Power line voltage10/19/2023 ![]() This drop has deepened overcapacity in China’s power sector, which according to Bloomberg New Energy Finance was 35% in 2016. ![]() National demand growth averaged 11.7% from 2003-12 but fell to 4.5% in 2012-17, bottoming out at 0.5% in 2015. Meanwhile, the economic case for new UHVDC lines from the interior has weakened amidst slowing growth in electricity demand. ![]() Analysts suggest that State Grid has shelved the backbone plan for now and is focusing on UHVAC lines within individual grids instead. But officials worry about nationwide blackouts cascading across these interconnected grids. State Grid’s UHV plans suggested remarkable ambition, but did not always align with those of central and provincial policymakers.Ĭentral officials have clashed with State Grid planners on its backbone scheme, which envisions a lattice of six UHVAC lines to synchronise grids that are currently in State Grid’s territory. In fact, its national UHV backbone scheme, which is the centrepiece of its UHVAC ambitions, looks unlikely to happen anytime soon. In Inner Mongolia alone, company officials spoke of 11 lines running from the province’s coal and renewable hotspots by 2020.īut rollouts have slowed, and few analysts expect State Grid will deliver on its 2020 target. Its 2013-2020 construction plan envisioned six AC and 13 DC lines by 2013, and 10 AC and 27 DC lines by 2020. Grid companies have been keen adopters, with State Grid, which covers 88% of China’s territory, especially interested. Direct current (UHVDC) lines suit transmission from A to B over distances of more than 1,000 kilometres whereas alternating current (UHVAC) lines work better over slightly shorter distances but permit branching links along the way. The benefit of UHV lines is that they have dramatically reduced losses.Ĭhina has deployed two types of UHV line. In normal high voltage lines, a lot of the power is lost as it’s moved across China’s enormous terrain. Sources: Lantau Group, news reports Big plansĬhinese grid companies have pursued Ultra High Voltage projects to solve a logistical dilemma: coal, hydro, wind, and solar resources are concentrated in the interior, but the heaviest energy demand is along the urbanised east coast. Ultra High Voltage line start points are marked in green and endpoints in blue. This means that approvals for new lines have slowed, and grid companies are unlikely to meet their targets for new ones.Įnlarge map for more detail. The lines themselves are underperforming, and more recent projects are coming online amid a period of electricity generation overcapacity. The technology is beset by conflicts of interest between grid companies and central and local governments. For comparison, no other country has a single UHV line in full commercial operation.īut China’s enthusiasm for UHV is waning. Since 2006, it’s built 19 of these multi-billion-dollar lines, stretching almost 30,000 kilometres and supplying 4% of national electricity demand. If there is an unexpected surge, the ground wire will siphon the electricity down before it reaches the part of the line that’s getting repaired.Įxplainer thanks Anne Mayberry of the Electrical Safety Foundation International, Jim Owen of the Edison Electric Institute, John Palmer of Knott Laboratory, and reader Stuart Cleland for asking the question.China is the global test bed for ultra-high voltage (UHV) transmission lines, a technology that can carry electricity across vast distances with much greater efficiency than the high voltage lines that you’re probably used to seeing. They might also run a ground wire from the cable to the street below. ![]() If workers have to be within 10 feet of a line, the power company can “de-energize” it (turn it off). Even regular folks trimming trees near a power line need to take care-wood isn’t as conductive as metal, but a stray branch can still transmit a deadly shock down the trunk. Most power companies warn workers to stay 10 feet away from power lines and up to 25 feet away from the highest-voltage lines. That means electricity could arc out of the wire to any crane or pole that gets close enough, even if it never makes contact. For large-scale transmission lines, this field can have a radius of a foot or more. The air around a power line isn’t a good conductor, but very high voltages do create a significant electrical field.
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