why neutral and earth should not be connected on 3 phase
440v/50c/s supply at consumer side. where as on
25kv/ac/50c/s railway traction substation neutral and earth
will be connected and track at substation. and track will
act as neutral and earth. Reasons for this is needed
urgently
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Answer Posted / nmr
IF ALL CONSUMERS EARTH ARE CONNECTED TO NEUTRAL AT EACH
CONSUMER POINT, ALL THE EARTH ELECTRODES RESISTANCES ARE
BECOMES PARALLEL ALONG WITH TRANSFORMER SECONDARY NEUTRAL-
EARTH ELECTRODES. HENCE 1/R= 1/R1+1/R2+1/R3+1/R4 ETC.,
THERE EFFECTIVE RESISTANCE IS BECOMES VERY VERY LOW. IF A
30 KVA TRANSFORMER IS THERE. THE CURRENT IL/IPHSE =
30,000/440*1.732 = 40.0 AMPS (WITH UNITY PF) THIS CCURRENT
WILL PASS THROUGH EARTHS ELECTRODES(BECAUSE ALL EARTH
RESISTANCES ARE PARALLEL AND NET RESISTANCE WILL BECOME
LESSER THAN THAT OF NEUTRAL)SO STEP POTNTIAL WILL RAISE
CAUSES ELECTRIC SHOCK TO THE PEOPLE WALKING AT NEAR
TFP/PANNEL BOARDS. IN TRACTION SUBSTATION A EARTH MAT WILL
BE PROVIDED IN THE YARD TO REDUCE THE STEP VOLTAGE NOT TO
GET SHOCK BY THE PEOPLE. OK
NMR/email; bapdada1812@gmail.com electrical engineer
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