Affordable Cable System Reliability and Life Extension Strategy
Today, there is increased pressure for electric distribution cooperatives to maintain system reliability without increasing membership costs. This challenge is further compounded by the need to maximize existing legacy infrastructure. While membership reliability is a key consideration, a static economy, a commitment to a lower carbon footprint and the need for rate stability are also key factors that translate into increased operating costs. Many consider age to be the silent killer of America's critical infrastructure. The large fleets of equipment deployed by electric utilities and limited real-time monitoring makes it nearly impossible to know the duty each specific piece of equipment has experienced, thus age alone is used as the main determinant of remaining life. The economic and staffing requirements to replace these aged fleets based solely on in-service life is untenable. The need to find a lean approach to better address this challenge has lead to new technologies that provide detailed information about the equipment's true health or condition to allow the right measure of asset rehabilitation, replacement or extended deployment using actual condition assessment. There are millions of miles underground power distribution systems in service today that are operating beyond the original accounting defined depreciation life and failing at an ever increasing rate. Until recently, management of these underground assets was particularly challenging because once put into service, their concealment prevents visible inspection. A new cable life extension process is revolutionizing the industry by providing a means to field assess, rehabilitate and then certify cable systems to like new status. The proven assessment technology has certified more than 90,000 underground cable systems around the world and has shown that over 75% of aged assets still perform as well or better today as they did when they were first installed, decades ago. The Federal Energy Regulatory Commission's ("FERC") decision to allow capitalization of this new cable life extension technology is prompting many utilities and electric cooperatives coast to coast to reduce cable replacement budgets and make a positive impact on membership costs. These forward looking utilities have experienced extended capital reach, lowered operating and maintenance (O&M) expenditures, efficient resource utilization, minimal property intrusion and a dramatic real-time improvement in cable system reliability.
Uma Discussão sobre a Análise de Descargas Parciais para o Prognóstico de Falhas de Cabos Isolados e Gerenciamento de Ativos
Resumo—Este trabalho apresenta uma criteriosa revisão bibliográfica e uma discussão sobre a avaliação do estado da isolação de cabos isolados de média e alta tensão baseada na análise de descargas parciais, além da formulação de planos de manutenção e de gerenciamento de ativos baseados neste mesmo fenômeno. São apresentados os possíveis métodos de detecção de descarga parciais e os sensores adequados para cada aplicação, além de métodos para a estimativa do tempo de vida restante de cabos isolados empregando-se o valor da descarga aparente medido. Por fim, são mostrados diferentes métodos e sistemas que aplicam as descargas parciais como um parâmetro de auxilio no planejamento da atividade de manutenção preditiva e gerenciamento de ativos.
Computational fluid dynamics as a development tool for rotary blood pumps.
Computational fluid dynamics (CFD) is beginning to significantly impact the development of biomedical devices, in particular rotary cardiac assist devices. The University of Pittsburgh's McGowan Center for Artificial Organ Development has extensively used CFD as the primary tool to analyze and design a novel axial flow blood pump having a magnetically suspended rotor. The blood-contacting surfaces of the pump were developed using a design strategy based on CFD that involved closely coupling a Navier-Stokes solver to a parameterized geometry modeler and advanced mesh movement techniques. CFD-based blood damage models for shear-induced hemolysis as well as surrogate functions describing thrombosis potential were employed to help guide design improvements. This CFD-based design approach resulted in the timely development of a pump subjected to multiple geometric refinements without building expensive physical prototypes for each design iteration. A physical prototype of the final improved pump was fabricated and experimentally analyzed using particle imaging flow visualization. The CFD predicted results correlated well with the experimental data including pressure-flow (H-Q) performance and specific flow field features. It is estimated that the present CFD-based design approach shortened the overall design time frame from an order of years to months.