China’s ultra-high voltage power grid has created a “sink” in the Earth’s magnetic field which could stretch from the country’s southwest to the Indian Ocean, according to a study by Chinese scientists.
The particle sink – generated by a resonance between the world’s largest power grid and the ionosphere – has led to electrically-charged particles falling from space, but the researchers believe most of the energy was absorbed by the atmosphere and is unlikely to harm human health.
However, the increase in electrons could affect communications, GPS, sensitive electromagnetic surveillance devices and possibly contribute to extreme weather events such as thunderstorms, they said.
Beihang University associate professor Wu Jing and her collaborators from the China Electric Power Research Institute and Peking University said limited data, and the complexity of wave-particle interactions in near space, meant it was unclear how and to what extent China’s power grid could affect the planetary environment.
“With the growth of ultra-high voltage power lines in our country, the issue requires close attention,” they wrote in a paper published in the Proceedings Of The China Society For Electrical Engineering, a Chinese peer-reviewed journal, on Monday.
China is the only country with power lines that send electric current at 800 kilovolts or more. The ultra-high voltage technology connects the hydropower stations, solar panels and wind farms in its western regions to the densely populated, power-hungry coastal provinces more than 3,000km (1,800 miles) away.
For comparison, the most powerful lines in the US handle currents of no more than 500 kilovolts, limiting their transmission range to just a few hundred kilometres with only one-sixth of China’s load capacity.
The first Chinese ultra-high voltage project was a 650km line between coal-rich Shanxi and the industrial province of Hubei, built in 2009. Since then, the total length of these lines either in operation or near completion has grown to 48,000km – longer than the equator – according to the latest official data.
Some of the new lines can send a direct current as strong as 1,100 kilovolts and have increased the energy load by 50% from the earlier 800 kilovolt lines.
Chinese scientists carried out a large number of studies on potential radioactive exposure before the ultra-high voltage power lines were built, which suggested that in most cases exposure would be far below safety thresholds.
This is because the ultra-high voltage lines are taller than typical power lines and data collected after they came into operation confirmed the scientific estimates.
But safety concerns remained, with some nearby residents complaining of occasional shocks when they touched metallic objects, such as a clothes drying rack. Measures to address the problem in recent years have included wire fences over roofs or tree-planting to reduce the inductive current in affected neighbourhoods.
According to Wu, most existing studies focused on the human health impacts but ignored what was happening in the sky.
Her research team discovered that soon after the first ultra-high power line started operating in 2009, an abnormal increase in electron density began to show up in satellite readings over China, suggesting the formation of an atmospheric loss cone.
After years of study, they found some of the long waves generated by China’s power grid could propagate along the Earth’s magnetic field and make particles sink over the Indian Ocean.
The researchers said that investigating the grid’s impact had not been easy. Although it transmits more electricity than the US, Russia, Japan and India combined, the Chinese power grid leaks only a small amount of energy into the environment in the form of low frequency electromagnetic waves.
The disturbance caused by these waves in high altitudes could easily be confused with the effects of a solar storm or other natural phenomenon, they said.
The study examined other possible causes such as sun activities and low frequency radio stations, but ruled them out because the phenomenon occurred regularly, even when the sun was quiet and in regions without large-scale transmitters.
The idea that a power grid can affect the atmosphere is not new. In the 1970s, a Stanford University research team working at a radio station in Antarctica picked up signals they believed were generated by Quebec’s power grid.
Mathematical modelling suggested the low frequency waves produced by power lines could reach an altitude of 3,000km or more where they could resonate with the ionised layer of the Earth’s atmosphere and disrupt the magnetic field which shields the planet from cosmic rays.
In the 1980s, some researchers suspected the increase in thunderstorms across North America from the 1930s to 1970s was related to this effect. But the theory did not receive much attention because the power grid was at that time believed to be too weak to make such an impact.
For decades, the US and other Western countries explored development of ultra-high voltage technology but abandoned it because the traditional ceramic used to insulate the current meant a transformer could reach a weight of several thousand tonnes.
Chinese scientists and engineers solved the problem by replacing the ceramic with paper, which significantly reduced the weight of a transformer but is also difficult to produce because it could burn if tainted by a single grain of dust.
Brand new cables, high performance switches, noise cancellation and artificial intelligence control technology were also developed to make the commercial operation of these lines possible.
Beijing has plans to sell ultra-high voltage power technology to other countries, to eventually create a worldwide grid by 2050. Some of these lines are already up and running, in countries such as Brazil.
Wu said the particle sink generated by China’s power grid was already affecting some human activities, including electromagnetic surveillance for earthquake activities. She added that the problem could get worse with the country’s rapid increase in renewable energy production requiring more long-distance transmission.
An environmental scientist at Beijing’s Tsinghua University said the man-made particle sink could exist, but its scale and intensity would be small compared to those occurring in nature.
The scientist, who asked not to be named because of the issue’s sensitivity, said the many factors involved would make it difficult to confirm a link between the power grid and extreme weather.
Chinese studies have found that lightning activity in China has been on the rise, with about 4,000 people killed annually in recent years – 10 times more than 20 years ago.
Whether the increase could be linked with global warming, air pollution or the power grid required further investigation, the scientist said. – South China Morning Post