This research is divided into theoretical and practical sections. The theoretical section clarifies the importance of electrical interconnection in frequency stability, which reports the most important technical and economic benefits achieved for the electrical network stability in general and frequency stability by the (EIJLLPST) project. The practical section will introducea number of simulation on the Syrian network for the year 2011 using the PSS/E, and rely on this program after comparing the results with the results of real situations, through the application of several incidents of blackout occurred in the Syrian network (and archived of frequency when they occur) Where the experienced of this research was focus on the importance of the spinning reserve, electrical interconnection and the separation of electrical loads using underfrequency rely To maintain the stability of electrical grid frequency in Syria ,and to avoid falling into undesirable values of frequency.