Wireless sensor network is an emerging research field. It has gained a lot of attention from industry and academia. Mainly it is used for monitoring and data aggregation from the field. Data is most important in this process as it gives us the useful information. There are lots of techniques to gather data from the field. These techniques or can be said protocols must be energy efficient as this is a main constraint for the sensor nodes having limited battery. Lot of protocols have been designed for this process. LEACH (Low Energy Adaptive Clustering Hierarchy) is a basic protocol that uses clustering. It has significantly increased the life-time of network as compared to old flat protocols. There are various advancements in LEACH. Heterogeneity is also an important matter in sensor network as all the nodes do not lose energy uniformly. SEP (Stable Election Protocol) is a heterogeneous aware protocol based on LEACH and increases the lifetime of the network. ESEP (Extended Stable Election Protocol) is an extended version of the SEP that adds more heterogeneity by adding one more type of nodes. In heterogeneous aware protocols, each type of node has different amount of initial energy. There is a problem that when nodes left with the same amount of residual energy, the probability remains according to initial energy. So a changed ESEP protocol has been proposed. Simulation has been done in MATLAB and proposed protocol gives better performance in terms of first node dies and total number of packets delivered.