Risk Assessment Methodology for Operations applied to the Portuguese Transmission System - the Probabilistic Model

摘要

Nowadays most of the transmission systems' operating conditions are more stressed due to the introduction of a competitive environment in the power system industry and the regulatory changes causing the unbundling of generation, transmission and distribution, the environmental concerns, which limit the construction of new transmission lines and generation capacity, and the strong incentives to the generation through renewable energy sources. The use of methodologies that take advantage of the actual real-time conditions in combination with past knowledge is extremely interesting in the system operation's environment, because it gives a more accurate overview to the control room operators allowing them to prevent harmful situations. Obviously, this type of methodologies has received even more interest after the large disturbances which occurred in recent years, because they increase the awareness about the risk of unpredictable disturbances. Recent international data show that the frequency of large blackouts has increased and also that simple initiating faults can have very severe consequences. References [1-4] present a few examples of severe disturbances, which occurred in the recent past. Despite all the efforts being done regarding supervisory practices, operation strategies and protection and control systems' improvements, it is technically and economically impossible to eradicate major disturbances and blackouts. They will be a permanent threat to the electrical power systems, making incident analysis a crucial activity. The risk assessment methodology that is being developed is composed of two parts: probability of occurrence and severity for all contingencies under analysis. This paper aims to present the complete probabilistic model used to calculate the probability of occurrence of contingencies, including overhead lines, transformers and busbars. N-2 common cause contingencies are also considered for faults caused by lightning and forest fires.