Power distribution network fault analysis method and system considering wiring form and automation level

Abstract

This invention discloses a method and system for distribution network fault analysis considering wiring configurations and automation levels, belonging to the field of distribution network fault result analysis technology. The method includes: based on a distribution network fault mode table, obtaining the outage and transfer times according to the fault switch number and related fault modes; based on the outage load, obtaining the outage load and the transfer switch number at that time segment according to the outage and transfer times; transferring power through the ATS switch set in the switch number, and for loads that cannot be transferred by the ATS, transferring power through tie switches to obtain the outage load, and analyzing the consequences of the distribution network fault. The distribution network fault analysis technology designed in this invention is closer to the actual operation of the distribution network, the evaluation results are closer to reality, and it can handle distribution network systems with different complex wiring configurations, providing new technical insights for the planning and operation of distribution networks.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault analysis technology, and more specifically, to a power distribution network fault analysis method and system that takes into account wiring configuration and automation level. Background Technology

[0002] The distribution network, located at the end of the power system, serves as a crucial connection between the transmission network and low-voltage users, playing a vital role in ensuring power supply, supporting economic and social development, and improving people's livelihoods. Statistics show that 80% of power outages originate from distribution network failures.

[0003] With the rapid development of my country's economy and the continuous improvement of residents' living standards, urban areas are expanding, leading to a surge in the number and wider distribution of components in power distribution networks. These components are interconnected through radial networks of varying shapes, increasing the probability of potential faults. Considering the significant role of power distribution network automation systems in improving power supply reliability through functions such as fault detection and diagnosis, fault isolation and recovery, load management, and network optimization, they are widely used in power distribution networks. However, this also makes the process of analyzing the consequences of power distribution network faults more complex. How to conduct timely and effective consequence analysis after a power distribution network fault, reduce power outage losses and impacts, and provide scientific and reasonable technical support and theoretical basis for power distribution network operation and maintenance, fault repair, and safe operation is a current research focus.

[0004] Existing technologies have conducted extensive research and analysis on the consequences of distribution network faults, providing some technical support and theoretical basis for distribution network operation scheduling and fault repair. However, most researchers currently only consider the impact of the existing distribution network structure (wiring configuration) on distribution network reliability. For example, the reliability index based on linear expressions proposed in existing technologies is only applicable to purely radial networks and cannot be applied to distribution networks with tie switches and backup lines. Although existing technologies have added the impact of protection systems, circuit breakers, switches, and other equipment to the reliability index research, they have not considered the intelligent reconfiguration of the network structure by distribution automation. That is, after a distribution network fault occurs, automatic fault isolation can be achieved through feeder terminal devices, automatic transfer switches, and other equipment to improve the reliability of the distribution network. On the other hand, some studies only consider the impact of distribution network automation systems on the consequences of distribution network faults. For example, they take distribution network automation systems composed of automation equipment, centralized feeder automation, and recloser-type feeder automation as examples to conduct consequences analysis of distribution network faults, without considering the impact of the specific wiring form of the distribution network, nor the impact of the difference in automation level on fault recovery time: if an ATS automatic transfer switch is configured, it is in the millisecond level; if a recloser-type FTU is configured, it is in the second level; if a remote control FTU is configured, it is in the minute level; and if on-site operation is required, it is in the hour level.

[0005] Current technologies in distribution network fault analysis generally only consider simple networks, or simplify complex networks into ordinary radial networks, or only consider the impact of distribution network automation systems on distribution network reliability, while there is very little research on the impact of differences in automation levels. This results in data calculated by previous fault consequence assessment methods being far from the actual distribution network results. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this invention is to provide a power distribution network fault analysis technique that considers wiring configuration and automation level, aiming to provide new technical insights for the planning and operation of power distribution networks.

[0007] To achieve the above technical objectives, this application provides a method for fault analysis of distribution networks that considers wiring configuration and automation level, including the following steps:

[0008] Based on the fault mode table of the distribution network, the power outage and power transfer time are obtained according to the fault switch number and related fault mode.

[0009] Based on the power outage load, the power outage load and the switch number of the power transfer are obtained according to the power outage and transfer time.

[0010] Power is transferred through the ATS switch set in the switch number, and for loads that cannot be transferred by the ATS, power is transferred through the tie switch to obtain the outage load and analyze the consequences of the distribution network fault.

[0011] Preferably, in the process of obtaining the fault mode table, based on the original information of the distribution network consisting of switches, feeders and equipment, the unique number of each device is obtained, and special switch types are filtered out according to the set identifier to obtain the total path table and the fault mode table. The special switch types include ATS and normally open transfer switch.

[0012] Preferably, in the process of obtaining the power outage and transfer time, the connection relationship between each node in the power grid is obtained according to the total path table, and the fault mode and corresponding power outage time of different switches, feeders and equipment are obtained according to the fault mode table.

[0013] Preferably, during the process of obtaining the switch number, the faulty switch in the power grid and its corresponding fault information are read, the selected faulty switch is checked to see if it has an FTU, and the switch information with the FTU is stored; at the same time, all tie switches in the power grid are screened out, and it is determined whether these tie switches have remote power transfer capability, thereby obtaining the switch number composed of the FTU and the tie switch.

[0014] Preferably, when acquiring the power outage load, the maximum outage time max_T of each power outage area is calculated based on the fault information and the topology of the power grid, and for each time segment t, the load of the power outage area and the load that can be transferred through the tie switch are calculated to acquire the power outage load.

[0015] Preferably, when acquiring the power outage load, it is checked whether there is an ATS device in the power grid. If there is an ATS device, the power grid state after the ATS is activated is simulated, and the power outage load after the activation is calculated. Based on the status of the tie switch and the transfer capacity, it is determined whether the power outage load can be transferred to other feeders. If it can be transferred, the power outage load after the transfer is calculated. If it cannot be transferred, the current power outage load remains unchanged.

[0016] Preferably, when analyzing the consequences of a power distribution network fault, it is checked whether the current time t exceeds the maximum outage time max_T. If it does, the outage load set for each time segment t is output; if it does not exceed, t is incremented by 1, and for each time segment t, the load of the outage area and the load that can be transferred through the tie switch are calculated to continue to obtain the outage load.

[0017] This invention discloses a power distribution network fault analysis system that considers wiring configuration and automation level, comprising:

[0018] The data acquisition module is used to obtain the fault mode table of the distribution network;

[0019] The first analysis module is used to obtain the power outage and power transfer time based on the fault mode table of the distribution network, according to the fault switch number and related fault mode.

[0020] The second analysis module is used to obtain the power outage load and the switch number of the power transfer in the time segment based on the power outage load and the power outage and transfer time.

[0021] The third analysis module transfers power through the ATS switch set in the switch number, and for loads that cannot be transferred by the ATS, it transfers power through the tie switch to obtain the outage load and analyze the consequences of the distribution network fault.

[0022] The present invention discloses the following technical effects:

[0023] This invention not only considers the impact of wiring configuration when analyzing the consequences of power distribution network faults, but also takes into account the differences in automation levels in actual power distribution networks. This makes the analysis more closely reflect the actual operating conditions of power distribution networks, and the evaluation results are closer to reality. Furthermore, it can handle power distribution network systems with different complex wiring configurations, providing new technical insights for the planning and operation of power distribution networks. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the method described in this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] This invention provides a method for analyzing the consequences of power distribution network faults, taking into account wiring configurations and automation levels, comprising the following steps:

[0028] 1) Data reading and preprocessing:

[0029] Read the original information of switches, feeders, and equipment to obtain the unique number of each device. And filter out special switch types such as ATS and normally open transfer power supply switches according to the set identifier.

[0030] Read the total path table and fault mode table output by the minimum path program.

[0031] 2) Fault handling and time generation:

[0032] The fault switch number and related fault mode are read from the fault input table. The power outage time and the time for switching power supply are generated by the power outage time calculation program (which is also related to the line structure, such as whether the switching power supply can be ordered by the dispatcher or can only be manually switched on site). The maximum simulation time is also generated.

[0033] 3) Preprocessing stage at each time step:

[0034] Based on the power outage and power transfer times generated above, the power outage load and power transfer switch numbers for that time segment are generated by the power outage load calculation program.

[0035] 4) ATS transfer portion:

[0036] Based on the searched set of all ATS switches (if any), determine whether a load power failure will cause the ATS to activate and then transfer power.

[0037] 5) Interconnection switch power supply section:

[0038] For loads that cannot be supplied by the ATS, the load is supplied through the tie switch (if it can be supplied), and the power outage load under that section is finally output.

[0039] like Figure 1 The method flowchart is shown in detail below:

[0040] 1) Read information tables for switches, feeders, and equipment:

[0041] Retrieves detailed information about switches, feeders, and equipment in the power grid from the database. This information includes the location, status, and feeder to which the switch belongs.

[0042] 2) Preprocess the data:

[0043] The read data is cleaned and organized to remove invalid data, correct erroneous data, and ensure the accuracy and integrity of the data.

[0044] 3) Read the path summary table, fault mode table, etc.:

[0045] Read the power grid path table to understand the connection relationships between nodes in the power grid; at the same time, read the fault mode table to understand the fault modes and corresponding outage times of different switches, feeders and equipment.

[0046] 4) Read the fault switch and corresponding fault information:

[0047] Read the fault switches in the power grid and their corresponding fault information. This information is used to determine the status of the fault switches.

[0048] 5) Screening FTU switches:

[0049] Check if the selected fault switch has an FTU (Feeder Terminal Unit) and store the switch information with the FTU for later use.

[0050] 6) Filter out the contact switch and whether it can be transferred:

[0051] All tie switches in the power grid are screened out, and it is determined whether these tie switches have the ability to transfer power, that is, whether the load in the power outage area can be transferred to other feeders.

[0052] 7) Filter out and save ATS:

[0053] All ATS devices in the power grid are screened out and their information is stored for later use.

[0054] 8) Generate the outage time max_T based on the fault mode table:

[0055] Based on the fault information and the topology of the power grid, the maximum outage time max_T for each outage area is calculated.

[0056] 9) Calculate and obtain the power outage load and the load transferred at time t:

[0057] For each time segment t, calculate the load in the power outage area and the load that can be transferred through the tie switch.

[0058] 10) Determine if an ATS exists:

[0059] Check if an ATS device exists in the power grid. If it does, proceed to the next step; otherwise, skip the next step.

[0060] 11) Calculate the power outage load after ATS operation:

[0061] If an ATS device exists, simulate the power grid state after the ATS is activated and calculate the power outage load after the activation.

[0062] 12) Determine if the supply can be transferred:

[0063] Based on the status and transfer capacity of the tie switch, determine whether the out-of-power load can be transferred to other feeders.

[0064] 13) Calculate and obtain the power outage load after the power transfer:

[0065] If power can be transferred, calculate the outage load after the transfer; if power cannot be transferred, keep the current outage load unchanged.

[0066] 14) Determine if the maximum power outage time max_T has been reached:

[0067] Check if the current time t exceeds the maximum power outage time max_T. If it does, proceed to the next step; otherwise, increment t by 1 and return to step 9 to continue the calculation.

[0068] 15) Output the set of power outage loads at each time segment:

[0069] When the maximum power outage time max_T is reached, output the set of power outage loads for each time segment t, including information such as power outage loads and loads transferred to power supply.

[0070] Based on the above-mentioned method flow, the specific process of the method designed in this invention is as follows:

[0071] 1. Reliability evaluation indicators:

[0072] Reliability assessment indicators for power distribution systems are the foundation of reliability analysis. By calculating these indicators, the reliability level of the system is quantitatively evaluated. Power distribution system reliability indicators can be categorized into user reliability indicators and system reliability indicators based on the evaluation object. User reliability indicators describe the power supply reliability at each load point in the power distribution system, while system reliability indicators reflect the system's power supply capacity.

[0073] 1.1 User reliability indicators:

[0074] Based on the network structure and component parameters of the distribution network, the reliability level of each load point in the system is evaluated: the annual average number of faults (denoted as λ); the annual average fault time (denoted as r); and the average fault duration (denoted as U).

[0075] 1.2 System Reliability Indicators:

[0076] To reflect the overall reliability level of the power distribution system, based on the load point reliability index, some performance indicators are defined to characterize power outage statistics from the system perspective: System Average Outage Frequency Index (SAIFI); System Average Outage Duration Index (SAIDI); User Average Outage Duration Index (CAIDI); Average Power Supply Availability Index (ASAI); Expected Power Shortage (EENS); Average Expected Power Shortage (AENS).

[0077] 2. Analysis of the consequences of power distribution network faults:

[0078] 2.1 Impact of Wiring Configuration on Fault Consequence Analysis of Distribution Network

[0079] Medium and low voltage distribution networks primarily operate in open-loop ring network mode and can generally be treated as radial systems. Failure Mode and Effects Analysis (FMEA) is employed as the reliability analysis method. By analyzing all possible component failures or malfunctions, the set of failure modes of the system is identified, the impact on load points is determined, and the reliability of the load points is derived. In the power industry, parameters such as Average Incoming Power Outage Time (AIHC), Average Incoming Power Supply Reliability (RS), and Average Incoming Power Outage Frequency (AITC) are commonly used as basic evaluation indicators. Many reliability evaluation indicators exist for medium and low voltage distribution systems, and the selection must be based on the specific circumstances. To reflect the importance and severity of distribution network outages, RS is typically chosen as the evaluation indicator, with the formula: [Formula omitted for brevity].

[0080] RS=(T v / T s )×100%(2.1)

[0081] In the formula: T vIt is the sum of the actual power supply time during the statistical period; T s It refers to the total power supply time during the statistical period.

[0082] AITC = Total number of power outages per user / Total number of users = ∑U i N i =λ2×R×N×r3×λ3,

[0083] but

[0084]

[0085] In the formula: N i t represents the number of users at load point i; i Let be the average annual downtime of load point i.

[0086] In the reliability analysis and calculation of power distribution networks, the main approach is usually to use the failure rate and mean time of repair of four types of equipment: lines, ring network switches, circuit breakers, and busbars, to calculate the number of users experiencing power outages due to different equipment failures, and then calculate the outage frequency and power supply reliability based on the number of users experiencing power outages.

[0087] 1) Duration of power outage for users during busbar faults. The line busbar consists of only one segment in different modes, and the impact of the number of line segments is negligible. The calculation formula is as follows:

[0088] ∑U i N i =λ1×N×r1(2.3)

[0089] In the formula: λ1 is the average failure rate of the bus (times / unit × year); N is the total number of users on the line; r1 is the average repair time of the bus (hours / time).

[0090] 2) Duration of power outage for users during line faults. If a line fault occurs, it is necessary to analyze different segmented faults. When a line fault occurs, the load carried by the line does not meet the conditions for timely transfer. Therefore, if the distribution line is a single radial line divided into three segments, and the first segment fails, the number of affected users is N, and the average repair time of the line is the average outage time. Similarly, if the second or third segment fails, the number of affected users will be 2 / 3N and 1 / 3N respectively, and the average outage time will be the average repair time of the line. The calculation formulas are summarized below.

[0091] When radiating a single radiation

[0092]

[0093] In the formula: R is the power supply radius of the line, km; num is the number of sections of the line; λ2 is the average failure rate of the line, times / km×year; r2 is the average repair time of the line, hours / time; t is the switching time of the line, hours / time.

[0094] In single contact

[0095]

[0096] In other wiring configurations, different devices after a fault can be converted into single-radio and single-tie configurations before calculations are performed separately.

[0097] 3) Duration of power outage for users due to circuit breaker failure. If each 10kV line corresponds to only one outgoing circuit breaker, the circuit breaker failure rate under normal operating conditions is usually expressed as the failure-to-operate rate. If the failure-to-operate rate of the circuit breaker is taken as 2.11%, and the power outage caused by the circuit breaker failure is based on the line outage, then its theoretical calculation formula is:

[0098] ∑U i N i =λ²×R×N×r³×λ³(2.6)

[0099] In the formula: λ2 is the average failure rate of the line, times / km×year; λ3 is the average failure rate of the circuit breaker, times / unit×year; r3 is the average repair time of the circuit breaker, hours / time; R is the power supply radius of the line, km.

[0100] 4) Duration of power outage for users when a ring main unit fails. If the ring main unit installed on the cable line is configured as a sectionalizing device, and the load switch installed on the overhead line is configured as a sectionalizing device, the theoretical calculations assume that the formulas also apply to cable lines, and the load switch is taken as the object of study. Under different network wiring modes, the duration of power outage for users when a load switch fails can be divided into two types: single-radial and single-tie.

[0101] In the case of single radiation:

[0102]

[0103] In the formula: λ4 is the average failure rate of the load switch, times / unit × year; r4 is the average repair time of the load switch, hours / time; t is the switching time of the line, hours / time.

[0104] For single contact:

[0105]

[0106] In other wiring configurations, different devices after a fault can be converted into single-radio and single-tie configurations before calculations are performed separately.

[0107] If load switches, circuit breakers, cable lines or overhead lines and busbars fail simultaneously, the average outage time and the number of affected users can be calculated using the corresponding formulas for AIH, AITC, and CRS, along with the corresponding reliability indicators.

[0108] 2.2 Impact of Distribution Automation on Distribution Network Fault Consequences:

[0109] Distribution network automation technology refers to a technical system that utilizes advanced communication, control, and information technologies to achieve automated management and operation of distribution networks. This technology introduces intelligent devices, sensors, communication networks, and automation algorithms to enable real-time monitoring, remote control, and data processing of all aspects of the distribution network system, thereby improving the reliability and efficiency of power supply from the distribution network.

[0110] 2.2.1 Classification of Automation Modes:

[0111] Distribution automation systems are integrated systems for remote, real-time monitoring, coordination, and control of distribution network components and equipment. They represent the application of modern computer and communication technologies in distribution network monitoring and control. Based on the different equipment upgrades and communication system requirements of distribution automation construction, distribution network construction modes are categorized into three types: fault location automation mode, local automation mode, and centralized automation mode. Distribution automation systems can quickly locate and isolate faulty sections after a fault occurs, reducing the time spent on fault finding and isolation. However, the speed and effectiveness of fault handling and power transfer to non-faulty areas vary depending on the distribution automation mode.

[0112] Because there are many distribution automation modes, with different operating principles and functional characteristics, conducting reliability assessments by considering all automation modes individually would be cumbersome. Based on the varying degrees of impact of distribution automation modes on reliability, modes with similar levels of impact are grouped together to reduce the workload of reliability assessments. For example, the recloser mode and the centralized semi-automated "three-remote and four-remote" mode have the same distribution network operating parameters and similar automation improvement effects; therefore, they are grouped together in reliability assessment. For intelligent distributed systems, fault isolation and power transfer can generally be completed within 20-30 seconds, and reliability indicators only count power outages longer than 3 minutes; therefore, the theoretical reliability in this case is 100%, and it does not need to be considered in reliability assessments. The classification results are shown in the table below.

[0113] Table 1 Classification of Power Distribution Automation Modes

[0114]

[0115] 2.2.2 Fault Impact State Classification:

[0116] When a feeder fault occurs, the circuit breaker trips. Nodes downstream of the tripped circuit breaker and other feeder nodes are unaffected by the fault, while nodes upstream of the tripped circuit breaker are all affected. After disconnecting the corresponding switching equipment to isolate the fault point, the affected nodes may regain power through the feeder's own power supply, or they may regain power through a tie line transfer, or they may experience a power outage due to the inability to transfer power. Therefore, without considering the impact of distribution automation, the fault impact status of feeder load nodes can be divided into four types: fault-free state, fault repair state, fault isolation state, and fault transfer state.

[0117] The impact of distribution automation on the reliability of the distribution network is mainly reflected in the speed of fault location and isolation and power transfer. Therefore, both fault location and isolation time and fault transfer time are affected. The specific degree of impact of the four automation levels in Table 1 on fault location and isolation time and fault transfer time varies. If the distribution network contains automation switching equipment of all four levels (A to D), the disconnection operation time of different levels of automation switching equipment differs significantly. In the event of a fault, the switching equipment with a higher degree of automation often operates first. Therefore, the power restoration process after a fault will be carried out in stages.

[0118] When considering the impact of distribution automation, based on the different speeds of fault location and isolation and fault transfer, the following 10 fault impact states can be categorized: fault unaffected state, fault repair state, A-D level fault isolation state corresponding to A-D level automation mode, and A-D fault transfer state. Since the "fault unaffected state" is not required in distribution network reliability assessment, only the latter nine fault impact states will be discussed.

[0119] 2.2.3 Distribution Network Reliability Assessment:

[0120] Based on the different impacts of a fault in node i on the state of node j, define a set of fault enumeration nodes. The set of faulty nodes that cause node j to be in a fault repair state The set of faulty nodes that cause node j to be in fault isolation state A to D and the set of fault nodes that cause node j to be in the A-D fault transfer state. The value of k represents the degree of impact of different node failures on node j. For example, when k is 1, the node set... The failure of any node in the set causes node j to be in fault isolation state A. The process is traversed to form the network. The equivalent reliability parameter for region node j is defined as the annual equivalent outage rate F. j Equivalent downtime D per year j The calculation formula is:

[0121]

[0122]

[0123] In the formula: λ(i) (k) For a set of nodes The equivalent failure rate of the set of electrical devices contained in node i of a certain region; T(i) (k) For the corresponding power outage time; t gm t gal t ga2 and t ga3 These represent the isolation operation time for the corresponding level of automated switches; t zm t zal t za2 and t za3 These represent the transfer operation time for the corresponding level of automation switch; λ i and t i It can be calculated based on the set of electrical equipment at region node i; λ m,i , λ f,i , λ l,i and λ t,i These represent the failure rates of feeders, fuses, distribution transformer branches, and transformers at regional nodes, respectively; p f t represents the reliable operation probability of the fuse; m t l t f and t t For the corresponding equipment repair time; n M n L n F and n T This represents the corresponding number of devices.

[0124] For each load point in the region, the reliability parameters of the load point can be obtained by considering the impact of reliable operation of the load point fuse based on the equivalent reliability parameters of the region nodes. For load point d in region node j, its annual failure outage rate F j (d) and annual outage time D j (d) The calculation formulas are respectively

[0125] F j (d)=F j +Δλ=F j +p f (λ 1,d +λ t,d (2.15)

[0126] D j (d)=D j +Δt=D j +p f (λ 1,d t1+λ t,d tt (2.16)

[0127] In the formula: Δλ and Δt are the corrections for the load point fault outage rate and outage time, respectively, when considering the reliable operation of the fuse; λ 1,d , λ t,d These represent the failure rates of the distribution transformer branch and the transformer itself at load point d, respectively. System reliability indicators can be obtained from the load point reliability parameters. The calculation formulas for the system's average annual power outage frequency (SAIFI), average annual power outage duration (SAIDI), system power supply reliability rate (RS), and average annual power outage shortage (AENS) are as follows:

[0128]

[0129] RS=(1-SAIDI / 8760)×100%(2.19)

[0130]

[0131] Where: N u,d α is the number of users at load point d; d For the distribution transformer load rate; S d N1 represents the transformer capacity; N2 represents the number of load nodes.

[0132] 2.3 Methods for analyzing the consequences of power distribution network faults, considering wiring configuration and automation level:

[0133] 2.3.1 Improved Dynamic Minimum Path Method:

[0134] Existing minimum path algorithms mainly employ three methods for path formation: the connection matrix method, depth-first search, or a combination of both. All of these methods require sequentially analyzing each user's power supply source and the minimum path and power supply branches from that source to the user. The timing is determined by assigning corresponding failure rates and recovery times to components based on their types. The minimum power supply path and power supply branches for each user are obtained by analyzing the component correlation matrix of the distribution network. The impact of the power supply branches on user reliability is then equated to the minimum power supply path. Finally, through series calculations of the minimum power supply paths and parallel calculations of different minimum power supply paths, the user's power supply reliability is calculated.

[0135] The improved minimum path algorithm simplifies the search calculation process and reduces time by analyzing the impact of minimum path elements from the power source to the user and branch elements on user reliability. Improvements are made in several aspects, including simplified topology data processing, power transfer principles, and power supply path formation.

[0136] (1) Topology data simplification

[0137] With the widespread application of GIS (Geographic Information System) in power distribution networks, real-time and accurate power distribution network topology data can be obtained from GIS systems. The topology data of a power distribution network GIS system consists of primary-side component data items, and is stored in groups according to the structure of city, district, bureau, substation, station, line, and component. The data item content includes the component number, component type, component inlet node number, and component outlet node number, etc.

[0138] Components affecting distribution network reliability indicators include critical components such as distribution transformers, circuit breakers, load switches, overhead lines, cables, and substation busbars. In addition, the distribution network GIS system topology data also contains a large number of non-critical components such as poles and equipment fault detectors, which do not affect reliability calculations. To reduce the number of components in the component database and improve retrieval efficiency, redundant data is processed while ensuring system connectivity, thereby simplifying the distribution network topology data.

[0139] The main simplification approach is as follows: ① Identify non-critical components in the component list by component type and obtain the node numbers of the input and output terminals of the non-critical components; ② Assign all the input and output terminal node numbers of the component to the same new number (that is, treat the input and output terminal nodes of the component as the same new node); ③ Delete the component from the component list; ④ Finally, the only component types remaining are switchgear such as low-voltage busbars, transformers, overhead lines, cables, circuit breakers, load switches, tie switches, and ATS (automatic transfer switch).

[0140] (2) Principle of Sub-supply:

[0141] As distribution networks grow larger, numerous interconnecting switches are used to improve overall power supply reliability, forming a closed-loop design and open-loop operation mode. However, in minimum path calculations, the interconnecting function of these switches needs to be considered to obtain all possible power supply paths to the load. Therefore, based on the power transfer methods used in actual distribution network operation and maintenance, the power transfer principles are determined as follows:

[0142] 1) There are at most two tie switches in all possible power supply paths:

[0143] Considering the need for convenient and rapid power restoration during power transfer operations, power is generally not supplied through more than two tie switches for a non-faulty area. In particular, if on-site power transfer is required, the power transfer time will be greatly increased. Only when both tie switches are equipped with FTUs with remote control can the requirement for rapid power transfer be met.

[0144] 2) Selection of power transfer substations:

[0145] When selecting feeders for power transfer, feeders within the same substation should be selected first. Only when all constraints are not met should feeders within adjacent substations be selected, so as to make full use of the station's redundant resources and reduce the decline in power supply reliability caused by complex inter-station operations.

[0146] 3) Selection of power supply tie switch:

[0147] Similar to power transmission and distribution networks at various voltage levels, the branch lines on each feeder are also classified (main line, primary, secondary, etc.). The capacity of the tie switches (if any) configured on each branch line corresponds to the level of the branch line, decreasing from large to small. Therefore, when transferring power, it can only be transferred from the tie point of the same or higher level branch to the area where power needs to be restored.

[0148] 4) Capacity constraints:

[0149] Adjacent feeders should prioritize meeting the maximum load of their own feeder and should have a certain margin. Only if there is redundant capacity can the feeder be transferred to another feeder. At the same time, the transferred capacity provided cannot exceed the maximum transmission capacity allowed by the tie line.

[0150] 5) Constraints on the number of transfer lines:

[0151] If a non-faulty area cannot be completely supplied by one tie line, a maximum of two tie lines can be used for supply transfer. If the power supply to the entire area still cannot be restored at this time, the load will be cut off according to the importance of the load, while ensuring the power supply to important users, until it is less than the supply transfer capacity.

[0152] (3) Formation of the power supply path:

[0153] Similar to the conventional least-path method for finding power supply paths, this method starts with the load point and ends with the power source point (substation), searching for all possible power supply paths between each load point and each power source point. Taking a specific load point as an example, the specific approach is as follows:

[0154] 1) Change all tie switches from normally open to normally closed;

[0155] 2) Starting from the initial node, find all the elements connected to that node according to their numbers and store them in matrix A for later use;

[0156] 3) Enumerate each element in matrix A sequentially, search for the elements connected to it, and compare them with the elements in A. If the numbers match, discard them and store the rest in different columns of matrix B.

[0157] 4) If all the tie switches in 1) are changed to normally closed, the path may be trapped in a loop during the path finding process. At this time, the tie switches involved are stored, and only one tie switch is kept in closed state at a time. The above process is repeated, and the different components passed each time are recorded and stored. The process is updated each time until the power point is found.

[0158] 4) Repeat the above process continuously and store the component numbers of all components that pass through from the load point to the power supply point to form an initial power supply path table;

[0159] 5) Based on the transfer principle in (2), the initial power supply path table is screened to obtain the final path table that meets the transfer principle, which is then used as a backup for subsequent fault analysis.

[0160] 2.3.2 Fault Consequence Analysis Process:

[0161] 1) Calculation of downtime:

[0162] Based on the analysis in the previous section, and considering the differences in wiring configuration (whether a tie switch is included) and automation (whether an FTU is included), as well as the handling process of maintenance personnel, the following eight types of fault consequences and handling results can be summarized, denoted as A. 1 ~A 6 :

[0163] A 1 After a fault occurs, the power outage area cannot be resupplied. Power will be restored remotely by the dispatcher. The power outage time is 0 minutes and the power resupplied time is 0 minutes.

[0164] A 2 After a fault occurs, the power outage area can be resupplied and the resupplier switch is equipped with an FTU. The power can be resupplied remotely by the dispatcher. The original operation mode will be restored after the on-site personnel complete the inspection. The power outage time is 0 hours and the resupplier time is 2 hours.

[0165] A 3 After a fault occurs, and the FTU is unable to be remotely controlled at this time, the power outage area cannot be resupplied. The maintenance personnel will restore power on-site. The power outage time is 2 hours, and the power resupplied time is 0 hours.

[0166] A 4 After a fault occurs, the power outage area can be resupplied, but the FTU is faulty and cannot be remotely controlled. The maintenance personnel will first restore power supply on-site. The original operation mode will be restored after the inspection of the faulty FTU switch is completed. The power outage time is 2 hours and the power supply resupplier time is 2 hours.

[0167] A 5After a fault occurs, the power outage area cannot be resupplied. However, the telemetry data is incorrect, making it impossible to accurately locate the fault area. Maintenance personnel need to conduct on-site inspections to determine the power outage range and the malfunctioning switch. Then, the dispatch personnel will remotely control the switch to restore power. The power outage time is 4 hours, and the power resupplied time is 0 hours.

[0168] A 6 After a fault occurs, the power outage area can be resupplied, but the telemetry data is incorrect. After the maintenance personnel conduct a preliminary on-site inspection, the dispatch personnel will remotely control the power supply to restore power to part of the area. After the entire fault area is inspected and found to be correct, the original operation mode will be restored. The power outage time is 4 hours, and the power supply resupplied time is 2 hours.

[0169] To facilitate the incorporation of time into the improved minimum path algorithm, the time required for power outages and power transfers is calculated using a 15-minute timescale, such as A. 6 The power outage time is 4 periods, and the power supply transfer time is 2 periods, that is, the power outage time is 4 fifteen-minute periods (one hour), and the power supply transfer and restoration time is 2 fifteen-minute periods (half an hour).

[0170] If a power outage is caused by a fault at switch i, the maximum power outage calculation time t is... (i)max for:

[0171]

[0172] in Let be the power outage time under the i-th fault condition. Let be the switching time under the i-th fault condition, where the maximum value of i is the total number of faulty switches.

[0173] The total maximum power outage calculation time T max for

[0174] T max =max(t) (i)max (2.22)

[0175] 2) Calculation of load loss after fault:

[0176] Based on the maximum power outage calculation time T obtained in the previous section max Let n be the maximum time scale, and let 0 and 1 represent whether the power supply path is connected (0 means not connected, i.e., the load is lost at this time, and the opposite means connected). Let N be the maximum number of load losses caused by the fault, and let M be the number of power supply paths for each load.

[0177] First, the fault types obtained from the power distribution automation system are classified to obtain the outage load at the initial time t=0, which is the time with the most load loss and the largest outage area. Based on the final path table obtained by the improved minimum path method, the wiring configuration and the impact of automation are then considered to calculate whether each load is out of power at each time scale.

[0178]

[0179] Among them GD (i,j,k) This indicates the connection status of the j-th power supply path for the i-th initial power outage load at time k.

[0180] If GD (i,j,k) If k = 1, then there needs to be an ATS automatic transfer switch or a tie switch on the power supply path at time k to transfer the power, and at this time the load i will not lose load.

[0181] Then the unload state of load i at time k is: 0 represents unload, and 1 represents continuous power supply.

[0182]

[0183] Then the set of all unloaded items at time k is:

[0184] SFH (k) ={F (i)}F (i,k) =0(2.25)

[0185] Where F (i) This represents the i-th initial power outage load.

[0186] 3) Summary:

[0187] As can be seen from the above analysis, during the period from t=1 to t=n, if there is an ATS automatic transfer switch or a tie switch on the power supply path of load i, the power outage time will be shortened accordingly. The specific time is related to the level of automation. For example, the power outage time is 0 for an ATS switch, 2 for on-site transfer, and 1 for remote control. Therefore, the calculated power outage range at different times varies and is closely related to the wiring method and the level of automation.

[0188] This invention not only considers the impact of wiring configuration when analyzing the consequences of distribution network faults, but also takes into account the differences in automation levels in actual distribution networks. This makes it closer to the actual operation of distribution networks, and the evaluation results are more realistic. It can also handle distribution network systems with different complex wiring configurations, providing new experience for guiding the planning and operation of distribution networks.

[0189] 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.

[0190] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0191] 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.

Claims

1. A method for analyzing distribution network faults considering wiring configurations and automation levels, characterized in that: Includes the following steps: Based on the fault mode table of the distribution network, the power outage and power transfer time are obtained according to the fault switch number and related fault mode. Based on the power outage load, the power outage load and the switch number of the power transfer are obtained according to the power outage and transfer time. Power is transferred through the ATS switch set in the switch number, and for loads that cannot be transferred by the ATS, power is transferred through the tie switch to obtain the outage load and analyze the consequences of the distribution network fault. When acquiring the power outage load, the maximum outage time max_T for each power outage area is calculated based on the fault information and the topology of the power grid. For each time segment t, the load of the power outage area and the load that can be transferred through the tie switch are calculated to acquire the power outage load. When acquiring the outage load, check whether there is an ATS device in the power grid. If there is an ATS device, simulate the power grid state after the ATS is activated and calculate the outage load after the activation. Based on the status and transfer capacity of the tie switch, determine whether the outage load can be transferred to other feeders. If power can be transferred, calculate the power outage load after the transfer; If power cannot be transferred, then the current power outage load should remain unchanged; When analyzing the consequences of a power distribution network fault, check whether the current time t exceeds the maximum outage time max_T. If it does, output the set of outage loads for each time segment t. If not exceeded, t is incremented by 1, and for each time segment t, the load of the power outage area and the load that can be transferred through the tie switch are calculated to continue to acquire the power outage load; Based on different wiring methods and automation differences, and considering the handling process of maintenance personnel, the following fault consequences and handling results are derived, denoted as A1 to A6: A1: After a fault, the power outage area cannot be resupplied. The dispatcher will remotely control the switch to restore power. The power outage time is 0 hours and the power resupplied time is 0 hours. A2: After a fault, the power outage area can be transferred to another power source, and the transfer switch is equipped with an FTU. The power transfer can be carried out remotely by the dispatcher. The original operation mode will be restored after the on-site personnel complete the inspection. The power outage time is 0 hours and the transfer time is 2 hours. A3: After the fault occurs, and the FTU is faulty and cannot be remotely controlled at this time, the power outage area cannot be transferred to another power source. The maintenance personnel will restore power on-site. The power outage time is 2 hours, and the power transfer time is 0 hours. A4: After a fault, the power outage area can be resupplied, but the FTU is faulty and cannot be remotely controlled at this time. The maintenance personnel will first restore the power supply on-site. The original operation mode will be restored after the inspection of the faulty FTU switch is completed. The power outage time is 2 hours and the power supply resupplier time is 2 hours. A5: After a fault, the power outage area cannot be resupplied, but the telemetry data is incorrect, making it impossible to accurately locate the fault area. Maintenance personnel need to conduct on-site inspections to determine the power outage range and the malfunctioning switch. Then, the dispatch personnel will remotely control the switch to restore power. The power outage time is 4 hours, and the power resupplied time is 0 hours. A6: After the fault, the power outage area can be transferred to another power source, but the telemetry data is incorrect. After the maintenance personnel conduct a preliminary on-site inspection, the dispatch personnel will remotely control the transfer of power to restore power to a part of the area. After the entire fault area is inspected and found to be correct, the original operation mode will be restored. The power outage time is 4 hours, and the transfer time is 2 hours. The time required for power outages and power reshoring is calculated using a 15-minute time scale. If a power outage is caused by a fault at switch i, the maximum power outage calculation time t is... (i)max for: in Let be the power outage time under the i-th fault condition. Let be the switching time under the i-th fault condition, where the maximum value of i is the total number of faulty switches.

2. The distribution network fault analysis method considering wiring configuration and automation level according to claim 1, characterized in that: During the process of obtaining the fault mode table, based on the original information of the distribution network consisting of switches, feeders and equipment, the unique number of each device is obtained, and special switch types are filtered out according to the set identifiers to obtain the total path table and the fault mode table. The special switch types include ATS and normally open transfer switch.

3. The distribution network fault analysis method considering wiring configuration and automation level according to claim 2, characterized in that: During the process of obtaining power outage and power transfer times, the connection relationships between nodes in the power grid are obtained according to the total path table, and the fault modes and corresponding power outage times of different switches, feeders and equipment are obtained according to the fault mode table.

4. The distribution network fault analysis method considering wiring configuration and automation level according to claim 3, characterized in that: During the process of obtaining the switch number, the faulty switches in the power grid and their corresponding fault information are read, and it is checked whether the selected faulty switch has an FTU. The switch information with the FTU is stored. At the same time, all tie switches in the power grid are screened out, and it is determined whether these tie switches have remote power transfer capability, thereby obtaining the switch number composed of the FTU and the tie switch.

5. A distribution network fault analysis system considering wiring configuration and automation level, used to implement the distribution network fault analysis method considering wiring configuration and automation level as described in claim 1, characterized in that, include: The data acquisition module is used to obtain the fault mode table of the distribution network; The first analysis module is used to obtain the power outage and power transfer time based on the fault mode table of the distribution network, according to the fault switch number and related fault mode. The second analysis module is used to obtain the power outage load and the switch number of the power transfer in the time segment based on the power outage load and the power outage and transfer time. The third analysis module transfers power through the ATS switch set in the switch number, and for loads that cannot be transferred by the ATS, it transfers power through the tie switch to obtain the outage load and analyze the consequences of the distribution network fault.

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