As a result of the nastiest snowfall in five decades the Chinese government has sent a working team to Chenzhou, the city worst hit by snowstorms in south China's Hunan Province, to investigate causes of the widespread power blackout.

The working team, organized by the National Development and Reform Commission (NDRC), includes officials and experts from the NDRC, the State Grid and power consultative companies. At damaged transformer stations, they found that heavy and thick ice had formed on power lines and poles, the cause of much of the trouble.

The minimum temperature in Chenzhou this winter was minus five degrees Celsius. At first it seems odd that Chenzhou had such problems, especially compared with northern China, where winter temperatures can be as low as minus 20 to 30. Yet in the north there is no ice formation on power supply lines.

"The humidity here is all to blame," said Liang Zhengping, senior engineer with China Power Engineering Consulting Group Corporation (CPECGC). "When the temperature ranges between zero and minus five, the moisture in the air can easily freeze on power lines and accrete gradually if bad weather lasts."

Wu Yun, chief engineer of CPECGC, said the iron tower supporting the power lines usually weighs six tons, however, when ice becomes thicker and thicker on it, it weighs some 50 tons or six times the original, that's the reason it collapsed.

An official in charge of the investigation said that with lessons learned from this snow and ice disaster, China will further improve its emergency mechanism for power supply, with adjustment to grid designs to raise their reliability.

The snow havoc over the past few weeks in China has resulted in direct economic losses of about 80 billion yuan (11 billion U.S. dollars), toppled 300,000 homes, damaged 90 million hectares of crops in 19 provinces and regions, the Red Cross Society of China said earlier this week.

It has also killed scores of people and disrupted transport and power services across a large swathe of the country's southern, central and eastern regions.

(Xinhua News Agency February 9, 2008)