POWER January 2016 - 12

Grid Resiliency: A Strategy
for Keeping Transformers
Safe
Grid resiliency has become a widely discussed
topic recently. Experts have been
called before congressional hearings to
testify on the topic, and close calls-including
a massive solar storm that missed
Earth by a matter of days in 2012-have
been highlighted in the news. Natural
disasters, such as Hurricane Sandy, and
physical attacks, such as the rifle assault
on the Metcalf substation near San Jose,
Calif., have also brought to light grid vulnerabilities.
Mitigating
Risk Is Important
Most people are not prepared for a blackout
that lasts longer than a day or two,
but utilities must consider this possibility
and prepare for it. A report published by
the Electric Power Research Institute for
the U.S. Department of Homeland Security
states that power transformers are critical
devices when it comes to natural disasters,
attacks, or unintentional accidents.
The findings are troubling once a person
realizes that 70% of the grid's transmission
lines and large transformers are more
than 25 years old, with the average age
of power transformers in the U.S. being
40 years. Old age can lead to an increase
1. Locating vulnerabilities. Comprehensive
condition assessment and other
services help to prevent unpredicted failures.
Courtesy: Siemens Energy Management
of weather-induced outages and adds to
failure risk during normal operation.
The transformer purchasing process is
not simply a case of taking a product off
of a shelf. Transformers are highly individualized,
tailor-made products that are designed
and manufactured for very unique
purposes at strategic nodes in the transmission
grid. The procurement process
adds complexity to the manufacturing
task, which is still mostly done by hand,
using raw materials sourced from all over
the world. The end product is in some ways
a masterpiece of electrical equipment.
Units are very large and heavy-made
mainly of steel and copper-so shipping
them is another undertaking that cannot
be done in the blink of an eye. Less than
one-third of units larger than 60 MVA are
made in the U.S. As such, U.S. reliance
on imports makes quick delivery difficult,
especially when it comes to extra-highvoltage
power transformers (voltage levels
above 345 kV).
A Three-Pronged Strategy
Siemens has developed a transformer strategy
that encompasses several facets of
transformer technology and also contains
completely new features and products designed
to secure resiliency for U.S. utilities.
Preventive and protective measures can
be taken to lower the risk of operational
equipment failures and failures caused by
natural disasters or human attacks.
Prevent. Preventive measures comprise
all kinds of service to the existing
transformer equipment. Condition assessment
(Figure 1) helps keep track of the
status of every single unit operated in the
transformer fleet. As with most processes
in the modern world, the preventive resiliency
strategy is based upon an intelligent
database that sums up information on the
transformers in the fleet.
Siemens combines data from several
measurements such as oil analysis, thermal
graphics, and electrical tests to form
a complete picture of all associated units.
The transformer operator is able to view
a simple traffic-light graphic to identify
which transformers are likely to fail or
need service. Retrofit and repair might
give some units longer life with decreased
operational risk.
Protect. While prevention is a common
strategy to handle operational risks, protecting
devices that require investment is
a second method. Protective measures can
be added to all new units that are ordered,
and some can also be installed to upgrade
existing units.
To shield units from human attacks,
Siemens has completed testing with different
kinds of rifles to find a material
that prevents external harm to the transformer
from bullets. The outcome is a
cutting-edge solution with special armor
panels, similar to tank-mounted sound
panels, installed externally at the tank.
2. Sun storms place the grid at risk. Coronal mass ejections-commonly known as
solar storms-can create magnetic disturbances on Earth, which induce currents on the electric
grid with the ability to damage or destroy key transformers over a large geographic area. Courtesy:
Siemens Energy Management
12
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POWER January 2016

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