Power Blackout Risks

crobriefing on Power Blackout Risks
space weather 
The term space weather summarizes different astrophysical effects the earth is exposed to. Constantly emitted 
clouds of electrically charged particles (plasma) from the sun into space are called solar wind. Large eruptions
of plasma from the sun‘s corona are known as coronal mass ejections (CME) and create solar storms. The sun 
follows an 11 year cycle of changing solar activity with the next maximum expected in 2013. During a solar 
maximum 1 CME reaches the earth’s orbit every 5 days on average, while during a solar minimum only 1 CME 
reaches our planet every 45 days. 
A solar storm that reaches earth, generates intensive showers of particles and gigantic currents in the ionosphere 
(producing bright auroras) and induces major alterations in the geomagnetic field resulting in a geomagnetic storm. 
Large scale electric conductors in the changing magnetic field, whether cables or pipes, run currents called geo-
magnetically induced currents (GIC). Depending on the underneath geology long power lines connect (or short 
circuit) regions of different geoelectric potential. This can trigger GIC (up to 200 Ampere or more over time spans 
of more than 10 seconds) to enter the power grid through transformer grounding cables. The electromagnetic 
induction is higher the longer the transmission line and more severe for east-west directed transmission lines. 
While power grids normally work with alternating currents they are not designed to handle direct currents (like GIC) 
induced by a geomagnetic storm. Those currents affect the electricity infrastructure, in particular high-voltage 
regulating transformers and substations, but also telecommunication networks and even pipe lines are exposed. 
GIC could hold the power to not only cause tripping of transformers but also damage or even destroy transformers, 
resulting in a different quality of power outage, i.e. not only large-scale but also long-lasting.
The first historical event where GIC appear to be linked to a large loss was a telegraph breakdown on September 2, 
1859 – the so-called Carrington event. The day before, scientists detected a spectacular solar flare that had 
triggered a series of CMEs, followed by the largest aurora ever reported. At the same time, the extreme geo- 
magnetic storm overloaded telegraph lines worldwide, causing short circuits and fires in telegraph stations and 
ultimately a breakdown in service. 
More recently on March 13, 1989, during a large magnetic storm accompanied by vivid auroras visible as far 
south as Hawaii and Cuba, GICs hit power lines from the Hydro-Québec power network. This led to a blackout 
affecting 6 million people and losses of more than CAD 10 million. The increasing dependence of society on 
electricity and electronics, and of course satellites (e.g. GPS timing signals), leads to a growing exposure to 
strong space weather events, amplified by over-aged or sometimes degraded high-voltage equipment. >

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