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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Column s 1 1 to 13 of Table 20 or Table 21, as appropriate. Table 2 2 contains a reference to the appropriate current-carrying capacity table for cables installed in thermal insulation. Specific conditions of installation are laid down in Clauses 3.
For the purpose of determining the maximum voltage drop value in Clause 4. Different methods of installation vary the rate at which the heat generated by the current flow is dissipated to the surrounding medium.
Therefore the voltage drop on a single-phase basis will only be that associated with the current flowing in one active conductor, i. Where a number of circuits are installed in the same group in free air, on a surface, buried direct in the ground or within the same sheath or wiring enclosure, in such a way that they are not independently cooled by the ambient air or the ground, the appropriate derating factor shall be as given in Tables 22 to Cables wit h minimum cable spacings in air Tables 3 and 4 as shown and installed — Two single- 4 see Note 5 a spaced fr om a wall or vert ical surface; core cables Columns 4 and 5 b supported on ladders, racks, perf orated or unperf orated trays, cleats or hangers; c in a switchboard or similar enclosure; 23 or 5 Tables 6 and 7 Three single- see Note 5 core cables Columns 4 and 5 6 d suspended fr om a catenary wire.
In many cases this will still be necessary if the out-of-balance conditions are inconsistent or intermittent.
The voltage drop nzzs phase to neutral is the voltage drop in one cable and the voltage drop between phases is therefore—. The voltage drop IZc is the same in all cases, but because of the different power factors the voltage IZ c is added to the load voltage at a different angle in each case.
It will be noted that the magnitude of the phasors IRc and IXc has been exaggerated with respect to V L in Figure 2 to illustrate the point. A number of worked examples on cable selection are included in Appendix A.
If non-metallic conduits are used then these ratings are not applicable. Cables may be operated in that temperature range when incorporated as equipment wiring and not exposed to mechanical damage, e. Similarly, lower ambient temperatures may apply for cables installed in concrete slabs on or above the surface of the ground. Provision should be made to maintain the recommended configurations to avoid these problems. If thermal separation is not provided, the temperature limits of the insulation should be used if it is lower than that of the sheath.
This derating factor is necessary because of the desire to limit the maximum permissible temperature rise under overload conditions. However, care must be taken that the cable environment and means of support can withstand the higher temperatures.
This Standard was issued in draft form for comment as DR With the same length and disposition of the two cables throughout the circuit, balanced current flow between the parallel cables can be expected. Attention is drawn to tables of rated current-carrying capacity where the standard installation conditions of Clause 3.
Australian requests for permission and information on commercial software royalties should be directed to the head office of Standards Australia. The current-carrying capacity values in the tables are based upon typical installation conditions and a range of different materials as described in Clause 3.
The current-carrying capacities of served cables may bzs 1. 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.
Cable short circuit fault current calculator AS/NZS 3008
Where different materials or installation conditions are used such that the rate of heat dissipation is adversely or favourably affected, lower or higher current-carrying capacities may be obtained respectively. As a result the contribution of these cables to the effects of mutual heating will be small; in the case of cables E and F, almost negligible. In addition the values for bare conductors are based on black weathered conductors and the values for insulated conductors are based on the use of black PVC or XLPE.
Tables 2 1 to 2 4 provide a schedule of the installation methods applicable to sheathed and unsheathed 0308 or thermoplastic cables whose current-carrying capacities are given in Tables 3 to The voltage drop in each cable will then be equal zs ILZc.
For grouped cable circuits see— a Clause 3080.
Cable short circuit fault current calculator AS/NZS |
Statements expressed in mandatory terms in notes to tables and figures are deemed to be requirements of this Standard. 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 aas 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 aa Three-core see Note 5 cables Columns 2 and 3 d suspended fr om a catenary or as a self – 11 supported overhead cable.
Tables 23 and Fixings should be spaced sufficiently far apart to permit lateral movement of multi-core cables or groups of single-core cables. Permission may be conditional on an 3080 royalty payment.
However, the cables are generally ae in areas of high ambient temperature, such as equipment wiring, and it will be necessary to apply an appropriate temperature correction factor from Table From the derating factors of Table 26 2 for groups of underground enclosures, it can be nzd that four conduits or ducts, each containing a circuit of mm2 conductors and touching, as illustrated, are required.
The cable sizes required to satisfy the voltage drop restriction are assessed using the formula of Clause 4. Remember me on this computer. 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 sa the final operating temperature of the cable within the limits given in Table 1.