Cable Transmission Capacity Research Articles

Study of balancing methods for parallel cable transmission lines

Cables are of vital importance for the transmission and distribution of electricity within the power grid. However, as the demand for electricity continues to grow, the transmission capacity of a single high-voltage cable is no longer sufficient to meet the required standards. It is therefore imperative to increase the transmission capacity of cables. The deployment of parallel cable transmission represents the most effective strategy for enhancing transmission capacity. However, due to the complex electromagnetic coupling relationship between cables, there is a possibility of current imbalance between cable lines in the same phase, which will have an adverse effect on the normal operation of power equipment and pose a significant threat to the security of the power system. In light of the aforementioned considerations, this paper primarily investigates the mitigation of parallel cable line imbalance. Initially, it examines the parallel cable line current imbalance factors through a theoretical lens, encompassing cable impedance and electromagnetic coupling arrangement. Subsequently, it assesses the efficacy of two proposed methods for reducing the imbalance degree of the parallel cable, namely, the adjustable reactor in series and the addition of a magnetic ring device. Furthermore, finite element simulation software is employed to simulate the two methods and verify their efficacy. Ultimately, a parallel cable plus magnetic ring test is conducted to verify the effectiveness of the magnetic ring.

Introduction of 35 kV km Level Domestic Second Generation High Temperature Superconducting Power Cable Project in Shanghai, China

This paper introduces the basic situation of the 35-kV domestic high temperature superconducting (HTS) power cable project in Shanghai. The target of this project is to construct and put into operation the first 35-kV km level three-phase turn-key HTS power cable project in the world. The cable transmission capacity, cable routing selection, cable structure design, cooling system configuration, etc. of the project are introduced. The project is implemented by the State Grid Corporation Shanghai Electric Power Company. A 35-kV, 1.2-km-long 220-kV inter-substation connecting HTS cable line will be constructed in the core urban area of Shanghai. So far, the type test of the HTS power cable system has been completed, and the construction of the project has begun. The project is expected to be completed and put into operation in the second half of 2020.

Maximum Capacities in Submarine Cables With Fixed Power Constraints for C-Band, C+L-Band, and Multicore Fiber Systems

Achieving greater transmission capacity in submarine optical cables is of great interest as data traffic demands continue to increase worldwide. A significant constraint unique to submarine cable systems is that of electrical power that must be delivered to the entire cable from the terminals at the landing points. Recently, much focus has been on how to maximize the overall cable transmission capacity within fixed electrical power feed constraints. Until recently, all repeatered submarine cable systems were built using the erbium-doped fiber amplifier C-band, but C+L-band systems are now being considered and deployed. In parallel, there has been intense interest in spatial division multiplexing technologies, such as multicore fibers, as potential means to enabling greater transmission capacity in terrestrial and submarine systems. In this work, we examine maximum submarine cable capacities for three types of systems based on single-core fibers with C-band only or C+L-band transmission, and general multicore fiber systems with C-band-only transmission. The analysis is performed on the basis of common fixed power constraints and received signal-to-noise requirements, and comparable fiber-core characteristics. Additional losses for devices, such as C/L-band splitters and fan-in/fan-out modules, are accounted, and their impact on maximum cable capacity is estimated. For multicore fiber systems, other potential effects, such as higher fiber attenuation and crosstalk between cores, are also analyzed and evaluated with respect to capacity impacts. We find that single-core C-band systems offer the highest cable capacity, provided cable designs can accommodate the number of fiber pairs suggested.

Optimization Research on Ampacity of Underground High Voltage Cable Based on Interior Point Method

The conservative operation method which takes unified current-carrying capacity as maximum load current can’t make full use of the overall power transmission capacity of the cable. It’s not the optimal operation state for the cable cluster. In order to improve the transmission capacity of underground cables in cluster, this paper regards the maximum overall load current as the objective function and the temperature of any cables lower than maximum permissible temperature as constraint condition. The interior point method which is very effective for nonlinear problem is put forward to solve the extreme value of the problem and determine the optimal operating current of each loop. The results show that the optimal solutions obtained with the purposed method is able to increase the total load current about 5%. It greatly improves the economic performance of the cable cluster.

Experimental Study on the Emergency Ampacity of XLPE Cable and its Application

In order to solve the contradiction between the increasing demand of power supplies and the difficulty of building new distribution lines, improving the transmission capacity of existing distribution cables is imperative. Using emergency ampacity can increase cable transmission capacity temporarily. Software of calculation emergency ampacity of distribution cable is developed and experiments are undertaken in this paper. The consistency of calculation and experiments shows that the software could calculate emergency ampacity of distribution cable correctly. By the software, the relationship between emergency ampacity and emergency time & initial status are studied here. The research shows that emergency ampacity is much higher than the continuous ampacity. What’s more, the shorter emergency time is, the higher emergency ampacity will be. The lower initial current is, the higher emergency ampacity will be. The more cable circuit number is, the lower emergency ampacity will be but the stronger lifting capacity will be. If emergency ampacity is considered in cable line design stage, cable cross-section or the number of circuit number could be reduced; and if emergency ampacity is considered in emergency load control, the number and capacity of transferring power supply can be reduced. The application the emergency ampacity of distribution cable will result in a great improvement in economy and reliability of power supply.

손실율을 이용한 전력구내 온도특성 해석

To cope with the ever increasing electric power demands in metropolitan areas, a greater underground cable transmission capacity is required. In general, it must be determined whether the temperature in the tunnel maintains the maximum allowable temperature. In order to improve this point, it is used to the loss factor. But, for economic cooling, it is problem to use such loss factor in this country. In this study, based on the load factor in this country, technique for calculating the loss factor has been presents. The suggested method has been tested in a sample section using the computer and the results have shown the usefullness of the suggested method.

Experimental Study on the Cyclic Ampacity and Its Factor of 10 kV XLPE Cable

The load varies periodically, but the peak current of power cable is controlled by its continuous ampacity in China, resulting in the highest conductor temperature is much lower than90℃, the permitted long-term working temperature of XLPE. If the cable load is controlled by its cyclic ampacity, the cable transmission capacity could be used sufficiently. To study the 10 kV XLPE cable cyclic ampacity and its factor, a three-core cable cyclic ampacity calculation software is developed and the cyclic ampacity experiments of direct buried cable are undertaken in this paper. Experiments and research shows that the software calculation is correct and the circuit numbers and daily load factor have an important impact on the cyclic ampacity factor. The cyclic ampacity factor of 0.7 daily load factor is 1.20, which means the peak current is the 1.2 times of continuous ampacity. If the continuous ampacity is instead by the cyclic ampacity to control the cable load, the transmission capacity of the cable can be improved greatly without additional investment.

Method for Calculating Temperature Rise in Cables in Bridge

To permit calculation of the power transmission capacity of cables carried in bridge ducts, methods for calculating the thermal resistance and capacity of a bridge and changes in the transient temperature of cables in bridge ducts are proposed. The validity of these methods is confirmed by tests on bridges. It is also found that the heat trapped in the duct can be estimated by a convection computation taking radiation into due consideration. >

Method for calculating temperature rise in cables in bridge ducts

To permit calculation of the power transmission capacity of cables carried in bridge ducts, methods for calculating the thermal resistance and capacity of a bridge and changes in the transient temperature of cables in bridge ducts are proposed. The validity of these methods is confirmed by tests on bridges. It is also found that the heat trapped in the duct can be estimated by a convection computation taking radiation into due consideration. >