Protecting the Grid

With over 16,400 miles of transmission lines and 500 substations throughout the Tennessee Valley, grid resiliency is an important area of focus for TVA. Grid resiliency refers to the system’s ability to bounce back quickly from—or avoid completely—disruptions such as adverse weather events, cybersecurity threats, solar flares and/or electromagnetic pulses (EMPs).

Weather Events

According to the U.S. Department of Energy, weather events such as tornadoes, blizzards and hurricanes have accounted for more than half of all American outages since 2002.

While the Tennessee Valley is less affected by severe weather than some other regions of the country, high winds, ice and even tornadoes can and do affect the grid in our region.

TVA has procedures in place to maintain system reliability following advance notification of a coming storm by NOAA. These procedures are continually refined as knowledge is enhanced by experience in the field and by industry research, and TVA provides graduated responses to all levels of weather events.

Cybersecurity Threats

TVA works around the clock to monitor and protect its critical cyber assets, partnering with other government agencies such as the FBI and the Department of Homeland Security as well as with industry groups and peers, such as the Edison Electric Institute and neighboring utilities.

TVA has a comprehensive cybersecurity program aligned to industry best practices that operates to predict, protect, detect and respond to threats. Our focus is being proactive and using risk-based assessments to protect TVA. In addition to having multi-layered threat analysis capabilities, we perform continuous monitoring, penetration testing and vulnerability assessments.

TVA’s critical systems are housed within a specialized, isolated network that is separated from corporate networks and inaccessible by the internet. This segmentation provides a significant added level of security.

TVA trains its employees to recognize and resist cyber threats and also adheres to an array of industry and government standards, including National American Electric Reliability Corporation (NERC) Critical Infrastructure Protection (CIP) standards, Nuclear Regulatory Commission (NRC) security requirements and the Federal Information Security Management Act (FISMA).

Solar Flares

Solar flares peak on an 11-year cycle, though a storm can happen any time. Typically, there are 200 days of strong storms and four days of extreme conditions during each cycle (the last cycle peaked in 2014).

Following a prolonged period of very low solar activity, the new cycle is starting to develop with sunspots and flares. If a storm impacts the earth, it can result in very low frequency current in transmission lines (geomagnetic induced current, or GIC). These currents can cause equipment operation interference or even damage.

Our geographic location makes us less susceptible than more northern regions, though TVA did experience some nuisance effects in 2000-2003.

To maintain readiness for future disruption, TVA has:

• Completed a full risk analysis and implemented its recommendations
• Adopted new procedures to follow after notification of a storm
• Replaced all susceptible equipment
• Installed sensors at key locations to measure actual GIC and field strength
• Funded research on possible GIC blocking devices
• Modelled the transmission grid and studied effects of NERC benchmark and extreme storms
• Obtained detailed GIC models for all 500 kV transformers
• Continued to participate in NERC, EPRI, and DOE research

Electromagnetic Pulses

An electromagnetic pulse (EMP) is an instantaneous, intense energy field that can overload or disrupt at a distance numerous electrical systems and microcircuits, which are sensitive to power surges. There are two types: a high-altitude electromagnetic pulse (HEMP), such as might be caused by the detonation of a nuclear weapon, and an intentional electromagnetic interference (IEMI), caused by a device on the ground and generally affecting only a small area.

There are currently no NERC or other regulatory requirements for EMPs, but like other utilities, TVA is actively considering this as an emerging concern and working with a number of partners—including the U.S. Department of Energy and the Electric Infrastructure Security Council—on the very complex issues involved in prevention and recovery. TVA is also an active member of the Electric Infrastructure Security Council’s EMP Project.

Concrete steps being taken now include:

• Participating with other utilities in Electric Power Research Institute (EPRI) studies and equipment testing activities. See the final Phase 1 EPRI report here.
• Integrating information learned from EPRI activities into guidelines for practical grid hardening measures that will improve resiliency and recovery
• Review of transformer fleet performance in extreme events
• Review of black start and emergency plans for EMP scenarios
• Review of existing design practices
• Upgrading wireless communications systems
• Construction of a hardened and shielded operating center