Practical Aspects of Applying Soil Thermal Stability Measurements to the Rating of Underground Power Cables

Martin, Shawn; Bush, Ashley I.; Black,; Hartley,

doi:10.1109/mper.1981.5511835

Cited by 8 publications

(5 citation statements)

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“…The resistivity of the soil in each condition is proportional to the slope of the respective curves. In the either condition, wet or dry, the soil resistivity may be found using Equation 3 [4]. 4;r p= q effect of that moisture movement on the heat source.…”

Section: Equationmentioning

confidence: 99%

“…In the either condition, wet or dry, the soil resistivity may be found using Equation 3 [4]. 4;r p= q effect of that moisture movement on the heat source. It is reported that laboratory and field tests consistently provide differing results for the resistivity of soil [7].…”

Section: Equationmentioning

confidence: 99%

“…Some sources suggest that for a particular heat rate the drying time of the soil can be adjusted for a larger diameter heat source such as a cable using the measured drying time for the smaller diameter probe using Equation 4 [4] [5] [6].…”

Section: Equationmentioning

confidence: 99%

“…t 2 = soil time to dry with heat source diameter D2 t p = soil time to dry with probe diameter D p It is sometimes suggested that the time to try for a particular diameter of cable being installed may be used to assess the stability of the soil resistivity [4]. However, the criteria used for such an assessment are difficult to define.…”

Section: Equationmentioning

confidence: 99%

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The measurement of soil thermal stability, thermal resistivity, and underground cable ampacity

Malmedal¹,

Bates²,

Cain³

2014

2014 IEEE Rural Electric Power Conference (REPC)

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One of the most important factors affecting underground cable ampacity is the thermal resistivity of the soil. It is well known that thermal resistivity of the soil will vary with moisture content. It is also well known that the heat generated by cables can cause soil drying thus affecting the soil thermal resistivity. The ability of the soil to maintain its thermal resistivity in the presence of a heat source is known as thermal stability. Soil will increase in resistivity due to drying caused by heating from underground sources. This phenomenon makes it challenging for the design engineer to decide how to account for the drying effect in cable ampacity calculations. This paper will examine the information available from standard soil tests and the information these tests may provide relating to the migration of moisture in soil and the resulting changes in soil resistivity. Furthermore a method is suggested for including this information in underground cable ampacity calculations.

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Section: Equationmentioning

confidence: 99%

Section: Equationmentioning

confidence: 99%

Section: Equationmentioning

confidence: 99%

Section: Equationmentioning

confidence: 99%

See 2 more Smart Citations

The measurement of soil thermal stability, thermal resistivity, and underground cable ampacity

Malmedal¹,

Bates²,

Cain³

2014

2014 IEEE Rural Electric Power Conference (REPC)

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show abstract

“…Conductor sizing for buried high voltage cables, such as those in collector systems at wind energy sites, is currently based on a combination of amperage required by the system and ability of the cable to maintain a stable operating temperature (IEC 2006, Martin & Black 1981, Milne & Mochlinski 1964, Neher & McGrath 1957. Operating temperature of cables and the surrounding soil is governed by the soil's ability to transmit cable losses in the form of heat energy away from the cable (Adams & Baljet 1968, Mitchell 1991.…”

Section: Introductionmentioning

confidence: 99%

Impact of Moisture Migration on Thermal Resistivity Testing in Unsaturated Soil

Woodward¹,

Tinjum²

2012

GeoCongress 2012

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This study investigates the impact of moisture redistribution during the measurement of the thermal dry-out curve (i.e., soil thermal resistivity, ρ T , versus moisture content, θ). Thermal dry-out curves are used in energy geotechnics (e.g., geothermal heating and cooling, collector systems at wind energy sites) to quantify the capacity of a soil to store or dissipate heat. Although there is not a standard method for measurement of the ρ T -θ relationship, curves are typically generated by measuring ρ T of remolded or undisturbed specimens at varying water contents, typically with incremental measurements as the specimen is dried. However, drying within a specimen may not be uniform, even in a controlled, low-temperature, drying environment. In this study, a thermal properties probe was used to measure ρ T of remolded cylindrical specimens as the soil was dried in a low-temperature oven. Three horizontal sensor locations (top, middle, and bottom) were used to measure ρ T across the specimen. Water content at the sensor locations was measured and compared to the corresponding ρ T measurement. Thermal resistivity tests were performed at various drying times for three soils: Poorly Graded Sand (SP), Silty Sand (SM), and Sand with Silt (SP-SM). Tests on SM remolded at 95% maximum dry density revealed θ up to nine times higher in the bottom sensor location than in the top sensor location. The test results indicate a need for modification of the standard thermal resistivity testing procedure such that moisture migration within a specimen during drying does not impact the testing accuracy.

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Controlled backfill optimization to achieve high ampacities on transmission cables

Williams

Parmar²,

Conroy³

1994

IEEE Trans. Power Delivery

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Practical Aspects of Applying Soil Thermal Stability Measurements to the Rating of Underground Power Cables

Cited by 8 publications

References 0 publications

The measurement of soil thermal stability, thermal resistivity, and underground cable ampacity

The measurement of soil thermal stability, thermal resistivity, and underground cable ampacity

Impact of Moisture Migration on Thermal Resistivity Testing in Unsaturated Soil

Controlled backfill optimization to achieve high ampacities on transmission cables

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