Developments in Transmission and Distribution Networks

In the last five to ten years, almost all large or international networks have witnessed a shortfall of investment in the EHV and HV transmission systems, leading in many cases to concerns about security of supply. Despite being critical, transmission is the smallest investment component of the three sectors making up the electricity supply industry. In terms of future requirements, transmission accounts for about 20% of investment and distribution and generation for 40% each. In the past, investment in transmission has fallen short of this share.

The number of transmission failures in the last few years has provoked much public interest and increasing discussion within the power industry. Outages have occurred throughout the world but notably in the US, Italy, Denmark, Sweden and the United Kingdom.

In the United States, which makes up 25% of the world’s electricity supply sector, the growth rate of the bulk transmission system (230 kV and over) has declined from 3.1% a year in new lines in the period 1979-89, to 2.7% from 1989 to 1999 and to only 1.7% a year in the present decade 1999 to 2009. Between 1989 and 1999 utilities added new transmission capacity at a slower rate than loads grew and normalised transmission capacity declined in all of the 10 regional reliability regions by amounts ranging from 10-40%. From its surveys of US utilities, EPRI concludes that in the next four years, transmission investment will increase to US$6 billion a year.

The European Union´s high/extra high voltage electricity network consists of approximately 105,000 km of 380/400 kV overhead line and another 116,000 km of 220-300 kV lines. Up to 2000 there was not any significant expansion although many utility owners had invested in up-grading capacity. More than 50 transmission projects have been identified as necessary by the EU Commission in order to ensure the reliability and dependability of electricity networks, the functioning of the internal market, and the connection of renewable energy sources. Furthermore, 30 other projects are needed with the ten accession countries and non-Member States such as Norway and Switzerland to ensure the reliability and dependability of the electricity grids or supply of electricity within the European Community.

European international interconnections are being expanded significantly, not to mention the expansion linking to North Africa and the Middle East. In China and India, transmission has lagged but is now receiving attention and investment programmes are in hand, with the targets in each case of working to a national network interconnecting all of the regional grids.

This results in increased interest and investment in Transmission and Distribution. There has been a surplus of generating capacity for the last five years and the priority now is to transport the power and to bring it to the consumers. I predict that in about five years the focus will start to shift toward generation again, after much work has been carried out in the transmission sector.

Some T&D Facts:

Total worldwide lengths of T&D lines are forecast to rise from 64.4 million km in 2006 to 69.6 km in 2011. In 2006, the global total of transmission lines was 5.3 million km, forecast to rise to 5.8 million km in 2011. The total of distribution lines will rise from 59.1 million km to 63.8 million km in 2011.