LICENCE for AS/NZS Electrical installations – Selection of cables – Cables for alternating voltages up to and including /1 kV – Typical. Electrical installations – Selection of cables – Cables for alternating voltages up to and including /1 kV – Typical Australian installation. The calculator calculates the short circuit fault current at a specified distance in a cable run, based on the source short circuit fault current level. See also the full.

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Determine the minimum conductor size if a voltage drop of 2. If thermal separation is not nzss, the temperature limits of the insulation should be used if it is lower than that of the sheath.

Fixings should be spaced sufficiently far apart to permit lateral movement of multi-core cables or groups of single-core cables.

Taking into account the method of installation employed, the smallest conductor size which has a tabulated current-carrying capacity equal to or in excess of this predetermined minimum value will be considered to be the minimum cable size satisfying the current-carrying capacity Licensed to BGC Cemtech on 25 Aug Soil thermal resistivity varies greatly with soil composition, moisture retention qualities and seasonal weather patterns as well as the variation in load carried by the cable.

For grouped cable circuits see— a Clause 3. The contents of the Standard are a development of the limited provision of Appendix B to AS and it is expected that over subsequent revisions of ASAppendix B will be modified and reduced in size and reference made to this Standard.

Such factors will invariably determine the minimum current requirements for the application of this Standard. The objective of the Standard is to specify current-carrying capacity, voltage drop and short-circuit temperature rise of cables, to provide a method of selection for those types of electric cables and methods of 0308 which are in common use at working voltages up to and including 0.

The cable sizes required to satisfy nze voltage drop restriction are assessed using the formula of Clause nzd. For cables not included in this Standard, cable manufacturers should be consulted for recommendations on the current-carrying capacity and qs methods of installation. Note that these methods result in approximately the same answer. This simplified method gives an approximate but conservative solution assuming maximum cable operating temperatures and the most onerous relationship between load and cable power factors.


Cables install ed in — a a wir ing enclosure on a wall ; or b an enclosed tr ench wit h a removable cover. These conditions are included in this Standard but, in some cases where recalculations have been performed, the tabulated values differ slightly between the Standards.

Cable short circuit fault current calculator AS/NZS |

Similarly, lower ambient temperatures may apply for cables installed in concrete slabs ax or above the surface of the ground.

For other conditions, see Clause 3. However, if work on an installation commenced before publication of this edition, the inspecting authority may grant permission for the installation to be carried out in accordance with the superseded edition. It was published on 5 February Furthermore, a still smaller supply voltage is required to maintain the given load voltage when the current leads the load voltage. Columns 8 to 10 of Table 20 or Table 21, as appropriate.

Three criteria are given for cable selection, as follows: Therefore, the minimum cable size would be 70 mm2. Cables for alternating voltages up to and including 0.

Help Ws Find new research papers in: However, care must be taken that the cable environment and means of support can withstand the higher temperatures.

Assuming worst case conditions of cable operating temperature and load power factor, the simplified method of Clause 4.

Actual values would need to be calculated according to loading. Where there is more than one layer on the same tray or ladder support, Table 22 may be used. For other types of cable installed in locations exposed to direct solar radiation it will be necessary to make some provision for the effects of the increased heating.

From the phasor diagrams of Figure 2 it can be seen that a larger value of supply voltage is required to maintain a given load voltage when the current is lagging the voltage than when the same current and voltage are in phase.


An important aspect concerns the extent and nature of the mechanical restraint imposed on the cable. These conditions have been used to derive the current-carrying capacities tabulated in 30088 3.

Longitudinal expansion of a cable during a short circuit can nzx significant and when this expansion is restrained the resultant forces are considerable. Up to 10 percent of the technical content pages of a Standard may be copied for use exclusively in-house by purchasers of the Standard without payment of a royalty or advice to Standards Australia or Standards New Zealand.

Provision should be made to maintain the recommended configurations to avoid these problems. The higher operating temperature achieved by grouping will not affect the mineral insulation of the unserved cable.

Cable short circuit fault current calculator AS/NZS 3008

Under these conditions care should be taken in the application of the correction factors included in Tables 22 to 26; it may be possible to derive other appropriate correction factors for these installations. A guide to the acceptable short-circuit temperature limits is given in Section 5.

With the same length and disposition of the two cables throughout the circuit, balanced current flow between the parallel cables can be expected.

The use of material in print form or in computer software programs to be used commercially, with nnzs without nxs, or in commercial contracts is subject to the payment of a royalty. Where this occurs the current-carrying capacity given in this Standard is considered to be more accurate, but either value is acceptable for the application of any appropriate requirements of ASe. Specific conditions of installation are laid down in Clauses 3. Where the continuous loading of the cables is assessed as 16, 20, 25, 32, and 40 amps, determine the minimum cable sizes required where the cables are in one of the following conditions: Appropriate calculations are as follows: