Power distribution network in-situ island protection method and system based on fault characteristics

Abstract

The invention discloses a power distribution network on-site island protection method and system based on fault characteristics, and the method comprises the steps: 101, judging the fault characteristics, setting a fault generation mark parameter Sigfoc from 0 to 1 and keeping the fault generation mark parameter Sigfoc when a t0 moment at least meets one of fault characteristic identification criteria, setting a fault continuous mark parameter Sigfsum from 0 to 1, and keeping the fault generation mark parameter Sigfoc from 0 to 1 when the t0 moment at least meets one of the fault characteristic identification criteria; when fault feature identification criteria are not met at any moment, Sigfsum is reset to be 0; when the memory time of the Sigfoc setting 1 reaches T time, resetting the Sigfoc to 0; when it is judged that the island occurs, setting an island formation sign parameter Sigisland from 0 to 1, and executing the step 102; step 102, in the period of Sigisland = 1, if the islands disappear, the Sigisland is immediately reset to be 0, and if the islands disappear, the Sigisland is reset to be 0; if the Sigisland is kept to be 1 and after a time delay tset1 is waited, when the Sigisland is equal to 1, the Sigfoc is equal to 1 and the Sigfsus is equal to 0, the islanding protection acts immediately, meanwhile, the Sigfoc, the Sigfsus and the Sigisland are reset to be 0, and the step 101 is executed; if the Sigisland is kept to be 1 and after the time delay tset1 is waited, the conditions that the Sigisland is equal to 1, the Sigfoc is equal to 1 and the Sigfsus is equal to 0 are not met, the step 103 is executed: after the time delay tset2 is reached from the time t0, the islanding protection acts immediately, meanwhile, the mark parameters Sigfoc, Sigfsus and Sigisland are reset to be 0, and the step 101 is executed.

Description

Technical Field

[0001] This invention relates to the field of distribution network protection technology, and more specifically, to a method and system for local islanding protection of distribution networks based on fault characteristics. Background Technology

[0002] With the increasing proportion of distributed generation in power distribution networks, numerous problems have arisen, among which islanding is one of the most prominent. Unplanned islanding, especially caused by circuit breaker tripping due to faults or other factors, poses significant risks to power system equipment and maintenance personnel due to its randomness and unpredictability. These risks include voltage / frequency fluctuations leading to power quality degradation, interference with grid switch reclosing, and potential electric shocks to maintenance personnel. Therefore, it is necessary to be able to quickly identify islanding conditions and disconnect distributed generation lines or grid connection points as needed.

[0003] To avoid power system islanding, existing technologies involve installing protection devices at the point of common coupling (PCC) and controllers at distributed generation sources. Currently, most provincial grid companies have installed islanding protection devices at locations such as 110kV substations, 10kV switching stations, and PCC points in distribution rooms with a certain scale of renewable energy access. Upon identifying an island, the protection device trips or remotely disconnects the renewable energy line according to preset logic. In the early stages, due to the small capacity of distributed generation sources and the large power differences between source and load, existing technologies could reliably identify islands and act quickly, and the coordination conflict between islanding protection actions and line protection, automatic devices, etc., was not prominent. However, the high proportion of distributed generation access changes the source-load distribution characteristics of the distribution network. In particular, the addition of energy storage may lead to an increase in the source-load matching level, a decrease in the speed of islanding protection actions, and thus an increased risk of mismatch with line protection, automatic transfer switch, and reclosing, leading to a further expansion of the scope of grid accidents.

[0004] Existing local protection technologies can identify islands when the capacity of distributed power sources is small and the power difference between the source and the load is large, based on the huge changes or fluctuations in characteristic quantities after the island is formed. However, as the power matching level of the source and the load in a local area gradually improves, the change in electrical quantity characteristics after the island is formed is small and slow, which leads to a decrease in the reliability of existing island identification methods, slow island protection action or even failure to act, causing a series of power grid operation and personal safety problems. Summary of the Invention

[0005] The present invention provides a method and system for local islanding protection of distribution networks based on fault characteristics, in order to solve the problem of how to perform islanding protection based on local measurement signals and fault characteristics.

[0006] To address the above problems, this invention provides a method for local islanding protection of distribution networks based on fault characteristics, the method comprising:

[0007] Fault characteristics of the distribution network are determined by fault feature identification methods for island identification.

[0008] When it is determined that the fault characteristics meet one of the fault characteristic identification criteria, and it is determined that islanding has occurred in the distribution network, islanding protection action is performed on the distribution network.

[0009] Preferably, the fault feature identification method for islanding identification determines the fault features; when the fault features satisfy one of the fault feature identification criteria and islanding is determined to have occurred, islanding protection actions are performed on the distribution network, including:

[0010] Fault characteristics are determined using a fault feature identification method for island identification. When a fault feature is determined to satisfy at least one of the fault feature identification criteria at time t0, the fault generation flag parameter Sig is set. foc Set the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set from 0 to 1;

[0011] In Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0. Preferably, if Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus =0 after:

[0012] Waiting delay, when the delay t is reached from time t0. set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sigisland Reset to 0.

[0013] Preferably, if Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus =0 after:

[0014] Waiting delay, when the delay t is reached from time t0. set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

[0015] Preferably, the fault feature identification criteria include severe fault identification, and the fault features of the distribution network include measured electrical quantities:

[0016] When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network:

[0017] U1 / U N ≤0.5 (1)

[0018] Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

[0019] Preferably, the fault feature identification criterion for island identification is non-severe fault identification:

[0020] When the measured electrical quantities at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network:

[0021] U1 / U N >0.5

[0022] The non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

[0023] Preferably, the identification method for the two-phase short-circuit fault and the two-phase ground fault in the non-serious fault identification is as follows:

[0024] When the measured electrical quantities in the measurement information at the island protection installation point meet one of the following two conditions, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault:

[0025] U2 / U N >U set,2ph (2)

[0026]

[0027] Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

[0028] Preferably, the method for identifying single-phase ground faults in the non-serious fault identification process is as follows:

[0029] When the measured electrical quantities at the island protection installation point satisfy the following formula, it is determined to be a single-phase ground fault:

[0030] 3ΔU0 / U N ≥U set,1ph (5)

[0031] Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

[0032] According to another aspect of the present invention, the present invention provides a local islanding protection system for distribution networks based on fault characteristics, the system comprising:

[0033] The judgment unit determines the fault characteristics of the distribution network through a fault characteristic identification method for islanding identification;

[0034] The first execution unit is used to perform islanding protection actions on the distribution network when it is determined that the fault characteristics meet one of the fault characteristic identification criteria and that islanding has occurred in the distribution network.

[0035] Preferably, the judgment unit is further configured to: judge fault features using a fault feature identification method for island identification; and when it is determined that the fault features satisfy at least one of the fault feature identification criteria at time t0, set the fault generation flag parameter Sig... foc Set the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. islandSet from 0 to 1;

[0036] The first execution unit is further configured to: in Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0.

[0037] Preferably, the system further includes a second execution unit for:

[0038] If Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus When t = 0, there is a waiting delay. When the delay t is reached, starting from time t0... set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

[0039] Preferably, the fault feature identification criteria include severe fault identification, and the fault features of the distribution network include measured electrical quantities:

[0040] When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network:

[0041] U1 / U N ≤0.5 (1)

[0042] Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

[0043] Preferably, the fault feature identification criteria for island identification include non-critical fault identification:

[0044] When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network:

[0045] U1 / UN >0.5

[0046] The non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

[0047] Preferably, the identification method for the two-phase short-circuit fault and the two-phase ground fault in the non-serious fault identification is as follows:

[0048] When the measured electrical quantities in the measurement information at the island protection installation point meet one of the following two conditions, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault:

[0049] U2 / U N >U set,2ph (2)

[0050]

[0051] Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

[0052] Preferably, the single-phase ground fault identification method in the non-serious fault identification is as follows:

[0053] When the measured electrical quantities in the measurement information at the island protection installation location satisfy the following formula, it is judged as a single-phase ground fault:

[0054] 3ΔU0 / U N ≥U set,1ph (5)

[0055] Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

[0056] According to another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a method for local islanding protection of a distribution network based on fault characteristics.

[0057] According to another aspect of the present invention, the present invention provides an electronic device, characterized in that it comprises:

[0058] The aforementioned computer-readable storage medium; and

[0059] One or more processors for executing a program in the computer-readable storage medium.

[0060] This invention provides a method and system for local islanding protection of distribution networks based on fault characteristics. The method includes: determining the fault characteristics of the distribution network using a fault characteristic identification method for islanding identification; and when the fault characteristics satisfy one of the fault characteristic identification criteria, and islanding is determined to have occurred in the distribution network, performing islanding protection actions on the distribution network. The local islanding protection method and system proposed in this invention do not rely on communication or signal injection devices, but are based solely on locally measured signals and fault characteristics, thereby improving the reliability of islanding identification. This invention avoids a series of safety hazards caused by slow action speed due to the failure of islanding protection to identify islands in a timely manner. Attached Figure Description

[0061] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0062] Figure 1 This is a flowchart of a local islanding protection method for a distribution network based on fault characteristics, according to a preferred embodiment of the present invention.

[0063] Figure 2 A schematic diagram of a typical line and scenario of islanding caused by a distribution network fault according to a preferred embodiment of the present invention;

[0064] Figure 3 This is a graph showing the variation of positive-sequence voltage and negative-sequence voltage during a two-phase ground fault according to a preferred embodiment of the present invention.

[0065] Figure 4 This is a graph showing the variation of positive-sequence voltage and negative-sequence voltage during a single-phase ground fault according to a preferred embodiment of the present invention.

[0066] Figure 5 This is a schematic diagram of a fault event without islands according to a preferred embodiment of the present invention;

[0067] Figure 6 A schematic diagram illustrating an islanding event caused by a fault according to a preferred embodiment of the present invention, and the disappearance of the fault after the island is formed;

[0068] Figure 7 A schematic diagram illustrating an islanding event caused by a fault according to a preferred embodiment of the present invention, and the fault persistence after islanding is formed;

[0069] Figure 8 A schematic diagram illustrating an islanding event caused by non-fault factors such as switch tripping according to a preferred embodiment of the present invention; and

[0070] Figure 9 This is a structural diagram of a local islanding protection system for a distribution network based on fault characteristics, according to a preferred embodiment of the present invention. Detailed Implementation

[0071] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0072] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0073] Figure 1 This is a flowchart of a local islanding protection method for a distribution network based on fault characteristics, according to a preferred embodiment of the present invention.

[0074] To address the issue of insufficient reliability in islanding identification and protection after large-scale distributed generation (DG) integration into distribution networks, this invention proposes an islanding protection method that relies solely on locally measured signals and fault characteristics, without depending on communication or signal injection devices. This improves the reliability of islanding identification and avoids a series of safety hazards caused by slow response times due to failure to identify islands in a timely manner. This invention presents a fault-characteristic-based local islanding protection method for distribution networks with DG, designed to improve system recovery efficiency after faults in DG-integrated distribution networks and reduce the impact of unplanned islanding. It belongs to the field of distribution network protection technology.

[0075] like Figure 1 As shown, this invention provides a method for local islanding protection of distribution networks based on fault characteristics, characterized in that the method includes:

[0076] Step 101: Determine the fault characteristics of the distribution network using a fault feature identification method for islanding identification;

[0077] Step 102: When it is determined that the fault characteristics meet one of the fault characteristic identification criteria, and it is determined that islanding has occurred in the distribution network, islanding protection action is performed on the distribution network.

[0078] The method includes: determining fault and islanding characteristics based on measured electrical quantities at the islanding protection installation location. Fault characteristics are determined using a fault feature identification method oriented towards islanding identification. When a fault feature is determined to satisfy at least one of the fault feature identification criteria at time t0, the fault generation flag parameter Sig is set. focSet the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set from 0 to 1;

[0079] In Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0;

[0080] If Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus When t = 0, there is a waiting delay. When the delay t is reached, starting from time t0... set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

[0081] Preferably, the fault characteristic identification criteria include severe fault identification, and the fault characteristics of the distribution network include measured electrical quantities:

[0082] When the measured electrical quantities at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network:

[0083] U1 / U N ≤0.5 (1)

[0084] Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

[0085] Preferably, the fault feature identification criteria for island identification include non-critical fault identification:

[0086] When the measured electrical quantities at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network:

[0087] U1 / U N >0.5

[0088] Non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

[0089] Preferably, the method for identifying two-phase-to-phase short-circuit faults and two-phase-to-ground faults in the non-serious fault identification is as follows:

[0090] When the measured electrical quantity at the island protection installation point satisfies one of the following two equations, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault:

[0091] U2 / U N >U set,2ph (2)

[0092]

[0093] Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

[0094] Preferably, the method for identifying single-phase ground faults in non-serious fault identification is as follows:

[0095] When the measured electrical quantities at the island protection installation point satisfy the following formula, it is determined to be a single-phase ground fault:

[0096] 3ΔU0 / U N ≥U set,1ph (5)

[0097] Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

[0098] The principles of applying fault feature identification to island identification in this invention include:

[0099] Principle 1: Fault feature identification is a supplement to, rather than a replacement for, the original islanding identification method. It is used to improve the reliability of the original islanding identification, speed up the islanding protection action, and at the same time, it can distinguish between faulty and fault-free islanding states, which facilitates the coordination between islanding protection and line protection and safety automatic devices.

[0100] Principle 2: Islanding protection that uses fault feature identification does not assume the function of isolating line faults.

[0101] The fault feature identification method for island identification in this invention includes:

[0102] Serious fault identification:

[0103] Figure 2 The diagram shows a typical distribution network topology. After a fault, the upstream system-side protection detects the fault characteristics and will operate with a delay. At the same time, the downstream islanding protection can also extract certain fault characteristics. When the upstream system-side protection trips, the downstream protection forms an island and may operate with the fault.

[0104] A serious system fault is considered to have occurred when the electrical quantities measured at the islanding protection installation point meet the following conditions:

[0105] U1 / U N ≤0.5 (1)

[0106] In the formula, U1 represents the positive sequence voltage amplitude measured at the location of the islanding protection, U N This indicates the system's rated voltage. Meeting the above conditions generally indicates a three-phase short circuit and some two-phase-to-ground short circuits in the system. When a "serious fault" is met, distributed generation sources without fault ride-through capability will disconnect from the grid within 0.2 seconds, while those with fault ride-through capability will disconnect within 1.3 seconds.

[0107] Non-critical fault identification:

[0108] Faults that do not satisfy equation (1) are non-critical faults, i.e., U1 / U N >0.5, including two-phase short-circuit faults, single-phase ground faults, and partial two-phase ground faults.

[0109] 1) Identification of two-phase short circuit faults

[0110] When a two-phase short-circuit fault occurs in the system, regardless of whether the power supply side protection operates, the positive and negative sequence voltages at the fault point are close to 0.5 (per unit, pu). The positive sequence voltage on the distributed power supply side is slightly higher than 0.5, and the negative sequence voltage is lower than 0.5, with numerical differences depending on the different negative sequence control strategies of the distributed power supply.

[0111] When the electrical quantities at the island protection installation point satisfy one of the following two equations, it is considered to have the characteristics of a two-phase short circuit fault. Among them, when the distributed power source adopts a control strategy of suppressing negative sequence current, its negative sequence equivalent circuit is approximately open circuit, and the negative sequence voltage at the island protection installation point after the fault is approximately equal to that at the fault point. At this time, equation (2) should be satisfied. When the distributed power source adopts a control strategy that does not suppress negative sequence current, according to the requirements of the national standard for the negative sequence control strategy of new energy inverters and the level of distribution network parameters, the negative sequence equivalent circuit of the distributed power source is not open circuit, but the negative sequence impedance is much greater than the negative sequence impedance on the system side. At this time, equation (3) should be satisfied.

[0112] U2 / U N >U set,2ph (2)

[0113]

[0114] In the formula: U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph To determine the criteria for two-phase-to-phase short-circuit faults, considering the negative sequence voltage drop from the fault point to the islanded protection installation location and the finite fault transition resistance, a certain margin should be allowed between the value of U and 0.5 at the fault point. op,2 The starting setpoint indicates that the negative sequence voltage has a value and is higher than the negative sequence voltage level generated by the normal imbalance of the system, and should have 0.1 ≤ U op,2 <0.3≤U set,2ph ≤0.4, a reference value of U is given. set,2ph =0.3, U op,2 =0.2.

[0115] 2) Identification of two-phase grounding faults

[0116] When a two-phase-to-ground fault occurs in the system, based on composite sequence network calculations, the magnitudes of the positive-sequence voltage and negative-sequence voltage at the fault point depend on the ratio of the positive-sequence and zero-sequence equivalent impedances looking from the fault point to the system, Z1 / Z0 (e.g., ...). Figure 3 When the neutral point of the distribution network is grounded via an arc suppression coil or ungrounded, Z1 / Z0 is approximately 0; when the neutral point is grounded via a small resistor, Z1 / Z0 is slightly higher but still much less than 1, with a typical range of 0.01 to 0.3. Therefore, the identification of two-phase grounding fault characteristics can be consistent with that of two-phase short circuit, that is, if the electrical quantities at the island protection installation point satisfy either equation (2) or equation (3), it is considered that there are two-phase grounding fault characteristics.

[0117] 3) Single-phase ground fault identification

[0118] When a single-phase ground fault occurs in the system, the zero-sequence electrical quantity changes abruptly. Since the islanding protection is installed upstream of the distribution transformer and its neutral point is generally not grounded, there is almost no zero-sequence current at the islanding protection installation location. The zero-sequence voltage can be used to identify the single-phase ground fault. The zero-sequence voltage at the islanding protection installation location before and after the islanding occurs can be described by the following formula:

[0119]

[0120] In the formula, ΔU0 represents the zero-sequence voltage change at the islanding protection installation point, Z1, Z2, and Z0 represent the equivalent positive-sequence, negative-sequence, and zero-sequence impedances of the system as viewed from the fault point, respectively, and R... f This indicates the fault transition resistance.

[0121] The reasons for approximating and simplifying equation (4) include the following aspects: 1) Before the system-side protection operates, the positive and negative sequence equivalent impedances of the system are mainly composed of line parameters, which is 10 -1 ~10 0 The value is on the order of Ω; in contrast, the zero-sequence equivalent impedance is mainly determined by the line-to-ground impedance, and even the smallest value, achieved through a small-resistance grounding method for the neutral point, is still 10 Ω. 1 The order of magnitude is on the order of Ω, while the other two both reach 10. 3 ~10 4 Ω level. 2) After the system-side protection operates, the resulting islanded system is a neutral-point ungrounded system. The positive and negative sequence equivalent impedances are determined by the load-side impedance, which is 10Ω. 2 The zero-sequence equivalent impedance is on the order of Ω, representing the capacitive reactance to ground of the islanded line, which is 10. 4 The order of magnitude is Ω. In summary, Z1 and Z2 are negligible relative to Z0 in all cases, or approximately negligible under non-precise calculation requirements. For example... Figure 4 As shown.

[0122] Therefore, when the electrical quantities at the island protection installation point satisfy the following formula, it is considered to have the characteristics of a single-phase ground fault:

[0123] 3ΔU0 / U N ≥U set,1ph (5)

[0124] In the formula, U set,1ph The setpoint is for single-phase grounding fault identification, with a range of 0.1 to 0.2, and a value of 0.1 is recommended. The withstand resistance capability of a low-resistance grounding system is approximately 50Ω, while the withstand resistance capability of a system with an arc suppression coil and no grounding exceeds 6kΩ.

[0125] In Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus =0;

[0126] Waiting delay, when the delay t is reached from time t0. set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0. Criteria for integrated islanding protection action after successful fault feature identification in this invention:

[0127] If the islanding protection identifies the fault characteristics, there are two possible scenarios: 1) Islanding occurs after the system-side protection upstream of the fault point operates, and then the fault disappears. That is, the islanding protection can identify the fault characteristics, but the fault characteristics have disappeared before the islanding protection operates; 2) The fault characteristics can still be identified before the islanding protection operates. That is, the fault characteristics persist from the time the fault occurs until the island is formed.

[0128] Let the fault occurrence flag parameter Sig foc It reflects whether a fault has occurred; let the fault persistence flag parameter Sig be... fsus It reflects whether a fault exists before the islanding protection takes effect; the islanding formation indicator parameter Sig island This reflects the island identification results of the original island identification method. The island identification steps based on fault characteristics are as follows:

[0129] Step 1: Determine the fault and islanding characteristics based on the measured electrical quantities at the islanding protection installation location. The fault characteristics are determined using a fault feature identification method for islanding identification. When it is determined that at least one of the fault feature identification criteria is met at time t0, the fault generation flag parameter Sig is set. foc Set the value from 0 to 1 and maintain it (hold time T = 5 seconds), and set the fault persistence flag parameter Sig. fsus Sig is set from 0 to 1 and when the fault feature identification criterion is not satisfied at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. focReset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set the value from 0 to 1 and proceed to step 2;

[0130] Step 2: In Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0, return to step 101; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus When = 0, proceed to step 3; in this step, all original island identification algorithms for island protection have return criteria, and Sig will only return when the return criteria are met. island Set from 1 to 0. Where, delay t set1 Slightly later than the latest operating time of the second stage of the multi-level protection for the line, but earlier than the operating time of the no-voltage check and the non-calibration reclosing, that is:

[0131] t set1 =max(t) II )+Δt<min(t rcls,jwy ,t rcls,bjd ), Sig island =1,Sig foc =1,Sig fsus =0(6)

[0132] In the formula, max(t) II ) represents the longest operating delay of stage II of the multi-level protection system, typically 0.3–0.6; Δt represents the coordination level difference considering the switching action time, Δt = 0.1–0.2; t rcls,jwy and t rcls,bjd These represent the reclosing time when the reclosing is performed using the no-voltage check and no-check methods, respectively, and are generally greater than 1.

[0133] Step 3: Wait for the delay, until the delay t is reached, starting from time t0. set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sigisland Reset to 0 and return to step 1;

[0134] Based on t0, achieve a delay t set2 (t set2 ≥t set1 The island protection action after t set2 Specifically:

[0135]

[0136] In the formula, max(t) III The ) indicates the longest operating delay of stage III of the multi-level protection system, typically 1.3 to 1.8 seconds; t LVRT This indicates the shortest ride-through time required for low-voltage ride-through control of distributed power sources.

[0137] This invention is based on Figure 2 Taking a typical distribution network topology as an example, four typical cases are used to illustrate the effectiveness of the invention:

[0138] Case 1 of this invention: A fault occurs at f1 in the diagram. Since the fault point is far from the distributed power source area, no significant voltage and frequency fluctuations occur in the area where the distributed power source is located after the fault. The original islanding identification method of islanding protection fails to identify it (such as over / under voltage and over / under frequency methods). However, the fault identification method based on negative sequence and zero sequence voltage can still identify the fault characteristics. In this case, according to the method of this invention, the flag parameters are Sig... island =0, Sig foc =1.Sig fsus =0 or 1, island protection does not activate, such as Figure 5 As shown.

[0139] Case 2 of this invention: A fault occurs at f2 as shown in the diagram. Since existing islanding identification methods cannot reliably distinguish between faulty and fault-free islanding states, the islanding identification method will also activate during faults (especially near-field faults). Thus, both fault identification and islanding identification in islanding protection will recognize the corresponding characteristics. When upstream protection A of f2 operates, an island is formed downstream. Because the f2 fault is transient, or the short-circuit current generated by the distributed power source is insufficient to support the maintenance of the arc at the fault point, the fault disappears after upstream protection A operates, thus the marked parameters are Sig... island =1, Sig foc =1.Sig fsus =0, then the islanding protection will be in operation after the fault occurs. set1 Accelerating actions, such as Figure 6 As shown.

[0140] Case 3: A fault occurs at f2 as shown in the diagram. Other scenarios are the same as in Case 2, but after upstream protection A of f2 is activated, an island is formed downstream and the fault does not disappear and persists. That is, the flag parameters are Sig. island =1, Sig foc =1.Sig fsus =1. At this time, the islanding protection operates later than the latest operating time of stage III of the line multi-level protection, so distributed power source 1 experiences a fault and after a delay t set2 The islanding protection of the distributed power source 2 upstream of the fault point will not malfunction during the fault period of f2, thus ensuring the selectivity of the islanding protection. Figure 7 As shown.

[0141] Case 4: When the system is fault-free, switch A trips unexpectedly, causing an islanding effect downstream, thus marking the parameters as Sig. island =1, Sig foc =0.Sig fsus =0, islanding protection does not require coordination with line protection, automatic safety devices, etc., and operates after a 2-second delay according to the latest operating time. Figure 8 As shown.

[0142] This invention proposes a method for islanding protection based solely on local measurement of electrical quantities to identify four types of fault characteristics. Furthermore, by combining this method with existing islanding identification methods, a more sensitive, fast, and selective islanding protection system is formed.

[0143] This invention, through fault feature identification, enhances the coordination between islanding protection and line protection and automatic safety devices while maintaining basic functions, thereby improving the sensitivity, speed, and selectivity of islanding protection. Specifically: a) It does not operate when islanding is not identified; b) When islanding is identified, a fault occurs and is held, the islanding protection operates later than the line protection, especially to avoid the islanding protection on the power supply side malfunctioning before the line protection operates, causing excessive disconnection of distributed power sources; c) When islanding is identified, a fault occurs but is not held, the islanding protection accelerates its operation, exceeding the minimum time required for low-voltage fault ride-through control, and should operate earlier than the time for checking no voltage and not checking reclosing to avoid reclosing failure or impact; d) When islanding is identified but a fault has not occurred, it is judged to be an islanding caused by non-fault events such as switch tripping. The islanding protection has no specific coordination requirements, and according to the latest operating time recommended by relevant standards, the islanding protection operates with a 2-second delay after identifying the island.

[0144] Figure 9 This is a structural diagram of a local islanding protection system for a distribution network based on fault characteristics, according to a preferred embodiment of the present invention.

[0145] like Figure 9 As shown, this invention provides a local islanding protection system for distribution networks based on fault characteristics. The system includes:

[0146] The judgment unit determines the fault characteristics of the distribution network through a fault characteristic identification method for islanding identification;

[0147] The first execution unit is used to perform islanding protection actions on the distribution network when it is determined that the fault characteristics meet one of the fault characteristic identification criteria and that islanding has occurred in the distribution network. The judgment unit 901 is also used to: determine the fault characteristics using a fault characteristic identification method oriented towards islanding identification; and when it is determined that the fault characteristics meet at least one of the fault characteristic identification criteria at time t0, set the fault generation flag parameter Sig... foc Set the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set from 0 to 1;

[0148] The first execution unit 902 is also used for: in Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0;

[0149] The second execution unit 903 is used to: if Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus When t = 0, there is a waiting delay. When the delay t is reached, starting from time t0... set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

[0150] Preferably, the fault characteristic identification criteria include severe fault identification, and the fault characteristics of the distribution network include measured electrical quantities:

[0151] When the measured electrical quantities at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network:

[0152] U1 / U N ≤0.5 (1)

[0153] Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

[0154] Preferably, the fault feature identification criteria for island identification include non-critical fault identification:

[0155] When the measured electrical quantities at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network:

[0156] U1 / U N >0.5

[0157] Non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

[0158] Preferably, the method for identifying two-phase-to-phase short-circuit faults and two-phase-to-ground faults in non-serious fault identification is as follows:

[0159] When the measured electrical quantity at the island protection installation point satisfies one of the following two equations, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault:

[0160] U2 / U N >U set,2ph (2)

[0161]

[0162] Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

[0163] Preferably, the method for identifying single-phase ground faults in non-serious fault identification is as follows:

[0164] When the measured electrical quantities in the measurement information at the island protection installation location satisfy the following formula, it is judged as a single-phase ground fault:

[0165] 3ΔU0 / U N ≥U set,1ph (5)

[0166] Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

[0167] According to another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a method for local islanding protection of a distribution network based on fault characteristics.

[0168] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0169] The aforementioned computer-readable storage medium; and

[0170] One or more processors for executing a program in a computer-readable storage medium.

[0171] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, 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. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0172] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0173] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0174] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0175] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0176] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0177] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0178] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A method for local islanding protection of distribution networks based on fault characteristics, characterized in that, The method includes: Fault characteristics of the distribution network are determined by fault feature identification methods for island identification. When it is determined that the fault characteristics meet one of the fault characteristic identification criteria, and it is determined that islanding has occurred in the distribution network, islanding protection action is performed on the distribution network.

2. The method according to claim 1, characterized in that, The fault feature identification method for islanding identification determines fault features; when a fault feature satisfies one of the fault feature identification criteria and islanding is determined to have occurred, islanding protection actions are performed on the distribution network, including: Fault characteristics are determined using a fault feature identification method for island identification. When a fault feature is determined to satisfy at least one of the fault feature identification criteria at time t0, the fault generation flag parameter Sig is set. foc Set the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set from 0 to 1; In Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0.

3. The method according to claim 2, characterized in that, If Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus =0 after: Waiting delay, when the delay t is reached from time t0. set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

4. The method according to claim 1, characterized in that, The fault characteristic identification criteria include severe fault identification, and the fault characteristics of the distribution network include measured electrical quantities: When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network: U1 / U N ≤0.5 (1) Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

5. The method according to claim 4, characterized in that, The fault feature identification criteria for island identification include non-critical fault identification: When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network: U1 / U N >0.5 The non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

6. The method according to claim 5, characterized in that, The identification method for the two-phase short-circuit fault and the two-phase ground fault in the non-serious fault identification is as follows: When the measured electrical quantities in the measurement information at the island protection installation point meet one of the following two conditions, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault: U2 / U N >U set,2ph (2) Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

7. The method according to claim 5, characterized in that, The method for identifying single-phase ground faults in the non-serious fault identification process is as follows: When the measured electrical quantities in the measurement information at the island protection installation location satisfy the following formula, it is judged as a single-phase ground fault: 3ΔU0 / U N ≥U set,1ph (5) Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

8. A local islanding protection system for distribution networks based on fault characteristics, characterized in that, The system includes: The judgment unit determines the fault characteristics of the distribution network through a fault characteristic identification method for islanding identification; The first execution unit is used to perform islanding protection actions on the distribution network when it is determined that the fault characteristics meet one of the fault characteristic identification criteria and that islanding has occurred in the distribution network.

9. The system according to claim 8, characterized in that, The judgment unit is further configured to: determine fault features using a fault feature identification method for island identification; and when it is determined that the fault features satisfy at least one of the fault feature identification criteria at time t0, set the fault generation flag parameter Sig... foc Set the value from 0 to 1 and maintain it, and set the fault persistence flag parameter Sig. fsus The Sig value is set from 0 to 1, and Sig is set when the fault feature identification criterion is not met at any time. fsus Reset to 0; when a fault occurs, the flag parameter Sig foc When the memory time of setting 1 reaches time T, a fault flag parameter Sig will be generated. foc Reset to 0; use an island detection method to determine island characteristics; when an island is detected, set the island formation flag parameter Sig. island Set from 0 to 1; The first execution unit is further configured to: in Sig island During the period of =1, if the island disappears, then Sig island Immediately reset to 0; if Sig island Keep it at 1 and wait for delay t set1 After that, Sig island =1,Sig foc =1,Sig fsus When = 0, the island protection will activate immediately, and the flag parameter Sig will be changed. foc Sig fsus Sig island Reset to 0; 10. The system according to claim 9, characterized in that, The system further includes a second execution unit, used for: If Sig island Keep it at 1 and wait for delay t set1 After that, Sig does not satisfy island =1,Sig foc =1,Sig fsus When t = 0, there is a waiting delay. When the delay t is reached, starting from time t0... set2 Subsequently, the island protection mechanism immediately took action, simultaneously setting the flag parameter Sig. foc Sig fsus Sig island Reset to 0.

11. The system according to claim 9, characterized in that, The fault characteristic identification criteria include severe fault identification, and the fault characteristics of the distribution network include measured electrical quantities: When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for severe fault identification, and a severe fault has occurred in the distribution network: U1 / U N ≤0.5 (1) Where U1 represents the positive sequence voltage amplitude in the electrical quantities measured at the islanding protection installation location, U N This indicates the system's rated voltage.

12. The system according to claim 9, characterized in that, The fault feature identification criteria for island identification include non-critical fault identification: When the measured electrical quantities in the measurement information at the island protection installation point meet the following conditions, it is determined that the fault characteristics meet the criteria for non-serious fault identification, and a non-serious fault has occurred in the distribution network: U1 / U N >0.5 The non-serious faults include: two-phase short circuit faults, single-phase ground faults, and two-phase ground faults.

13. The system according to claim 12, characterized in that, The identification method for the two-phase short-circuit fault and the two-phase ground fault in the non-serious fault identification is as follows: When the measured electrical quantities in the measurement information at the island protection installation point meet one of the following two conditions, it is determined to be a two-phase phase-to-phase short-circuit fault or a two-phase ground fault: U2 / U N >U set,2ph (2) Where U2 and I2 represent the negative sequence voltage and negative sequence current amplitudes at the islanding protection installation location, respectively; U N and I N These represent the system rated voltage and the rated current of the distributed power source downstream of the islanding protection, respectively; U set,2ph For the discrimination criteria of two-phase-to-phase short-circuit faults; U op,2 To enable the set value.

14. The system according to claim 12, characterized in that, The method for identifying single-phase ground faults in the non-serious fault identification process is as follows: When the measured electrical quantities in the measurement information at the island protection installation location satisfy the following formula, it is judged as a single-phase ground fault: 3ΔU0 / U N ≥U set,1ph (5) Where ΔU0 represents the zero-sequence voltage change at the islanding protection installation location, U set,1ph These are the criteria for single-phase grounding faults.

15. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-7.

16. An electronic device, characterized in that, include: The computer-readable storage medium as described in claim 15; as well as One or more processors for executing a program in the computer-readable storage medium.

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