remote control equipment - Indian Railways Institute of Electrical ...
remote control equipment - Indian Railways Institute of Electrical ...
remote control equipment - Indian Railways Institute of Electrical ...
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etween live parts and different potentials (phase clearance) in order to prevent flashovers.<br />
Safety clearance also called as sectional clearance is defined as the minimum distance<br />
required between unscreened live conductor and the limits <strong>of</strong> a work section. Safety clearances<br />
are required for safety <strong>of</strong> personnel in inspection, operation and maintenance. Minimum<br />
electrical clearances for outdoor switchgear as stipulated in IS 3072.<br />
Voltage<br />
rating<br />
Impulse<br />
withstand<br />
level<br />
Minimum<br />
ciearanee<br />
to earth<br />
Minimum<br />
clearance<br />
between<br />
phases<br />
Min clearance<br />
from any point<br />
where they may be<br />
reauired to stand<br />
to the nearest<br />
unscreened<br />
conductors<br />
air(section<br />
safety clearance)<br />
kV (rms) kV (Peak) (mm) (mm) (mm)<br />
72.5 325 630 750 3230<br />
350 675 810 3270<br />
123 450 920 1065 3520<br />
550 1150 1350 3750<br />
145 550 1150 1350 3750<br />
650 1380 1600 3980<br />
245 875 1800 2000 4400<br />
900 1900 2300 4550<br />
1050 2300 2700 4900<br />
Figures underlined have been adopted in RDSO’s specifications.<br />
4.11 EARTHING<br />
4.11.1 Earthing system is <strong>of</strong> utmost importance for the purpose <strong>of</strong> protection in both<br />
electricity supply and utilisation. The primary need <strong>of</strong> earthing is that in the event <strong>of</strong> fault<br />
sufficient current shall flow through the fault path so as to operated the protective gear and<br />
preventing dangerous potential rise on parts <strong>of</strong> electrical <strong>equipment</strong>s that are not alive. It is<br />
therefor, essential that earthing system shall have sufficient cross section and low resistance<br />
to provide a path for the traction current. Earthing also provide the return path for the<br />
traction current, ensures that non current carrying parts such as <strong>equipment</strong> frames, fencing<br />
and structures are always at ground potential even after the failure <strong>of</strong> the insulation.<br />
Earthing also helps to reduce the effect <strong>of</strong> induced voltage in adjacent communication<br />
circuits.<br />
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