L-Index Based

1. This paper uses PMU measurements from the entire system to compute L index based voltage stability index. This uses both phasor measurements and network topology to compute the L index. The authors assume full observability of the monitored power system for the implementation of proposed voltage stability assessment approach. (http://ieeexplore.ieee.org/document/6508139/)
2. This paper introduces a voltage stability index similar to L-index for voltage stability monitoring. This paper discusses voltage stability enhancement using phasor measurement units by proposing to make Voltage stability margin a constraint in formulated OPF problem. (https://ieeexplore.ieee.org/document/5307295/)
3. https://ieeexplore.ieee.org/document/6572886/