HPEM-based risk assessment of substations enabled for the smart grid

For extended critical infrastructures such as the power grid, electromagnetic compatibility (EMC) testing of electronic components alone is not sufficient to assess the risk of electromagnetic (EM) attacks. This paper presents results on a methodology for high-power EM based risk assessment of large structures considering the example of smart grid substations. The evaluation involves control, protection, and communication equipment used in substations as part of supervisory control and data acquisition systems and ready for the smart grid. The methodology developed in this paper evaluates the threat, vulnerability, impact, and protective measures as indicators in various scenarios of both conducted and radiated intentional EM interference (IEMI) threats to these systems. In order to assess these indicators, fundamental data on available IEMI sources, generic substation layouts, and their mitigating effects, coupling paths, and IEMI susceptibilities has been gathered in several test campaigns and studies. Electrical field strengths generable by commercially available power sources inside substations have been estimated considering measured shielding characteristics of the buildings and attainable target distances. A comparison with measured susceptibilities of control equipment to IEMI reveals noticeable security issues. In particular, expected field strengths inside substation buildings can be much higher than the immunity levels for control systems as requested in EMC standards.