scholarly journals Heat Dissipation in Variable Underground Power Cable Beddings: Experiences from a Real Scale Field Experiment

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7189
Author(s):  
Christoph Verschaffel-Drefke ◽  
Markus Schedel ◽  
Constantin Balzer ◽  
Volker Hinrichsen ◽  
Ingo Sass

To prevent accelerated thermal aging or insulation faults in cable systems due to overheating, the current carrying capacity is usually limited by specific conductor temperatures. As the heat produced during the operation of underground cables has to be dissipated to the environment, the actual current carrying capacity of a power cable system is primarily dependent on the thermal properties of the surrounding porous bedding material and soil. To investigate the heat dissipation processes around buried power cables of real scale and with realistic electric loading, a field experiment consisting of a main field with various cable configurations, laid in four different bedding materials, and a side field with additional cable trenches for thermally enhanced bedding materials and protection pipe systems was planned and constructed. The experimental results present the strong influences of the different bedding materials on the maximum cable ampacity. Alongside the importance of the basic thermal properties, the influence of the bedding’s hydraulic properties, especially on the drying and rewetting effects, were observed. Furthermore, an increase in ampacity between 25% and 35% was determined for a cable system in a duct filled with an artificial grouting material compared to a common air-filled ducted system.

Author(s):  
Paweł Ocłoń ◽  
Piotr Cisek ◽  
Marcelina Matysiak

Abstract The circular economy is a closed cycle that allows one to reuse the industrial waste, as well as minimize the energy and resources losses during the production process. This paper presents an innovative idea of the application of a geopolymer cable backfill for underground power cable system installation. The closed cycle, in this case, is formulated as follows: the primary resource is the waste from the combustion of fossil fuels, i.e., fly ash that is utilized to form the geopolymer matrix. The geopolymer then is used as thermal backfill in underground power cable systems. Utilization of combustion by-products in the form of a geopolymer is a highly profitable solution since landfill waste disposal, in this case, generates considerable costs for the electrical energy producers. In typical applications, geopolymers are used as insulators. By adding individual components, the thermal conductivity of 2.0 W/(m K), higher than of typical thermal backfills (Fluidized Thermal Backfill), which value is close to 1.5 W/(m K), is reached. What is very important, geopolymers can absorb water better than typical sand–cement mixtures. As a result, a high thermal conductivity with the temperature increase is maintained. The application of geopolymers as thermal backfills has the potential to improve the flexibility of underground power cable systems, as well as to minimize the material costs of installation. The case study is presented to show the economic benefits of using the combustion by-products as a geopolymer thermal backfill. The finite element method model of an underground power cable system is developed, and optimization of backfill dimensions is provided to minimize the material costs using the geopolymer thermal backfill and to maximize the underground power cable system performance. The main result of this paper is that the application of geopolymers leads to a decrease in underground power cable system costs, compared to traditional backfill (sand–cement mixture). The reason is the higher value of thermal conductivity, which allows selecting a cable with a smaller cross-sectional area. Also, the environmental benefits of geopolymer application for cable bedding are discussed. Graphic abstract


2016 ◽  
Vol 108 ◽  
pp. 233-250 ◽  
Author(s):  
Paweł Ocłoń ◽  
Marco Bittelli ◽  
Piotr Cisek ◽  
Eva Kroener ◽  
Marcin Pilarczyk ◽  
...  

2018 ◽  
Vol 123 ◽  
pp. 162-180 ◽  
Author(s):  
Paweł Ocłoń ◽  
Piotr Cisek ◽  
Monika Rerak ◽  
Dawid Taler ◽  
R. Venkata Rao ◽  
...  

2017 ◽  
Vol 26 (5) ◽  
pp. 465-471 ◽  
Author(s):  
Monika Rerak ◽  
Paweł Ocłoń

2019 ◽  
Vol 158 ◽  
pp. 5317-5322 ◽  
Author(s):  
Lei Quan ◽  
Chenzhao Fu ◽  
Wenrong Si ◽  
Jian Yang ◽  
Qiuwang Wang

Up to the present, effectively all underground power transmission needs have been satisfied by the use of conductors insulated with impregnated paper. In particular, in recent years, the oil-filled cable system using cellulose paper impregnated with oil under pressure has been further developed to meet all immediate and near future needs for higher voltage and higher current power transmission underground. With modem materials and technology, are there more economical solutions and can the needs of the longer future term be met? The basic electrical, thermal, mechanical and reliability constraints which are exerted upon the design of supertension underground power cable systems are considered. The limitations upon further development of the oil-filled cable system are identified. Also, indications are given of the potentials of new insulating materials and novel constructions of cable to provide more economical solutions and greater power transmission capabilities.


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