In general, electrical power stations are constructed far from load regions because of pollution problems and using long transmission lines for high voltage. Also, the networks are connected with other networks for the purpose of transmission and to return supply the electrical energy. As a result, and because of other factors, such as sudden change in the load, oscillations occur in electrical systems, some time, these oscillations become strong and if they continue they will affect stability system.
This work is devoted to the study of the stability of the Iraqi National Grid when subjected to various operating conditions (fault: large and small load changes). Load changes produce low frequency oscillations which represent an unstable phenomenon, it is important that these oscillations are damped. Supplementary controllers (power system stabilizers, PSS type 2A) may be added to the generators controllers to improve the damping of these oscillations. Part of the work will be focused on studying the oscillation in the generators torque angles of the Iraqi Grid. Three cases of disturbances are investigated; the first is load changing, the second is Single-Line-Ground fault, and the third is three phase fault at the generator terminals.