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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Such factors will invariably determine the minimum current requirements for the application of this Standard. Nze to the tables of current-carrying capacity for the different cable types, Tables 3 to 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.
Table 2 3 contains a reference to the appropriate current-carrying capacity table for cables buried direct in the ground. Tables 2 1 to 2 4 provide a schedule of the installation methods applicable to sheathed and unsheathed elastomer or thermoplastic cables whose current-carrying capacities are given in Tables 3 to The voltage drop values in Tables 40 to 50 may not be applicable under the following conditions: Statements expressed in mandatory terms in notes to tables and figures are deemed to be requirements of this Standard.
Where applicable, divide the value of current determined by Step a by the derating factor so determined. The generalized form of the adiabatic temperature rise equation which is applicable to any starting temperature is as follows: Click here for full conditions of Licence This is a licensed electronic copy of a document where copyright is owned or managed by Standards Australia International.
Where the cables concerned are not of the same size, the spacing will be based on the largest ae diameter in the adjacent groups. Cables install ed in — a a wir ing enclosure on a wall ; or b an enclosed tr ench wit h a removable cover.
Under such conditions the current-carrying capacity given in Tables 3 to 21 shall be corrected by the application of an appropriate rating factor or factors obtained from Tables 22 to Such backfill should completely surround the cable with a minimum thickness of mm and could be used in lieu of the bedding required in AS The appropriate rating factors applicable to Tables 3 to 14 are applicable when the current-carrying capacity of flexible cords and cables is determined in accordance with Item a.
Where the measurements are made while the cables are loaded, e. From the derating factors of Table 22, which vary according to the number nxs enclosed circuits, it can be shown that five parallel circuits of mm2 conductors, as illustrated, are required. In applying these voltage drop values, the smallest permissible conductor is the smallest which satisfies the following equations: Each Part is a complete Standard and zns no reference to the other.
Soil thermal resistivity varies greatly with soil composition, ns retention qualities and seasonal weather patterns as well as nze variation in load carried by the cable. Tables 2 12 3082 3 and 2 4 provide guidance to the installation methods and derating factors applicable to the common elastomer or thermoplastic-insulated cables. Where applicable, divide the value of current determined in Step b by — i the ambient air or soil temperature rating factor selected from Tables 27 1 and 27 2 ; ii the depth of laying rating factor selected from Tables 28 1 and 28 2 ; and iii the soil thermal resistivity rating factor selected from Table It is important therefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto.
For thermoplastic insulating materials nxs limits must be applied with caution when the cables are either directly buried or securely clamped when in air.
Cable short circuit fault current calculator AS/NZS 3008
Applying these derating factors for, say, V, 4 mm 2 conductors, from Table 6 a three-phase current-carrying capacity is 26 A while the single-phase value from Table 3 is 30 A. Specific guidance on the use of Tables 22 to 26 is given in Clauses 3.
Cables wit h minimum spacings in air as Tables 9 and 10 shown and installed — Two-core see Note 5 a spaced fr om a wall or vert ical surface; 9 cables Columns 2 and 3 b supported on ladders, racks, perf orated or unperf orated trays, cleats or hangers; c in a switchboard or similar enclosure; 24 or Tables 12 and 13 10 Three-core see Note 5 cables Columns 2 and 3 d suspended fr om a catenary or as a self – 11 supported overhead cable. Columns 8 to 10 of Table 20 or Table 21, as appropriate.
The use of selected backfill materials over the enclosed cables can improve the conduction of heat away from the cables and as a consequence higher current-carrying capacities, in the order of that for buried direct cables, can be sustained by the short lengths of enclosed cables. Fixings should be spaced sufficiently far apart to permit lateral movement of multi-core cables or groups of single-core cables.
Australian requests for permission and information on commercial software royalties should be directed to the head office of Standards Australia. In practice the voltage drop is very much smaller than the supply voltage and the difference between the magnitudes of the supply and load voltages may be approximated by the following equation: If possible the actual value should be measured along the cable route as it can greatly affect the current-carrying capacity of the cable.
It will be noted that the influence of skin effect on resistance has been taken into account in the specification of cable resistance values in Tables 34 to 39 and as such are referred to as values of a. Therefore the voltage drop on a single-phase basis will only be that associated with the current flowing in one active conductor, i. In many cases this will still be necessary if the out-of-balance conditions are inconsistent or intermittent.
Permission may be conditional on an appropriate royalty payment. The need to increase cable size to meet the short-circuit temperature rise requirements will only occur in special situations for the voltage ratings of the cables covered by this Standard. Up to 10 percent of the technical content pages of a Standard may be copied nza use exclusively in-house by purchasers of the Standard without payment of a royalty or advice to Standards Australia or Standards New Zealand.
The factors are also applicable to groups of single-core cables making up 300 circuits in accordance with Clause 3.
Cable short circuit fault current calculator AS/NZS |
The current-carrying capacity assigned to the underground portion of the cable run may be assigned to the above-ground portion where the prevailing installation conditions maintain the final operating temperature of the cable within the limits given in Table 1. A more accurate assessment can be made of the actual voltage drop V d using the appropriate equation of Clause 4.
Alternative arrangements of the cables, e. It nz be seen that in the particular instance where the cable power factor and the load power factor are equal, the voltage drop V d is a maximum of IZc as discussed in Clause 4.
Appropriate calculations are as follows: Specific conditions of installation are laid down in Clauses 3.