Power distribution network protection method and device

Abstract

The invention provides a power distribution network protection method and device, and relates to the field of power system maintenance, and the method comprises the steps: analyzing the protection sensitivity ratio of all outgoing lines of a power distribution network, and determining the installation position of an isolation transformer in the power distribution network; after an isolation transformer is installed at the installation position, wave recording analysis is carried out on the zero-sequence current signal and the zero-sequence voltage signal of the power distribution network, and the instantaneous single-phase earth fault occurrence frequency of the power distribution network is obtained; and if the occurrence frequency of the instantaneous single-phase earth fault exceeds a frequency threshold value, generating a circuit break signal based on a preset instantaneous single-phase earth fault protection algorithm, and protecting the power distribution network. According to the invention, the protection effect on the single-phase short-circuit fault of the power distribution network can be improved, and the possibility of multiple insulation breakdown and dangerous overvoltage in the power supply system can be reduced.

Description

Technical Field

[0001] This application relates to the field of power system maintenance, and specifically to a distribution network protection method and device. Background Art

[0002] One of the most frequent faults in the distribution network is the single phase to ground fault (SPGF), and its occurrence frequency depends on network configuration, line length, number of electrical units, and climatic conditions, etc. In order to reduce important electrical equipment failures caused by SPGF, it is necessary to apply selective and reliable grounding fault protection measures. According to experimental data, the main reasons for the non-selective operation of equipment for single phase to ground fault protection include the instability of zero-sequence circuit parameters and short-term single phase to ground faults (StSPGF).

[0003] If the zero-sequence current exceeds the action set point, the protection operation algorithm for SPGF is triggered. However, since the zero-sequence current signal is intermittent, that is, the actual current value either exceeds the action set point or is lower than the action area, the protection algorithm does not allow selective detection and isolation of this fault. Within less than 1 s, the grounding fault changes from a short-term SPGF to a permanent grounding fault, resulting in more serious consequences for the electrical network.

[0004] A single short-term grounding fault, accompanied by a long dead zone, does not pose a great danger to the electrical network. However, chains of SPGF that continuously appear or disappear will occur before most stable and arcing grounding faults. These faults are accompanied by huge losses and require immediate isolation of the grounded line and equipment.

[0005] Single-phase grounding fault protection based on controlling the zero-sequence current in the stable SPGF mode is widely used in 6-10 kV distribution networks. However, the reliable operation of the current protection for SPGF requires that the value of the total capacitive current flowing through the damaged connection in the network exceeds 3-5 times the capacitive current value of the undamaged line itself. Therefore, the existing technology has limitations.

[0006] This section aims to provide background or context for the embodiments of the present invention stated in the claims. The description herein is not admitted to be prior art merely because it is included in this section. Summary of the Invention

[0007] Aiming at the problems in the prior art, this application provides a distribution network protection method and device, which can improve the protection effect on single-phase short circuit faults in the distribution network and reduce the possibility of multiple insulation breakdowns and dangerous overvoltages in the power supply system.

[0008] To solve the above technical problems, the present application provides the following technical solutions:

[0009] In a first aspect, the present application provides a method for protecting a distribution network, including:

[0010] Analyze the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network;

[0011] After installing the isolation transformer at the installation position, perform oscillogram analysis on the zero-sequence current signal and zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase grounding faults occurring in the distribution network;

[0012] If the number of instantaneous single-phase grounding faults exceeds the number threshold, generate a breaker signal based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network.

[0013] Further, the analyzing the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network includes:

[0014] Determine the capacitive current of the outgoing line itself according to the unit capacitive current of the outgoing line relative to the ground and the length of the outgoing line;

[0015] Calculate the sum of the unit capacitive currents of each outgoing line relative to the ground to obtain the total capacitive current of the grounding faults of all outgoing lines;

[0016] Determine the protection offset ratio according to the reliability ratio considering the relay action error and the inrush ratio considering the inrush response ability to the capacitive current when an instantaneous single-phase grounding fault occurs;

[0017] Determine the protection sensitivity ratio according to the proportion of the capacitive current of the outgoing line itself in the total grounding fault current and the protection offset ratio;

[0018] Determine the installation position according to the specific capacitive current of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitive current of the outgoing line itself, and the total capacitive current of the grounding faults of all outgoing lines.

[0019] Further, the performing oscillogram analysis on the zero-sequence current signal and zero-sequence voltage signal of the distribution network after installing the isolation transformer at the installation position to obtain the number of instantaneous single-phase grounding faults occurring in the distribution network includes:

[0020] Perform oscillogram recording on the zero-sequence voltage signal and the zero-sequence current signal, and obtain the differential signal of the zero-sequence voltage signal;

[0021] Compare the phase of the zero-sequence current signal with that of the differential signal to determine whether an instantaneous single-phase ground fault has occurred; if the instantaneous single-phase ground fault has occurred, record a primary insulation breakdown signal;

[0022] Use a counter to determine the number of times the insulation breakdown signal is recorded, and obtain the number of occurrences of the instantaneous single-phase ground fault in the distribution network.

[0023] Further, if the number of occurrences of the instantaneous single-phase ground fault exceeds a threshold number, generate a breaker signal based on a preset instantaneous single-phase ground fault protection algorithm to protect the distribution network, including:

[0024] Judge whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold;

[0025] If so, judge whether the amplitude of the zero-sequence current signal is greater than a preset current threshold;

[0026] If so, calculate the number of times that the amplitude of the zero-sequence voltage signal is greater than the voltage threshold and the amplitude of the zero-sequence current signal is greater than the current threshold;

[0027] If the number exceeds the threshold number, generate the breaker signal to protect the distribution network.

[0028] In a second aspect, the present application provides a distribution network protection device, including:

[0029] An installation position determination unit, configured to analyze the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network;

[0030] A fault number determination unit, configured to perform oscillogram analysis on the zero-sequence current signal and the zero-sequence voltage signal of the distribution network after installing the isolation transformer at the installation position to obtain the number of occurrences of the instantaneous single-phase ground fault in the distribution network;

[0031] A breaker protection unit, configured to generate a breaker signal based on a preset instantaneous single-phase ground fault protection algorithm to protect the distribution network if the number of occurrences of the instantaneous single-phase ground fault exceeds a threshold number.

[0032] Further, the installation position determination unit includes:

[0033] An outgoing line capacitance current determination module, configured to determine the capacitance current of the outgoing line itself according to the unit capacitance current of the outgoing line relative to the ground and the length of the outgoing line;

[0034] A total capacitance current sum determination module, configured to calculate the sum of the unit capacitance currents of all outgoing lines relative to the ground to obtain the total capacitance current of the grounding faults of all outgoing lines;

[0035] An offset ratio determination module, configured to determine a protection offset ratio according to a reliability ratio considering relay operation errors and a surge ratio considering the ability to respond to the inrush of capacitive current during the occurrence of an instantaneous single-phase grounding fault;

[0036] A sensitivity ratio determination module, configured to determine the protection sensitivity ratio according to the proportion of the capacitive current of the outgoing line itself in the total grounding fault current and the protection offset ratio;

[0037] An installation location determination module, configured to determine the installation location according to the specific capacitive current of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitive current of the outgoing line itself, and the total capacitive current of the grounding faults of all outgoing lines.

[0038] Further, the fault occurrence number determination unit includes:

[0039] A differential signal obtaining module, configured to perform oscillographic recording on the zero-sequence voltage signal and the zero-sequence current signal, and obtain the differential signal of the zero-sequence voltage signal;

[0040] A breakdown signal generation module, configured to compare the phases of the zero-sequence current signal and the differential signal to determine whether an instantaneous single-phase grounding fault occurs; if the instantaneous single-phase grounding fault occurs, record an insulation breakdown signal once;

[0041] A fault occurrence number statistics module, configured to use a counter to determine the number of recorded insulation breakdown signals to obtain the number of occurrences of instantaneous single-phase grounding faults in the distribution network.

[0042] Further, the open-circuit protection unit includes:

[0043] A voltage judgment module, configured to judge whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold;

[0044] A current judgment module, configured to, if so, judge whether the amplitude of the zero-sequence current signal is greater than a preset current threshold;

[0045] A fault occurrence number discrimination module, configured to, if so, calculate the number of times that the amplitude of the zero-sequence voltage signal is greater than the voltage threshold and the amplitude of the zero-sequence current signal is greater than the current threshold;

[0046] An open-circuit protection module, configured to, if the number exceeds the number threshold, generate the open-circuit signal to protect the distribution network.

[0047] In a third aspect, the present application provides an electronic device including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, the steps of the distribution network protection method are implemented.

[0048] Fourthly, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the distribution network protection method are implemented.

[0049] Fifthly, the present application provides a computer program product, including a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of the distribution network protection method are implemented.

[0050] In view of the problems in the prior art, the distribution network protection method and device provided by the present application can, in the case where there are significant discontinuities in the distribution network and the load changes in the distribution network show short-term suddenness, improve the sensitivity of the single-phase grounding fault protection action by selecting to install an isolation transformer at the connection of the outgoing line where the line capacitance current of its own line accounts for a larger proportion in the total capacitance current during a single-phase grounding fault; and can perform oscillogram analysis on the zero-sequence voltage signal and zero-sequence current signal of the distribution network, input them into the instantaneous single-phase grounding fault protection algorithm, further improve the protection effect on the distribution network when a single-phase short-circuit fault occurs, minimize the time spent in finding the damaged connection to the greatest extent, and reduce the probability of multiple insulation breakdowns and dangerous over-voltages occurring in the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0052] Figure 1 It is a flowchart of the distribution network protection method in the embodiment of the present application;

[0053] Figure 2 It is a flowchart of determining the installation position of the isolation transformer in the distribution network in the embodiment of the present application;

[0054] Figure 3 It is a flowchart of obtaining the number of instantaneous single-phase grounding faults occurring in the distribution network in the embodiment of the present application;

[0055] Figure 4 It is a flowchart of generating a circuit breaker signal in the embodiment of the present application;

[0056] Figure 5 It is a structural diagram of the distribution network protection device in the embodiment of the present application;

[0057] Figure 6 It is a structural diagram of the installation position determination unit in the embodiment of the present application;

[0058] Figure 7 This is the structural diagram of the fault count determination unit in the embodiments of the present application;

[0059] Figure 8 This is the structural diagram of the open - circuit protection unit in the embodiments of the present application;

[0060] Figure 9 This is the schematic structural diagram of the electronic device in the embodiments of the present application;

[0061] Figure 10 This is the schematic diagram of the protection operation algorithm for single - phase grounding faults in the embodiments of the present application;

[0062] Figure 11 This is the schematic diagram of the discrimination algorithm logic of StSPGF in the embodiments of the present application. Detailed implementation manners

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the following further elaborates on the embodiments of the present invention with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0064] In the technical solutions of the present application, the information collected is information and data authorized by the user or fully authorized by all parties. Moreover, for the processing of relevant data, such as collection, storage, use, processing, transmission, provision, disclosure, and application, etc., all comply with the relevant laws, regulations, and standards of relevant countries and regions, take necessary confidentiality measures, do not violate public order and good customs, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0065] Provide corresponding operation entrances for users to choose to agree or refuse the results of automated decision - making; if the user chooses to refuse, then enter the expert decision - making process.

[0066] In one embodiment, referring to Figure 1 , in order to improve the protection effect against single - phase short - circuit faults in the distribution network and reduce the possibility of multiple insulation breakdowns and dangerous over - voltages in the power supply system, the present application provides a distribution network protection method, including:

[0067] S101: Analyze the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation location of the isolation transformer in the distribution network;

[0068] S102: After installing the isolation transformer at the installation location, perform oscillogram analysis on the zero - sequence current signal and zero - sequence voltage signal of the distribution network to obtain the number of instantaneous single - phase grounding faults occurring in the distribution network;

[0069] S103: If the number of occurrences of the instantaneous single-phase grounding fault exceeds the number threshold, generate a circuit breaker signal based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network.

[0070] It can be understood that the present application proposes an effective single-phase grounding fault protection scheme, which can maintain necessary protection selectivity and operational invariance under the conditions of zero-sequence circuit parameter variation and the occurrence of StSPGF.

[0071] First of all, installing an isolation transformer in the distribution network can improve the sensitivity of single-phase grounding fault protection. One of the main functions of the isolation transformer in the distribution network is electrical isolation. It can make the primary side and the secondary side electrically completely insulated and also isolate the loop. When a single-phase grounding fault occurs in the distribution network, the isolation transformer can prevent the fault current from directly spreading through the grounding system, thereby limiting the range of the fault current. This limiting effect helps the protection device to more accurately detect the fault and take corresponding actions, thus improving the sensitivity of single-phase grounding fault protection.

[0072] Reasonably installing and using an isolation transformer in the distribution network has a positive effect on improving the sensitivity of single-phase grounding fault protection. Therefore, it is necessary to first determine the installation location of the isolation transformer in the distribution network. The installation location in the embodiments of the present application refers to the length (l tr ) of the cable or wire required to connect from the 10 kV bus (outgoing line) to the installation location of the isolation transformer.

[0073] Next, install the isolation transformer at the above installation location, and then start the oscillographic analysis of the zero-sequence current signal and zero-sequence voltage signal of the distribution network. When an instantaneous single-phase grounding fault occurs, there will be signal changes in the zero-sequence current signal and zero-sequence voltage signal, so as to obtain the number of occurrences of the instantaneous single-phase grounding fault in the distribution network. If the number of occurrences of the instantaneous single-phase grounding fault is too large and exceeds the number threshold, a circuit breaker signal will be generated based on the instantaneous single-phase grounding fault protection algorithm to realize the protection of the distribution network. After the circuit breaker processing is executed, since the isolation transformer has been installed in a suitable position, it can prevent the fault current from directly spreading through the grounding system within the smallest range, thereby limiting the influence range of the fault current.

[0074] Therefore, the method provided by the present application installs an isolation transformer at a suitable position and uses the instantaneous single-phase grounding fault protection algorithm to perform circuit breaker processing in a timely manner, protecting the distribution network to a greater extent and forming a complete protection scheme.

[0075] As can be seen from the above description, the distribution network protection method provided by the present application can, when there are significant discontinuities in the distribution network and the load changes in the distribution network show short-term suddenness, improve the sensitivity of the single-phase grounding fault protection action by selecting to install an isolation transformer at the connection of the outgoing line where the line capacitance current of its own line accounts for a larger proportion in the total capacitance current during a single-phase grounding fault; and can perform oscillogram analysis on the zero-sequence voltage signal and zero-sequence current signal of the distribution network, input them into the instantaneous single-phase grounding fault protection algorithm, further improve the protection effect on the distribution network when a single-phase short-circuit fault occurs, minimize the time spent in finding the damaged connection, and reduce the probability of multiple insulation breakdowns and dangerous overvoltages occurring in the power supply system.

[0076] In one embodiment, referring to Figure 2 , the analysis of the protection sensitivity ratio of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network includes:

[0077] S201: Determine the capacitance current of the outgoing line itself according to the unit capacitance current of the outgoing line relative to the ground and the length of the outgoing line;

[0078] S202: Calculate the sum of the unit capacitance currents of each outgoing line relative to the ground to obtain the total capacitance current of the grounding fault of all outgoing lines;

[0079] S203: Determine the protection offset ratio according to the reliability ratio considering the relay action error and the inrush ratio considering the inrush response ability to the capacitance current when an instantaneous single-phase grounding fault occurs;

[0080] S204: Determine the protection sensitivity ratio according to the proportion of the capacitance current of the outgoing line itself in the total grounding fault current and the protection offset ratio;

[0081] S205: Determine the installation position according to the specific capacitance current (also called the set capacitance current) of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitance current of the outgoing line itself, and the total capacitance current of the grounding fault of all outgoing lines.

[0082] It can be understood that for a distribution network, the incoming line refers to the power transmission (or distribution) power line that enters the distribution room (or distribution box), and the outgoing line is the power supply line fed out from the distribution room (or distribution box). These outgoing lines transmit electrical energy from the power distribution system to each load, ensuring the normal operation of the power system and meeting the electricity consumption needs of users.

[0083] Improving the effectiveness of SPGF is based on the analysis of the protection sensitivity ratio of all outgoing line connections. The protection sensitivity ratio can be calculated according to the following formula:

[0084]

[0085] Among them, m is the proportion of the capacitance current of the calculation line itself in the total ground fault current, and m = I l.c / I Sigma . This ratio reflects the relationship between the capacitance current of the line itself and the total capacitance current of the network during a ground fault. Among them, I l.c is the capacitance current of the line itself, and I Sigma is the total ground fault current.

[0086] K r is the protection offset ratio, and K r = K r.r ×K i . Among them, K r.r is the reliability ratio considering the relay action error and calculation error, and its value is usually between 1.2 and 1.3. K i is the "inrush" ratio considering the inrush of capacitance current during a ground fault and the response ability of the protection device to this inrush, and its value is usually between 1.5 and 1.8.

[0087] The capacitance current I l.c of the line itself is defined by the specific parameters of the line, and the calculation formula is as follows:

[0088] I l.c = I s.c.i ×l i (2)

[0089]

[0090] Among them, I s.c.i is the unit capacitance current of the i-th line relative to the ground, and the unit is A / km. l i is the length of the i-th line, and the unit is km. I Σc is the total capacitance current of the ground fault of all electrically connected network lines. l is the total length of the line.

[0091] The calculation of sensitivity helps to design and adjust the protection device to ensure that during a single-phase ground fault, the damaged line can be accurately detected and cut off, while avoiding unnecessary power outages and ensuring the stable operation of the power system.

[0092] To improve the protection sensitivity of the distribution network to single-phase ground faults, an isolation transformer should be used, which can be used for potential separation of the ground and underground complexes of 6-10 kV power networks. The isolation transformer should be installed on the line with a high proportion, which will increase the ratio between the capacitance current of the line itself and the total current of the network ground fault, thereby increasing the sensitivity of the protection.

[0093] The installation location of the isolation transformer should be selected according to safety rules and calculated according to the following formula for SPGF protection:

[0094]

[0095] where l tr is the line length required to determine the installation location of the isolation transformer; I s.c is the specific capacitive current of the line where the isolation transformer is installed; I CΣ is the total capacitive current of the ground fault of all electrical connection network lines;

[0096] Formula (4) can finally determine where to install the isolation transformer to improve the sensitivity of SPGF protection. By installing the isolation transformer on the outgoing line connection, the ratio between the capacitive current of the line itself and the total current of the network ground fault can be increased, thus improving the sensitivity of the protection. This measure is crucial for ensuring the reliability and safety of power supply, especially under the condition of significant discontinuity of network configuration.

[0097] That is to say, using formula (4) can analyze the efficiency of applying the isolation transformer according to the provided suggestions. Data analysis shows that installing the isolation transformer on the outgoing line connection and installing the isolation transformer on the line where the capacitive current of the line itself accounts for a relatively high proportion (the specific threshold can be set according to the actual working conditions) can improve the operating sensitivity of the isolation transformers installed on all outgoing line connections for SPGF protection and provide reliable protection operation for the distribution network.

[0098] The above method can allow recording the occurrence of StSPGF, notifying the existence of non-dangerous StSPGF, and cutting off dangerous StSPGF, and can selectively reveal the protection operation algorithms for metal, arc, and ground faults through transient resistance.

[0099] From the above description, it can be seen that the distribution network protection method provided by this application can analyze the protection sensitivity ratio of all outgoing lines of the distribution network and determine the installation location of the isolation transformer in the distribution network.

[0100] In one embodiment, referring to Figure 3 , after installing the isolation transformer at the installation location, performing oscillogram analysis on the zero-sequence current signal and zero-sequence voltage signal of the distribution network to obtain the occurrence times of instantaneous single-phase ground faults of the distribution network, including:

[0101] S301: Performing oscillogram recording on the zero-sequence voltage signal and the zero-sequence current signal, and obtaining the differential signal of the zero-sequence voltage signal;

[0102] S302: Compare the phase of the zero-sequence current signal with that of the differential signal to determine whether an instantaneous single-phase grounding fault has occurred; if the instantaneous single-phase grounding fault has occurred, record an insulation breakdown signal.

[0103] S303: Use a counter to determine the recording times of the insulation breakdown signal to obtain the occurrence times of the instantaneous single-phase grounding fault in the distribution network.

[0104] It can be understood that according to Figure 10 , the proposed protection operation algorithm continuously controls the main electrical signals. These signals describe the operation mode of the power network. First, measure the zero-sequence voltage signal 3u 0 and the zero-sequence current signal 3i 0 . Next, enter the Figure 10 left branch operation analysis path and right branch operation analysis path in.

[0105] Among them, the zero-sequence voltage signal 3u 0 refers to the vector sum of the voltages of the three phases ABC, while the zero-sequence current signal 3i 0 is the vector sum of the currents of the three phases ABC. In the power system, when a single-phase grounding fault occurs, zero-sequence voltage and zero-sequence current may be generated.

[0106] Figure 10 The left branch analysis path in is as follows:

[0107] Step1: When a grounding fault occurs, record this signal, such as performing waveform recording and analysis on 3u 0 and 3i 0 , and comparing the change processes of 3u 0 and 3i 0 along the time sequence.

[0108] Among them, the methods for performing waveform recording and analysis on 3u 0 and 3i 0 mainly include phase relationship reading and amplitude reading. For phase relationship reading, by comparing the peak points or zero-crossing points of 3i 0 and 3u 0 , the phase angle difference between the two can be observed, which is crucial for fault location and analysis.

[0109] For amplitude reading, in the fault waveform recording diagram, the changes in the amplitudes of 3u 0 and 3i 0 before and after the fault can be observed to judge the occurrence and severity of the fault. For example, in a single-phase grounding fault, the zero-sequence voltage 3u 0 at the fault point is the highest, and the zero-sequence voltage is lower the farther away from the fault point; at the same time, the zero-sequence current 3i 0 flows from the fault point to the neutral point.

[0110] In actual operation, the power system fault recorder can record and display 3u 0 and 3i 0 waveforms for technicians to analyze.

[0111] Step2: Differentiate the zero-sequence voltage 3u 0 to obtain the differential signal of the zero-sequence voltage, getting the differential component signal du 0 / dt.

[0112] Step3: Compare the phases of the zero-sequence current 3i 0 and du 0 / dt, and make a judgment through the StSPGF algorithm logic (the specific criteria of the algorithm logic will be described in detail later). If there is a single-phase ground fault StSPGF, then a primary insulation breakdown signal is obtained.

[0113] In addition, the phase relationship between the zero-sequence current and the zero-sequence voltage itself can also help to judge the single-phase ground fault. During a single-phase ground fault, the phase relationship between the zero-sequence current and the zero-sequence voltage has specific characteristics.

[0114] Step4: Transmit this information (recording the primary insulation breakdown signal) to the counter. The counter accumulates the information n 0 about the number of insulation breakdowns, and compares it with the set action point n set . If n 0 > n set , then it will enter the Figure 10 right-branch discrimination logic. If n 0 ≤ n set， , then the counting of n 0 will continue to be counted.

[0115] It should be noted that the subscripts set are all set values corresponding to the parameters.

[0116] As can be seen from the above description, the distribution network protection method provided by this application can, after installing an isolating transformer at the installation position, perform oscillographic analysis on the zero-sequence current signal and the zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase ground faults occurring in the distribution network.

[0117] In one embodiment, referring to Figure 4 , if the number of instantaneous single-phase ground faults exceeds the number threshold, a breaker signal is generated based on a preset instantaneous single-phase ground fault protection algorithm to protect the distribution network, including:

[0118] S401: Judge whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold;

[0119] S402: If so, determine whether the amplitude of the zero-sequence current signal is greater than a preset current threshold value;

[0120] S403: If so, calculate the number of times that the amplitude of the zero-sequence voltage signal is greater than the voltage threshold value and the amplitude of the zero-sequence current signal is greater than the current threshold value;

[0121] S404: If the number of times exceeds the number threshold value, generate the open-circuit signal to protect the distribution network.

[0122] It can be understood that Figure 10 the discrimination logic of the right middle branch is as described below:

[0123] Step1: Compare the zero-sequence voltage value 3u 0 with u set . If 3u 0 > u set , it indicates that the possibility of a single-phase grounding fault is relatively high, and enter Step2.

[0124] Step2: Discriminate through the protection based on the StSPGF algorithm. Refer to Figure 11 , and the discrimination formula is as follows:

[0125] Count{(3u 0 - u set ) & (3i 0 - i set )} ≥ the counter action threshold value. If the count exceeds the counter action threshold value, trip with a 0.1s delay.

[0126] Step3: Determine whether the zero-sequence current value 3i 0 is greater than i set , and occurs within a short time interval (which can be a preset value). If 3i 0 exceeds the set action point i set , generate an open-circuit signal to cut off the damaged line.

[0127] Step4: If n 0 is not greater than n set , then continue to accumulate and count n 0 .

[0128] If the insulation breakdown frequency is low, the protection algorithm will execute the function of "warning the existence of this emergency mode" to notify the operator to take measures to eliminate this accident.

[0129] It should be noted that set the subscripts are all the set values corresponding to the parameters.

[0130] In addition, the method provided by this application can also operate effectively during metal, arc, and ground faults. These faults occur through transient resistance, ensuring reliable protection for the 6-10 kV electrical network under various SPGF modes.

[0131] As can be seen from the above description, for the distribution network protection method provided by this application, if the number of occurrences of the instantaneous single-phase ground fault exceeds the number threshold, a circuit breaker signal can be generated based on a preset instantaneous single-phase ground fault protection algorithm to protect the distribution network.

[0132] Based on the same inventive concept, an embodiment of this application also provides a distribution network protection device, which can be used to implement the method described in the above embodiment, as described in the following embodiment. Since the principle of the distribution network protection device for solving problems is similar to that of the distribution network protection method, the implementation of the distribution network protection device can refer to the implementation of the method for determining software performance benchmarks, and the repeated parts will not be elaborated. Hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the systems described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0133] In one embodiment, referring to Figure 5 , in order to improve the protection effect of single-phase short-circuit faults in the distribution network and reduce the possibility of multiple insulation breakdowns and dangerous overvoltages in the power supply system, this application provides a distribution network protection device, including: an installation position determination unit 501, a fault number determination unit 502, and a circuit breaker protection unit 503.

[0134] The installation position determination unit 501 is used to analyze the protection sensitivity ratio of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network;

[0135] The fault number determination unit 502 is used to perform oscillogram analysis on the zero-sequence current signal and zero-sequence voltage signal of the distribution network after installing the isolation transformer at the installation position to obtain the number of occurrences of the instantaneous single-phase ground fault in the distribution network;

[0136] The circuit breaker protection unit 503 is used to generate a circuit breaker signal based on a preset instantaneous single-phase ground fault protection algorithm to protect the distribution network if the number of occurrences of the instantaneous single-phase ground fault exceeds the number threshold.

[0137] In one embodiment, referring to Figure 6 , the installation position determination unit 501 includes: an outgoing line capacitance current determination module 601, a total capacitance current sum determination module 602, an offset ratio determination module 603, a sensitivity ratio determination module 604, and an installation position determination module 605.

[0138] The outgoing line capacitance current determination module 601 is configured to determine the capacitance current of the outgoing line itself according to the unit capacitance current of the outgoing line relative to the ground and the length of the outgoing line;

[0139] The total capacitance current sum determination module 602 is configured to calculate the sum of the unit capacitance currents of each outgoing line relative to the ground to obtain the total capacitance current of the grounding fault of all outgoing lines;

[0140] The offset ratio determination module 603 is configured to determine the protection offset ratio according to the reliability ratio considering the relay operation error and the inrush ratio considering the inrush response ability to the capacitance current during the occurrence of an instantaneous single-phase grounding fault;

[0141] The sensitivity ratio determination module 604 is configured to determine the protection sensitivity ratio according to the proportion of the capacitance current of the outgoing line itself in the total grounding fault current and the protection offset ratio;

[0142] The installation position determination module 605 is configured to determine the installation position according to the specific capacitance current of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitance current of the outgoing line itself, and the total capacitance current of the grounding fault of all outgoing lines.

[0143] In one embodiment, referring to Figure 7 , the fault times determination unit 502 includes: a differential signal obtaining module 701, a breakdown signal generating module 702, and a fault times statistics module 703.

[0144] The differential signal obtaining module 701 is configured to perform wave recording on the zero-sequence voltage signal and the zero-sequence current signal, and obtain the differential signal of the zero-sequence voltage signal;

[0145] The breakdown signal generating module 702 is configured to compare the phases of the zero-sequence current signal and the differential signal to determine whether an instantaneous single-phase grounding fault occurs; if the instantaneous single-phase grounding fault occurs, record an insulation breakdown signal once;

[0146] The fault times statistics module 703 is configured to use a counter to determine the recording times of the insulation breakdown signal to obtain the occurrence times of the instantaneous single-phase grounding fault of the distribution network.

[0147] In one embodiment, referring to Figure 8 , the open circuit protection unit 503 includes: a voltage judgment module 801, a current judgment module 802, a fault times discrimination module 803, and an open circuit protection module 804.

[0148] The voltage judgment module 801 is configured to judge whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold;

[0149] The current judgment module 802 is configured to, if so, judge whether the amplitude of the zero-sequence current signal is greater than a preset current threshold value;

[0150] The fault times discrimination module 803 is configured to, if so, calculate the number of times that the amplitude of the zero-sequence voltage signal is greater than the voltage threshold value and the amplitude of the zero-sequence current signal is greater than the current threshold value;

[0151] The open-circuit protection module 804 is configured to, if the number of times exceeds the number threshold value, generate the open-circuit signal to protect the distribution network.

[0152] From the hardware level, in order to improve the protection effect against single-phase short-circuit faults in the distribution network and reduce the possibility of multiple insulation breakdowns and dangerous over-voltages in the power supply system, this application provides an embodiment of an electronic device for implementing all or part of the content in the distribution network protection method. The electronic device specifically includes the following:

[0153] A processor, a memory, a communication interface, and a bus; wherein, the processor, the memory, and the communication interface complete communication with each other through the bus; the communication interface is used to implement information transmission between the distribution network protection device and related devices such as a core service system, a user terminal, and a related database, etc. This logic controller can be a desktop computer, a tablet computer, a mobile terminal, etc., and this embodiment is not limited thereto. In this embodiment, this logic controller can be implemented with reference to the embodiments of the distribution network protection method and the embodiments of the distribution network protection device in the embodiments, and the content is incorporated herein, and the repeated parts will not be described again.

[0154] It can be understood that the user terminal may include a smart phone, a tablet electronic device, an Internet set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device may include smart glasses, a smart watch, a smart bracelet, etc.

[0155] In practical applications, part of the distribution network protection method can be executed on the electronic device side as described above, or all operations can be completed in the client device. Specifically, it can be selected according to the processing ability of the client device and the limitations of the user usage scenario, etc. This application does not make any limitations in this regard. If all operations are completed in the client device, the client device may further include a processor.

[0156] The above-mentioned client device may have a communication module (i.e., communication unit), which can communicate with a remote server to achieve data transmission with the server. The server may include a server on the task scheduling center side, and in other implementation scenarios, it may also include a server of an intermediate platform, such as a server of a third-party server platform with a communication link to the task scheduling center server. The server may include a single computer device, or a server cluster composed of multiple servers, or a server structure of a distributed device.

[0157] Figure 9 It is a schematic block diagram of the system composition of the electronic device 9600 according to an embodiment of the present application. As Figure 9 shown, the electronic device 9600 may include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It should be noted that this Figure 9 is exemplary; other types of structures can also be used to supplement or replace this structure to achieve telecommunication functions or other functions.

[0158] In one embodiment, the function of the distribution network protection method can be integrated into the central processing unit 9100. Among them, the central processing unit 9100 can be configured to perform the following controls:

[0159] S101: Analyze the protection sensitivity ratio of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network;

[0160] S102: After installing the isolation transformer at the installation position, perform oscillogram analysis on the zero-sequence current signal and zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase grounding faults occurring in the distribution network;

[0161] S103: If the number of instantaneous single-phase grounding faults exceeds the number threshold, generate a breaker signal based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network.

[0162] As can be seen from the above description, the distribution network protection method provided by the present application can, in the case where the distribution network has significant discontinuity and the load change in the distribution network shows short-term suddenness, improve the sensitivity of the single-phase grounding fault protection action by selecting to install an isolation transformer at the connection of the outgoing line where the line capacitance current of its own line accounts for a larger proportion in the total capacitance current during a single-phase grounding fault; and can perform oscillogram analysis on the zero-sequence voltage signal and zero-sequence current signal of the distribution network, input them into the instantaneous single-phase grounding fault protection algorithm, further improve the protection effect on the distribution network when a single-phase short-circuit fault occurs, minimize the time spent on finding the damaged connection, and reduce the probability of multiple insulation breakdowns and dangerous overvoltages in the power supply system.

[0163] In another embodiment, the distribution network protection device can be separately configured from the central processing unit 9100. For example, the data composite transmission device and the distribution network protection device can be configured as a chip connected to the central processing unit 9100, and the functions of the distribution network protection method can be realized through the control of the central processing unit.

[0164] As Figure 9 shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It should be noted that the electronic device 9600 does not necessarily have to include Figure 9 all the components shown in Figure 9 ; in addition, the electronic device 9600 may further include

[0165] As Figure 9 shown, the central processing unit 9100 is sometimes also referred to as a controller or an operation control. It may include a microprocessor or other processor devices and / or logic devices. The central processing unit 9100 receives inputs and controls the operations of the various components of the electronic device 9600.

[0166] Among them, the memory 9140 can be, for example, one or more of a buffer, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory, or other suitable devices. It can store the above information related to failures, and can also store programs for executing relevant information. And the central processing unit 9100 can execute the programs stored in the memory 9140 to implement information storage or processing, etc.

[0167] The input unit 9120 provides inputs to the central processing unit 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to supply power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display can be, for example, an LCD display, but is not limited thereto.

[0168] The memory 9140 can be a solid-state memory. For example, a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It can also be a memory that stores information even when powered off, can be selectively erased and has more data. Examples of such a memory are sometimes referred to as EPROMs, etc. The memory 9140 can also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142, and the application / function storage unit 9142 is used to store application programs and function programs or the processes for operating the electronic device 9600 through the central processing unit 9100.

[0169] The memory 9140 may further include a data storage unit 9143 for storing data such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various drivers for the communication functions of the electronic device and / or for performing other functions of the electronic device (such as a messaging application, an address book application, etc.).

[0170] The communication module 9110 is a transmitter / receiver that transmits and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processor 9100 to provide input signals and receive output signals, which may be the same as in the case of a conventional mobile communication terminal.

[0171] Based on different communication technologies, multiple communication modules 9110 may be provided in the same electronic device, such as a cellular network module, a Bluetooth module, and / or a wireless local area network module, etc. The communication module (transmitter / receiver) 9110 is also coupled to the speaker 9131 and the microphone 9132 via the audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, so as to implement the usual telecommunication functions. The audio processor 9130 may include any suitable buffers, decoders, amplifiers, etc. In addition, the audio processor 9130 is also coupled to the central processor 9100, so that it is possible to record on the local machine through the microphone 9132 and play the sound stored on the local machine through the speaker 9131.

[0172] Embodiments of the present application also provide a computer-readable storage medium capable of implementing all steps of the distribution network protection method in which the execution subject in the above embodiments is a server or a client. A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, all steps of the distribution network protection method in which the execution subject in the above embodiments is a server or a client are implemented. For example, when the processor executes the computer program, the following steps are implemented:

[0173] S101: Analyze the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation location of the isolation transformer in the distribution network;

[0174] S102: After installing the isolation transformer at the installation location, perform oscillogram analysis on the zero-sequence current signal and the zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase ground faults occurring in the distribution network;

[0175] S103: If the number of occurrences of the instantaneous single-phase grounding fault exceeds the number threshold, generate a circuit breaker signal based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network.

[0176] As can be seen from the above description, the distribution network protection method provided by this application can, in the case where the distribution network has significant discontinuity and the load change in the distribution network shows short-term suddenness, by selecting to install an isolation transformer at the connection of the outgoing line where the capacitive current of its own line accounts for a larger proportion in the total capacitive current during a single-phase grounding fault, improve the sensitivity of the single-phase grounding fault protection action; and can perform oscillogram analysis on the zero-sequence voltage signal and zero-sequence current signal of the distribution network, input them into the instantaneous single-phase grounding fault protection algorithm, further improve the protection effect on the distribution network when a single-phase short-circuit fault occurs, minimize the time spent in finding the damaged connection to the greatest extent, and reduce the probability of multiple insulation breakdowns and dangerous overvoltages occurring in the power supply system.

[0177] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, devices, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0178] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for realizing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0179] These computer program instructions can 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 generate a manufactured article including an instruction device, and the instruction device realizes the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0180] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus, such that a series of operation steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one process or a plurality of processes and / or blocks Figure 1 one process or a plurality of processes and / or blocks Figure 1 steps for implementing the functions specified in one block or a plurality of blocks.

[0181] In the present invention, specific embodiments are used to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A distribution network protection method, characterized in that: include: Analyzing the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network; After installing the isolation transformer at the installation location, recording and analyzing the zero-sequence current signal and the zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase grounding faults of the distribution network; If the number of occurrences of the instantaneous single-phase grounding fault exceeds a threshold number, a trip signal is generated based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network.

2. The distribution network protection method according to claim 1, characterized in that: The analyzing the protection sensitivity ratios of all outgoing lines of the distribution network to determine the installation position of the isolation transformer in the distribution network includes: Determine the capacitance current of the outgoing line itself according to the unit capacitance current of the outgoing line relative to the ground and the length of the outgoing line; Calculate the sum of the unit capacitance current of each outgoing line relative to the ground to obtain the total ground fault capacitance current of all outgoing lines; Determine the protection shift ratio based on the reliability ratio considering the relay operation error and the inrush ratio considering the inrush response capability to the capacitive current when the instantaneous single-phase ground fault occurs; Determine the protection sensitivity ratio according to the proportion of the capacitive current of the outgoing line itself in the total ground fault current and the protection offset ratio; The installation position is determined according to the set capacitance current of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitance current of the outgoing line itself and the total capacitance current of the ground fault of all the outgoing lines.

3. The distribution network protection method according to claim 1, characterized in that: After the isolation transformer is installed at the installation location, recording and analyzing the zero-sequence current signal and the zero-sequence voltage signal of the distribution network to obtain the number of instantaneous single-phase grounding faults of the distribution network includes: Recording the zero-sequence voltage signal and the zero-sequence current signal, and obtaining a differential signal of the zero-sequence voltage signal; Comparing the phases of the zero-sequence current signal and the differential signal to determine whether an instantaneous single-phase grounding fault occurs; if the instantaneous single-phase grounding fault occurs, recording an insulation breakdown signal; The number of recordings of the insulation breakdown signal is determined by using a counter to obtain the number of occurrences of instantaneous single-phase grounding faults in the distribution network.

4. The distribution network protection method according to claim 1, characterized in that: If the number of occurrences of the instantaneous single-phase grounding fault exceeds a number threshold, a circuit breaker signal is generated based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network, including: Determining whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold; If so, determining whether the amplitude of the zero-sequence current signal is greater than a preset current threshold; If so, calculate the number of times the amplitude of the zero-sequence voltage signal is greater than the voltage threshold and the amplitude of the zero-sequence current signal is greater than the current threshold; If the number exceeds the number threshold, the circuit breaker signal is generated to protect the distribution network.

5. A distribution network protection device, characterized in that: include: An installation position determination unit, used to analyze the protection sensitivity ratios of all outgoing lines of the distribution network and determine the installation position of the isolation transformer in the distribution network; A fault number determination unit is used to perform waveform analysis on the zero-sequence current signal and the zero-sequence voltage signal of the distribution network after the isolation transformer is installed at the installation position, so as to obtain the number of instantaneous single-phase grounding faults of the distribution network; A circuit breaker protection unit is used to generate a circuit breaker signal based on a preset instantaneous single-phase grounding fault protection algorithm to protect the distribution network if the number of occurrences of the instantaneous single-phase grounding fault exceeds a number threshold.

6. The power distribution network protection device according to claim 5, characterized in that: The installation position determining unit comprises: An outgoing line capacitance current determination module, used to determine the capacitance current of the outgoing line itself according to the unit capacitance current of the outgoing line relative to the ground and the length of the outgoing line; A total capacitance current sum determination module is used to calculate the sum of the unit capacitance current of each outgoing line relative to the ground to obtain the total capacitance current of the ground fault of all outgoing lines; An offset ratio determination module is used to determine a protection offset ratio according to a reliability ratio considering a relay action error and an inrush ratio considering an inrush response capability to a capacitive current when an instantaneous single-phase grounding fault occurs; A sensitivity ratio determination module, used to determine the protection sensitivity ratio according to the proportion of the capacitive current of the outgoing line itself in the total ground fault current and the protection offset ratio; The installation position determination module is used to determine the installation position according to the set capacitance current of the line where the isolation transformer is installed, the protection offset ratio, the protection sensitivity ratio, the capacitance current of the outgoing line itself and the total capacitance current of the ground fault of all the outgoing lines.

7. The power distribution network protection device according to claim 5, characterized in that: The failure number determination unit comprises: A differential signal obtaining module, used for recording the zero-sequence voltage signal and the zero-sequence current signal, and obtaining a differential signal of the zero-sequence voltage signal; A breakdown signal generating module, used for comparing the phases of the zero-sequence current signal and the differential signal to determine whether an instantaneous single-phase grounding fault occurs; if the instantaneous single-phase grounding fault occurs, recording an insulation breakdown signal; The fault number statistics module is used to use a counter to determine the number of records of the insulation breakdown signal to obtain the number of instantaneous single-phase grounding faults of the distribution network.

8. The power distribution network protection device according to claim 5, characterized in that: The circuit breaker protection unit comprises: A voltage judgment module, used to judge whether the amplitude of the zero-sequence voltage signal is greater than a preset voltage threshold; A current judgment module, used to judge whether the amplitude of the zero-sequence current signal is greater than a preset current threshold; A fault number determination module, for calculating the number of times the amplitude of the zero-sequence voltage signal is greater than the voltage threshold and the amplitude of the zero-sequence current signal is greater than the current threshold; The circuit breaker protection module is used to generate the circuit breaker signal to protect the distribution network if the number of times exceeds the number threshold.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the distribution network protection method according to any one of claims 1 to 4 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the distribution network protection method described in any one of claims 1 to 4 are implemented.

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