There was no material association between childhood leukaemia and distance to nearest overhead power line of any voltage.

https://www.nature.com/articles/s41416-018-0097-7

In the past six months, transmission lines have been destroyed by hurricanes in Puerto Rico, singed by wildfires in California, and bitterly opposed by residents in Utah and Pennsylvania who want to stop utilities from building more.

Such problems have grid operators literally thinking deeper. Increasingly, utilities in the United States and elsewhere are routing power underground. Puerto Rico’s grid rebuild is a prime example: A proposal, crafted by an industry-government consortium late last year, calls for “undergrounding” transmission to harden a power system still recovering from Hurricanes Irma and Maria.

By heading below ground, transmission grids are following a path laid by their lower-voltage cousins—distribution grids. In some cities, power distribution occurs entirely out of sight. This is possible thanks to specialized cables

Utilities have been slower to bury transmission because of the expense

Each cable must be shipped in roughly 1-kilometer-long links and stitched together on-site, adding further to the tab.

Tally it all up, says Hall, and underground transmission costs roughly 5 to 10 times as much per kilometer as overhead circuits. “Every utility in the United States has underground distribution. But not every utility has underground transmission,” he notes.

Despite the expense, utilities are now investing more in underground transmission, prodded by regulators and public outcry. Denmark was among the first to mandate it in 2008, requiring most new AC and HVDC transmission to be routed underground, with the exception of the highest-voltage, ­400-kilovolt AC lines.

In 2015, Germany mandated underground transmission for HVDC systems unless they could be strung alongside existing power lines.

For all its benefits, Laun says undergrounding has also caused new headaches for transmission operators. Farmers can plant and plow over buried cables, but ­Germany’s farm lobbies are concerned with potential soil impacts from cable heat and altered drainage, and have demanded compensation.

Blown fuses on one of its 12.5 kV distribution feeders had shut down part of the plant. Unfortunately, it happened around noon on two days in a row. Power had been restored without finding any problems on both days. Pressure was mounting to find and correct the problem before noon the following day.

All the evidence suggested this was the arc location and a classic example of what one might expect to find in the aftermath of an arcing fault.

Animals around the world could be scared away from power cables because these give off UV flashes invisible to humans, scientists have said.

The findings, published in the journal Conservation Biology, claimed habitats and migration could be disrupted.

The flashes, or corona, occur when charge builds up in a cable and is released into the air.

The first animal to reveal its UV sensitivity was the reindeer. And, as the researchers explained, reindeers’ avoidance of the power lines running across the Arctic tundra was part of the inspiration for this project.

coronas “happen on all power lines everywhere”

A German student has designed an energy harvester that derives energy from electromagnetic fields in the air to recharge small batteries and appliances. Dennis Siegel, who is studying digital media at the University of the Arts in Bremen, Germany, outlines the design of the harvester on his website.

With the energy harvested, it’s possible to charge a small battery in just a day depending on the size of the electromagnetic field.

National trends

Municipalities have passed laws requiring new distribution facilities to be
placed underground.
- For aesthetic reasons
- To increase property values (5-10% according to some studies)

Cost covered by developers and ultimately paid by property owners.

Provide better protection from storm damage and improve reliability of power supply

Underground construction CAN improve the reliability of the electric power system by minimizing damage to the system from:
- High winds
- Ice and snow storms
- Falling trees

Underground Construction is NOT Immune from All Storm Damage
- Flooding
- Hurricane Damage
- Earthquake Damage
- Lightning Damage
- Rodent and Human Damage (dig up)

The main argument against constructing underground systems is usually financial. But costs are not the only limitation.

The laws of physics limit how physically long a power line can be.
- will severely limit high voltage underground cable systems (especially on voltages 100 kV and up)

Capacitance causes current to flow even when no load is connected to the cable.

Replacing overhead with underground lines will also change other characteristics of the line and connected power system.
- Resistance will go down (probably beneficial)
- Inductance (resistance to the flow of AC current) will also go down.
- Voltage regulation will become much more difficult.
- Line losses may increase and efficiency might become worse.
- Time to repair the line will be much longer

Underground transmission line construction may be 20 times the cost of overhead construction. (A $3 million/mile line becomes $60 million/mile.)

Currently underground AC transmission is primarily used only where nothing else will do.

A move to install underground transmission cables may require a conversion from AC to DC transmission.

Large-scale underground high voltage power line projects constructed since 1980

Askon Consulting Group (2008):
– Underground cables are much safer
than overhead lines. No electric fields
are emitted from buried cables, and
most importantly, the magnetic field
is greatly reduced both in intensity
right over the line and in distance of
impact.
– Underground cables enhance power
grid security and reliability and give
improved performance, compared to
overhead lines.
– Underground cables are significantly
more reliable.
– Underground cables are significantly
more efficient.
– Underground cables are affordable
compared to overhead lines. There
is a higher initial capital cost, but this
difference is cancelled out by the
much higher and costly electricity
losses from overhead lines over the
life of the line. When this is taken into
account, plus the lengthy planning
delays, property devaluation, impacts
on tourism and higher maintenance
costs associated with overhead lines,
costs of underground and overhead
lines are almost equal.