The Client
Transpower New Zealand Limited (TPNZ) is the state-owned enterprise responsible for owning and operating the transmission network in New Zealand.
Transpower provides the infrastructure and market systems that connects electricity generators to major electricity users and distribution networks that deliver electricity to homes and businesses around New Zealand. Meridian Energy Ltd is a prominent New Zealand electricity generator and retailer. They generate electricity exclusively from 100% renewable sources, including hydro and wind generation.
Their Needs
Meridian Energy has constructed a new 542GWh wind farm (Harapaki) and required a point of connection to Transpower’s transmission network. Transpower is building a new substation to allow connection of the wind farm to the 220kV WRK-WHI A double circuit transmission line. As a preferred consultant for Transpower,
Groundline Engineering was tasked with conceptual design and on-site support to complete construction and enable generation transfer by mid-2024. The double circuit WRK-WHI A line is the sole supply of electricity to the Redclyffe / Napier region; hence the connection design had to consider a live circuit during the entire construction phase. The tower design also had to consider the unbalanced loading as a result of the single circuit termination, and poor soil properties supporting the foundations.
What We Did
Connection of the WRK-WHI A line to the Harapaki substation required one circuit to be terminated at one of the existing lattice towers, so that it could be redirected into the substation terminal gantries. Since the chosen termination tower was a suspension structure, one side needed crossarm modification to terminate the circuit.
Due to the unbalanced loading on the tower and foundations, an assessment of the foundation capacity was undertaken and suitable strengthening designed to support the updated loading and poor soil strength. To ensure lightning protection could be installed on the incoming circuit, new earth peaks were designed and installed. Due to the location of the substation in relation to the chosen termination tower, an additional intermediate pole structure was also required to ensure electrical clearances to ground and access routes were maintained.
The Results
The final design enabled the existing lattice structures to be utilized and for the entire construction work to be undertaken whilst one circuit was live. This was critical to the construction of the substation and the final connection to the windfarm to enable commissioning. Meridian’s Harapaki wind farm finally went live in July 2024 and by October was operating at 50% capacity.
Groundline is proud to be playing our part towards a net zero economy.
