System Event Automatic Correlation of Voltage Dips for SARFI Benchmarking D. Daniel Sabin, Electrotek Concepts Erich W. Gunther, Electrotek Concepts

Tennessee Valley Authority (TVA) Public power provider 8 million customers across seven states via 158 distributors and 62 direct serve customers. Collecting power quality and energy data from critical customer sites since 1996 Data stored in 20 gigabyte, on-line database management system (PQView) System permits calculation of numerous indices

Goal To establish a benchmark of the TVA system in order to provide the means to track the success (or lack of success) of improvements made to the system over time Compute the number of voltage dips with a remaining voltage below 0.70 per unit (pu) that had causes attributable to the TVA transmission system Separate the voltage dips recorded into two bins: those voltage dips which were caused by TVA’s customers and those which were caused by a problem within TVA’s system itself

SARFIX Index Chosen When computed for a single monitoring location, the SARFI70 index represents the count of voltage dips in which at least one phase fell to below 0.70 pu of the location’s nominal base voltage, and with a duration less than 60 seconds

Rules Automatically identify the customer faults by searching for rms variation measurement events with these characteristics: (1) the remaining rms voltage of one or more phases was less than 0.70 pu; and (2) the rms current of one or more phases was above a site-specific threshold.

Example

Event Correlation

Conclusion The measured events at multiple monitoring locations and at multiple times are linked together in the TVA database using a “system event” record. The record also allows the system event to be categorized by cause code, by source code (e.g., tie-line, circuit, generator, substation, customer, etc.), by weather code, and by equipment code (e.g., cable, joint, transformer, conductor, splice, arrestor, cross arm, etc.) TVA considers the automatic routines for system faults due to customers and the automatic correlation of the measured events to be a successful effort