Late last year CTC Global announced a significant joint venture with the NARI Group, a wholly-owned subsidiary of the State Grid Corporation of China, the world’s largest electric utility company. Power Engineering International spoke to Dave Bryant, CTC’s Director of Technology, about the growing realization of the need to improve power transmission’s effectiveness.
“While a lot of work is being done to help improve efficiency on the generation side, and in the last several decades a lot about improving the efficiency of demand side appliances, there hasn’t been a lot of effort to improve the efficiency of the grid,” says Bryant. “So much energy is lost between generation and the end user.”
CTC manufactures the ACCC (Aluminum Conductor Composite Core), a product designed in response to utilities' need to reduce losses associated with poor-quality materials in transmission lines.
Some of those behind the California-based company come from an aerospace background, and their previous experience saw them recognize the possibilities of changing the materials that conduct power.
They saw the problem's extent at first hand when an energy crisis hit the western US in 2000, with problems directly traced to constrained transmission lines.
In 2003 there followed a major outage in the eastern US and parts of Canada that caused around $8-9bn in economic losses.
"It took three days for the system to be completely restored, but at the end of the day it was a number of sag outages on 345 kv lines that dropped down the 138 kv voltage lines. It was conductor sag that caused these outages. We saw similar things happen not long after in Europe, and two years ago there was a major outage in India, the largest in history."
“The problem [in 2000] was exacerbated by congested or constrained transmission lines that could no longer deliver power from remote generation due to thermal sags," said Bryant. "We introduced carbon fibre to transmission lines for its high strength, light weight and low co-efficient of thermal expansion to mitigate the thermal sag. We essentially replaced the steel wire that supports overhead conductor, generally made out of alumina, with carbon fibre to get the added strength. We could then operate the conductor at higher temperatures without causing excessive sag.”
In recent years the increased share of renewables on the European grid has presented challenges which CTC looks well-placed to meet. There is a growing appetite among lawmakers and industry chiefs alike to see the European grid infrastructure improve its capacities, and for the grid itself to be extended. It is of particular priority to the wind sector, many of whom believe the entire industry is threatened by restricted interconnection.
Bryant says: “One of the challenges in Europe is that there is not a lot of available real estate to build new lines, so it’s very important to increase the capacity of existing corridors and many utilities within Europe have already discovered how the ACCC conductor in a range of voltages has enabled them to do that effectively.”
In recent years CTC has performed a number of projects aimed at increasing the capacity of the existing European grid, not only for lines coming out of base generation plants but also from other lines that are thermally constrained and where capacity needs to be upgraded due to an increase in demand or in tying in new sources of renewables.
The characteristics of the ACCC that can enable power transmission to up its game are that it offers conductor of the same diameter and weight as the conventional but it uses 28 per cent more aluminium and it also uses aluminium that offers improved conductivity compared to the aluminium alloys more usually found.
Some of the alumina conductors commonly used in Europe don’t have a steel core but only offers conductivity of 53 per cent of that of copper. The 1350O type alumina used in ACCC offers conductivity of 63 per cent of that of copper. The added content and improved conductivity helps improve the capacity of the wire and critically also reduces the electrical resistance so that line losses aren’t exacerbated under high demand conditions.
“In other words if we run more current there is exponential line loss associated but because of the improved connectivity the line losses aren’t as pronounced as if you were running higher capacity through a conventional conductor. There is a second tier advantage that relates to the efficiency.”
With ten years now on the clock, 280 projects completed in 29 countries, CTC has built up a a body of experience in every condition from extreme desert to ice load to areas where corrosion is a big issue. While the quality of the materials within the product give it a resilience head start, Bryant acknowledges that there have been tough lessons, in Europe and further afield.
Bryant explained: “It’s a very challenging undertaking to introduce a new technology to a very conservative industry. In Poland we did an installation in 2009 for a 100km line and we only had a 30 day outage to work with. PSE, the Polish grid operator, hired six different construction companies because they wanted to give all of these companies experience in installation of a ACCC conductor. Because time constraints were so tight they had 16 different crews working simultaneously and many parts of the line were over railroads or highways where the outages were limited and they ended up making mistakes during installation which caused the wire to break after it was installed.
“So we have had to learn the hard way at times but that said those experience have helped us to grow at a more accelerated rate as we’ve been able to share those mistakes with others to prevent them being repeated.”
So to China, where CTC’s most recent and exciting progress is being made. While quality and quantity of labour pool can often be a negative factor in countries such as Indonesia and India, this hasn’t proven the case in China, but there is a different and persistent threat – the copycat manufacturer.
Bryant said: “We’ve completed between maybe 90-100 projects in China to the point that we have established a joint venture manufacturing relationship with China State Grid, one of the two major utilities and we are now building a core production facility with a subsidiary of China State Grid to be able to ramp up capacity to support the Chinese market.”
The Chinese have very substantial demands for building their infrastructure not only with building new lines but upgrading their existing lines. We have been challenged a lot by knocks offs who try to replicate what we make – the quality from the copy cats’ performance is not the same and could give the technology a black eye.”
Luckily China State Grid was motivated to pursue the joint venture with CTC to put paid to the scenario of project delays and failures caused by just such knock off imitations.
“Because of the environmental conditions the product operates in is very harsh and you operate in a high voltage arena you are susceptible to corona, ozone UV radiation, thermal fatigue and cyclical and vibration aspects that can chew away at a product that is not designed to be robust. This is why China State Grid took an interest in taking the technology under their wing so that they can do a better job at controlling the copycats to some degree.”
With energy losses via transmission as high as 28 to 33 per cent in countries like India (the US corresponding average is 7-9 per cent), the need for CTC’S product looks likely to come under increasing consideration for utilities around the globe in the coming years with increasing scrutiny on power and associated financial losses demanding it.
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