Sensor nodes are tiny devices, with less computational power and memory capacity. For secure communication, the secret keys must be built into the nodes before deployment. Distribution of keys among the sensor nodes is a challenging task. Number of sensor nodes are usually much higher than the number of keys available. In this paper we use Steiner Triple system (STS) which is a combinatorial design to distribute the keys among the sensor nodes. As the keys are built into the nodes, no path key establishment phase is required for secure communication. Hence nodes can communicate using the built in secret keys. Thus, a faster communication is achieved. However, STS is not an appropriate candidate for large networks, where sensors are not within the communication range of each other. To overcome this we propose a cluster based key predistribution using Steiner Triple System. We evaluated the resiliency of our proposed system and found to have a better resiliency.Using dummy node concept the scalability of network can be increase.