Answer / cnu

Basically a device is earthed to avoid any stray
circulating current that appear on the body of the device
operating with an AC supply.

since AC creates an alternating flux. this changes in flux
induces stray currents in the metallic body of the devices.

When coming to DC, since it is a constant voltage it does
not produce flux change to induce any currents so earthing
is not required for a DC battery.

Answer / prasoon

In a HV Sub station, 220 Volt system is not earthed to
avoid mal operation of DC controlled electrical elemnets in
case of a earth fault.

50 Volt system is earthed (-ve). This is done as 50 volt
system is used for electronic circuits where -ve voltage is
required to opearate npn transistors.

Answer / aamod tripathi

To avoid circulating current in DC system.

Answer / owais chaudhri

b/c there is already availabe zero potential in batry
(ie -ve terminal).

Answer / kanth

there is no need of earthing fo Dc systems
and in AC only earthing is needed
bcoz power generated from generators and ttransfer from
transformers ,so transrormers neutral's earthing has done
(in star-star or delta-star trafo)so phase currents goes
directly though earth or in neutral as a returned path to
transformer.
so we r using neutral for return path and earthing for
safety

Due to ferranti effect which power increases at the receiving end?active power or reactive power?

5 Answers  

If the rotor pf of a 3 phase induction motor is .866, then what is the phase displacement between stator and rotor magnetic field 1)30,2)120,3)150,4)90 please justify....

2 Answers   GATE,

132 KV TRFO BUSHING CT BURNT WHEN A 6.6KV HAS BEEN APPLIED TO IT .WHY .ANY REASON ?

3 Answers   vguard,

why root three is used and how its comes in three phase power system?

1 Answers   IEEE,

how is working bearing heater?

0 Answers   ONGC,

what is the use of power factor ? where its applicable ?

4 Answers  

how calculate the current faut level

2 Answers   ABB,

In a Circuit how the MCB and Fuse ratings are calculated. And shall the fuse follws the MCB or it is otherwise?

16 Answers   Emerson, HCL, Thirumalai Chemicals,

When a single pase capacitor run motor- run on 230vac and Case(1)run with 8 Mfd 250 vac.capacitor , Case( 2) run with 8 Mfd 400vac capacitor. What is difference between both case regarding power ,efficiency etc?

0 Answers  

Why all voltage level are multiples of 11, like 220V, 440V, 1100V instead of 200V, 400V, 1000V?

9 Answers   Indian School of Mines,

How to find out freqency in Ac and Dc and also how u control it

2 Answers   MacLellan,

Find defination of KVA convert in to KW.

4 Answers   ABB,