As part of Wellington Electricity Lines Ltd’s (Wellington Electricity) ongoing work to provide cost effective risk based solutions to High Impact Low Probability (HILP) events, this paper provides an update of work between Wellington Electricity and LineTech to develop an emergency overhead lines system as a contingency plan to bypass any 33kV underground cables damaged during a major earthquake.
The concept envisaged was a set of pre-planned and fully designed emergency overhead routes between key substations, connected with overhead lines built with concrete poles.
Because the emergency line routes run in part across public parks, along paved streets etc, a system of surface mount pole foundations was envisaged to avoid excavating and damaging existing underground services, and speeding up construction of the line.
Staying of poles is not practical or desirable in many locations so a heavy duty foundation option is needed. The surface foundations will enable poles to be placed almost anywhere. The foundations will be made of steel and weighted down with concrete anchor blocks.
Prototypes of both these foundations have been manufactured. As they are completely new and untested designs, physical load testing is needed to check if the designs would work as intended.
This paper sets out the results and lessons learned from the first round of prototype load testing on both the large and small foundation, carried out in Oct 2015 and summarises the plan to complete the emergency overhead lines system.
-Wal Marshall and Richard Steer
Full report can be downloaded below: