  This paper investigates how a disturbance in the power network affects the
nodal frequencies of certain network buses. To begin with, we show that the
inertia of a single generator is in inverse proportion to the initial rate of
change of frequency (RoCoF) under disturbances. Then, we present how the
initial RoCoF of the nodal frequencies are related to the inertia constants of
multiple generators in a power network, which leads to a performance metric to
analyze nodal frequency performance. To be specific, the proposed metric
evaluates the impact of disturbances on the nodal frequency performance. The
validity and effectiveness of the proposed metric are illustrated via
simulations on a multi-machine power system.
