Single-phase earth fault line positioning method for power distribution network

Abstract

The invention specifically relates to a single-phase earth fault line positioning method for a power distribution network, and belongs to the technical field of fault detection in the power distribution network. The method comprises the following steps of collecting power distribution zero-sequence voltage and arc suppression coil current, calculating and drawing a fault judgment curve according to the zero-sequence voltage and the arc suppression coil current, and judging whether the power distribution network has a single-phase earth fault by judging whether the fault judgment curve exceeds a first fault judgment threshold value or not; after a single-phase earth fault occurs in the power distribution network, zero-sequence current of n feeder lines of the power distribution network is collected in real time and preprocessed, a fault line judgment curve is drawn through the preprocessed zero-sequence current, and a fault line of the power distribution network is positioned through the fault line judgment curve. According to the method, the difference between the fault feeder line and the normal feeder line is amplified in a signal preprocessing mode, then the fault line is sensitively selected, the line where the single-phase earth fault occurs can be rapidly and accurately positioned, and the safety of the power distribution network is greatly improved.

Description

Technical Field

[0001] The present invention specifically relates to a method for locating a single-phase grounding fault line of a power distribution network, and belongs to the technical field of fault detection in a power distribution network (G01R31 / 08). Background Art

[0002] The existing single-phase grounding fault line location methods are mainly divided into active methods and passive methods. The active method represented by the signal injection method will delay the arc extinguishing device due to the injection of non-arc extinguishing current, and may even increase the fault current and worsen the fault. The passive method using steady-state signals needs to avoid a long transient process, which is insufficient in rapidity. In addition, the steady-state quantity changes very little during high-resistance faults, making the line selection method easily lose reliability. Therefore, the passive line selection method using transient characteristics is gaining more and more attention.

[0003] The application number is CN202410979555.9, the application publication number is CN118795277A, and the patent name is: A Chinese invention patent for a single-phase grounding fault line selection method for a small current grounding system based on improved SVM. The VMD algorithm is used to extract transient zero-sequence current and the GOA-SVM optimization classifier is used to select the fault line, but this method has the disadvantages of small training set data and vague physical meaning. The application number is CN201911229871.X, the application publication number is CN110736900A, and the patent name is: A Chinese invention patent for a single-phase grounding fault line selection method for distribution lines based on directional traveling waves. The direction of the initial traveling wave of the line is different for fault line selection, but because the distribution line is short and has many branches, the traveling wave reflection is complex, and it is difficult for high-resistance grounding faults to form obvious traveling waves, and the traveling wave line selection method has certain limitations. The existing line selection technology lacks the ability to quickly and accurately detect within a few cycles after the fault occurs, and the reliability is insufficient in the line asymmetry system. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to quickly and accurately locate the fault line when a single-phase grounding fault occurs in a distribution network.

[0005] In order to solve the above technical problems, the technical solution proposed in the present invention is: a line locating method for a single-phase grounding fault in a distribution network, comprising the following steps:

[0006] Step 1: Set the judgment period T of the single-phase grounding fault in the distribution network, and every other sampling period within the judgment period T The zero-sequence voltage of the distribution network and the current flowing into the arc suppression coil are collected once in real time, and a total of M collections are performed, and the collected zero-sequence voltage of the distribution network and the current flowing into the arc suppression coil are collected to form the first zero-sequence voltage matrix U of the distribution network. 01 and arc suppression coil current matrix I L, as shown in the following equations (1) and (2),

[0007] (1)

[0008] (2)

[0009] In formula (1) and formula (2), They are respectively the distribution network at the start of the judgment period T and every other sampling period The first zero-sequence voltage of the first distribution network, the first zero-sequence voltage of the second distribution network to the first zero-sequence voltage of the Mth distribution network collected in real time, They are respectively the distribution network at the start of the judgment period T and every other sampling period The first arc extinguishing coil current, the second arc extinguishing coil current to the Mth arc extinguishing coil current collected in real time;

[0010] The first zero-sequence voltage matrix U of the distribution network 01 Substitute all the data in into the following formula (3) to calculate the first zero-sequence voltage change rate of the distribution network:

[0011] (3)

[0012] In formula (3), is the first zero-sequence voltage matrix U of the distribution network 01 The ath element in is the The rate of change of

[0013] The M-1 first zero-sequence voltage change rates calculated according to formula (3) form the first zero-sequence voltage change rate matrix of the distribution network: , as shown in the following formula (4),

[0014] (4)

[0015] Step 2: Substitute the first zero-sequence voltage matrix U of the distribution network 01 , the arc suppression coil current matrix I L and the first zero-sequence voltage change rate matrix of the distribution network Substituting into the following formula (5), we can obtain M-1 fault judgment quantities:

[0016] (5)

[0017] In formula (5), and are respectively the total capacitance to ground and the total conductance to ground of the distribution network;

[0018] The M-1 fault judgment quantities calculated by the formula (5) are used as the ordinate, and the time corresponding to the M-1 and the fault judgment ability is used as the abscissa to draw a smooth curve, which is defined as the fault judgment curve;

[0019] If the fault judgment curves are all within the positive and negative first fault judgment thresholds, it indicates that no single-phase grounding fault occurs within the judgment period T, then return to step 1 to continue monitoring the distribution network;

[0020] If the fault judgment curve has a portion exceeding the first positive and negative fault judgment thresholds, it indicates that a single-phase grounding fault has occurred within the judgment period T. At this time, the time corresponding to the point at which the fault judgment curve first exceeds the first positive and negative fault judgment thresholds is recorded, and it is defined as the start time t0 of the single-phase grounding fault, and the following step 3 is continued;

[0021] Step 3: From the start time of the single-phase ground fault Start, every sampling period The zero-sequence voltage of the distribution network and the zero-sequence current of n feeders are collected once in real time, and a total of N collections are performed and the collected zero-sequence voltage of the distribution network and the zero-sequence current of n feeders are collected to form a second zero-sequence voltage matrix U of the distribution network. 02 and zero-sequence current matrix I0, as shown in equations (6) and (7) respectively:

[0022] (6)

[0023] In formula (6), They are respectively the distribution network at the time when the single-phase grounding fault starts Start every other sampling period The second zero-sequence voltage of the first distribution network, the second zero-sequence voltage of the second distribution network to the second zero-sequence voltage of the Nth distribution network collected in real time;

[0024] (7)

[0025] In formula (7), They are the first feeder of the n feeders of the distribution network, starting from the time t0 when the single-phase grounding fault starts, and every other sampling period The first zero-sequence current of the first feeder, the second zero-sequence current of the first feeder to the Nth zero-sequence current of the first feeder collected in real time; The second feeder of the n feeders of the distribution network is respectively the sampling period of every sampling period from the start time t0 of the single-phase grounding fault The first zero-sequence current of the second feeder, the second zero-sequence current of the second feeder to the Nth zero-sequence current of the second feeder collected in real time; , ,…arrive They are respectively the nth feeder among the n feeders of the distribution network, starting from the start time t0 of the single-phase grounding fault, and every other sampling period The first zero-sequence current of the nth feeder, the second zero-sequence current of the nth feeder, and the Nth zero-sequence current of the nth feeder collected in real time;

[0026] Step 4: Substitute the second zero-sequence voltage matrix U of the distribution network 02 Substitute all the data in into the following formula (8) to calculate the second zero-sequence voltage change rate of the distribution network:

[0027] (8)

[0028] In formula (8), is the second zero-sequence voltage matrix U of the distribution network 02 The jth element in is the The rate of change of

[0029] The N-1 second zero-sequence voltage change rates calculated according to formula (8) form the distribution network second zero-sequence voltage change rate matrix , as shown in the following formula (9),

[0030] (9)

[0031] Step 5: The second zero-sequence voltage matrix U of the distribution network 02 and the second zero-sequence voltage change rate matrix To preprocess all the data of the first N-1 columns in the zero-sequence current matrix I0, the preprocessing formula is shown as follows (10):

[0032] (10)

[0033] In formula (10), is the natural unbalanced current of the kth feeder among the n feeders of the distribution network when the jth zero-sequence current is collected in real time; and are respectively the grounding conductance and the grounding capacitance of the kth feeder among the n feeders of the distribution network;

[0034] The N-1 pre-processed zero-sequence currents of the n feeders of the distribution network are collected to form a pre-processed zero-sequence current sequence of the n feeders, as shown in the following equation (11):

[0035] (11)

[0036] Taking the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders in the formula (11) as the ordinate, and taking the acquisition time corresponding to the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders as the abscissa, draw n smooth curves, which are defined as the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve in sequence;

[0037] Substitute the first fault line judgment curve, the second fault line judgment curve and the nth fault line judgment curve into the following formula (12) for judgment:

[0038] (12)

[0039] In formula (12), is the vth fault line judgment curve among the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve; is the second fault judgment threshold;

[0040] The distribution network feeder corresponding to the fault line judgment curve that satisfies the above formula (12) is a normal line; the distribution network feeder corresponding to the fault line judgment curve that does not satisfy the above formula (12) is a fault line.

[0041] Beneficial effects of the invention: The invention proposes a line positioning method for single-phase grounding faults in a distribution network, which uses signal preprocessing to amplify the difference between the faulty feeder and the normal feeder, and then sensitively selects the faulty line. The line where the single-phase grounding fault occurs can be quickly and accurately positioned, greatly improving the safety of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention is a flow chart of a line locating method for a single-phase grounding fault in a distribution network.

[0043] Figure 2 It is a simulation model diagram of the distribution network feeder in an embodiment of the present invention.

[0044] Figure 3 It is a schematic diagram of a fault judgment curve drawn in an embodiment of the present invention.

[0045] Figure 4 It is a schematic diagram of a fault line judgment curve drawn in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following is a further description of a line location method for a single-phase grounding fault in a distribution network according to the present invention in conjunction with the accompanying drawings and specific embodiments.

[0047] Example

[0048] In this embodiment, a method for locating a line of a single-phase grounding fault in a distribution network is provided. Figure 1 As shown, the following steps are included:

[0049] Step 1: Set the judgment period T of the single-phase grounding fault in the distribution network. Within a judgment period T, every other sampling period The zero-sequence voltage of the primary distribution network and the current flowing into the arc suppression coil are collected in real time, and a total of M collections are performed. The collected zero-sequence voltage of the distribution network and the current flowing into the arc suppression coil are collected to form the first zero-sequence voltage matrix U of the distribution network. 01 and arc suppression coil current matrix I L , as shown in the following equations (1) and (2),

[0050] (1)

[0051] (2)

[0052] In formula (1) and formula (2), They are respectively the distribution network at the beginning of the judgment period T and every sampling period The first zero-sequence voltage of the first distribution network, the first zero-sequence voltage of the second distribution network to the first zero-sequence voltage of the Mth distribution network collected in real time, They are respectively the distribution network at the beginning of the judgment period T and every sampling period The first arc extinguishing coil current, the second arc extinguishing coil current to the Mth arc extinguishing coil current collected in real time;

[0053] The first zero-sequence voltage matrix U of the distribution network 01 Substitute all the data in into the following formula (3) to calculate the first zero-sequence voltage change rate of the distribution network:

[0054] (3)

[0055] In formula (3), is the first zero-sequence voltage matrix U of the distribution network 01 The ath element in yes The rate of change of

[0056] The M-1 first zero-sequence voltage change rates calculated according to formula (3) form the first zero-sequence voltage change rate matrix of the distribution network: , as shown in the following formula (4),

[0057] (4)

[0058] Step 2: Substitute the first zero-sequence voltage matrix U of the distribution network 01 , arc suppression coil current matrix IL And the first zero-sequence voltage change rate matrix of the distribution network Substituting into the following formula (5), we can obtain M-1 fault judgment quantities:

[0059] (5)

[0060] In formula (5), and They are the total capacitance and conductance to ground of the distribution network respectively;

[0061] The M-1 fault judgment quantities calculated by formula (5) are used as the ordinate, and the time corresponding to M-1 and the fault judgment force is used as the abscissa. A smooth curve is drawn, which is defined as the fault judgment curve.

[0062] If the fault judgment curves are all within the positive and negative first fault judgment thresholds, it indicates that no single-phase grounding fault occurs within the judgment period T, then return to step 1 to continue monitoring the distribution network;

[0063] If the fault judgment curve has a part exceeding the first positive and negative fault judgment threshold, it indicates that a single-phase grounding fault has occurred within the judgment period T. At this time, the time corresponding to the point at which the fault judgment curve first exceeds the first positive and negative fault judgment threshold is recorded, and it is defined as the start time t0 of the single-phase grounding fault, and the following step 3 is continued;

[0064] Step 3: From the start time of single-phase ground fault Start, every sampling period The zero-sequence voltage of the primary distribution network and the zero-sequence current of n feeders are collected in real time, and a total of N collections are performed and the collected zero-sequence voltage of the distribution network and the zero-sequence current of n feeders are collected to form the second zero-sequence voltage matrix U of the distribution network. 02 and zero-sequence current matrix I0, as shown in equations (6) and (7) respectively:

[0065] (6)

[0066] In formula (6), They are the distribution network at the beginning of the single-phase grounding fault Start every other sampling period The second zero-sequence voltage of the first distribution network, the second zero-sequence voltage of the second distribution network to the second zero-sequence voltage of the Nth distribution network collected in real time;

[0067] (7)

[0068] In formula (7), They are the first feeder of the n feeders in the distribution network, starting from the time t0 when the single-phase grounding fault starts, and every other sampling period The first zero-sequence current of the first feeder, the second zero-sequence current of the first feeder to the Nth zero-sequence current of the first feeder collected in real time; They are the second feeder of the n feeders in the distribution network, starting from the time t0 when the single-phase grounding fault starts, and every other sampling period The first zero-sequence current of the second feeder, the second zero-sequence current of the second feeder to the Nth zero-sequence current of the second feeder collected in real time; , ,…arrive They are the nth feeder of the n feeders in the distribution network, starting from the time t0 when the single-phase grounding fault starts, and every sampling period The first zero-sequence current of the nth feeder, the second zero-sequence current of the nth feeder, and the Nth zero-sequence current of the nth feeder collected in real time;

[0069] Step 4: Substitute the second zero-sequence voltage matrix U of the distribution network 02 Substitute all the data in into the following formula (8) to calculate the second zero-sequence voltage change rate of the distribution network:

[0070] (8)

[0071] In formula (8), is the second zero-sequence voltage matrix U of the distribution network 02 The jth element in yes The rate of change of

[0072] The N-1 second zero-sequence voltage change rates calculated according to formula (8) form the distribution network second zero-sequence voltage change rate matrix , as shown in the following formula (9),

[0073] (9)

[0074] Step 5: Use the second zero-sequence voltage matrix U of the distribution network 02 and the second zero-sequence voltage change rate matrix To preprocess all the data of the first N-1 columns in the zero-sequence current matrix I0, the preprocessing formula is shown as follows (10):

[0075] (10)

[0076] In formula (10), It is the natural unbalanced current of the kth feeder among the n feeders of the distribution network when the jth zero-sequence current is collected in real time; and are the grounding conductance and grounding capacitance of the kth feeder among the n feeders of the distribution network;

[0077] The N-1 pre-processed zero-sequence currents of the n feeders of the distribution network are collected to form the pre-processed zero-sequence current sequence of the n feeders, as shown in the following equation (11):

[0078] (11)

[0079] With the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders in formula (11) as the ordinate, and with the acquisition time corresponding to the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders as the abscissa, n smooth curves are drawn, which are defined as the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve in sequence;

[0080] Substitute the first fault line judgment curve, the second fault line judgment curve and the nth fault line judgment curve into the following formula (12) for judgment:

[0081] (12)

[0082] In formula (12), is the vth fault line judgment curve among the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve; is the second fault judgment threshold;

[0083] The distribution network feeder corresponding to the fault line judgment curve that satisfies the above formula (12) is a normal line; the distribution network feeder corresponding to the fault line judgment curve that does not satisfy the above formula (12) is a fault line.

[0084] The following uses MATLAB / Simulink simulation to verify the line selection method for single-phase grounding fault proposed in the present invention. The simulation model is a 10kV medium-voltage power grid with three feeders, such as Figure 2 The zero-sequence parameters of each feeder are shown in Table 1. The arc suppression coil works in the overcompensation state of 15%, and the size is 0.2196H. At 0.13s, a single-phase grounding fault with a grounding resistance of 8000Ω occurs in phase A of line 1.

[0085]

[0086] Table 1

[0087] Verification of fault line selection method: Starting from 0s, the zero-sequence voltage and arc suppression coil current of the distribution network are collected. The sampling time is 0.08ms, and every 0.02s, it is determined whether the system has a single-phase grounding fault. The collected zero-sequence voltage and arc suppression coil current are used to calculate the waveform of the fault judgment curve, such as Figure 3As shown in the figure, before 0.12s, the system was judged to be faulty. In the period of 0.12-0.14s, the curve exceeded the threshold, indicating that a single-phase grounding fault occurred in the system during this period. At the same time, the time when the threshold was exceeded for the first time was 0.13s, indicating that the system fault occurred at 0.13s. In the period of 0.13s to 0.18s, the system zero-sequence voltage and zero-sequence current of the three lines were collected. The sampling time was 0.08ms. After the zero-sequence current was preprocessed, the preprocessed zero-sequence current waveform was obtained, as shown in Figure 4 As shown, only the zero-sequence current of line 1 after preprocessing exceeds the threshold, which is the fault line.

Claims

1. A method for locating a single-phase ground fault in a distribution network, characterized in that: The following steps are involved: Step 1: Set the judgment period T of the single-phase grounding fault in the distribution network, and every other sampling period within the judgment period T The zero-sequence voltage of the distribution network and the current flowing into the arc suppression coil are collected once in real time, and a total of M collections are performed, and the collected zero-sequence voltage of the distribution network and the current flowing into the arc suppression coil are collected to form the first zero-sequence voltage matrix U of the distribution network. 01 and arc suppression coil current matrix I L , as shown in the following equations (1) and (2), (1) (2) In formula (1) and formula (2), They are respectively the distribution network at the start of the judgment period T and every other sampling period The first zero-sequence voltage of the first distribution network, the first zero-sequence voltage of the second distribution network to the first zero-sequence voltage of the Mth distribution network collected in real time, They are respectively the distribution network at the start of the judgment period T and every other sampling period The first arc extinguishing coil current, the second arc extinguishing coil current to the Mth arc extinguishing coil current collected in real time; The first zero-sequence voltage matrix U of the distribution network 01 Substitute all the data in into the following formula (3) to calculate the first zero-sequence voltage change rate of the distribution network: （3） In formula (3), is the first zero-sequence voltage matrix U of the distribution network 01 The ath element in is the The rate of change of The M-1 first zero-sequence voltage change rates calculated according to formula (3) form the first zero-sequence voltage change rate matrix of the distribution network: , as shown in the following formula (4), （4） Step 2: Substitute the first zero-sequence voltage matrix U of the distribution network 01 , the arc suppression coil current matrix I L and the first zero-sequence voltage change rate matrix of the distribution network Substituting into the following formula (5), we can obtain M-1 fault judgment quantities: （5） In formula (5), and are respectively the total capacitance to ground and the total conductance to ground of the distribution network; The M-1 fault judgment quantities calculated by the formula (5) are used as the ordinate, and the time corresponding to the M-1 and the fault judgment ability is used as the abscissa to draw a smooth curve, which is defined as the fault judgment curve; If the fault judgment curves are all within the positive and negative first fault judgment thresholds, it indicates that no single-phase grounding fault occurs within the judgment period T, then return to step 1 to continue monitoring the distribution network; If the fault judgment curve has a portion exceeding the first positive and negative fault judgment thresholds, it indicates that a single-phase grounding fault has occurred within the judgment period T. At this time, the time corresponding to the point at which the fault judgment curve first exceeds the first positive and negative fault judgment thresholds is recorded, and it is defined as the start time t0 of the single-phase grounding fault, and the following step 3 is continued; Step 3: From the start time of the single-phase ground fault Start, every sampling period The zero-sequence voltage of the distribution network and the zero-sequence current of n feeders are collected once in real time, and a total of N collections are performed and the collected zero-sequence voltage of the distribution network and the zero-sequence current of n feeders are collected to form a second zero-sequence voltage matrix U of the distribution network. 02 and zero-sequence current matrix I0, as shown in equations (6) and (7) respectively: (6) In formula (6), They are respectively the distribution network at the time when the single-phase grounding fault starts Start every other sampling period The second zero-sequence voltage of the first distribution network, the second zero-sequence voltage of the second distribution network to the second zero-sequence voltage of the Nth distribution network collected in real time; (7) In formula (7), They are the first feeder of the n feeders of the distribution network, starting from the time t0 when the single-phase grounding fault starts, and every other sampling period The first zero-sequence current of the first feeder, the second zero-sequence current of the first feeder to the Nth zero-sequence current of the first feeder collected in real time; The second feeder of the n feeders of the distribution network is respectively the sampling period of every sampling period from the start time t0 of the single-phase grounding fault The first zero-sequence current of the second feeder, the second zero-sequence current of the second feeder to the Nth zero-sequence current of the second feeder collected in real time; , ,…arrive They are respectively the nth feeder among the n feeders of the distribution network, starting from the start time t0 of the single-phase grounding fault, and every other sampling period The first zero-sequence current of the nth feeder, the second zero-sequence current of the nth feeder, and the Nth zero-sequence current of the nth feeder collected in real time; Step 4: Substitute the second zero-sequence voltage matrix U of the distribution network 02 Substitute all the data in into the following formula (8) to calculate the second zero-sequence voltage change rate of the distribution network: （8） In formula (8), is the second zero-sequence voltage matrix U of the distribution network 02 The jth element in is the The rate of change of The N-1 second zero-sequence voltage change rates calculated according to formula (8) form the distribution network second zero-sequence voltage change rate matrix , as shown in the following formula (9), （9） Step 5: The second zero-sequence voltage matrix U of the distribution network 02 and the second zero-sequence voltage change rate matrix To preprocess all the data of the first N-1 columns in the zero-sequence current matrix I0, the preprocessing formula is shown as follows (10): （10） In formula (10), is the natural unbalanced current of the kth feeder among the n feeders of the distribution network when the jth zero-sequence current is collected in real time; and are respectively the grounding conductance and the grounding capacitance of the kth feeder among the n feeders of the distribution network; The N-1 pre-processed zero-sequence currents of the n feeders of the distribution network are collected to form a pre-processed zero-sequence current sequence of the n feeders, as shown in the following equation (11): （11） Taking the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders in the formula (11) as the ordinate, and taking the acquisition time corresponding to the N-1 zero-sequence currents after preprocessing in the preprocessed zero-sequence current sequence of the n feeders as the abscissa, draw n smooth curves, which are defined as the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve in sequence; Substitute the first fault line judgment curve, the second fault line judgment curve and the nth fault line judgment curve into the following formula (12) for judgment: （12） In formula (12), is the vth fault line judgment curve among the first fault line judgment curve, the second fault line judgment curve to the nth fault line judgment curve; is the second fault judgment threshold; The distribution network feeder corresponding to the fault line judgment curve that satisfies the above formula (12) is a normal line; the distribution network feeder corresponding to the fault line judgment curve that does not satisfy the above formula (12) is a fault line.

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