I S : 3 0 4 3 . 1987 6.1.2 It is also recognized that, in practice, a system may be an admixture of type for the pur poses of this code, earthing systems are designated as follows: a) TN-S System {for 240 Vsingle phase domestic! commercial supply ) — Systems where there are separate neutral and protective con ductors throughout the system. A system where the metallic path between the installation and the source of energy is the sheath and armouring of the supply cable ( see Fig. 2 ). b) Indian TN-S System {for 415 V three-phase domestic commercial supply ) — An independ ent earth electrode within the consumer's premises is necessary ( See Fig. 3 ). Indian TNC-System—The neutral and pro c) tective functons are combined in a single
couductor throughout the system ( for example earthed concentric wiring (see Fig. 4 ). d) TN-C-S Systtm — The neutral and protec tive functions are combined in a single conductor but only in part of the system ( set Fig 5 ). e) T-TN-S System {for 6-6\ll kV thtee-phase bulk supply ) — The consumers installation, a TN-S system receiving power at a captive substation through a delta connected transformer primary ( see Fig. 6 ). f) TT System {for 415V three-phase industrial supply ) — Same as 6.1.1 (b) ( see Fig 7. ). g) IT System Fig. 8 ).
Same as 6.1.1
(c) ( see
SOURCE OF ENERGY -L2 -L3 -N •PE SOURCE EARTH
f
EXPOSED CONOUCTIVE PART 'CONSUMER INSTALLATION
{ I \
EQUIPMENT IN INSTALLATION
NOTE — The protective conductor ( FE ) is the metallic covering ( armour or load sheath of the cable supplying the installation or a separate conductor ). . AH exposed conductive parts of an installation are connected to this protective conductor via main earthing terminal of the installation. Fio. 2
TN-S
SYSTEM SEPARATE NEUTRAL AND PROTECTIVE CONDUCTORS THROUGHOUT THE SYSTEM,
230V SIMPLE PHASE. DOMESTIC/COMMERCIAL SUPPLY FOR 3~TN-S ( >SM FIO. 3 ) SOURCE OF ENERGY _ 1
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415 V Three phase Domestic/Commercial supply having 3 <~ and 1 r~ loads. All exposed conductive parts of the installation are connected to protective conductor via the main earthing terminal'of the installation. An independent earth electrode within the consumer's permises is necessary. FIO. 3
INDIAN TN-S SYSTEM
12