SECTION 5 EARTHING ARRANGEMENTS AND EARTHING
CONDUCTORS
北京平面设计培训第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 1.
5.2 EARTHING ARRANGEMENTS 接地布置
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5.2.1 General 概述
Earthing arrangements may be ud jointly or parately for protective or functional purpos, according to the requirements of the electrical installation.
5.2.2 For protective purpos
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Earthing arrangements for protective purpos shall be comprid of protective earthing conductors us
ed 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 vicinity.
5.2.3 For functional purpos 出于功能目的
Earthing arrangements for functional purpos shall be comprid 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 earth’ 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 purpos
Where earthing for combined protective and functional purpos is required, the requirements for protective purpos (e Clau 5.2.2) shall prevail.
5.2.5 Selection and installation 选择和安装
The lection 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 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 stress; and
(c) it is adequately robust or has additional mechanical protection appropriate to the assd conditions of external influence in accordance with Clau 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 galvanic action.
十一月 英文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 Clau 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 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 requirements may be ud.
5.4 EARTHING REQUIREMENTS 接地要求
5.4.1 General 概述
The expod conductive parts of electrical equipment shall be earthed where the electrical equipment is —
saturn(a) installed or might operate in an earthed situation; or
(b) not installed in an earthed situation but any expod conductive part of the electrical equipment is electrically continuous with conductive material which is located in an earthed situation.
NOTE: The term expod 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 required to remove the covers of the enclosure.
(b) Conductive parts within electrical equipment where the parts cannot be touched in normal u and movement of the electrical equipment due to its configuration and size, e.g. some types of washing machines.
(c) Conductive parts which are parated from 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 are supported and fixed.
NOTE: Only single pha connections shown for clarity.
FIGURE 5.1 MULTIPLE EARTHED NEUTRAL (MEN) SYSTEM OF EARTHING—MEN LINK AT CUSTOMER’S MAIN SWITCHBOARD
NOTE: Distribution as Figure 5.1
FIGURE 5.2 MULTIPLE EARTHED NEUTRAL (MEN) SYSTEM OF EARTHING—MEN LINK REMOTE FROM CUSTO MER’S MAIN SWITCHBOARD
5.4.2 Connection of electrical equipment to earth 电气设备接地连接
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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 medium 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 conductor 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 associated with any particular circuit depends on the type and rating of the protective device and the impedance of the live conductors that compri 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 of Clau 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 determined 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 5.1
in relation to the cross-ctional area of the largest active conductor supplying 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 multipha circuit compri different size conductors, the earthing conductor shall be determined in relation to the cross-ctional area of the largest active conductor to be protected.
(ii) Where the active conductor compris a number of conductors, connected in parallel, the earthing conductor shall be determined in relation to the summation of the cross-ctional areas of the individual conductors forming the largest active conductor to be protected.
Where the summation of cross-ctional 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 MINIMUM COPPER EARTHING CONDUCTOR SIZE
* The earthing conductors may be ud only where incorprated in a multicore cable or flexible cord, other than a lift traveling cable, in accordance with Clau 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 conductor 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 sizes under fault current conditions is given in Clau 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-ctional area of the largest
active conductor of the consumers 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:
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(i) Where double insulation is maintained between the point of supply and the load terminals of the protective devices 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-ctional area of the largest active conductor of the largest outgoing submain or final subcircuit.
(ii) Where the cross-ctional area of the consumers mains is larger than that required to carry the maximum demand of the installation becau of voltage-drop limitations, the minimum size of the main earthing conductor may be determined in relation to the cross-ctional area of the minimum cable size required to carry the maximum demand.
In any ca, the cross-ctional area of a copper main earthing conductor shall be not less than4mm2.
steal过去式(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-ctional area of the earthing conductor so determined shall be not less than the size specified in Clau 3.12.2.2 and Table 3.9 according to the type of conductor and length of span.
(e) Earthing conductors in cables or flexible cords The minimum size of an earthing conductor in the
新年快乐英文form of a cable or flexible cord shall be determined in accordance with Item (a) and Table 5.1, and the cross-ctional area of the earthing conductor so determined shall comply with the following additional requirements appropriate to the type of cable or cord:
2013年福建高考作文
NOTE: AS/NZS 3191 precludes the u of aluminium conductors in flexible cords.
(i) Single-core cable or flexible cord The minimum size of a copper earthing conductor in the form of a single-core insulated cable or flexible cord shall be 2.5 mm2.
This requirement need not apply where connections in a multicore cable require a short length of single-core insulated earthing conductor to be unenclod, in which ca the earthing conductor size may be not less than 1 mm2 in accordance with Item (e)(ii).
(ii) Multicore cable The minimum size of an earthing conductor incorporated with associated live conductors in a sheathed multicore cable shall be 1 mm2.
