Investigation of Phase Angle Differences Using Statistical Analysis of Real World State Estimator Data

Phase angle differences may provide very useful insight to guide the operations of the electric power grid. This analysis investigates two different methods to use data-driven statistical analysis methods to identify normal patterns and atypical events based on State Estimator phase angel differences. An ISO provided 15 months of State Estimator data. This data enabled the calculation of phase angle differences for 54 pairs of sites. The identified atypical events for both methods were compared to the ISO's operations log.

1. Introduction

The Planning Implementation Task Team (PITT) and Operational Implementation Task Team (OITT) of the North American Synchro Phasor Initiative (NASPI) identified baselining of phase angles as their highest priority. The baselining includes relating power system measurements (e.g., voltage and phase angles, path flows, and reactive reserves) with the system performance measures for normal operating conditions and during various limiting conditions, such as thermal limits, proximity to voltage instability, frequency and damping of oscillations, and transient angular stability. This kind of analysis will facilitate development of situation awareness tools from wide-area measurements. The value of phase angle information to assess grid reliability (for example, phase angle separation, small signal stability and damping levels) became obvious during the analysis of the blackouts within the Western and Eastern Interconnections on August 10, 1996, and August 14, 2003, respectively.