Neutral point non-effective grounding power distribution network secondary overline fault detection method

Abstract

The invention relates to the technical field of power system fault detection and diagnosis, in particular to a neutral point non-effective grounding power distribution network secondary overline fault detection method, device and equipment and a computer storage medium. According to the method for detecting the secondary overline fault of the neutral point non-effectively grounded power distribution network, an overline different-phase secondary fault equivalent circuit model is established, a fault electrical quantity analytical expression is solved, the characteristics of each stage of the secondary grounding fault under different fault phase sequences are analyzed, and the fault detection accuracy is improved. Corresponding different-phase secondary overline grounding fault detection logic is provided, the accuracy and reliability of the secondary grounding fault detection method are improved, and the method has positive significance in improving the power supply safety of the power distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of power system fault detection and diagnosis, and in particular to a method, device, equipment and computer storage medium for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network. Background Art

[0002] Most medium-voltage distribution networks use neutral-point grounding via arc suppression coils. After a single-phase ground fault occurs, the voltage in the non-fault phase rises, which can easily cause insulation breakdown in the non-fault phase, leading to a secondary two-phase ground fault. When the impedance of the two-phase ground fault loop is small, the large short-circuit current surge triggers overcurrent protection to isolate the faulty feeder. When the two-phase ground fault loop is large, the overcurrent protection fails to operate. Conventional low-current ground fault line selection devices for detecting single-phase ground faults face difficulties in setting the starting threshold and unsuitable detection methods. Consequently, they often fail to detect secondary ground faults, resulting in an inability to quickly and accurately isolate the faulty feeder. They may even mistakenly believe that the correctly selected first-fault feeder was incorrect, triggering subsequent operations such as automatic line switching, leading to serious consequences such as expanding the fault's impact range.

[0003] Experts at home and abroad have conducted valuable research on secondary ground faults. Starting with composite-sequence networks and fault-equivalent zero-sequence networks, employing phasor analysis and solving differential equations, they theoretically analyzed and simulated the steady-state and transient characteristics of electrical quantities associated with secondary ground faults under different neutral-point grounding schemes. They found significant differences in at least one of the modulus or phase angle of the zero-sequence admittance of the fault line before and after the secondary ground fault. Based on this, they proposed a fault detection method. However, this analysis only considers the case where phases B and C are grounded sequentially. In practice, there are also cases where the second ground fault phase precedes the first ground fault phase.

[0004] In summary, the secondary ground fault detection method in the prior art is not comprehensive enough, resulting in poor accuracy and reliability. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem of poor accuracy and reliability of the secondary ground fault detection method in the prior art.

[0006] To solve the above technical problems, the present invention provides a method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point, comprising:

[0007] Construct an equivalent circuit model for cross-line heterogeneous faults;

[0008] Based on the equivalent circuit model, obtaining the electrical quantity change after the first ground fault is transformed into a two-point ground fault according to the electrical characteristic key parameters;

[0009] constructing a fault detection feature based on the electrical quantity change;

[0010] Obtaining key thresholds of the fault detection feature at different fault phase sequences;

[0011] The first single-phase grounding fault line and fault phase of the target distribution network are detected, and the fault detection characteristic value of each line is obtained in real time. The key threshold is used as a judgment criterion to detect subsequent cross-line faults.

[0012] Preferably, the key parameters of the electrical characteristics include the steady-state phase voltage at the first fault point, the steady-state phase voltage at the second fault point, the zero-sequence capacitance of each feeder to the ground, the sum of the zero-sequence capacitance of each feeder to the ground, the equivalent inductance of the arc suppression coil, the transition resistance of two ground faults, and the frequency.

[0013] Preferably, the electrical quantity variation includes a zero-sequence voltage variation, a first fault line zero-sequence current variation, and a second fault line zero-sequence current variation.

[0014] Preferably, constructing a fault detection feature based on the electrical quantity change comprises:

[0015] Constructing a first fault detection feature based on the amplitude change of the zero-sequence current change of the first fault line;

[0016] Constructing a second fault detection feature based on a phase change of a zero-sequence current change of the first fault line;

[0017] The difference in the electrical quantity amplitude change is obtained based on the zero-sequence capacitance of the second fault line to ground, the change in the zero-sequence current of the second fault line, and the change in the zero-sequence voltage, to construct a third fault detection feature;

[0018] The difference in phase change of the electrical quantity is obtained based on the change in zero-sequence current and the change in zero-sequence voltage of the second fault line, and a fourth fault detection feature is constructed.

[0019] Preferably, the step of obtaining the critical thresholds of the fault detection features under different fault phase sequences includes:

[0020] Obtaining a first critical threshold value according to the smaller of a minimum value of the first fault detection feature corresponding to sequential grounding and a minimum value of the first fault detection feature corresponding to reverse-sequence grounding;

[0021] Obtaining a second critical threshold value according to an average value of a sum of a minimum value of the second fault detection feature corresponding to sequential grounding and a maximum value of the second fault detection feature corresponding to reverse-sequence grounding;

[0022] Obtaining a third critical threshold according to a minimum value of a third fault detection feature corresponding to sequential grounding;

[0023] Obtaining a fourth critical threshold value according to a minimum value of the third fault detection feature corresponding to the reverse-sequence grounding;

[0024] Obtaining a fifth critical threshold value according to a minimum value of a fourth fault detection feature corresponding to sequential grounding;

[0025] Obtaining a sixth critical threshold value according to a maximum value of a fourth fault detection feature corresponding to sequential grounding;

[0026] Obtaining a seventh critical threshold value according to a minimum value of the fourth fault detection feature corresponding to the reverse-sequence grounding;

[0027] Obtain the eighth critical threshold value according to the maximum value of the fourth fault detection feature corresponding to the sequence grounding.

[0028] Preferably, the detecting the first single-phase grounding fault line and fault phase of the target distribution network, obtaining the fault detection characteristic value of each line in real time, and detecting the subsequent cross-line fault based on the key threshold as a criterion includes:

[0029] Detect the first single-phase grounding fault line and fault phase of the target distribution network;

[0030] Real-time acquisition of a first fault detection characteristic value of a first single-phase grounding fault line;

[0031] When the first fault detection characteristic value is greater than the first critical threshold, obtaining in real time a second fault detection characteristic value of the first single-phase grounding fault line;

[0032] Obtaining the third fault characteristic value and the fourth fault characteristic value of the remaining lines in real time;

[0033] When the second fault detection characteristic value is greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the third critical threshold, and satisfies that its corresponding fourth fault characteristic value is greater than the fifth critical threshold and less than the sixth critical threshold, it is determined that a secondary ground fault has occurred in the line, and the fault phase is a phase that lags the first fault phase by 120°;

[0034] When the second fault detection characteristic value is not greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the fourth critical threshold, and satisfies that its corresponding fourth fault characteristic value is greater than the seventh critical threshold and less than the eighth critical threshold, it is determined that a secondary ground fault has occurred in the line, and the fault phase is a phase that is 120° ahead of the first fault phase.

[0035] Preferably, when the secondary cross-line fault is detected, the outlet is controlled to trip or issue an alarm.

[0036] The present invention also provides a device for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point, comprising:

[0037] Equivalent circuit construction module, used to construct the equivalent circuit model of cross-line heterogeneous faults;

[0038] An electrical quantity change acquisition module is used to acquire the electrical quantity change after the first ground fault is transformed into a two-point ground fault based on the equivalent circuit model and the key electrical characteristic parameters;

[0039] a fault detection feature construction module, configured to construct a fault detection feature based on the electrical quantity variation;

[0040] A key threshold determination module, used to obtain the key threshold of the fault detection feature under different fault phase sequences;

[0041] The secondary fault detection module is used to detect the first single-phase grounding fault line and fault phase of the target distribution network, and obtain the fault detection characteristic value of each line in real time, and detect the secondary cross-line fault based on the key threshold as the judgment criterion.

[0042] Preferably, the key parameters of the electrical characteristics include the steady-state phase voltage at the first fault point, the steady-state phase voltage at the second fault point, the zero-sequence capacitance of each feeder to the ground, the sum of the zero-sequence capacitance of each feeder to the ground, the equivalent inductance of the arc suppression coil, the transition resistance of two ground faults, and the frequency.

[0043] Preferably, the electrical quantity variation includes a zero-sequence voltage variation, a first fault line zero-sequence current variation, and a second fault line zero-sequence current variation.

[0044] Preferably, the fault detection feature building module includes:

[0045] A first fault detection feature construction unit, configured to construct a first fault detection feature based on an amplitude variation of a zero-sequence current variation of a first fault line;

[0046] A second fault detection feature construction unit is configured to construct a second fault detection feature based on a phase change of a zero-sequence current change of the first fault line;

[0047] a third fault detection feature construction unit, configured to construct a third fault detection feature by obtaining a difference in electrical quantity amplitude change based on a zero-sequence capacitance of the second fault line to ground, a change in a zero-sequence current of the second fault line, and a change in a zero-sequence voltage;

[0048] The fourth fault detection feature construction unit is configured to obtain a difference in electrical quantity phase change based on a zero-sequence current change and a zero-sequence voltage change of the second fault line to construct a fourth fault detection feature.

[0049] Preferably, the key threshold determination module includes:

[0050] a first critical threshold determination unit, configured to obtain a first critical threshold according to the smaller of a minimum value of the first fault detection feature corresponding to sequential grounding and a minimum value of the first fault detection feature corresponding to reverse-sequence grounding;

[0051] a second critical threshold determination unit, configured to obtain the second critical threshold according to an average of a sum of a minimum value of the second fault detection feature corresponding to sequential grounding and a maximum value of the second fault detection feature corresponding to reverse-sequence grounding;

[0052] a third critical threshold determination unit, configured to obtain a third critical threshold according to a minimum value of a third fault detection feature corresponding to sequential grounding;

[0053] a fourth key threshold determination unit, configured to obtain a fourth key threshold according to a minimum value of the third fault detection feature corresponding to the reverse-sequence grounding;

[0054] a fifth key threshold determination unit, configured to obtain a fifth key threshold according to a minimum value of a fourth fault detection feature corresponding to sequential grounding;

[0055] a sixth key threshold determination unit, configured to obtain a sixth key threshold according to a maximum value of a fourth fault detection feature corresponding to sequential grounding;

[0056] a seventh key threshold determination unit, configured to obtain a seventh key threshold according to a minimum value of the fourth fault detection feature corresponding to the reverse-sequence grounding;

[0057] The eighth key threshold determination unit is configured to obtain the eighth key threshold according to the maximum value of the fourth fault detection feature corresponding to the sequential ground fault.

[0058] Preferably, the secondary fault detection module includes:

[0059] A target distribution network detection unit is used to detect the first single-phase grounding fault line and fault phase of the target distribution network;

[0060] A first fault detection characteristic value acquisition unit is used to acquire a first fault detection characteristic value of a line with a first single-phase grounding fault in real time;

[0061] a second fault detection characteristic value acquiring unit, configured to acquire, in real time, a second fault detection characteristic value of the line for the first single-phase grounding fault when the first fault detection characteristic value is greater than the first critical threshold;

[0062] A third fault detection characteristic value acquisition unit, configured to acquire third fault characteristic values of the remaining lines in real time;

[0063] a fourth fault detection characteristic value acquiring unit, configured to acquire fourth fault characteristic values of the remaining lines in real time;

[0064] a first fault judgment unit, configured to determine that a secondary ground fault has occurred in the line, and the fault phase is a phase that lags the first fault phase by 120°, when the second fault detection characteristic value is greater than the second critical threshold, and any line satisfies the conditions that its corresponding third fault characteristic value is greater than the third critical threshold, and its corresponding fourth fault characteristic value is greater than the fifth critical threshold and less than the sixth critical threshold;

[0065] The second fault judgment unit is used to determine that a secondary ground fault has occurred in the line, and the fault phase is a phase that is 120° ahead of the first fault phase, when the second fault detection characteristic value is not greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the fourth critical threshold, and satisfies that its corresponding fourth fault characteristic value is greater than the seventh critical threshold and less than the eighth critical threshold.

[0066] Preferably, the device for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point further comprises:

[0067] The early warning control unit is used to control the outlet to trip or issue an alarm when the secondary cross-line fault is detected.

[0068] The present invention also provides a device for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point, comprising:

[0069] memory for storing computer programs;

[0070] The processor is configured to implement the steps of the above-mentioned method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point when executing the computer program.

[0071] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point are implemented.

[0072] The above technical solution of the present invention has the following advantages over the prior art:

[0073] The method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point described in the present invention establishes an equivalent circuit model for cross-line consecutive faults with different names, solves the analytical expression of the fault electrical quantity, analyzes the characteristics of each stage of secondary grounding faults under different fault phase sequences, and proposes corresponding detection logic for consecutive consecutive cross-line grounding faults with different names, thereby improving the accuracy and reliability of the secondary grounding fault detection method and having positive significance for improving the power supply safety of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0075] Figure 1 This is a flow chart for implementing a method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point provided by the present invention;

[0076] Figure 2 It is a secondary fault zero-sequence equivalent circuit model established in an embodiment of the present invention;

[0077] Figure 3 is ΔI 10 Amplitude change image;

[0078] Figure 4 is ΔI 10 Phase change images;

[0079] Figure 5 is the |ΔB| variation image;

[0080] Figure 6 yes Change image;

[0081] Figure 7 This is a schematic diagram of the improved fault detection logic according to an embodiment of the present invention. DETAILED DESCRIPTION

[0082] The core of the present invention is to provide a method, device, equipment and computer storage medium for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point, which effectively improves the accuracy and reliability of the secondary grounding fault detection method.

[0083] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0084] Please refer to Figure 1 , Figure 1 This is a flowchart of a method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point provided by the present invention; the specific operating steps are as follows:

[0085] S101: Constructing an equivalent circuit model for cross-line heterogeneous faults;

[0086] S102: Based on the equivalent circuit model, obtaining the electrical quantity change after the first ground fault is transformed into a two-point ground fault according to the electrical characteristic key parameters;

[0087] S103: constructing a fault detection feature based on the electrical quantity change;

[0088] S104: Obtaining key thresholds of the fault detection feature under different fault phase sequences;

[0089] S105: Detect the first single-phase grounding fault line and fault phase of the target distribution network, and obtain the fault detection characteristic value of each line in real time, and detect subsequent cross-line faults based on the key threshold as a judgment criterion.

[0090] Based on the above embodiment, this embodiment describes step S101 in detail:

[0091] A cross-line fault with opposite-phase connections is a specific type of fault in distribution networks that involves two different lines and different phases (i.e., opposite-phase connections). This fault typically occurs in distribution systems with ineffective neutral grounding, and has the following characteristics:

[0092] First ground fault: When a single-phase ground fault occurs initially, the fault current is relatively small and may not immediately trigger the protection device to operate.

[0093] Transition resistance: The first ground fault may have a small transition resistance, which means that the fault current will not be large and the protection device may not operate.

[0094] Second high-resistance ground fault: After the first ground fault, due to certain factors in the system (such as voltage increase), a second ground fault may occur on another line, and the resistance of this ground fault is higher (i.e. "high resistance").

[0095] Cross-line fault: The second ground fault occurs on a different line from the first ground fault. This cross-line fault increases the complexity of fault detection and location.

[0096] Different phase: The second ground fault occurs on a conductor with a different phase from the first ground fault. This type of fault with a different phase is called a "different phase" fault.

[0097] Secondary fault: A secondary ground fault is caused by the first ground fault, so it is called a secondary fault. This type of fault may cause more serious grid problems, such as expanding the fault range and increasing grid instability.

[0098] like Figure 2In some embodiments, a cross-line fault scenario involving a low transition resistance ground fault followed by a high-resistance ground fault is selected as the research scenario. This scenario simulates potential fault conditions in actual distribution networks and facilitates more accurate fault analysis and detection.

[0099] Based on the above embodiment, this embodiment describes step S102 in detail:

[0100] In the fault detection method mentioned in the present invention, it is first necessary to calculate the changes in electrical quantities before and after the first ground fault turns into a two-point ground fault based on a series of parameters and an equivalent circuit model;

[0101] In some embodiments, the key electrical characteristic parameters include the first fault point steady-state phase voltage U f1 , steady-state phase voltage U at the second fault point f2 , the zero-sequence capacitance of each feeder to ground C j (j=1,2,3,4,...,n), the sum of the zero-sequence capacitance of each feeder to ground C M , arc suppression coil equivalent inductance L, two ground fault transition resistances R1, R2, frequency w;

[0102] The first and second fault points are typically located on different power feeders, meaning the fault may span different lines, increasing the complexity of fault detection and isolation. In a cross-line, opposite-phase fault, the two fault points may occur on different phases (for example, one on phase A and the other on phase B or C). These different-phase faults are called "opposite-phase" faults. The first fault point typically refers to the initial ground fault, while the second fault point is a secondary ground fault that occurs on another line due to some reason (such as voltage increase) after the initial fault. The first fault point may have a smaller transition resistance (R1), meaning the fault current may be relatively small and may not be sufficient to immediately trigger protective device operation. The second fault point may have a higher transition resistance (R2), which may result in a smaller fault current, making fault detection more difficult. The first and second fault points may have different impacts on the power grid, including voltage fluctuations, increased current, and increased power loss.

[0103] In some embodiments, the electrical quantity variation includes the zero-sequence voltage variation ΔU0, the first fault line zero-sequence current variation ΔI 10 and the change in zero-sequence current of the second fault line ΔI 20 ;

[0104] The first fault line typically refers to the line where the ground fault first occurs. Faults on this line may be caused by external factors (such as lightning strikes or tree contact) or internal factors (such as equipment aging or insulation damage). The fault on the first fault line may be low-impedance or high-impedance, depending on the nature of the fault. This may trigger protective devices, such as overcurrent protection, to isolate the faulty line and prevent the fault from spreading.

[0105] A secondary fault line refers to a secondary ground fault that occurs on another line after the primary fault line due to some reason (such as voltage increase, system instability, etc.). The fault on the secondary fault line may be high-impedance, meaning the fault current may be small and insufficient to immediately trigger the protection device. This high-impedance fault can be more difficult to detect and locate. The failure of the secondary fault line may cause further instability in the power grid and may even trigger a larger-scale power outage or other grid problems.

[0106] The first and second fault lines are located on different power feeders. This cross-line fault complicates fault detection and isolation. In a cross-line, heterogeneous fault, the first and second fault lines may fail on different phases. This type of fault, known as a "heterogeneous phase" fault, further complicates fault analysis. The fault on the first fault line occurred before the fault on the second, and the fault on the second line is a secondary fault caused by the fault on the first line.

[0107] In some embodiments, the present invention combines an equivalent circuit model and calculates the electrical quantity analytical expression of the electrical quantity change after the first ground fault turns into a two-point ground fault based on the key electrical characteristic parameters:

[0108]

[0109]

[0110] Based on the above embodiment, this embodiment describes step S103 in detail:

[0111] In some embodiments, constructing a fault detection feature based on the electrical quantity change includes:

[0112] Based on the amplitude change ΔI of the zero-sequence current change of the first fault line 10 constructing a first fault detection feature;

[0113] Phase change based on the zero-sequence current change of the first fault line constructing a second fault detection feature;

[0114] The difference in the amplitude change of the electrical quantity is obtained based on the zero-sequence capacitance of the second fault line to the ground, the change in the zero-sequence current of the second fault line, and the change in the zero-sequence voltage. constructing a third fault detection feature;

[0115] Obtain the difference in electrical phase change based on the zero-sequence current change and zero-sequence voltage change of the second fault line A fourth fault detection feature is constructed.

[0116] Based on the above embodiment, this embodiment describes step S104 in detail:

[0117] In some embodiments, a sequential ground fault is defined as a second ground fault phase lagging behind the first ground fault phase by 120°, while a reverse-sequence ground fault is defined as a second ground fault phase leading the first ground fault phase by 120°. A detection transition resistance variation range is set, and the variations of the aforementioned electrical quantities are calculated when transition resistances R1 and R2 vary and under different grounding sequences, thereby calculating the critical thresholds of the fault detection feature under different fault phase sequences:

[0118] like Figure 3 , according to the smaller of the minimum value of the first fault detection feature corresponding to the sequential grounding and the minimum value of the first fault detection feature corresponding to the reverse-sequence grounding, obtain the first critical threshold k = a1 × min {min | ΔI 10 | 顺 , min|ΔI 10 | 逆};

[0119] like Figure 4 Since the overall phase change in sequential grounding is higher than that in reverse-sequence grounding, the second critical threshold is obtained based on the average of the sum of the minimum value of the second fault detection feature corresponding to sequential grounding and the maximum value of the second fault detection feature corresponding to reverse-sequence grounding.

[0120] like Figure 5 , since |ΔB| is always greater than zero:

[0121] According to the minimum value of the third fault detection feature corresponding to the sequential grounding, the third critical threshold b1=a2×min(|ΔB|) is obtained. 顺 ;

[0122] According to the minimum value of the third fault detection feature corresponding to the reverse-sequence grounding, the fourth key threshold b2 = a3 × min (|ΔB|) is obtained. 逆 ;

[0123] like Figure 6 , p1, q1, p2, q2 are respectively Variation range setting:

[0124] The fifth critical threshold is obtained according to the minimum value of the fourth fault detection feature corresponding to the sequential grounding

[0125] Obtain the sixth critical threshold value based on the maximum value of the fourth fault detection feature corresponding to the sequential grounding

[0126] Obtain the seventh critical threshold value based on the minimum value of the fourth fault detection feature corresponding to the reverse sequence grounding

[0127] According to the maximum value of the fourth fault detection feature corresponding to your sequence grounding, obtain the eighth key threshold

[0128] In the above formula, a1 to a7 are setting coefficients, which can be adjusted based on the actual situation on site. In a specific embodiment, the recommended values are a1 = 0.9, a2 = 0.9, a3 = 0.9, a4 = 1.1, a5 = 0.9, a6 = 0.9, and a7 = 1.1.

[0129] Based on the above embodiment, this embodiment describes step S105 in detail:

[0130] like Figure 7 In some embodiments, detecting the first single-phase grounding fault line and fault phase of the target distribution network, and obtaining the fault detection characteristic value of each line in real time, and using the key threshold as a criterion to detect subsequent cross-line faults includes:

[0131] Step a: Detect the first single-phase grounding fault line and fault phase of the target distribution network, which can be done by using the traveling wave method or the transient method;

[0132] Step b: Real-time acquisition of the first fault detection characteristic value of the first single-phase grounding fault line; in some embodiments, real-time monitoring of the zero-sequence current and zero-sequence voltage of each line, denoted as I 0j (t), U0(t), and the time of single-phase grounding is t0. If at a certain time t1, the zero-sequence current of the first fault line satisfies |I 0f (t0)-I 0f (t1)|>k, then go to step c;

[0133] Step c: when the first fault detection characteristic value is greater than the first critical threshold, obtaining in real time a second fault detection characteristic value of the first single-phase grounding fault line;

[0134] Step d: When the second fault detection characteristic value is greater than the second critical threshold When the third fault characteristic value and the fourth fault characteristic value of the remaining lines are obtained in real time, when any line meets its corresponding third fault characteristic value |ΔB x | is greater than the third critical threshold, and its corresponding fourth fault characteristic value Greater than the fifth critical threshold and less than the sixth critical threshold |ΔB x |>b1 and Then a secondary ground fault occurs on the line, and the fault phase is the phase that lags behind the first fault phase by 120°;

[0135] Step e: When the second fault detection characteristic value is not greater than the second critical threshold When the third fault characteristic value and the fourth fault characteristic value of the remaining lines are obtained in real time, when any line meets its corresponding third fault characteristic value |ΔB x | is greater than the fourth critical threshold, and its corresponding fourth fault characteristic value Greater than the seventh critical threshold and less than the eighth critical threshold |ΔB x |>b2 and A secondary ground fault occurs on the line, and the fault phase is the phase that leads the first fault phase by 120°.

[0136] Based on the above embodiments, after determining the faulty line and phase, the system will perform corresponding protection actions, such as tripping to isolate the faulty line, or issuing an alarm to notify operation and maintenance personnel for further processing.

[0137] An embodiment of the present invention provides a device for detecting secondary cross-line faults in a distribution network with an ineffectively grounded neutral point. The device may include:

[0138] Equivalent circuit construction module, used to construct the equivalent circuit model of cross-line heterogeneous faults;

[0139] An electrical quantity change acquisition module is used to acquire the electrical quantity change after the first ground fault is transformed into a two-point ground fault based on the equivalent circuit model and the key electrical characteristic parameters;

[0140] a fault detection feature construction module, configured to construct a fault detection feature based on the electrical quantity variation;

[0141] A key threshold determination module, used to obtain the key threshold of the fault detection feature under different fault phase sequences;

[0142] The secondary fault detection module is used to detect the first single-phase grounding fault line and fault phase of the target distribution network, and obtain the fault detection characteristic value of each line in real time, and detect the secondary cross-line fault based on the key threshold as the judgment criterion.

[0143] The neutral point non-effectively grounded distribution network secondary cross-line fault detection device of this embodiment is used to implement the aforementioned neutral point non-effectively grounded distribution network secondary cross-line fault detection method. Therefore, the specific implementation methods of the neutral point non-effectively grounded distribution network secondary cross-line fault detection device can be seen in the embodiment part of the neutral point non-effectively grounded distribution network secondary cross-line fault detection method mentioned above. For example, the equivalent circuit construction module, the electrical quantity change acquisition module, the fault detection feature construction module, the key threshold determination module, and the secondary fault detection module are respectively used to implement steps S101, S102, S103, S104 and S105 in the above-mentioned neutral point non-effectively grounded distribution network secondary cross-line fault detection method. Therefore, its specific implementation methods are as follows:

[0144] Based on the above embodiment, the fault detection feature construction module includes:

[0145] The first fault detection feature construction unit is used to generate a zero-sequence current amplitude change ΔI based on the first fault line zero-sequence current amplitude change ΔI 10 constructing a first fault detection feature;

[0146] The second fault detection feature construction unit is used to construct a phase change of the zero-sequence current of the first fault line based on the phase change of the zero-sequence current of the first fault line. constructing a second fault detection feature;

[0147] The third fault detection feature construction unit is used to obtain the difference in the electrical quantity amplitude change based on the zero-sequence capacitance of the second fault line to ground, the change in the zero-sequence current of the second fault line, and the change in the zero-sequence voltage. constructing a third fault detection feature;

[0148] The fourth fault detection feature construction unit is used to obtain the difference in electrical quantity phase change based on the zero-sequence current change and the zero-sequence voltage change of the second fault line. A fourth fault detection feature is constructed.

[0149] Based on the above embodiment, the key threshold determination module includes:

[0150] The first key threshold determination unit is configured to obtain a first key threshold k=a1×min{min|ΔI} according to the smaller of the minimum value of the first fault detection feature corresponding to the sequential grounding and the minimum value of the first fault detection feature corresponding to the reverse grounding. 10 | 顺 , min|ΔI 10 | 逆};

[0151] The second critical threshold determination unit is configured to obtain the second critical threshold according to the average value of the sum of the minimum value of the second fault detection feature corresponding to the sequential grounding and the maximum value of the second fault detection feature corresponding to the reverse grounding.

[0152] The third critical threshold determination unit is configured to obtain a third critical threshold b1=a2×min(|ΔB|) according to the minimum value of the third fault detection feature corresponding to the sequential grounding. 顺 ;

[0153] The fourth key threshold determination unit is configured to obtain a fourth key threshold b2=a3×min(|ΔB|) according to the minimum value of the third fault detection feature corresponding to the reverse-sequence grounding. 逆 ;

[0154] A fifth key threshold determination unit is configured to obtain a fifth key threshold according to the minimum value of the fourth fault detection feature corresponding to the sequential grounding.

[0155] A sixth key threshold determination unit is configured to obtain a sixth key threshold according to the maximum value of the fourth fault detection feature corresponding to the sequential grounding.

[0156] A seventh key threshold determination unit is used to obtain the seventh key threshold according to the minimum value of the fourth fault detection feature corresponding to the reverse sequence grounding

[0157] The eighth key threshold determination unit is used to obtain the eighth key threshold according to the maximum value of the fourth fault detection feature corresponding to the sequence grounding

[0158] In the above formula, a1 to a7 are setting coefficients, which can be adjusted based on the actual situation on site. In a specific embodiment, the recommended values are a1 = 0.9, a2 = 0.9, a3 = 0.9, a4 = 1.1, a5 = 0.9, a6 = 0.9, and a7 = 1.1.

[0159] Based on the above embodiment, the secondary fault detection module includes:

[0160] The target distribution network detection unit is used to detect the first single-phase grounding fault line and fault phase of the target distribution network, which can adopt the traveling wave method or transient method;

[0161] The first fault detection characteristic value acquisition unit is used to obtain the first fault detection characteristic value of the first single-phase grounding fault line in real time. In some embodiments, the first fault detection characteristic value acquisition unit is used to monitor the zero-sequence current and zero-sequence voltage of each line in real time, which is recorded as I 0j (t), U0(t), and the time of single-phase grounding is t0. If at a certain time t1, the zero-sequence current of the first fault line satisfies |I 0f (t0)-I 0f(t1)|>k, then enter the second fault detection feature value acquisition unit;

[0162] a second fault detection characteristic value acquiring unit, configured to acquire, in real time, a second fault detection characteristic value of the line for the first single-phase grounding fault when the first fault detection characteristic value is greater than the first critical threshold;

[0163] A third fault detection characteristic value acquisition unit, configured to acquire third fault characteristic values of the remaining lines in real time;

[0164] a fourth fault detection characteristic value acquiring unit, configured to acquire fourth fault characteristic values of the remaining lines in real time;

[0165] The first fault judgment unit is used to judge the fault when the second fault detection characteristic value is greater than the second critical threshold And any line satisfies its corresponding third fault characteristic value |ΔB x | is greater than the third critical threshold and satisfies its corresponding fourth fault characteristic value Greater than the fifth critical threshold and less than the sixth critical threshold |ΔB x |>b1 and When , it is determined that a secondary ground fault has occurred on the line, and the fault phase is a phase that lags behind the first fault phase by 120°;

[0166] The second fault judgment unit is used to judge the fault when the second fault detection characteristic value is not greater than the second critical threshold And any line satisfies its corresponding third fault characteristic value |ΔB x | is greater than the fourth critical threshold and satisfies its corresponding fourth fault characteristic value Greater than the seventh critical threshold and less than the eighth critical threshold |ΔB x |>b2 and When , it is determined that a secondary ground fault occurs on the line, and the fault phase is the phase that leads the first fault phase by 120 degrees.

[0167] Based on the above embodiment, the device for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point further includes:

[0168] The early warning control unit is used to control the outlet to trip or issue an alarm when the secondary cross-line fault is detected.

[0169] A specific embodiment of the present invention also provides a device for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point, comprising: a memory for storing a computer program; and a processor for implementing the steps of the above-mentioned method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point when executing the computer program.

[0170] A specific embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for detecting secondary cross-line faults in a distribution network with ineffectively grounded neutral point are implemented.

[0171] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0172] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0173] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0174] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0175] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for detecting secondary cross-line faults in a distribution network with non-effective neutral point grounding, characterized in that: include: Construct an equivalent circuit model for cross-line heterogeneous faults; Based on the equivalent circuit model, obtaining the electrical quantity change after the first ground fault is transformed into a two-point ground fault according to the electrical characteristic key parameters; constructing a fault detection feature based on the electrical quantity change; Obtaining key thresholds of the fault detection feature at different fault phase sequences; The first single-phase grounding fault line and fault phase of the target distribution network are detected, and the fault detection characteristic value of each line is obtained in real time. The key threshold is used as a judgment criterion to detect subsequent cross-line faults.

2. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 1, characterized in that: The key parameters of the electrical characteristics include the steady-state phase voltage at the first fault point, the steady-state phase voltage at the second fault point, the zero-sequence capacitance of each feeder to ground, the sum of the zero-sequence capacitance of each feeder to ground, the equivalent inductance of the arc suppression coil, the transition resistance of two ground faults, and the frequency.

3. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 1, characterized in that: The electrical quantity variation includes a zero-sequence voltage variation, a first fault line zero-sequence current variation, and a second fault line zero-sequence current variation.

4. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 2, characterized in that: The constructing of a fault detection feature based on the electrical quantity change comprises: Constructing a first fault detection feature based on the amplitude change of the zero-sequence current change of the first fault line; Constructing a second fault detection feature based on a phase change of a zero-sequence current change of the first fault line; The difference in the electrical quantity amplitude change is obtained based on the zero-sequence capacitance of the second fault line to ground, the change in the zero-sequence current of the second fault line, and the change in the zero-sequence voltage, to construct a third fault detection feature; The difference in phase change of the electrical quantity is obtained based on the change in zero-sequence current and the change in zero-sequence voltage of the second fault line, and a fourth fault detection feature is constructed.

5. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 4, characterized in that: The key thresholds of obtaining the fault detection features under different fault phase sequences include: Obtaining a first critical threshold value according to the smaller of a minimum value of the first fault detection feature corresponding to sequential grounding and a minimum value of the first fault detection feature corresponding to reverse-sequence grounding; Obtaining a second critical threshold value according to an average value of a sum of a minimum value of the second fault detection feature corresponding to sequential grounding and a maximum value of the second fault detection feature corresponding to reverse-sequence grounding; Obtaining a third critical threshold according to a minimum value of a third fault detection feature corresponding to sequential grounding; Obtaining a fourth critical threshold value according to a minimum value of the third fault detection feature corresponding to the reverse-sequence grounding; Obtaining a fifth critical threshold value according to a minimum value of a fourth fault detection feature corresponding to sequential grounding; Obtaining a sixth critical threshold value according to a maximum value of a fourth fault detection feature corresponding to sequential grounding; Obtaining a seventh critical threshold value according to a minimum value of the fourth fault detection feature corresponding to the reverse-sequence grounding; Obtain the eighth critical threshold value according to the maximum value of the fourth fault detection feature corresponding to the sequence grounding.

6. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 5, characterized in that: The detecting of the first single-phase grounding fault line and fault phase of the target distribution network, obtaining the fault detection characteristic value of each line in real time, and detecting the subsequent cross-line fault based on the key threshold as a criterion includes: Detect the first single-phase grounding fault line and fault phase of the target distribution network; Real-time acquisition of a first fault detection characteristic value of a first single-phase grounding fault line; When the first fault detection characteristic value is greater than the first critical threshold, obtaining in real time a second fault detection characteristic value of the first single-phase grounding fault line; Obtaining the third fault characteristic value and the fourth fault characteristic value of the remaining lines in real time; When the second fault detection characteristic value is greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the third critical threshold, and satisfies that its corresponding fourth fault characteristic value is greater than the fifth critical threshold and less than the sixth critical threshold, it is determined that a secondary ground fault has occurred in the line, and the fault phase is a phase that lags the first fault phase by 120°; When the second fault detection characteristic value is not greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the fourth critical threshold, and satisfies that its corresponding fourth fault characteristic value is greater than the seventh critical threshold and less than the eighth critical threshold, it is determined that a secondary ground fault has occurred in the line, and the fault phase is a phase that is 120° ahead of the first fault phase.

7. The method for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 1, characterized in that: When the secondary cross-line fault is detected, the control outlet is tripped or an alarm is issued.

8. A device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network, characterized in that: include: Equivalent circuit construction module, used to construct the equivalent circuit model of cross-line heterogeneous faults; An electrical quantity change acquisition module is used to acquire the electrical quantity change after the first ground fault is transformed into a two-point ground fault based on the equivalent circuit model and the key electrical characteristic parameters; a fault detection feature construction module, configured to construct a fault detection feature based on the electrical quantity variation; A key threshold determination module, used to obtain the key threshold of the fault detection feature under different fault phase sequences; The secondary fault detection module is used to detect the first single-phase grounding fault line and fault phase of the target distribution network, and obtain the fault detection characteristic value of each line in real time, and detect the secondary cross-line fault based on the key threshold as the judgment criterion.

9. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 8, characterized in that: The key parameters of the electrical characteristics include the steady-state phase voltage at the first fault point, the steady-state phase voltage at the second fault point, the zero-sequence capacitance of each feeder to ground, the sum of the zero-sequence capacitance of each feeder to ground, the equivalent inductance of the arc suppression coil, the transition resistance of two ground faults, and the frequency.

10. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 8, characterized in that: The electrical quantity variation includes a zero-sequence voltage variation, a first fault line zero-sequence current variation, and a second fault line zero-sequence current variation.

11. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 9, characterized in that: The fault detection feature building module includes: A first fault detection feature construction unit, configured to construct a first fault detection feature based on an amplitude variation of a zero-sequence current variation of a first fault line; A second fault detection feature construction unit is configured to construct a second fault detection feature based on a phase change of a zero-sequence current change of the first fault line; a third fault detection feature construction unit, configured to construct a third fault detection feature by obtaining a difference in electrical quantity amplitude change based on a zero-sequence capacitance of the second fault line to ground, a change in a zero-sequence current of the second fault line, and a change in a zero-sequence voltage; The fourth fault detection feature construction unit is configured to obtain a difference in electrical quantity phase change based on a zero-sequence current change and a zero-sequence voltage change of the second fault line to construct a fourth fault detection feature.

12. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 11, characterized in that: The key threshold determination module includes: a first critical threshold determination unit, configured to obtain a first critical threshold according to the smaller of a minimum value of the first fault detection feature corresponding to sequential grounding and a minimum value of the first fault detection feature corresponding to reverse-sequence grounding; a second critical threshold determination unit, configured to obtain the second critical threshold according to an average of a sum of a minimum value of the second fault detection feature corresponding to sequential grounding and a maximum value of the second fault detection feature corresponding to reverse-sequence grounding; a third critical threshold determination unit, configured to obtain a third critical threshold according to a minimum value of a third fault detection feature corresponding to sequential grounding; a fourth key threshold determination unit, configured to obtain a fourth key threshold according to a minimum value of the third fault detection feature corresponding to the reverse-sequence grounding; a fifth key threshold determination unit, configured to obtain a fifth key threshold according to a minimum value of a fourth fault detection feature corresponding to sequential grounding; a sixth key threshold determination unit, configured to obtain a sixth key threshold according to a maximum value of a fourth fault detection feature corresponding to sequential grounding; a seventh key threshold determination unit, configured to obtain a seventh key threshold according to a minimum value of the fourth fault detection feature corresponding to the reverse-sequence grounding; The eighth key threshold determination unit is used to obtain the eighth key threshold according to the maximum value of the fourth fault detection feature corresponding to the sequential grounding.

13. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 12, characterized in that: The secondary fault detection module includes: A target distribution network detection unit is used to detect the first single-phase grounding fault line and fault phase of the target distribution network; A first fault detection characteristic value acquisition unit is used to acquire a first fault detection characteristic value of a line with a first single-phase grounding fault in real time; a second fault detection characteristic value acquiring unit, configured to acquire, in real time, a second fault detection characteristic value of the line for the first single-phase grounding fault when the first fault detection characteristic value is greater than the first critical threshold; A third fault detection characteristic value acquisition unit, configured to acquire third fault characteristic values of the remaining lines in real time; a fourth fault detection characteristic value acquiring unit, configured to acquire fourth fault characteristic values of the remaining lines in real time; a first fault judgment unit, configured to determine that a secondary ground fault has occurred in the line, and the fault phase is a phase that lags the first fault phase by 120°, when the second fault detection characteristic value is greater than the second critical threshold, and any line satisfies the conditions that its corresponding third fault characteristic value is greater than the third critical threshold, and its corresponding fourth fault characteristic value is greater than the fifth critical threshold and less than the sixth critical threshold; The second fault judgment unit is configured to: when the second fault detection characteristic value is not greater than the second critical threshold, and any line satisfies that its corresponding third fault characteristic value is greater than the fourth critical threshold, and When the corresponding fourth fault characteristic value is greater than the seventh critical threshold and less than the eighth critical threshold, it is determined that a secondary ground fault has occurred in the line, and the fault phase is a phase that leads the first fault phase by 120°.

14. The device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network according to claim 8, characterized in that: Also includes: The early warning control unit is used to control the outlet to trip or issue an alarm when the secondary cross-line fault is detected.

15. A device for detecting secondary cross-line faults in a neutral point non-effectively grounded distribution network, characterized in that: include: memory for storing computer programs; A processor is configured to implement the steps of a method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point as claimed in any one of claims 1 to 7 when executing the computer program.

16. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for detecting secondary cross-line faults in a distribution network with non-effectively grounded neutral point as claimed in any one of claims 1 to 7.

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