SVCs to the rescue

Transpower is applying leading ‘reactive power compensation’ technology to enhance its upper South Island network and secure the region’s electricity demand for the near future.

One of Transpower’s most recent grid projects involves the installation of Siemens’ static VAR compensators (SVC’s) at the Islington substation in Christchurch and at the Kikiwa substation near Nelson.

These projects, together with the other sub-projects incorporated in the ‘Upper South Island Reactive Support project’, will provide security of supply for Transpower in the short to medium term. However, the lines company admits that further transmission enhancement will be required for meeting the forecast load growth in the longer term.

The current power system has insufficient dynamic ‘reactive support’ at Islington to meet the reactive power demands of the connected load during the transient period following a power system fault, says Transpower.

Consumer load requires ‘reactive power’ that varies continuously, increasing transmission losses and affecting voltage in the transmission network. To prevent unacceptably high voltage fluctuations, (or even power failures) this reactive power has to be compensated and kept in balance.

In the past, compensation has been achieved by ‘passive’ elements such as reactors or capacitors (and combinations of the two) that supply inductive or capacitive reactive power. The more quickly and precisely the reactive power compensation can be achieved, the more efficiently transmission can be controlled – it is for this reason, slow mechanically switched components have been almost completely replaced by fast thyristor and IGBT controlled devices.

The multi-million dollar contracts for Islington and Kikiwa were won by Siemens. Work involves the turnkey installation of Static VAR Compensators (SVC’s) at both sub-stations. The modular SVC is used for a wide range of applications like reactive power compensation and the modular design uses far less space than other compensation solutions.

Siemens Power Transmission and Power Distribution Business Development manager Marcus Ling, says the SVC technology will potentially extend the life of the lines by three to four years. The Islington project involves a standard SVC and is expected to take about 16 months to complete, while the Kikiwa upgrade will be commissioned four months after that.

Ling says the Kikiwa project will incorporate a new Siemens SVC known as the SVC-Plus, which is only the third one the company has sold worldwide after the first two units were bought as part of a wind farm project in the UK. “This is leading edge technology,” he says.

The Islington project got underway during the winter of 2008 with a team of up to five engineers from Germany, along with a project manager from Australia. While Siemens has supplied Transpower with the likes of circuit breakers and transformer bushings for some years, these will be the first large projects the company has done for the Kiwi lines company.

“This demonstrates that we are much more than just a supplier of products,” Ling comments.

Transpower’s project development manager Daniel Crawshay iterates the importance of the two projects for the future of Transpower’s South Island network.

“We had carried out a number of studies that showed that our ability to recover voltage after faults in some parts of the upper South Island might not be adequate in the future, so we initiated a series of projects to support that part of the network.”

Crayshaw says Siemens won the tenders because the company had valuable experience with ‘Active Filter’ (a Siemen’s trademark) and HVDC work, had a good product and responded quickly and efficiently during the tender process.

“We felt their solution was well considered, and that we could work with them around the commercial considerations. We look forward to a successful partnership with Siemens.”

Sorting out the acronyms

In the electricity world of acronyms SVC’s are one type of Flexible Alternating Current Transmission Systems (or FACTS) device. FACTS refers to a group of resources used to overcome limitations in the transmission capacity of a electrical network, and with the purpose of supplying a network as quickly as possible with inductive or capacitive reactive power, while also improving transmission quality and efficiency. The project at Islington involves FACTS application and thyristors as the switch, while the Kikiwa project involves a SVC PLUS using IGBT’s as the switch.

Transpower is not alone with these challenges. Anthony Johnston, the marketing manager for the Power Transmission and Power

Distribution Division of Siemens, says the globalisation of energy markets with associated deregulation and privatisation are resulting in bottlenecks, uncontrolled load flows, instabilities, and even power transmission failures worldwide.

“Power supplies are increasingly dependent on distributed power plants with higher voltage levels, a greater exchange within meshed systems, and transport to large load centres over what are often long distances.”

Implementing new transmission systems and components is a long-term strategy for meeting these challenges, he says, but over the short and medium term, modern transmission technologies can be employed at comparatively little expense to rectify or minimise bottlenecks and substantially improve the quality of supply.

“Often, this makes it possible to postpone investing in new plants and, as a result, to achieve critical advantages over the competition – especially important in deregulated energy markets in which power supply companies are subject to extreme pricing pressure.”

Johnston says Siemens has developed a number of modern, flexible, high-capacity FACTS for efficiently and reliably regulating voltage, impedance, and phase angle when transmitting power over high-voltage lines.