Answer / will

Lightning occurs when the negative charged cloud and
positive charged clouds hit together.A flash occurs and it
tries to conduct through the atmosphere.
Protection through lightning is achieved by installting the
lightning arrestors at the top of the high rise buildings
and grounded separately.The grounding shall be separated
from the normal ground grid in the petrochemical plants.
We need not to select the height for the spike , when the
building or the equipment is proted by lightning arrestor ,
the lightning arrestor will take care, The surge will be
arrested by the lightning arrestor and current will
directly flow to the ground without causing any damage to
the equipment(Substation) or the high rise buildings.

Answer / bala

when the atmosperic electrical potential is sufficently
high to break down the air's normal insulation level's
600kv/m. cloud to ground lighning flas occur's.

Answer / nazeer

positive charged cloud takes ground as negative in this way
it discharge its power lightning occur.it is protected by
providing lighting arrestor. Area which come under the
diameter of 45 degree from top height of lightning arrestor
will be protected by the way it should earthed at least by
70sqmm cu cable to separate earth pit which resistance
should be below 5 ohms

Answer / shivdutt tyagi

Lightning is a Ntural phenomenon. when thudercloudformed,
charge separation takes place. a step leader move forward
toward the ground if the suffiecient elctrical present
which is highher the breakdown value normal requred. and
leader move as a branch in path. when it aproaches the
ground level the grounded object having suficient field
meet to leader and charge back flow to the cloud and
neutralize there and a hug ecurrent flow called return
stroke. this explin lightning phenomenon

in the exciter the power is feeded from battry or control or whatever.and we need it in the generators for the stating . do we need it in the shutdown also?i mean the exciter>

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