IEEE 693:2005 pdf free download – IEEE Recommended Practice for Seismic Design of Substations
1.5.1 Acceptance of previous versions of IEEE Std 693
Equipment qualified to IEEE Std 693-1997 or later versions will be deemed to be in conformance with thecurrent version of IEEE Std 693, and the qualification need not be repeated, unless a previous qualificationtest or analysis method is explicitly excluded by the current version.The qualification will be acceptableonce the explicitly excluded part is done according to the current recommended practice and foundacceptable according to A.5 or A.6.Additional documentation will be required if the current versionrequires additional documentation.
For a manufacturer to use a qualification from a previous edition of this recommended practice to qualifythe equipment to the current version of this recommended practice,a supplemental report must beappended to the old qualification report explaining how sections excluded in the new version of therecommended practice will meet the adequacy criteria given in 1.5. The identification tag for the equipmentsupplied to that user can state that the equipment has been qualified to the current IEEE Std 693.
1.6 Earthquakes and substations
Earthquakes are caused by the sudden rupture of a geologic fault. Shock waves radiatc from the faultfracture zone and arrive at the earth’s surface as a complex multifrequency vibratory ground motion,having both horizontal and vertical components.
The response of buildings and structures to earthquake ground motion depends on factors,including theirconfiguration, strength of construction, ductility, and their dynamic properties. Lightly damped structureshaving one or more natural modes of oscillation within the frequency band of ground excitation canexperience considerable amplification of the forces, component stresses, and deflections.
Mechanisms that absorb energy in a structure, in response to its deformation, provide damping.
lf two or more structures or equipment are linked together, such as through a conductor, they may interactwith one another producing a modified response and interaction loads. Even when the link is sufficientlyflexible to accommodate the relative displacement,forces may be transferred between the structures orequipment including dynamic effects. Therefore, particular care should be given to that design aspect sothat the level of forces is minimized.However, provisions should also be taken in equipment design to takesuch forces into account.(See 5.9 and IEEE Std 1527-2006 [B23].) In particular, many items of substationequipment,for electrical reasons, are highly interconnected and often contain brittle, relatively low strength(compared with,e.g.，steels),and/or low damping materials (e.g., porcelain). The conductors are ofieninstalled with very small slack. In these cases, after only a little relative motion occurs, damaging nonlinearinteraction，including impacting between connected equipment will begin.Thus,items of substationequipment whose natural frequencies lie in the normal frequency range of earthquake ground motion areparticularly vulnerable to damage by seismic events.
1.7 Design and construction
lt is recognized that a substation may not always be designed and constructed solely by a utility using its in-house expertise. A substation may be designed as a “turnkey contract.” In between these two extremes liemany hybrid possibilities, including the involvement of consultants or architect-engineers as third parties.
After the substation is complete, the user should have procedures that ensure that the installed configurationand any subsequent modification or expansion of the substation is subject to proper review to verify that theintentions of this recommended practice are preserved.