Academic literature on the topic 'Heat dissipation from underground cables'

Current ratings of buried cables are determined by the characteristics of surrounding soils and cable properties as given in IEC 60287-1-3 (1982). In this standard the soil thermal resistivity of the surrounding soil is supposed to be varies from 0.5 oC m/w to 1.2 oC m/w but under loading the heat dissipated from underground power cables increases the soil thermal resistivity and this may leads to cable thermal failure and thermal instability of the soil around the underground cables. For this reason de-rating factors for cable loading taking the dry zone formation into consideration has to be considered during distribution cable network design. Several approaches have been adopted to establish current ratings of buried cables based on constant values of soil thermal conductivities. Mathematical models are suggested by many researches to study the drying out phenomenon around underground power cables. In this chapter de-rating factor for underground power cables taking dry zone formation into account is calculated depending on IEC 60287-1-3 (1982). This chapter also contains an experimental work carried out on different types of soils to investigate the formation of dry zone phenomena under loading by heat source simulates the underground cables.

Domestic ‘mains’ systems in the UK use AC at 50 Hz. In the USA the systems use 60 Hz. These frequencies are used as they are efficient frequencies for transmission from power generation to the users and minimise the effect of leakage currents due to capacitance, which is discussed later in this chapter. The mains is initially generated in a power station and the power generated there (volts × amps) is enough to supply a number of hospitals and consumers. The voltage and the potential to do work must be transmitted to the user and this is usually achieved with overhead pylons, or sometimes by underground cables. Both types of cable will be designed to carry current, but the higher the current, the greater power lost to heat (I 2R). It is desirable to keep the current as low as possible to reduce this transmission heat loss, and this can be done by making the voltage as high as possible. For a given power, (V × I) there can be a high V and low I or vice versa. The transmission voltage is normally greater than 11 kV. It arrives at a domestic substation and is transformed down to (in the UK) 230 V RMS by a transformer. At the substation, as illustrated in Figure 6.1, one connection of the transformer is firmly bound to earth at what is called the star point, and this forms the start of what is called the neutral lead. The earth connection forms a vital part of electrical safety. The connection on the other side of the transformer is called the live lead and this is at 230 V RMS. These two leads are taken to the individual outlets or mains sockets, the live carrying the voltage to the load, and the neutral lead carrying the return current back to the source of the supply. The earth connection of the mains socket is connected back to the star point separately, although sometimes in older installations this can be earthed locally. In this way only one of the socket points is live, and the other is at near zero potential.

In 1998, EPCOR undertook an inspection program on the condition of 14 of their underground high voltage transmission lines where they crossed the riverbed of the North Saskatchewan River within the City of Edmonton. Based on the findings of this investigation, it was determined that two of the river crossings were at serious risk of mechanical damage. It was decided that they would be replaced by horizontal directional drilling (HDD) methods, at a sufficient depth into the bedrock below the river bottom to remove any risk of failure due to mechanical damage. This paper examines all phases of t

The authors have been proposed and developed snow-melting system using geothermal and solar energy. In summer, solar heat is stored into underground from road surface to underground piles. In winter, the underground heat is utilized to melt snow on the road surface. This system was applied to parking lots and bridges of relatively small scale (less than 1000 m2). Numerical simulation program was also developed to predict temperature field of the system and to evaluate system performance. This program was verified by experimental data only for relatively small scale test area. In addition, appr

Heat transfer from a buried pipe has been a subject of great interest due to its many important engineering applications, which include the underground pipelines for oil and gas transport and the power cables. The problem considered in the present study has applications related to a radiant underfloor heating system in residence and industry. In the existing literature, heat transfer from a buried pipe has been considered for various heat transfer modes and configurations. For example, analytical solutions are readily available for heat conduction from one single cylindrical heat source or mul