With overhead lines (OHL) forming a major part of the transmission and distribution network, transient voltage dips can be caused by adverse weather conditions such as typhoons and lightning strikes. To mitigate the potential risks of super typhoon damage, a Hong Kong electricity utility commissioned Fugro to help assess the asset integrity of its transmission network, resulting in a strengthening programme to ensure a safe and reliable power supply.
Hong Kong has a sub-tropical climate and the region can be affected by tropical cyclones between May and November. However, changes in global weather patterns bring an increasing potential for ‘super typhoons’ at a maximum sustained wind speed of 185 km/h or above, with wind gusts of up to 300 km/h.
These super typhoons pose a risk to the region’s overhead lines (OHL). 400 kV towers form the backbone of the transmission network in Hong Kong. If a tower (pylon) is destroyed by a typhoon it can take several months to repair. To counter the potential impact of super typhoons, Fugro was appointed to carry out engineering consultancy services, to assess the asset integrity of a section of the network in Hong Kong and Shenzhen.
Working closely with the structural strengthening design engineers, Fugro provided consultancy services for the planning, design and statutory supervision elements of strengthening of the towers, foundations and slope upgrades.
Services included structural improvements to the steel gantry and cable troughs, integrated geo-structural integrity works and a unique method of strengthening the towers while keeping the structure intact and fully functional during the entire upgrade.
The project faced numerous challenges. For example, many of the transmission towers were in remote mountain regions, with no access roads. Also the work had to be completed in sections to minimise downtime on the transmission network.
Future power quality
The historic seven-year project was completed in 2017, helping to ensure that the utility can maintain a safe and reliable electricity supply for Hong Kong and enhance public safety at large.
Moreover, it highlights the need for electricity providers to migrate towards a condition-based maintenance approach that combines predictive and preventive maintenance. Condition monitoring techniques will detect potential fault conditions in advance of failures, making maintenance a proactive process. Under this approach, vegetation management strategies and improvements to asset management processes are essential to ensure exceptional power quality.
The client said: ‘We are grateful to have Fugro’s professional support on this project, which is making our power grids ready to withstand any challenge from the threat of super typhoons.’