Longyan City, China - On July 1, 2006 preparation began for the 5th installation of CTC Global's ACCC conductor in mainland China. Since that time, 220 other ACCC projects have been completed in China and 23 other countries.
In the wake of Hurricane Sandy, this project is particularly relevant and may provide clues as to how we can cost-effectively 'harden' our key electrical transmisson infrastructures, worldwide.
The Longyan project was located in South Eastern China's Fujian Province. At the beginning of the project, anchors were installed for bull wheel tensioners and pullers, and bamboo guard structures were built over 37 existing under-built transmission and distribution lines and a number of primary roads and railways that crossed under the path of this relatively short reconductoring project. Three 15,000 foot sections of a 220kV transmission line were reconductored using 1020 kcmil Drake ACCC conductor to increase ampacity without having to replace or modify the existing lattice structures.
The job had several challenges to overcome. The terrain was particularly difficult. Of the thirteen steel lattice structures that had to be accessed, only three were accessible by vehicle. The other structures were located on mountain tops covered with very thick vegetation. Span lengths were quite long between mountain tops. The longest of these spans was over 2,500 feet. Changes in elevation were also substantial and challenging.
Another major challenge was the weather. South China had just begun going through the most active typhoon season in recorded history. This was after having already gone through a very active rainy season and a number of smaller "pre-season" typhoons, two of which happened during the course of construction. The installation site was plagued with mud, flooding, broken sewer lines, landslides, and even a disheveled pig farm. At the time of the installation, the crew didn't want to talk about the native animals - many of which you would only want to encounter at a zoo or at at a safe distance. The conditions, by anyone's standards, were challenging.
On July 3rd, 4th, and 5th the job site had to be abandoned to allow a typhoon to pass. Work soon resumed, and by July 8th the two spans between towers eleven and thirteen were complete with all three phases of ACCC pulled in, sagged, and dead-ended. This included a 2,558 foot span between towers twelve and thirteen. The difficult terrain and conditions made it impossible to get heavy equipment to each of the structures and progress on the installation was relatively slow.
Because of the length of the spans, extreme changes in elevation, and all the under-build, pulls had to be done under very high tension conditions. By July 14th, all conductors had been pulled in. Double blocks were used to avoid severe bending around angles and structures with a lot of down pull. Preformed Line Products' "preforms" were used to aid in gripping the conductor with excellent results. The conductors were sagged, dead-ended and placed into double suspension clamps. Compression jumpers were assembled. The tie-in to the adjacent substation was completed, and by July 26th, the line was successfully energized (after a second typhoon hit).
Less than two weeks after the line was energized, "Super Typhoon" Saomai (meaning "morning star" in Vietnamese) slammed into the coastal town of Mazhan in the Zhejiang Province. Saomai was the most powerful super typhoon in recorded history to make landfall in mainland China. Wind speeds were measured in excess of 135 miles per hour. While more than 1.3 million people were evacuated from its path, 458 people perished. The estimated damages were in excess of $2.5 billion (2006) USD.
While it is impossible to predict how much damage a "super storm" or "super typhoon" might cause, or implement a plan to completely prevent damage from occurring, this is one example of how the robust qualities of the ACCC conductor helped one section of the grid remain energized during extremely harsh conditions.
