Publication
This thesis analyses and models the vulnerability of the electricity power supply under extreme weather conditions. The system under study is the electric supply system that includes major power plants to main load centers. Extreme weather conditions can cause common mode contingencies (CMCs) of overhead power lines, which endanger the security of electricity supply. Planning and operation of transmission systems are subject to N-1 criterion, which requires that all single failures of network elements do not cause a breach of safety limits. This criterion does not guarantee the security of electricity supply at the time of extreme weather conditions. The objective of this research is to identify critical and plausible CMCs, taking into account space-time correlations of extreme weather conditions and possible states of the network. The most vulnerable zones are focused on to determine appropriate countermeasures for reducing vulnerability. In the past, extreme weather events have caused major disruptions. For example, the blackout in New York in 1977 was initiated by three impacts of lightning on high voltage lines. In 1999, hurricane Lothar caused damage to power grids in several countries, leaving hundreds of thousands of people in darkness. These examples demonstrate the vulnerability of power systems to CMCs. Current transmission networks are expected to undergo significant changes in response to developments such as increases in consumption and newly installed capacity. These changes provide an opportunity to strengthen the security of electricity supply in the perspective of extreme weather conditions and even improve the resilience of electric supply systems. The use of the proposed methodology allows reducing the level of vulnerability by reinforcing only few points or change of the topology of the network. Faced with uncertainties about the evolution of networks and plausible extreme weather conditions, a methodology based on scenarios has been selected. The methodology allows the modeler to reproduce the complexity of the problem while still encouraging the learning process. The core of the methodology is founded on a scenario of electric supply systems and a scenario of extreme weather events. The first scenario includes three models: electric, geographic, and reliability. The electric model comprises components of the network compatible with load flow calculations. The geographic model contains a representation of each power line in a geographic information system, and each of these lines is divided into segments that are associated with a reliability model. The reliability model evaluates failure rates related to exposure to extreme weather conditions. Scenarios of extreme weather events are built on data from weather stations or by numerical simulations implemented in a geographic information system. A vulnerability level index is calculated on the basis of probability and severity indices of a priori possible CMCs. These probabilit