• Journal of the Korean Geosynthetics Society
• /
• v.12 no.1
• /
• pp.83-92
• /
• 2013

Backfill material with thermal resistivity which has $50^{\circ}C$-cm/Watt in wet and $100^{\circ}C$-cm/Watt in dry is requested to improve the power transfer capability for dissipation of heat production in underground power cables. In the field test performed by buried cable backfills, the backfill material developed from this study is compared with river sand and weathered soil (native soil) to investigate the effect of heat transfer in various seasons and locations of thermal sensors. As a result, the developed backfill material is faster approaching yielding temperature (critical heat) than that of river sand and weathered soil, and it has good dissipation capacity rather than other materials by keeping moisture content at dry season.

• Electric Engineers Magazine
• /
• v.232 no.12
• /
• pp.18-23
• /
• 2001

케이블 인입시 손상을 방지하기 위하여 케이블이 타시설물에 접촉 우려가 있는 장소에는 로라, 쉬트 및 ELP 관 등을 사용하여 케이블 포털시는 캐터필러 및 로러를 사용하므로 인입장력 및 측압에 대해서는 고려하지 않아도 되겠으나 인입속도 및 포설 곡률반경 등에 대해서는 관로식 케이블 포설의 경우와 같이 주의가 요구된다.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.663-664
• /
• 2007

지중송전선로 건설공사에 154kV 장조장 케이블 드럼개발 및 트레일러 일체형 Under Roller 방식을 이용한 포설장비를 개발하여 현장에 적용함으로써 신기술 신개발 공법 적용으로 인한 국제경쟁력 향상 뿐만 아니라 접속경간의 장조장 설계로 케이블 접속개소 감소로 인한 공사비절감과 공사기간 단축에 크게 기여하였다. 이와 동시에 공사를 위한 도로점용 단축으로 민원발생을 크게 감소시켰다. 현행 도로법 규제로 케이블의 운반중량이 제한되었던 케이블 표준 경간을 450m에서 최대 700m까지 가능하여 접속개소의 유연성이 확보되었을 뿐만 아니라 토목구조물(전력구,관로등)공사의 다양한 설계방법을 적용할 수 있게 되었다.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.553-554
• /
• 2011

도심지간 대용량 전력수송을 담당하는 지중송전케이블의 설비 신뢰성 향상과 공사원가 절감을 위해 적정 포설길이의 결정과 접속함의 최적 배치가 중요하며, 이러한 시스템 설계에 있어서 허용 포설장력과 측압은 여러 중요 요소 중 하나가 된다. 특히, 허용측압 계산과정에서 적용중인 최대 측압값에 대한 실증적 검증과 건정성 확인시험을 통해 케이블 특성에 가장 적정한 값을 도출하고, 실 계통에 적용함으로서 최적 시스템 설계가 구현될 것이다. 따라서 본 연구에서는 지중송전케이블을 관로에 포설시 곡률부에서 발생하는 측압을 여러 case별로 모의할 수 있도록 실증설비를 구축하였고, 실제 작용되는 측면하중을 로드셀을 이용하여 측정하였다. 본 연구결과로 안전율을 고려한 최적의 허용측압이 결정되었으며, 이러한 허용측압의 확대를 통해 장경간 케이블 포설의 이론 정립이 가능하게 되었다.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.6
• /
• pp.41-52
• /
• 2005

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need fur cable backfill materials that can maintain a low thermal resistivity even while subjected to high temperatures for prolonged periods. Temperatures greater than $50^{\circ}C\;to\;60^{\circ}C$ may lead to breakdown of cable insulation and thermal runaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aimed at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. Tests were carried out for Dongrim river sand, a relatively uniform sand of very high thermal resistivity, $50^{\circ}C-cm/watt\;at\;10\%$ water content, $260^{\circ}C-cnuwatt$ when dry, and Jinsan granite screenings, and D-2 (sand and granite screenings mixture), E-1 (rubble and granite screenings mixture), a well-graded materials with low thermal resistivity, about $35^{\circ}C-cm/watt$ when at 10 percent water content, $100^{\circ}C-cm/watt$ when dry. Based on this research, 3 types of backfill materials were suggested for improved materials with low thermal resistivity and the applicability was assessed through field tests.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.1
• /
• pp.13-26
• /
• 2011

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need for cable backfill materials to be maintained at a low thermal resistivity during the service period. Temperatures greater than $50^{\circ}C$ to $60^{\circ}C$ may lead to breakdown of cable insulation and thermal runaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aimed at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. The results of Dong-rim river sand (relatively uniform) show that as water content level increases, thermal resistivity tends to decrease, whereas the thermal resistivity on dry condition is very high value($260^{\circ}C-cm/watt$). In addition, other materials(such as Jinsan granite screenings, A-2(sand and gravel mixture), E-1(rubble and granite screenings mixture) and SGFC(sand, gravel, fly-ash and cement mixture)) are well-graded materials with low thermal resistivity($100^{\circ}C-cm/watt$ when dry). Based on this research, 4 types of improved materials were suggested as the environmentally friendly backfill materials with low thermal resistivity.

• Journal of the Korean Geosynthetics Society
• /
• v.10 no.4
• /
• pp.123-130
• /
• 2011

In the precedent study it was presented that the comparison of thermal resistivity using various backfill materials including river sand regarding water content, dry unit weight and particle size distribution. Based on the precedent study, this study focused on developing the optimized backfill material that would improve the power transfer capability and minimize the thermal runaway due to an increase of power transmission capacity of underground power cables. When raw materials, such as river sand, recycled sand, crush rock and stone powder, are used for a backfill material, they has not efficient thermal resistivity around underground power cables. Thus, laboratory tests are performed by mixing Fly-ash, slag and floc with them, and then it is found that the optimized backfill material are required proper water content and maximum density. Through various experimental test, when coarse material, crush rock, is mixed with recycled sand, stone powder, slag or floc for a dense material, the thermal resistivity of it has $50^{\circ}C$-cm/Watt at optimum moisture content, and the increase of thermal resistivity does not happen in dry condition. The result of experiments approach the optimization of the backfill materials for underground power cables.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.4
• /
• pp.263-276
• /
• 1992

The transmission current in a power cable is determined under the condition of separate pipe cooling. To this end, the thermal analysis is conducted with the standard condition of separate pipe cooling system, which constitutes one of the underground power transmission system. The changes of transmission current in a power cable with respect to the variation of temperatures and flow rates of inlet cooling water as well as the cooling spans are also determined. As a consequnce, the corresponding transmission current is shown to vary within allowable limit, resulting in the linear variation of the current for most of the cable routes. The abrupt changes of current, however, for the given flow rate of inlet cooling water in some cooling span lead to the adverse effects on the smooth current transmission within the underground power transmission system. In practice, it is expected that the desinging of the separate pipe cooling system in conjunction with the evaluation of system capacity should take into account the effects of design condition on the inlet cooling flow rate.

• Proceedings of the KIEE Conference
• /
• 2005.07a
• /
• pp.597-599
• /
• 2005

국내 지중배전계통에 사용되는 케이블은 경제성을 이유로 송전급 케이블에 준하는 신뢰성을 확보하지 못하고 있다. 초창기 CNCV 케이블로부터 지속적으로 성능이 향상되어 왔음에도 불구하고 여전히 수분침투에 의한 수트리 열화와 반도전층 계면의 전계집중으로 인한 케이블 고장이 많이 발생하고 있다. 이에 한전에서는 위 두 가지 고장원인을 제거하기 위하여 TR CNCE-W 케이블을 개발하였으며, 2005년 4월 규격을 제정하였다. 새로운 케이블은 지중 관로에 포석될 것이며 지중배전계통의 신뢰성을 한충 향상시키게 된 것이다.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.1068-1075
• /
• 2006

Flow-able backfill is known as soil-cement slurry, void fill, and controlled low-strength material (CLSM). The benefits of CLSM include reduced equipment costs, faster construction, re-excavation in the future, and the ability to place material in confined spaces such as narrow parts nearly impossible for compaction or perimeter of underground power cables. A review of some recent full-scale tests carried out by KEPRI on slurry backfill materials for application in underground power cable was presented. Based on this research, applicability was assessed and compare to results of laboratory tests for improved slurry materials with optimal mixture contents.