the new single-phase grounding fault line selection method for distribution network according to any one of claims 1 to 5.

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