Next step in application of transmission and distribution system reliability analysis

In the paper the two approaches, models and tools for the electric power system reliability assessment on HL II level: NIEZ - for reliability assessment of transmission and/or distribution systems, and TRELSS (transmission reliability evaluation of large scale systems) - for composite (generation and transmission) system reliability evaluation, are described. Their application to the Polish electric power transmission system reliability analysis and assessment as well as usefulness of obtained results for both planning and management purposes are also presented. In Warsaw University of Technology the special overlay computer program for TRELSS, named "SYSTEM TRELSS - PW" was created. This program is user-friendly tool, adjusted for Polish condition and data, which allows to do the next step in application of transmission system reliability analysis. The main features of "SYSTEM TRELSS - PW" are also presented in the paper.