1. A high-resistance grounding fault detection method for a low-resistance grounding system is characterized by comprising the following steps:

acquiring a zero sequence current transient component amplitude value at an outlet of a target detection line;

extracting two attenuated direct current component amplitudes of each line from the zero sequence current transient component amplitudes by adopting a preset Prony algorithm;

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes;

if the amplitude ratios corresponding to all the target detection lines are approximately equal under a preset ratio rule, judging that the bus has a fault;

and if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule, judging that the line corresponding to the current amplitude ratio has a fault.

2. A method for detecting a high impedance ground fault of a low resistance grounding system according to claim 1, wherein said calculating an amplitude ratio of each line according to two said attenuated dc component amplitudes comprises:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

3. The method for detecting the high impedance ground fault of the small resistance grounding system according to claim 1, wherein the preset ratio rule is as follows:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

4. A low resistance grounding system high resistance grounding fault detection method according to claim 1, characterized in that said preset range is [0.9,1.1 ].

5. The utility model provides a low resistance grounding system high resistance ground fault detection device which characterized in that includes:

the acquisition module is used for acquiring a zero sequence current transient component amplitude value at the outlet of the target detection line;

the extraction module is used for extracting two attenuated direct current component amplitudes of each line from the zero sequence current transient component amplitudes by adopting a preset Prony algorithm;

the calculation module is used for calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes;

the first judgment module is used for judging that the bus has a fault if the amplitude ratios corresponding to all the target detection lines are approximately equal under a preset ratio rule;

and the second judgment module is used for judging that the line corresponding to the current amplitude ratio fails if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule.

6. The high impedance ground fault detection device of claim 5, wherein the calculation module is specifically configured to:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

7. The high impedance ground fault detection device of claim 5, wherein the preset ratio rule is:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

8. A low resistance grounding system high resistance grounding fault detection device as claimed in claim 5, wherein said preset range is [0.9,1.1 ].

9. A high resistance ground fault detection device for a low resistance ground system, the device comprising a processor and a memory;

the memory is used for storing program codes and transmitting the program codes to the processor;

the processor is used for executing the method for detecting the high-resistance ground fault of the small-resistance grounding system according to any one of claims 1 to 4 according to instructions in the program code.

10. A computer-readable storage medium for storing a program code for executing the method for detecting a high impedance ground fault of a small impedance grounding system of any one of claims 1 to 4.

Background

Traditionally, a common line selection method for ground faults of a low-resistance grounding system is timing-limited overcurrent protection. The method needs to consider the influence of the maximum unbalanced current and sets a higher over-current protection setting value, so that high-resistance fault line selection cannot be realized. However, when a high-resistance ground fault occurs, the fault characteristic quantity of the system is small, and how to effectively utilize the fault characteristic quantity of the high-resistance ground is a prominent problem of line selection of the current low-resistance ground system.

At present, the method for positioning or detecting the high-resistance grounding fault of the low-resistance grounding system mainly comprises an artificial intelligence method, an arc characteristic identification method and the like. However, artificial intelligence methods lack a large amount of field data for training and arc signature methods are too demanding for fault conditions.

Disclosure of Invention

The application provides a high-resistance grounding fault detection method and a related device for a low-resistance grounding system, which are used for relieving the technical problem that limitations on data and fault conditions exist in the actual fault detection process in the prior art.

In view of this, the present application provides, in a first aspect, a method for detecting a high-resistance ground fault of a low-resistance ground system, including:

acquiring a zero sequence current transient component amplitude value at an outlet of a target detection line;

extracting two attenuated direct current component amplitudes of each line from the zero sequence current transient component amplitudes by adopting a preset Prony algorithm;

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes;

if the amplitude ratios corresponding to all the target detection lines are approximately equal under a preset ratio rule, judging that the bus has a fault;

and if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule, judging that the line corresponding to the current amplitude ratio has a fault.

Preferably, the calculating the amplitude ratio of each line according to the two attenuated dc component amplitudes includes:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

Preferably, the preset ratio rule is as follows:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

Preferably, the preset range is [0.9,1.1 ].

The present application provides in a second aspect a high impedance ground fault detection device for a low resistance ground system, comprising:

the acquisition module is used for acquiring a zero sequence current transient component amplitude value at the outlet of the target detection line;

the extraction module is used for extracting two attenuated direct current component amplitudes of each line from the zero sequence current transient component amplitudes by adopting a preset Prony algorithm;

the calculation module is used for calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes;

the first judgment module is used for judging that the bus has a fault if the amplitude ratios corresponding to all the target detection lines are approximately equal under a preset ratio rule;

and the second judgment module is used for judging that the line corresponding to the current amplitude ratio fails if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule.

Preferably, the calculation module is specifically configured to:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

Preferably, the preset ratio rule is as follows:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

Preferably, the preset range is [0.9,1.1 ].

A third aspect of the present application provides a high impedance ground fault detection device for a low resistance ground system, the device comprising a processor and a memory;

the memory is used for storing program codes and transmitting the program codes to the processor;

the processor is configured to execute the method for detecting a high-resistance ground fault of a low-resistance ground system according to the first aspect.

A fourth aspect of the present application provides a computer-readable storage medium for storing program codes for executing the method for detecting a high impedance ground fault of a low impedance grounding system according to the first aspect.

According to the technical scheme, the embodiment of the application has the following advantages:

the application provides a high-resistance grounding fault detection method for a small-resistance grounding system, which comprises the following steps: acquiring a zero sequence current transient component amplitude value at an outlet of a target detection line; extracting two attenuated direct current component amplitudes of each line from the zero sequence current transient component amplitudes by adopting a preset Prony algorithm; calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes; if the corresponding amplitude ratios of all the target detection lines are approximately equal under the preset ratio rule, judging that the bus has a fault; if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule, the line corresponding to the current amplitude ratio is judged to have a fault.

According to the high-resistance grounding fault detection method for the small-resistance grounding system, fault judgment is carried out by obtaining the zero-sequence current transient component amplitude, the selected index is easy to obtain, the actual operation is simple, the Prony algorithm contains an attenuation coefficient, the dynamic signal has certain correspondence, and the low frequency in the signal can be obtained; moreover, the fault detection method can detect not only the common line fault but also the bus fault according to the ratio judgment of the index, does not need to utilize other information similar to voltage or polarity and the like, and improves the applicability and the high efficiency of fault detection. Therefore, the method and the device can solve the technical problem that the prior art has limitations on data and fault conditions in the actual fault detection process.

Drawings

Fig. 1 is a schematic flowchart of a high-resistance ground fault detection method for a low-resistance ground system according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of a high-resistance ground fault detection apparatus of a small-resistance ground system according to an embodiment of the present application;

fig. 3 is a schematic diagram of a high-resistance ground fault simulation model of a small-resistance ground system constructed by MATLAB according to an embodiment of the present application;

fig. 4 is a waveform diagram of transient current obtained at the outlet of each line when a fault occurs at a transition resistance of 600 Ω and k1 according to an embodiment of the present application.

Detailed Description

In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Compared with the prior art, the applicant believes that the circuit analysis method is simpler, more convenient and clearer and is more suitable for practical application. Under the high-resistance grounding fault, the transient component of the current at the outlet of the line contains abundant fault information. The transient state quantity of the zero sequence current can be decomposed into a combination form of sine functions with different frequencies, different amplitudes and different initial phases and decaying exponentially by utilizing a Prony algorithm, and the connection between the sine functions is searched, so that the positive effect on realizing the high-resistance grounding fault of the low-resistance grounding system is achieved. Therefore, the application provides a high-resistance grounding fault detection method for a low-resistance grounding system.

For easy understanding, referring to fig. 1, an embodiment of a method for detecting a high-resistance ground fault of a low-resistance ground system provided in the present application includes:

step 101, obtaining a zero sequence current transient component amplitude value at an outlet of a target detection line.

And 102, extracting two attenuated direct current component amplitudes of each line from the zero-sequence current transient component amplitudes by adopting a preset Prony algorithm.

The sampling time of the Prony algorithm is shorter than that of the FFT algorithm, which means that the Prony algorithm can extract low-frequency content in a signal; the interval (resolution) between the frequencies calculated by the method is independent of the sampling time, and the resolution is very high; the calculation result contains an attenuation coefficient, which can be regarded as having a certain correspondence to the dynamic signal. And the attenuation is extracted from the zero-sequence current transient component amplitude based on the Prony algorithm, so that the reliability of the extracted signal can be ensured. The two extracted attenuated dc component amplitudes are denoted T1 and T2.

And 103, calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes.

Further, step 103 includes:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

Each line can be calculated by the method in this embodiment to obtain an amplitude ratio, specifically, a ratio is not obtained by randomly calculating the amplitudes of the attenuated direct current components, but a larger value is compared with a smaller value.

And step 104, if the corresponding amplitude ratios of all the target detection lines are approximately equal under the preset ratio rule, judging that the bus has a fault.

Further, the preset ratio rule is as follows:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

Further, the preset range is [0.9,1.1 ].

And 105, if the current amplitude ratio of one line in the target detection line is not approximately equal to the amplitude ratios corresponding to all other lines under the preset ratio rule, judging that the line corresponding to the current amplitude ratio has a fault.

All target detection lines can obtain corresponding amplitude ratios, then the amplitude ratios of all lines are compared pairwise, the comparison mode is that the ratio of the two amplitude ratios is calculated, and if the ratio is within a preset range, the amplitude ratios corresponding to the two lines are judged to be approximately equal; if the amplitude ratio exceeds the preset range, the amplitude ratio corresponding to the two lines is completely unequal. After all lines are compared, the relation of amplitude ratios among all lines can be integrally analyzed, and therefore whether the bus or other lines have faults is judged. The preset range may be [0.9,1.1], or may be set according to actual conditions, and is not limited herein.

According to the high-resistance grounding fault detection method for the small-resistance grounding system, fault judgment is carried out by obtaining the zero-sequence current transient component amplitude, the selected index is easy to obtain, the actual operation is simple, the Prony algorithm contains an attenuation coefficient, certain correspondence is provided for dynamic signals, and low frequency in the signals can be obtained; moreover, the fault detection method can detect not only the common line fault but also the bus fault according to the ratio judgment of the index, does not need to utilize other information similar to voltage or polarity and the like, and improves the applicability and the high efficiency of fault detection. Therefore, the technical problem that limitation on data and fault conditions exists in the actual fault detection process in the prior art can be solved.

For the convenience of understanding, the application uses a simulation case, and a high-resistance ground fault simulation model of a small-resistance ground system is built in MATLAB, as shown in FIG. 3. The transformer transformation ratio in the simulation system is 110kV/10.5kV, and the neutral point grounding resistance is 10 omega. The whole system is provided with 6 lines, wherein the line L1 and the line L2 are overhead lines of 20km and 15km respectively, the lines L3-L6 are cable lines of 5km, 7km, 9km and 12km respectively, and all the line ends are constant impedance loads of 1 MW. Ground faults are set at k1, k2 and k3, respectively, and the fault resistances are set at 600 Ω, 800 Ω and 1000 Ω, respectively, where k1 is 5km from the bus on line L5, k2 is 9km from the bus on line L6, and k3 is on the bus. The line model parameters are shown in table 1.

TABLE 1 line model parameter List

As shown in table 2, the amplitudes of the two attenuated transient current components at the line outlet are different from each other at different fault locations and transition resistances.

TABLE 2 line transient current component amplitude List

As shown in table 3, the amplitude ratio and the high resistance ground fault line selection result of each line can be calculated according to the data in table 2.

TABLE 3 amplitude ratio and line selection result List for each line

According to the data recorded in table 3, it can be seen that, under a high-resistance ground fault, the ratio of the amplitude of the faulty line is unequal to that of the healthy line, and accordingly, the faulty line can be correctly determined.

Referring to fig. 4, a transient current waveform obtained at the outlet of each line when a fault occurs at a transition resistance of 600 Ω and k1 is shown.

For easy understanding, please refer to fig. 2, the present application provides an embodiment of a high resistance ground fault detection apparatus for a small resistance ground system, including:

an obtaining module 201, configured to obtain a zero sequence current transient component amplitude at an outlet of a target detection line;

the extracting module 202 is configured to extract two attenuated direct current component amplitudes of each line from the zero-sequence current transient component amplitudes by using a preset Prony algorithm;

a calculating module 203, configured to calculate an amplitude ratio of each line according to the two attenuated dc component amplitudes;

the first judging module 204 is configured to judge that the bus fails if the amplitude ratios corresponding to all the target detection lines are approximately equal under the preset ratio rule;

the second determining module 205 is configured to determine that a line corresponding to a current amplitude ratio fails if the current amplitude ratio of one line in the target detection line is not approximately equal to amplitude ratios corresponding to all other lines under a preset ratio rule.

Further, the calculating module 203 is specifically configured to:

calculating the amplitude ratio of each line according to the two attenuated direct current component amplitudes based on a preset ratio formula, wherein the preset ratio formula is as follows:

wherein, T₁、T₂And for the amplitudes of the two attenuation direct current components, max { } is used for solving the maximum value, and min { } is used for solving the minimum value.

Further, the preset ratio rule is as follows:

and acquiring two amplitude ratios corresponding to any two lines, calculating the ratio of the two amplitude ratios, judging that the two amplitude ratios are approximately equal if the ratio is within a preset range, and otherwise, judging that the two amplitude ratios are not approximately equal.

Further, the preset range is [0.9,1.1 ].

The application also provides a high-resistance grounding fault detection device of the low-resistance grounding system, which comprises a processor and a memory;

the memory is used for storing the program codes and transmitting the program codes to the processor;

the processor is used for executing the high-resistance ground fault detection method of the small-resistance grounding system in the above method embodiment according to instructions in the program code.

The present application further provides a computer-readable storage medium for storing program codes for executing the method for detecting a high-resistance ground fault of a low-resistance ground system in the above-mentioned method embodiments.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for executing all or part of the steps of the method described in the embodiments of the present application through a computer device (which may be a personal computer, a server, or a network device). And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.