A dynamic current-carrying capacity evaluation method and device

Abstract

The application discloses a dynamic load carrying capacity evaluation method, which comprises the following steps: calculating a first power demand capacity of a power transmission section, a first overload capacity of a main transformer, and a second overload capacity of each power transmission line in the power transmission section; determining whether to perform power flow distribution according to a comparison result of the first power demand capacity and the first overload capacity; if not, directly calculating a dynamic load carrying capacity; if yes, performing the power flow distribution, and then determining the dynamic load carrying capacity according to a comparison result of the first power demand capacity, the first overload capacity and the second overload capacity. The dynamic load carrying capacity is obtained by comprehensively considering the power transmission line section and the main transformer, calculating the real overload capacity of the power transmission line and the transformer, and simultaneously considering the power flow distribution of the line in the power transmission section, so that the transmission capacity of the transformer and the line in the power transmission section is given, and the power grid equipment capacity expansion operation can be guided.

Description

Technical Field

[0001] This application relates to the field of dynamic current-carrying capacity assessment technology for power grid equipment, a method for dynamic current-carrying capacity assessment, and a device for dynamic current-carrying capacity assessment. Background Technology

[0002] As electricity demand continues to rise, some transformers and transmission lines are operating under heavy load to meet the demand, highlighting the bottleneck in transmission capacity. Currently, with the strengthening of the main power grid, transient stability is no longer the primary factor restricting transmission capacity. Instead, the main concern is that under normal operating conditions, the power flow of transmission lines may exceed the static current carrying capacity limits specified in regulations. To ensure that equipment does not trip due to overload, its transmission power must be strictly controlled under normal operating conditions.

[0003] The transmission capacity of a power transmission section depends on the load-carrying capacity of the lines and transformers, as well as the power flow distribution of the lines. Due to the lack of effective methods for assessing the dynamic current-carrying capacity of power grid equipment, it is difficult to determine the true overload capacity of overhead lines and main transformers while ensuring their thermal stability and safety. Therefore, the transmission capacity limit can only be set based on the conservative static load-carrying capacity. In some areas, the transmission capacity of main transformers and overhead transmission lines is limited by the static current-carrying capacity, which seriously restricts the capacity transmission within the system. Furthermore, building new line corridors and increasing the number of main transformers not only requires huge investments and long construction periods, but it is also difficult to open up new line corridors near major cities where land is scarce.

[0004] Existing dynamic capacity expansion assessment methods for transmission lines and transformers mainly consider the overload capacity of individual equipment, without taking into account that the transmission line and transformer are a whole. There may be situations where the line has overload operating space but the main transformer cannot safely deliver the required power, or the main transformer has overload operating space but the line section cannot safely transmit the required power. At the same time, the power flow distribution within the transmission section is not taken into account, resulting in poor practicality of the existing solutions. Summary of the Invention

[0005] To address the problems in the prior art, this application provides a dynamic current-carrying capacity assessment method and also relates to a dynamic current-carrying capacity assessment device.

[0006] This application provides a method for evaluating dynamic current-carrying capacity, including:

[0007] Calculate the first electrical demand capacity of the transmission section and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section;

[0008] Based on the comparison between the first electrical demand capacity and the first overload capacity, determine whether to implement power flow distribution;

[0009] If not, the dynamic current carrying capacity is calculated directly; if yes, after the power flow distribution is executed, the dynamic current carrying capacity is determined based on the comparison results of the first electrical demand capacity, the first overload capacity, and the second overload capacity.

[0010] Optionally, the power flow distribution includes:

[0011] Based on the importance of the power supply areas of each transmission line within the aforementioned transmission section, a power flow allocation coefficient K is assigned to each line. l The first conveying capacity is equal to the first overload capacity.

[0012] Optionally, the dynamic current-carrying capacity includes:

[0013] The minimum value among the product of the first overload capacity and the power flow distribution coefficient Kl, the first power demand, and the second overload capacity is taken as the dynamic current carrying capacity of the transmission line.

[0014] Optionally, the expression for the first overload capacity is as follows:

[0015]

[0016] Where, θ h θ represents the transformer hot spot temperature. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

[0017] Optionally, the expression for the second overload capacity is as follows:

[0018]

[0019] Among them, P l For dynamic current-carrying capacity, θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the current-carrying capacity. a The ambient temperature is s, the heat absorption coefficient of the conductor is k. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let U be the solar radiation intensity on the conductor, and U be the operating voltage of the conductor. The power factor.

[0020] This application also provides a dynamic current-carrying capacity assessment device, comprising:

[0021] The calculation module is used to calculate the first electrical demand capacity and the first overload capacity of the main transformer of the transmission section, as well as the second demand capacity and the second overload capacity of each transmission line within the transmission section.

[0022] The configuration module is used to determine whether to perform power flow distribution based on the comparison result between the first power demand capacity and the first overload capacity.

[0023] If the execution module does not perform the calculation, it directly calculates the dynamic current carrying capacity. If it does, it executes the power flow distribution and determines the dynamic current carrying capacity based on the comparison results of the first electrical demand capacity, the first overload capacity, and the second overload capacity.

[0024] Optionally, the power flow distribution in the configuration module includes:

[0025] Based on the importance of the power supply areas of each transmission line within the aforementioned transmission section, a power flow allocation coefficient K is assigned to each line. l Let the first conveying capacity be equal to the first overload capacity.

[0026] Optionally, the execution module performs dynamic current carrying capacity calculation, including:

[0027] The minimum value among the product of the first overload capacity and the power flow distribution coefficient Kl, the first power demand, and the second overload capacity is taken as the dynamic current carrying capacity of the transmission line.

[0028] Optionally, the calculation module calculates the first overload capacity using the following expression:

[0029]

[0030] Where, θ h θ represents the transformer hot spot temperature. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

[0031] Optionally, the calculation module calculates the second overload capacity using the following expression:

[0032]

[0033] Among them, P l For dynamic current-carrying capacity, θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the current-carrying capacity. a The ambient temperature is s, the heat absorption coefficient of the conductor is k. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let U be the solar radiation intensity on the conductor, and U be the operating voltage of the conductor. The power factor.

[0034] The advantages of this application compared to the prior art are:

[0035] A dynamic current-carrying capacity assessment method includes: calculating the first electrical demand capacity of a transmission section and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section; determining whether to implement power flow distribution based on the comparison result of the first electrical demand capacity and the first overload capacity; if not, directly calculating the dynamic current-carrying capacity; if so, after implementing the power flow distribution, determining the dynamic current-carrying capacity based on the comparison result of the first electrical demand capacity, the first overload capacity, and the second overload capacity. This method comprehensively considers both the transmission line section and the main transformer, calculating the actual overload capacity of the transmission lines and transformers while simultaneously considering the power flow distribution within the transmission section, thereby providing the transmission capacity of the transformer and the lines within the transmission section. This can guide the capacity expansion operation of power grid equipment. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the dynamic current carrying capacity assessment process in this application;

[0037] Figure 2 This is a schematic diagram of the dynamic current carrying capacity assessment logic in this application;

[0038] Figure 3 This is a schematic diagram of the dynamic current-carrying capacity assessment device in this application. Detailed Implementation

[0039] The following are examples of specific implementation processes provided to illustrate the technical solutions to be protected in this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can implement this application by different technical means under the guidance of the concept of this application. Therefore, this application is not limited to the specific embodiments below.

[0040] A dynamic current-carrying capacity assessment method includes: calculating the first electrical demand capacity of a transmission section and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section; determining whether to implement power flow distribution based on the comparison result of the first electrical demand capacity and the first overload capacity; if not, directly calculating the dynamic current-carrying capacity; if so, after implementing the power flow distribution, determining the dynamic current-carrying capacity based on the comparison result of the first electrical demand capacity, the first overload capacity, and the second overload capacity. This method comprehensively considers both the transmission line section and the main transformer, calculating the actual overload capacity of the transmission lines and transformers while simultaneously considering the power flow distribution within the transmission section, thereby providing the transmission capacity of the transformer and the lines within the transmission section. This can guide the capacity expansion operation of power grid equipment.

[0041] Figure 1 This is a schematic diagram of the dynamic current carrying capacity assessment process in this application.

[0042] Please refer to Figure 1 As shown, this application mainly treats transmission lines and main transformers in a power grid as a whole for dynamic capacity expansion calculation. Combining power flow distribution requirements, it proposes a method for evaluating the dynamic current-carrying capacity of power grid equipment. This method can guide capacity expansion operations while ensuring the safe operation of both transmission lines and main transformers. Specifically, the execution steps of this method are as follows:

[0043] S101 calculates the first electrical demand capacity and the first overload capacity of the main transformer of the transmission section, as well as the second demand capacity and the second overload capacity of each transmission line within the transmission section.

[0044] S102 determines whether to perform power flow distribution based on the comparison result of the first electrical demand capacity and the first overload capacity;

[0045] If S103 is not, then the dynamic current carrying capacity is directly calculated; if it is, then after executing the power flow distribution, the dynamic current carrying capacity is determined based on the comparison results of the first electrical demand capacity, the first overload capacity, and the second overload capacity.

[0046] Figure 2 This is a schematic diagram of the dynamic current carrying capacity assessment logic in this application.

[0047] Please combine Figure 1 and Figure 2 As shown, in step 1, the required capacity is calculated based on the power demand of the power supply area of ​​the transmission section, and the first required capacity Pls of the transmission section is determined accordingly. Pls is the sum of the transmission demand Plis of each transmission line within the transmission section.

[0048] It should be noted that in the following description, the overload capacity of the transformer is the first overload capacity, and the overload capacity of each transmission line is the second overload capacity.

[0049] The overload capacity of the main transformer responsible for transmitting electrical energy across this transmission section is calculated using the following method:

[0050]

[0051] Among them, P tr For the dynamic overload capacity, θ h θ represents the transformer hot spot temperature. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

[0052] The overload capacity of each transmission line within the transmission section is calculated using the following method:

[0053]

[0054] Among them, P l For dynamic current-carrying capacity, θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the current-carrying capacity. a The ambient temperature is s, the heat absorption coefficient of the conductor is k. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let U be the solar radiation intensity on the conductor, and U be the operating voltage of the conductor. The power factor.

[0055] Based on the above calculations, the first electrical demand capacity and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section, were obtained.

[0056] In step 2, the first overload capacity P is compared. tr With the first demand capacity P ls ;

[0057] If P tr ≧P ls Then compare the transmission capacity demand P of each transmission line within the transmission section. lis With the overload capacity P of the transmission line l If P lis>P l Then P l The value is used as the transmission capacity P of the transmission line. lt The value of P; if P lis ≦P l Then P lis The value is used as the transmission capacity P of the transmission line. lt The value of ; at this time, let the transmission capacity P of the main transformer be . tt The sum of the transmission capacities of all transmission lines, sum(P) lt ).

[0058] If P tr <P ls Based on the importance of the power supply areas of each transmission line within the transmission section, a power flow allocation coefficient K is assigned to each line. l At this time, let the transmission capacity P of the main transformer be... tt Main transformer overload capacity P tr .

[0059] In step 3, based on the power flow distribution coefficient K assigned to each transmission line... l Calculate the overload capacity P of the main transformer. tr *Trend distribution coefficient K l Compare the overload capacity P of the main transformer tr *Trend distribution coefficient K l The accumulation of the power transmission line and the transmission demand P lis Overload capacity P of transmission lines l The minimum value among the three is taken as the transmission capacity P of the transmission line. lt .

[0060] This application also provides a dynamic current carrying capacity assessment device, including: a calculation module 301, a configuration module 302 and a result module 303.

[0061] Figure 3 This is a schematic diagram of the dynamic current-carrying capacity assessment device in this application.

[0062] Please refer to Figure 3 As shown, the calculation module 301 is used to calculate the first electrical demand capacity of the transmission section and the first overload capacity of the main transformer, as well as the second demand capacity and the second overload capacity of each transmission line within the transmission section.

[0063] The required capacity is calculated based on the electricity demand of the area supplied by the transmission section, and the first required capacity Pls of the transmission section is determined accordingly. Pls is the sum of the transmission demand Plis of each transmission line within the transmission section.

[0064] It should be noted that in the following description, the overload capacity of the transformer is the first overload capacity, and the overload capacity of each transmission line is the second overload capacity.

[0065] The overload capacity of the main transformer responsible for transmitting electrical energy across this transmission section is calculated using the following method:

[0066]

[0067] Among them, P tr For the dynamic overload capacity, θ h θ represents the transformer hot spot temperature. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

[0068] The overload capacity of each transmission line within the transmission section is calculated using the following method:

[0069]

[0070] Among them, P l For dynamic current-carrying capacity, θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the current-carrying capacity. a The ambient temperature is s, the heat absorption coefficient of the conductor is k. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let U be the solar radiation intensity on the conductor, and U be the operating voltage of the conductor. The power factor.

[0071] Based on the above calculations, the first electrical demand capacity and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section, were obtained.

[0072] Please refer to Figure 3 As shown, the configuration module 302 is used to determine whether to perform power flow distribution based on the comparison result of the first power demand capacity and the first overload capacity.

[0073] Compare the first overload capacity P tr With the first demand capacity P ls ;

[0074] If P tr ≧Pls Then compare the transmission capacity demand P of each transmission line within the transmission section. lis With the overload capacity P of the transmission line l If P lis >P l Then P l The value is used as the transmission capacity P of the transmission line. lt The value of P; if P lis ≦P l Then P lis The value is used as the transmission capacity P of the transmission line. lt The value of ; at this time, let the transmission capacity P of the main transformer be . tt The sum of the transmission capacities of all transmission lines, sum(P) lt ).

[0075] If P tr <P ls Based on the importance of the power supply areas of each transmission line within the transmission section, a power flow allocation coefficient K is assigned to each line. l At this time, let the transmission capacity P of the main transformer be... tt Main transformer overload capacity P tr .

[0076] Please refer to Figure 3 As shown in the result module, if not, the dynamic current carrying capacity is calculated directly; if yes, the dynamic current carrying capacity is calculated after the power flow distribution is executed.

[0077] Based on the power flow distribution coefficient K assigned to each transmission line l Calculate the overload capacity P of the main transformer. tr *Trend distribution coefficient K l Compare the overload capacity P of the main transformer tr *Trend distribution coefficient K l The accumulation of the power transmission line and the transmission demand P lis Overload capacity P of transmission lines l The minimum value among the three is taken as the transmission capacity P of the transmission line. lt .

[0078] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0079] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0083] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for evaluating dynamic current-carrying capacity, characterized in that, include: Calculate the first electrical demand capacity of the transmission section and the first overload capacity of the main transformer, as well as the second overload capacity of each transmission line within the transmission section; Based on the comparison result of the first electrical demand capacity and the first overload capacity, determine whether to perform power flow distribution; if not, directly calculate the dynamic current carrying capacity; if so, after performing the power flow distribution, determine the dynamic current carrying capacity based on the comparison result of the first electrical demand capacity, the first overload capacity, and the second overload capacity, specifically including: comparing the first overload capacity P... tr With the first demand capacity P ls If P tr ≧P ls Then compare the transmission capacity demand P of each transmission line within the transmission section. lis With the second overload capacity P l If P lis >P l Then P l The value is used as the transmission capacity P of the transmission line. lt The value of P; if P lis ≦P l Then P lis The value is used as the transmission capacity P of the transmission line. lt The value of ; at this time, let the transmission capacity P of the main transformer be . tt The sum of the transmission capacities of all transmission lines, sum(P) lt If P tr <P ls Based on the importance of the power supply area of ​​each transmission line within the transmission section, a power flow allocation coefficient K is assigned to each line. l At this time, let the transmission capacity P of the main transformer be... tt The first overload capacity P tr Based on the power flow distribution coefficient K assigned to each transmission line l Calculate the first overload capacity P tr *Trend distribution coefficient K l Compared with the first overload capacity P tr *Trend distribution coefficient K l The accumulation of the power transmission line and the transmission demand P lis The second overload capacity P l The minimum value among the three is taken as the transmission capacity P of the transmission line. lt .

2. The dynamic current-carrying capacity assessment method according to claim 1, characterized in that, The expression for the first overload capacity is as follows: Where, θ h θ represents the hot spot temperature of the transformer. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

3. The dynamic current-carrying capacity assessment method according to claim 1, characterized in that, The expression for the second overload capacity is as follows: Among them, P l The second overload capacity is given by θ, where θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the wind speed. a For ambient temperature, α s k is the heat absorption coefficient of the conductor. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let be the solar radiation intensity on the conductor, U be the conductor operating voltage, and be the power factor.

4. A dynamic current-carrying capacity assessment device, characterized in that, include: The calculation module is used to calculate the first electrical demand capacity of the transmission section and the first overload capacity of the main transformer, as well as the second demand capacity and second overload capacity of each transmission line within the transmission section. The configuration module is used to determine whether to perform power flow distribution based on the comparison result between the first electrical demand capacity and the first overload capacity. If the execution module does not perform the calculation, it directly calculates the dynamic current carrying capacity. If it does perform the power flow distribution, it determines the dynamic current carrying capacity based on the comparison results of the first electrical demand capacity, the first overload capacity, and the second overload capacity. The configuration module and execution module specifically include: comparing the first overload capacity P. tr With the first demand capacity P ls If P tr ≧P ls Then compare the transmission capacity demand P of each transmission line within the transmission section. lis With the second overload capacity P l If P lis >P l Then P l The value is used as the transmission capacity P of the transmission line. lt The value of P; if P lis ≦P l Then P lis The value is used as the transmission capacity P of the transmission line. lt The value of ; at this time, let the transmission capacity P of the main transformer be . tt The sum of the transmission capacities of all transmission lines, sum(P) lt If P tr <P ls Based on the importance of the power supply area of ​​each transmission line within the transmission section, a power flow allocation coefficient K is assigned to each line. l At this time, let the transmission capacity P of the main transformer be... tt The first overload capacity P tr Based on the power flow distribution coefficient K assigned to each transmission line l Calculate the first overload capacity P tr *Trend distribution coefficient K l Compared with the first overload capacity P tr *Trend distribution coefficient K l The accumulation of the power transmission line and the transmission demand P lis The second overload capacity P l The minimum value among the three is taken as the transmission capacity P of the transmission line. lt .

5. The dynamic current-carrying capacity assessment device according to claim 4, characterized in that, The expression for the first overload capacity is as follows: Where, θ h θ represents the hot spot temperature of the transformer. a For ambient temperature, Δθ or R is the steady-state temperature rise of the top oil of the main transformer under rated loss, R is the ratio of load loss to no-load loss of the main transformer under rated current, K is the load factor (load current / rated current), x is the oil index, y is the winding index, H is the hot spot factor, and g is the temperature rise of the top oil of the main transformer under rated loss. r P represents the gradient of the winding average temperature with respect to the oil average temperature under rated current. Rate The rated capacity of the main transformer.

6. The dynamic current-carrying capacity assessment device according to claim 4, characterized in that, The expression for the second overload capacity is as follows: Among them, P l The second overload capacity is given by θ, where θ is the current-carrying temperature rise of the conductor, V is the wind speed, D is the outer diameter of the conductor, ε is the emissivity of the conductor surface, S is the Stefan-Boltzmann constant, and t is the wind speed. a For ambient temperature, α s k is the heat absorption coefficient of the conductor. t R is the AC / DC resistance ratio. dt I is the DC resistance at t℃. s Let be the solar radiation intensity on the conductor, U be the conductor operating voltage, and be the power factor.

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