Protection of Critical Transformers
from High-Energy Attacks
By
Andrew P. Lawless, P. Eng.
Siemens Energy, Inc.
Dipl. Ing. Helmut Pregartner
Siemens Transformers Austria
GmbH & Co KG
Background
In 2013 a sniper attack with a high-powered firearm caused significant damage at a PG&E
substation. Several high voltage transformers and reactors were damaged. The attack was
treated as a possible terrorist attack. On March 7, 2014, the Federal Energy Regulatory
Commission (FERC) issued Docket No. RD14-6-0001 calling on owners and operators to assess
risks for critical facilities, evaluate potential threats and vulnerabilities, and develop and
implement corresponding security plans. The North American Electric Reliability Corporation
(NERC) was given 90 days to submit proposed standards. NERC CIP-014-1 is the response to
the FERC order.
The White House launched a Quadrennial Energy Review (QER) in January 2014 for which the
first report will focus on transmission and distribution infrastructure. As part of this review,
NEMA participated on behalf of its member manufacturers and submitted its recommendations
in June.
In April 2014, the National Electrical Manufacturers Association (NEMA) established a series of
committees to develop recommendations for the QER. One committee dealt with grid security,
which includes physical security and the hardening of transformers and substations against
physical attack.
Problem Statement
The existing NERC and IEEE standards and guidelines for the physical security of substations
make little or no mention of an intentional attack from far outside the substation perimeter or the
range of substation surveillance and detection. These documents focus on assessing, preventing,
detecting, and responding to unauthorized entrance into substations. An attacker using a highenergy kinetic weapon (rifle) could render substation security measures ineffective, cause
significant damage to equipment, and then withdraw without being detected or apprehended.
There is no specific standard or guideline for the hardening of critical substation equipment
against such attacks.
Vulnerability and Risk Assessment
The existing guidelines from NERC follow a basic approach to assess vulnerabilities and
prioritize countermeasures to mitigate the identified vulnerabilities.2
1. Identification of assets and the impact of their loss.
In this case, the assets are large power transformers and reactors, the loss of which can result
in significant outages with consequent economic loss and social disturbance.
2. Identification and analysis of vulnerabilities.
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Large power transformers and reactors are heavy and bulky yet very susceptible to physical
attack. They are typically the largest piece of electrical equipment in any station or
substation. The least vulnerable part would be the tank and casing, which is normally
composed of A-36 mild steel with a thickness of approximately 3/8 inches. The remaining
components are far less resistant to physical attack. Porcelain bushings and sheet metal
radiators would be considered the most vulnerable components.
3. Assessment of risk and the determination of priorities for the protection of critical assets.
The baseline risk will be modeled after the Metcalf incident and consider the maximum
reasonable limits in terms of weaponry and the minimum distance from the substation where
an attacker is likely to operate.
4. Identification of countermeasures, their costs, and trade-offs.
Countermeasures will consider the transformer and reactor as a system with subsystems and
components. The countermeasures will consider direct hardening of the equipment in
addition to the general substation security measures to protect all equipment. Costs and
trade-offs are too preliminary at this time to fully evaluate.
Determining the Level of Threat and Protection
The analysis of the physical hardening of transformers and substations will be limited to threats
from high-energy kinetic weapons (firearms) operated from outside the substation security fence.
The intent is to model the threat and recommend the necessary protection based on the PG&E
Metcalf incident. If there is no restriction to the type of kinetic or physical attack, then there
could be a myriad of possible threats using vehicles, aircraft, explosives, missiles, incendiaries,
remote control drones, intentional flooding, intentional shorting of equipment, or any other such
mode of attack.
Figure 1
AK-47 (7.62x39mm) of the Type Likely Used in the Metcalf Attack3
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Extremely powerful rifles such as the Anzio Ironworks 20mm Take-Down Rifle are
commercially available.4 These rifles are extremely expensive, rare, and custom-built. A special
category of Federal Firearms License for a destructive device is required to obtain one.
Therefore, it will be considered outside the realm of a practical threat. If not, then there is
practically no limit to the kind of high-energy kinetic weapon that should be evaluated as a
threat.
Figure 2
Anzio Ironworks 20mm Take-Down Rifle in Firing Position5
A class of relatively uncommon, yet relatively easy to obtain, commercially available highpower rifles are those using the .50 BMG round. These represent the likely maximum threat for a
ballistic attack. Domestically manufactured and commercially available rifles include those built
by Barrett Firearms Manufacturing,6 Anzio Ironworks Corporation,7 E.D.M. Arms,8 Spider
Firearms,9 Bushmaster Firearms International,10 McMillan Group International,11 Desert Tech,12
ArmaLite, Inc.,13 Bluegrass Armory,14 and Serbu Firearms, Inc.15 The prices for .50 BMG rifles
range from approximately $3,500 upwards, and .50 caliber armor-piercing M2 rounds are
commercially available for as little as $1.25 each. Using this rifle as the baseline threat would
represent the very absolute limit for the most critical substations.
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Figure 3
Barrett Model 99 Using the .50 Caliber BMG Round16
Figure 4
E.D.M. .50 Caliber BMG Windrunner M9617
Even though smaller caliber weapons may not have the same degree of power or penetration as
.50 BMG rifles, there is a range of more commonly and commercially available types. The most
popular rifles are based on the following rounds:
•
•
•
•
•
•
•
•
•
.22 Long Rifle
.17 HMR
.223 Remington
.243 Winchester
.260 Remington or 6.5x55 SE
.270 Winchester
7mm Remington Magnum
.30-30 Winchester*
.308 Winchester*
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•
•
•
.30-06 Springfield*
.375 Holland & Holland Magnum*
.458 Winchester Magnum*
The last five (*) rounds are used in firearms based on large caliber hunting or military rifles.
Other specialty and custom-built rounds known as “wildcats” are also available. These would
include high-power versions of .338, .408, .416, .510, and other large caliber rounds (for
example, Lapua, Win Mag, CheyTac, Barrett, Nitro). These offer any attackers extreme
penetrating power beyond 500 yards, allowing them to do considerable damage to substation
equipment from beyond the range of substation surveillance and detection. However, even the
smaller .22 rounds are capable damaging sensitive and delicate components of major equipment
such as bushings, arresters, instruments, and radiators.
Figure 5
Comparison of Cartridge Sizes18
It is important to note that complete penetration of electrical equipment by high-energy
projectiles is not necessary to cause catastrophic equipment failure. If a high-energy projectile
strikes a rigid target but does not penetrate, the momentum of the impact can be sufficient to
cause particles from the opposite side of the target to break free. The particles can be projected
at very high velocities and cause considerable damage. This effect is called ballistic spalling. In
the case of high voltage apparatus, spalling from metal tanks of transformers and breakers can
cause metallic particles to spray into the high voltage fields or transformer windings, potentially
causing catastrophic failure from internal flashovers.
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Video 1
Simulation Showing Spalling Effect19
Development of Countermeasures
It is necessary to understand the damage that can be inflicted by the likely maximum threat
ballistic attack to properly develop countermeasures. The characteristics of a .50 BMG M2 AP
round fired from a high-power rifle are shown below.20
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Figure 6
Data Sheet for .50 Caliber Ball, M2 Armor-Piercing Round
The velocities at different ranges for the .50 BMG M2 AP are given by the Department of
Defense MIL-STD-662F.21 Likewise, the level of protection against the same round according
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to its velocity and the angle of impact (either 0° or 30°), is given by the Department of the Army
MIL-DTL-12560K (MR).22 Note that these standards are based on military grade armor.
Substituting the armor material with composite, A36, aluminum, or other materials would
require adjustments in calculations or validation.
Taking the two aforementioned standards allows us to create a table based on the distance,
velocity, angle, and thickness of military plate required to prevent complete penetration.
Table 1
Minimum Armor Thickness for .50 Caliber M2 AP at Distance, Velocity, and Obliquity
Distance
Yards
Velocity
(ft/sec)
0
100
200
300
400
500
600
700
2845
2710
2580
2455
2340
2220
2100
1985
Min. Armor
0° Obliquity
inches
1.115
1.020
0.935
0.855
0.790
0.720
0.655
0.6251
Min Armor
30° Obliquity
inches
N/A2
0.610
0.575
0.540
0.505
0.470
0.440
800
900
1875
1765
0.625
0.6251
0.405
0.375
0.3551
1000
1665
0.6251
0.3551
1
1. Specification requirements for ordered thickness begin.
2. Beyond range of specifications.
From the table we can see that an attacker with the .50 BMG round can cause significant
penetration at 1,000 yards and probably far beyond. Assuming that A36 mild steel is 20%
weaker than armor plate, a transformer main tank with 3/8 inch armor could quite feasibly be
penetrated at 1,000 yards. Plate type radiators, typically made from 18 gauge steel, could likely
be damaged from the 2,500 yard maximum operational range of a .50 BMG rifle.
Countermeasures per NERC and IEEE
The NERC Security Guideline for the Electricity Sector: Physical Security23 describes solutions
to physical attack based on a combination of “protection in depth” and “crime prevention
through environmental design” (CPTED). The “protection in depth” concept depends on
delaying the advance of the attacker until a response can be made. This would imply that in a
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kinetic attack, the transformers and other critical components would have to be sufficiently far
away from the perimeter of the station to make it difficult for an attacker to damage them. This
puts the transformer at 2,500 yards from the perimeter, which is not very practical.
The “crime prevention through environmental design” concept is mostly based on measures to
prevent access, provide surveillance, and report intrusion or attack. The guideline gives these
recommendations:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Install fencing, walls, gates, and other barriers to restrict access.
Limit access to authorized persons.
Take access control measures.
Use alarm systems to monitor entry.
Use perimeter alarm systems to monitor forced intrusion.
Use alarms, CCTV, and other security systems reporting to an attended central security
station.
Deploy guards.
Install vehicle barriers.
Install adequate lighting.
Install signage to warn potential intruders.
Implement a comprehensive security awareness program.
Deploy roving security patrols or fixed station security staffing.
Install a projectile barrier to project vulnerable equipment or personnel.
Conduct security surveys and other risk assessment programs.
The only recommendation that would be effective against high-energy kinetic weapons is the
creation of projectile barriers to protect equipment or personnel, but little detail to the
requirements is given. Barriers of sufficient dimensions and material would have to be placed
around the transformers to protect them. The other recommendations do little or nothing to
prevent a dedicated attacker far outside the perimeter of the station.
The IEEE Standard 1402-200024 is also primarily concerned with intrusion mitigation. There is
some detail about foreign objects and projectiles, including the mention of gunshots. However,
only one applicable recommendation is given for direct protection against gunshots :
“Solid masonry or metal walls may provide an additional degree of security. Solid walls
are generally more difficult to breach and also prevent direct line-of-sight access to
equipment inside the substation. Solid walls may prevent external vandalism, such as
gunshot damage, depending on the height of the wall, surrounding terrain, and elevation
of equipment inside the substation.”
This recommendation highlights the advantage of preventing line-of-sight (LOS) to critical
components. Typically, an attacker will only target what can be directly seen. However, the
NERC and IEEE standard do not give much guidance about what to do in case building barrier
walls or relocating equipment within the station is impractical. Walls cannot always be built to
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the maximum height of the bushings and 360 degrees around the transformer without interfering
with the overall layout of the station. Building a complete wall of the required dimensions
around the entire station may also be prohibitive.
The U.S. Marine Corps gives some practical guidelines on the thickness and types of walls to
prevent penetration of various rounds, including the .50 caliber M2 AP.25 The Military
Operations on Urbanized Terrain (MOUT) manual describes the .50 BMG round as a very
effective penetrator of walls, although it may take more than one round to breach. Table B-6
indicates that something on the order of 10 to 12 inches of brick or reinforced concrete is
required to stop this round. A cinder-block wall, two or three blocks thick and filled with sand,
represents a good barrier against this form of attack.
On November 20, 2014, FERC issued a notice of final rule on the approval of the NERC CIP014-1 standard for physical security.26 The purpose of CIP-014-1 is
“To identify and protect Transmission stations and Transmission substations, and their
associated primary control centers, that if rendered inoperable or damaged as a result of a
physical attack could result in widespread instability, uncontrolled separation, or
Cascading within an Interconnection.”27
The standard is applicable to transmission facilities 200 kV and above, with some noted
exceptions, and was developed to address directives from NERC to
“identify and protect facilities that if rendered inoperable or damaged could result in
widespread instability, uncontrolled separation, or Cascading within an
Interconnection.”28
The standard is not intended to detail specific threats or countermeasures. Rather, it outlines a
process and procedure for each transmission owner to conduct initial and periodic risk
assessments, have the risk assessment evaluated by a third party, identify potential threats and
vulnerabilities to physical attack, implement appropriate security plans, and have these plans
verified by a third party. The CIP-014-1 standard is novel as it makes specific reference to
hardening, either of the entire transmission asset or of specific components.
“While most security measures will work together to collectively harden the entire site,
some may be allocated to protect specific critical components. For example, if protection
from gunfire is considered necessary, the entity may only install ballistic protection for
critical components, not the entire site.”29
Countermeasures for Direct Hardening
Siemens recommends the specific and direct hardening of power transformers, in addition to
measures outlined by other standards, where it has been determined that the transformer or
station is a critical asset and where existing measures are insufficient against a high-energy
kinetic attack.
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Transformers can be analyzed as a system of components rather than a single piece of
equipment. This gives a method to determine the vulnerabilities of each component, the
associated risk of damage, and the effectiveness of countermeasures. 30 The table below follows
this approach for transformers.
Table 2
Measures Against High-Velocity Kinetic Attack
Measure
Component
(1.1.1.1)
Bushings (1.1.1)
(1.1.1.2)
Arresters (1.1.2)
(1.1.3.1)
Ground Insulators (1.1.3)
(1.1.4.1)
Turrets (1.1.4)
(1.2.1.1)
Main Tank (1.2.1)
(1.2.2.1)
Conservator (1.2.2)
(1.2.3.1)
Load Tap Changer (1.2.3)
(1.2.4.1)
Valves (1.2.4)
(1.2.5.1)
Protection Devices (1.2.5)
(1.3.1.1)
Radiators (1.3.1)
(1.3.2.1)
Fans and Pumps (1.3.2)
(1.4.1.1)
Main Control Cabinet (1.4.1)
(1.4.2.1)
LTC Control Cabinet (1.4.2)
(1.4.3.1)
Control Cable Connections (1.4.3)
Subsystem
System
Connections (1.1)
Main Unit (1.2)
Transformer (1)
Cooling (1.3)
Controls (1.4)
Bushings (1.1.1)
There are currently no technologies available to directly harden an HV air-to-oil bushing and
prevent failure from a kinetic attack. Indirectly, bushings can be replaced with SF6-to-oil or oilto-oil types which can then be connected via SF6 bus duct or cable connections that can be either
buried or hardened. This option represents a significant modification to an existing station.
Many LV bushings on GSU transformers are already in bus ducts, so these ducts could be
armored without too much difficulty.
Apart from the above, the most practical solution for oil-to-air bushings is to replace porcelain
bushings with polymer or composite RIP oilless-type bushings so that even if the polymer
insulator is penetrated, catastrophic failure will not lead to fire from ignition of the oil. Special
attention to the bottom end of the bushing is required so that internal contamination and damage
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to the coil and coils is avoided and field replacement can be completed quickly. Having spare
bushings available would allow for fast recovery.
Arresters (1.1.2)
Similar to bushings, the best recommended practice is to replace all porcelain arresters with
polymer or composite types. This prevents damage from flying porcelain that can cause
cascading damage to other transformer components (especially bushings) and physical injury.
Having spare arresters available would allow for fast recovery.
Ground Insulator (1.1.3)
Many transformers have ground busses that run along the tank wall. These ground busses are
used to connect the grounding of arresters. They are connected to the wall via insulators. Older
insulators may be made of porcelain and it is recommended that they be replaced with epoxy or
other similar material insulators that are shatter-resistant.
Turrets (1.1.4)
Bushing turrets can be directly hardened using appliqué armor. Appliqué armor (armor mounted
over an existing structure) of the plate or composite type designed to withstand the maximum
impact can be added. Sufficient stand-off distance and an anti-spalling layer is recommended.
Main Tank (1.2.1), Conservator (1.2.2), and Load Tap Changer (1.2.3)
The portions of the main tank, load tap changer, or conservator that are exposed to an attacker’s
line of sight can be protected with appliqué armor. The armor could be of the plate or composite
type. There must be sufficient stand-off distance from the main tank and an anti-spalling layer to
protect against secondary penetration or damage. Whenever possible, it is recommended that
any appliqué armor be offset approximately 30 degrees or more from the perpendicular of the
surface being protected to increase ballistic withstand. This will deny an attacker a
perpendicular trajectory to both surfaces from any angle which would allow maximum
penetration. Attaching appliqué armor would be similar to the attachment of noise reduction
panels.
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Figure 7
Transformer Tank Made with Bullet-Resistant Material
Siemens has already developed steel panels to reduce noise emissions from transformers.
Modified designs for ballistic protection of transformer and reactor tanks are being tested. A
combined low noise and armored tank solution could potentially result from the experiments
being conducted.
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Figure 8
Transformer with Tank-Mounted Sound Panels
The results from testing of the armored panels will be compared with the impact resistance of the
standard 3/8 inch tank design material. This will allow for the total impact resistance of the tank
plus the armored panels to be established. A safety factor may also be included in future tank
designs with the results from these tests.
The bulletproof panels are to be tested with military weapons of various calibers at an official
testing center for weapon development, material testing, and safety technology. All testing will
be conducted in accordance with MIL-STD-662F31 or VPAM APR 2006 (Edition: 2009-0514).32 An example of the bulletproof panels can be seen in Figure 9.
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Figure 9
Steel Panels Tested as Armor Plating for Tanks
Valves (1.2.4) and Protection Devices (1.2.5)
Valves, instruments, and protection devices should have resistant metal covers to protect them
from line-of-sight attacks while being removable for maintenance.
Radiators (1.3.1) and Fans and Pumps (1.3.2)
Radiators and fans cannot be directly hardened because adding armor or obstructing airflow
impairs their operation. Composite or plate armor barriers should be mounted with sufficient
standoff distance to allow for proper airflow. Figures 10 and 11 give an example of this
arrangement.
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Figure 10
Side View of Bullet-Resistant Tank Design with Protected Radiators and Conservator
Figure 11
Top View of Design Including Cooling Equipment
Tank-mounted radiators require a significant structure around the applicable part of the main
tank to properly protect it. Unless armor panels are made of light, composite materials, they will
require separate mechanical structures. Separate cooling, especially using dedicated OFAF
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coolers, are much easier to locate out of the line of sight or to protect using barriers or appliqué
armor.
Figure 12
Large Power Transformer with Separate OFAF Cooling Banks
Main Control Cabinet (1.4.1), LTC Control Cabinet (1.4.2) and Control Cable
Connections (1.4.3)
Similar to the main tank, appliqué armor can be mounted on the control cabinets. Conduits for
critical wiring, even if buried, should be protected from cutting with standard tools and should
withstand ballistic impacts.
Comparison of Solutions
Ballistic Curtains
Bulletproof fabrics are commercially available and are normally based on NIJ Standard-0101.04,
“Ballistic Resistance of Personal Body Armor,”33 intended for personal protection, such as
bulletproof vests. These fabrics typically last 10 years under normal wear and tear for vests, but
there is no clear indication of their life under long-term exposure to environmental conditions.
Ballistic curtains may require regular maintenance to maintain their ballistic protection level.
Normally flexible fabrics only offer protection levels IIA (9 mm; .40 S&W) to III (.357 SIG; .44
Magnum). Level III (Rifles) and IV (Armor Piercing Rifle) provide protection to .30 Cal M2 AP
but normally use rigid plates inserted into the fabric.
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“Body armor designed to defeat rifle fire is of either semirigid or rigid construction,
typically incorporating hard materials such as ceramics and metals.”34
“Type IV body armor provides the highest level of protection currently available.
Because this armor is intended to resist “armor piercing” bullets, it often uses ceramic
materials. Such materials are brittle in nature and may provide only single-shot
protection, since the ceramic tends to break up when struck. As with Type III armor,
Type IV armor is clearly intended only for tactical situations when the threat warrants
such protection.”35
Level IIIA blankets cost approximately $75 per square foot36 and Level III and Level IV plates
without fabric holders cost approximately $150 per square foot.37
In addition to the curtain material, some sort of supporting structure or method of fastening is
required, either directly on the tank or set off from the tank. Issues such as dielectric clearance
and airflow would need to be considered in addition to the possibility of wind loads on any
supporting structure.
Masonry Walls
Masonry walls or fire barriers are commonly used around transformers to prevent collateral
damage and the spread of fire in the case of violent transformer failure. Their use is not
universal, however, and many transformers are not protected by any sort of barrier.
In addition to protection against blast and fire, these walls can provide some degree of ballistic
protection. Some precast concrete barrier manufacturers advertise that their walls have been
tested for ballistic protection.
According to military and paramilitary sources, single layer concrete block can be easily
penetrated with .30 caliber and .50 caliber M2 AP rounds. For transformer ballistic protection,
these blocks may have to be reinforced with concrete to achieve the desired level of protection.
Masonry or concrete walls require significant space around the transformer to allow for cooling
and access, which may make retrofitting difficult in existing substations due to space limitations.
Utility brick walls are $20 to $25 per square foot.38 Precast concrete walls 6 inches thick are on
the order of $16 to $19 per square foot.39 The 6-inch thick concrete walls are normally sufficient
to stop most .30 caliber rounds, although a .50 caliber round can penetrate thick layers of
concrete.
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Comparison of Solutions
Table 3
Comparisons of Antiballistic Solutions
Protection Level
Maintenance-Free
Durability
Ease of Installation,
New Transformer
Ease of Installation,
Existing Transformer
Installation Time
Space Requirements
Cost per Square Foot
Armor Panels
30 or 50 Cal
Lifetime
Lifetime
Easy
Ballistic Curtain
30 Cal Max
Unlikely
10 years (?)
Moderate (?)
Masonry Walls
30 Cal typical
Lifetime
Lifetime
Easy to Moderate
Moderate
Moderate to Difficult
Moderate to Difficult
Days to Weeks
Low to Medium
$95 to $250
Days to Weeks
Low to High
$75 to $150
Days to Months
Medium to High
$16 to $25
The choice of any of the three solutions depends on the level of protection required and the
particular installation. An advantage of armor panels is that they can be incorporated into the
tank design of new transformers, thereby making the transformer inherently resistant. They can
also be attached to the transformer similar to the way sound panels are or installed on existing
transformers in a manner similar to that of sound enclosures.
Ballistic curtains can be applied to the transformer and hung from supporting structures, but the
cost to achieve a high level of protection makes them an expensive solution. Long-term
durability of ballistic fabric armor used in an exposed environment is not adequately covered by
the NIJ standards. Level III and IV armor types are armor plates inserted into a fabric,
essentially making them another form of armor plating.
Depending on their construction, masonry or precast concrete walls may provide adequate
protection from most common firearms. If already installed as fire walls in an existing
substation, then their protection level can be readily verified. For new substations, masonry or
concrete walls can be designed with the necessary level of protection and spacing. Installing
walls in existing substations may be possible if adequate space is available. Walls represent the
lowest cost option, provided no major modifications to the substation are required.
Conclusion
The existing NERC and IEEE standards and guidelines for the physical security of substations do
not adequately address intentional attack from high-energy kinetic weapons commonly available.
Transmission asset owners and operators need to perform threat analyses and implement
measures to protect critical transformers to comply with the latest NERC CIP-014-1
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requirements. This paper does not give definitive solutions but does provide some guidance
about the likely maximum threat and some possible countermeasures.
References
1. FERC (March 7, 2014). “Reliability Standards for Physical Security Measures, Docket No.
RD14-6-000.” www.ferc.gov/CalendarFiles/20140307185442-RD14-6-000.pdf
2. NERC (June, 2002). “Security Guidelines for the Electricity Sector: Vulnerability and Risk
Assessment.”
www.esisac.com/Public%20Library/Documents/Security%20Guidelines/Vulnerability%20an
d%20Risk%20Assessment,%20Version%201.0.pdf
3. Red Jacket Firearms LLC. Retrieved April 2014 from www.redjacketfirearms.com;
www.redjacketfirearms.com/images/Russianred.jpg
4. Anzio Iron Works. Retrieved April 2014 from www.anzioironworks.com;
www.anzioironworks.com/20MM-TAKE-DOWN-RIFLE.htm
5. Retrieved April 2014 from www.reddit.com;
https://i1.ytimg.com/vi/7ft2j6J4NcY/maxresdefault.jpg
6. www.barrett.net
7. www.anzioironworks.com
8. www.edmarms.com
9. www.ferret50.com
10. www.bushmaster.com
11. www.mcmillanusa.com
12. www.deserttacticalarms.com
13. www.armalite.com
14. www.bluegrassarmory.com
15. www.serbu.com
16. Barrett Firearms Manufacturing. Retrieved April 2014 from www.barrett.net;
www.barrett.net/images/firearms/99-hero.jpg
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17. E.D.M. Arms. Retrieved April 2014 from www.edmarms.com;
www.edmarms.com/images/products/WndRnrF2.jpg
18. Retrieved April 2014 from http://herohog.com/images/guns/ammo/
http://herohog.com/images/guns/ammo/all_ammo_comparison.jpg
19. Oak Ridge National Laboratory. “Computational Materials Science Group.” Retrieved April
2014 from http://thyme.ornl.gov;
http://thyme.ornl.gov/downloads/pub/metak/movs/pyrlayer_int8_close.avi
20. Department of the Army. “Army Ammunition Data Sheets for Small Caliber Ammunition
(FSC 1305), TM 43-0001-27,” 29 April 1994.
21. Department of Defense. “Test Method Standard, V50 Ballistic Test for Armor, MIL-STD662F,” December 18, 1997.
22. Department of the Army. “Detail Specification: Armor Plate, Steel, Wrought, Homogeneous
(For Use in Combat Vehicles and for Ammunition Testing), MIL-DTL-12560K (MR),”
December 7, 2013.
23. NERC (October, 2011). “Security Guideline for the Electricity Sector: Physical Security
v1.89.” www.nerc.com/docs/cip/sgwg/Physical%20Security
%20Guideline%202011-10-21%20Formatted.pdf
24. IEEE. “Guide for Electric Power Substation Physical and Electronic Security, IEEE Std
1402-2000,” January 30, 2000.
25. Department of the Navy, U.S. Marine Corps. “Military Operations on Urbanized Terrain
(MOUT), MCWP 3-35.3,” April 26, 1998.
26. FERC (November 20, 2014). “Physical Security Reliability Standard, Docket No. RM14-15000.” www.ferc.gov/whats-new/comm-meet/2014/112014/E-4.pdf
27. NERC (May 2014). “CIP-014-1 - Physical Security.”
www.nerc.com/pa/Stand/Reliability%20Standards/CIP-014-1.pdf
28. Ibid.
29. Ibid.
30. Ezell B.C., “Infrastructure Vulnerability Assessment Model (I-VAM),” Risk Analysis, 2007;
27(3):571–583.
31. Department of Defense. “Test Method Standard, V50 Ballistic Test for Armor, MIL-STD662F,” December 18, 1997.
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32. Association of Test Laboratories for Bullet Resistant Materials and Constructions (VPAM).
“General basis for ballistic material, construction and product tests. Requirements, test
levels and test procedures, VPAM APR 2006 Edition: 2009-05-14.”
www.vpam.eu/fileadmin/Pruefrichtlinien_AKTUELL/2009-05-14_APR2006_englisch.pdf
33. National Institute of Justice. “Ballistic Resistance of Personal Body Armor: NIJ Standard–
0101.04.” Washington, D.C.: U.S. Department of Justice, National Institute of Justice,
September 2000. NCJ 183651. www.ncjrs.gov/pdffiles1/nij/183651.pdf
34. National Institute of Justice. “Selection and Application Guide to Personal Body Armor: NIJ
Guide 100–01.” Washington, D.C.: U.S. Department of Justice, National Institute of Justice,
November 2001. NCJ 189633 www.ncjrs.gov/pdffiles1/nij/189633.pdf
35. Ibid.
36. Best Safety Apparel. “Bomb & Ballistic Blanket-Level IIIA (NIJ).”
www.bestsafetyapparel.com/bo3.html
37. BulletProofMe. “Level IV Stand-Alone Rifle Plates.” www.bulletproofme.com/RP-Level-4Stand-Alone.html
38. Capital Building Consultants. “2014-2015 Cost Comparisons for Common Commercial
Wall Systems.” Winston-Salem, NC.
www.gobricksoutheast.com/CostComparisons/2014WallCostComparison4Web.pdf
39. Ibid.
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