In addition to heavy loading of transmission lines, integration of volatile renewable energy to power system can cause voltage stability problem. This paper proposes risk based optimum power flow (OPF) that decides not only generator power dispatch, but also reserve power allocation and operations of variable shunt reactors (VSR) and capacitor banks (CB) considering N-1 contingencies and RE integration. The proposed method ensures the voltage stability for both normal and contingency condition, including system security and RE constraint. Effectiveness of the proposed method is tested on the IEEE 57 bus test system.