AS NZS 3000 5.docx

1、AS NZS 3000 5SECTION 5 EARTHING ARRANGEMENTS AND EARTHING CONDUCTORS第5部分 接地布置和接地导体5.1 GENERAL 概述The requirements of this Section apply to the performance of the earthing arrangements intended to satisfy the safety and functional requirements of the electrical installation in accordance with Section

2、1.5.2 EARTHING ARRANGEMENTS 接地布置5.2.1 General 概述Earthing arrangements may be used jointly or separately for protective or functional purposes, according to the requirements of the electrical installation.5.2.2 For protective purposes Earthing arrangements for protective purposes shall be comprised o

3、f protective earthing conductors used with overcurrent protective devices provided, in the active, for protection against indirect contact and overcurrent.NOTE: The protective earthing conductors should be incorporated in the same wiring enclosure as the associated active conductors or in the near v

4、icinity.5.2.3 For functional purposes 出于功能目的Earthing arrangements for functional purposes shall be comprised of functional earthing conductors provided to ensure correct operation of electrical equipment or to permit reliable and proper functioning of electrical installations.NOTE: Where a clean ear

5、th is specified for a particular item of electrical equipment, the manufacturer of the electrical equipment should be consulted in order to confirm the necessary arrangements.5.2.4 For combined protective and functional purposesWhere earthing for combined protective and functional purposes is requir

6、ed, the requirements for protective purposes (see Clause 5.2.2) shall prevail.5.2.5 Selection and installation 选择和安装The selection and installation of the equipment of the earthing arrangements shall be such that (a) the value of earthing resistance is in accordance with the protective and functional

7、 requirements of the electrical installation and expected to be continuously effective; and(b) earth-fault currents and earth-leakage currents can be carried without danger, particularly from thermal, thermomechanical and electromechanical stresses; and(c) it is adequately robust or has additional m

8、echanical protection appropriate to the assessed conditions of external influence in accordance with Clause 3.3.5.2.6 Precautions 防范措施Precautions shall be taken against the risk of damage to the earthing arrangement and other metallic parts of the electrical installation through electrolysis or galv

9、anic action.5.3 MULTIPLE EARTHED NEUTRAL (MEN) SYSTEM 多重接地中线系统The system of earthing that shall be deemed to satisfy the requirements of Clause 5.1 is the multiple earthed neutral (MEN) system in which the parts of an electrical installation required, under this Standard, to be earthed are connected

10、 to the general mass of earth and, in addition, are connected within the electrical installation to the neutral conductor of the supply system.NOTES:1 Examples of the MEN system of earthing are shown in Figures 5.1 and 5.2.2 Alternative earthing systems that satisfy the general safety and functional

11、 requirements may be used.5.4 EARTHING REQUIREMENTS 接地要求5.4.1 General 概述The exposed conductive parts of electrical equipment shall be earthed where the electrical equipment is (a) installed or might operate in an earthed situation; or(b) not installed in an earthed situation but any exposed conducti

12、ve part of the electrical equipment is electrically continuous with conductive material which is located in an earthed situation.NOTE: The term exposed conductive part does not apply to the following:(a) Conductive parts within an enclosure where the parts cannot be touched unless a key or a tool is

13、 required to remove the covers of the enclosure.(b) Conductive parts within electrical equipment where the parts cannot be touched in normal use and movement of the electrical equipment due to its configuration and size, e.g. some types of washing machines.(c) Conductive parts which are separated fr

14、om live parts by (i) double insulation; or(ii) other conductive parts which are earthed.(d) Conductive parts which are in the form of nameplates, screw heads, covers and similar attachments that cannot become live in the event of failure of insulation of live parts, due to the manner in which they a

15、re supported and fixed.NOTE: Only single phase connections shown for clarity.FIGURE 5.1 MULTIPLE EARTHED NEUTRAL (MEN) SYSTEM OF EARTHINGMEN LINK AT CUSTOMERS MAIN SWITCHBOARDNOTE: Distribution as Figure 5.1FIGURE 5.2 MULTIPLE EARTHED NEUTRAL (MEN) SYSTEM OF EARTHINGMEN LINK REMOTE FROM CUSTOMERS MA

16、IN SWITCHBOARD5.4.2 Connection of electrical equipment to earth 电气设备接地连接Electrical equipment required to be earthed shall be arranged for connection to (a) protective earthing conductors in the form of cables, cords, busbars or similar forms of current-carrying material; or(b) another earthing mediu

17、m such as metallic parts of cables, wiring enclosures, switchboard framework or the like.5.4.3 Resistance of the earthing system 接地系统电阻The resistance from any point on the electrical installation required to be earthed to the point where the main earthing conductor is connected to the neutral conduc

18、tor of the supply system shall be low enough to permit the passage of current necessary to operate the circuit protective devices.The resistance of the main earthing conductor shall be not more than 0.5 ?.NOTE: As described in Appendix B, the maximum resistance of the protective earthing conductor a

19、ssociated with any particular circuit depends on the type and rating of the protective device and the impedance of the live conductors that comprise the circuit.5.5 EARTHING CONDUCTORS 接地导线5.5.1 Size 尺寸5.5.1.1 General 概述The size of an earthing conductor shall be such that it meets the requirements o

20、f Clause 5.2.NOTE: Guidance on the determination of the maximum length of a circuit, in relation to the characteristics of protective devices and the size of the protective earthing conductor, is provided in Appendix B.5.5.1.2 Minimum size 最小尺寸The minimum size of an earthing conductor shall be deter

21、mined as follows:(a) General Except where varied by Items (b) to (f), the minimum size of any copper earthing conductor required for the protection of any portion of an electrical installation shall be determined from Table 5.1in relation to the cross-sectional area of the largest active conductor s

22、upplying the portion of the electrical installation to be protected.The determination method using Table 5.1 may also be applied in the following situations:(i) Where the active conductors in a multiphase circuit comprise different size conductors, the earthing conductor shall be determined in relat

23、ion to the cross-sectional area of the largest active conductor to be protected.(ii) Where the active conductor comprises a number of conductors, connected in parallel, the earthing conductor shall be determined in relation to the summation of the cross-sectional areas of the individual conductors f

24、orming the largest active conductor to be protected.Where the summation of cross-sectional areas does not correspond exactly with the nominal size of the active conductor given in Table 5.1, the conductor shall be determined in relation to the nearest larger size of active conductor.TABLE 5.1 MINIMU

25、M COPPER EARTHING CONDUCTOR SIZE Nominal size of active conductorNominal size of copper earthing conductorWith copper active conductorsWith aluminium active conductors11.52.51*1.5*2.5-46102.52.54-2.52.516253566104665070951625251010161201501853550702525352403004009512012050709550063012012095120* Thes

26、e earthing conductors may be used only where incorprated in a multicore cable or flexible cord, other than a lift traveling cable, in accordance with Clause 5.5.1.2(e)(ii) and (iii).(b) Calculation As an alternative to the determination method described in Item (a), the minimum size of an earthing c

27、onductor required may be determined by calculation provided that accurate information is obtained on the value of the prospective fault current, the disconnecting time of the protective device, and conductor and insulation characteristics.NOTE: A suitable equation for the calculation of conductor si

28、zes under fault current conditions is given in Clause 5.6.7.4.3.(c) Main earthing conductor In general, the minimum size of the main earthing conductor shall be determined in accordance with Item (a) and Table 5.1 in relation to the cross-sectional area of the largestactive conductor of the consumer

29、s mains.The size of the main earthing conductor need not be determined in relation to the size of the largest active conductor of the consumers mains under the following conditions:(i) Where double insulation is maintained between the point of supply and the load terminals of the protective devices

30、on the submains and final subcircuits outgoing from the main switchboard, the minimum size of the main earthing conductor may be determined in relation to the cross-sectional area of the largest active conductor of the largest outgoing submain or final subcircuit.(ii) Where the cross-sectional area

31、of the consumers mains is larger than that required to carry the maximum demand of the installation because of voltage-drop limitations, the minimum size of the main earthing conductor may be determined in relation to the cross-sectional area of the minimum cable size required to carry the maximum d

32、emand.In any case, the cross-sectional area of a copper main earthing conductor shall be not less than4mm2.(d) Aerial earthing conductor The minimum size of an earthing conductor installed as an aerial conductor shall be determined in accordance with Item (a) and Table 5.1 provided that the cross-sectional area of the earthing conductor so determined shall be not less than the size specified in Cla