Load flow studies in the presence of magnetohydrodynamic electromagnetic pulse

A scenario in which, seconds after a high-altitude nuclear event, the Earth´s surface experiences a very low-frequency, quasi-DC magnetohydrodynamic electromagnetic pulse (MHD-EMP) field is considered. MHD-EMP fields impress quasi-DC currents on transmission and subtransmission lines. These current magnitudes can exceed several times the transformer exciting current levels. Transformers and shunt reactors experience severe half-cycle saturation resulting in harmonics and increased VAr (volt-ampere reactive) demand. The calculation of the quasi-DC currents is reviewed, the calculation of the increased VAr demand is discussed, and the effect of a simulated MHD-EMP event on a power system with stability and load flow analyses is evaluated. For the APS (Arizona Public Service) system, the simulated, base-case MHD-EMP event has major impact on power flows and voltage levels for subtransmission systems. For the base case analyzed, MHD-EMP has little effect on system stability and negligible impact on networks with DC ground paths that span small geographic distances