The typical characteristics of a certain high-voltage trip-off accident of wind turbines that does happen in a power system are reviewed.It is concluded that in learning about the root cause of the accident，we need to give careful consideration of the impact of dynamic reactive compensation control.Based on a simple equivalent system，the reactive power-voltage sensitivity expression considering the influence of constant reactive power control of inductive branch in dense wind power areas is derived.It is proved in principle that constant reactive power control on the inductive branch adopted by a static reactive compensator will cause an increase in reactive power-voltage sensitivity.And the growth rate depends on the initial value of the inductive branch.Further，it is pointed out that the increase in reactive power-voltage sensitivity due to constant reactive power control on the inductive branch is one of the main causes that leads to the “5·14”high-voltage trip-off accident.Finally，the typical case of an actual system is verified by simulation.