WEGAI was contracted by Siemens to analyze and seismically qualify the new thyristor valve towers for the Pole 3 Project of Transpower, New Zealand. The valve towers span approximately 57 feet from the floor to ceiling of the base-isolated valve hall building, weigh nearly 43,500 lbs, and the systems are pre-tensioned using specialized pre-stressed damping devices developed by GERB.

The valve tower presented many engineering challenges for the seismically demanding sites of the New Zealand Haywards and Benmore substations. Analysis of the tower’s structural components was performed using Non-Linear Direct Integration Time History Analysis of seven different scaled earthquake records.

The input time histories (floor and ceiling attachment point) used for qualification were developed from a model created by Aurecon of the base-isolated valve hall building. One of the key challenges was limiting the peak displacements of the low frequency valve tower such that the telescopic and rigid valve hall bus work was within design tolerances. WEGAI worked closely with engineering teams of Siemens, GERB, and Aurecon to develop the pre-tensioned system of the valve tower and seismically qualify the crucial component of the HVDC system.

Click the link below to watch an overview of this project.