Security Assessment in the Operation of Longitudinal Power Systems

In the last decade modern control centers with advanced security functions have been installed in several countries. However most security applications have been based on steady state calculations, mainly because for those systems typical operating problems can be assessed using steady state analyses. Many power systems around the world, specially in developing countries, are characterized by a weak longitudinal structure. For these systems operating problems and system security are closely related to system configuration. The paper presents main characteristics of longitudinal power systems and common operating problems are described and illustrated. The examples included in the paper are based on simulations using real longitudinal power systems. For these systems dynamic security analyses are required to assess system performance. Main areas of study are voltage control , transient stability and frequency dynamics. Basic simulation tools are described and operating strategies presented.