Cable Capacity Research Articles

Ampacity Estimation for Submarine Power Cables Installed in Saturated Seabed—Experimental Studies

The maximum current carrying capacity (ampacity) of power cables depends on the heat transferability of its surrounding medium. Submarine power cable ampacity is calculated conventionally following the international standards defined for underground cables. In reality, the thermal behavior of submarine environments differs significantly from its underground counterpart as the porous sediments are constantly water saturated. In this article, finite element method (FEM) results were used to determine the factors affecting the ampacity in the submarine environment. A method to calculate the ampacity using external thermal resistance considering two series resistances—conductive resistance (of the solid phase sediment) and convective resistance (due to the natural convection in the pore fluid, water) is proposed. An experimental setup was developed to validate the FEM simulations and the numerical method. The results indicated that the inclusion of convective heat transfer in the proposed method obtained a more precise ampacity estimate compared to that of the standard methods.

Examining the Case for Multicore Fibers in Submarine Cable Systems Based on Fiber Count Limits

The potential role of multicore fibers (MCFs) in submarine cable systems is investigated in the context of electrical power limitations and physical fiber count limitations. We compare the maximum cable capacity theoretically possible for cables using MCFs with 2, 3, and 4 cores to that of cables built with conventional single-core fibers. The comparisons are made based on ideal Shannon-limited capacity, systems with constant output power amplifiers, and individual amplification of MCF cores using fan-in/fan-out devices. MCFs are assumed to have nominally uncoupled cores for which crosstalk between cores is a system impairment. We examine the relative cost/bit of systems built with MCFs and single-core fibers when designed for maximum capacity, and when designed for minimum cost/bit operation. The relative capacity of a cable with MCFs depends strongly on the number of fibers able to be physically accommodated and is greatest when the fiber count number is relatively small. We find only small differences in the relative capacities of MCFs with 2-4 cores and that any advantage over single-core fiber systems can be eroded with minimum signal-to-noise ratio (SNR) requirements above the theoretical level near 0 dB that maximizes cable capacity. The cost/bit of MCF cable systems is determined to be higher than that of single-core fiber systems when maximum cable capacity is the design goal, according to the cost model employed and the specific system and fiber parameters assumed here. Different results may be obtained with cost model refinements and different parameters.

Feasibility Assessment of the New Configuration of an Electric Power Grid with 23 kV Tri-axial HTS Power Cables for an Urban Power Supply

The advantage of high temperature superconducting (HTS) power cables is that they can transmit large amounts of power at relatively low voltages, which can be used to reduce the number of lines in transmission cables or to configure a power grid at lower voltages. Because the commercial operation of 23 kV HTS power cables has begun, the optimal configuration between the 154 kV transformer substations and the 23 kV switching stations connected by the 23 kV HTS cables must be reviewed. In this paper, the new power supply model using 23 kV tri-axial HTS cables is presented for an urban power supply, and the economic feasibility is reviewed to present the appropriate cable capacity selection that matches the 23 kV switching stations.

Design of Power Cable Lines Partially Exposed to Direct Solar Radiation—Special Aspects

Power cable lines are usually buried in the ground. However, in some cases, their ending sections are mounted along the supports of overhead lines. This leads to a situation where the cables are exposed to direct solar radiation and, consequentially, overheat. The paper presents the advanced computer modelling of power cables’ heating, considering their insolation as well as the effect of wind. The temperature and current-carrying capacity of power cables—during exposure to direct solar radiation—are evaluated. An effective method of limiting the unfavourable impact of the sun is discussed. In the presence of solar radiation, the proposed method enables a significant increase in the power cables current-carrying capacity.

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.

Optimization of reliable cyclic cable layouts in offshore wind farms

ABSTRACT A novel approach for optimizing reliable cable layouts in offshore wind farms is presented. While optimization models traditionally are designed to suggest acyclic cable routes, those developed in this work recognize that cyclic layouts reduce the consequences of cable failures. The models under study take into account that cables cannot cross each other, which, particularly in instances with restrictive cable capacity, can make it attractive to let cables follow a joint trajectory, and visit turbines without connecting to them. A two-layered optimization process is developed. The outer layer is associated with an integer programming problem, which is subject to simultaneous generation of rows and columns representing cable paths. In the inner layer, a problem identifying feasible low cost paths is solved, guided by optimal dual variable values in the continuous relaxation of the former problem. Results from experimental applications to existing wind farms show good promise of the method.

Study of Electrical Systems in Engineering Faculty Udayana University Bukit Jimbaran

Electrical systems that serve the Dean of electricity load, the electricity load of the Departement of Architecture, Departement of Mechanical Engineering, Departement of Electrical Engineering, Departement of Information Technology, external lighting facilities supplied by transformers with a capacity of 200 KVA. Lately the quality electrical system has begun to decline with frequent interruptions such as the breakdown of electricity to the load, unbalanced load, THD current exceeds the standard, the fuse on the incoming to the parent panel and the fuse on the main panel is often burned, the grounding system resistance value exceeds the standard equipment value, cable temperature exceeds the standard, even voltage rises to 500 volts. The purpose of this study is to determine the causes of disruption of electricity, and produce a new master installation design to improve the system.
 Based on the results of the analysis, it was found that the importance of channel separation between loads to the Dean building with the Departement of Architecture building with cable capacity for the Dean building of NYY 4 x 95 mm2 and the safety of the NFb 200 Ampere mains. For cables to the building load, the Departement of Architecture installed a new main cable with NYY 4 x 50 mm2 cable size and NFb 150A main safety. It is necessary to replace the main NFb safety at the MDP parent panel which supplies the load to the Departement of Mechanical Engineering building from 160 Ampere to 200 Ampere. The entire phase in each panel does not meet the IEEE 519 - 2014 standard, so it is very important to install a filter. Ground resistance values ??on all panels vary above the standard with a value of 12 to 62 ohms. So it needs to be made a new grounding. When using a plate grounding system, the number of plates that need to be planted is 25 sheets with a size of 2m x 1 m with a planting depth of 2 m. Whereas when using a grid type earth system, a grid with a size of 3 meters x 3 meters is needed with a total grid length of 2976 meters and a depth of 3 meters.

Assessing Capacity and Cost/Capacity of 4-Core Multicore Fibers Against Single Core Fibers in Submarine Cable Systems

We assess the potential applicability and performance of multicore fibers (MCFs) against conventional single-core fibers (SCFs) in submarine transmission systems. In particular, we assume 4-core MCFs with nominally uncoupled cores and separate amplification of each MCF core with conventional erbium doped fiber amplifiers (EDFAs) using fan-in/fan-out (FI/FO) devices in the repeaters. We examine the effects of the number of physical fibers accommodated in the cable design, MCF and FI/FO crosstalk, FI/FO loss, span length, transceiver implementation penalty, and minimum required signal-to-noise ratio (SNR). The relative cable capacities offered by the MCF and SCF systems are evaluated under the different conditions. Then the relative cost/capacity for systems built with the two types of fiber are calculated using a system cost model for two conditions: 1) with maximum cable capacity and 2) for minimum overall cost/capacity. The potential role of multicore fibers (MCFs) in submarine cable systems is investigated in the context of electrical power limitations and physical fiber count limitations. Cable capacities are estimated based on ideal Shannon-limited capacity unless a transceiver implementation penalty, or gap-to-Shannon capacity, is applied. The systems are modeled assuming constant output power amplifiers as are commonly deployed in submarine systems. We find that MCFs offer the greatest cable capacity increase for low fiber count cables, but that the cost/capacity can be significantly higher. When minimization of cost/capacity is the design goal, MCF systems remain higher in this metric than SCF systems, while enabling only a small capacity increase at best.

Temperature Analysis Based on Multi-Coupling Field and Ampacity Optimization Calculation of Shore Power Cable Considering Tide Effect

Shore power system that powers berthing ships is gradually becoming widely used worldwide because it helps reduce air and noise pollution. However, due to the bad environment of the port, the influence of the port tide on the temperature distribution and the ampacity of the shore power cable connecting the ship and shore can't be ignored. Therefore, in this paper, a thermal field calculation model of shore power cable based on electromagnetic-thermal-flow coupling field is presented, in which the impact of tide has been considered. And the validity of the coupling model is verified by thermal circuit method base on IEC(International Electrotechnical Commission) 60287 standard. Then, the influence of cable immersion depth, water velocity and temperature, wind speed and air temperature on the temperature distribution of shore power cable was analyzed based on the multi-field coupling model. Finally, the ampacity of shore power cable in different environments is calculated by the combined Newton iterative and numerical simulation method. The results indicate that the conductor temperature firstly decreases and then increases with the immersion depth. And when the immersion depth is small, the wind speed dominates the temperature of the conductor. While the water flow speed plays a leading role in the conductor temperature when the immersion depth is deeper. In addition, the relationship between ambient temperature and capacity of shore power cable is approximately linear.

Study on the Calculation of Cable Emergency Current Capacity Based on Real-time Measurement Data

In actual operation, the cable may bear extra load due to other line faults within a certain time. This load is called the emergency Current Capacity, and this time period is called the emergency time. There are two main ways to solve the emergency Current Capacity using the thermal circuit. One is to take the surface temperature of the cable outer sheath as the boundary of the transient thermal circuit, without considering the influence of laying environment. The other is to use the environmental thermal parameters recommended by IEC standard. Since the actual environment along the cable is complex and changeable, and the environmental thermal parameters are time-varying, both methods will cause errors. In this paper, the environmental thermal parameters are calculated by using the data obtained from the real-time measurement, which is then substituted into the derived formula to obtain the emergency Current Capacity algorithm. The correctness of the algorithm is verified by comparing the results with the ones of FEA simulation and IEC. The results show that: the algorithm proposed in this paper is safe and more accurate. The effects of initial load and emergency time are also be analysed at the same time.

Evaluation of optimal ground motion intensity measures and seismic fragility analysis of a multi-pylon cable-stayed bridge with super-high piers in Mountainous Areas

16 ground motion intensity measures (IMs) were utilized to assess the seismic performance of a multi-pylon cable-stayed bridge with super-high piers in mountainous areas. The best IM was identified based on the practicality, efficiency, proficiency, sufficiency and hazard computability, and was used to carry out the seismic fragility analysis of the bridge. Results show that peak ground velocity (PGV) is the best IM for such a bridge with super-high piers. By using the IM of PGV, the displacement components, such as bearings, suffer the greatest damage. In the case of large earthquakes, the damage probabilities, especially those exceeding the severe state, are very large for the longest cables. However, the possibility of the girder falling off the piers is very small. The transition piers are also seismically vulnerable. The pylons and super-high piers are not seismically vulnerable, although being the main vertical components and very tall. Therefore, the displacement capacity of bearings and the strength capacity of long cables and transition piers should be improved by taking seismic fragility into account.

Effect of Solar Radiation on Current-Carrying Capacity of PVC-insulated Power Cables – the Numerical Point of View

Effect of Solar Radiation on Current-Carrying Capacity of PVC-insulated Power Cables – the Numerical Point of View

Temperature dependent electrical properties of thermoplastic polypropylene nanocomposites for HVDC cable insulation

Polypropylene has been regarded as a potential recyclable insulation material for HVDC cable, which is beneficial to improve the working temperature and transmission capacity of HVDC cables. However, the electrical properties of polymeric insulation materials exhibit apparent temperature dependent characteristics. Temperature influences the generation and migration of charge carriers, thereby affecting the electrical properties. This paper focuses on the electrical properties of polypropylene nanocomposites at different temperatures, including volume resistivity, space charge and DC breakdown strength. The temperature dependent electrical properties of polypropylene are regulated by adding MgO nanoparticles. Based on the characterization of microstructure and trap characteristics, the mechanism of regulating the charge carrier transport process and the electrical properties of the nanocomposites by introducing MgO nanoparticles is explained. The polypropylene nanocomposites show decreased electrical conduction, suppressed space charge accumulation and increased DC breakdown strength, which are desirable for recyclable HVDC cable insulation application. This work may pave a way for tailoring the high temperature electrical properties of polymeric insulation material.

Investigation on dielectric breakdown behavior of thermally aged cross-linked polyethylene cable insulation

With the rapid development of industry and the increasing demand of power supply, the rated voltage class and current-carrying capacity of power cables become higher and higher, causing the severer service and testing conditions for high voltage (HV) power cables. Therefore, the requirement of the quality of cable insulating materials also becomes increasingly higher. The dielectric breakdown strength is one of the most important indices characterizing the quality and present status of insulating materials, and insulating materials and systems undergo dielectric breakdown tests during development and service. A lot of research results on the dielectric breakdown characterization of polyethylene (PE) and cross-linked polyethylene (XLPE) have been reported up to now, however, few systematic investigations about the dielectric breakdown behaviors of the thermally-aged XLPE cable insulation have been reported in details. Generally, the behaviors of dielectric breakdown for HV insulating materials and structures have been known to obey some statistical distributions, including the Weibull statistical distribution. The changes of the parameters characterizing the Weibull statistical distribution, e.g. the scale and shape parameters may be closely related with those of the physical and chemical properties of the insulating materials considered. This paper aims to investigate the behaviors of the changes of the Weibull statistical parameters for XLPE cable specimens with the different degrees of thermal aging and to elucidate their mechanisms. The investigation results show that the dielectric breakdown characteristics of thermally aged XLPE cable insulating materials also fit well with the Weibull statistical distribution and the changes of their Weibull statistical parameters are very sensitive to the degree of thermal aging, which can be effectively used for the diagnosis of PE or XLPE cable insulation and the analysis of its degradation mechanisms.

A Feasibility Study of Smart High-Temperature Superconducting Cable to Improve Stability of KEPCO System

The Korean power system is a very tightly coupled island system. The installed capacity is about 100 GW and the load demand is gradually increasing. Especially in metropolitan areas where the load is concentrated, the system fault current often exceeds the breaker capacity due to the strong connection. The system operator limits the fault current by bus split operations considering the breaker capacity but this reduces system stability. Therefore, various efforts have been made using a fault current limiter to overcome these problems. A smart superconducting (SC) cable is a type of SC power transmission cable. It has not only standard structure of the existing SC power cable but also a fault current limiter. The cable has a SC characteristic in a normal state, while when a fault occurs, it can limit a fault current through generating impedance that adjusts electrical and thermal properties of SC cable and material and cross-sectional area of SC cable. In this paper, a technique is proposed to reduce system fault current while improving the system stability using a smart high-temperature SC cable. In addition, the appropriate cable capacity and locations are selected to improve the reliability of the Korean power systems using the smart SC cables. The proposed locations and capacities will be applied to the smart SC cable development project that started in May last year

Cable Capacity Enhancement by Utilizing Trapezoidal Voltage Waveform

To avoid installation of expensive new underground cable connections in locations where peak load exceeds existing cable capacity, it is advantageous to transfer more power through a cable than its nominal power capacity, without endangering its reliability. Dynamic current rating of cables is a typical approach that is used to exceed the nominal cable capacity for a short time period. In this paper a new method for cable capacity enhancement based on dynamic voltage rating is introduced. The method can be applied if multilevel converters are installed at both ends of cable as will become more commonplace in the future when an inverter rich power system is realized. In this study the influence of trapezoidal voltage waveform on the electric field distribution inside cable insulation is investigated. The results shows that by using trapezoidal waveform it is possible to achieve a more homogeneous field distribution inside the cable insulation. This enables better utilization of the insulation system which translates into higher continuous power transfer capacity.

Discussion on the Improvement of Current Carrying Capacity of AC 500kV Submarine Cable

A three-dimensional electro-thermal coupling physical and mathematical model of the submarine cable landing section together with the cable trench was established to analyze the effect of the current-carrying capacity improvement scheme of the 500kV submarine cable. The effects of three types of submarine cable landing section current carrying capacity improvement schemes were analyzed and compared. The research results show that the flow rate of the medium around the cable in the cable trench (fluid medium), thermal conductivity, temperature of the cooling medium and the arrangement of the submarine cable affect the current carrying capacity. The fluid medium in the cable trench that is forced to flow along the radial direction of the cable can fully exert the heat absorption effect of the cooling system in the cable trench. The greater the thermal conductivity of the medium around the submarine cable, the Joule heat generated in the submarine cable conductor dissipates more quickly, reducing the temperature rise of the cable conductor, which is beneficial to increasing the current carrying capacity of the submarine cable. The research results have guiding significance for the selection and engineering design of submarine cables.

Study on the ampacity of single-core submarine power cable with return conductor

In order to analyze the effect of internal Cu return conductor on ampacity, this paper establish three types of single core submarine power cable and calculate losses and thermal resistances. Results show that the internal return conductor can effectively reduce the cable loss, thereby increase the cable current carrying capacity. Cable with separated return conductor shows highest ampcity. When section area of return conductor increases, ampacity of cable improves correspondingly.

A novel radial cable for restraining tensile failure in steep fill—rock interfaces

It is quite common for fill slopes such as embankments and airport foundations to be constructed in mountainous areas. Steep fill—rock interfaces in such areas undergo tensile failure owing to differences in the stiffness values and tensile strengths of the soil and hard rock. In this study, a new anchor system, termed “radial cable,” is proposed to increase the pullout capacity of cables in the fill; this in turn helps control tensile deformation in the fill slope along the interface. In a radial cable, the steel ropes of a conventional cable are equally and symmetrically separated into three sub-cables (a central sub-cable and two branch sub-cables) with a radial distribution starting from the position of the interface. Moreover, each of the sub-cables is fixed in the fill using short U-shaped rigid rods along the cable length and a rigid baffle at its end to further increase pullout resistance. Experimental and numerical uplift tests were conducted to analyze the pullout capacity and anchoring behavior of the radial cables in soil to study the effect of branching. The reinforcement effect of the radial cables was also examined using a case study.

Surface Potential Simulation for Robust Electrode Placement by MRI Based Human Phantom with FEM Based Quasi-Static Solver for Bioimpedance Measurement.

Estimating cardiac output (CO) and thoracic fluid content (TFC) by non-invasive measurement of thoracic electrical bioimpedance (TEB) is on the rise of becoming clinically established. Dynamic fluid management and detecting and trending excess quasi-static thoracic fluids are of particular interest to benefit the critically ill patient. While the advantages such as easy application and non-invasive assessment are intriguing, there are some challenges. In addition to artifacts due to the patient's movement, instability of the electrode-skin interfaces, the accuracy of the applied current and varying cable capacity because of motion, exact placement of electrodes - or lack thereof - must be considered. In particular the robustness of the electrode placement, i.e., the insensitivity to inaccuracy of electrode placement (actual sensor from the nominal). We propose a new technique for evaluation of electrode placement by simulation with MRI based human phantoms with FEM based quasi-static solver for bioimpedance measurement. Results: We identified alternative electrode positions which lead to an increase in robustness of bioimpedance measurements of up to 9.5 times compared to the standard electrode placement. Simulations suggested an improvement in ECG signal quality which was confirmed by a subject measurement.