CN111257693A - Single-phase earth fault positioning method and device for small current grounding system - Google Patents
Single-phase earth fault positioning method and device for small current grounding system Download PDFInfo
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Abstract
The invention provides a single-phase earth fault positioning method and a single-phase earth fault positioning device for a low-current grounding system, wherein the fault positioning method comprises the following steps of; s101: acquiring a zero sequence voltage signal of each phase of line, judging whether the line has a fault according to the zero sequence voltage signal, if so, executing S102, and if not, continuing to execute S101; s102: determining the time of line fault according to the zero sequence voltage signal, and acquiring the maximum value of the zero sequence current signal of each phase of line according to the time; s103: determining a fault line according to the polarity of the maximum value of the zero-sequence current signal; s104: and acquiring the reverse traveling wave of the fault line, and performing wavelet transformation on the reverse traveling wave to determine the position of a fault point. The invention can judge whether the line has a fault by utilizing the characteristics of small value and low signal-to-noise ratio of the fault zero-sequence current signal, large value and high signal-to-noise ratio of the fault zero-sequence voltage signal, determine the fault line when the line has a fault, and process the reverse traveling wave by a wavelet transformation mode, thereby enhancing the anti-interference capability and improving the accuracy of fault positioning.
Description
Technical Field
The invention relates to the field of power system fault positioning, in particular to a method and a device for positioning a single-phase earth fault of a low-current earth system.
Background
In China, neutral points of medium and low voltage distribution systems are mostly in an indirect grounding mode and are called as a neutral point ungrounded system or a neutral point ineffective grounding system, the neutral points of the neutral points are generally grounded through arc suppression coils or resistors, and when single-phase grounding occurs, a small-impedance current loop cannot be formed, so the neutral point ungrounded system is also called as a small-current grounding system. The system comprises a neutral point ungrounded system (NUS), a neutral point arc suppression coil grounding system (NES) and a neutral point resistance grounding system (NRS).
The power distribution network neutral point adopts a low-current grounding mode to improve the power supply reliability, so that the power distribution network neutral point is adopted by power distribution systems of many countries. However, the topology structure, operation requirement and fault characteristics of the system are different from those of a large-current system, and the fault point positioning of the feeder line of the system is always a difficult problem in fault location research.
In the prior art, the discovery and location of single-phase earth faults have the following problems: when a single-phase earth fault occurs on one feeder line, the amplitude of the fundamental component has no obvious change characteristic, and the fault line is difficult to be accurately identified and the fault point positioning is realized by using the steady fundamental frequency component observed by the single feeder line; moreover, because the feeder line is short, the requirement on the accuracy of fault positioning is high, and the existing fault positioning method is difficult to realize accurate positioning.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method and a device for positioning a single-phase earth fault of a small-current earth system, which can judge whether a line has a fault by utilizing the characteristics of small value and low signal-to-noise ratio of a fault zero-sequence current signal, large value and high signal-to-noise ratio of a fault zero-sequence voltage signal, determine the fault line when the line has the fault, process reverse traveling waves in a wavelet transformation mode, enhance the anti-interference capability and improve the accuracy of fault positioning.
In order to solve the above problems, the present invention adopts a technical solution as follows: a small current grounding system single-phase grounding fault positioning method comprises the following steps: s101: acquiring a zero sequence voltage signal of each phase of line, judging whether the line has a fault according to the zero sequence voltage signal, if so, executing S102, and if not, continuing to execute S101; s102: determining the time of the line fault according to the zero sequence voltage signal, and acquiring the maximum value of the zero sequence current signal of each phase of line according to the time; s103: determining a fault line according to the polarity of the maximum value of the zero sequence current signal; s104: and acquiring reverse traveling waves of the fault line, and performing wavelet transformation on the reverse traveling waves to determine the position of a fault point.
Further, the step of determining whether the line has a fault according to the zero sequence voltage signal specifically includes: and judging whether the modulus maximum value of the zero sequence voltage signal is greater than a preset threshold value, if so, determining that the line has a fault, and if not, determining that the line has no fault.
Further, the step of acquiring the zero sequence voltage signal of each phase line specifically includes: and acquiring a zero sequence voltage signal of each phase of line, and performing wavelet transformation on the zero sequence voltage signal to obtain a modulus maximum value of the zero sequence voltage signal.
Further, the step of determining the time of the line fault according to the zero sequence voltage signal specifically includes: and acquiring the time corresponding to the modulus maximum value, and taking the time as the time when the line fails.
Further, the step of obtaining the maximum value of the zero-sequence current signal of each phase line according to the time specifically includes: and performing wavelet transformation on the zero-sequence current signal corresponding to the time to obtain a modulus maximum value of the zero-sequence current signal and the polarity of the zero-sequence current signal corresponding to the modulus maximum value.
Further, the step of determining the fault line according to the polarity of the maximum value of the zero-sequence current signal specifically includes: and judging whether the polarities of the zero sequence current signals of each line are the same or not, if so, determining that the bus is a fault line, and if the polarity of one line is opposite to that of other lines, determining that the line is a fault line.
Further, the step of acquiring the reverse traveling wave of the faulty line specifically includes: and acquiring the electrical data of the single end of the fault line, and acquiring the reverse traveling wave of the fault line according to the electrical data.
Further, the step of performing wavelet transform on the reverse traveling wave to determine the location of the fault point specifically includes: and performing wavelet transformation on the reverse traveling wave, identifying the wave head of the reverse traveling wave according to the singular point of the wavelet transformation, and determining the position of a fault point according to the time of the wave head reaching a reverse traveling wave acquisition point.
Further, the step of determining the position of the fault point according to the time of the wave head reaching the backward traveling wave collecting point specifically includes: the location of the fault point is determined according to equation (1),
wherein L is the distance from the fault point to the reverse traveling wave collection point, T1MAnd T2MIs the time when the reverse traveling wave reaches the collection point for the first time and the second time, and v is the propagation speed of the reverse traveling wave.
Based on the same invention concept, the invention also provides a single-phase earth fault positioning device of the low-current grounding system, wherein the fault positioning device comprises an acquisition unit and a processing unit, and the acquisition unit is in communication connection with the processing unit; the acquisition unit is used for acquiring electrical data and sending the acquired electrical data to the processing unit, wherein the electrical data comprises a zero-sequence voltage signal, a zero-sequence current signal and a reverse traveling wave of a fault line of each phase of line; the processing unit executes the method for positioning the single-phase earth fault of the low-current earthing system according to the electrical data sent by the acquisition unit.
Compared with the prior art, the invention has the beneficial effects that: the characteristics of small fault zero-sequence current signal value, low signal-to-noise ratio, large fault zero-sequence voltage signal value and high signal-to-noise ratio can be utilized to judge whether a line has a fault or not, the fault line is determined when the line has the fault, and the reverse traveling wave is processed in a wavelet transformation mode, so that the anti-interference capability is enhanced, and the accuracy of fault positioning is improved.
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Fig. 1 is a flowchart of an embodiment of a single-phase earth fault positioning method of a low-current grounding system according to the present invention;
fig. 2 is a schematic diagram of one embodiment of fault location in the method for locating a single-phase ground fault of a low-current grounding system according to the present invention;
FIG. 3 is a flowchart illustrating a single-phase ground fault location method for a low-current grounding system according to another embodiment of the present invention;
fig. 4 is a structural diagram of an embodiment of the positioning device for single-phase earth fault of the low-current grounding system of the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.
Referring to fig. 1-3, fig. 1 is a flowchart illustrating a method for locating a single-phase ground fault of a low-current grounding system according to an embodiment of the present invention; FIG. 2 is a schematic diagram of an embodiment of fault location in the method for locating a single-phase ground fault of a low-current grounding system according to the present invention; fig. 3 is a flowchart of a single-phase ground fault location method of a low-current grounding system according to another embodiment of the present invention. Wherein, M in figure 2 is a bus, N is an opposite end bus, the position pointed by the broken line arrow between M and N is a fault point, the reverse traveling wave collection point is arranged on the bus, and T is1M、T2M、T3MThe time of the reverse traveling wave reaching the reverse traveling wave collection point for the first time, the second time and the third time is respectively. The method for positioning the single-phase earth fault of the low-current grounding system is described in detail with reference to the attached drawings 1-3.
In this embodiment, the method for positioning the single-phase earth fault of the low-current earthing system includes:
s101: and acquiring a zero sequence voltage signal of each phase of circuit, judging whether the circuit has a fault according to the zero sequence voltage signal, if so, executing S102, and if not, continuously acquiring the zero sequence voltage signal of each phase of circuit.
In this embodiment, the device for executing the method for positioning the single-phase earth fault of the low-current grounding system is a single chip, an SOC, a background, and other devices capable of processing electrical data of a line.
The single-phase earth fault positioning method of the low-current grounding system is specifically explained by taking the equipment for executing the positioning method as a single chip microcomputer.
In this embodiment, the device for acquiring the zero sequence voltage signal is a zero sequence voltage signal transformer, and the zero sequence voltage signal transformer acquires a zero sequence voltage signal of each phase line in the line and transmits the zero sequence voltage signal to the single chip microcomputer.
The zero sequence voltage signal mutual inductor is connected and communicated with the single chip microcomputer in a wireless or wired mode.
In this embodiment, the step of determining whether the line has a fault according to the zero-sequence voltage signal specifically includes: and judging whether the modulus maximum value of the zero sequence voltage signal is greater than a preset threshold value, if so, determining that the line has a fault, and if not, determining that the line has no fault.
In this embodiment, the preset threshold is stored in the single chip microcomputer, and the specific size may be set according to the actual situation of the single-phase ground fault, which is not described herein.
If the function (signal) f (t) is discontinuous at some local point t0 or the derivative is discontinuous, the function is generally said to be singular at t 0. When the single-phase grounding is carried out, the transient process duration of fault voltage and current is short and contains abundant characteristic quantity, and the value of the transient process is small in steady state, so that a new theory suitable for analyzing the transient component is selected in the grounding fault detection, and the transient characteristic component is extracted.
The wavelet analysis can accurately analyze signals, is particularly sensitive to the transformation of transient sudden change signals and weak signals, and can reliably extract fault characteristics. According to the modulus maximum value theory of wavelet transformation, the signal singularity can be caused by faults and noise, the modulus maximum value point of wavelet transformation corresponds to the singular point of the sampling signal, and the modulus maximum value of the noise is attenuated along with the increase of the scale, so that the influence of the noise can be ignored after proper scale decomposition, and a more ideal transient short circuit signal can be obtained.
In this embodiment, the step of obtaining the zero sequence voltage signal of each phase line specifically includes: and acquiring a zero sequence voltage signal of each phase of line, and performing wavelet transformation on the zero sequence voltage signal to obtain a modulus maximum value of the zero sequence voltage signal. By utilizing the characteristics of large value and high signal-to-noise ratio of the zero-sequence voltage signal when the line fails, the sensitivity of fault discovery is improved by taking the zero-sequence voltage signal as a standard for judging whether the line fails.
In this embodiment, the single chip microcomputer may acquire the zero sequence voltage signal in real time, determine whether the line has a fault according to the zero sequence voltage signal, and also may acquire the zero sequence voltage signal according to a preset period.
S102: and determining the time of the line fault according to the zero sequence voltage signal, and acquiring the maximum value of the zero sequence current signal of each phase of line according to the time.
A zero-sequence sudden change or singular value is generated at the moment of line fault, the polarity of all non-fault line zero-sequence current sudden changes is the same, the polarity of the fault line zero-sequence current sudden changes is opposite to the polarity of the non-fault line zero-sequence current sudden changes, and the amplitude of the fault line zero-sequence current sudden changes is equal to the sum of the amplitude of the non-fault line zero-sequence current sudden changes. The wavelet singularity detection theory is utilized to carry out wavelet transformation on the collected fault signals, a module maximum value point is determined, the magnitude and the polarity of the module maximum value of the zero-sequence current of each line are compared, and the fault line can be distinguished.
In this embodiment, after the line fault is determined, the time corresponding to the zero-sequence voltage signal whose modulo maximum value is greater than the preset threshold value is obtained, and the time is taken as the time when the line fault occurs. And performing wavelet transformation on the zero-sequence current signal through equipment for acquiring the zero-sequence current signal and the zero-sequence current signal corresponding to the time to obtain a modulus maximum value of the zero-sequence current signal and the polarity of the zero-sequence current signal corresponding to the modulus maximum value at the moment.
In this embodiment, the device for acquiring the zero-sequence current signal is a current transformer, the current transformer is wirelessly connected to a single chip microcomputer, the single chip microcomputer receives and stores the zero-sequence current signal sent by the current transformer, and when a line fails, the zero-sequence current signal corresponding to the failure time is acquired from the stored zero-sequence current signal.
In other embodiments, the zero-sequence current signal may also be stored in the current transformer, and the single chip microcomputer obtains the zero-sequence current signal corresponding to the fault time from the current transformer when the fault is determined.
In the above embodiment, the zero sequence voltage transformer and the current transformer may respectively perform wavelet transformation on the acquired zero sequence voltage signal and zero sequence current signal, and the single chip microcomputer receives the zero sequence voltage signal and zero sequence current signal after the wavelet transformation, and determines whether a fault occurs and determines a fault line according to the signals.
S103: and determining a fault line according to the polarity of the maximum value of the zero sequence current signal.
When a line fault occurs, the zero sequence current value is small, the signal-to-noise ratio is low, the zero sequence voltage value is large, and the signal-to-noise ratio is high. When a fault line is identified, a voltage signal is selected as a starting line selection signal, the fault time is determined according to the wavelet transformation modulus maximum value of the voltage signal, then the polarity is compared point by point according to the larger numerical value of the wavelet transformation modulus maximum value of the zero sequence current of each outgoing line, the fault line with opposite polarity can be judged, and if the polarities are the same, the bus fault is judged.
In this embodiment, the step of obtaining the maximum value of the zero-sequence current signal of each phase line according to time specifically includes: and performing wavelet transformation on the zero-sequence current signal corresponding to the time to obtain a modulus maximum value of the zero-sequence current signal and the polarity of the zero-sequence current signal corresponding to the modulus maximum value.
In this embodiment, the step of determining the faulty line according to the polarity of the maximum value of the zero-sequence current signal specifically includes: and judging whether the polarities of the zero sequence current signals of each line are the same or not, if so, determining that the bus is a fault line, and if the polarity of one line is opposite to that of other lines, determining that the line is a fault line.
In other embodiments, the sudden change amplitude of the zero-sequence current may also be determined according to a difference between the modulus maximum of the zero-sequence current and the zero-sequence current amplitude of the line when the fault does not occur, and the line where the zero-sequence current with the largest sudden change amplitude is located may be determined as the fault line.
S104: and acquiring the reverse traveling wave of the fault line, and performing wavelet transformation on the reverse traveling wave to determine the position of a fault point.
The invention mainly uses traveling wave fault location in the actual application, and the application field is mainly high-voltage transmission lines, therefore, the invention primarily tries the traveling wave fault location principle in a low-current grounding system, collects the single-end electrical data of the line, detects the arrival time of the traveling wave head by utilizing the strong function of wavelet transformation on singularity detection, realizes fault location, opens up a new way for the fault location of the low-current grounding system, and provides an important step for improving the automation level of the power distribution network.
Reflection and refraction of waves are important characteristics of line traveling waves, and in power systems, uniform lines exist only under certain conditions. When a traveling wave moves along a wire, if the parameters of the wire or the wave impedance change abruptly at a certain junction, refraction and reflection of the wave occur at that point. After the transmission line is failed, the fault point will produce voltage and current traveling waves moving along the line, and the traveling waves are refracted and reflected at the fault point, the bus of the fault line and the buses at the tail ends of other lines connected with the fault line due to the discontinuous wave impedance, and the fault characteristics of the traveling waves are determined by the refraction and reflection relations among the traveling wave components.
According to electromagnetic field theory, the voltage and current on a single lossless line are functions of position and time, which satisfy the wave equation:
solving the wave equation to obtain equation (2):
According to the above formula, the following can be solved:
forward traveling wave:
reverse traveling wave:
the forward traveling wave is a directional traveling wave that reflects only from the bus direction. The reverse traveling wave reflects only the directional traveling wave from the direction of the faulty line, which carries important information on the fault distance and location, and for the reverse traveling wave, the traveling wave component appearing after the initial traveling wave is either the reflected wave from the faulty point or the reflected wave from the opposite-end bus, and the reflected wave from the faulty point has the same polarity as the initial traveling wave, and the reflected wave from the opposite-end bus has the opposite polarity as the initial traveling wave. Accordingly, it is possible to distinguish the reflected wave from the refracted wave, thereby achieving the purpose of ranging according to the reverse traveling wave.
In this embodiment, the step of acquiring the reverse traveling wave of the faulty line specifically includes: and acquiring the electrical data of the single end of the fault line through equipment arranged at the reverse traveling wave acquisition point, and acquiring the reverse traveling wave of the fault line according to the electrical data. The electrical data may be a voltage wave or a current wave in the fault line, and the reverse traveling wave is obtained through the voltage wave or the current wave.
In this embodiment, the step of performing wavelet transform on the reverse traveling wave to determine the location of the fault point specifically includes: and performing wavelet transformation on the reverse traveling wave, identifying the wave head of the reverse traveling wave according to the singular point of the wavelet transformation, and determining the position of a fault point according to the time of the wave head reaching a reverse traveling wave acquisition point.
In a specific embodiment, the step of determining the position of the fault point according to the time of the wave head reaching the backward traveling wave collecting point specifically includes: determining the distance from the fault point to the reverse traveling wave acquisition point according to the formula (1) so as to determine the position of the fault point,
In other embodiments, the distance from the fault point to the backward traveling wave collecting point can also be determined according to the time when the backward traveling wave arrives at the backward traveling wave collecting point twice in the vicinity.
Has the advantages that: the single-phase earth fault positioning method of the small current grounding system can judge whether the line has a fault by utilizing the characteristics of small value and low signal-to-noise ratio of the fault zero-sequence current signal, large value and high signal-to-noise ratio of the fault zero-sequence voltage signal, determine the fault line when the line has the fault, and process the reverse traveling wave in a wavelet transformation mode, thereby enhancing the anti-interference capability and improving the accuracy of fault positioning.
Based on the same inventive concept, the present invention further provides a positioning device for a single-phase ground fault of a low-current grounding system, please refer to fig. 4, fig. 4 is a structural diagram of an embodiment of the positioning device for a single-phase ground fault of a low-current grounding system of the present invention, and the positioning device for a single-phase ground fault of a low-current grounding system of the present invention is specifically described with reference to fig. 4.
In this embodiment, the fault locating device includes an acquisition unit and a processing unit, wherein the acquisition unit is in communication connection with the processor unit; the acquisition unit is used for acquiring electrical data and sending the acquired electrical data to the processing unit, wherein the electrical data comprises a zero-sequence voltage signal and a zero-sequence current signal of each phase line and a reverse traveling wave of a fault line; the processing unit executes the single-phase earth fault positioning method of the low-current earthing system according to the electrical data sent by the acquisition unit.
In this embodiment, the acquisition unit includes a zero sequence voltage transformer, a current transformer, and a device for acquiring a reverse traveling wave, and the acquisition unit acquires a zero sequence voltage signal, a zero sequence current signal, and a reverse traveling wave of the fault line of the line through the zero sequence voltage transformer, the current transformer, and the device for acquiring a reverse traveling wave, respectively, and sends them to the processing unit, so that the processing unit acquires the fault line and implements fault location.
Has the advantages that: the single-phase earth fault positioning device of the small current grounding system can judge whether a line has a fault by utilizing the characteristics of small fault zero-sequence current signal value, low signal-to-noise ratio, large fault zero-sequence voltage signal value and high signal-to-noise ratio, determine the fault line when the line has the fault, process reverse traveling waves in a wavelet transformation mode, enhance the anti-interference capability and improve the accuracy of fault positioning.
In the embodiments provided in the present invention, it should be understood that the disclosed devices, modules and circuits may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the structural components of the modules may be divided into only one logical function, and other divisions may be made in practice, for example, a plurality of modules or modules may be combined or integrated into another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, devices or indirect coupling or communication connection, and may be in an electrical, mechanical or other form.
The components described as separate parts may or may not be physically separate, and the components shown may or may not be physically separate, may be located in one place, or may be distributed in a plurality of places. Some or all of them can be selected according to actual needs to achieve the purpose of the embodiment.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A single-phase earth fault positioning method of a low-current grounding system is characterized by comprising the following steps of;
s101: acquiring a zero sequence voltage signal of each phase of line, judging whether the line has a fault according to the zero sequence voltage signal, if so, executing S102, and if not, continuing to execute S101;
s102: determining the time of the line fault according to the zero sequence voltage signal, and acquiring the maximum value of the zero sequence current signal of each phase of line according to the time;
s103: determining a fault line according to the polarity of the maximum value of the zero sequence current signal;
s104: and acquiring reverse traveling waves of the fault line, and performing wavelet transformation on the reverse traveling waves to determine the position of a fault point.
2. The method for locating the single-phase earth fault of the small-current grounding system according to claim 1, wherein the step of determining whether the line has a fault according to the zero-sequence voltage signal specifically comprises:
and judging whether the modulus maximum value of the zero sequence voltage signal is greater than a preset threshold value, if so, determining that the line has a fault, and if not, determining that the line has no fault.
3. The method for locating the single-phase earth fault of the small-current grounding system according to claim 2, wherein the step of obtaining the zero-sequence voltage signal of each phase line specifically comprises:
and acquiring a zero sequence voltage signal of each phase of line, and performing wavelet transformation on the zero sequence voltage signal to obtain a modulus maximum value of the zero sequence voltage signal.
4. The method for locating a single-phase ground fault of a low-current grounding system according to claim 2, wherein the step of determining the time when the line has a fault according to the zero-sequence voltage signal specifically comprises:
and acquiring the time corresponding to the modulus maximum value, and taking the time as the time when the line fails.
5. The method for locating the single-phase earth fault of the small-current grounding system according to claim 1, wherein the step of obtaining the maximum value of the zero-sequence current signal of each phase line according to the time specifically comprises:
and performing wavelet transformation on the zero-sequence current signal corresponding to the time to obtain a modulus maximum value of the zero-sequence current signal and the polarity of the zero-sequence current signal corresponding to the modulus maximum value.
6. The method for locating a single-phase ground fault of a low-current grounding system according to claim 5, wherein the step of determining the fault line according to the polarity of the maximum value of the zero-sequence current signal specifically comprises:
and judging whether the polarities of the zero sequence current signals of each line are the same or not, if so, determining that the bus is a fault line, and if the polarity of one line is opposite to that of other lines, determining that the line is a fault line.
7. The single-phase earth fault location method of the small-current grounding system according to claim 1, wherein the step of acquiring the reverse traveling wave of the fault line specifically includes:
and acquiring the electrical data of the single end of the fault line, and acquiring the reverse traveling wave of the fault line according to the electrical data.
8. The single-phase earth fault location method of claim 1, wherein the step of performing wavelet transform on the reverse traveling wave to determine the location of the fault point specifically comprises:
and performing wavelet transformation on the reverse traveling wave, identifying the wave head of the reverse traveling wave according to the singular point of the wavelet transformation, and determining the position of a fault point according to the time of the wave head reaching a reverse traveling wave acquisition point.
9. The method for locating the single-phase earth fault of the small-current grounding system according to claim 8, wherein the step of determining the location of the fault point according to the time of the wave head reaching the backward traveling wave collecting point specifically comprises:
the location of the fault point is determined according to equation (1),
10. The single-phase earth fault positioning device of the low-current grounding system is characterized by comprising an acquisition unit and a processing unit, wherein the acquisition unit is in communication connection with the processing unit;
the acquisition unit is used for acquiring electrical data and sending the acquired electrical data to the processing unit, wherein the electrical data comprises a zero-sequence voltage signal, a zero-sequence current signal and a reverse traveling wave of a fault line of each phase of line;
the processing unit executes the single-phase earth fault positioning method of the low-current earthing system according to any one of claims 1-9 according to the electrical data sent by the acquisition unit.
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| CN113655339A (en) * | 2021-08-20 | 2021-11-16 | 许继集团有限公司 | Fault positioning method and device for direct-current transmission line protection system |
| CN115308638A (en) * | 2022-08-30 | 2022-11-08 | 天津大学 | Fault line identification method suitable for multi-terminal direct-current power transmission system |
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| CN115308638A (en) * | 2022-08-30 | 2022-11-08 | 天津大学 | Fault line identification method suitable for multi-terminal direct-current power transmission system |
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