Abstract
In this paper, the calculation of the conductor temperature is related to the temperature sensor position in high-voltage power cables and four thermal circuits—based on the temperatures of insulation shield, the center of waterproof compound, the aluminum sheath, and the jacket surface are established to calculate the conductor temperature. To examine the effectiveness of conductor temperature calculations, simulation models based on flow characteristics of the air gap between the waterproof compound and the aluminum are built up, and thermocouples are placed at the four radial positions in a 110 kV cross-linked polyethylene (XLPE) insulated power cable to measure the temperatures of four positions. In measurements, six cases of current heating test under three laying environments, such as duct, water, and backfilled soil were carried out. Both errors of the conductor temperature calculation and the simulation based on the temperature of insulation shield were significantly smaller than others under all laying environments. It is the uncertainty of the thermal resistivity, together with the difference of the initial temperature of each radial position by the solar radiation, which led to the above results. The thermal capacitance of the air has little impact on errors. The thermal resistance of the air gap is the largest error source. Compromising the temperature-estimation accuracy and the insulation-damage risk, the waterproof compound is the recommended sensor position to improve the accuracy of conductor-temperature calculation. When the thermal resistances were calculated correctly, the aluminum sheath is also the recommended sensor position besides the waterproof compound.
Highlights
XLPE insulated cable is currently a major type of high-voltage power cable, and its insulation condition is related to conductor temperature [1]
To examine the effectiveness effectiveness conductor temperature calculations, models based on flow characteristics of the air gap between the waterproof compound simulation and the aluminum were flow characteristics of the air gap between the waterproof compound and the aluminum were built up
Both the calculation and finite element method (FEM) simulation proved that when the uncertainty of thermal resistances, especially the air resistance was eliminated, the conductor temperature calculations using the temperatures of the waterproof compound or the aluminum sheath could obtain a close accuracy to that of insulation shield
Summary
XLPE (cross-linked polyethylene) insulated cable is currently a major type of high-voltage power cable, and its insulation condition is related to conductor temperature [1]. The IEC-60287 standard provides the general methods for determining the conductor temperature and current rating in cable, and the IEC-60853 standard provides the methods of cyclic-current rating when the thermal capacities of cable structures cannot be ignored [2,3] These standards are used to calculate the conductor-temperature rise with environmental temperature and laying conditions according to the thermal circuit. Typical arrangements of the sensor in a practical cable in studies are given in the following Table 1 [14,15,16,17,18,19] In these cases, when the sensor has realized the temperature measurement of a certain structure, the real-time conductor temperature could be obtained according to the corresponding thermal circuit [18], or using the numerical methods, like FEM [19].
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