This paper presents a generic framework for the modeling of energy systems comprising multiple-energy carriers, such as electricity, heat, gas, biomass, etc. The modeling framework is based on the so-called energy hub approach. The core idea of the energy hub is the definition of a conversion matrix capable of describing the interactions of production, delivery, and consumption in multiple-energy carrier systems. Based on the energy hub concept a broad spectrum of modeling extensions and applications is presented, such as a multiple-energy carrier optimal power flow, risk management and investment analysis tools, agent-based control schemes for decentralized generation units as well as the possibility to analyze the influence of plug-in hybrid electric vehicles (PHEVs) on future energy systems. The paper is concluded with a section presenting the key benefits of the energy hub modeling framework, followed by a discussion on the main design principles generality, scalability, and modularity as well as a discussion on the possibility to follow top-down or bottom-up modeling strategies.

Online condition monitoring and diagnosis are being utilized more and more for increasing the reliability and availability of technical systems and to reduce their maintenance costs. Today's model-based diagnosis (MBD) tools are able to detect and identify incipient and sudden faults very reliably. For application to cost-sensitive equipment, such as high-voltage circuit breakers (HVCBs), however, the presently available MBD systems are not feasible for economic reasons. In this paper, a novel combination of the model-based with the case-based approach to condition diagnosis is presented, which can be implemented on a low-cost computer and which offers satisfactory performance. The technique is divided into two parts: (1) preparation and (2) diagnosis. The diagnosis part can be executed on an inexpensive low-performance computer. Successful tests on real HVCBs confirm the usefulness of this new approach to condition diagnosis.