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| CURRENT RATING |
| RECOMMENDATIONS FOR CURRENT RATING |
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-The current rating of power cable is defined by the maximum intensity of current (in amperess), which can flow continuously through the cable, under permanet loading conditions, without any risk of damaging the cable or deterioration of its electrical properties.
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- For three and four core cables, it is usual to assume the same current carrying capactiy for four cores cables as for three core cables. Our calulated values are based actually on three core cables. These values are suitable with enough accuracy also for four cores cables in most cases. Only for large four core cables in air the values may be found to be too conservaitive, due to the large cable surface and consequent high heat dissipation factor.
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- Current carrying capacities have been calculated in accordance with IEC 287 (Calculation of the continuous current rating of cables. |
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- The inner diameter of ducts has been assumed to be at least 1.5 times the diameter of the cable. |
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| - The values given in the tables are valid for one circuit in a three phase system under conditions specified. For grouping cables rating factors must be used. |
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- To obtain the maximum current carrying capacity of a cable operating at different conditions from the standard, you have to multiply the values of the current given in the technical information for the corresponding cable by the rating factors mentioned in the tables from 1 to 11, as follows: |
- It is to be observed that the current carrying capacities presented in JCC technical data sheets are intended as a guide, to assist operating engineers in selecting cables for safety and reliability. |
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Ia= Kt . Is in amperes |
where;
Ia : Current rating at actual operating conditions (amperes)
Is : Current rating at actual operating conditions (amperes)
Kt :Rating factor given in the tables 1 to 11
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Basic assumptions and conditions of installation * Ambient ground temperature:20°C
* Ambient air temperature: 30° C
* Depth of cable burial :1.0 m
* Thermal resistivity of soil: 120°C.Cm/W
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Cables in air are assumed to be protected from direct solar radiation. |
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It has to be noted that Kt the total rating factor: Kt = K1 K2..... Kn |
Single core cables are installed as indicated in the technical information tables. Spacing between cables in flat formation is assumed to be one cable diameter.
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You may have a multiplication of so many. partial rating factors, as many as the differences of laying and operating conditions, from standard conditions. |
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