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On July 19th, 2012 the Solar Dynamics Observatory
captured this incredible footage of Sun. This
clip was recorded with 1 frame every 12 seconds.
Meaning every second of this video represents
6 minutes of real time. This event began with
an intense solar flare. A sudden release of
magnetic energy sending ungodly amounts of
energy, in the form of radiation and light,
into space. This particular solar flare was
followed by a coronal mass ejection, a massive
twisted bubble shaped eruption firing a colossal
cloud of electrically charged particles into
space, which can disrupt interplanetary magnetic
fields and interact with Earth’s magnetic
field in what is known as a geomagnetic storm.
Finally, as the solar storm subsided and the
eruption bubble began to cool, we were treated
to one of the most mesmerizing events in our
solar system. Coronal Rain. Where the remaining
charged plasma cools and falls back to the
surface of the sun. Forming these beautiful
cage like structures as the particles follow
the Sun’s magnetic field lines back down.
[1]
An astoundingly beautiful event, but had it
happened just a week earlier the flare up
would have been pointing squarely at earth
and could have had some nasty consequences
[2], and it wouldn’t have been the first
time a solar storm affected life negatively
on earth.
In 1859 a similarly powerful solar flare,
called the Carrington event, did hit earth.
Treating people as far south as the Carribean
to the northern lights, while also knocking
out major telegraph systems in both Europe
and North America.[3]
In some cases the geomagnetic disturbances
were so strong that they sparked fires, shocked
telegraph operators and even allowed the telegraph
system to work with no power.
In 1989 a large geomagnetic storm caused a
blackout in Quebec after the coronal mass
ejection managed to trip circuit breakers
in their grid. Leaving 6 million people without
power for 9 hours.
So, clearly these storms have the power to
really mess with vital technologies that keep
our society moving, but how exactly do they
do it? [4][5]
To understand this we first need to understand
some basics of how electricity is generated
in power stations. As you probably know already,
we generate electricity by moving a wire through
a magnetic field, or vica versa. The basic
law behind this is called Faraday’s Law[6],
which states that “any change to a magnetic
field surrounding a coil of wire will cause
an electromotive force to be produced, otherwise
known as a voltage. The voltage can be considered
the force pushing electrons through a wire,
if they are free to move a current is produced.
The current is a measure of the rate of flow
of electrons.
We generally generate electricity by rotating
a coil of wire inside a magnetic field. We
do it this way simply because rotational motion
is efficient with no changing of direction
like linear motion forcing us to decelerate
and lose inertia, but we can generate currents
other ways, like dropping a magnet through
a coil of wire. This moves the magnetic field
itself, rather than the coil of wire.
So stationary wires can generate currents
when a magnetic field changes around them,
and our electricity grid happens to be made
up of millions of kilometres of stationary
wire. We have effectively turned the planet
into a massive electric generator by surrounding
the earth’s magnetic core with all this
conductive wire, the only thing that’s missing
is a large shift in the earth’s magnetic
field. Unfortunately for us, that is exactly
what coronal mass ejections do to Earth’s
magnetic field.
On March 10th 1989, the sun blasted a cloud
of charged particles so large that it dwarfed
our planet in size. It raced through space
at 450 kilometres per second, before crashing
into the Earth’s magnetopause. The boundary
between Earth’s magnetosphere and interplanetary
space, sitting about sixty five thousand kilometres
above Earth. It struck with such force that
it literally shook and trembled our planet’s
protective magnetic field. [7]
The first phase of this is called the sudden
storm commencement where the coronal mass
ejection first arrives at our magnetopause
causing the magnetosphere to compress on the
daylight side of the earth. Resulting in a
sudden increase in the intensity of the geomagnetic
field in that region. The next phase results
in a decrease in intensity as an electric
current induced in the magnetosphere and ionosphere,
pushes the boundary of the magnetosphere outwards
and results in a decrease in geomagnetic field,
and the geomagnetic field can continue to
vary from hours to days after this initial
burst.
So these geomagnetic storms cause shifts in
the earth's magnetic field which drives induced
electric currents in anything capable of carrying
them. That can be the ground, ocean, or our
electricity grid. If those currents enter
our grid they can wreak havoc on essential
infrastructure.
So it seems like a disaster waiting to happen.
What are we doing to prepare for the worst?
Unsurprisingly, one of the largest industries
on Earth has thought pretty hard about this
problem and has set out guidelines on how
to deal with such an event. As mentioned in
my recent solar sailing video, we currently
have several satellites parked in lagrange
point one. A point between the Sun and the
Earth where a satellite can maintain a constant
position, and thus allow us to receive advance
warning of any coronal mass ejection. This
point confused many commenters, who assumed
solar flares were simply bursts of radiation
travelling at the speed of light, and thus
no speed of light communication method could
give us any advance warning.
But these eruptions of particles travel at
a fraction the speed of light, about 0.15%
the speed of light for our above 1989 event.
(1.48x10-3) And thus can provide up to an
hour of warning time.
We also have some other less definitive warning
signs that the Sun may point a coronal mass
ejection in our direction by observing sunspots,
which are dips in brightness on the surface
of the Sun, which occur as magnetic energy
bottles up in the solar atmosphere before
being suddenly released. These sunspots come
in cycles of low and high activity every eleven
years.
This warning time can provide grid operators
a little time to prepare for any anomalies,
but they are more useful to GPS satellites
whose accuracy is affected by ionosphere disturbances
as their radio waves refract through it [10]
and thus need to adjust their signal to compensate
for. In severe solar storms these warnings
would give industries where GPS malfunction
could lead to loss of life, like airliners,
vital time to prepare.
To protect our grid, it’s really a matter
of designing it in a way to be able to deal
with these induced currents. Let’s take
a deeper look into that 1989 blackout to see
what really happened and see how grid operators
can prepare.
The first malfunction occurred as a result
of transformers becoming saturated. Power
transformers are placed at internals between
high-voltage transmission lines and power
generators or local distribution lines to
step-up or step-down voltages.
So what does saturation mean? Transformers
work by winding wire from the source around
a ferromagnetic core. This generates a magnetic
field inside the core which can in turn induce
an electric current in our secondary winding.
If our primary wire has more windings that
the secondary wire it will step down the voltage,
and if the secondary wire has more windings
that the primary wire it will step up the
voltage. These transformers form an essential
part of our grid, but when the core becomes
saturated it interferes with their operation.
Saturation just means that the magnetic core
has reached is maximum magnetic flux capabilities,
so an increase in current and voltage will
not result in a subsequent increase of magnetic
flux. If this happens, the voltage induced
in the secondary winding can no longer match
the waveform as the voltage powering the primary
coil. So the waveform of the secondary wire
becomes distorted. [12]
When this happened in Quebec the grid voltage
became unstable causing protective relays
to disconnect five high-voltage transmission
lines including one from a hydroelectric facility.
[12]
As the hydroelectric facility was disconnected
it experienced a rapid loss of load, meaning
it’s power had nowhere to go, which caused
the voltage to suddenly increase which damaged
two step-up transformers as a result of excessive
heating.
Saturated transformers are the route cause
of most grid malfunctions during magnetic
storms. However In 1989, the knock-on effect
of these waveform distortions is what caused
the majority of the damage, as electro-mechanical
protective relays tripped and cut off sections
of the grid. [13]
Electro-mechanical relays are essentially
switches that turn on and off when an electric
current flows in the control circuit creating
a magnetic field in an electromagnet and pulls
an armature down to complete a circuit in
a secondary circuit.
These can be combined to form logic gates
that are more complicated, but are in-general
not programmable to deal with anomalies like
distorted waveforms caused by transformer
saturation.
Today we have much smarter microprocessor
technology that can be programmed to deal
with these issues better and maintain grid
stability, but because of the electro-mechanical
relay’s reliability and long service life,
there are still thousands of these older devices
in the grid infrastructure, but they are slowly
being phased out for more modern technology
especially in northern and southern regions
more susceptible to geomagnetically induced
currents.
We can also block geomagnetically induced
currents because they are direct currents,
where our normal power is alternating current.
Capacitors can only transmit alternating current
because capacitors don’t physically complete
circuits. They are just large stores of positive
and negative potentials that switch every
time the current flips. DC currents don’t
flip and thus a capacitors do not allow DC
currents to flow. So we do have options to
minimise the effects of these disturbances.
I expected this to be a dramatic video that
would drag viewers in on fear of their grid
failing from solar flares. You can probably
tell from the shift in tone from the start
of the video to the end, as I researched this
topic more thoroughly. It really seems like
mainstream media’s fear mongering on the
effects of solar storms on our electricity
grid is completely overblown. With only one
notable blackout caused by geomagnetically
induced currents, that with today’s technologies
was completely preventable, there isn’t
much evidence that grid operators need to
spend vast amounts of money on these systems.
Although DC blocking capacitor systems have
been installed in countries in northern locations
more at risk of geomagnetic disturbances,
like Finland and England. [13]
In the end the only reason electricity grid
operators have not implemented these DC blocking
devices and other mitigating technologies
is because they would cost more to model and
implement than the risk geomagnetic disturbances
actually pose to the grid. In reality, the
risk from hurricanes and other terrestrial
weather events pose a much bigger risk to
our electricity grid.
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