Electric shock fault detection method, device, equipment, storage medium and program product

Abstract

The invention provides an electric shock fault detection method and device, equipment, a storage medium and a program product. The method comprises the following steps: acquiring residual current and repeated grounding point current of the low-voltage power distribution network in a first measurement period; extracting a first harmonic amplitude of the residual current and a second harmonic amplitude of the repeated grounding point current; determining a transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, a third harmonic amplitude corresponding to the residual current in the second measurement period and a fourth harmonic amplitude corresponding to the repeated grounding point current in the second measurement period; the second measurement period is a previous measurement period of the first measurement period; and detecting whether the low-voltage distribution network has an electric shock fault according to the transformation ratio. The method is used for achieving the effect of improving the electric shock fault detection reliability.

Description

Technical Field

[0001] The present application relates to the technical field of electric shock detection, and in particular, to an electric shock fault detection method, device, equipment, storage medium and program product. Background Art

[0002] With the booming development of the renewable energy industry, the access scale of distributed photovoltaic power sources in low-voltage distribution networks is increasing day by day. Due to the direct electrical connection between distributed photovoltaic power sources, especially non-isolated photovoltaic systems, and low-voltage distribution networks, problems such as common-mode current and harmonic pollution are likely to occur, increasing the risk of electric shock faults. Therefore, an efficient and accurate electric shock fault detection method is of great significance for ensuring the safe operation of low-voltage distribution networks.

[0003] In the related art, the electric shock fault detection of low-voltage distribution networks mainly relies on Residual Current Devices (RCDs). Specifically, an RCD monitors the current changes in a low-voltage distribution network in real time through a current transformer; when the detected residual current (i.e., leakage current) exceeds a preset action threshold, the RCD will quickly cut off the power supply to prevent electric shock accidents.

[0004] However, the reliability of the above-mentioned electric shock fault detection method is relatively low. Summary of the Invention

[0005] Embodiments of the present application provide an electric shock fault detection method, device, equipment, storage medium and program product, so as to achieve the effect of improving the reliability of electric shock fault detection.

[0006] In a first aspect, an embodiment of the present application provides an electric shock fault detection method, including:

[0007] Obtaining the residual current and the repeated grounding point current of a low-voltage distribution network within a first measurement period;

[0008] Extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current;

[0009] Determining a transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within a second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period;

[0010] Detecting whether an electric shock fault has occurred in the low-voltage distribution network according to the transformation ratio.

[0011] In a possible implementation manner, determining a transformation ratio according to a first harmonic amplitude, a second harmonic amplitude, a third harmonic amplitude corresponding to a residual current within a second measurement period, and a fourth harmonic amplitude corresponding to a repetitive grounding point current within the second measurement period includes:

[0012] Calculating a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determining the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio.

[0013] In a possible implementation manner, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current includes:

[0014] When the residual current is greater than a first current threshold and the repetitive grounding point current is greater than a second current threshold, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current.

[0015] In a possible implementation manner, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current includes:

[0016] Solving the effective order of the Prony algorithm by using the singular value decomposition algorithm;

[0017] According to the effective order, using the Prony algorithm to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current.

[0018] In a possible implementation manner, detecting whether an electric shock fault occurs in a low-voltage distribution network according to the transformation ratio includes:

[0019] When the transformation ratio is greater than a transformation ratio threshold, determining that an electric shock fault occurs in the low-voltage distribution network;

[0020] When the transformation ratio is less than or equal to the transformation ratio threshold, determining that no electric shock fault occurs in the low-voltage distribution network.

[0021] In a possible implementation manner, before detecting whether an electric shock fault occurs in a low-voltage distribution network according to the transformation ratio, it further includes:

[0022] Determining the transformation ratio threshold according to the transformation ratio generated by load switching during normal operation of the low-voltage distribution network.

[0023] In a second aspect, an electric shock fault detection device provided by an embodiment of the present application includes:

[0024] An acquisition module, configured to acquire a residual current and a repetitive grounding point current in a low-voltage distribution network within a first measurement period;

[0025] An extraction module, configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current;

[0026] A determining module, configured to determine a transformation ratio according to a first harmonic amplitude, a second harmonic amplitude, a third harmonic amplitude corresponding to a residual current within a second measurement period, and a fourth harmonic amplitude corresponding to a repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period.

[0027] A detection module, configured to detect whether an electric shock fault occurs in a low-voltage distribution network according to the transformation ratio.

[0028] In a possible implementation manner, the determining module is specifically configured to calculate a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio.

[0029] In a possible implementation manner, an extraction module is specifically configured to extract a first harmonic amplitude of the residual current and a second harmonic amplitude of the repeated grounding point current when the residual current is greater than a first current threshold and the repeated grounding point current is greater than a second current threshold.

[0030] In a possible implementation manner, the extraction module is specifically configured to use the singular value decomposition algorithm to solve the effective order of the Prony algorithm;

[0031] According to the effective order, use the Prony algorithm to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0032] In a possible implementation manner, the detection module is specifically configured to determine that an electric shock fault occurs in the low-voltage distribution network when the transformation ratio is greater than a transformation ratio threshold;

[0033] When the transformation ratio is less than or equal to the transformation ratio threshold, it is determined that no electric shock fault occurs in the low-voltage distribution network.

[0034] In a possible implementation manner, the determining module is further configured to determine the transformation ratio threshold according to the transformation ratio generated by load switching during normal operation of the low-voltage distribution network.

[0035] In a third aspect, an embodiment of the present application provides an electronic device, including: a memory, a processor;

[0036] The memory stores computer-executable instructions;

[0037] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the above first aspect and / or various possible implementation manners of the first aspect.

[0038] Fourthly, an embodiment of the present application provides a computer-readable storage medium storing computer-executable instructions, which are used to implement the first aspect and / or various possible implementation manners of the first aspect when executed by a processor.

[0039] Fifthly, an embodiment of the present application provides a computer program product including a computer program, which implements the first aspect and / or various possible implementation manners of the first aspect when executed by a processor.

[0040] The electric shock fault detection method, device, equipment, storage medium and program product provided by the present application obtain the residual current and the repeated grounding point current of the low-voltage distribution network, extract the harmonic amplitude of the residual current and the harmonic amplitude of the repeated grounding point current, determine the transformation ratio according to the harmonic amplitude of the residual current and the harmonic amplitude of the repeated grounding point current, and then determine whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio. Since the transformation ratio of the low-voltage distribution network is used to judge whether an electric shock fault occurs in the low-voltage distribution network, compared with the prior art that only uses the relationship between the residual current and the threshold to detect the electric shock fault, it can effectively reduce the misoperation of the RCD and improve the reliability of the electric shock fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0042] Figure 1 It is a circuit schematic diagram of a low-voltage distribution network provided by the present application;

[0043] Figure 2 It is a flowchart of an electric shock fault detection method provided by the present application;

[0044] Figure 3 It is a schematic diagram of a single-feeder system simulation model provided by the present application;

[0045] Figure 4 It is a schematic diagram of the structure of an electric shock fault detection device provided by the present application;

[0046] Figure 5 It is a schematic diagram of the structure of an electronic device provided by the present application.

[0047] Through the above-mentioned accompanying drawings, the clear embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0049] With the rapid development of the renewable energy industry, the installed capacity of distributed light sources represented by distributed photovoltaics has expanded rapidly. The large-scale access of distributed photovoltaic power sources to low-voltage distribution networks not only promotes the optimization of the energy structure and environmental protection, but also poses new challenges to the safety and stability of power systems. On the one hand, the access of distributed photovoltaic power sources, especially non-isolated photovoltaic systems, is directly electrically connected to the distribution network due to the lack of a transformer, resulting in the common-mode current flowing through the parasitic capacitance being prone to cause frequent false operations of the RCD. On the other hand, the high proportion of grid-connected inverters brings fluctuating high-order harmonic pollution to the low-voltage distribution network, resulting in the waveform characteristics of the leakage current becoming complex. In addition, the double-end power supply phenomenon formed after the photovoltaic power source is connected further increases the technical difficulty of electric shock fault detection and leakage protection.

[0050] At present, the detection methods for electric shock faults in low-voltage distribution networks include detection technologies based on residual current protection devices and fault detection network models based on intelligent algorithms. Traditional AC-type RCDs are mainly applicable to residual currents in the form of power frequency sine waves and are difficult to ensure normal and accurate operation in the face of harmonic pollution introduced by distributed photovoltaic systems. To improve the applicability of detection, the industry has developed B-type RCDs and magnetic modulation current sensors, which can meet the detection requirements for various complex residual currents including alternating current, direct current, and pulsating direct current. However, these protection devices need to set fixed action thresholds and are easily affected by the common-mode current caused by distributed photovoltaic power sources, resulting in frequent false operations. In addition, although the Hall sensor type residual current protector has the advantage of a wide detection range, its anti-interference ability is weak and it is easily affected by external magnetic fields and direct current components. In recent years, electric shock fault detection network models based on deep learning algorithms such as backpropagation neural networks and kernel extreme learning machines have also been proposed, but these models have complex structures, require a large number of data samples, take a long time to train, and the acquisition of data samples is restricted by various conditions such as the photovoltaic access location, access quantity, and geographical location, and do not have universal applicability.

[0051] Based on the above analysis, the present application provides a method, device, equipment, storage medium and program product for detecting electric shock faults. In this method, by obtaining the residual current and the current at the repeated grounding point of the low-voltage distribution network, the transformation ratio is determined according to the harmonic amplitude of the residual current and the harmonic amplitude of the current at the repeated grounding point, so as to judge whether an electric shock fault occurs in the low-voltage distribution network based on the transformation ratio. Compared with the prior art that only uses the residual current to detect electric shock faults, the electric shock fault detection method of the present application can effectively reduce the misoperation of the RCD and more accurately detect the electric shock faults in the low-voltage distribution network.

[0052] The following will specifically describe the technical solutions of the present application and how the technical solutions of the present application solve the above technical problems in detail. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0053] Figure 1 FIG. is a circuit diagram of a two-point repeated grounding system with a photovoltaic power source provided by the present application. As Figure 1 shown, in the low-voltage distribution network, the unbalanced three-phase current caused by load imbalance flows into the ground through the zero-line impedance, the transformer neutral point and the repeated grounding point. The three-phase lines and loads will also generate normal ground leakage currents. In a non-isolated distributed photovoltaic three-phase grid-connected system, the inverter outputs a changing common-mode voltage, thus forming a common-mode current in the loop composed of the parasitic capacitance between the photovoltaic power source and the ground, the inverter, the filter and the low-voltage distribution network. Therefore, the unbalanced three-phase current, the ground leakage current and the common-mode current are inherent components during the normal operation of the system.

[0054] Figure 1 In, Z ALoad 、Z BLoad 、Z CLoad are loads, Z AG 、Z BG 、Z CG are the line-to-ground leakage impedances, Z SG is the repeated grounding point impedance, Z NLine is the zero-line impedance, Z ALine1 、Z BLine1 、Z CLine1 、Z ALine2 、Z BLine2 、Z CLine2 are the three-phase line impedances, Z h is the biological body touch impedance, C PV is the photovoltaic parasitic capacitance to the ground. I A 、I B 、I C 、I N are the three-phase currents and the zero-line current respectively, I AG 、IBG 、I CG are the line-to-ground leakage currents of the line, I ub is the three-phase unbalanced current, I SG is the current at the repeated grounding point, I cm is the common-mode leakage current, I h is the electric shock fault current. The RCD is a residual current protection device. The photovoltaic cells convert the boosted DC into AC through an AC-DC inverter, and then connect to the distribution network after filtering through a filtering device.

[0055] In a 10 / 0.4 kV TN-C-S system, after the three-phase power supply is grounded at the neutral point O of the transformer, the protective earth and neutral line (PEN) is divided into a protective earth line PE and a neutral line N at the user side. During normal operation, the three-phase unbalanced current is generated due to the asymmetric operation of the load, flows through the three-phase line impedance and the zero-line impedance in sequence, and finally flows into the earth through the neutral point O of the transformer and the impedance of the repeated grounding point. The line-to-ground leakage current caused by the line-to-ground leakage impedance flows into the earth through the neutral point O of the transformer. The common-mode current of the non-isolated photovoltaic system is generated by the high-frequency switching action of the inverter, forms a loop through the filtering device, AC-DC converter, boost circuit and the parasitic capacitance of the photovoltaic array to the ground, and finally flows into the earth through the parasitic capacitance and the neutral point O of the transformer. The RCD monitors the residual current of the load branch to ensure that the three-phase unbalanced current, line-to-ground leakage current and common-mode current are within a safe range.

[0056] Three-phase unbalanced current and the current at the repeated grounding point The expressions are:

[0057] (1)

[0058] (2)

[0059] Wherein, in the formula is the impedance of the neutral point of the 10 / 0.4 kV transformer to the ground, is the repeated grounding impedance at the load setting point, is the impedance of the three-phase line and the zero line.

[0060] Three-phase normal line-to-ground leakage current The expression is:

[0061] (3)

[0062] Wherein, 、 、 are the normal line-to-ground leakage currents of phases A, B, and C, , , are the leakage impedances to ground of the line and the load equipment respectively.

[0063] Common-mode current The expression is:

[0064] (4)

[0065] Wherein, is the parasitic capacitance to ground of the photovoltaic power supply, is the common-mode voltage generated on the parasitic capacitance.

[0066] The residual current of the low-voltage distribution substation during normal operation is:

[0067] (5)

[0068] Wherein, the three-phase normal leakage current to ground and the common-mode current flow back to the neutral point of the transformer through shunt one ( ) and shunt two ( , ), so:

[0069] (6)

[0070] In the formula, is the current shunt coefficient.

[0071] The residual current generated when the three-phase load is switched is:

[0072] (7)

[0073] In the formula, , , are the mutation amounts generated by each current respectively.

[0074] The residual current when an electric shock fault occurs is:

[0075] (8)

[0076] In the formula, is the electric shock fault current.

[0077] In this application, the transformation ratio M is defined as the absolute value of the ratio of the change in the harmonic amplitude of the residual current to the change in the harmonic amplitude of the repeated grounding current.

[0078] When the system is operating normally and the load is switched, the transformation ratio is:

[0079] (9)

[0080] When an electric shock fault occurs, the transformation ratio is:

[0081] (10)

[0082] where n represents the harmonic order.

[0083] When the system is operating normally, calculate the transformation ratio generated by load switching , and set the transformation ratio threshold corresponding to the nth harmonic accordingly . When an electric shock fault occurs, due to adding variables in , a mutation occurs, and the value calculated in real time is greater than the threshold , thus determining that an electric shock fault has occurred.

[0084] Figure 2 is a schematic flow chart of an electric shock fault detection method provided by this application. As Figure 2 shown, with the electric shock detection system as the execution subject, the method includes:

[0085] S101. Obtain the residual current and the current at the repeated grounding point in the low-voltage distribution network within the first measurement period.

[0086] In this embodiment, the electric shock detection system can be integrated into the detection module of the RCD to detect electric shock faults for the low-voltage distribution network with distributed photovoltaic multi-point access. Specifically, the electric shock detection system collects the current flowing through the repeated grounding point and the current flowing through the RCD of the unbalanced three-phase current according to a preset measurement period, and obtains the current at the repeated grounding point and the residual current.

[0087] S102. Extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the current at the repeated grounding point.

[0088] In this embodiment, the electric shock detection system can process the residual current and the current at the repeated grounding point respectively through a harmonic analysis algorithm, extract the harmonic components in the current, and obtain the first harmonic amplitude and the second harmonic amplitude.

[0089] S103. Determine the transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the current at the repeated grounding point within the second measurement period.

[0090] where the second measurement period is the previous measurement period of the first measurement period.

[0091] In this embodiment, the electric shock detection system can obtain the residual current harmonic amplitude and the repeated grounding point current harmonic amplitude within the second measurement period from the storage module, and calculate the absolute value of the ratio of the harmonic amplitude change between the two measurement periods.

[0092] S104. Detect whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio.

[0093] In this embodiment, the electric shock detection system can input the transformation ratio into the fault detection algorithm. The algorithm judges whether an electric shock fault occurs in the low-voltage distribution network according to the value of the transformation ratio and in combination with the preset safety standard.

[0094] If an electric shock fault is detected, the electric shock detection system can send an alarm to the operator through the user interface, the alarm module or other communication means, and may trigger automatic power-off or other safety measures.

[0095] The electric shock fault detection method provided in this embodiment realizes high-sensitivity detection and accurate judgment of electric shock faults in the low-voltage distribution network through steps such as extracting harmonic amplitudes, calculating transformation ratios, and judging fault states, providing a strong guarantee for the safe operation of the low-voltage distribution network.

[0096] In a possible implementation manner, when the residual current is greater than the first current threshold and the repeated grounding point current is greater than the second current threshold, the electric shock detection system can extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0097] Specifically, due to factors such as sampling resolution and environmental noise during the actual operation of the power system, the sudden change in the residual current collected by the electric shock detection system and the sudden change in the repeated grounding point current and inevitably contain measurement errors, and when

[0098] are smaller, the influence of the measurement error on the transformation ratio is greater. and Therefore, effective measurement thresholds and and and need to be set for the residual current and the repeated grounding point current. When is greater than the threshold and is greater than the threshold and then extracting the harmonic amplitude and calculating the transformation ratio can further improve the detection accuracy of the electric shock fault.

[0099] Compared with only using the current threshold in the prior art, in this embodiment, a double combination criterion is also formed by combining the transformation ratio threshold. When the line current flows through the RCD, if the threshold conditions under the double combination criterion of the current threshold and the transformation ratio threshold are met, the RCD will act to disconnect the line. When a leakage occurs in the photovoltaic power supply or the load switching causes a large residual current in the distribution area, the residual current and the current at the repeated grounding point will exceed the operating setting value. However, when the criterion condition of the transformation ratio is not met, the RCD will not act to disconnect the line, thereby effectively reducing the misoperation of the RCD. In summary, the method of this embodiment can not only accurately judge the electric shock fault, but also avoid the misoperation caused by load switching.

[0100] Based on the above embodiment, the present application constructs a simulation model of a 400V low-voltage distribution network with distributed photovoltaic access based on the three-layer topological relationship of the distribution area-line-user and the distribution characteristics of the residual current in the distribution area, and selects the human equivalent circuit model of Freiberg as the human electric shock simulation model, as Figure 3 shown.

[0101] Figure 3 In the figure, the model is used to simulate the electric shock characteristics of a distribution network with distributed photovoltaic in a 10 / 0.4kV TN-C-S system. The low-voltage distribution network steps down 10kV to 0.4kV through a transformer T and accesses the bus, connecting a feeder and three load nodes (L1-L3). Among them, the distributed photovoltaic PV1 is directly connected to the bus, and PV2 is connected to the load L3 node. The distributed photovoltaics PV1 and PV2 convert the boosted direct current into alternating current through an AC-DC inverter, and then access the point of common coupling PCC1 and PCC2 after filtering through a filtering device. QF is a relay protection circuit breaker, and the lines Z1-Z6 are all line impedances. The model considers parameters such as line impedance, load impedance, ground leakage impedance, repeated grounding impedance, and photovoltaic parasitic capacitance, and simulates the human contact scenario by setting the impedance of the biological body contact, so as to study the electric shock current characteristics under different photovoltaic penetration rates, three-phase unbalance degrees and other working conditions, evaluate the protection performance of the RCD, and provide data support for the safe design of the distribution network and the photovoltaic grid connection protection.

[0102] Based on the above model, the residual current and the current at the repeated grounding point during normal operation of the distribution area can be obtained.

[0103] Based on the Singular Value Decomposition-Prony (SVD-Prony) algorithm, the harmonic amplitudes of the residual current and the harmonic amplitudes of the current at the repeated grounding point can be extracted.

[0104] In a possible implementation, the specific implementation of step S102 includes:

[0105] S1021. Solve the effective order of the Prony algorithm using the singular value decomposition algorithm.

[0106] S1022. According to the effective order, use the Prony algorithm to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding current.

[0107] Specifically, process the sampling signal (residual current and repetitive grounding current) as:

[0108] (11)

[0109] The sampling signal is the residual current and the repetitive grounding current.

[0110] Construct a matrix based on formula (11) , where is the order of the matrix:

[0111] (12)

[0112] It should be noted that the accuracy of the Prony algorithm depends on the selection of the rank . When the rank is selected too small, it will cause partial omission during parameter extraction; when the rank is selected too large, it will cause information redundancy. Use the noise reduction method based on SVD to obtain the effective order of the Prony algorithm , and the specific process is as follows:

[0113] Based on the noise reduction method of SVD, obtain the singular values of the matrix , and sort them according to size to get:

[0114] (13)

[0115] Among them, and the subsequent singular value values gradually approach 0. Construct a function based on the singular value data and obtain the second derivative. If the following conditions are met, it indicates that the singular values of the matrix change abruptly before and after the critical point , and this point is the demarcation point of the effective rank of the matrix , and thus obtain the effective order of the Prony algorithm.

[0116] (14)

[0117] The calculation process of the Prony algorithm is: Let is the fitting approximate solution of the sampling signal and is composed of any number of exponential functions

[0118] (15)

[0119] (16)

[0120] (17)

[0121] In the formula, N is the number of sampling points, and are both complex numbers, and are the amplitude and phase angle, and are the attenuation factor and frequency, is the time interval, and j is the imaginary unit

[0122] To improve the fitting accuracy, construct and solve the objective function using the least sum of squares:

[0123] (18)

[0124] To solve this non - linear least - squares equation, define the characteristic polynomial:

[0125] (19)

[0126] Combined with formula (15), we get:

[0127] (20)

[0128] Therefore, satisfies the following recurrence difference equation:

[0129] (21)

[0130] Define the error between the true value and the approximate value as , and combined with formula (21), we get:

[0131] (22)

[0132] Then define the error to avoid solving the non - linear equation:

[0133] (23)

[0134] Therefore, the linear matrix equation is obtained:

[0135]

[0136]

[0137]

[0138] (24)

[0139] Solve for the coefficients , ,…, to obtain the roots :[[]]

[0140] (25)

[0141] Substitute into formula (15) to obtain the matrix equation:

[0142] (26)

[0143] Denote the leftmost matrix as , and the least squares solution is:

[0144] (27)

[0145] Finally, obtain the characteristic parameters of the harmonics:

[0146] (28)

[0147] Thus, obtain the harmonic amplitude of the residual current and the harmonic amplitude of the current at the repeated grounding point .

[0148] Furthermore, the expression of the transformation ratio is:

[0149] (29)

[0150] where n is an integer from 2 to 5, representing the harmonic order.

[0151] It should be noted that, compared with traditional harmonic detection algorithms such as wavelet transform and S transform, the Prony algorithm has the characteristics of simultaneously detecting multiple disturbance information and higher frequency resolution, but the Prony algorithm has poor anti-noise ability and requires prior noise reduction processing of the signal.

[0152] In this embodiment, the Prony algorithm can accurately extract the harmonic amplitude information in the residual current and the repeated grounding point current. By extracting the harmonic amplitude information, the electric shock detection system can achieve high-sensitivity detection and accurate judgment of electric shock faults, improve the robustness of electric shock fault detection, and provide a strong guarantee for the safe operation of the power system.

[0153] On this basis, the specific implementation manner of step S103 includes calculating the first difference between the first harmonic amplitude and the third harmonic amplitude, and the second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determining the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio.

[0154] It can be understood that the first difference is , and the second difference is , and the transformation ratio expression is as shown in formula (29).

[0155] In a possible implementation manner, the specific implementation manner of step S104 includes:

[0156] S1041. When the transformation ratio is greater than the transformation ratio threshold, it is determined that an electric shock fault occurs in the low-voltage distribution network;

[0157] S1042. When the transformation ratio is less than or equal to the transformation ratio threshold, it is determined that no electric shock fault occurs in the low-voltage distribution network.

[0158] Specifically, when the harmonic order n of the harmonic amplitude is different, the transformation ratio threshold is different. The transformation ratio being greater than the transformation ratio threshold indicates that the change amount of the residual current increases by the electric shock fault current, that is, an electric shock fault occurs in the low-voltage distribution network.

[0159] Based on the foregoing embodiment, the transformation ratio threshold can be determined according to the transformation ratio generated by load switching during the normal operation of the low-voltage distribution network.

[0160] Threshold is related to the topological structure of the photovoltaic power source and load access in the substation area. Therefore, the corresponding threshold can be set according to the actual system topology, line parameters, and environmental conditions .

[0161] Figure 4 is a schematic structural diagram of an electric shock fault detection device provided by the present application. As Figure 4 shown, the electric shock fault detection device 10 of this embodiment is used to implement the operations corresponding to the electric shock detection system in any of the above method embodiments. The electric shock fault detection device 10 provided in this embodiment includes:

[0162] An acquisition module 11, configured to acquire the residual current and the repeated grounding point current in the low-voltage distribution network during the first measurement period;

[0163] An extraction module 12 is configured to extract a first harmonic amplitude of the residual current and a second harmonic amplitude of the repeated grounding point current;

[0164] A determination module 13 is configured to determine a transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, a third harmonic amplitude corresponding to the residual current within a second measurement period, and a fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period;

[0165] A detection module 14 is configured to detect whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio.

[0166] In a possible implementation manner, the determination module 13 is specifically configured to calculate a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio.

[0167] In a possible implementation manner, the extraction module 12 is specifically configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current when the residual current is greater than a first current threshold and the repeated grounding point current is greater than a second current threshold.

[0168] In a possible implementation manner, the extraction module 12 is specifically configured to use the singular value decomposition algorithm to solve the effective order of the Prony algorithm;

[0169] According to the effective order, use the Prony algorithm to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0170] In a possible implementation manner, the detection module 14 is specifically configured to determine that an electric shock fault occurs in the low-voltage distribution network when the transformation ratio is greater than a transformation ratio threshold;

[0171] When the transformation ratio is less than or equal to the transformation ratio threshold, it is determined that no electric shock fault occurs in the low-voltage distribution network.

[0172] In a possible implementation manner, the determination module 13 is further configured to determine the transformation ratio threshold according to the transformation ratio generated by load switching during normal operation of the low-voltage distribution network.

[0173] The electric shock fault detection device 10 provided in this embodiment can execute the method provided in the above method embodiment, and its implementation principle and technical effect are similar, which will not be elaborated here in this embodiment.

[0174] Figure 5 It is a schematic structural diagram of an electronic device provided in this application. As Figure 5As shown in the figure, the electronic device 20 provided in this embodiment includes: a memory 21 and at least one processor 22. Optionally, the device 20 further includes a communication component 23. Among them, the memory 21, the processor 22, and the communication component 23 are connected through a bus 24.

[0175] In the specific implementation process, at least one processor 22 executes the computer-executable instructions stored in the memory 21, so that at least one processor 22 executes the above-mentioned method.

[0176] For the specific implementation process of the processor 22, reference may be made to the above method embodiment, and its implementation principle and technical effects are similar, so they will not be elaborated here in this embodiment.

[0177] In the above embodiment, it should be understood that the processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in combination with the invention can be directly embodied as being executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

[0178] The memory may include a high-speed random access memory (RAM), and may also include a non-volatile memory (NVM), such as at least one disk memory.

[0179] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0180] This application also provides a computer program product, including a computer program, which implements the above-mentioned method when executed by a processor.

[0181] The present application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above method.

[0182] The above-readable storage medium may be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, a magnetic disk, or an optical disk. The readable storage medium may be any available medium accessible by a general-purpose or special-purpose computer.

[0183] An exemplary readable storage medium is coupled to the processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium may also be part of the processor. The processor and the readable storage medium may be located in an application-specific integrated circuit (ASIC). Of course, the processor and the readable storage medium may also exist as discrete components in a device.

[0184] The division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the couplings or direct couplings or communication connections shown or discussed between each other may be indirect couplings or communication connections through some interfaces, devices, or units, and may be in electrical, mechanical, or other forms.

[0185] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0186] In addition, in each embodiment of the present invention, the functional units may be integrated in a processing unit, or each unit may exist physically alone, or two or more units may be integrated in one unit.

[0187] If a function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The foregoing storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs, etc., various media that can store program codes.

[0188] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions. The foregoing program can be stored in a computer-readable storage medium. When this program is executed, it executes the steps including the above method embodiments; and the foregoing storage medium includes: ROMs, RAMs, magnetic disks, or optical discs, etc., various media that can store program codes.

[0189] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other implementation manners of the present invention. The present invention is intended to cover any variations, uses, or adaptive changes of the present invention. These variations, uses, or adaptive changes follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field of the present invention that are not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for detecting electric shock faults, characterized in that, Including: Obtain the residual current and the repeated grounding point current of the low-voltage distribution network within the first measurement period; Extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current; Determine the transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period; Detect whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio.

2. The method according to claim 1, wherein Determining the transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period includes: Calculate the first difference between the first harmonic amplitude and the third harmonic amplitude, and the second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio.

3. The method according to claim 1, characterized in that, Extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current includes: When the residual current is greater than the first current threshold and the repeated grounding point current is greater than the second current threshold, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

4. The method according to claim 1, wherein Extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current includes: Use the singular value decomposition algorithm to solve the effective order of the Prony algorithm; According to the effective order, use the Prony algorithm to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

5. The method according to claim 1, wherein Detecting whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio includes: When the transformation ratio is greater than the transformation ratio threshold, determine that an electric shock fault occurs in the low-voltage distribution network; When the transformation ratio is less than or equal to the transformation ratio threshold, determine that no electric shock fault occurs in the low-voltage distribution network.

6. The method according to any one of claims 1-5, characterized in that, Before detecting whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio, it further includes: Determine the transformation ratio threshold according to the transformation ratio generated by load switching during the normal operation of the low-voltage distribution network.

7. An electric shock fault detection device, characterized in that, Including: An acquisition module for acquiring the residual current and the repeated grounding point current of the low-voltage distribution network within the first measurement period; An extraction module for extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current; A determination module for determining the transformation ratio according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period; A detection module for detecting whether an electric shock fault occurs in the low-voltage distribution network according to the transformation ratio.

8. An electronic device, characterized in that, Including: A memory, a processor; The memory stores computer execution instructions; The processor executes the computer-executable instructions stored in the memory, such that the processor performs the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Computer-executable instructions are stored in the computer-readable storage medium, and when the computer-executable instructions are executed by a processor, they are used to implement the method according to any one of claims 1-6.

10. A computer program product, characterized in that, It includes a computer program which, when executed by a processor, implements the method according to any one of claims 1-6.

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