IEC 62271-2:2003 pdf download.High-voltage switchgear and controlgear
4 Seismic qualification requirements
The seismic qualification shall demonstrate the ability of the switchgear and their assemblies to withstand seismic stress.
No failure on the main circuits, the control and auxiliary circuit, including the relevant mounting structures, shall occur.
Permanent deformations are acceptable provided that they do not impair the functionality of the equipment. The equipment shall properly operate after the seismic event as defined in 8.2 and 8.3.
Analytical methods, experimental methods or a combination of both shall be used to perform the seismic qualification.
If analytical methods are used, sufficient data is required; if not, a sample test set-up representing the system for the purpose of structure and function shall be subjected to a test. This basic experimental data shall be used as input for calibration in analytical methods.
For complete switchgear assemblies (e.g. substations) the analytical method shall be considered as a sufficient demonstration for seismic qualification.
4.1 Preliminary analysis
4.1.1 Selection of the representative test-set
Due to practical reasons concerned with the available experimental facilities, the seismic qualification of switchgear and their assemblies can require the definition and the choice of different sub-sets which still meaningfully represent the whole system for the purpose of structural and functional checks.
Such test-sets shall include the switching devices with their relevant operating mechanism and control equipment, and their electrical and mechanical interfaces.
It is recommended:
— to test generic components;
— to identify the dynamic behaviour of the plant (natural frequencies and damping ratios) through the experimental activities of Annex A.
4.1.2 Mathematical model of the test-set
On the basis of technical information concerning the design characteristics of the substation, a three-dimensional model of the test-set shall be created. Such a model shall take into consideration the presence of actual compartments and of their supporting structures, and shall have sufficient sensitivity to describe the dynamic behaviour of the test-set in the frequency range being studied.
For vertical severities, the direction factor is 0,5 (see IEC 60068-3-3).
NOTE 1 The required response spectrum of qualification level AF5 covers, in the range of predominant seismic frequency of 1 Hz to 35 Hz, the following response spectra: Endesa, Edelca, USA/NRC RG 1.60, Newmark Design Response Spectra (scaled to 5 m/s'), Nema (5 m/s' maximum foundation acceleration), Dept. of Water & Power Los Angeles, San Diego SDG & E Imperial Substation.
NOTE 2 Information on the correlation between seismic qualification levels and different seismic scales is given in IEC 60068-3-3.
The selected qualification level shall be in accordance with expected earthquakes at maximum ground motions for the location of the installation. This level corresponds to S2-earthquake (see IEC 60068-3-3).IEC 62271-2 pdf download.