Control Strategies for Large Power Transformer HEMP/GMD Protection

Document Type

Conference Proceeding

Publication Date



Department of Mechanical Engineering-Engineering Mechanics


A high altitude electromagnetic pulse (HEMP) or other high intensity geomagnetic disturbance (GMD) has the potential to severely impact the operation of large-scale electric power grids. This is due to the introduction of low-frequency geomagnetically induced currents (GICs), which can saturate the magnetic core of large power transformers and lead to distorted ac waveforms, increased losses, and the potential for cascading blackouts. This paper presents a controls-based strategy for protecting transformers against such threats. Analysis of two different HEMP/GMD protection approaches are evaluated: first, a neutral-path blocking approach, and second, a magnetizing-path flux cancellation approach. The relative trade-offs between the two techniques are provided, and a demonstration of their application in a representative 4-transformer grid scenario is considered. Finally, conclusions and directions for future research are proposed.

Publication Title

2023 North American Power Symposium, NAPS 2023