Transend: Network critical

Transend, Hobart
Transend is building 250 transmission towers along a 100 km route north of Hobart, Tasmania

Tasmanian transmitter Transend races against the clock to complete vital electricity infrastructure supply in time for winter.

The Tasmanian winter can hit cold and hard, with maximum temperatures of 3-12 °C. Tasmanian government-owned high-voltage transmitter, Transend is looking to complete construction of 250 transmission towers along a 100 km route north of Hobart before winter sets in to ensure security of supply as forecast demand continues to increase.

Managing the $130 million investment between Waddamana substation and Lindisfarne substation – the biggest project Transend has ever taken on – is general manager transmission services, Mike Hunnibell.

“This capital works program is critical in setting up our network for years ahead,” Mr Hunnibell told Energy Source & Distribution.

“It is a significant investment in Tasmania. The real key driver is to provide security to, certainly, the greater Hobart area, but also to the southern part of Tasmania. Currently we only have one 220 kV supply point into the south and that is supported by some fairly old and under-capacity lines that no longer can meet the forecast demand in the south,” he said.

“It’s really the unreliability and capacity of existing infrastructure supporting southern–based load. That’s compounded by the fact that we’ve got an increasing forecast demand.”

The new transmission line replaces an old 110 kV line between Waddamana and Bridgewater substations and will supply the electricity to new transformers at Lindisfarne substation. At present, the transmission system relies heavily on Chapel Street substation in Glenorchy for supply to Hobart and the south of the state. Chapel Street is the only 220 kV supply point in the Hobart area.

“It certainly assists in network security, hence it provides more flexibility in terms of power flows from generation to the market and managing the nuances of Basslink, that can either import or export. So it’s really trying to remove constraints on the network as well, not only from a transmission perspective but also from a generation perspective,” Mr Hunnibell said.

Transend has installed two transformers – a total investment of $7.6 million – in a new 220 kV switchyard at the Lindisfarne substation.

“Each transformer cost $3.8 million and will be capable of transforming 200 MW of electricity from 220 kV to 110 kV, after which the electricity will be passed to other substations at that voltage or dropped to 33 kV at Lindisfarne substation to be passed into the electricity distribution network operated by Aurora Energy,” Mr Hunnibell said.

Alstom Grid’s state manager Tasmania, Gustavo Bodini said Alstom Grid (previously Areva) had been selected to design and construct the new Waddamana 220 kV substation and upgrade the Lindisfarne substation, reflecting the company’s technical expertise and its long-term association with Tasmania.

Hazell Bros’ managing director, Geoffrey Hazell said that the construction and resources company had been awarded the substation work in a joint venture with Alstom Grid.

“We are committed to the ongoing development of the state, and we are pleased to keep Tasmania progressing through our involvement in this needed infrastructure project,” Mr Hazell said.

The project will be commissioned by the end of first quarter 2011, a critical time for the network.

“We really need it to be commissioned then. Tasmania still has its maximum demand in the winter months, not like other states where their peak demand occurs in the summer months largely due to the air conditioning loads. It’s critical that we commission this project before winter and we’re working with our contractor to make sure that commissioning occurs at this time. At this stage everything is on track for this to occur,” Mr Hunnibell said.

Transend is looking closely at the IEC 61850 communication protocol and working with other transmission network service providers in establishing protocols to achieve consistency from a national perspective. The standard simplifies the communication between all the IEDs within the substation either at a bus or process level.

“As we renew our relays and protection schemes in our substations, all replacement equipment will be compatible with the IEC 61850 standard. We’re assessing the benefits from our perspective and are moving toward adopting the IEC 61850 standard,” Mr Hunnibell said.

Transend works closely with Tasmanian distributor, Aurora Energy, every year to collaborate on the annual planning review for demand forecast, potential hot spots and constraints on the network. Transend is in its second year of its revenue reset period, which expires in 2014, with up to $400 million of capital expenditure remaining.

“We’re starting to get on top of our larger-type infrastructure projects, such as this line, and our renewal program is going well, so we’re in pretty good stead moving forward. This capital works program is critical in setting up our network for years ahead,” Mr Hunnibell said.

Transend’s work program of installing optical ground wire (OPGW) fibre could provide future opportunities for collaboration in the NBN environment.

“Effectively we are rolling it out for operational purposes, including providing diversity in our communications network between our key sites,” he said.

“Once we have fibre in the air there may be opportunities to work with NBN by providing capacity to them that will complement their fibre roll-out.”

Transmission upgrade

Transend has made use of high-temperature conductors and dynamic ratings to improve the quality of its transmission network that has helped manage the network during the upgrade.

“In some of our lines in the inner-Hobart area where obtaining easements are going to be problematical, we’ve actually increased transmission line capacity by using a high-temperature conductor between a couple of our sites. High temperature conductor allows transmission lines to be operated at higher design ratings and hence we can increase the power flows through those lines,” Mr Hunnibell said.

An old copper conductor was replaced with a high-temperature conductor on an existing line to increase the capacity through a fairly contentious corridor. The operating temperature range has now been improved from a design rating of 49°C to potentially up to 230°C. It also prevents lines overheating, sagging and breaching conductor to ground clearances.

Transend makes use of dynamically run lines on its entire transmission network. It receives direct meteorological data that correlates transmission line operating temperatures to the weather conditions, wind, temperature and other factors.

“So, depending on the conditions of the day, we can either increase the power flows or, in times of hot weather, sometimes decrease the power flows. And that’s basically so we don’t breach statutory conductor-to- ground clearances,” he said.

Dynamic rating releases additional capacity into the system and helps defer capital expenditure.

“But it means we know what our constraints are on any particular day because we’ve got a direct correlation between weather and power flows.”

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