Introduction to Electromagnetic Compatibility

To assess the geomagnetic hazard to power systems it is useful to be able to simulate the geomagnetically induced currents (GIC) that are produced during major geomagnetic disturbances. This paper examines the methodology used in power system analysis and shows how it can be applied to modelling GIC. Electric fields in the area of the power network are used to determine the voltage sources or equivalent current sources in the transmission lines. The power network can be described by a mesh impedance matrix which is combined with the voltage sources to calculate the GIC in each loop. Alternatively the power network can be described by a nodal admittance matrix which is combined with the sum of current sources into each node to calculate the nodal voltages which are then used to calculate the GIC in the transmission lines and GIC flowing to ground at each substation. Practical calculations can be made by superposition of results calculated separately for northward and eastward electric fields. This can be done using magnetic data from a single observatory to calculate an electric field that is a uniform approximation of the field over the area of the power system. It is also shown how the superposition of results can be extended to use data from two observatories: approximating the electric field by a linear variation between the two observatory locations. These calculations provide an efficient method for simulating the GIC that would be produced by historically significant geomagnetic storm events.

/pdf/methodology-for-simulation-of-geomagnetically-induced-3hsu413l0y.pdf

Methodology for simulation of geomagnetically induced currents in power systems

In this paper we present an overview of the IEMI threat, discuss an assessment approach, and present mitigation options. Because it is often dominant, we concentrate on cable coupling of radiated RF (radio frequency) power as the means of IEMI attack. We separate an IEMI attack into various parts, and introduce an efficient approach for assessing the IEMI vulnerability of a facility. We then present some methods to mitigate IEMI attacks, especially for network cable coupling. Finally, we review ongoing worldwide IEMI efforts.

Overview of the threat of IEMI (intentional electromagnetic interference)

Recent research has shown that the integrity of sensor measurements can be violated through out-of-band signal injection attacks. These attacks target the conversion process from a physical quantity to an analog property—a process that fundamentally cannot be authenticated. Out-of-band signal injection attacks thus pose previously-unexplored security risks by exploiting hardware imperfections in the sensors themselves, or in their interfaces to microcontrollers. In response to the growing-yet-disjointed literature in the subject, this article presents the first survey of out-of-band signal injection attacks. It focuses on unifying their terminology and identifying commonalities in their causes and effects through a chronological, evolutionary, and thematic taxonomy of attacks. By highlighting cross-influences between different types of out-of-band signal injections, this paper underscores the need for a common language irrespective of the attack method. By placing attack and defense mechanisms in the wider context of their dual counterparts of side-channel leakage and electromagnetic interference, this study identifies common threads and gaps that can help guide and inform future research. Overall, the ever-increasing reliance on sensors embedded in everyday commodity devices necessitates that a stronger focus be placed on improving the security of such systems against out-of-band signal injection attacks.

/pdf/taxonomy-and-challenges-of-out-of-band-signal-injection-3ihauqojwa.pdf

Taxonomy and Challenges of Out-of-Band Signal Injection Attacks and Defenses

Recent research has shown that the integrity of sensor measurements can be violated through out-of-band signal injection attacks. These attacks target the conversion process from a physical quantity to an analog property---a process that fundamentally cannot be authenticated. Out-of-band signal injection attacks thus pose previously-unexplored security risks by exploiting hardware imperfections in the sensors themselves, or in their interfaces to microcontrollers. In response to the growing-yet-disjointed literature in the subject, this article presents the first survey of out-of-band signal injection attacks. It focuses on unifying their terminology and identifying commonalities in their causes and effects through a chronological, evolutionary, and thematic taxonomy of attacks. By highlighting cross-influences between different types of out-of-band signal injections, this paper underscores the need for a common language irrespective of the attack method. By placing attack and defense mechanisms in the wider context of their dual counterparts of side-channel leakage and electromagnetic interference, this study identifies common threads and gaps that can help guide and inform future research. Overall, the ever-increasing reliance on sensors embedded in everyday commodity devices necessitates that a stronger focus be placed on improving the security of such systems against out-of-band signal injection attacks.

/pdf/taxonomy-and-challenges-of-out-of-band-signal-injection-4i55hez9i5.pdf

Standardization of High Power Electromagnetic (HPEM), environments, protection design and test methods is becoming increasingly important particularly as the perceived risk to society from HPEM is growing. Many generic standards and some application or product specific standards are now available. This letter will provide an overview of some recent developments in HPEM standards, in particular High Altitude Electromagnetic Pulse (HEMP) and Intentional Electromagnetic Interference (IEMI) phenomena.

Recent Developments in High Power EM (HPEM) Standards With Emphasis on High Altitude Electromagnetic Pulse (HEMP) and Intentional Electromagnetic Interference (IEMI)

Here we present an efficient method for evaluating the EM shielding effectiveness of a commercial building to determine approximately the amount of shielding available before beginning a “hardening” program. A traditional approach is to use a transmitter/antenna matched to an antenna/receiver. In that standard approach the setup is calibrated in an open area outside, with a set separation distance. Then the same setup is used, but with the antenna/receiver moved into the building - with shielding effectiveness determined by the reduction in the received field, as provided by the building structure. However, done properly, this approach can be expensive, time consuming, and may present some logistical problems. To address these problems, we present a much simpler alternative approach. For this method only the internal antenna/receiver part of the setup is used. The external source is replaced by using existing external RF sources, such as AM and FM radio transmission, and signals from cellular phone towers. This approach also accounts for the fact that at lower frequencies (∼1 MHz) the shielding effectiveness differs for electric and magnetic fields. After discussing this approach, we then present a test in which this method and the traditional approach are used on a building, and the results compared. All approaches have strengths and weaknesses - this method produces reasonable results with greatly reduced effort. It is especially useful in that there is no need to procure the right to illuminate the building and to gain access to all required transmitter sites all around the building.

An alternative EM shielding effectiveness measurement method for buildings

This paper provides details of a computational technique used to calculate currents induced by geomagnetic storms on transmission lines and in transformers of a large power grid. In practice, this technique has been driven by three sets of input data — magnetometer data on an irregular grid, magnetic fields from storm models, and predictions of magnetic fields from satellite data. The technique employs a ground conductivity that varies in both the horizontal and vertical directions and a computationally efficient technique for performing the convolutions needed to obtain the horizontal electric field from the horizontal magnetic field. A quasistatic technique is used for circuit modeling of lines and transformers, and various transformer and core types may be included for modeling of the current flow and of the generation of reactive power demand. This technique has been implemented in the POWERCASTTM code.

A technique for calculating the currents induced by geomagnetic storms on large high voltage power grids

The calculation of the high-altitude electromagnetic pulse (HEMP) fields resulting from a nuclear explosion is dependent on the modeling of secondary electrons generated by the high-energy Compton electrons. In this paper, we discuss different modeling procedures used for this task and show how modeling a delay in the formation of the conductivity resulting from the low-energy electrons affects the HEMP electric fields at the surface of the ground.

William A. Radasky

Papers

Overview of the threat of IEMI (intentional electromagnetic interference)

Recent Developments in High Power EM (HPEM) Standards With Emphasis on High Altitude Electromagnetic Pulse (HEMP) and Intentional Electromagnetic Interference (IEMI)

An alternative EM shielding effectiveness measurement method for buildings

A technique for calculating the currents induced by geomagnetic storms on large high voltage power grids

Study of Nonequilibrium Air Chemistry