Dynamic Phase Lag Studies of Damper Mounted Substation Structures

Stability and safety of fragile equipment used in electric power applications are in demand against strong ground motions. Post-earthquake data necessitates the seismic studies on substation used porcelain components in evident to the poor serviceability of the equipment. The installed structures that failed at the field are experimentally tested and passed in laboratories under real-time earthquake motions. In addition to that, with the influence of the heavy movement of tectonic plates, the site-specific conditions are varying rapidly and consequently resulting in the progression of structural failure. Therefore, mitigating the vibration at the base level of the supporting structure is one possible solution to the undesirable ground accelerations. In this paper, two current transformers of different ratings supported on steel structure are considered and evaluated for response phase when subjected to site specified accelerations at critical frequencies with the help of experimental damping factor. Also, the structure is studied for viscoelastic damper attached at the base to recognize the phase shift with the specified ground accelerations. In both the cases of the structure with and without the damper, the system damping is extracted from shake table experiments of 0.3 g ground acceleration. Conclusions are derived for the model connected with damper during complete earthquake vibration using angles of phase versus frequency ratios. The results may be used in redesigning the structure prior to the standard recommended testing.