A method for reducing the sag difference of sub-conductors of large-section conductors

Abstract

The present invention relates to a method for reducing the sag difference between sub-conductors of a large-section conductor. The method comprises the following steps: establishing a conductor deployment microelement dx creep calculation model to determine the creep elongation of a sub-conductor after deployment; determining a control parameter for reducing the sag difference between the sub-conductors according to the creep elongation of the sub-conductors; formulating a control strategy for reducing the sag difference between the sub-conductors according to the control parameter, so as to achieve the purpose of making the creep amount of each sub-conductor in the laying-out process tend to be consistent, thereby ensuring that the sag difference of each sub-conductor is extremely small, and the method is simple, reliable and easy to adjust.

Description

[Technical field]

[0001] The invention belongs to the technical field of power transmission and transformation engineering construction, and in particular relates to a method for reducing the sag difference of sub-conductors of a large-section conductor. [Background technology]

[0002] With the gradual development of UHV transmission technology, multi-split large-section conductors have been widely used in overhead transmission lines, and the conductor cross-section is getting larger and larger. Since the phased deployment method can use relatively small and less tensioning equipment, it has attracted more and more attention. Therefore, the phased deployment of large-section conductors has gradually become a widely accepted method in the industry to effectively solve equipment constraints and maintain the current construction cost unchanged, and has good promotion value.

[0003] However, due to the inevitable creep differences of sub-conductors during the phased deployment of large-section conductors, unbalanced sag will inevitably occur between the sub-conductors. From the relationship between the length and sag of overhead lines, it can be seen that a small change in line length will cause a large change in sag. The increase in sag will result in insufficient electrical clearance between the conductor and the object being crossed, which may cause line tripping and destroy the stability of the power system, thus adversely affecting the safe and stable operation of the line.

[0004] Therefore, it is necessary to study the construction technology of phased deployment of large-section conductors, propose an effective method to reduce the sag difference of sub-conductors, and solve the current technical difficulties in phased deployment of large-section conductors, so as to effectively ensure the safe and reliable operation of transmission lines. This will play a positive role in promoting the construction of UHV lines and large-section conductors. [Summary of the invention]

[0005] In order to solve the above problems in the prior art, the present invention proposes a method for reducing the sag difference of sub-conductors of a large-section conductor, comprising the following steps:

[0006] (1): Establish a creep calculation model for the deployment of a sub-conductor with a length of L and a deployment speed of v under a certain tension;

[0007] (2): Calculate the creep elongation of each microelement dx;

[0008] (3): Determine the creep elongation of the sub-conductor after deployment;

[0009] (4): Determining a control parameter for reducing the sag difference between the sub-conductors according to the creep elongation of the sub-conductors;

[0010] (5): A control strategy for reducing the sag difference between the sub-conductors is formulated based on the control parameters, so as to achieve the goal of making the creep amount of each sub-conductor in the laying-out process tend to be consistent.

[0011] The creep calculation model of the neutron conductor in step (1) is based on the integral theory, which divides the entire conductor into countless micro-elements dx.

[0012] The creep elongation of each segment dx in step (2) is: ΔL1(x)=a·t1 b ·dx, where a is the coefficient constant for the calculation of the initial elongation of the wire, t1 is the time required to pull a length x at a speed of v, and b is the creep rate variation parameter, which is the exponential constant for the calculation of the initial elongation of the wire.

[0013] The creep elongation of the sub-conductor after it is deployed in step (3) Among them, a is the coefficient constant for calculating the initial elongation of the wire, t0 is the time required to pull the wire length L when the speed is v, and b is the creep rate change parameter, which is the exponential constant for calculating the initial elongation of the wire.

[0014] The control parameters in step (4) are the sub-conductor deployment time t0 and the creep rate variation parameter b, wherein the creep rate variation parameter b is determined by the tension, and the creep rate variation parameter b decreases with the increase of the tension, and the sub-conductor deployment time t0 is determined by the deployment construction process.

[0015] The control strategy for reducing the sag difference between the sub-conductors in step (5) is to apply different pay-out tensions to each sub-conductor according to the different pay-out times of each sub-conductor.

[0016] The beneficial effects of the present invention include: the present invention studies the problems existing in the construction technology of stepwise deployment of large-section conductors, analyzes the initial deformation law of sub-conductors of large-section conductors, establishes a microelement dx creep calculation model for deployment of sub-conductors, clarifies the control parameters for reducing the sag difference between sub-conductors, and applies different laying-out tensions to each sub-conductor to achieve the effect that the creep release amount of each sub-conductor during the laying-out process tends to be consistent, thereby ensuring that the sag difference of each sub-conductor is extremely small, and at the same time is simple, reliable, and easy to adjust.

Brief Description of the Drawings

[0017] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application, but do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 The invention is a calculation model of the method for reducing the sag difference of sub-conductors of a large-section conductor.

[0019] Figure 2 The present invention is a flow chart of a method for reducing sag differences of sub-conductors of a large-section conductor. [Specific implementation method]

[0020] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, wherein the illustrative embodiments and descriptions are only used to explain the present invention but are not intended to limit the present invention.

[0021] According to the current construction status of domestic multi-split large-section conductor sub-conductors, according to the construction process, the number of times of release can generally be 2, 3 and 4 times, etc. Generally, the first release time is 0-9 hours, overnight, the second release time is 24-33 hours, overnight, the third release time is 48-57 hours, overnight; the fourth release time is 72-91 hours, overnight, etc. In a single-circuit AC transmission line, the coefficient constant and change parameters affecting the creep of the conductor are selected according to the principle of both representativeness and convenience of calculation. For example, if the conductor model is ACSR-720 / 50 steel-core aluminum stranded wire, the number of splits of each phase conductor is 4, and each phase is released in 2 times, the three-phase 12 sub-conductors need to be released in 6 times.

[0022] According to the initial extension equation of the dynamic wire ΔL=a·t b …………(1)

[0023] The applicable condition of formula (1) is that a certain length of wire is suspended between two supporting points, a certain tension is applied to the wire, and the tension is loaded to a certain value within the required time. The initial elongation (creep elongation) of the wire at a certain moment can be calculated using formula (1).

[0024] However, the process of laying out the conductor tension is not consistent with the conditions of use of formula (1). The entire section of conductor is not hung on the tower of the laying section in advance and then tension is applied. Instead, the conductor is gradually laid over the entire section at a given tension and a certain speed. Formula (1) cannot be used to directly calculate the creep elongation of the conductor during tension laying.

[0025] According to the construction process of laying out the conductor in batches, during the laying process, the conductor in the wire drum is subjected to a certain traction force after being pulled out by the tension machine, and creep occurs immediately. The time for each wire drum to be pulled from the end to the tail is different, and the creep amount of the entire wire cannot be directly calculated using the formula. Based on the integral theory, the entire wire is divided into countless micro-elements dx, and the creep elongation of the entire wire is the integral of the creep of all micro-elements dx. Its calculation model is as follows Figure 1 shown.

[0026] Assuming that the length of a single reel of wire is L and the pay-off speed is v, the time required to pull a reel of wire is t0 = L / v, and the time required to pull x length is t1 = x / v. Assuming that the creep rate equation of the wire under the pulling tension is ΔL = a·t b , then the creep extension of each microelement dx is

[0027]

[0028] The creep elongation of the coiled conductor after pulling is:

[0029]

[0030] In the construction process of stepwise deployment of multiple split conductors, since the time taken to deploy each sub-conductor is different, the corresponding creep elongation is also different, which leads to differences in the sag of each sub-conductor, thereby affecting the safe distance between the sub-conductors.

[0031] It can be seen from formula (2) that there are two main parameters controlling the creep elongation calculation of each sub-conductor. One is the deployment time t0, and the other is the creep rate variation parameter b, which is an exponential constant for calculating the initial elongation of the conductor. The former depends on the construction process of the deployment in stages, while the latter depends on the tension, temperature and conductor structural parameters. Since the temperature and structural parameters of multiple split conductors are roughly the same in the one-time deployment construction process, the creep variation parameter b of each sub-conductor is mainly related to the wire tension. The relationship between the two is that the creep rate variation parameter b decreases with the increase of tension or increases with the decrease of tension.

[0032] In the traditional stepwise deployment process, the pay-out tension of each sub-conductor is the same, so the creep of each sub-conductor varies with the pay-out time of each sub-conductor. Therefore, in order to avoid the problems in the existing stepwise deployment process, it is necessary to ensure that the creep of each sub-conductor is close to the same after the final pay-out. The present invention proposes to adopt different pay-out tensions according to the different pay-out times of each sub-conductor to achieve the purpose of consistent creep of each sub-conductor during the pay-out process. For this purpose, a flow chart of a method for reducing the sag difference of sub-conductors of a large-section conductor is proposed, as shown in FIG. Figure 2 As shown, it includes the following steps:

[0033] (1): Establish a creep calculation model for the deployment of a sub-conductor with a length of L and a deployment speed of v under a certain tension;

[0034] (2): Calculate the creep elongation of each microelement dx;

[0035] (3): Determine the creep elongation of the sub-conductor after deployment;

[0036] (4): Determining a control parameter for reducing the sag difference between the sub-conductors according to the creep elongation of the sub-conductors;

[0037] (5): A control strategy for reducing the sag difference between the sub-conductors is formulated based on the control parameters, so as to achieve the goal of making the creep amount of each sub-conductor in the laying-out process tend to be consistent.

[0038] The creep calculation model of the neutron conductor in step (1) is based on the integral theory, which divides the entire conductor into countless micro-elements dx.

[0039] The creep elongation of each segment dx in step (2) is: ΔL1(x)=a·t b ·dx, where a is the coefficient constant for the calculation of the initial elongation of the wire, t is the time required to pull a length x at a speed of v, and b is the creep rate variation parameter, which is the exponential constant for the calculation of the initial elongation of the wire.

[0040] The creep elongation of the sub-conductor after it is deployed in step (3) Among them, a is the coefficient constant for calculating the initial elongation of the wire, t0 is the time required to pull the wire length L when the speed is v, and b is the creep rate change parameter, which is the exponential constant for calculating the initial elongation of the wire.

[0041] The control parameters in step (4) are the sub-conductor deployment time t0 and the creep rate variation parameter b, wherein the creep rate variation parameter b is determined by the tension, and the creep rate variation parameter b decreases with the increase of the tension, and the sub-conductor deployment time t0 is determined by the deployment construction process.

[0042] The control strategy for reducing the sag difference between the sub-conductors in step (5) is to apply different pay-out tensions to each sub-conductor according to the different pay-out times of each sub-conductor.

[0043] The above description is only a preferred embodiment of the present invention, so all equivalent changes or modifications made according to the structure, characteristics and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A method for reducing the sag difference of sub-conductors of a large-section conductor, comprising the following steps: (1): Establish a line length of L The deployment speed is v And the microelement dx creep calculation model of the sub-conductor is deployed under a certain tension; (2): Calculate the creep elongation of each microelement dx; (3): Determine the creep elongation of the sub-conductor after deployment; (4): Determine the control parameters for reducing the sag difference between the sub-conductors according to the creep elongation of the sub-conductors; (5): Formulate a control strategy to reduce the sag difference between the sub-conductors according to the control parameters, so as to achieve the purpose of making the creep amount of each sub-conductor in the laying process consistent; The creep elongation of each segment dx in step (2) is: , where a is the coefficient constant for calculating the initial extension of the wire, t1 b is the time required to pull a length x at a speed of v, b is the creep rate variation parameter, and is the exponential constant for calculating the initial elongation of the conductor; The creep elongation of the sub-conductor after it is deployed in step (3) , where a is the coefficient constant for calculating the initial extension of the wire; t0 b is the time required to pull the wire length L at a speed of v; b is the creep rate variation parameter, which is the exponential constant for calculating the initial elongation of the wire; The control parameters in step (4) are the sub-conductor deployment time t0 and the creep rate change parameter b, wherein the creep rate change parameter b is determined by the tension, and the creep rate change parameter b decreases as the tension increases; the sub-conductor deployment time t0 is determined by the deployment construction process; The control strategy for reducing the sag difference between the sub-conductors in step (5) is to apply different pay-out tensions to each sub-conductor according to the different pay-out times of each sub-conductor.

2. A method for reducing the sag difference of sub-conductors of a large-section conductor as claimed in claim 1, characterized in that: The creep calculation model of the micro-element dx of the sub-conductor in step (1) is based on the integral theory and divides the sub-conductor into countless micro-element dx.

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