RATING OF LIGHTENING ARRESTER FOR 11 KV LINE IS 9 KV BUT WE
KNOW THAT LIGHTENING ARRESTER IS USED FOR OVER VOLTAGE
PROTECTION SO WHY NOT THE RATING OF LIGHTENING ARRESTER BE
MORE THAN 11KV ???????????????//

Answer Posted / h r jadhav

when we use ac line having system line voltage 11kv,in
this case phase voltage [phase to neutral which is earthed}
is 6.351 kv. lightening arrester is connected between phase
and neutral. lightening arester are nothing but the voltage
dependant resistors which act as insulator up to not only
the phase volatage ie 6.351 kv rms but ac peak voltage
reaches to 6.351 rms x root of 2 ie 1.414=8.98 kv. for
normal operation of system. thus the L A s are rated for
normal voltages 9 kv and discharge current generaly 10 kamp.
when ever voltage surges occures due to lightenig or either
by system abnormabilty,L A becomes for a instance as a
conductor provides path to surge voltages and prevents
failure of insulation leveles of equipment of system

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