Backfill materials for underground power cables, Phase I. Interim report. Thermal resistivity measurement methods, backfill treatments, heat and moisture flow analysis. [HEAT]
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 need for cable backfill materials that can maintain a low thermal resistivity (less than 50/sup 0/C-cm/watt) even while subjected to high temperatures for prolonged periods. The results of studies aimed at development of improved methods for placing backfill around underground power cable systems and special treatments to reduce the thermal resistivity and increase the thermal stability of the backfill materials are reported. The thermal needle method used for measuring the thermal resistivity of backfill materials in the laboratory is discussed. Samples compacted wet and then dried backfill materials were tested. Three water-absorbing polymers for the prevention of water migration were tested and found to retard, but not prevent water migration. Once dried, samples treated with these materials had poorer thermal properties than did the untreated soil. No additives were found that can produce a material with a thermal resistivity significantly less than that of the untreated wet compacted material. A finite element computer program HEAT was used to study transient and steady-state heat flows and temperature distributions for typical buried cable systems. The dominating influence of the thermal resistivity of the trench backfill on the temperature distributions and allowable thermal loading is readily apparent from the analyses. Field tests should be conducted to evaluate both the performance of the most promising backfill treatments and the accuracy of the developed heat and moisture flow predictive methods.
- Research Organization:
- California Univ., Berkeley (USA). Dept. of Civil Engineering
- OSTI ID:
- 5321028
- Report Number(s):
- EPRI-EL-506
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COMPUTER CODES
H CODES
ELECTRIC CABLES
INSTALLATION
UNDERGROUND POWER TRANSMISSION
FEASIBILITY STUDIES
BACKFILLING
COMPUTER CALCULATIONS
HEAT FLOW
HEAT TRANSFER
POLYMERS
POWER TRANSMISSION LINES
ROCKS
SAND
SOILS
TEMPERATURE CONTROL
TEMPERATURE GRADIENTS
THERMAL CONDUCTIVITY
UNDERGROUND
WATER
CABLES
CONDUCTOR DEVICES
CONTROL
ELECTRICAL EQUIPMENT
ENERGY TRANSFER
EQUIPMENT
HYDROGEN COMPOUNDS
LEVELS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POWER TRANSMISSION
THERMODYNAMIC PROPERTIES
200300* - Electric Power Engineering- Power Transmission & Distribution- (-1989)