本手冊是2013年由國際銅業(yè)協(xié)會東南亞區(qū)馬來西亞電氣專家，結(jié)合馬來西亞當(dāng)?shù)亟ㄖ姎庖?guī)范和IEC標(biāo)準(zhǔn)編寫的，是對低壓電氣布線的指導(dǎo)說明。手冊只有英文版，僅供大家學(xué)習(xí)參考。
版權(quán)歸國際銅業(yè)協(xié)會所有
說明：本手冊共分為8個(gè)大章節(jié)。本文是第四個(gè)大章節(jié)之4.1、4.2：
4 Earthing System
4.1 Earth Systems in an Installation
Earthing systems in an electrical installation can be identified as follows:
a.
Electrical system earth; defined in Part 1; Section 312 and Part 5-54 (which will be covered in this handbook).
b.
Equipotential earth (for protection) covered in Part 4-41, Part 4-44 and 5-54 (which will not dealt with in this handbook).
c.
Equipotential earth (for EMC) covered in IEC61000-5-2 “Electromagnetic compatibility (EMC)”; Part 5: Installation and mitigation guidelines – Section 2: Earthing and cabling” (which will not dealt with in this handbook).
4.2 Earthing System Defined in IEC 60364; Part 1, 312
System earth in an installation is defined in Part 1; 312 1st
From the above, three main earthing system types can be identified.
Note: If isolating transformer (iTx) has primary of Δ then TN-C system is used. If iTx has primary of Y, then TN-S system is used.
a.
TT System – where the source neutral is earthed and the frame of the load is independently earthed. TT system has 4 cables comprising 3P + N. TT system requires independent earth at both ends of the connections.
b.
TN System – where the source neutral is earthed and the frame of the final load is earthed through a protective conductor (PE) which connects back to “source” earth. TN has two sub systems:
(i) TN-C System – where the frame earth is linked via the neutral to the source earth,creating a combined PE and Neutral (PEN) conductor. TN-C system has 4 cables comprising 3P + PEN.
(ii) TN-S System – where the frame earth is connected through a separate ‘earth continuity conductor’ called the ‘Protective Earth’ or PE. TN-S system has 5 cables comprising 3P + N + PE.
TN system requires only one earth point at source.
c.
IT System – where the source neutral is unearthed and the frame of the final load is independently earthed. IT system has 3 cables comprising 3P. An earth point would be required at termination end.
Note: “IN” system is topographically not possible (frame earthing linked back to source neutral earth is not possible when source neutral is unearthed). An “IN” system would in effect be a completely unearthed installation and IS NOT ALLOWED for safety reasons.
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