Electrical power system in buildings with higher risk for seismic event

The earthquake can cause serious problems to the functional reliability and continuity of supply of electrical power systems. The paper discusses the need to study the requirements for the design and installation of electrical power systems in buildings subject to seismic hazard. Therefore, it is necessary to recommend mechanical and electrical criteria for the design and the installation, to be graduated according to building occupancy categories (as hospitals, strategic buildings). At least three levels of performances are definable for equipment: -the resistance to the seismic stress, - the guarantee of duty after the earthquake, - the guarantee of duty during and after the earthquake. Basically, the criteria relative to the installation of the electrical equipment are an appropriate extension of those general static ones for non structural components. Their consideration is essential for the settlement of the design criteria, which, as far as the configuration and the size of the electrical power system are concerned, aim at limiting the same installation problems. A special power distribution, "brush-distribution", is suitable for the strategic buildings with higher risk for seismic event. This distribution suggests locating, as much as possible, in ground or underground floors the most heavy equipments (transformers, generator sets, motors, panel boards). The electrical loads of building upper floors (inclusive lighting and appliances) has to be subdivided in areas not horizontally in the same level of each floor, but in vertical sectors of the whole building, as "towers". Other general design criteria, aimed as a guarantee for the supply continuity, the system reliability and the system protection, have a particular use in these appliances. The paper deals comparing the brush distribution on the basis of the recommendations for the non structural components issued by the National Earthquake Hazard Reduction Program (NEHRP) (edition 2000).