- Voltage collapse was investigated by simulations on a midsize power system with 39 buses and 10 generators. System loads were modeled as constant complex power corrupted with Gaussian noise of a small magnitude. The initial conditions for simulation were determined by singular-value decomposition of the load-flow Jacobian. The collapse-inducing disturbance was chosen to be a gradual increase of a portion of the total system load corrupted by noise. A systemwide voltage collapse was observed in all simulated scenarios. The slow dynamics of the collapse caused by load fluctuations opens perspectives for effective online detection. The constraints on the reactive power generation are discussed along with their effect on the stability boundary.