This paper discusses the performance of different line voltage stability indices previously studied in literature including Line stability Index (Lmn), Fast Voltage Stability Index (FVSI), Voltage Collapse Point Indicators (VCPI), and Line Stability Index (LQP). The long term objective is to identify which index is most suitable for being used in control applications (bandwidth of the Wide Area Monitoring Systems (WAMS)) for future grids. For this objective the first step was to create a time-domain baseline model and to validate the theory on voltage stability indices. The results presented here will provide a first indication. The indices were tested in a small 5-bus system and in a larger 39-bus system. The Real Time Digital Simulator (RTDS) was used to create data sets and the indices where computed using the control block components for real time operation. This method was chosen to have the values of the indices available for future development of control algorithms based on stability indices.