Since the invention of phasor measurement unit (PMU), there has been growing interest in developing methodologies for finding the minimum number of units for complete system observability. The methods for the PMU placement must consider the fact that the network topology may change when the power system is affected by a contingency event (transmission lines and transformers). In order to design a robust wide area measurement (monitoring) systems (WAMS) which can ensure complete system observability under the failure of any transmission line or even a PMU, some works have considered power system contingencies and loss of measurements (failure of a PMU or its communication links).

In contemporary power system practice, the stability limits are typically computed off-line and stored in databases to be monitored by system operators (dispatchers) in the real-time environment. Several sources of uncertainty affect such computations and consequently reasonable stability margins must be taken into account when determining operation limits. Despite these precautions, unplanned outages and planned switching actions (such as topology control [TC] actions) may cause operational conditions not considered at operation planning stages, and consequently system operators are left with no pertinent stability information. Online stability assessment has been proposed as an additional line of defense in which stability limits are computed based on the actual power system condition, which decreases the uncertainty, thus providing more accurate stability operation limits. The online stability assessment can be performed for the (real-time) operating point only, or additionally for a region around this condition [1].

In this chapter, the authors extended the existing FDIAs on DC or AC model to a more generalized framework, where perfect and imperfect attacks are included. The vulnerability of SE under this generalized framework was investigated through the analysis of the tradeoff between attack magnitude and the attack error. To detect FDIAs, a measurement consistency check-based index is proposed. This index is defined by the measurement difference between received measurements and the interpolated measurements that are calculated through a small number of selected secure alternative PMU measurements. This index works well even when BD and FDIAs occur simultaneously. Simulation results on IEEE 14-bus and 30-bus test systems validated the effectiveness of the proposed method. With the development of WAMS, the proposed method could be a good candidate to mitigate the effects of cyber security on power system SE and measurements-based applications.