Method for judging single-phase earth fault of 10kV line based on elimination of non-fault line

Abstract

The invention discloses a 10kV line single-phase earth fault distinguishing method based on elimination of non-fault lines, comprising the following steps: within the initial time when a single-phase earth fault occurs in an arc suppression coil grounding system, calculating the direction of zero-sequence power in real time and preliminarily judging the position of a fault line by collecting the PMU zero-sequence current and PMU zero-sequence voltage of each measurement point on each 10kV line; and after 2-10 ms of the single-phase earth fault, continuously calculating the zero-sequence power direction of the first measurement point on each non-fault line and the zero-sequence power direction of the first measurement point at the downstream of the fault point of the fault line, and further confirming the non-fault line segments of the non-fault line and the fault line, thereby reversely and indirectly confirming the fault line segment of the fault line. The technical problem that in the prior art, after a fault occurs and an arc suppression coil starts to be started, fault information of a fault line segment of a fault line is submerged by inductive current of the arc suppression coil, and single-phase grounding fault judgment cannot be further carried out 2-10 ms after the fault occurs is solved.

Description

Technical Field

[0001] The invention relates to a method for distinguishing a single-phase grounding fault of a 10kV line based on excluding non-fault lines, which is used in an arc suppression coil grounding system. Based on wide area synchronization information, the method excludes non-fault lines to indirectly confirm faulty lines and faulty line segments. The invention belongs to the technical field of protection and control of power distribution networks. Background Art

[0002] The arc suppression coil grounding system generally adopts an over-compensation scheme. When a single-phase grounding fault occurs on a 10kV distribution line, the arc suppression coil is started about 2 to 10ms after the fault occurs. The inductive current of the arc suppression coil compensates for and exceeds the capacitive current of the fault point, so that the fault information of the fault line is submerged by the inductive current, making it very difficult to further identify the single-phase grounding fault. In the 10kV distribution network system, which is a grounding system through an arc suppression coil, for a single-phase grounding fault on a 10kV distribution line, a wide-area synchronous (PMU) current measuring device is used to collect the A, B, and C phase currents on the line, report them to the dispatching master station or substation end, and calculate the zero-sequence current 3I0 of each line. At the same time, a wide-area synchronous voltage measuring device is installed on the substation bus or the line voltage transformer (PT) to collect the zero-sequence voltage 3U0, report it to the dispatching master station or substation end, and then calculate the zero-sequence power direction. However, this technical solution can only perform short-term (about 2 to 10ms) zero-sequence power direction calculation and single-phase grounding fault judgment. It is impossible to further judge the single-phase grounding fault 2 to 10ms after the fault occurs. As long as the zero-sequence power direction is started, it will remain in the operating state when the zero-sequence voltage exists. This approach is prone to misjudgment and false operation. The present invention proposes a relay protection technology solution for single-phase grounding faults in a 10kV arc suppression coil grounding system, which eliminates non-fault lines based on wide-area synchronization information, indirectly confirms fault lines and fault segments, and thus realizes fault line selection or fault segment positioning. Summary of the invention

[0003] The purpose of the present invention is to eliminate non-fault lines and indirectly confirm fault lines and fault segments based on wide area synchronization information, so as to solve the technical problem that after the arc extinguishing coil starts to start, the inductive current of the arc extinguishing coil drowns the fault information of the fault segment of the fault line, and the single-phase grounding fault cannot be further judged 2 to 10 ms after the fault occurs. The present invention adopts the following technical solutions:

[0004] A method for distinguishing single-phase grounding faults of 10kV lines based on excluding non-fault lines is applied to 6kV-35kV systems whose grounding mode is arc suppression coil grounding system; firstly, a single-phase grounding distinguishing system master station (hereinafter referred to as master station system) is set up at the dispatching master station end or the substation end to collect fault information, calculate the zero-sequence power direction of each measuring point on each outgoing line, and find out the fault line segment and non-fault line segment and non-fault line of the faulty line of the distribution line; on the 10kV line, A, B, C three-phase or zero-sequence current wide-area synchronous PMU type current measuring device (hereinafter referred to as current measuring point) is installed at every other line, and the A, B, C phase PMU current or zero-sequence current of each current measuring point on the line is collected, reported to the master station system, and the PMU zero-sequence current 3I0 is calculated; a PMU type voltage measuring device is installed on the PT of the substation bus or line to collect the PMU zero-sequence voltage 3U0 and report to the master station system;

[0005] The method for determining a single-phase grounding fault of a 10kV line includes the following steps:

[0006] Step 1) Collect zero-sequence voltage PMU data. When the zero-sequence voltage value is greater than the zero-sequence voltage start setting value, enter the single-phase grounding fault judgment program; collect the PMU data of zero-sequence current and zero-sequence voltage at each measuring point of each line, and calculate the zero-sequence power direction within the first 2 to 10 ms of the fault to exclude the fault point that is not upstream (power supply side) of the first measuring point of each line or on the 10 kV busbar of the substation;

[0007] The method for eliminating the fault point that is not upstream of the first measurement point of each line or on the 10kV busbar of the substation is:

[0008] (1) If the zero-sequence power direction of at least one line at the first measuring point of the line is in the positive direction, the grounding point for excluding single-phase grounding fault is not in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation;

[0009] (2) If the calculation results of the zero-sequence power direction of the first measuring point of the line are all in the opposite direction, the grounding point of the single-phase grounding fault is screened out to be in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation;

[0010] Through the above steps ⑴ and ⑵, it is ruled out that the single-phase grounding fault is not in the upstream line section of the first measuring point of each 10kV line or the 10kV busbar of the substation, but in the downstream line section of the first measuring point of a certain 10kV line;

[0011] Step 2) Find out the faulty lines and non-faulty lines;

[0012] The method of sorting the zero-sequence power direction calculation results and determining the faulty lines and non-faulty lines is as follows:

[0013] ⑴ Screen out the faulty lines

[0014] If the direction of the zero-sequence power of the first measuring point on a certain line is calculated to be positive, the line section downstream of the measuring point of the line is selected as the fault line section;

[0015] ⑵Filter out non-faulty lines

[0016] If the direction of the zero-sequence power calculated for the first measurement point on a certain line is in the reverse direction, the line section downstream of the measurement point of the line is selected as the non-fault line section;

[0017] Through the above screening steps, the faulty line and non-faulty line sections are screened out;

[0018] Step 3) Find the fault section and non-fault section of the fault line as follows:

[0019] ⑴ Calculate the zero-sequence power direction of each measuring point on the fault line, set condition ① if the zero-sequence power direction of one or more consecutive measuring points (may be 1 point, or 1 series of points: from the first measuring point of the line to the measuring point before the fault point) is in the positive direction, condition ② the zero-sequence current is greater than the zero-sequence current setting value; if the above two conditions are met, select the downstream line section of the measuring point as the positive direction of the fault;

[0020] (2) Calculate the zero-sequence power direction of each measuring point on the fault line. If it is in the reverse direction, select the downstream line section of the measuring point as the reverse direction of the fault;

[0021] ⑶ Sort the measurement points selected as the positive direction and the reverse direction of the fault. The sorting method is: the zero-sequence power direction on the line is judged to be the positive direction (from the first measurement point of the line to the measurement point before the fault point) and the reverse direction (all measurement points after the fault point) are sorted respectively. The downstream section of the last measurement point in the positive direction to the upstream section of the first measurement point in the reverse direction is the fault point of the line fault. The downstream section of the first measurement point in the reverse direction is the non-fault section of the line. The line section between the last measurement point in the positive direction of the fault and the first measurement point in the reverse direction of the fault is determined to be the fault section of the fault line.

[0022] (4) If the last measurement point in the positive direction of the fault is already the last measurement point of the line, the line section downstream of the measurement point is judged to be the fault line section;

[0023] Step 4) 2 to 10 ms after the fault occurs, continue to collect zero-sequence current at the first measurement point of each non-fault line and non-fault line segment of the fault line, and calculate the zero-sequence power direction with the PMU zero-sequence voltage, and continue to determine whether the above line is a non-fault line;

[0024] 2 to 10 ms after the fault, the arc extinguishing coil starts to start, and the inductive current of the arc extinguishing coil drowns the fault information of the fault line segment of the faulty line, causing the zero-sequence power direction of the faulty line segment of the faulty line to change. The original positive direction indicates a fault, but now the zero-sequence power direction is in the reverse direction, which is an error message, and it is impossible to continue to judge that the line has a fault;

[0025] The reason is that the arc suppression coil grounding system generally adopts overcompensation. The original capacitance current of the entire 10kV system is I C , capacitor current I C The zero-sequence current flows from the fault point to the 10kV busbar through the fault phase of the fault line. For the fault line, the zero-sequence current of the fault section of the fault line is the 10kV system capacitance current minus the capacitance current of the fault section of the fault line. The direction flows from the fault point to the 10kV busbar through the fault line. At this time, the zero-sequence current direction of the fault section of the fault line is opposite to the zero-sequence current direction of the non-fault line, and the zero-sequence power direction is judged to be positive. After the arc extinguishing coil starts to start, the inductance current of the arc extinguishing coil is I L , through the fault point and the fault line fault phase from the fault point to the 10kV bus, and then through the 10kV side of the transformer or the grounding transformer back to the arc extinguishing coil. Since the arc extinguishing coil is an overcompensation method, there is I after the arc extinguishing coil is started L Greater than I C , the current at the ground fault point in the fault section of the fault line is I L -I C , is an inductor current with the inductor component as the main component. L The current flows to the 10kV bus through the fault point of the fault line. At this time, the zero-sequence current of the fault section of the fault line is mainly the composite current of the inductive current of the arc suppression coil and the capacitive current of the fault section of the line before the fault. It is a current dominated by inductive current, and the current direction is from the line fault point to the 10kV bus. Since the zero-sequence current of the fault section of the fault line has changed from capacitive current to inductive current, after the arc suppression coil starts to start, the inductive current of the arc suppression coil overwhelms the fault information dominated by capacitive current of the fault line section of the fault line; because the reference direction of the line current is generally from the bus to the line, the zero-sequence current of the fault section of the fault line is negative inductive current; the negative inductive current is equivalent to the capacitive current, so it is in phase with the capacitive current of the non-fault line, so the zero-sequence power direction is in the opposite direction at this time.

[0026] Therefore, (1) 2 to 10 ms after the fault, continue to collect the PMU zero-sequence current and zero-sequence voltage data of the first measurement point of each non-fault line and the first measurement point of the non-fault line segment of the faulty line, and continue to calculate the zero-sequence power direction. If the zero-sequence power direction is judged to be the reverse direction, it can be confirmed that the above line is a non-fault line or a non-fault line segment of the faulty line;

[0027] The reason is: the capacitive current of the non-fault line and the capacitive current of the non-fault segment of the fault line, because the line capacitive impedance is much larger than the line impedance of the fault segment of the fault line, the inductive current of the arc suppression coil flows from the fault point to the 10kV bus through the fault point and the fault phase of the fault line, and then flows back to the arc suppression coil through the 10kV side of the transformer or the grounding transformer, and almost no current flows through the non-fault line and the non-fault segment of the fault line through the ground capacitance of the non-fault line and the ground capacitance of the non-fault segment of the fault line. Therefore, the capacitive current of the non-fault line and the capacitive current of the non-fault segment of the fault line are not submerged by the inductive current of the arc suppression coil, and can continue to be used for continuous zero-sequence power direction calculation and judgment.

[0028] (2) Continue to collect the PMU zero-sequence voltage and calculate the starting value when the zero-sequence voltage is continuously greater than the zero-sequence voltage;

[0029] The starting setting of zero-sequence voltage is: greater than the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation:

[0030] 3U 0zd =K k *3U bph (1)

[0031] In formula (1), 3U 0zd is the zero-sequence voltage starting value; K k is the reliability factor; 3U bph It is the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation;

[0032] Through the above steps, when the zero-sequence voltage is continuously greater than the starting setting value of the zero-sequence voltage, the lines or line segments originally judged as non-fault lines and non-fault line segments of faulty lines are further judged. If they are still non-fault lines and non-fault line segments of faulty lines, the lines or line segments that have not been identified as non-fault lines or non-fault line segments of faulty lines are reversely confirmed to be faulty lines or faulty line segments;

[0033] Step 5) Determine the nature of the fault line grounding fault:

[0034] When the result of the single-phase grounding fault screened in step 4) is: the duration of the single-phase grounding fault is less than time t, the fault line is judged to be an instantaneous single-phase grounding fault; time t is set to be greater than the disturbance fault time of the distribution line, and is taken as 0.1 to 10 minutes; when the duration of the single-phase grounding fault is greater than time t, the fault line is judged to be a permanent single-phase grounding fault;

[0035] Step 6) Single-phase ground fault judgment program and system return:

[0036] When the measured zero-sequence voltage is less than the return set value of the zero-sequence voltage, it is screened and judged that the single-phase grounding fault disappears, and the single-phase grounding fault judgment program and system return.

[0037] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 1):

[0038] Preferably, the method for collecting zero-sequence current PMU data is: collecting PMU data of three-phase currents A, B, and C collected at each measuring point on each 10kV line, calculating the zero-sequence current at each measuring point of each line, or directly collecting PMU data of zero-sequence current at each measuring point using a zero-sequence current transformer; wherein the zero-sequence current calculated from the three-phase currents A, B, and C is for:

[0039]

[0040] (2) In the formula, is 3 times the zero-sequence current, is the A phase current, is the B phase current, is the C phase current;

[0041] Step 1) requires collecting the zero-sequence current of each measuring point of each line, which is also equal to the sum of the capacitance currents of the three-phase A, B, and C lines to the ground at each measuring point of each line in the event of a single-phase grounding fault, that is, the zero-sequence current is a comprehensive capacitance current.

[0042] Preferably, the method for collecting zero-sequence voltage PMU data is: collecting the three-phase voltage of the PT secondary on the substation bus or line, calculating the zero-sequence voltage in real time, and calculating the zero-sequence voltage from the A, B, and C three-phase voltages. for:

[0043]

[0044] In formula (3), is 3 times the zero-sequence voltage, is the A phase voltage, is the B phase voltage, is the C phase voltage;

[0045] Alternatively, a zero-sequence voltage transformer (PT) is used to directly collect the zero-sequence voltage PMU data of the PT secondary on the substation bus or line.

[0046] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 1:

[0047] If the zero-sequence power direction of the line is positive, it is a faulty line. The method for judging the zero-sequence power direction is: the angle range for judging the positive direction is -180°~0° or 180°~360°. The half angle position of the action area is called the maximum sensitivity angle. The sensitivity angle Φ lm is 90°, and its motion equation is:

[0048]

[0049] If the zero-sequence power direction of the line is judged to be in the reverse direction, it is a non-fault line. The angle range for judging the reverse direction is 0°~180°, and its sensitive angle Φ lm is -90°, and its motion equation is:

[0050]

[0051] The voltage in the zero-sequence power direction calculated in equations (4)-(5) is Calculate the current in the zero-sequence power direction as

[0052] In the above-mentioned method for determining a single-phase grounding fault of a 10kV line based on excluding non-faulty lines, the zero-sequence current setting value in step 3) is greater than the maximum unbalanced current when the master station system collects zero-sequence current under normal operation of the line.

[0053] 3I 0zd =K k 3I 0bph (6)

[0054] In formula (6), 3I 0zd is the zero-sequence current setting value; K k is the reliability coefficient; 3I 0bph It is the maximum unbalanced current when the master station system collects zero-sequence current during normal operation of the line, 3I 0zd Take 2~7A, reliability coefficient K k Take ≥1.5~2.0.

[0055] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 5):

[0056] 3U 0zd Take 5~15V; reliability coefficient K kTake ≥1.5~2.0; the return setting of the zero-sequence voltage is k times the zero-sequence voltage starting setting, and k is 0.5~0.8.

[0057] In the above-mentioned method for determining a single-phase grounding fault of a 10kV line based on excluding non-fault lines, step 3), another method can be used to screen the fault section of the fault line and the non-fault section of the fault line: sort the zero-sequence current of the fault line at this moment, calculate and screen the phase of the zero-sequence current of the upstream measuring point and the downstream measuring point: when the phase of the zero-sequence current of the upstream measuring point and the zero-sequence current of the downstream measuring point appears in reverse phase, screen and select the coverage section of the upstream measuring point and the downstream measuring point as the fault section;

[0058] Note: When a single-phase grounding occurs in the line: the phase of the zero-sequence current will be opposite at the fault point. The fault location can be determined through this fault phenomenon.

[0059] The above-mentioned method for distinguishing single-phase grounding faults of 10kV lines based on excluding non-faulty lines, further, the method for distinguishing the fault phases of the faulty lines is as follows:

[0060] (1) Calculate the A, B, and C three-phase current increments of each measuring point before the fault section of the fault line while screening in step 3) for:

[0061]

[0062] (7) In the formula, They are the A, B, and C phase currents collected after the fault section of the fault line fails. are the A, B, and C phase currents collected before the fault in the fault section of the faulty line, and Φ represents phase A, phase B, and phase C respectively;

[0063] ⑵ Sort the three-phase current increments of each measuring point before calculating the fault section of the faulty line, and determine that the phase with the largest current increment among the three-phase currents is the fault phase.

[0064] The above-mentioned method for determining single-phase grounding fault of 10kV line based on excluding non-fault lines, further, another method is adopted to screen out the fault phase of the faulty line: the A, B, C three-phase voltage data of the PT secondary on the bus or line are used to screen the fault phases. When the voltage of two phases of the three-phase voltage A, B, C is greater than the normal operating voltage and the voltage of one phase is less than m times or less of the normal operating voltage, the phase with reduced voltage is determined to be the fault phase of the faulty line, and m is 70% to 80%.

[0065] The above is another method to determine the fault phase: because the most obvious fault feature of single-phase grounding is the decrease in voltage of one phase of the PT, which can be used to determine the phase difference of single-phase grounding.

[0066] By means of the above scheme, the present invention has at least the following advantages:

[0067] 1. The present invention makes full use of the advantages of wide-area synchronous data, collects the PMU zero-sequence voltage and zero-sequence current data of the entire 10kV power grid, calculates the zero-sequence power direction of the 10kV lines of the entire network, and sorts them, so as to identify the faulty lines; the use of zero-sequence power direction to distinguish grounding faults is very accurate, which is conducive to the safe and stable operation of the power grid.

[0068] 2. The present invention adopts the PMU data of non-fault lines, and continues to calculate the zero-sequence power direction of the first measuring point on each non-fault line and the zero-sequence power direction of the first measuring point downstream of the fault point of the fault line 2 to 10 ms after the single-phase grounding fault occurs. During the period of zero-sequence voltage existence, the non-fault line segments of the non-fault line and the fault line are further confirmed, thereby indirectly confirming the fault line segment of the fault line in reverse, thereby confirming that a single-phase grounding fault occurs in a certain line segment of a certain line. The present invention overcomes the defect that the correct judgment time of the zero-sequence power direction of the fault line can only be 2 to 10 ms after the arc suppression coil device is started, fully utilizes the advantages of big data, makes continuous judgments, and identifies the faulty line, and is simple and easy to implement.

[0069] 3. The present invention gives full play to the advantages of big data. After 2 to 10 ms, the location of the fault line is further determined through reverse identification, and whether it is an instantaneous single-phase grounding fault or a permanent single-phase grounding fault is determined according to the length of the fault time. This overcomes the problem that in the past, when judging a single-phase grounding fault, it was not clear whether the grounding fault was an instantaneous single-phase grounding fault or a permanent single-phase grounding fault.

[0070] 4. The present invention adopts two methods, positive and reverse verification of single-phase grounding, which verify each other and make fault identification more accurate.

[0071] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0073] Figure 1 It is a single line diagram of a 10kV power distribution line of the present invention;

[0074] Figure 2 It is a single-phase grounding determination flow chart of the present invention;

[0075] Figure 3 It is an action characteristic diagram of zero-sequence power direction of the fault line of the present invention;

[0076] Figure 4 It is the action characteristic diagram of the zero-sequence power direction of the non-fault line of the present invention. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0078] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0079] like Figure 1 As shown, in order to solve the above technical problems, the overall idea of ​​the technical solution of the present invention is: in the arc suppression coil grounding system, within the first 2 to 10 ms of a single-phase grounding fault occurring in a distribution line, the single-phase grounding identification system master station located at the dispatching master station end or the substation end collects the PMU zero-sequence current of each measuring point on each 10kV line and the PMU zero-sequence voltage of the PT secondary on the substation bus or line, calculates the zero-sequence power direction in real time, and sorts the calculation results to preliminarily determine the location of the faulty line; 2 to 10 ms after the single-phase grounding fault, continue to calculate the zero-sequence power direction of the first measuring point on each non-fault line and the zero-sequence power direction of the first measuring point downstream of the fault point of the faulty line, and further confirm the non-fault line and the non-fault line segment of the faulty line within the period of zero-sequence voltage existence, thereby indirectly confirming the faulty line segment of the faulty line in reverse, thereby confirming that a single-phase grounding fault has occurred in a certain line segment of a certain line; when the single-phase grounding fault time exceeds the specified time limit, report that a permanent single-phase grounding fault has occurred in a certain line segment of the line.

[0080] The method for distinguishing single-phase grounding fault of 10kV line based on excluding non-faulty lines is applied to the 6kV~35kV system grounding mode through arc suppression coil grounding system; firstly, a single-phase grounding distinguishing system master station (hereinafter referred to as master station system) is set up at the dispatching master station end or substation end to collect fault information, calculate the zero-sequence power direction of each measuring point on each outgoing line, and find out the faulty line segment and non-faulty line segment and non-faulty line of the faulty line of the distribution line; on the 10kV line, A, B, C three-phase or zero-sequence current wide-angle detectors are installed every other line segment. A domain synchronous PMU type current measuring device (referred to as current measuring point) collects the A, B, C phase PMU current or zero-sequence current of each current measuring point on the line, reports to the master station system, and calculates the PMU zero-sequence current 3I0; a PMU type voltage measuring device is installed on the PT of the substation bus or line to collect the PMU zero-sequence voltage 3U0 and report to the master station system; the PMU type current measuring device is an overhead PMU type current measuring device (SGS) and a cable type current measuring device (RCMU), or other PMU type current measuring devices.

[0081] like Figure 2 As shown, the method for determining a single-phase grounding fault of a 10kV line according to the present invention comprises the following steps:

[0082] Step 1) Collect zero-sequence voltage PMU data. When the zero-sequence voltage value is greater than the zero-sequence voltage start setting value, enter the single-phase grounding fault judgment program; collect the PMU data of zero-sequence current and zero-sequence voltage at each measuring point of each line, and calculate the zero-sequence power direction within the first 2 to 10 ms of the fault to exclude the fault point that is not upstream (power supply side) of the first measuring point of each line or on the 10 kV busbar of the substation;

[0083] The method for eliminating the fault point that is not upstream of the first measurement point of each line or on the 10kV busbar of the substation is:

[0084] (1) If the zero-sequence power direction of at least one line at the first measuring point of the line is in the positive direction, the grounding point for excluding single-phase grounding fault is not in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation;

[0085] (2) If the calculation results of the zero-sequence power direction of the first measuring point of the line are all in the opposite direction, the grounding point of the single-phase grounding fault is screened out to be in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation;

[0086] Through the above steps ⑴ and ⑵, it is ruled out that the single-phase grounding fault is not in the upstream line section of the first measuring point of each 10kV line or the 10kV busbar of the substation, but in the downstream line section of the first measuring point of a certain 10kV line;

[0087] Step 2) Find out the faulty lines and non-faulty lines;

[0088] The method of sorting the zero-sequence power direction calculation results and determining the faulty lines and non-faulty lines is as follows:

[0089] ⑴ Screen out the faulty lines

[0090] If the direction of the zero-sequence power of the first measuring point on a certain line is calculated to be positive, the line section downstream of the measuring point of the line is selected as the fault line section;

[0091] ⑵Filter out non-faulty lines

[0092] If the direction of the zero-sequence power calculated for the first measurement point on a certain line is in the reverse direction, the line section downstream of the measurement point of the line is selected as the non-fault line section;

[0093] Through the above screening steps, the faulty line and non-faulty line sections are screened out;

[0094] Step 3) Find the fault section and non-fault section of the fault line as follows:

[0095] ⑴ Calculate the zero-sequence power direction of each measuring point on the fault line, set condition ① if the zero-sequence power direction of one or more consecutive measuring points (may be 1 point, or 1 series of points: from the first measuring point of the line to the measuring point before the fault point) is in the positive direction, condition ② the zero-sequence current is greater than the zero-sequence current setting value; if the above two conditions are met, select the downstream line section of the measuring point as the positive direction of the fault;

[0096] (2) Calculate the zero-sequence power direction of each measuring point on the fault line. If it is in the reverse direction, select the downstream line section of the measuring point as the reverse direction of the fault;

[0097] ⑶ Sort the measurement points selected as the positive direction and the reverse direction of the fault. The sorting method is: the zero-sequence power direction on the line is judged to be the positive direction (from the first measurement point of the line to the measurement point before the fault point) and the reverse direction (all measurement points after the fault point) are sorted respectively. The downstream section of the last measurement point in the positive direction to the upstream section of the first measurement point in the reverse direction is the fault point of the line fault. The downstream section of the first measurement point in the reverse direction is the non-fault section of the line. The line section between the last measurement point in the positive direction of the fault and the first measurement point in the reverse direction of the fault is determined to be the fault section of the fault line.

[0098] (4) If the last measurement point in the positive direction of the fault is already the last measurement point of the line, the line section downstream of the measurement point is judged to be the fault line section;

[0099] Step 4) 2 to 10 ms after the fault occurs, continue to collect zero-sequence current at the first measurement point of each non-fault line and non-fault line segment of the fault line, and calculate the zero-sequence power direction with the PMU zero-sequence voltage, and continue to determine whether the above line is a non-fault line;

[0100] 2 to 10 ms after the fault, the arc extinguishing coil starts to start, and the inductive current of the arc extinguishing coil drowns the fault information of the fault line segment of the faulty line, causing the zero-sequence power direction of the faulty line segment of the faulty line to change. The original positive direction indicates a fault, but now the zero-sequence power direction is in the reverse direction, which is an error message, and it is impossible to continue to judge that the line has a fault;

[0101] The reason is that the arc suppression coil grounding system generally adopts overcompensation. The original capacitance current of the entire 10kV system is I C , capacitor current I C The zero-sequence current flows from the fault point to the 10kV busbar through the fault phase of the fault line. For the fault line, the zero-sequence current of the fault section of the fault line is the 10kV system capacitance current minus the capacitance current of the fault section of the fault line. The direction flows from the fault point to the 10kV busbar through the fault line. At this time, the zero-sequence current direction of the fault section of the fault line is opposite to the zero-sequence current direction of the non-fault line, and the zero-sequence power direction is judged to be positive. After the arc extinguishing coil starts to start, the inductance current of the arc extinguishing coil is I L , through the fault point and the fault line fault phase from the fault point to the 10kV bus, and then through the 10kV side of the transformer or the grounding transformer back to the arc extinguishing coil. Since the arc extinguishing coil is an overcompensation method, there is I after the arc extinguishing coil is started L Greater than I C , the current at the ground fault point in the fault section of the fault line is I L -I C , is an inductor current with the inductor component as the main component. L The current flows to the 10kV bus through the fault point of the fault line. At this time, the zero-sequence current of the fault section of the fault line is mainly the synthesis of the inductive current of the arc suppression coil and the capacitive current of the fault section of the line before the fault. It is a current dominated by inductive current, and the current direction is from the line fault point to the 10kV bus. Since the zero-sequence current of the fault section of the fault line has changed from capacitive current to inductive current, after the arc suppression coil starts to start, the inductive current of the arc suppression coil overwhelms the fault information dominated by capacitive current of the fault line section of the fault line; because the reference direction of the line current is generally from the bus to the line, the zero-sequence current of the fault section of the fault line is negative inductive current; the negative inductive current is equivalent to the capacitive current, so it is in phase with the capacitive current of the non-fault line, so the zero-sequence power direction is in the opposite direction at this time.

[0102] Therefore, (1) 2 to 10 ms after the fault, continue to collect the PMU zero-sequence current and zero-sequence voltage data of the first measurement point of each non-fault line and the first measurement point of the non-fault line segment of the faulty line, and continue to calculate the zero-sequence power direction. If the zero-sequence power direction is judged to be the reverse direction, it can be confirmed that the above line is a non-fault line or a non-fault line segment of the faulty line;

[0103] The reason is: the capacitive current of the non-fault line and the capacitive current of the non-fault segment of the fault line, because the line capacitive impedance is much larger than the line impedance of the fault segment of the fault line, the inductive current of the arc suppression coil flows from the fault point to the 10kV bus through the fault point and the fault phase of the fault line, and then flows back to the arc suppression coil through the 10kV side of the transformer or the grounding transformer, and almost no current flows through the non-fault line and the non-fault segment of the fault line through the ground capacitance of the non-fault line and the ground capacitance of the non-fault segment of the fault line. Therefore, the capacitive current of the non-fault line and the capacitive current of the non-fault segment of the fault line are not submerged by the inductive current of the arc suppression coil, and can continue to be used for continuous zero-sequence power direction calculation and judgment.

[0104] (2) Continue to collect the PMU zero-sequence voltage and calculate the starting value when the zero-sequence voltage is continuously greater than the zero-sequence voltage;

[0105] The starting setting of zero-sequence voltage is: greater than the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation:

[0106] 3U 0zd =K k *3U bph (8)

[0107] In formula (8), 3U 0zd is the zero-sequence voltage starting value; K k is the reliability factor; 3U bph It is the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation;

[0108] Through the above steps, when the zero-sequence voltage is continuously greater than the starting setting value of the zero-sequence voltage, the lines or line segments originally judged as non-fault lines and non-fault line segments of faulty lines are further judged. If they are still non-fault lines and non-fault line segments of faulty lines, the lines or line segments that have not been identified as non-fault lines or non-fault line segments of faulty lines are reversely confirmed to be faulty lines or faulty line segments;

[0109] Step 5) Determine the nature of the fault line grounding fault:

[0110] When the result of the single-phase grounding fault screened in step 4) is: the duration of the single-phase grounding fault is less than time t, the fault line is judged to be an instantaneous single-phase grounding fault; time t is set to be greater than the disturbance fault time of the distribution line, and is taken as 0.1 to 10 minutes; when the duration of the single-phase grounding fault is greater than time t, the fault line is judged to be a permanent single-phase grounding fault;

[0111] Step 6) Single-phase ground fault judgment program and system return:

[0112] When the measured zero-sequence voltage is less than the return set value of the zero-sequence voltage, it is screened and judged that the single-phase grounding fault disappears, and the single-phase grounding fault judgment program and system return.

[0113] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 1):

[0114] Preferably, the method for collecting zero-sequence current PMU data is: collecting PMU data of three-phase currents A, B, and C collected at each measuring point on each 10kV line, calculating the zero-sequence current at each measuring point of each line, or directly collecting PMU data of zero-sequence current at each measuring point using a zero-sequence current transformer; wherein the zero-sequence current calculated from the three-phase currents A, B, and C is for:

[0115]

[0116] (9) In the formula, is 3 times the zero-sequence current, is the A phase current, is the B phase current, is the C phase current;

[0117] Step 1) requires collecting the zero-sequence current of each measuring point of each line, which is also equal to the sum of the capacitance currents of the three-phase A, B, and C lines to the ground at each measuring point of each line in the event of a single-phase grounding fault, that is, the zero-sequence current is a comprehensive capacitance current.

[0118] Preferably, the method for collecting zero-sequence voltage PMU data is: collecting the three-phase voltage of the PT secondary on the substation bus or line, calculating the zero-sequence voltage in real time, and calculating the zero-sequence voltage from the A, B, and C three-phase voltages. for:

[0119]

[0120] In formula (10), is 3 times the zero-sequence voltage, is the A phase voltage, is the B phase voltage, is the C phase voltage;

[0121] Alternatively, a zero-sequence voltage transformer (PT) is used to directly collect the zero-sequence voltage PMU data of the PT secondary on the substation bus or line.

[0122] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 1:

[0123] If the zero-sequence power direction of the line is positive, it is a faulty line. The method for judging the zero-sequence power direction is: the angle range for judging the positive direction is -180°~0° or 180°~360°. The half angle position of the action area is called the maximum sensitivity angle. The sensitivity angle Φ lm is 90°, and its motion equation is:

[0124]

[0125] If the zero-sequence power direction of the line is judged to be in the reverse direction, it is a non-fault line. The angle range for judging the reverse direction is 0°~180°, and its sensitive angle Φ lm is -90°, and its motion equation is:

[0126]

[0127] The voltage in the zero-sequence power direction is calculated as follows: Calculate the current in the zero-sequence power direction as

[0128] In the above-mentioned method for determining a single-phase grounding fault of a 10kV line based on excluding non-faulty lines, the zero-sequence current setting value in step 3) is greater than the maximum unbalanced current when the master station system collects zero-sequence current under normal operation of the line.

[0129] 3I 0zd =K k 3I 0bph (13)

[0130] In formula (13), 3I 0zd is the zero-sequence current setting value; K k is the reliability coefficient; 3I 0bph It is the maximum unbalanced current when the master station system collects zero-sequence current during normal operation of the line, 3I 0zd Take 2~7A, reliability coefficient K k Take ≥1.5~2.0.

[0131] The above method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines, wherein step 5):

[0132] 3U 0zd Take 5~15V; reliability coefficient K kTake ≥1.5~2.0; the return setting of the zero-sequence voltage is k times the zero-sequence voltage starting setting, and k is 0.5~0.8.

[0133] In the above-mentioned method for determining a single-phase grounding fault of a 10kV line based on excluding non-fault lines, step 3), another method can be used to screen the fault section of the fault line and the non-fault section of the fault line: sort the zero-sequence current of the fault line at this moment, calculate and screen the phase of the zero-sequence current of the upstream measuring point and the downstream measuring point: when the phase of the zero-sequence current of the upstream measuring point and the zero-sequence current of the downstream measuring point appears in reverse phase, screen and select the coverage section of the upstream measuring point and the downstream measuring point as the fault section;

[0134] Note: When a single-phase grounding occurs in the line: the phase of the zero-sequence current will be opposite at the fault point. The fault location can be determined through this fault phenomenon.

[0135] The above-mentioned method for distinguishing single-phase grounding faults of 10kV lines based on excluding non-faulty lines, further, the method for distinguishing the fault phases of the faulty lines is as follows:

[0136] (1) Calculate the A, B, and C three-phase current increments of each measuring point before the fault section of the fault line while screening in step 3) for:

[0137]

[0138] (2) In the formula, They are the A, B, and C phase currents collected after the fault section of the fault line fails. are the A, B, and C phase currents collected before the fault in the fault section of the faulty line, and Φ represents phase A, phase B, and phase C respectively;

[0139] ⑵ Sort the three-phase current increments of each measuring point before calculating the fault section of the faulty line, and determine that the phase with the largest current increment among the three-phase currents is the fault phase.

[0140] The above-mentioned method for determining single-phase grounding fault of 10kV line based on excluding non-fault lines, further, another method is adopted to screen out the fault phase of the faulty line: the A, B, C three-phase voltage data of the PT secondary on the bus or line are used to screen the fault phases. When the voltage of two phases of the three-phase voltage A, B, C is greater than the normal operating voltage and the voltage of one phase is less than m times or less of the normal operating voltage, the phase with reduced voltage is determined to be the fault phase of the faulty line, and m is 70% to 80%.

[0141] The above is another method to determine the fault phase: because the most obvious fault feature of single-phase grounding is the decrease in voltage of one phase of the PT, which can be used to determine the phase difference of single-phase grounding.

[0142] The following embodiments take a 10 kV line as an example.

[0143] Embodiment 1:

[0144] Combination Figure 1 , install A, B, C three-phase current or zero-sequence current PMU type current measuring devices at each measuring point 1~n on each 10kV line, collect A, B, C phase current or zero-sequence current on each line, report to the master station system, and calculate zero-sequence current 3I0; at the same time, install PMU type voltage measuring devices on the substation bus or line PT, collect PMU zero-sequence voltage 3U0, and report to the master station system; then calculate the zero-sequence power direction in the master station system, and judge and find the single-phase grounding fault line segment of the distribution line by calculating the zero-sequence power direction of each measuring point on each outgoing line;

[0145] The specific embodiments are as follows:

[0146] The voltage and current in the zero-sequence power direction are calculated as When the zero-sequence power direction of the line is positive, its sensitivity angle Φ lm is 90°, and its motion equation is:

[0147]

[0148] Further calculation yields:

[0149]

[0150] Therefore, when judging the zero-sequence power direction of a single-phase grounding fault, the angle range for the positive direction is -180° to 0° or 180° to 360°.

[0151] When the line is a non-fault line and the zero-sequence power direction is in the opposite direction, its sensitivity angle Φ lm is -90°, and its motion equation is:

[0152]

[0153] Further calculation yields:

[0154]

[0155] Therefore, the angle range for judging the zero-sequence power direction of a single-phase grounding fault is 0° to 180°.

[0156] In the arc suppression coil grounding system, the arc suppression coil starts to work 2 to 10 ms after the initial fault, and the inductive current of the arc suppression coil drowns out the fault information of the fault line segment of the fault line, so that the zero-sequence power direction of the fault line segment of the fault line is judged to be the reverse direction instead of the positive direction of the fault. However, the fault information of the non-fault line and the non-fault line segment of the fault line are not drowned, and can be used to continue fault identification. In the case that the system still has zero-sequence voltage, by judging the zero-sequence power direction of the measuring point on the non-fault line of the substation and the non-fault line of the fault line, the non-fault line and the non-fault line of the fault line are excluded, and the fault line and the fault line segment of the fault line can be indirectly identified.

[0157] Combined with the above judgment method,

[0158] When a phase A ground fault occurs in the downstream line of the third measuring point of the third line, and the collected or calculated zero-sequence voltage exceeds the zero-sequence voltage setting value, the master station system immediately collects the zero-sequence current of each measuring point of each line and calculates the zero-sequence power direction. Within 2 to 10 ms after the initial fault: the zero-sequence power direction of the 1st to 3rd measuring points of the third line is judged to be in the positive direction, the zero-sequence power direction of the 4th to nth measuring points is judged to be in the reverse direction, and the zero-sequence power direction of the first measuring point on the 1st to 2nd and 4th to nth lines is judged to be in the reverse direction. The increments of the three-phase currents A, B, and C of the 1st to 3rd measuring points of the third line are calculated, among which the increment of the current of the phase A is the largest, then the fault is between the 3rd and 4th measuring points of the third line, and the fault phase is the phase A; or judging by the three-phase voltage, if the voltages of the phases B and C increase and the voltage of the phase A is lower than m times the normal operating voltage, the fault phase is judged to be the phase A.

[0159] When the fault occurs 2 to 10 ms later, continue to collect zero-sequence current and zero-sequence voltage at the first measurement point of other non-fault lines of lines 1 to 2 and 4 to n and the fourth measurement point of line 3, continue to calculate the zero-sequence power direction, continue to exclude the above lines as non-fault lines, and confirm the third fault line segment by excluding lines 1 to 2 and 4 to n and the non-fault line segments of the third fault line as non-fault lines. If the single-phase grounding fault lasts for less than t time, report that an instantaneous A-phase grounding fault occurs between the third measurement point and the fourth measurement point of the third line; if the single-phase grounding fault lasts for more than t time, report that a permanent A-phase grounding fault occurs between the third measurement point and the fourth measurement point of the third line;

[0160] When the zero-sequence voltage disappears, the master station system single-phase grounding fault judgment program exits.

[0161] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for distinguishing single-phase grounding faults of 10kV lines based on excluding non-fault lines, which is applied to 6kV-35kV systems and the grounding method is a grounding system through an arc suppression coil; first, a single-phase grounding distinguishing system master station is set up at the dispatching master station or substation end to collect fault information, calculate the zero-sequence power direction of each measuring point on each outgoing line, and find out the faulty line segment and non-fault line segment and non-fault line of the faulty line of the distribution line; on the 10kV line, A, B, C three-phase or zero-sequence current wide-area synchronous PMU type current measuring device is installed at every other line, and the A, B, C phase PMU current or zero-sequence current of each current measuring point on the line is collected, reported to the master station system, and the PMU zero-sequence current 3I0 is calculated; a PMU type voltage measuring device is installed on the PT of the substation bus or line to collect the PMU zero-sequence voltage 3U0 and report to the master station system; It is characterized in that The method for determining a single-phase grounding fault of a 10kV line includes the following steps: Step 1) Collect zero-sequence voltage PMU data. When the zero-sequence voltage value is greater than the zero-sequence voltage start setting value, enter the single-phase ground fault judgment program; collect the PMU data of zero-sequence current and zero-sequence voltage at each measuring point of each line, and calculate the zero-sequence power direction within the first 2 to 10 ms of the fault to exclude the fault point that is not on the upstream power supply side of the first measuring point of each line or the 10 kV busbar of the substation; The method for eliminating the fault point that is not upstream of the first measurement point of each line or on the 10kV busbar of the substation is: (1) If the zero-sequence power direction of at least one line at the first measuring point of the line is in the positive direction, the grounding point for excluding single-phase grounding fault is not in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation; (2) If the calculation results of the zero-sequence power direction of the first measuring point of the line are all in the opposite direction, the grounding point of the single-phase grounding fault is screened out to be in the upstream line section of the first measuring point of all 10kV lines or the 10kV busbar of the substation; Through the above steps ⑴ and ⑵, it is ruled out that the single-phase grounding fault is not in the upstream line section of the first measuring point of each 10kV line or the 10kV busbar of the substation, but in the downstream line section of the first measuring point of a certain 10kV line; Step 2) Find out the faulty lines and non-faulty lines; The method of sorting the zero-sequence power direction calculation results and determining the faulty lines and non-faulty lines is as follows: ⑴ Screen out the faulty lines If the direction of the zero-sequence power of the first measuring point on a certain line is calculated to be positive, the line section downstream of the measuring point of the line is selected as the fault line section; ⑵Filter out non-faulty lines If the direction of the zero-sequence power calculated for the first measurement point on a certain line is in the reverse direction, the line section downstream of the measurement point of the line is selected as the non-fault line section; Through the above screening steps, the faulty line and non-faulty line sections are screened out; Step 3) Find the fault section and non-fault section of the fault line as follows: ⑴ Calculate the zero-sequence power direction of each measuring point on the fault line, set condition ① if the zero-sequence power direction of one or more consecutive measuring points (may be 1 point, or 1 series of points: from the first measuring point of the line to the measuring point before the fault point) is in the positive direction, condition ② the zero-sequence current is greater than the zero-sequence current setting value; if the above two conditions are met, select the downstream line section of the measuring point as the positive direction of the fault; (2) Calculate the zero-sequence power direction of each measuring point on the fault line. If it is in the reverse direction, select the downstream line section of the measuring point as the reverse direction of the fault; ⑶ Sort the measurement points selected as the positive direction and the reverse direction of the fault. The sorting method is: the zero-sequence power directions on the line are sorted as the positive direction and the reverse direction respectively. The downstream section of the last measurement point in the positive direction to the upstream section of the first measurement point in the reverse direction is the fault point of the line fault. The downstream section of the first measurement point in the reverse direction is the non-fault section of the line. The line section between the last measurement point in the positive direction of the fault and the first measurement point in the reverse direction of the fault is determined to be the fault section of the fault line. (4) If the last measurement point in the positive direction of the fault is already the last measurement point of the line, the line section downstream of the measurement point is judged to be the fault line section; Step 4) 2 to 10 ms after the fault occurs, continue to collect zero-sequence current at the first measurement point of each non-fault line and non-fault line segment of the fault line, and calculate the zero-sequence power direction with the PMU zero-sequence voltage to continue to determine whether the above line is a non-fault line; the method is as follows: (1) 2 to 10 ms after the fault, since the capacitive current of the faulty line and the capacitive current of the non-fault segment of the faulty line are not overwhelmed by the inductive current of the arc suppression coil, the PMU zero-sequence current and zero-sequence voltage data of the first measuring point of each non-faulty line and the first measuring point of the non-fault segment of the faulty line are continuously collected, and the zero-sequence power direction calculation is continuously performed. If the zero-sequence power direction is judged to be in the reverse direction, it can be confirmed that the above-mentioned line is a non-faulty line or a non-fault segment of the faulty line; (2) Continue to collect the PMU zero-sequence voltage and calculate the starting value when the zero-sequence voltage is continuously greater than the zero-sequence voltage; The starting setting of zero-sequence voltage is: greater than the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation: 3U 0zd =K k *3U bph (1) In formula (1), 3U 0zd is the zero-sequence voltage starting value; K k is the reliability factor; 3U bph It is the maximum unbalanced voltage value when the master station system collects zero-sequence voltage during normal operation; Through the above steps, when the zero-sequence voltage is continuously greater than the starting setting value of the zero-sequence voltage, the lines or line segments originally judged as non-fault lines and non-fault line segments of faulty lines are further judged. If they are still non-fault lines and non-fault line segments of faulty lines, the lines or line segments that have not been identified as non-fault lines or non-fault line segments of faulty lines are reversely confirmed to be faulty lines or faulty line segments; Step 5) Determine the nature of the fault line grounding fault: When the result of the single-phase grounding fault screened in step 4) is: the duration of the single-phase grounding fault is less than time t, the fault line is judged to be an instantaneous single-phase grounding fault; time t is set to be greater than the disturbance fault time of the distribution line, and is taken as 0.1 to 10 minutes; when the duration of the single-phase grounding fault is greater than time t, the fault line is judged to be a permanent single-phase grounding fault; Step 6) Single-phase ground fault judgment program and system return: When the measured zero-sequence voltage is less than the return set value of the zero-sequence voltage, it is screened and judged that the single-phase grounding fault disappears, and the single-phase grounding fault judgment program and system return.

2. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: Wherein step 1): The method for collecting zero-sequence current PMU data is: collect the PMU data of the three-phase currents A, B, and C collected at each measuring point on each 10kV line, calculate the zero-sequence current at each measuring point on each line, or use a zero-sequence current transformer to directly collect the PMU data of the zero-sequence current at each measuring point; the zero-sequence current calculated from the three-phase currents A, B, and C for: (2) In the formula, is 3 times the zero-sequence current, is the A phase current, is the B phase current, is the C phase current; Step 1) requires collecting the zero-sequence current of each measuring point of each line, which is also equal to the sum of the capacitance currents of the three-phase lines A, B, and C to the ground of each measuring point of each line in the case of a single-phase grounding fault, that is, the zero-sequence current is a comprehensive capacitance current; The method for collecting zero-sequence voltage PMU data is: collect the three-phase voltage of the PT secondary on the substation bus or line, calculate the zero-sequence voltage in real time, and calculate the zero-sequence voltage from the A, B, and C three-phase voltages. for: In formula (3), is 3 times the zero-sequence voltage, is the A phase voltage, is the B phase voltage, is the C phase voltage; Alternatively, use a zero-sequence voltage transformer PT to directly collect the zero-sequence voltage PMU data of the PT secondary on the substation bus or line.

3. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: Step 1: If the zero-sequence power direction of the line is positive, it is a faulty line. The method for judging the zero-sequence power direction is: the angle range for judging the positive direction is -180°~0° or 180°~360°. The half angle position of the action area is called the maximum sensitive angle. The sensitive angle Φ lm is 90°, and its motion equation is: If the zero-sequence power direction of the line is judged to be in the reverse direction, it is a non-fault line. The angle range for judging the reverse direction is 0°~180°, and its sensitive angle Φ lm is -90°, and its motion equation is: The voltage in the zero-sequence power direction calculated in equations (4)-(5) is Calculate the current in the zero-sequence power direction as 4. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: The zero-sequence current setting value in step 3) is greater than the maximum unbalanced current when the master station system collects zero-sequence current under normal line operation. <h2 style=";text-align:left;direction:ltr">3I<h2 style=";text-align:left;direction:ltr"> 0zd <h2 style=";text-align:left;direction:ltr"> =K<h2 style=";text-align:left;direction:ltr"> k <h2 style=";text-align:left;direction:ltr"> 3I<h2 style=";text-align:left;direction:ltr"> 0bph <h2 style=";text-align:left;direction:ltr"> (6) In formula (6), 3I 0zd is the zero-sequence current setting value; K k is the reliability coefficient; 3I 0bph It is the maximum unbalanced current when the master station system collects zero-sequence current during normal operation of the line, 3I 0zd Take 2~7A, reliability coefficient K k Take ≥1.5~2.

0.

5. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: Wherein step 5): 3U 0zd Take 5~15V; reliability coefficient K k Take ≥1.5~2.0; the return setting of the zero-sequence voltage is k times the zero-sequence voltage starting setting, and k is 0.5~0.

8.

6. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: Step 3), another method is used to screen the fault section of the fault line and the non-fault section of the fault line: sort the zero-sequence current of the fault line at this moment, calculate and screen the phase of the zero-sequence current of the upstream measurement point and the downstream measurement point: when the phase of the zero-sequence current of the upstream measurement point and the zero-sequence current of the downstream measurement point appears in reverse phase, the coverage section of the upstream measurement point and the downstream measurement point is screened and selected as the fault section.

7. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: After the fault line is identified, the method for further screening the fault phase of the fault line is as follows: (1) Calculate the A, B, and C three-phase current increments of each measuring point before the fault section of the fault line while screening in step 3) for: (7) In the formula, They are the A, B, and C phase currents collected after the fault section of the fault line fails. are the A, B, and C phase currents collected before the fault in the fault section of the faulty line, and Φ represents phase A, phase B, and phase C respectively; ⑵ Sort the three-phase current increments of each measuring point before calculating the fault section of the faulty line, and determine that the phase with the largest current increment among the three-phase currents is the fault phase.

8. The method for determining a 10kV line single-phase grounding fault based on excluding non-faulty lines according to claim 1, characterized in that: After the fault line is identified, the method for further screening the fault phase of the fault line is as follows: The A, B, and C three-phase voltage data of the PT secondary on the bus or line are used to screen the fault phases. When the voltage of two of the three-phase voltages A, B, and C is greater than the normal operating voltage and the voltage of one phase is less than m times the normal operating voltage or less, the phase with reduced voltage is determined to be the fault phase of the faulty line, and m is 70% to 80%.

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