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Earthquakes

Protection of surge arrestors and generators at a nuclear power station

The seismic range considered in nuclear power plant design is much more demanding since the Fukushima catastrophe. The challenge was to come up with an alternative solution to the standard spring box to protect equipment in nuclear stations and ensure that strategic equipment operates correctly in extreme conditions.

Socitec devised a decoupling system that uses wire rope isolators, justifying its choice with calculations and characterisation tests. The system was qualified for earthquakes on an electrohydraulic shaker unit by the Sopemea laboratory.

The wire rope isolator was chosen because this type of spire-rolled cable possesses considerable elasticity and damping capacities, and significant deformation and dissipation capabilities. The equipment is also unaffected by temperature, humidity and chemical agents and can therefore last as long as the equipment it protects.

SYMOS, dynamic modelling of equipment’s reaction to seismic waves

To produce cable isolator suspension for a surge arrestor in seismic conditions, Socitec employed SYMOS software to model the equipment mounted on isolators, represented by elastic liaisons with properties of stiffness and non- linear isolation.

SYMOS software can be used to integrate different types of isolation models (viscous, dry rubbing, structural, etc.) to obtains highly elaborate models.

Seismic vulnerability of Substations

Electric substations are part of the electric grid system that ensures the delivery of safe and reliable power to every day consumers.

Some substation equipment are extremely vulnerable to seismic vibrations due to their tall and slender design.

Socitec’s wire rope isolators have been used to solve this problem. They are able to absorb seismic vibrations and dissipate them without bottoming out thanks to their inherent damping, low stiffness, and high deflection capability.