Physical Security-Resiliency Against Long Term Outages

Presented By:
Petter Fiskerud
Power Transformer Resiliency Program Manager, ABB Inc.
& Craig L. Stiegemeier
Expert Services Product Manager, ABB Inc.
TechCon 2018


The loss of a key transmission assets such as a step-up transformer, whether it is due to a natural or man-made event, can cause a loss of significant power to the grid. Depending on the circumstances this loss of power could cause other cascading effects resulting in long-term outages. ABB has developed a 5 step program to significantly reduce the risk and rapidly repair/replace transformers to mitigate the impact.

  1. Assess the asset risk to extreme weather events, intentional criminal attacks, geomagnetic disturbances (GMD), and electromagnetic pulses (EMP)
  2. Harden substations and power equipment against malevolent attack, and extreme environments
  3. Remote Monitor the asset and surroundings and Automate response to abnormalities 4. Rapidly Repair lightly damaged power equipment
  4. Rapidly Replace severely damaged power equipment

In this presentation we will cover each of the above areas with a special focus on hardening and rapidly replacing the transformers.


What could happen if several large power transformers went out of service at the same time? This is a scenario that raises to the top of the reliability discussion agenda. Consider the scenario where a large metropolitan area is served by 10 major substations and more than one utility. 60% of the peak load is carried by just 11 transformers in four of those substations. A coordinated attack could significantly damage those transformers. The resulting outage would be catastrophic for that area both in terms of size and duration. FERC and NERC concerns are placing requirements on our customers – they need solutions. According to a recent survey from Utility Dive, 40% of utility respondents consider shootings and planned sabotage a potential threat to their substation.

Physical security considerations

Current methodology is not enough. Absolute physical security is not practically achievable. Vulnerabilities hinge on attackers’ intentions and resources. There is no way to absolutely protect a substation transformer and other electrical equipment from severe damage from an intentional attack. It is possible to make the damage less severe, prolong service and restore service more quickly with a layered approach to physical security.

layered approach to physical security & resiliency

Protect your substation and minimize downtime

Systems must be protected by a layered approach, as shown above. A single layer of security, such as in the hard shell of an egg, is not adequate. Layered levels help insure that all aspects of a power delivery system are taking into account when developing an effective physical security and resiliency process.

A 5 step process has been developed that includes the following:

  1. Assess the asset risk to extreme weather events, intentional criminal attacks, geomagnetic disturbances and electromagnetic pulses
  2. Harden substations and power equipment against malevolent attack, and extreme environments
  3. Remote Monitor the asset and surroundings and Automate response to abnormalities
  4. 4. Rapidly Repair lightly damaged power equipment
  5. Rapidly Replace severely damaged power equipment

Starting with an assessment of each individual substation helps develop flexible options that are based on each unique situation. This takes into account the equipment in the substation as well as the physical and environmental challenges that make each location unique.

First step

Assess vulnerabilities in critical substations. Assessments should include:

  • Substation site details
  • Physical landscape and system information

A thorough assessment of the equipment

  • Nameplate / design
  • Operating data
  • External barriers
  • Tank & components
  • Bushings & arresters

Ballistic protection system

The AssetShield™ (patent pending) ballistic protection system has been developed by ABB. This system provides resiliency through the application of hardened steel with impact and fragmentation protective coating for electrical power apparatus designed to protect equipment from extreme events. This system reduces the kinetic energy of the bullets and reduces spalling (fragmentation) after impact to reduce collateral damage.

ballistic testing protocol

Ballistic Testing: Typical tank wall: 3/8” Mild Steel (UL 8)

exterior view of the tank wall
Interior of tank wall

Ballistic Testing: Hardened steel without AssetShield™

UL 752 Level 8 – Spalling
UL 752 Level 9 – Spalling

Ballistic Testing: AssetShield™

Highest level of protection
No spalling from impact
Recommended solution for power transformers

UL 752 Level 10 – Passed

Summary of ballistic testing

Solution to meet UL 752, Level 10 requirements

UL 752 Level 8
Fail – Common transformer tanks: ⅜”, or ½” mild steel – even with AssetShieldTM
Pass – ⅜” hardened steel without AssetShieldTM (potential collateral damage) ⅜” hardened steel with AssetShieldTM

UL 752 Level 9
Fail – ⅜” hardened steel
Pass – ½” hardened steel without AssetShieldTM (potential collateral damage) ½” hardened steel with AssetShieldTM

UL 752 Level 10
Fail – ⅜” hardened steel with AssetShieldTM
Pass – ½” hardened steel without AssetShieldTM (potential collateral damage) ½” hardened steel with AssetShieldTM

ABB Recommends ½” hardened steel with AssetShield™ to provide protection from the largest readily available ballistic rounds.

Ballistic resiliency

To eliminate the chance of an extended outage, protecting the active part and controls is critical. Keep the core and coils and other critical components in the transformer tank under oil and free of contamination to help speed recovery from an attack. Prevent ballistic penetration of tank and critical components.

  • Ensures active part is always under oil
  • Minimizes the chance of an internal electrical failure from exposure of high-stress areas
  • No moisture or debris ingress

Tank and conservator made with AssetShield™
On-tank OLTC made with AssetShield™
Control Cabinets made with AssetShield™

Dry bushings

When an oil-filled porcelain bushing is compromised there is a great chance for collateral damage. A ballistic impact on a centrally clamped porcelain bushing may cause an explosion due to internal pressure from an arc and the spring force on the porcelain outer shell. Porcelain shards can be sent flying 40 yards or more and put other equipment and personnel at risk. Conductor, lead and the lower porcelain may fall into the transformer when the support of the upper porcelain is suddenly removed. The resulting electrical arc often ignites the flammable oil and oil-soaked paper and can cause further collateral damage within the substation. Repair time and transformer and substation equipment damage can be significantly minimized with the application of dry bushings.

Bushing resiliency

Dry bushings can be provided on new transformers or retrofit into existing transformers. Since there may be physical differences, an engineering study is typically required. Dry bushings aid in protecting against collateral damage and minimizing the impact of a bushing failure on the transformer. Solid (oil free) construction aids greatly in eliminating the risk of fire. Non porcelain shed eliminates damage:

  • To the transformer
  • To other equipment
  • To personnel

Excellent electrical, thermal and mechanical characteristics:

  • Environmentally friendly
  • Maintenance- and check-free
  • Transportation and storage at any angle

Physical security awareness

Large transmission transformers are sometimes located in remote substations. This in itself can make the substations vulnerable to a physical attack. In addition, they are often unmanned so if an attack occurs, the utility may not be aware of the impact for quite some time. This means that the attacker can do extensive damage and leave prior to the arrival of first responders.

Sensors are available for substations that detect ballistic activity and can send an alert, warning of a potential attack. However, it is not known if this is a hunter in the area or someone intent on causing damage to the substation.

A transformer equipped with a Ballistic Impact Sensor affords early detection and knowledge that a ballistic attack is taking place. ABB has developed a system (CoreStrike™) that employs sensors mounted on each of the four sides of the transformer and a detection level measurement system. It is easy to install on both new and existing transformers. The CoreStrike™ system supports sending an alarm at the very early stage of an attack, allowing first responders to be deployed immediately, to help minimize the attack and secure the site. The system is a simple and robust solution that detects ballistic impact and allows control of automated valves in addition to sending an alarm through SCADA or other systems. Extensive testing minimizes the chance of a false detection. The response to different impacts is shown in the following graph:

RMS acceleration of bullet and non-bullet trials

Cooling resiliency

The CoreStrike™ system can be integrated into a response solution that automatically closes radiator valves to isolate cooling system impact from the main tank. This avoids costly shielding and foundations to support ballistic barriers while still isolating the core and coils from the impact of an attack. This helps ensure the active part is always under oil and eliminates moisture or debris ingress. Sensors can be added to open the valves once confirmation that oil leakage from the radiators or coolers is not taking place.

This system can be adapted to existing cooling, as the solution adds less than 4” to width/length. Additionally, there is no restriction on cooling due to air-flow restrictions from shielding radiators. There is typically no need for additional cooling on existing transformers and it supports easy fan and cooling maintenance requirements. It is recommended that replacement/spare radiators/coolers are readily available. It is also possible to isolate and shield the cooling or support a redundant cooling system to ensure uninterrupted operation.

Accessories resiliency

Critical protection is provided at entry points and for important accessories. Design options offer solutions that do not impact the ability to easily conduct maintenance activities. This protection supports the goal of ensuring the core and coils are always immersed in oil and protected from moisture or debris ingress. Specific protection is provided for the following components:

component protection

ABB Transformer resiliency solution

The standard features of the solution are scalable, simple and effective. ABB is ready to offer any or all of these features on new transformers or retrofit in existing installations. ABB Solution includes AssetShield™, Tank, conservator OLTC and control cabinet, Dry Bushings, CoreStrike™ transformer ballistic impact sensor, Automated cooling valves, and Protected valves and other entry points.

ABB Transformer resiliency solution

Increased resiliency with minimal design impact

The ABB Power Transformer solution – minimized design impact

This system is designed to protect the transformer active part, while maintaining the look and feel of a “normal” transformer. This supports minimizing the “advertising” of a critical substation piece of equipment while still offering effective protection.

Transformers are designed to support maintenance activities over the lifetime of the equipment. The ABB solutions have minimal impact on components and systems that require periodic maintenance. Also, there are no restrictions of the cooling system that otherwise may result in de-rating or a significant size increase of the transformer. The system has the side benefit of superior environmental properties, supporting installations in contaminated environments – such as salt spray areas. If it is desired to convert the system onto existing units, the impact is minimal. Normally no additional cooling is needed; the weight increase is below 5%; and the transformer fits on existing foundations.


It is important to plan out the steps to take after a real substation emergency happens. In preparation, working with local emergency personnel ensures an effective response while minimizing the risk of additional equipment damage and risk to personnel. In the event of an attack, the first responders should make the site safe and allow restoration experts entry to the site(s). Experts should be engaged to provide an initial assessment of the condition of the equipment. A determination of manpower / equipment requirements needed to restore the site to operational status would be performed, including the mobilization (as needed) of additional specific resources, such as replacement equipment and processing systems, needed to start the repair process. Identification and procurement of parts and equipment can then begin.

Importance of partnering

Outage services often require expertise beyond what typical maintenance crews possess. Alignment with experts that have experience working large scale emergency substation outages is recommended. As part of your homework, a specific substation outage restoration plan should be developed. This allows identification of substation outage readiness, an analysis of the installed base and need for specific spare parts to support the installation.

Additionally, an environmental and equipment specific assessment of susceptibility of substations to damage should be performed. This allows effective hardening of substations to reduce potential damage, while controlling cost. Also, appropriate selection and training of qualified first responders is a result of the assessment. The following options should be considered:

  • Choose the right partner
  • Local service shop sites that could be quickly mobilized
  • Replacement parts
  • Capabilities to repair / replace the substation equipment
  • Testing and commissioning services

Rapid replace

Since there is no way to absolutely protect equipment from all damage, actions should be initiated to develop rapid replacement options. Since transformers are likely the longest lead time component in a substation, a spare/replacement strategy should be initiated for all critical substations. Identical spare transformers or somewhat standardized transformers should be considered as a solution to rapid replacement. Transformer designs can be optimized for rating and logistic flexibility. Spares for the most critical transformers are prudent. It is possible to design universal spares that provide resiliency by supporting replacement in multiple locations. When damages exceed repair capabilities, rapid replacement strategies play an important role in rapid substation recovery.

recovery solutions full range

ABB Recovery Solutions

Since many transformers are designed for specific points in the gird, they vary in voltage ratio and other characteristics. A spare must be able to support that point in the grid. Studies were performed for EPRI (Electrical Power Research Institute) and the Department of Homeland Security that identified 345/138kV and 500/230kV as the most deployed large transmission transformers on the Grid. For that reason, a concept transformer identified as the Recovery Transformer (or RecX) project was initiated that created designs to match these most frequent needs.

The following table contains 6 possible conceptual designs for 345 and 500kV transmission transformers. Designs 1-4 in the table are transformers that support 4 different low voltage system levels, identified as Polytransformers™. Designs 5 and 6 allow rapid transportation (these are the DHS Recovery Transformer design concepts – or RecX design) that support replacement of a large bank (600MVA) of transformers. These designs can be relocated from storage and transported over a long distance to the restoration site. Design concepts allow reassembly and energization in a few days – well under a week.

6 possible conceptual designs for 345 and 500kV transmission transformers

Contingency planning

The most important thing to initiate is a review of important substations and develop a contingency solution for the loss of critical substation equipment. This plan needs to take into account the specific equipment in the substation along with physical logistics in and around the substation environment. Following is an example of a plan that includes location of a mobile transformer to support the complete loss of the main transformers in the substation.

contingency solutions predefined contingency plan

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