A type of feedback linearizing excitation control, most recently reported in [1] is simulated on a very large (5000-bus) model of the Northeast Power Coordinating Council System. The control is implemented on two groups of machines, one in the New York City/Long Island area and one in the Lake Ontario area of New York State. A series of system faults is simulated, the most serious involving the loss of a very large portion of the transmission capacity from Northwest New York State to the New York City area, under extreme loading conditions. The nonlinear control prevents a breakup of the system which would otherwise result in a widespread blackout, at the expense of a rise in the system voltage at the Lake Ontario end. Simulations are also run with PSS/static exciter combinations on the same groups of generators, as a rough comparison of the performance of conventional vs. feedback linearizing control.