A comprehensive selection method for closing points in distribution network

Abstract

The present invention discloses a comprehensive selection method for closing points of distribution network, including: obtaining distribution network parameter information, and numbering all spare areas; according to the distribution network parameter information, calculating and judging whether the operating conditions of the distribution network after closing and switching power supply of each spare area meet the operating condition requirements; calculating and judging whether the voltage phase difference between the nodes of the main power supply area to be repaired and the nodes of each spare area that meets the operating condition requirements meets the conditions; calculating and judging whether each steady-state closing current after closing the loop meets the requirements; calculating various indicators, and combining the weights of each closing index calculated in advance to obtain the comprehensive index of each spare area; selecting the node of the spare area with the largest comprehensive index as the optimal closing point, and using the closing device selected by the spare area to perform actual closing and switching power supply operation on the load on the main power supply area to be repaired. The present invention can comprehensively, accurately and effectively select the optimal closing point, and improve the safety and economy of the closing operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution network closing loop, and more specifically, relates to a comprehensive selection method for distribution network closing loop points. Background Art

[0002] With the continuous development of the economy, the service concept of power supply companies has changed, and the user's electricity experience has received more and more attention. In order to improve the reliability of power supply, the proportion of distribution network closing and power supply operations has gradually increased. However, the traditional closing device (including only the closing switch) needs to meet certain closing conditions when performing closing and power supply operations (generally requiring the voltage phase angle difference on both sides of the closing ring to be between 0 and 10°), and there is a closing ring impact current, which has a high operating risk. In order to improve the safety and reliability of the closing operation, the seamless closing device has been further studied. The Chinese patent application number: CN202110372138.4 proposes a new type of seamless closing and power supply device for low-voltage distribution network, which can eliminate the impact current in the closing and power supply process, and realize the power supply operation with a voltage phase angle difference of 0 to 30° on both sides of the closing ring without power outage, further improving the reliability of power supply.

[0003] Before performing the distribution network closing operation, the closing point selection must be performed first. The selection of the closing point is an important issue in the closing and power supply operation of the distribution network. When different closing points are selected, different closing voltage differences will produce different closing currents, and the line flow distribution after closing is also different, which makes the corresponding closing and power supply operation have different economy and safety. Currently, the closing points are mostly selected based on the principle of proximity. If the closing point is not selected properly, the current flowing through the closing line is too large, which may cause safety problems such as line protection switch tripping and power supply equipment overload, and even cause large economic losses. Choosing a good closing point can improve the safety and economy of the closing and power supply operation.

[0004] Therefore, it is necessary to study a comprehensive method for selecting closing points that comprehensively considers traditional and potential closing scenarios. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide a comprehensive selection method for the closing point of the distribution network, which takes into account the closing scenario where both traditional closing devices and seamless closing devices are used, and can comprehensively, accurately and effectively select the optimal closing point to improve the safety and economy of the closing operation.

[0006] To achieve the above object, the present invention provides a method for comprehensive selection of closing points in a distribution network, which comprises the following steps:

[0007] (1) Obtain distribution network parameter information and number all standby substations;

[0008] (2) Calculating the operating conditions of the distribution network after the k-circuit power supply of each backup substation according to the distribution network parameter information; if the operating conditions meet the operating conditions requirements, executing step (3); if not, ending the verification of the backup substation;

[0009] (3) According to the distribution network parameter information, the voltage phase difference between the node of the main power supply area to be repaired and the node of each standby area k that meets the operating condition requirements is calculated. If the voltage phase difference is less than 10°, it is preliminarily considered that a first closing device can be selected between the node of the main power supply area to be repaired and the node of the standby area and step (4) is performed. The first closing device only includes a closing switch. If the voltage phase difference is greater than or equal to 10° and less than or equal to 30°, it is considered that a second closing device can be selected between the node of the main power supply area to be repaired and the node of the standby area and step (5) is performed. The second closing device is used to realize the closing power supply operation with the voltage phase difference between 0 and 30°. If the voltage phase difference is greater than 30°, the verification of the standby area is terminated.

[0010] (4) Based on the equivalent method and superposition principle of Thevenin theory, the steady-state closed-loop currents on both sides of the first closed-loop device on the closed-loop line formed by connecting each standby substation k with the main power supply substation to be repaired, as well as the steady-state closed-loop currents flowing through the feeder of the standby substation and the feeder of the main power supply substation to be repaired connected thereto are calculated. If the steady-state closed-loop currents meet the requirements, the first closed-loop device is selected between the node of the main power supply substation to be repaired and the node of the standby substation; if the steady-state closed-loop currents do not meet the requirements, the second closed-loop device is selected between the node of the main power supply substation to be repaired and the node of the standby substation;

[0011] (5) According to the distribution network operating conditions after the ring closing of each standby substation k to be verified and the type of ring closing device used, the static voltage stability margin index, wire stripping safety index, ring closing current safety index and economic index of each standby substation k are calculated respectively, and the weights of the safety and economic indicators of each standby substation k calculated in advance by the hierarchical analysis method are combined to calculate the comprehensive index of each standby substation k;

[0012] (6) The node of the standby substation with the largest comprehensive index is selected as the optimal closing point, and the closing device selected by the standby substation is used to perform actual closing and power supply operations on the load on the main power supply substation to be maintained.

[0013] The comprehensive selection method for the closing point of the distribution network provided by the present invention comprehensively considers various states of the power system, operating conditions, voltage phase difference and steady-state circulating current, takes into account the economic indicators and safety indicators of the closing point, and can effectively improve the reliability of the closing point selection; at the same time, it takes into account the scenarios of seamless closing and power transfer devices and traditional closing and power transfer devices, and has high practical value.

[0014] In one of the embodiments, in step (1), the distribution network parameter information includes distribution network structure, distribution network operating condition parameters, transformer parameters and load parameters.

[0015] In one embodiment, in step (2), the operating condition requirements include that the line flow after the ring-closing power supply meets the current carrying capacity requirement and the load carried by the standby substation meets the main transformer capacity requirement.

[0016] In one embodiment, in step (4), if each steady-state closed-loop current meets the requirements, the following equation is satisfied:

[0017]

[0018] In the formula, Indicates the phase voltage of each standby area k; Indicates the phase voltage of the main power supply area to be repaired; It represents the equivalent impedance of the closed-loop line including the closed-loop device in each standby substation k; It represents the equivalent impedance of each standby substation k minus the external network impedance outside the closed loop line; It indicates the steady-state closed-loop current flowing through the first closed-loop device on both sides of the closed-loop line formed by connecting each standby substation k with the main power supply substation to be repaired after the loop is closed; Indicates the steady-state closing current flowing through the feeder k of each standby substation before closing; Indicates the steady-state closing current flowing through the feeder of the main power supply station area to be repaired before closing the loop; Indicates the current flowing through the feeder of the main power supply station area to be repaired after the loop is closed; It indicates the current flowing through the feeder k of each standby substation after the loop is closed; , and It corresponds to the current carrying capacity on the k feeder of each standby substation, the current carrying capacity on the feeder of the main power supply substation to be repaired, and the current carrying capacity on the closed-loop line.

[0019] In one embodiment, in step (5), the static voltage stability margin index of each standby area k node is for:

[0020]

[0021] In the formula, It represents the active load of the k-node of each standby substation after the ring is closed; Represents the load at the voltage collapse point of node k in each backup substation.

[0022] In one embodiment, in step (5), the wire stripping safety index of each standby area k node is for:

[0023] When the ring-closing power supply site is connected to the backup switch at the head end of the low-voltage cabinet between stations or the busbar at the head end of the low-voltage cabinet between stations, the wire stripping safety index of the node in the backup station area 1; when the power supply site is connected to the nearest point cable between substations, the wire stripping safety index of the node in the standby substation is It is determined based on the site of the closed-loop power supply.

[0024] In one embodiment, in step (5), the loop current safety index of the k-node of each standby substation is calculated according to the type of loop closing device selected by the standby substation;

[0025] When the backup area k adopts the second closing device, the closing safety index of the backup area is is 1;

[0026] When the standby area k adopts the first closing device, the closing safety index of the standby area is for:

[0027]

[0028]

[0029]

[0030]

[0031] In the formula, Indicates the impact current margin index of the first loop closing device selected in each standby area k; Indicates the steady-state current margin index of the first loop closing device selected in each standby area k; , The corresponding weights represent the impact current margin index and the steady-state current margin index; Indicates the over-current quick-break protection triggering current on the closed-loop circuit formed by connecting each standby substation k with the main maintenance power supply substation; It represents the maximum effective value of the impact current on the closed-loop line formed by connecting each backup substation k with the main maintenance power supply substation.

[0032] In one embodiment, in step (5), the economic performance index of each standby area k is for;

[0033] When the standby substation k adopts the first closing device, the economic index of the standby substation is ; For the ring-circuit power supply site, the low-voltage cabinet head end bus connection between substations, the economic index of the standby substation is ; For the power supply site of the ring-closing power supply, the economic index of the standby substation is ;

[0034] When the standby substation k adopts the second closing device, the economic index of the standby substation is ; For the ring-closing power supply site, the first-end busbar connection of the low-voltage cabinet between substations, the economic indicators of the standby substation area ; For the power supply site of the ring-closing power supply, the economic index of the standby substation is ;

[0035] in, and Indicates the single operation cost of the first closing device and the backup switch; Indicates the cost per operation of the second closing device and accessories; Indicates the unit price of the cable per unit distance; It represents the cost of laying cables per unit distance by manpower; Indicates the length of the cable that can be laid between each standby area k and the main power supply area to be repaired; e represents the labor cost of wire stripping; represents the manpower cost of a single operation; Q represents the standard value of economy.

[0036] In one embodiment,

[0037] The comprehensive index of each standby area k for:

[0038]

[0039] In the formula, the static voltage stability margin index of each backup area k is , Stripping safety indicators , loop current safety index and economic indicators The maximum and minimum limits must be met, that is, , if not met, the comprehensive index of the standby area is 0;

[0040] in, is the weight of the static voltage stability margin index, is the weight of the wire stripping safety index, is the weight of the closed-loop current, is the weight of the closed loop safety, is the weight of the economic indicator. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of a comprehensive selection method of a distribution network closing point provided by an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of different 10 kV line partitions of the same 110 kV substation provided by a specific embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the circuit principle of a certain closed-loop circuit in a specific embodiment of the present invention;

[0044] Figure 4 yes Figure 3 The simplified equivalent circuit diagram of the closed loop circuit;

[0045] Figure 5 It is a flow chart of a method for comprehensive selection of closing points in a distribution network provided by a specific embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] It should be noted that the closing loop scenario refers to when the main supply area needs to be shut down (requires maintenance), the main supply area is connected to the backup area through cables and closing loop devices to form a closing loop line, and the load on the main supply area is transferred to the backup area by operating the closing loop device, completing the closing loop power supply operation.

[0048] In order to solve the problem that traditional closing points are mostly selected based on the principle of proximity, resulting in poor safety and economy, the present invention takes into account the closing scenarios in which traditional closing devices and seamless closing devices are used together, and aims at the important issue of closing point selection to provide an accurate, comprehensive and effective comprehensive selection method for distribution network closing points, which provides a basis for power dispatchers to carry out distribution network closing operations and effectively improves the safety and economy of closing operations.

[0049] Figure 1 FIG. 1 is a flow chart of a method for comprehensive selection of closing points in a distribution network provided by an embodiment of the present invention. Figure 1 As shown, the comprehensive selection method of the distribution network closing point includes:

[0050] S10, Get information

[0051] Specifically, the distribution network parameter information is obtained, which may include information such as the distribution network structure, distribution network operating condition parameters, transformer parameters, and load parameters. At the same time, all spare areas are numbered to facilitate the subsequent selection of the optimal spare area. The node of the optimal spare area corresponds to the optimal closing point. For example, assuming that the main power supply area can be numbered as area 1, each spare area k can be numbered as 2, ..., G. Of course, other numbering methods can also be used, and this embodiment is not limited.

[0052] For all the spare stations (2, ..., G), steps S20 to S60 are performed:

[0053] S20, calculate and determine whether the distribution network meets the requirements after the ring-closing power supply

[0054] Specifically, according to the information obtained in step S10, calculate whether the operating conditions of the distribution network after the ring-closing and power supply of each standby substation k meet the requirements: the line flow after the ring-closing and power supply must meet the current carrying capacity requirements, and the load size carried by the standby substation must meet the main transformer capacity requirements. If the operating conditions meet the operating conditions, go to step S30; if they do not meet the operating conditions, it is determined that the standby substation is not allowed to close the ring, and the verification of the standby substation ends.

[0055] S30, calculate and determine whether the phase difference meets the conditions

[0056] Specifically, according to the information obtained in S10, the voltage phase differences between the nodes of the main power supply area to be repaired and the nodes of the backup area that meets the working conditions are calculated. If the voltage phase difference is less than 10°, it is preliminarily considered that the first closing device can be selected between the nodes of the main power supply area to be repaired and the nodes of the backup area, and then the process goes to step S40 for further judgment, wherein the first closing device only includes a closing switch, that is, a traditional closing device, which can realize a closing power supply operation with a voltage phase difference between 0 and 10°.

[0057] If the voltage phase difference is greater than or equal to 10° and less than or equal to 30°, it is considered that the second closing device can be selected between the node of the main power supply area to be repaired and the node of the backup area, and then go to step S50. The second closing device is a seamless closing device known in the art, which is used to realize the closing and power supply operation with a voltage phase difference between 0 and 30°. If the voltage phase difference is greater than 30°, the verification of the backup area is ended.

[0058] S40, calculate and determine whether the steady-state current meets the conditions

[0059] Specifically, according to the information obtained in S10, based on the equivalence method and superposition principle of the Thevenin theory, the steady-state closing currents on both sides of the first closing device on the closing line formed by connecting each backup substation k with the main power supply substation to be repaired are calculated after the closing, as well as the steady-state closing currents flowing through the feeder of the backup substation and the feeder of the main power supply substation to be repaired connected thereto. If each steady-state closing current meets the requirements, a traditional closing device is selected between the node of the main power supply substation to be repaired and the node of the backup substation; if each steady-state closing current does not meet the requirements, a seamless closing device is selected between the node of the main power supply substation to be repaired and the node of the backup substation.

[0060] S50, calculate various indicators and obtain comprehensive indicators of each backup area

[0061] Specifically, according to the distribution network operating conditions after the ring closing of each standby substation k to be verified and the type of ring closing device used, the static voltage stability margin index, wire stripping safety index, ring closing current safety index and economic index of each standby substation k are calculated respectively. Then, combined with the weights of the safety and economic indicators of each standby substation k calculated in advance by the hierarchical analysis method, the comprehensive index of each standby substation k is calculated.

[0062] Among them, the static voltage stability margin index, wire stripping safety index, loop current safety index and economic index must all meet the minimum and maximum limits. If not, the comprehensive index of the standby substation to be verified is set to 0.

[0063] Among them, the static voltage stability margin index of the standby substation to be verified is defined as: starting from the steady-state state after the system is closed, by increasing the load power carried by the closing point to be verified (the node of the standby substation k to be verified) gradually approaching the voltage collapse point, the distance from the closing steady-state state of the distribution network system to the voltage collapse point.

[0064] Economic indicators and safety indicators use different calculation formulas under different on-site connection schemes for closing and power supply. There are three types of on-site connection schemes for closing and power supply: Type 1. The low-voltage cabinet backup switches between substations are connected. The economic aspect needs to consider the closing device cost, cable cost and labor operation cost. The safety aspect needs to consider the closing current safety index and static voltage stability margin; Type 2. The low-voltage cabinet busbar connection between substations. The economic aspect needs to consider the closing device cost, cable cost, backup switch cost and labor operation cost. The safety aspect needs to consider the closing current safety index and static voltage stability margin; Type 3. The cable connection between substations is at the nearest point. In this case, the wire needs to be stripped and then connected. The economic aspect needs to consider the closing device cost, cable cost, backup switch cost, labor operation cost and additional stripping cost. The safety aspect needs to consider the closing current safety index, stripping safety index and static voltage stability margin.

[0065] S60, select the optimal closing point

[0066] A selection is made among the backup substations k, and the node of the backup substation with the largest comprehensive index is taken as the optimal closing point. The closing device selected by the backup substation is used to close the loop and transfer power to the load on the main power supply substation to be maintained.

[0067] The comprehensive selection method for the closing point of the distribution network provided in this embodiment comprehensively considers various states of the power system, operating conditions, voltage phase difference and steady-state circulating current, takes into account the economic indicators and safety indicators of the closing point, and can effectively improve the reliability of the closing point selection; at the same time, it takes into account the scenarios of seamless closing and power transfer devices and traditional closing and power transfer devices, and has high practical value.

[0068] In order to more clearly illustrate the present invention, the following is described in conjunction with specific embodiments:

[0069] Taking the different 10 kV bus connections under different 10 kV line partitions of the same 110 kV substation as an example, the distribution network closing situation is described. The schematic diagram of different 10 kV line partitions under the same 110 kV substation is as follows Figure 2 As shown in the figure, there are G feeder lines in total. Assume that area 1 is the main area to be repaired, and one of the loop lines k1 (k=2,…,G) is as follows Figure 3 shown.

[0070] exist Figure 3 In the process, substation 1 is waiting for maintenance, bus k communicates with bus 1, and the load 1 carried by substation 1 is transferred to substation k. Figure 3 In the figure, the 0.4 kV feeder closing switch is a simple expression of the closing device. Figure 3 middle, , They are the phase voltages of low voltage bus k and low voltage bus 1 respectively; , is the initial current on feeder k and feeder 1; is the closed-loop steady-state current. The equivalent circuit of the closed-loop circuit obtained by the Thevenin equivalent method is as follows: Figure 4 As shown, the closing point k and the closing point 1 correspond to the low-voltage bus k and the low-voltage bus 1. is the equivalent impedance of the closed-loop line including the closed-loop device, To subtract the equivalent impedance of the external network outside the closed loop line.

[0071] like Figure 5 As shown, the present invention relates to a comprehensive selection method for distribution network closing points in a closing scenario in which a traditional closing device and a seamless closing device are used together. The method comprises the following steps:

[0072] 1. Obtaining information

[0073] Obtain information such as distribution network structure, equipment status, system operating conditions, transformer and other equipment parameters, load data, etc. in the automation system, and determine the numbers of all closing points to be verified.

[0074] For all the candidate closing points k (k=2,…,G), perform steps (ii) to (vi):

[0075] (II) Calculate and determine whether the distribution network meets the requirements after the ring-closing power supply

[0076] After the ring-closing power supply is switched, the distribution network operation conditions must meet the following requirements:

[0077] ① After the ring-closing power supply is switched, the line flow must meet the current carrying capacity requirements;

[0078] (1)

[0079] In the formula, is a set of distribution network nodes; represents the current on line ij; It indicates the current carrying capacity of line ij, which can be determined according to the specifications of the cable used in line ij.

[0080] ②The load size of the standby substation must meet the capacity requirements of the main transformer.

[0081] (2)

[0082] In the formula, is the load carried by the backstage area k after power transfer, Represents the capacity of the main transformer k.

[0083] If the operating conditions meet the above two requirements, go to step (iii); if not, it is determined that the closing point k is not allowed to close the loop, and the verification of the closing point k ends.

[0084] (III) Calculate and determine whether the phase difference meets the conditions

[0085] Calculate the phase angle difference of the voltage on both sides of the closing point k : .like , then the closing condition is not met, the closing point k is not allowed to close the loop, and the verification ends; if , it is necessary to go to step (IV) to further determine the device to be used; if , determine that a seamless ring closing device is required to close the ring at this point, and go to step (V).

[0086] (IV) Calculate and determine whether the steady-state current meets the conditions

[0087] Based on the equivalent method and superposition principle of Thevenin theory, the steady-state currents of the two feeders after the loop is composed of two parts: one part is the initial current of the two feeders before the loop is closed. , The other part is the steady-state circulating current caused by the voltage amplitude and phase angle difference of the closing points on both sides of the closing switch. .

[0088] according to Figure 4 The Thevenin equivalent circuit shown calculates the steady-state circulating current :

[0089] (3)

[0090] Then the steady-state current flowing through feeder k after the loop is closed is As follows:

[0091] (4)

[0092] Then the steady-state current flowing through feeder 1 after the loop is closed is As follows:

[0093] (5)

[0094] If each steady-state current meets the conditions, the following equation must be satisfied:

[0095] (6)

[0096] In the formula, , and They are the current carrying capacity of feeder k, feeder 1 and the closed-loop line respectively, which can be determined according to the specifications of the cables used in the closed-loop line.

[0097] If the steady-state currents meet the conditions, it is determined that a conventional loop closing device is used, and the process goes to step (V); if the steady-state currents do not meet the conditions, it is determined that a seamless loop closing device is required, and the process goes to step (V).

[0098] (V) Calculate various indicators and obtain the comprehensive indicator value of the closing point

[0099] The weights of each closed loop safety and economic index are calculated in advance using the hierarchical analysis method. Among the closed loop safety sub-indicators, the corresponding weights of the static voltage stability margin index, the wire stripping safety index, and the closed loop current safety index are , , The corresponding weights of the closing loop safety and economic indicators are , .

[0100] According to the operating conditions of the distribution network and the types of devices used, the static voltage stability margin index, wire stripping safety index, loop current safety index and economic index are calculated respectively. According to the obtained index weight system, the comprehensive index value of the loop point to be verified is obtained.

[0101] 1) Security

[0102] ①Static voltage stability margin index

[0103] The static voltage stability margin index is shown as follows:

[0104] (7)

[0105] In the formula, is the static voltage stability margin value of the loop closing point k; is the active load at the closing point k after the closing of the loop; The active load at the voltage collapse point at the closing point k is determined according to the continuous power flow method, that is, the critical point of the power system under load changes is tracked using a continuous method.

[0106] ②Wire stripping safety index

[0107] Stripping safety is expressed as , that is, the probability of no accident when stripping the wire. When the on-site connection scheme is type 1 or 2, stripping the wire is not required. Therefore, 1; when the field connection scheme is type 3, wire stripping is required. Not 1, its value is determined according to the on-site conditions.

[0108] ③ Safety index of closed loop current

[0109] The closed-loop current safety index is calculated separately according to different device types.

[0110] a. Use traditional ring closing device

[0111] According to the steady-state closed-loop current on both sides of the first closed-loop device on the closed-loop line formed by connecting each standby substation k with the main power supply substation to be repaired after the closed-loop , calculate the maximum effective value of the impact current :

[0112] (8)

[0113] The impact current margin index of the traditional loop closing device is:

[0114] (9)

[0115] In the formula, The overcurrent quick-break protection trigger current on the closed-loop line formed by connecting each standby substation k with the main maintenance power supply substation can be determined according to the relay protection setting value in the project.

[0116] Take a larger feeder steady-state current margin and calculate the steady-state current margin index of the traditional loop closing device:

[0117] (10)

[0118] The closing safety of traditional closing devices It can be expressed as the comprehensive value of the impact current margin index and the steady-state current margin index:

[0119] (11)

[0120] In the formula, , They are the weights corresponding to the impact current margin index and the steady-state current margin index respectively.

[0121] b.Use seamless ring device

[0122] When a seamless closing device is used at the closing power supply site, there is no impact current in the closing line. The seamless closing device can ensure the closing safety, and its closing safety is 1, that is:

[0123] (12)

[0124] 2) Economic indicators

[0125] For different on-site connection schemes for closed-loop power supply, the economic indicators need to be considered separately.

[0126] a. Use traditional ring closing device

[0127] For the on-site connection scheme 1 for the closed-loop power supply, its economic indicators are:

[0128] (13)

[0129] For the on-site connection scheme 2 for the closed-loop power supply, its economic indicators are:

[0130] (14)

[0131] For the on-site connection scheme 3 for the closed-loop power supply, its economic indicators are:

[0132] (15)

[0133] In the formula, and are the single operation costs of the traditional loop closing device and the backup switch respectively; is the unit price of the cable per unit distance; Cost of laying cables per unit distance in manpower; is the length of the cable that can be laid between the closing point k and the closing point 1; e is the labor cost of stripping the wire; is the manpower cost for a single operation; Q is the standard value of economy.

[0134] b.Use seamless ring device

[0135] For the on-site connection scheme 1 for the closed-loop power supply, its economic indicators are:

[0136] (16)

[0137] For area type 2, the economic indicators are:

[0138] (17)

[0139] For area type 3, the economic indicators are:

[0140] (18)

[0141] In the formula, Cost per operation for seamless ring fittings and accessories.

[0142] Each static voltage stability margin index, wire stripping safety index, loop current safety index and economic index must meet the maximum and minimum value limits. If not, the comprehensive index value of the loop point is set to 0:

[0143] (19)

[0144] In summary, according to the static voltage stability margin index, wire stripping safety index, loop closing current safety index and economic index and their corresponding weights, the comprehensive index value of the loop closing point is:

[0145] (20)

[0146] in, is the weight of the static voltage stability margin index, is the weight of the wire stripping safety index, is the weight of the closed-loop current, is the weight of the closed loop safety, is the weight of the economic indicator.

[0147] (VI) Select the optimal closing point

[0148] Select from all the candidate closing points and take the closing point with the largest comprehensive index value as the optimal closing point:

[0149] (twenty one)

[0150] It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included.

Claims

1. A comprehensive selection method for closing points in a distribution network, characterized in that: The steps include: (1) Obtain distribution network parameter information and number all standby substations; (2) Calculating the operating conditions of the distribution network after the k-circuit power supply of each backup substation according to the distribution network parameter information; if the operating conditions meet the operating conditions requirements, executing step (3); if not, ending the verification of the backup substation; (3) According to the distribution network parameter information, the voltage phase differences between the nodes of the main power supply area to be repaired and the nodes of each standby area k that meets the operating condition requirements are calculated. If the voltage phase difference is less than 10°, it is preliminarily considered that a first closing device can be selected between the nodes of the main power supply area to be repaired and the nodes of the standby area and step (4) is performed. The first closing device only includes a closing switch. If the voltage phase difference is greater than or equal to 10° and less than or equal to 30°, it is considered that a second closing device can be selected between the nodes of the main power supply area to be repaired and the nodes of the standby area and step (5) is performed. The second closing device is used to realize the closing power supply operation with a voltage phase difference between 0 and 30°. If the voltage phase difference is greater than 30°, the verification of the standby area is terminated; (4) Based on the equivalent method and superposition principle of Thevenin theory, the steady-state closed-loop currents on both sides of the first closed-loop device on the closed-loop line formed by connecting each standby substation k with the main power supply substation to be repaired, as well as the steady-state closed-loop currents flowing through the feeder of the standby substation and the feeder of the main power supply substation to be repaired connected thereto are calculated. If the steady-state closed-loop currents meet the requirements, the first closed-loop device is selected between the node of the main power supply substation to be repaired and the node of the standby substation; If each steady-state closed-loop current does not meet the requirements, a second closed-loop device is selected between the node of the main power supply area to be repaired and the node of the standby area; (5) According to the distribution network operating conditions after the ring closing of each standby substation k to be verified and the type of ring closing device used, the static voltage stability margin index, wire stripping safety index, ring closing current safety index and economic index of each standby substation k are calculated respectively, and the weights of the safety and economic indicators of each standby substation k calculated in advance by the hierarchical analysis method are combined to calculate the comprehensive index of each standby substation k; (6) Select the node of the standby substation with the largest comprehensive index as the optimal closing point, and use the closing device selected by the standby substation to perform actual closing and power supply operations on the load on the main power supply substation to be maintained; The comprehensive index of each standby area k for: In the formula, the static voltage stability margin index of each backup area k is , Stripping safety indicators , loop current safety index and economic indicators The maximum and minimum limits must be met, that is, , if not met, the comprehensive index of the standby area is 0; in, is the weight of the static voltage stability margin index, is the weight of the wire stripping safety index, is the weight of the closed-loop current, is the weight of the closed loop safety, is the weight of the economic indicator.

2. The method for comprehensive selection of closing points of distribution network according to claim 1, characterized in that: In step (1), the distribution network parameter information includes distribution network structure, distribution network operating condition parameters, transformer parameters and load parameters.

3. The method for comprehensive selection of closing points of distribution network according to claim 1, characterized in that: In step (2), the operating condition requirements include that the line flow after the ring-closing power supply meets the current carrying capacity requirement and the load carried by the standby substation meets the main transformer capacity requirement.

4. The method for comprehensive selection of closing points of distribution network according to claim 1, characterized in that: In step (4), if each steady-state closed-loop current meets the requirements, the following equation is satisfied: In the formula, Indicates the phase voltage of each standby area k; Indicates the phase voltage of the main power supply area to be repaired; It represents the equivalent impedance of the closed-loop line including the closed-loop device in each standby substation k; It represents the equivalent impedance of each standby substation k minus the external network impedance outside the closed loop line; It indicates the steady-state closed-loop current flowing through the first closed-loop device on both sides of the closed-loop line formed by connecting each standby substation k with the main power supply substation to be repaired after the loop is closed; Indicates the steady-state closing current flowing through the feeder k of each standby substation before closing; Indicates the steady-state closing current flowing through the feeder of the main power supply station area to be repaired before closing the loop; Indicates the current flowing through the feeder of the main power supply station area to be repaired after the loop is closed; It indicates the current flowing through the feeder k of each standby substation after the loop is closed; , and It corresponds to the current carrying capacity on the k feeder of each standby substation, the current carrying capacity on the feeder of the main power supply substation to be repaired, and the current carrying capacity on the closed-loop line.

5. The method for comprehensive selection of closing points of distribution network according to claim 4, characterized in that: In step (5), the static voltage stability margin index of each standby area k node is for: In the formula, It represents the active load of the k-node of each standby substation after the ring is closed; Represents the active load at the voltage collapse point of node k in each backup substation.

6. The method for comprehensive selection of closing points of distribution network according to claim 5, characterized in that: In step (5), the stripping safety index of each standby area k node is for: When the ring-closing power supply site is connected to the backup switch at the head end of the low-voltage cabinet between stations or the busbar at the head end of the low-voltage cabinet between stations, the wire stripping safety index of the node in the backup station area 1; when the power supply site is connected to the nearest point cable between substations, the wire stripping safety index of the node in the standby substation is It is determined based on the site of the closed-loop power supply.

7. The method for comprehensive selection of closing points of distribution network according to claim 6, characterized in that: In step (5), the loop current safety index of the k-node of each standby substation is calculated according to the type of loop closing device selected by the standby substation; When the backup area k adopts the second closing device, the closing safety index of the backup area is is 1; When the backup area k adopts the first closing device, the closing safety index of the backup area is for: In the formula, Indicates the impact current margin index of the first loop closing device selected in each standby area k; Indicates the steady-state current margin index of the first loop closing device selected in each standby area k; , The corresponding weights represent the impact current margin index and the steady-state current margin index; Indicates the over-current quick-break protection triggering current on the closed-loop circuit formed by connecting each standby substation k with the main maintenance power supply substation; It represents the maximum effective value of the impact current on the closed-loop line formed by connecting each backup substation k with the main maintenance power supply substation.

8. The method for comprehensive selection of closing points of distribution network according to claim 7, characterized in that: In step (5), the economic index of each standby area k is for; When the standby substation k adopts the first closing device, the economic index of the standby substation is ; For the ring-circuit power supply site, the low-voltage cabinet head end bus connection between substations, the economic index of the standby substation is ; For the power supply site of the ring-closing power supply, the economic index of the standby substation is ; When the standby substation k adopts the second closing device, the economic index of the standby substation is ; For the ring-closing power supply site, the first-end busbar connection of the low-voltage cabinet between substations, the economic indicators of the standby substation area ; For the power supply site of the ring-closing power supply, the economic indicators of the standby substation area are as follows: ; in, and Indicates the single operation cost of the first closing device and the backup switch; Indicates the cost per operation of the second closing device and accessories; Indicates the unit price of the cable per unit distance; It represents the cost of laying cables per unit distance by manpower; Indicates the length of the cable that can be laid between each standby area k and the main power supply area to be repaired; e represents the labor cost of wire stripping; represents the manpower cost of a single operation; Q represents the standard value of economy.

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