The fast growth and development in power system has made the system becoming heavily stressed and more complex from day to days. This is happened due to the several reasons such increased of load in the transmission lines and also the difficulties in constructing new transmission system as well as inconvenience in building up new generating plant near the load centers. These incidents may lead to the power system problems such as voltage instability problem or voltage collapse and loss maximization. Generally, power system is an electrical network that contains several components such as generators, transmission lines, loads, and also voltage controller. Electric utility power system originates in the power plant or generation; it is then transmitted to the loads by the transmission lines .
As stated earlier, one of the power system problems is voltage instability or voltage collapse problem. Referring to , voltage instability or voltage collapse is dynamic process; It can be defined as the absence of voltage stability, resulted from the decreased of progressive voltage. Voltage magnitudes fall gradually in the early stage of voltage collapse. This condition might be temporary voltage recovery due to the voltage control action; however, the voltages soon drop to a very low level. Voltage instability or voltage collapse has become serious problem in power system and recently, active research subject
attracting investigators from the field of power engineering. A study on voltage collapse mechanism  shows that there is an iterative reaction of voltage drop between the system network and dynamic load that can lead to the voltage collapse. This dynamic phenomenon and incident of voltage collapse is then analyzed on the simple power system model with included synchronous motor. Many published papers have discussed and investigate the voltage stability which is related to the voltage collapse problem [4-6].
There are several techniques for voltage control technique in order to avoid voltage collapse such as reactive power scheduling and transformer tap changer setting. Both techniques involved the optimization process. Nowadays, many researchers have applied the artificial intelligence and optimization technique in order to solve the power system problem. Referring [7-13]; these optimization techniques are linear programming, non-linear programming, Tabu Search, Genetic Algorithm (GA), Evolutionary Programming (EP), and Simulated Annealing (SA). Each optimization technique carried different ways of the optimization.
In this thesis, Evolutionary Programming (EP) technique is used to optimize the reactive power scheduling and transformer tap changer setting for voltage controlling in order to improve and maximize the minimum voltage experience in the power system by considering multi-contingency conditions.
1.2 PROBLEM STATEMENT
Generally, power system may experience several problems such as voltage minimization...