TransGrid’s award-winning $312 million Western 500 kV project has made New South Wales’ network highly efficient, adaptive and flexible. Energy Source & Distribution takes a look at the efficiencies gained from building the National Electricity Market’s largest
capital works program.
More than three decades of planning have gone into linking New South Wales’ key generation areas via the high-capacity Western 500 kV transmission network. Having recently completed its first year of operation, TransGrid studies estimate that the network has reduced electrical losses by approximately 120,000 MW hours, more than double the reduction in losses originally forecast, lowering its carbon emissions by around 112,000 tonnes.
New South Wales’ position in the National Electricity Market (NEM) means its network deals with a substantial amount of power flow, presenting challenges to supplying the major load centres of Newcastle, Sydney and Wollongong. Accounting for around 75 per cent of the state’s peak power demand and as the largest single area of demand in the NEM, maintaining a reliable supply to the region is crucial. The new 500 kV network provides the additional capacity necessary to cater for the growing electricity needs of metropolitan NSW, while increasing the flexibility of the network to enable cross-border energy trading in the NEM. It achieves an efficient way of maximising use of all transmission lines into its load centres.
The project’s completion in 2010 was a milestone in the development and optimisation of the NSW transmission grid and the result of long-term planning by TransGrid over the past 30 years. Through careful project staging and collaborative project management, TransGrid and UGL Infrastructure delivered four new 500/330 kV substations within required timeframes and 2.4 per cent under budget.
Starting work on the design of the project in 2007 before taking over as project lead is TransGrid’s Steve Jones. The sheer scale of the project has left an impression on the project leader.
“They are major 500 kV substations, so they are very large. They stretch from the Hunter Valley area, where Bayswater is, through the western parts of our system down to Bannerby, which is in the southern highlands south-west of Sydney/Wollongong load centre,” Mr Jones told Energy Source & Distribution.
“The transformers are 1500 mVa each, so they are the largest transformers in Australia. The scale of the sites mean that even things like earth works are very much larger scale then we have done previously,” Mr Jones said.
With four large sites on its existing network to be linked together for operation, the challenge was considerable. The main transmission line linking the substations together had already been constructed, although there were still extensive deviations and linkages to be made. Toshiba provided 21 single-phase 500 to 330 kV transformers for the substations, which had to be delivered to each of the sites on time. In the case of the Bannaby substation, TransGrid had to rebuild quite an extensive road system to get the transformers to site.
The substations had to be completed and the power transformed from 330 kV to 500 KV without constraining the national electricity market. With only small outages available on weekends, everything had to run like to clockwork for the team under the 55-year-old project manager.
“Those were transmission lines that were already being used and operated at 330 kV and so that whole process of sequencing the upgrade process from 330 to 500 kV was something that had to be very carefully staged. It was by far the most complex sequencing of projects that I’ve ever been involved with,” Mr Jones said.
Roughly 200 full-time and part-time specialists and technicians from TransGrid were involved over the course of the massive project. One of the core benefits of TransGrid’s new western 500 kV network is its increased capacity and reduced losses.
“Power systems are quite complex to model but certainly from an efficiency point of view, from a New South Wales point of view, the work is achieving quite a lot. Efficiency is up, 120,000 MW hours have been saved. As demand for power grows, then that efficiency will improve as well.”
By increasing the amount of energy that can be transferred between states and improving the efficiency of the network, TransGrid is facilitating a more competitive energy market. Consequently, the Western 500 kV network delivers cheaper wholesale energy and reduces the cost of electricity for end-use customers.
The long-term forward planning process was commended in the Garnaut Climate Change Review Update 2011 and was awarded the 2011 Engineering Excellence Award for Infrastructure Projects in September.
TransGrid executive general manager of capital program delivery Gerard Reiter said he was delighted TransGrid and UGL won the Excellence Award.
“Few electrical engineers will ever have the opportunity to work on a development the size and importance of the Western 500 kV project,” Mr Reiter said.
With new renewable generation joining the market in the future, the Western 500 kV project will make the network much more flexible and adaptable to each of these applications as they connect.
“Its difficult for us to foresee where all the generation might come from and what source it might be, but whether it’s to the north, west or south, this development in our network makes it much more adaptable to any of those locations,” Mr Jones said.
“In terms of being able to provide a transmission service to people who want to connect to our network, providing a quality service of connection service is certainly one of the main aims of Transgrid. Moving forward, that’s certainly one of the areas we are looking forward to assist new generators in New South Wales.”
• 21 off-single-phase 500/330 kV power transformers from Toshiba
• 26 off-500 kV and 13 off-363 kV circuit breakers from Siemens
• 71 off-500 kV and 30 off-362kV disconnectors from Siemens
• 153 off-measurement transformers from Siemens
• 30 off-line traps from Siemens
Dealing with the unexpected
Bird nest debris and high electrical stresses were some of the unexpected operational issues TransGrid contended with while building the Western 500 kV project. Senior engineer Darren Spoor made a presentation to Engineers Australia earlier this year summarising the challenges they faced.
According to the presentation, the 330 kV network was converted to enable operation at the design voltage of 500 kV in response to emerging voltage and thermal limitations, which were predominantly imposed by 330 kV lines within the Sydney region. While alleviating these constraints, several unexpected operational issues required detailed investigation and analysis of fault-trace waveforms and line-inspection reports. These related to voltage control, outage planning and line auto-reclosure issues.
The greatest impact was observed in transmission-line maintenance, protection and fault location.
Despite many years of reliable operation at 330 kV, seven independent earth faults were observed within the first six months of operation at 500 kV. From an analysis of the data it was possible to conclude that these faults were being created by debris from nesting birds, combined with higher electrical stresses between the phase conductor and the steel-cross members of the structures. The compact construction of the 500 kV circuits had also significantly affected the accuracy of most fault-location routines due to the notable transmission line asymmetry on the new 500 kV circuits.
This produced large errors in conventional fault-location calculations, which were compensated using a new correction parameter, applicable for each phase.