Vector powers up to meet district growth

Plans by Vector to upgrade the network in the Mahurangi area can’t happen soon enough, if last week’s blackouts across much of the district are a taste of things to come.

Vector says last week’s power cuts were the result of fallen lines, but security of supply to the area has been identified as an issue.

At a Warkworth Area Liaison Group meeting this month, Vector network performance general manager Richard Pearce said that recent transmission planning reports from Transpower had identified that the Wellsford grid exit point (GXP) was nearing capacity and options to increase supply were being investigated.

The Wellsford Planning Area, which covers from Puhoi to Mangawhai coast to coast, including Kawau Island, is the most northern in Vector’s network. The area is supplied by the Wellsford GXP. The power comes south from Wellsford via two 33,000 volt (33kV) power lines, which were constructed in 1964 and are about 22 km long (route length). Access to the circuits can prove difficult as the lines traverse complex terrain and multiple privately owned properties.

Due to demand growth – the number of individual power connections is forecast to grow from 16,000 to 25,000 over the next 30 years – the Wellsford to Warkworth circuits are expected to soon reach capacity at peak winter evening demand. To address this constraint, Vector has been installing underground cable ducts along SH1, between Wellsford and Warkworth.

Pearce says the project is nearly completed, with only the stretch between Goatley Road and the Matakana link road remaining before the cables can be commissioned.

Vector owns three existing zone substations at Wellsford, Warkworth and Snells Beach, with a fourth zone substation at Omaha due to be commissioned later this year.

The sub-transmission network operates at 33kV and distribution at 11kV.

The 33kV overhead sub-transmission lines are primarily on private land, with some on rough or heavily vegetated terrain.

The medium-term area plan is to establish a new zone substation to the west of Warkworth, and in the longer term, another just north of Warkworth. The northern site will initially be supplied at 33kV, but with the ultimate objective of being supplied at 110kV.

The SH1 cable ducts are also designed for 110kV cables.

Snells Beach and Warkworth are expected to exceed transformer capacity next year and in 2027, respectively. Vector believes peak demand can be managed by battery storage systems in the short term. The constraints will be resolved by constructing a new zone substation on Sandspit Road in 2025 and at Warkworth south in 2029, and the redistribution of the load between a group of five substations.

The distribution network in this planning area covers a very large rural area that contains the longest 11kV rural overhead distribution circuits within Vector’s network. The long feeders are susceptible to outages, resulting in poor reliability, and poor power quality. To address these issues, Vector plans to use both network and nonwires solutions.

In addition, a 1.149 MW/1.254 MWh battery energy storage system has been installed at Tapora to provide improved quality of supply to the Tapora Peninsula, an emerging avocado growing area currently supplied by a long spur feeder.

A new voltage regulator has been installed in Te Arai to improve power quality and a recently-commissioned zone substation in Kaukapakapa has provided significant feeder backup capacity on the Kaipara Flats feeders.

David Stott, Co-chair https://onemahurangi.co.nz