translate : 

In a concentric spherical electrode system, the outer radius is 15cm, the perforation of the insulator between the spheres
since its resistance is 90 kV / cm,
a) Obtain the equation for the breakdown voltage. 
b) Since 300kV is applied between the electrodes, r1 (inner radius) can be taken to prevent piercing of the system.
what range are the values? 

Bir e merkezli kresel elektrot sisteminde d yarap 15cm, kreler arasndaki yaltkann delinme dayanm 90 kV/cm olduuna gre, a) Delinme geriliminin denklemini elde ediniz. b) Elektrotlar arasna 300kV uygulandna gre sistemin delinmemesi iin ri' in(i yarap) alabilecei deerler hangi aralktadr? c) Sistemin dayanabilecei maksimum gerilim deeri ka kV'tur?.