Radiation plays an important role in the energy transfer of internal fault arc in enclosed switchgears

which is closely related to the pressure rise and energy balance caused by the fault arcing. Consequently

the radiation characteristics of the air fault arc in a sealed cavity were measured by coupling a thermopile with flat spectral sensitivity and a photomultiplier with ultra fast response. The influences of different testing conditions on the arc radiated energy

Joule heating as well as the fraction of radiation to Joule heating were analyzed quantitatively. The results show that

with the increase of the arc current

filling pressure

or electrode gap

the energy of all arc radiations tends to rise. Regarding the fraction of radiation on input Joule heating

the fraction in the initial arcing process is seriously affected by the arc current while it almost has no relation to arc current in the final arcing period. The increase of the filling pressure gives a reduction in the fraction due to the fact that the growth rate of arc voltage exceeds that of arc radiation. Besides

the increase of the electrode gap gives a rise in the fraction that is slower than linear.