Synchrophasors redefining scada systems

Modern power system grid monitoring tools use data from remote terminal units (RTUs), protective relays, and transducers to provide information to system operators. This information is vital for the operation of the power system on a daily basis and under system contingencies. However, the mechanism used to retrieve data from the devices is asynchronous and relatively slow. The asynchronous nature of the data does not provide accurate angle difference information from two nodes on the network. Additionally, the low data rate may be too slow to capture many short-duration disturbances on the grid. Alternatively, phasor measurement units (PMUs) sample voltage and current many times a second and accurately time-stamp each sample. This technology can be used to provide high-speed and coherent real-time information of the power system that is not available from legacy supervisory control and data acquisition (SCADA) systems.

This paper discusses the existing SCADA system and the recently installed wide-area monitoring system (WAMS) at the Power Grid Corporation of India Limited (PGCIL) Northern Regional Load Despatch Centre (NRLDC). The paper discusses the communications infrastructure the WAMS uses and the tools to monitor and archive the time-synchronized data. The paper also discusses system events witnessed on the PGCIL network following the WAMS installation and how the WAMS provided critical information that is lacking in existing SCADA systems.