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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Skip to main content. Log In Sign Up. 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.
Your licence is a 1 user personal user licence and the document may not be stored, transferred or otherwise distributed on a network. Storage, distribution or use on network prohibited. Electrical installations— Selection of cables Part 1. Cables for alternating voltages up to and including 0.
It was published on 5 February It is important therefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto. Suggestions for improvements to Joint Standards, addressed to the nas office of either Standards Australia or Standards New Zealand, are welcomed.
This Standard was issued in draft form for comment as DR Final Australian edition AS This Standard Part 1. Each Part is a complete Standard and requires no reference to the other. Part 2 will deal with cables for use with alternating voltages over 1 kV. 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 installation which are in common use at working voltages up to and including 0.
This Standard differs from the edition as follows: The current ratings for insulated aerial cables are generally based on IEC and on methods proposed by Dr V.
The work carried out by Dr V. In the preparation of this Standard, reference was made to IEC and acknowledgment bzs made of the assistance received from that source.
Cable short circuit fault current calculator AS/NZS 3008
Statements expressed in mandatory terms in notes to tables and figures are deemed to be requirements of this Standard. The time taken to reach this steady state temperature will vary depending on the type of cable and installation conditions.
There will be many cable installations where, because of cable selection practices or demand ss, the current is not sustained at the maximum specified in this Standard. 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 nz correction factors for these installations.
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. Except where the Copyright Act allows and except where provided for below no publications or software produced by Standards Australia or Standards New Zealand may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from Standards Australia or Standards New Zealand.
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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. Inclusion of copyright material in computer software programs is also permitted without royalty payment provided such programs are used exclusively in-house by the creators of the programs. Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended or revised.
The number and date of the Standard should therefore be clearly identified. The use of material in print form or in computer software programs to be used commercially, with or without payment, or in commercial contracts is subject to the payment of a royalty.
Three criteria are given for cable selection, as follows: This Standard provides sustained current-carrying capacities and voltage drop values for those types of electrical cable and installation practices in common use in Australia.
A significant amount of explanatory material is also provided on the application of rating factors which arise from the particular installation conditions of a single circuit or groups of circuits. Also, provided in Section 5 is information on cable selection based on short-circuit temperature limits.
A number of worked examples on cable selection are included in Appendix A. This Standard does not take into account the effects that may occur owing to temperature rise at the terminals of equipment and reference is necessary to AS and the individual equipment Standards. 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 30088 the superseded edition.
These conditions are included in this Standard but, in some cases where recalculations have been performed, the tabulated values differ slightly between the Standards.
Where this occurs the current-carrying capacity given in this Standard is considered to be more accurate, but either value is acceptable for the ass of any appropriate requirements of ASe.
Where the type of cable or method of installation is not specifically covered in the tables of this Standard, current-carrying capacities obtained from alternative specifications such as ERA Report may nnzs employed.
Current-carrying capacities may also be determined by calculation using IEC and appropriate cable data. The subject of assigning a current-carrying capacity to a cyclically or intermittently loaded cable is not covered in 30008 Standard as it normally relates to HV cable installation. AS Conductors —Bare overhead — Aluminium and aluminium alloy Conductors —Bare overhead — Hard-drawn copper Approval and test specification —Electric cables —Thermoplastic insulated — For working voltages up to and including xs.
The minimum cable size will be the smallest nas that satisfies the three requirements. However, with experience it will become apparent that the different nature of installations will determine which of the requirements predominate. In general, the current-carrying capacity requirement will be the most demanding in the relatively shorter route lengths of domestic premises and the like where factors such as semi-enclosed rewirable fuse protection, cable grouping, and thermal insulation occur.
On the other hand the voltage drop limitation is usually nzss deciding factor for longer route lengths which are not subject to the factors mentioned above.
The need to increase cable size to meet the short-circuit temperature rise requirements will ax occur in special situations for the voltage ratings of the cables covered by this Standard. Such factors will invariably determine the minimum current requirements for the application of this Standard.
This derating factor is necessary because of the desire to limit the maximum permissible temperature rise under overload conditions. Where applicable, divide the value of current determined in Step a by the derating factor so determined.
Cable short circuit fault current calculator AS/NZS |
Where applicable, divide the value of current determined by Step a by the derating factor so determined. Tables 2 12 22 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 Refer to the tables of current-carrying capacity for the different cable types, Tables 3 to 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 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.
A more accurate assessment can be made of the actual voltage drop V d using the appropriate equation of Clause 4. This cable size represents the minimum size required to satisfy the short-circuit temperature rise requirements. Tables 2 1 to 2 4 give guidance to the appropriate table of current-carrying capacity for different installation methods for the common types of cable insulant covered by Tables 3 to A specific installation condition is defined and illustrated and alternative installation conditions deemed to have the same current-carrying capacity are also given.
Attention is drawn to tables of rated current-carrying capacity where the standard installation conditions of Clause 3. Tables 3 to 21 give the current-carrying capacities for the variety of different cable types described in Clause 3. The parameters for calculating current ratings in PVC conduits in IEC are still under consideration and considerable disparity was noted between values calculated using available parameters and those previously published in the edition of this Standard as well as other International Standards.
It has therefore been decided in these cases to leave the values previously assigned in the edition of this Standard even though in some cases these appear to be higher than would normally be justified. The ratings, however, for all other cables have been compared with international data and confirm the validity of using the IEC method.
When IEC is suitably amended then it is proposed to undertake a revision of this Standard to correct these anomalies. If non-metallic conduits are used then these ratings are not applicable. Where cables are consistently operating substantially below the limiting temperature of Table 1, the heat losses I 2R and voltage drop IZ will also be reduced. These features could be relevant in determining the optimum economic design of a circuit. 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 Tables 2 1 to 2 4 also draw attention to the different methods of installation which may be assigned the same current-carrying capacity and refers to tables of derating factors applicable where one circuit is run in close proximity to another circuit or circuits.
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. A guide to the acceptable short-circuit temperature limits is given in Section 5.
Cables may be operated in that temperature aas when incorporated as equipment wiring and not exposed to mechanical damage, e. Cables totally surrounded by thermal insulation may be considered not exposed to mechanical damage. Higher continuous operating temperatures are permissible for bare metal-sheathed cables, particularly stainless steel sheathed cables, dependent upon factors such as the following: However, the cables are generally installed in areas of high ambient temperature, such as equipment wiring, and it will be necessary to apply an appropriate temperature correction factor from Table As an alternative to the use of the relatively conservative values given in Table 17, advice may be sought from cable manufacturers.
Consideration should also be given to the voltage drop at this operating temperature. Current-carrying capacities are not given in this Standard for polyethylene served or other forms of MIMS cable used for heating purposes, such as trace heating, tank heating or floor warming.
However, the current-carrying capacity of neutral-screened aerial cables shall be determined zns follows: Columns 8 to 10 of Table 20 or Table 21, as appropriate.
Column s 1 1 to 13 of Table 20 or Table 21, as appropriate. For cables a included in this Standard, cable manufacturers should be consulted for recommendations on the current-carrying capacity and acceptable methods of installation. Different methods of installation vary the rate at which nzw heat generated by the current flow is dissipated to the surrounding medium.
Specific conditions of installation are laid down in Clauses 3. These conditions have been 308 to derive the current-carrying capacities tabulated in Section 3. Where sa number of installation conditions exist along a cable run or variations to the specific conditions occur, reference shall be made to Clauses 3. Table 2 1 contains a reference to the appropriate current-carrying capacity table for cables installed unenclosed in air.
Reflective foil laminates are not considered to be bulk thermal insulation. Table 2 2 contains a reference to the appropriate current-carrying capacity table for cables installed in thermal insulation.
Table 2 3 contains a reference to the appropriate current-carrying capacity table for cables buried direct in the ground. 308 2 4 contains a reference to the appropriate current-carrying capacity table for cables installed in underground wiring enclosures. The use of selected backfill materials over the enclosed cables can improve the conduction of heat away from the cables and nzzs 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.