Impact of MHD-E3 on power system equipment and loads.
The detonation of a nuclear weapon in the Earth’s upper atmosphere will cause a variety of electromagnetic disturbances at the Earth’s surface. One of these disturbances – the magnetohydrodynamic late-time or MHD-E3 pulse – is characterized by a strong yet minute-long electric field that is capable of inducing quasi-direct currents in long conductors such as electric transmission lines. These quasi-direct currents, on the order of 1000 amps within the power grid, will cause transformer saturation that leads to abnormal power absorption and high levels of harmonics in the power system. Research herein explores the impact of these direct currents on transformers, the impact of elevated levels of harmonics on power system protective relays, and the impact of harmonic-rich voltages on information technology equipment. A benchtop transformer DC injection testing apparatus was designed and constructed, and these laboratory transformer test results are analyzed and compared with the results of DC injection tests performed on power system transformers at Idaho National Laboratories. Electromechanical, solid state, and microprocessor-based protective relays were subjected to harmonic currents and this performance is documented, analyzed, and recommendations for mitigating protection system mis-operations are provided. The response of a modern microprocessor-based transformer differential relay to harmonic current simulations, including a relay with a second harmonic waveshape recognition algorithm, is presented and analyzed. Finally, a testing system was constructed and the evaluation process, analysis, and results for the response of information technology equipment to harmonic voltage waveforms measured during the Defense Threat Reduction Agency DC-injection transformer testing at Idaho National Laboratories in 2012 are included.