In security assessment of power systems, presently, the deterministic approach is the most widely used method. However, in the current competitive environment, the drawbacks become salient; hence security assessment based on the concept of risk is required. Risk assessment is an approach that quantitatively captures the factors that determine security level, namely likelihood and the severity of events. Risk index is used to quantify the degree of risk of the given operating condition. This paper presents risk based static security assessment on a practical interconnected power system at various loading condition using a risk index. The result captures the uncertainty in the occurrence of contingency and the variation of risk index as the load changes.