Siemens to expand New Zealand HVDC link

Siemens will modernise and increase the capacity of the existing HVDC link between New Zealand's North and South Island. It received the order from Wellington-based Transpower New Zealand Limited, the national grid operator.

For the "Inter Island Connector Pole 3" HVDC or high-voltage direct-current project, Siemens Energy will supply two turnkey converter stations and replace the aging converters with advanced light-triggered thyristor valves.

The investment volume for the overall project is US$488.57 million. Siemens' share accounts for approximately half.

The aim is to raise the capacity of the existing HVDC system in increments over the next few years from 700 MW to 1400 MW. This is intended to ensure reliable power supply with minimal losses and to further stabilise New Zealand's grid. Siemens will complete modernisation and expansion of the HVDC system by late 2013.

In the course of the multistage conversion and uprating of New Zealand's over 570-kilometer-long HVDC link—of which 40 kilometers are a subsea cable link across the Cook Strait—Siemens will replace the aging converter technology of mercury arc rectifiers with advanced light-triggered thyristor valves. This will involve the installation of two 700-MW turnkey converter stations in the two HVDC substations at Haywards, located north of Wellington, and Benmore on South Island. Siemens will also expand the 220-kilovolt outdoor switchyards of the two substations and replace the existing instrumentation & controls of part of the system with Simatic TDC, the latest generation of its HVDC instrumentation & controls. It is planned to increase the capacity of the HVDC link to 1000 MW by 2012, 1200 MW by 2014 and 1400 MW by 2017.

"With our HVDC and FACTS technology based on innovative power electronics we'll not only enhance the reliability and stability of New Zealand's power supply network but also increase grid intelligence—right in line with a smart grid," said Udo Niehage, CEO of the Power Transmission Division of Siemens Energy.

Siemens will not only supply the converter stations but also a static reactive-power compensation system based on its new SVC Plus or Static Var Compensator technology for grid stabilisation. It will be installed in the Haywards substation and operate with innovative voltage-sourced converter technology, and can be continuously controlled with the aid of insulated-gate bipolar transistors. The scope of supply also includes the converter transformers, smoothing reactors, protection and I&C systems, and AC and DC filters.