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

Abstract

The invention discloses a power distribution network fault analysis method and system considering a wiring form and an automation level, and relates to the technical field of power distribution network fault result analysis, and the method comprises the steps: obtaining power failure and transfer time based on a fault mode table of a power distribution network according to a fault switch number and a related fault mode; on the basis of the power failure load, according to the power failure time and the transfer time, obtaining the power failure load and the transfer switch number under the time section; and carrying out transfer through the ATS switch set in the switch number, carrying out transfer through the interconnection switch on the load which cannot be transferred by the ATS, obtaining the power failure load, and analyzing the result of the fault of the power distribution network. The power distribution network fault analysis technology designed by the invention is closer to the actual operation condition of the power distribution network, the evaluation result is closer to the reality, power distribution network systems with different complex wiring forms can be processed, and new technical enlightenment is provided for planning and operation of the power distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault analysis, and in particular, to a distribution network fault analysis method and system considering wiring forms and automation levels. Background Art

[0002] The distribution network is located at the end of the power system and is the connection hub between the transmission network and low-voltage users. It plays a significant role in ensuring power supply, supporting economic and social development, and serving to improve people's livelihood. Statistics show that 80% of user power outage accidents come from distribution network faults.

[0003] With the rapid development of China's economy and the continuous improvement of residents' living standards, the urban scale is constantly expanding, the number and scale of distribution network components have increased sharply, and they are more widely distributed. They are connected through radial networks with various forms, resulting in an increased probability of potential faults. Considering the great role of the functional design of the distribution network automation system in improving the power supply reliability of the distribution network, such as fault detection and diagnosis, fault isolation and restoration, load management, and network optimization, it has been widely applied to the distribution network, but this also makes the process of distribution network fault consequence analysis more complex. How to conduct timely and effective consequence analysis after a distribution network fault, reduce power outage losses and impacts, and provide scientific and reasonable technical support and theoretical basis for distribution network operation and maintenance, fault repair, and safe operation is the focus of current research.

[0004] Existing technologies have conducted a large amount of research and analysis on the distribution network fault consequence stage, providing certain technical support and theoretical basis for distribution network operation scheduling and fault repair. However, at present, most researchers only consider the impact of the existing distribution network framework (wiring form) on the reliability of the distribution network on the one hand. For example, the reliability index composed of linear expressions proposed in the existing technology is only applicable to pure radial networks and cannot be applied to distribution networks with tie switches and standby lines. Although the impact of equipment such as protection systems, circuit breakers, and switches has been added to the research of reliability indexes in the existing technology, the intelligent reconstruction of the network framework by distribution automation has not been considered, that is, after a distribution network fault occurs, the automatic isolation of faults is achieved by relying on equipment such as feeder terminal units and automatic transfer switches to improve the reliability of the distribution network. On the other hand, some research only considers the impact of the distribution network automation system on the distribution network fault consequence analysis. For example, taking the distribution network automation systems composed of automation equipment, centralized feeder automation, recloser-type feeder automation, etc. as examples, the distribution network faults are analyzed for consequences, without considering the impact of the specific wiring form of the distribution network, nor the impact of automation level differences on the fault recovery time: if the ATS automatic transfer switch is configured in milliseconds, if the recloser-type FTU is configured in seconds, if the remote-control FTU is configured in minutes, and if on-site operation is required, it is in hours.

[0005] In the current existing technologies during the process of distribution network fault analysis, generally only simple networks are considered, or complex networks are simplified into ordinary radial networks, or only the impact of the distribution automation system on the reliability of the distribution network is considered, while the research on the impact of the difference in automation level is very little. This makes the data calculated by the previous fault consequence assessment methods quite different from the actual results of the distribution network. Summary of the Invention

[0006] To solve the above problems, the object of the present invention is to provide a distribution network fault analysis technology considering the wiring form and automation level, aiming to provide new technical inspiration for the planning and operation of the distribution network.

[0007] To achieve the above technical object, the present application provides a distribution network fault analysis method considering the wiring form and automation level, including the following steps:

[0008] Based on the fault mode table of the distribution network, obtain the power outage and transfer times according to the fault switch number and relevant fault modes.

[0009] Based on the power outage load, obtain the power outage load and the transfer switch number at this time section according to the power outage and transfer times.

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

[0011] Preferably, during the process of obtaining the fault mode table, based on the original information composed of switches, feeders, and equipment in the distribution network, obtain the unique number of each equipment, and screen out special switch types according to the set identifier to obtain the total path table and the fault mode table, where the special switch types include ATS and normally open transfer switches.

[0012] Preferably, during the process of obtaining the power outage and transfer times, according to the total path table, obtain the connection relationship between each node in the power grid, and based on the fault mode table, obtain the fault modes and corresponding power outage times of different switches, feeders, and equipment.

[0013] Preferably, during the process of obtaining the switch number, read the fault switch in the power grid and its corresponding fault information, check whether the selected fault switch has an FTU, and store the switch information with FTU; at the same time, screen out all tie switches in the power grid, and judge whether these tie switches have the remote transfer ability, and then obtain the switch number composed of FTU and tie switches.

[0014] Preferably, when obtaining the power outage load, according to the fault information and the topology of the power grid, calculate the maximum power outage time max_T of each power outage area, and for each time section t, calculate the load of the power outage area and the load that can be transferred through the tie switch to obtain the power outage load.

[0015] Preferably, when obtaining the power 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 action and calculate the power outage load after the action; according to the state and transfer capacity of the tie switch, judge whether the power outage load can be transferred to other feeders; if it can be transferred, calculate the power outage load after the transfer; if it cannot be transferred, keep the current power outage load unchanged.

[0016] Preferably, when analyzing the consequences of the distribution network fault, check whether the current time t exceeds the maximum power outage time max_T. If it exceeds, output the power outage load set of each time section t; if it does not exceed, increase t by 1, and for each time section t, calculate the load of the power outage area and the load that can be transferred through the tie switch to continue obtaining the power outage load.

[0017] The present invention discloses a distribution network fault analysis system considering the wiring form and automation level, including:

[0018] A data acquisition module for obtaining the fault mode table of the distribution network;

[0019] A first analysis module for obtaining the power outage and transfer time based on the fault mode table of the distribution network according to the fault switch number and related fault modes;

[0020] A second analysis module for obtaining the power outage load and the transfer switch number at this time section based on the power outage load according to the power outage and transfer time;

[0021] A third analysis module performs transfer through the ATS switch set in the switch number, and for the load that cannot be transferred by the ATS, after transferring through the tie switch, obtains the power outage load and analyzes the consequences of the distribution network fault.

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

[0023] When analyzing the consequences of the distribution network fault, the present invention not only takes into account the influence of the wiring form, but also considers the differences in the automation level in the actual distribution network, making it closer to the actual operation condition of the distribution network, the evaluation result is closer to the actual situation, and it can handle the distribution network system with different complex wiring forms, providing new technical inspiration for the planning and operation of the distribution network. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of the method flow described in the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some, rather than all, embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0027] The present invention provides a method for analyzing the consequences of distribution network faults considering the wiring form and automation level, including the following steps:

[0028] 1) Data reading and preprocessing:

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

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

[0031] 2) Fault handling and time generation:

[0032] Read the fault switch number and related fault modes from the fault input table, generate the power outage time of each switch and the transfer time (which is also related to the line structure, such as whether the transfer switch can be ordered by the dispatcher or can only be manually transferred on-site), and generate the maximum simulation time.

[0033] 3) Preprocessing stage at each moment:

[0034] Based on the power outage and transfer times generated above, the power outage load and the transfer switch numbers at this time section are generated by the power outage load calculation program.

[0035] 4) ATS transfer supply part:

[0036] Based on all the ATS switches in the search results (if any), determine whether the load power loss will cause the ATS to operate and perform transfer supply.

[0037] 5) Tie switch transfer supply part:

[0038] For the loads that cannot be transferred by the ATS, transfer supply through the tie switch (if transferable), and finally output the power outage loads under this section.

[0039] As Figure 1 shown, the method flow chart is elaborated as follows:

[0040] 1) Read the information tables of switches, feeders, and equipment, etc.:

[0041] Read the detailed information of switches, feeders, and equipment in the power grid from the database. This information includes the location, status, and affiliated feeder of the switches.

[0042] 2) Preprocess the data:

[0043] Clean and sort the read data, remove invalid data, correct incorrect data, and ensure the accuracy and integrity of the data.

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

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

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

[0047] Read the fault switch in the power grid and its corresponding fault information, which is used to judge the status of the fault switch.

[0048] 5) Screen the FTU switches:

[0049] Check whether the selected fault switch has an FTU (feeder terminal unit), and store the switch information with FTU for subsequent use.

[0050] 6) Screen out the tie switches and whether they are transferable:

[0051] Screen out all the tie switches in the power grid and judge whether these tie switches have the transfer supply ability, that is, whether they can transfer the loads in the power outage area to other feeders.

[0052] 7) Screen out the ATS and store it:

[0053] Screen all ATS devices in the power grid and store the information of these devices for subsequent use.

[0054] 8) Generate the power outage time max_T according to the fault mode table:

[0055] According to the fault information and the topology of the power grid, calculate the maximum power outage time max_T of each power outage area.

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

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

[0058] 10) Determine whether there is an ATS:

[0059] Check whether there is an ATS device in the power grid. If it exists, perform the next step; if it does not exist, skip the next step.

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

[0061] If there is an ATS device, simulate the power grid state after the ATS operates and calculate the power outage load after the operation.

[0062] 12) Determine whether transfer is possible:

[0063] According to the status and transfer capacity of the tie switch, determine whether the power outage load can be transferred to other feeders.

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

[0065] If transfer is possible, calculate the power outage load after transfer; if transfer is not possible, keep the current power outage load unchanged.

[0066] 14) Determine whether the maximum power outage time max_T is reached:

[0067] Check whether the current time t exceeds the maximum power outage time max_T. If it exceeds, perform the next step; if it does not exceed, increment t by 1 and return to step 9 to continue the calculation.

[0068] 15) Output the power outage load sets for each time section:

[0069] When the maximum power outage time max_T is reached, output the power outage load sets for each time section t, including information such as the power outage load and the transfer load.

[0070] According to the method flow mentioned above, the specific process of the method designed by the present invention is as follows:

[0071] 1. Reliability evaluation indicators:

[0072] The reliability evaluation indicators of the distribution system are the basis of reliability analysis. By calculating the reliability indicators of the system, the reliability level of the system is quantitatively evaluated. The reliability indicators of the distribution system can be divided into user reliability indicators and system reliability indicators according to the evaluation object. User reliability indicators are used to describe the power supply reliability of each load point in the distribution system, and system reliability indicators reflect the power supply capacity of the system.

[0073] 1.1 User reliability indicators:

[0074] According to the network structure and component parameters of the distribution network, the reliability levels of each load point in the system are evaluated: annual average number of failures (denoted as λ); annual average failure time (denoted as r); average duration of failure (denoted as U).

[0075] 1.2 System reliability indicators:

[0076] In order to reflect the overall reliability level of the distribution system, based on the reliability indicators of the load points, some performance indicators are defined to characterize the power outage statistics from the perspective of the system: System Average Interruption Frequency Index (SAIFI); System Average Interruption Duration Index (SAIDI); Customer Average Interruption Duration Index (CAIDI); Average Service Availability Index (ASAI); Expected Energy Not Supplied (EENS); Average Expected Energy Not Supplied (AENS).

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

[0078] 2.1 Influence of wiring form on the analysis of the consequences of distribution network faults

[0079] Medium and low voltage distribution network operates mainly with the loop network open, and it can usually be treated as a radial system. The Failure Mode and Effects Analysis (FMEA) is adopted as the reliability analysis method. By analyzing all possible component failures or fault accidents, the set of fault modes of the system is found, the influence on the load points is determined, and the reliability analysis of the load points is obtained. In the power industry, parameters such as Average Interruption Hours for Consumers (AIHC), Reliability of Service for Consumers (RS), and Average Interruption Frequency for Consumers (AITC) are often used as basic evaluation indicators. There are many evaluation indicators for the reliability of medium and low voltage distribution systems, and they need to be selected according to the actual situation. To reflect the importance and severity when the distribution network is out of service, RS is usually selected as the evaluation indicator, and the formula is

[0080] RS = (T v / T s ) × 100% (2.1)

[0081] Where: T vis the sum of the actual power supply times during the statistical period; T s is the total power supply time during the statistical period.

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

[0083] Then

[0084]

[0085] In the formula: N i is the number of users at load point i; t i is the average annual outage time of load point i.

[0086] In the reliability analysis and calculation of the distribution network, the main idea usually adopted is: using the failure rates and average repair times of four types of equipment, namely lines, ring network switches, circuit breakers, and busbars, calculate the number of power outage users caused by different equipment failures, and calculate the power outage frequency and power supply reliability based on the number of power outage users.

[0087] 1) The power outage duration of users when the busbar fails. There is only one section of the line busbar in different modes, and the influence of the number of line segments can be ignored. Its 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 busbar (times / unit × year); N is the total number of users of the line; r1 is the average repair time of the busbar (hours / time).

[0090] 2) The power outage duration of users when the line fails. If a line fails, different sectional failures need to be analyzed. When a line fails and the load carried by the line does not meet the condition of timely transfer, therefore, when this distribution line is single-radiated and divided into three sections, if the first section 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 section fails, the number of affected users will be 2 / 3N and 1 / 3N respectively, and the average outage time is the average repair time of the line. The summary of its calculation formula is as follows.

[0091] For single-radiation, it is

[0092]

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

[0094] For single connection

[0095]

[0096] In the case of other various wiring modes, different equipment after failure can be converted into single radiation and single connection, and then calculated separately.

[0097] 3) Duration of power outage for users when the circuit breaker fails. If it is set that each 10kV line corresponds to only one outlet circuit breaker. The failure rate of the circuit breaker under normal operating conditions is usually represented by the non-tripping rate. If the non-tripping rate of the circuit breaker is 2.11%, and the power outage of users caused by the failure of the circuit breaker is based on the power outage of the line, then its theoretical calculation formula is

[0098] ∑U i N i =λ2×R×N×r3×λ3(2.6)

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

[0100] 4) Duration of power outage for users when the ring main unit fails. If the ring main unit installed on the cable line is set as the sectionalizing equipment, and the load switch installed on the overhead line is set as the sectionalizing equipment. In theoretical calculation, it is assumed that the theoretical calculation formula is also applicable to the cable line, and the load switch is set as the research object. In the case of different network wiring modes, the duration of power outage for users when the load switch fails can be divided into two types: single radiation and single connection.

[0101] For single radiation:

[0102]

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

[0104] For single connection:

[0105]

[0106] In the case of other various wiring modes, different equipment after failure can be converted into single radiation and single connection, and then calculated separately.

[0107] If equipment such as load switch circuit breakers, cable lines, overhead lines, and busbars fail simultaneously, the corresponding formulas of AIH, AITC, and CRS can be used to calculate the numerical values of reliability indicators such as the average power outage time and the number of affected users.

[0108] 2.2. Impact of distribution automation on the analysis of the consequences of distribution network faults:

[0109] Distribution automation technology refers to a technical system that uses advanced communication, control, and information technologies to achieve the automated management and operation of the distribution network. By introducing intelligent devices, sensors, communication networks, and automation algorithms, this technology enables 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 in the distribution network.

[0110] 2.2.1. Classification of automation modes:

[0111] A distribution automation system is an integrated system for remotely and real-time monitoring, coordinating, and controlling distribution network component devices, and is the application of modern computer technology and communication technology in the monitoring and control of the distribution network. According to the different requirements for equipment transformation and communication systems in the construction of distribution automation, the distribution network construction modes are divided into three categories: fault location automation mode, local automation mode, and centralized automation mode. The distribution automation system can quickly locate and isolate the fault section after a fault occurs, reducing the time for fault finding and isolation. However, the speed and effect of fault handling and non-fault area power transfer are different under different distribution automation modes.

[0112] Since there are many distribution automation modes with different action principles and functional characteristics, it is rather cumbersome to conduct reliability assessment by considering various automation modes. According to the different degrees of influence of distribution automation modes on reliability, automation modes with approximately the same influence degree are merged into one category to reduce the workload of reliability assessment. For example, the recloser mode has the same distribution network operation parameters as the centralized semi-automation "three-remote and four-remote" mode, and the automation improvement effects are similar. Therefore, they are classified as one category during reliability assessment. For intelligent distribution, the fault can generally be isolated and power supply transfer completed within 20 - 30 s, and the reliability indicators only count power outage events lasting more than 3 minutes. Therefore, the theoretical reliability in this case is 100%, and it does not need to be considered during reliability assessment. The classification results are shown in the following table.

[0113] Table 1 Classification of distribution automation modes

[0114]

[0115] 2.2.2. Division of fault impact states:

[0116] When a feeder fails and the circuit breaker trips to protect, the nodes behind the tripped circuit breaker and the nodes of other feeders are not affected by the fault, while the nodes in front of the tripped circuit breaker are all affected nodes. After disconnecting the corresponding switchgear to isolate the fault point, the affected nodes may be restored to power through the power supply of this feeder, may also be restored to power through the transfer power supply of the tie line, or may be powered off due to inability to transfer power. Therefore, when not considering the influence of distribution automation, the fault influence states of the feeder load nodes can be divided into 4 types: fault unaffected state, fault repaired state, fault isolated state, and fault transferred state.

[0117] The influence of distribution automation on the reliability of the distribution network is mainly manifested in the implementation speed of fault location and isolation and power transfer. Therefore, both the fault location and isolation time and the fault transfer time are affected, and the specific influence degrees of the 4 levels of automation modes in Table 1 on the fault location and isolation time and the fault transfer time are different. If the distribution network contains automatic switchgear of levels A to D at the same time, due to the large difference in the breaking operation time of automatic switchgear at different levels, the automatic switchgear with a higher degree of automation often operates first during a fault. Therefore, the power supply restoration process after a fault will be carried out in stages.

[0118] When considering the influence of distribution automation, according to the different speeds of fault location and isolation and fault transfer, it can be divided into the following 10 fault influence states: fault unaffected state, fault repaired state, and A - D fault isolation states and A - D fault transfer states corresponding to the A - D levels of automation modes. Since the "fault unaffected state" does not need to be considered during the reliability assessment of the distribution network, only the following 9 fault influence states will be discussed.

[0119] 2.2.3, Distribution network reliability assessment:

[0120] According to the different influence states of the fault of node i on node j, define the fault enumeration node set The set of fault nodes that cause node j to be in the fault repaired state The set of fault nodes that cause node j to be in the A - D fault isolation states And the set of fault nodes that cause node j to be in the A - D fault transfer states The value of k represents the influence degree of the faults of different nodes on node j. For example, when k is 1, any node in the node set causes node j to be in the A fault isolation state, and the fault enumeration node set is formed by traversal. Define the equivalent reliability parameters of regional node j as the annual equivalent outage rate F j and the annual equivalent outage time D j , and the calculation formulas are

[0121]

[0122]

[0123] In the formula: λ(i) (k) is the equivalent failure rate of the electrical equipment set included in node i in a certain area of the node set ; T(i) (k) is the corresponding fault power outage time; t gm , t gal , t ga2 and t ga3 are respectively the isolation operation times of the automatic switches of the corresponding levels; t zm , t zal , t za2 and t za3 are respectively the transfer operation times of the automatic switches of the corresponding levels; λ i and t i can be calculated according to the electrical equipment set of area node i; λ m,i , λ f,i , λ l,i and λ t,i are respectively the failure rates of the feeder, fuse, distribution transformer branch line and transformer in the area node; p f is the reliable operation probability of the fuse; t m , t l , t f and t t are the corresponding equipment repair times; n M , n L , n F and n T are the corresponding numbers of equipment.

[0124] For each load point in the area, the reliability parameters of the load point can be obtained by only considering the influence of the reliable operation of the fuse at the load point on the basis of the equivalent reliability parameters of the area node. For the load point d in area node j, its annual failure outage rate F j (d) and annual failure outage time D j (d) 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] where: Δλ and Δt are the correction amounts of the load point fault outage rate and outage time respectively when considering the reliable operation of the fuse; λ 1,d 、λ t,d are the failure rates of the distribution transformer branch line and the transformer itself at the load point d respectively. The system reliability indexes can be obtained from the load point reliability parameters. The calculation formulas for the annual average number of power outages SAIFI of system users, the annual average power outage time SAIDI of system users, the power supply reliability rate RS of the system, and the annual average power supply shortage AENS of system users are respectively

[0128]

[0129] RS = (1 - SAIDI / 8760) × 100% (2.19)

[0130]

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

[0132] 2.3. Analysis method for the consequences of distribution network faults considering the wiring form and automation level:

[0133] 2.3.1. Improved dynamic minimal path method:

[0134] In the existing minimal path algorithms, the formation of paths is mainly divided into three types: the incidence matrix method, the depth-first search, or a combination of both. It is necessary to analyze the power supply of each user and the minimal path and power supply branch for the power supply of the power supply to the user in sequence. The time is formed by assigning the corresponding failure rate and fault recovery time according to the component type, obtaining the minimal path and power supply branch for user power supply by analyzing the component incidence matrix of the distribution network, and equivalenting the influence of the power supply branch on user reliability to the minimal power supply path. Through the series calculation of the minimal power supply path and the parallel calculation of different minimal power supply paths, the power supply reliability of the user is finally calculated.

[0135] The improved minimal path algorithm simplifies the search calculation process and time by analyzing the influence of the minimal path components and branch components from the power supply to the user on user reliability and making improvements in aspects such as topological data simplification, transfer principle, and formation of power supply paths.

[0136] (1) Topological data simplification

[0137] With the widespread application of the GIS (Geographic Information System) in the distribution network, real-time and accurate topological data of the distribution network can be obtained from the GIS system. The topological data of the distribution network GIS system consists of primary-side component data items of the distribution network and is grouped and stored according to the structure of city, district, bureau, substation, station, line, and component. The content of the data items includes the component number, component type, node number of the incoming line end of the component, node number of the outgoing line end of the component, etc.

[0138] Components that affect the reliability index of the distribution network include key components such as distribution transformers, circuit breakers, load switches, overhead lines, cables, and substation buses. In addition, in the topological data of the distribution network GIS system, there are also a large number of non-critical components such as poles and equipment fault detectors that do not affect the reliability calculation. To reduce the number of components in the component library to be retrieved and improve the retrieval efficiency, redundant data is processed on the premise of ensuring the connectivity of the system, thereby simplifying the topological data of the distribution network.

[0139] The main simplification idea is as follows: ① Identify non-critical components in the component list through component type to obtain the node numbers of the incoming line end and outgoing line end of the non-critical components; ② Assign the same new number to all the node numbers of the incoming line end and outgoing line end of the component (that is, regard the incoming line end and outgoing line end nodes of the component as the same new node); ③ Delete the component from the component list; ④ Finally, the remaining component types are only switch-type devices such as low-voltage buses, transformers, overhead lines, cables, circuit breakers, load switches, tie switches, and ATS (Automatic Transfer Switch).

[0140] (2) Transfer principle:

[0141] As the scale of the distribution network is getting larger and larger, numerous tie switches are connected between each feeder to improve the overall power supply reliability, thus forming an operation mode of closed-loop design and open-loop operation. However, when calculating the minimum path, in order to obtain all possible power supply paths of the load, the connection function of the tie switch needs to be considered. Therefore, according to the transfer method in the actual operation and maintenance of the distribution network, the transfer principle is determined as follows:

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

[0143] Considering the convenience and rapidity requirements for restoring power supply during transfer operation, for a non-faulty area, generally, power supply is not carried out through more than two tie switches. Especially in the case of on-site transfer, it will lead to a significant increase in the transfer time. Only when both tie switches are equipped with FTUs with remote control can the requirement of rapid transfer be met;

[0144] 2) Selection of transfer substation:

[0145] When selecting a feeder for power transfer, it is preferred to select a feeder within the same substation for power transfer. Only when all constraint conditions are not met, a feeder within an adjacent substation is selected to make full use of the redundant resources of the station and reduce the decline in power supply reliability caused by complex inter-station operations;

[0146] 3) Selection of transfer connection switches:

[0147] Similar to the transmission and distribution networks at each voltage level, the branch lines on each feeder are also classified (main, first-level, second-level, etc.). The capacity of the connection switches (if any) configured on each level of branch lines decreases corresponding to the level of the branch lines from large to small. Therefore, during power transfer, power can only be transferred from the connection points of the same level or higher-level branches to the area where power supply needs to be restored;

[0148] 4) Capacity constraint:

[0149] The adjacent feeder should first meet the maximum load of this feeder and leave a certain margin. Only when there is redundant capacity at this time does it have the ability to transfer power, and at the same time, the transferred power capacity provided cannot exceed the maximum transmission capacity allowed by the connection line;

[0150] 5) Quantity constraint of transfer lines:

[0151] If a non-faulty area cannot be completely transferred by one connection line, it can be transferred by at most two connection lines. If power supply to the entire area still cannot be restored at this time, load shedding is carried out according to the importance of the load under the principle of ensuring power supply to important users until it is less than the transfer capacity.

[0152] (3) Formation of power supply paths:

[0153] Similar to finding power supply paths using the conventional minimum path method, starting from the load point and ending at the power source point (substation), all possible power supply paths between each load point and each power source point are searched. Taking a certain load point as an example, the specific idea is as follows:

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

[0155] 2) Starting from the initial node, find all components connected to this node according to the number and store them in matrix A for backup;

[0156] 3) Enumerate the elements in matrix A in turn, search for the components connected to them, and compare with the elements in A. If the numbers are the same, they are discarded, and the remaining ones are stored in different columns of matrix B;

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

[0158] 4) Continuously repeat the above process, and store the numbers of all components passed from this load point to the power source point to form an initial power supply path table;

[0159] 5) Screen and process the initial power supply path table according to the transfer power supply principle in (2) to obtain a final path table that meets the transfer power supply principle for use as a backup in the subsequent fault analysis process.

[0160] 2.3.2. Fault consequence analysis process:

[0161] 1) Fault time calculation:

[0162] Combined with the analysis process in the previous subsection, analyze according to different wiring forms (whether there are tie switches) and automation differences (whether with FTU), and consider the handling process of maintenance personnel. The following 8 kinds of fault consequences and treatment results can be summarized and recorded as A 1 ~A 6 :

[0163] A 1 : After the fault, the power outage area cannot be transferred for power supply. The dispatcher remotely controls the closing of the switch for power supply. The power outage time is 0, and the transfer power supply time is 0;

[0164] A 2 : After the fault, the power outage area can be transferred for power supply and the transfer switch has an FTU. The dispatcher remotely transfers the power supply. After the on-site personnel complete the inspection, the original operation mode is restored. The power outage time is 0, and the transfer power supply time is 2;

[0165] A 3 : After the fault, and at this time the FTU fails and remote control cannot be performed. The power outage area cannot be transferred for power supply. The maintenance personnel perform on-site closing for power supply. The power outage time is 2, and the transfer power supply time is 0;

[0166] A 4 : After the fault, the power outage area can be transferred for power supply, but at this time the FTU fails and remote control cannot be performed. The maintenance personnel first perform on-site transfer for power supply and restoration, and after the inspection of the faulty FTU switch is completed, the original operation mode is restored. The power outage time is 2, and the transfer power supply time is 2;

[0167] A 5:After a fault, the power outage area cannot be transferred, but the telemetry data is incorrect, resulting in the inability to accurately locate the fault area. It is necessary for the operation and maintenance personnel to conduct on-site inspections. After determining the power outage scope and the misoperated switch, the dispatcher will remotely control the switch to close and restore power. The power outage time is 4, and the transfer time is 0;

[0168] A 6 :After a fault, the power outage area can be transferred, but the telemetry data is incorrect. After the operation and maintenance personnel conduct a preliminary on-site inspection, the dispatcher will remotely control the transfer to restore power to some areas. After inspecting the entire fault area without errors, the original operation mode will be restored. The power outage time is 4, and the transfer time is 2;

[0169] To facilitate the introduction of time in the improved minimum path algorithm, the time required for power outage and transfer is calculated on a 15-minute time scale. For example, in A 6 the power outage time is 4, and the transfer time is 2, that is, the power outage time is 4 fifteen-minute periods (one hour), and the transfer time to restore power is 2 fifteen-minute periods (half an hour).

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

[0171]

[0172] where is the power outage time in the i-th fault case, is the transfer time in the i-th fault case, and the maximum value of i is the total number of faulty switches.

[0173] Then the total maximum power outage calculation time T max is

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

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

[0176] Based on the maximum power outage calculation time T max calculated in the previous section, denoted as the maximum time scale n, 0 and 1 are used to represent whether the power supply path is connected (0 means not connected, that is, the load is lost at this time, otherwise it is connected). Denote the maximum load loss caused by the fault as N, and denote the number of power supply paths for each load as M.

[0177] First, classify according to each fault type obtained from the distribution automation system to obtain the power outage load at the initial time t = 0. At this time, the load loss is the largest and the power outage area is the largest. Based on the final path table obtained by the improved minimum path method, then consider the influence of the wiring form and automation, and calculate whether each load is powered off at each time scale one by one:

[0178]

[0179] Among them, GD (i,j,k) represents the connection status of the j-th power supply path of the i-th initial power outage load at the k-th moment

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

[0181] Then the load loss state of load i at moment k is that 0 represents load loss and 1 represents continuous power supply:

[0182]

[0183] Then the set of all load losses at the k-th moment is:

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

[0185] Among them, F (i) represents the i-th initial power outage load.

[0186] 3) Summary:

[0187] According to the above analysis process, it can be seen that during the process 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 correspondingly shortened. The specific time is related to the automation level. For example, for the ATS switch, the power outage time is 0, for on-site transfer it is 2, and for remote control it is 1. Therefore, the power outage range calculated at different moments changes and is closely related to the wiring form and automation level.

[0188] When analyzing the consequences of distribution network faults, the present invention not only takes into account the influence of the wiring form, but also considers the differences in automation levels in the actual distribution network, making it closer to the actual operating conditions of the distribution network, the evaluation results are closer to the actual situation, and it can handle distribution network systems with different complex wiring forms, providing new experience for guiding the planning and operation of the distribution network.

[0189] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or means for implementing the functions specified in one block or multiple blocks.

[0190] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0191] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A distribution network fault analysis method considering wiring form and automation level, characterized in that: The following steps are involved: Based on the fault mode table of the distribution network, the power outage and transfer time are obtained according to the fault switch number and related fault mode; Based on the power outage load, according to the power outage and transfer time, obtain the switch number of the power outage load and the transfer in the time section; The load is transferred through the ATS switch set in the switch number, and for the load that the ATS cannot transfer, it is transferred through the connecting switch to obtain the power outage load and analyze the consequences of the distribution network failure.

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

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

4. The distribution network fault analysis method considering wiring form and automation level according to claim 3 is characterized by: In the process of obtaining the switch number, the fault switch in the power grid and its corresponding fault information are read, and it is checked whether the selected fault switch has an FTU, and the switch information with the FTU is stored; at the same time, all the connecting switches in the power grid are screened out, and it is determined whether these connecting switches have the ability to transfer power remotely, and then the switch number composed of the FTU and the connecting switch is obtained.

5. The distribution network fault analysis method considering wiring form and automation level according to claim 4 is characterized in that: When obtaining the blackout load, the maximum blackout time max_T of each blackout area is calculated according to the fault information and the topological structure of the power grid, and for each time section t, the load of the blackout area and the load that can be transferred through the tie switch are calculated to obtain the blackout load.

6. The distribution network fault analysis method considering wiring form and automation level according to claim 5 is characterized by: When obtaining the power 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 power outage load after the action; determine whether the power outage load can be transferred to other feeders based on the state and transfer capacity of the tie switch; If power transfer is possible, calculate the power outage load after the transfer; If the power transfer is not possible, the current power outage load will remain unchanged.

7. The distribution network fault analysis method considering wiring form and automation level according to claim 6 is characterized by: When analyzing the consequences of a distribution network failure, check whether the current time t exceeds the maximum power outage time max_T. If so, output the power outage load set for each time section t; If not, t is increased by 1, and for each time section t, the load of the blackout area and the load that can be transferred through the tie switch are calculated to continue to obtain the blackout load.

8. A distribution network fault analysis system considering wiring form and automation level, characterized in that: include: A data acquisition module, used to obtain a fault mode table of the distribution network; The first analysis module is used to obtain the power outage and power transfer time according to the fault switch number and related fault mode based on the fault mode table of the distribution network; The second analysis module is used to obtain the switch number of the power outage load and the power transfer under the time section based on the power outage load and the power transfer time; The third analysis module transfers the load through the ATS switch set in the switch number, and for the load that the ATS cannot transfer, transfers it through the connecting switch, obtains the power outage load, and analyzes the consequences of the distribution network failure.

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