  Load-generation balance and system inertia are essential for maintaining
frequency in power systems. Power grids are equipped with Rate-of-Change-of
Frequency (ROCOF) and Load Shedding (LS) relays in order to keep
load-generation balance. With the increasing penetration of renewables, the
inertia of the power grids is declining, which results in a faster drop in
system frequency in case of load-generation imbalance. In this context, we
analyze the feasibility of launching False Data Injection (FDI) in order to
create False Relay Operations (FRO), which we refer to as FRO attack, in the
power systems with high renewables. We model the frequency dynamics of the
power systems and corresponding FDI attacks, including the impact of
parameters, such as synchronous generators inertia, and governors time constant
and droop, on the success of FRO attacks. We formalize the FRO attack as a
Constraint Satisfaction Problem (CSP) and solve using Satisfiability Modulo
Theories (SMT). Our case studies show that power grids with renewables are more
susceptible to FRO attacks and the inertia of synchronous generators plays a
critical role in reducing the success of FRO attacks in the power grids.
