A Silent Saboteur at the Grid’s Edge: Decoding Supraharmonics

February 21, 2026

DERs like solar panels, bulk energy storage, and electric vehicle chargers could be weaponized to cause irreparable damage to the power grid. The physics of – and fixes for – a dangerous new security threat.

The rapid decarbonization and digitization of the grid is leading to fundamental shifts in their design and operation, yet most cybersecurity efforts continue to prioritize data breaches and digital “denial of service” attacks.

This focus may be missing a more catastrophic cyber-physical vulnerability: the ability of an adversary to weaponize the growing number of digital power electronics at the edge of our electrical grids. By hijacking smart inverters on solar panels or electric car chargers, attacks can transform a neighborhood’s green infrastructure into a synchronized electrical weapon, turning the grid’s digital assets against power systems and triggering outages, damage and instability that could take years to fix.

Chirp and Destroy

The attack surface weaponizes the invertors’ ability to generate, synchronize and focus destructive harmonic energy in the 15-28 kHz range. By exploiting the physics of supraharmonics, adversaries can bypass standard protection relays – which are effectively blind to these frequencies – and induce rapid dielectric breakdown in critical distribution assets. An attack like this does not rely on pre-existing knowledge of grid topology. Instead, it uses the invertors as a distributed array of sensors to perform grid tomography via active probing (chirp and detect).

Hardware Exploitation: Melting the Grid From Within

In a White Paper delivered this month at the S4 Conference, Optiv finds that the primary failure mechanism for targeted assets in a supraharmonics attack at scale – such as distribution transformers and capacitor banks – is not thermal overload but catastrophic insulation failure driven by high-voltage stress and partial discharge. Making matters worse, replacing affected equipment isn’t easy: transformer lead times exceed 100 weeks. This factors into a recovery timeline measured in years, potentially challenging the nation’s energy security and economic stability.

Strategic Call to Action: Mitigating the Risks of Homogeneity

The range of vulnerabilities posed both by an attack at scale are not just technical in nature, but symptoms of what’s possible if a growing software-defined monoculture continues. To counter the existential risk of Coordinated Supraharmonic Injection (CSHI) and adversarial grid shaping, a range of stakeholders – from regulators and professional associations to manufacturers and grid operators – must pivot from observation to active defense. 

For utilities and grid operators in particular, the distribution edge can no longer be treated as a black box. Utilities should deploy high-frequency sensing capabilities to monitor the supraharmonic spectrum in real time. By treating the invertor fleet as a senor array, rather than just a load, operators can detect the chirp of reconnaissance probing before the pulse of the attack, turning the adversary’s own tools into an early warning system.

Building Better, More Holistic Cyber-Physical Defenses

As digitization of the grid advances, utilities will benefit by improved and consistent collaboration between OT Cybersecurity, grid engineering and physical security resources to assess IT/OT vulnerabilities, integrate security, and to define new defenses.

For a deeper dive into the physics of supraharmonics, the threats and potential responses, check out the White Paper and Optiv’s own Grid Security Program Assessment services.