DETERMINA TION OF STATIC LOADABILITY LIMIT OF IRAN POWER NETWORK UNDER THE CONSTRAINT OF VOLTAGE STABILITY

Security is one of the main aspects of electric Power Systems in planing and operation phases. Conventionaly, line overloading and voltage magnitude and transient stability are considered as security indices for assessment of system security and performance. In this paper, a new approach based on loadability limit is proposed for assessment of system security. The new index is system loadability limit with respect to voltage stability constraint. In this paper, loadability limit is regarded as the maximum load which can be imposed on the system without lossing its voltage stability. As a result of this new index voltage security margin (VS" which is the difference of system loadability limit with current operating load of the system, can be defined. In this paper, system loadability limit is evaluated by the nonlinear optimization programming in which system total load is modeled. for maximizing under the constraint of power flow equations.