BS IEC 60287-2-1:2015
$189.07
Electric cables. Calculation of the current rating – Thermal resistance. Calculation of thermal resistance
| Published By | Publication Date | Number of Pages |
| BSI | 2015 | 46 |
This part of IEC 60287 is solely applicable to the conditions of steady-state operation of cables at all alternating voltages, and direct voltages up to 5 kV, buried directly in the ground, in ducts, in troughs or in steel pipes, both with and without partial drying-out of the soil, as well as cables in air. The term “steady state” is intended to mean a continuous constant current (100 % load factor) just sufficient to produce asymptotically the maximum conductor temperature, the surrounding ambient conditions being assumed constant.
This part of IEC 60287 provides formulae for thermal resistance.
The formulae given are essentially literal and designedly leave open the selection of certain important parameters. These may be divided into three groups:
-
parameters related to construction of a cable (for example, thermal resistivity of insulating material) for which representative values have been selected based on published work;
-
parameters related to the surrounding conditions which may vary widely, the selection of which depends on the country in which the cables are used or are to be used;
-
parameters which result from an agreement between manufacturer and user and which involve a margin for security of service (for example, maximum conductor temperature).
Equations given in this part of IEC 60287 for calculating the external thermal resistance of a cable buried directly in the ground or in a buried duct are for a limited number of installation conditions. Where analytical methods are not available for calculation of external thermal resistance finite element methods may be used. Guidance on the use of finite element methods for calculating cable current ratings is given in IEC TR 62095 .
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 4 | English CONTENTS |
| 6 | FOREWORD |
| 8 | INTRODUCTION |
| 9 | 1 Scope 2 Normative references 3 Symbols |
| 12 | 4 Calculation of thermal resistances 4.1 Thermal resistance of the constituent parts of a cable, T1, T2 and T3 4.1.1 General 4.1.2 Thermal resistance between one conductor and sheath T1 |
| 16 | 4.1.3 Thermal resistance between sheath and armour T2 4.1.4 Thermal resistance of outer covering (serving) T3 |
| 17 | 4.1.5 Pipe-type cables |
| 18 | 4.2 External thermal resistance T4 4.2.1 Cables laid in free air |
| 19 | 4.2.2 Single isolated buried cable |
| 20 | 4.2.3 Groups of buried cables (not touching) |
| 22 | 4.2.4 Groups of buried cables (touching) equally loaded |
| 24 | 4.2.5 Buried pipes 4.2.6 Cables in buried troughs 4.2.7 Cables in ducts or pipes |
| 26 | 5 Digital calculation of quantities given graphically 5.1 General 5.2 Geometric factor G for two-core belted cables with circular conductors |
| 27 | 5.3 Geometric factor G for three-core belted cables with circular conductors |
| 28 | 5.4 Thermal resistance of three-core screened cables with circular conductorscompared to that of a corresponding unscreened cable 5.5 Thermal resistance of three-core screened cables with sector-shaped conductors compared to that of a corresponding unscreened cable |
| 29 | 5.6 Curve for for obtaining the thermal resistance of the filling material between the sheaths and armour of SL and SA type cables 5.7 Calculation of s by means of a diagram |
| 31 | Tables Table 1 – Thermal resistivities of materials |
| 32 | Table 2 – Values for constants Z, E and g for black surfacesof cables in free air |
| 33 | Table 3 – Absorption coefficient of solar radiationfor cable surfaces Table 4 – Values of constants U, V and Y |
| 34 | Figures Figure 1 – Diagram showing a group of q cables and their reflection inthe ground-air surface |
| 35 | Figure 2 – Geometric factor G for two-core belted cables withcircular conductors (see 4.1.2.2.2) |
| 36 | Figure 3 – Geometric factor G for three-core belted cables withcircular conductors (see 4.1.2.2.4) |
| 37 | Figure 4 – Thermal resistance of three-core screened cables withcircular conductors compared to that of a correspondingunscreened cable (see 4.1.2.3.1) |
| 38 | Figure 5 – Thermal resistance of three-core screened cables withsector-shaped conductors compared with that of a correspondingunscreened cable (see 4.1.2.3.3) |
| 39 | Figure 6 – Geometric factor for obtaining the thermal resistances ofthe filling material between the sheaths and armour of SLand SA type cables (see 4.1.3.2) |
| 40 | Figure 7 – Heat dissipation coefficient for black surfaces of cables in free air, laying condition #1 to #4 |
| 41 | Figure 8 – Heat dissipation coefficient for black surfaces of cables in free air, laying condition #5 to #8 |
| 42 | Figure 9 – Heat dissipation coefficient for black surfaces of cables in free air, laying condition #9 to #10 |
| 43 | Figure 10 – Graph for the calculation of external thermal resistance of cables in air |
| 44 | Bibliography |
Related products
-
BS IEC 60287-2-1:2015 – TC:2020 Edition
Tracked Changes. Electric cables. Calculation of the current rating – Thermal resistance. Calculation of thermal…
