CN115825641A - Method and system for single-phase ground fault line selection in distribution network based on electrical mutation - Google Patents

Abstract

The invention discloses a method and a system for selecting a single-phase earth fault of a power distribution network based on electrical break variables, wherein the method comprises the steps of judging whether the single-phase earth fault occurs according to bus voltage read in real time; respectively calculating and obtaining abrupt variables of current, active power and reactive power before and after a fault occurs; respectively determining a circuit with the maximum mutation quantity of current, active power and reactive power; and if the circuit with the largest mutation quantity of the current, the active power and the reactive power is the same circuit, judging that the circuit is the circuit with the single-phase earth fault. According to the method, additional detection equipment is not needed, only the electric quantity before and after the fault occurs is read through the existing power distribution network dispatching platform, and the fault line is judged according to the quantity relation between the electric outburst variables.

Description

Method and system for single-phase-to-ground fault line selection in distribution network based on electrical mutation

technical field

The invention relates to the technical field of 10kV distribution network, in particular to a method and system for line selection of a single-phase grounding fault in a distribution network based on an electrical mutation.

Background technique

Single-phase ground fault is the most common form of fault in distribution network, accounting for more than 80%. The problem of fault line selection for single-phase ground fault in distribution network is a long-term technical problem. Focusing on the problem of line selection for single-phase ground faults in distribution networks, domestic and foreign scientific and technological workers have carried out extensive research and proposed a variety of line selection methods. These traditional line selection methods can be divided into the following categories: (1) Work-based The line selection method of frequency zero-sequence current is to select the line by comparing the amplitude, polarity, or group comparison of the amplitude and phase of the zero-sequence current; (2) the method of active current or active power direction, which mainly compares the line Amplitude, polarity, and direction realize line selection; (3) Harmonic method, a method to determine the fault line through comprehensive comparison of harmonic amplitude and polarity; (4) Residual incremental method, according to the change of zero-sequence current The method of judging the faulty line by the rate of the fault line. This method first judges whether the line is faulty. If the fault occurs, the inductance value of the arc suppression coil is changed to make the zero-sequence current of each line change accordingly. According to the change rate of the zero-sequence current of the line (5) The first half-wave method, a method for line selection based on the difference in zero-sequence current characteristics between the faulty line and the non-faulty line in the first half cycle when a fault occurs; (6) ) Transient parameter identification method, using the difference in line admittance at the moment of fault as the basis for line selection. These traditional line selection methods have their own advantages and application ranges, but they also have the following disadvantages: (1) The engineering application of these methods requires the installation of signal detection devices, which requires increased investment, and requires power outages when the detection equipment is installed. It not only increases the loss of power failure, but also reduces the reliability of power supply; (2) the accuracy of line selection is generally low when high-impedance grounding occurs.

Contents of the invention

The technical problem to be solved by the present invention: Aiming at the above-mentioned problems of the prior art, a method and system for line selection of a single-phase ground fault in a distribution network based on electrical mutations are provided. The dispatching platform of the distribution network separately reads the electrical quantities before and after the fault occurs, and judges the faulty line according to the quantitative relationship between the electrical mutation quantities, and the method of the present invention is less affected by the grounding resistance of the fault point, and the line selection accuracy is high.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A single-phase-to-ground fault line selection method for distribution network based on electrical mutation, comprising:

S101, judging whether a single-phase ground fault occurs according to the bus voltage read in real time, and if a single-phase ground fault occurs, skip to step S102;

S102, respectively calculate and acquire the sudden changes of current, active power and reactive power before and after the fault occurs;

S103, respectively determine the line with the largest mutation amount of current, active power, and reactive power;

S104, if the lines with the largest sudden changes in current, active power, and reactive power are all the same line, then it is determined that the line is the line with a single-phase ground fault.

Optionally, step S101 judging whether a single-phase-to-ground fault occurs based on the real-time read bus voltage includes calculating the zero-sequence voltage unbalance degree of the line according to the real-time read bus voltage, and if the calculated zero-sequence voltage unbalance degree of the line exceeds the predetermined If the threshold is set, it is determined that a single-phase ground fault has occurred.

Optionally, the preset threshold is 10%.

Optionally, step S102 includes:

S201, based on the power at the time when the single-phase ground fault occurs, read the current, active power, and reactive power of each line within a specified time period before and after the fault occurs from the database of the dispatching platform;

S202. Calculate the sudden change of current, active power, and reactive power before and after the fault according to the current, active power, and reactive power of each line within a specified time period before and after the fault.

Optionally, the specified duration in step S201 is 5 minutes.

Optionally, in step S202, calculating the sudden change of current, active power, and reactive power before and after the fault occurs includes calculating the absolute value of the difference between the currents of each line within a specified time before and after the fault, respectively, as the sudden change of current, Calculate the absolute value of the difference between the active power of each line within the specified time before and after the fault as the sudden change of active power, and calculate the absolute value of the difference between the reactive power of each line within the specified time before and after the fault As a sudden change in reactive power.

Optionally, step S104 also includes that when the line with the largest sudden change in current, active power, and reactive power is not the same line, if a certain line has the largest sudden change in active power and is greater than the sudden change in active power of other lines When it is (n-2) times of the amount, it is determined that the line is a line with a single-phase ground fault, where n is the total number of lines.

In addition, the present invention also provides a distribution network single-phase ground fault line selection system based on electrical mutation, including:

The fault detection program unit is used to judge whether a single-phase ground fault occurs according to the bus voltage read in real time;

The electrical sudden change calculation program unit is used to separately calculate and obtain the sudden changes of current, active power and reactive power before and after the fault occurs;

The maximum mutation amount line location program unit is used to respectively determine the line with the largest mutation amount of current, active power, and reactive power;

The fault line location program unit is used to determine that the line with the largest sudden change in current, active power, and reactive power is the same line, and then determine that the line is the line with a single-phase ground fault.

In addition, the present invention also provides a distribution network single-phase ground fault line selection system based on electrical mutation, which includes interconnected microprocessors and memories, the microprocessor is programmed or configured to perform the electrical mutation based Single-phase-to-earth fault line selection method for large-scale distribution network.

In addition, the present invention also provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and the computer program is used to be programmed or configured by a microprocessor to perform the configuration based on the electrical mutation value. Line selection method for single-phase ground fault in power grid

Compared with the prior art, the present invention mainly has the following advantages:

1. The present invention does not need to add additional detection equipment, and only needs to read the electrical quantities (such as voltage, current, active power, reactive power) before and after the fault occurs through the existing distribution network dispatching platform, and according to the electrical sudden change The quantitative relationship between them can be used to judge the fault line.

2. The method of the present invention is less affected by the grounding resistance of the fault point, and the precision of line selection is high.

Description of drawings

FIG. 1 is a schematic diagram of a distribution network topology in an embodiment of the present invention.

Fig. 2 is a schematic flow chart of the basic method of the embodiment of the present invention.

Detailed ways

和

)，每条线路的参数和负载Z_L均相同且三相对称，负载Z_L的功率因数角为

故障发生在第n条线路的A相，故障点对地电阻为R_f；故障点的稳态电流为I_f。采用对称分量法进行分析，可以求出(1)故障前后，各回路稳态电流的突变量。具体地，故障前后非故障线路电流的突变量如下式所示：Fig. 1 is the distribution network topology schematic diagram in the present embodiment, assume that the distribution network with the neutral point not grounded has n outgoing lines of 10kV, and the bus bars of the lines are connected to three-phase symmetrical voltage sources (

and

), the parameters of each line and the load Z _L are the same and the three phases are symmetrical, and the power factor angle of the load Z _L is

The fault occurs on phase A of the n line, the resistance of the fault point to ground is R _f ; the steady state current of the fault point is I _f . Using the symmetrical component method for analysis, (1) the sudden change of the steady-state current of each circuit before and after the fault can be obtained. Specifically, the sudden change of the non-faulted line current before and after the fault is shown in the following formula:

为每相导线对地电容C₀和故障点对地电阻的功率因数角，

为负载Z_L的功率因数角I_f，n为线路的数量，i为线路的序号。In the above formula, ΔI _fiA , ΔI _fiB and ΔI _fiC are the sudden changes of the currents of the three phases of non-fault circuits A, B and C respectively, I ₀ is the specific current,

is the power factor angle of each phase wire-to-ground capacitance C ₀ and the fault point-to-ground resistance,

is the power factor angle I _f of the load Z _L , n is the number of lines, and i is the serial number of the lines.

The sudden change in the current of the fault line (the nth loop) before and after the fault is shown in the following formula:

In the above formula, ΔI _fnA , ΔI _fnB and ΔI _fnC are the sudden changes of the currents of the three phases A, B and C of the non-fault circuit respectively.

The sudden change of active power of the non-faulted line before and after the fault is shown in the following formula:

The sudden change of active power of the fault line before and after the fault is shown in the following formula:

Among them, ΔP _i is the sudden change of active power of the non-faulted line before and after the fault, ΔP _n is the sudden change of active power of the faulty line before and after the fault, and P _f0 is the active power related to the zero-sequence current.

The sudden change of reactive power of non-faulted lines before and after the fault is shown in the following formula:

ΔQ _i =-Q _f0 ,

The sudden change of reactive power of the fault line before and after the fault is shown in the following formula:

ΔQ _n =(n-1)Q _f0 ,

Among them, ΔQ _i is the sudden change of reactive power of the non-faulted line before and after the fault, ΔQ _n is the sudden change of reactive power of the faulty line before and after the fault, and Q _f0 is the reactive power related to the zero-sequence current_. and have:

为A相电压源的电压，

为每相导线对地电容C₀零序电流的共轭，j为虚数单位。以上公式是在假定线路参数完全对称，并忽略了线路的电阻和电感，实际输电线路并非完全对称，电线电阻和电感的存在也会对影响电气突变量的大小，但故障线路的电流、有功功率、无功功率突变量远大于非故障回路的基本特征不会变，这一特征为基于电气突变量的单相接地故障选线方法提供了理论依据。在此基础上，如图2所示，本实施例基于电气突变量的配电网单相接地故障选线方法包括：In the above formula, ω is the grid angular frequency, C ₀ is the capacitance of each phase wire to ground,

is the voltage of the phase A voltage source,

It is the conjugate of the zero-sequence current of the capacitance C ₀ of each phase conductor to the ground, and j is the imaginary number unit. The above formula assumes that the line parameters are completely symmetrical, and ignores the resistance and inductance of the line. The actual transmission line is not completely symmetrical. The existence of wire resistance and inductance will also affect the size of the electrical mutation, but the current and active power , The basic characteristics of the reactive power mutation is much larger than the non-fault circuit will not change, this characteristic provides a theoretical basis for the single-phase ground fault line selection method based on the electrical mutation. On this basis, as shown in FIG. 2 , the method for line selection of a single-phase ground fault in a distribution network based on electrical mutations in this embodiment includes:

S101, judging whether a single-phase ground fault occurs according to the bus voltage read in real time, and if a single-phase ground fault occurs, skip to step S102;

S102, respectively calculate and acquire the sudden changes of current, active power and reactive power before and after the fault occurs;

S103, respectively determine the line with the largest mutation amount of current, active power, and reactive power;

S104, if the lines with the largest sudden changes in current, active power, and reactive power are all the same line, then it is determined that the line is the line with a single-phase ground fault.

In this embodiment, step S101 judges whether a single-phase ground fault occurs according to the real-time read bus voltage includes calculating the zero-sequence voltage unbalance degree of the line according to the real-time read bus voltage, if the calculated zero-sequence voltage unbalance degree of the line exceeds The preset threshold is determined as a single-phase-to-earth fault. The preset threshold may be selected according to experience and actual conditions. For example, as an optional implementation manner, the preset threshold in this embodiment is 10%.

In this embodiment, step S102 includes:

S201, based on the power at the time when the single-phase ground fault occurs, read the current, active power, and reactive power of each line within a specified time period before and after the fault occurs from the database of the dispatching platform;

S202. Calculate the sudden change of current, active power, and reactive power before and after the fault according to the current, active power, and reactive power of each line within a specified time period before and after the fault.

Wherein, the specified duration before and after the fault occurs can be selected according to experience and actual conditions. For example, as an optional implementation manner, the specified duration in step S201 of this embodiment is 5 minutes.

In this embodiment, the calculation of the sudden change in current, active power, and reactive power before and after the fault in step S202 includes calculating the absolute value of the difference between the currents of each line within a specified time before and after the fault, respectively, as the sudden change in current , calculate the absolute value of the difference between the active power of each line within the specified time before and after the fault as the sudden change of active power, and calculate the absolute value of the difference between the reactive power of each line within the specified time before and after the fault The value is used as the sudden change of reactive power, and the influence of direction can be eliminated through absolute value processing.

Referring to Fig. 1, as an optional implementation mode, step S104 of this embodiment also includes that when the line with the largest mutation amount of current, active power, and reactive power is not the same line, if the active power of a certain line is When the mutation amount is the largest and greater than (n-2) times of the active power mutation amount of other lines, it is determined that the line is the line with a single-phase ground fault, where n is the total number of lines.

To sum up, in this embodiment, the single-phase ground fault line selection method of distribution network based on the electrical mutation quantity directly reads the voltage, current, active power and reactive power of the line from the power grid dispatching platform in real time, and calculates the single-phase ground fault The amount of electrical mutation before and after the occurrence is used as the basis for line selection. Therefore, the method for selecting lines for single-phase ground faults in distribution networks based on electrical mutation in this embodiment does not require additional detection equipment, and only needs to pass through the existing distribution network. The network dispatching platform respectively reads the electrical quantities (such as voltage, current, active power, and reactive power) before and after the fault occurs, and judges the faulty line according to the quantitative relationship between the electrical mutation quantities, and the present embodiment is based on the electrical mutation quantity The single-phase ground fault line selection method of distribution network is less affected by the ground resistance of the fault point, and the line selection accuracy is high.

In addition, completely corresponding to the single-phase-to-ground fault line selection method of the distribution network based on the electrical mutation quantity in this embodiment, this embodiment also provides a distribution network single-phase-to-ground fault line selection system based on the electrical mutation quantity, including:

The fault detection program unit is used to judge whether a single-phase ground fault occurs according to the bus voltage read in real time;

The electrical sudden change calculation program unit is used to separately calculate and obtain the sudden changes of current, active power and reactive power before and after the fault occurs;

The maximum mutation amount line location program unit is used to respectively determine the line with the largest mutation amount of current, active power, and reactive power;

The fault line location program unit is used to determine that the line with the largest sudden change in current, active power, and reactive power is the same line, and then determine that the line is the line with a single-phase ground fault.

In addition, this embodiment also provides a distribution network single-phase ground fault line selection system based on electrical mutation, including interconnected microprocessors and memory, the microprocessor is programmed or configured to perform the aforementioned electrical mutation based Single-phase-to-earth fault line selection method for large-scale distribution network.

In addition, this embodiment also provides a computer-readable storage medium, where a computer program is stored in the computer-readable storage medium, and the computer program is used to be programmed or configured by a microprocessor to perform the aforementioned allocation based on electrical mutation Line selection method for single-phase ground fault in power grid.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein. The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram. These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram. These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (10)

1. A single-phase earth fault line selection method of a power distribution network based on electrical sudden change is characterized by comprising the following steps:

s101, judging whether a single-phase earth fault occurs according to the bus voltage read in real time, and if the single-phase earth fault occurs, skipping to execute the step S102;

s102, respectively calculating and obtaining abrupt changes of current, active power and reactive power before and after a fault occurs;

s103, respectively determining a circuit with the maximum mutation quantity of current, active power and reactive power;

and S104, if the lines with the largest mutation quantity of the current, the active power and the reactive power are the same line, judging that the line is the line with the single-phase earth fault.

2. The method for selecting the single-phase ground fault of the power distribution network based on the electrical break variable according to claim 1, wherein the step S101 of determining whether the single-phase ground fault occurs according to the bus voltage read in real time includes calculating a zero-sequence voltage unbalance of the line according to the bus voltage read in real time, and determining that the single-phase ground fault occurs if the calculated zero-sequence voltage unbalance of the line exceeds a preset threshold.

3. The electrical break variable-based single-phase ground fault line selection method for the power distribution network according to claim 2, wherein the preset threshold is 10%.

4. The method for selecting the single-phase earth fault of the power distribution network based on the electrical mutation quantity as claimed in claim 1, wherein the step S102 comprises:

s201, respectively reading current, active power and reactive power of each line within a specified time length before and after a fault occurs from a database of a dispatching platform based on the time electricity of the single-phase earth fault;

and S202, calculating abrupt change quantities of current, active power and reactive power before and after the fault according to the current, the active power and the reactive power of each line in the specified time before and after the fault.

5. The method for selecting the single-phase earth fault of the power distribution network based on the electrical mutation quantity as claimed in claim 4, wherein the specified time in the step S201 is 5 minutes.

6. The method according to claim 4, wherein the step S202 of calculating the sudden change of the current, the active power and the reactive power before and after the fault occurs comprises calculating an absolute value of a difference between the currents of the lines within a specified time period before and after the fault occurs as the sudden change of the current, calculating an absolute value of a difference between the active power of the lines within the specified time period before and after the fault occurs as the sudden change of the active power, and calculating an absolute value of a difference between the reactive power of the lines within the specified time period before and after the fault occurs as the sudden change of the reactive power.

7. The method according to claim 1, wherein the step S104 further includes, when the line with the largest sudden change of current, active power and reactive power is not the same line, if the sudden change of active power of a certain line is the largest and is greater than (n-2) times the sudden change of active power of other lines, determining that the certain line is the line with the single-phase ground fault, where n is the total number of lines.

8. The utility model provides a distribution network single-phase earth fault route selection system based on electrical abrupt change volume which characterized in that includes:

the fault detection program unit is used for judging whether a single-phase earth fault occurs according to the bus voltage read in real time;

the electric sudden change calculation program unit is used for calculating and obtaining sudden changes of current, active power and reactive power before and after a fault occurs;

the maximum abrupt change line positioning program unit is used for respectively determining a line with the maximum abrupt change of the current, the active power and the reactive power;

and the fault line positioning program unit is used for judging that the line is the line with the single-phase earth fault if the lines with the maximum mutation quantity of the current, the active power and the reactive power are the same line.

9. An electrical break variable based single-phase earth fault line selection system for a power distribution network, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to perform the electrical break variable based single-phase earth fault line selection method for the power distribution network according to any one of claims 1 to 8.

10. A computer-readable storage medium, in which a computer program is stored, wherein the computer program is programmed or configured by a microprocessor to execute the electrical break variable-based single-phase earth fault line selection method for the distribution network according to any one of claims 1 to 8.

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