Cables cross sectional area

The most appropriate choice of cable cross-sectional area and fuse rating are,... 

Cable cross-sectional area should be at least 50 mm, to comply with volt-drop. 

To the basic current requirement is applied the derating faetors for various service conditions, as noted in Section 1.5.4.2. The equipment, devices and components may then be cbosen to be as close (nearest higher) to this rating as possible from the available standard ratings. Based on these ratings, the minimum cross-sectional areas of the other current-carrying parts used in the circuit, such as interconnecting links and the cables-are calculated. 

Cross-sectional area of current-carrying metallic links or cables... 

The ratings and sizes of main components and cables can be selected from manufacturers catalogues. But cables required for the switchgear internal control and power wirings, being typical of all, are normally identified by their cross-sectional area rather than the current ratings. We have therefore piovided the technical data and current ratings for the most common sizes of such cables for a ready reference in Table 13.15. 

The anode effectiveness is only as good as the anode connection and loss of insulation at this point by deep pitting of the HSI or penetration of the anode cable seal will bring about rapid failure. Hydrostatic pressure should be borne in mind when considering the seal required for any depth of water. The useful life of HSI anodes is usually considered at an end after a 33% reduction in diameter, but this depends upon the original diameter, the amount of pitting sustained and the mechanical stresses to be withstood. Thus doubling the cross-sectional area may more than double the effective life of the anode. 

Consider a vertically hanging metal rod, to which a load can be apphed (e.g. a steel cable supporting an elevator), as in Figure 10.3. The load exerts a tensHe force over the entire cross-sectional area of the rod, which is said to be under uniaxial stress since only the stress along one of the principal axes is nonzero. The stress is equal to the force divided by the cross-sectional area over which it is distributed. In linear elastic theory, according to Hooke s law, the magnitude of the strain produced in the rod by a small uniform applied stress is directly proportional to the magnitude of the applied stress. Hence ... 

If the feeders are plain cables or overhead lines then it is a simple matter to choose their cross-sectional areas to match the current at the 125% duty. 

When fuses or moulded case circuit breakers are applied to a circuit it is necessary to ensure that their /-squared-t characteristics coordinate properly with the thermal capabilities of the downstream equipment, especially the cables. In order to determine the /-squared-t characteristics of a protective device it is assumed that the current in the device suddenly changes from a normal load value to the fault value in a very short period of time, i.e. similar to a step change in a control system. Hence for each value of current along the x-axis of the device s time-current characteristic the value of the current squared multiplied by the corresponding time can be plotted. For cables and busbars the /-squared-t function equals a constant (k) for each cross-sectional area of conductor, as explained... 

For XLPE cables the k factor for the /-squared- is 143. The cross-sectional area A is -... 

The depth of the galvanising is specified in the international standards. The cross-sectional area of each armour wire (in a helix and not in a braid) varies from typically 0.9 mm for small power and control cables e.g. 1.5 and 2.5 mm conductors, to 2.5 mm for 400 mm low voltage high... 

For LV cables having a cross-sectional area above approximately 25 mm the conductors would usually be formed into sector shaped conductors. 

The choice of cross-sectional area of cable conductors depends upon several factors, the main factors being -... 

If the time duration t is taken to be 5 seconds then the lowest acceptable cross-sectional area A for the cable for the various insulating materials is -... 

When a multi-core cable of n wires, or a rope of n fibres, replaces a cylindrical rod with the same cross-sectional area (Fig. C.2c and d), each wire has diameter d = Dl n, so has a second moment of area... 

Calculate the resistance of 100m of copper cable of I.Smm cross-sectional area (csa) if the resistivity of copper is taken as17.5 x 10... 

Calculate the resistance of 100m of aluminium cable of 1.5 mm cross-sectional area if the resistivity of aluminium is taken as 28.5 x 10 m. 

Conductor cross- sectional area Reference Method A (enclosed in conduit in an insulated wall, etc.) Reference Method B (enclosed in conduit on a wall or ceiling, or in trunking) Reference Method C (clipped direct) Reference Method E (on a perforated cable tray) or in free air OD D CO O (D... 

Conductor cross-sectional area (mm ) 1 Two-core cable, d.c. (mV/A/m) 2 Two-core cable, single-phase a.c. (mV/A/m) 3 Three- or four-core cable, three-phase (mV/A/m) 4... 

The conductors of a cable are made of either copper or aluminium and may be stranded or solid. Solid conductors are only used in fixed wiring installations and may be shaped in larger cables. Stranded conductors are more flexible and conductor sizes from 4.0 to 25 mm contain seven strands. A10mm conductor, for example, has seven 1.35 mm diameter strands which collectively make up the 10mm cross-sectional area of the cable. Conductors above 25 mm have more than seven strands, depending upon the size of the cable. Flexible cords have multiple strands of very fine wire conductors, as fine as one strand of human hair. This gives the cable its very flexible quality. 

Type of conductor Conductor cross-sectional area (mm ) Cable factor... 

The caravan should be connected to the pitch socket outlet by means of a flexible cable, no longer than 25 m and having a minimum cross-sectional area of 2.5 mm or as detailed in Section 721 of the lET Regulations. 

Note For the spacing of supports for oables having an overaii diameter exceeding 40 mm, and for single-core cables having conductors of cross-sectional area 300 mm and larger, the manufacturer s... 

When pulKng long lengths of cable through a duct or conduit, less than a 50% fill ratio by cross-sectional area is recommended (Fig. 9.108). For one cable, for example, this equates to a 0.71-in outside diameter cable in a 1-in inside diameter duct. Multiple cables can be pulled at once, as long as the tensile load is applied equally to all cables. 

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