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In this paper, the switching surge risks on the low-voltage auxiliary system of the frequent start-stop plant are evaluated based on switching surge simulations, field measurements, and the investigation of a heavy damage case. First of all, modeling and switching surge voltage simulations by the Alternative Transient Program (ATP) of the Electromagnetic Transient Program for an actual plant are presented, where the switching surge voltages produced by the operation of load switches and source breakers of the low-voltage auxiliary system are simulated with respect to switch-close and switch-open operations with different switching modes, and different power-supply sources are considered. Then, the field measurement of switching surge voltages for a load circuit of an auxiliary system is implemented by the fast transient recorder; therefore, the ATP simulation correctness is verified. Finally, the affections of the switching surge voltages on insulation failure of equipment and the extended risks are evaluated by the comparisons between the results of simulation and measurement and the recommendations of the IEEE standard, and the investigation result of an actual heavy damage case. With the conduction of the evaluation, the enhanced measures for switching surge protection are proposed.