Our vital links: Grid has the power to share the load

Power from the national electricity grid feeds into this Transpower grid exit point between Whanganui and Fordell.

Sharing the load is what it's all about in terms of ensuring electricity feeds into Whanganui's homes and businesses.

Given the city straddles the Whanganui River, the issue for supply company Powerco is to ensure the power gets to everyone if there's an outage.

Power to the city is supplied from two Transpower grid exit points (GXPs). The Brunswick GXP is on Brunswick Rd while the Whanganui GXP is a few kilometres east of the city on No 2 Line between Durie Hill and Fordell.

A Powerco spokesman said some would refer to the Fordell GXP as Blink Bonnie; that is not technically correct.

"Blink Bonnie is a Powerco substation that mostly supplies Durie Hill and the rural areas of Mangamahu and Fordell," he said.

The Brunswick GXP is on Transpower's 220kV system with the Whanganui GXP on its 110kV system. The 220kV line runs directly from Bunnythorpe to Brunswick and can be seen running just north of Fordell while the 110kV runs from Bunnythorpe "stops" at a GXP near Marton and carries on to the Whanganui GXP. This line can be seen running just to the south of Fordell.

Electricity is generated by New Zealand's hydro, thermal (coal and gas), geothermal and wind generation stations and then transmitted throughout the country by Transpower on high voltage transmission lines to distribution companies and directly to major industrial companies at 110kV, 220kV and 350kV. Substations lower voltage to that used by the local electricity distribution network or lines company (typically 66kV and below) at the point where electricity is delivered to Transpower's customers. Distribution companies' lines are used by Powerco to deliver electricity to its domestic and business customers.

Powerco said normally the load is distributed across the two GXPs but in the event of an outage of either one, the remaining one can carry the total load.

Normal network configurations mean Castlecliff, Kai Iwi, Peat St and Roberts Ave substations are supplied from the Brunswick GXP. Beach Rd, Blink Bonnie, Hatricks Wharf and Taupo Quay are supplied from the Whanganui GXP.

Whanganui's central business district is supplied from the substations at Hatricks Wharf and Taupo Quay.

Powerco is the country's second largest electricity utility and largest gas distribution utility with about 442,000 consumers across much of the North Island.