Using Synchrophasor System Data for Establishing Operating Range for Operators Guidance and Detection Analysis of Significant Events
Under a Department of Energy (DOE) project, Electric Power Group (EPG) along with four ISOs (NYISO, MISO, PJM and ISO-NE) in Eastern Interconnection (EI), are exploring the feasibility of using synchrophasor system data for establishing normal operating ranges for guidance to operators and identifying significant events occurring in the power system. Establishing the normal operating ranges for angle pairs can help operators to identify if the system moves into an abnormal system state. The analysis of significant events can help to understand in detail pre and post cursors of the event. Hundreds of Phasor Measurement Units (PMU) have been installed in the EI of the United States and data is available for the analysis. The collected data has been made available to EPG by the four ISOs for the PMU’s relevant to the selected angle pairs. The time-stamped data using C37.118 format was collected by each ISO independently, and combined to extract wide-area angle pair information. Even though much more information could be extracted from the provided PMU data, the project was focused on the voltage angle pairs. The objective of the project is to determine if the data can be used for (1) setting up wide-area angle pair operating ranges across ISOs, (2) wide-area system stress monitoring, (3) identifying significant system events and understanding their impacts on various regions, (4) analysis of events to understand pre and post event dynamics.
The result of the project has shown that multi-ISO PMU data can be used to determine operating ranges, and can be used by operators to identify abnormal operating conditions. ISOs can monitor wide-area stresses for regions that are not in their control area. The control chart screening technique commonly used in manufacturing for quality control could be used to filter significant events and would allow users to perform the detailed analysis on the identified events. Manufacturing industry typically uses a value of +/- 3 sigma; however, for the analysis of synchrophasor data, sigma values of 15 to 20 were found to provide good results in identifying events. Using this technique during one week period from December 1 to 7, 2014, three significant wide-area events and multiple local events were identified. Although the analysis was limited to voltage angle pairs, the analysis methodology could be applied for other parameters; such as sensitivities, oscillations or power flows to identify the abnormal system condition. In addition their trends can be combined to pinpoint degrading system conditions or near misses that may be more critical than violations of single metrics. This paper presents the analysis of the wide-area angle pairs for setting ranges and the technique used for screening large amount of data.