Energisa Minas Gerais Distribuidora de Energía, one of 13 utilities in the Energisa Group, serves a 17,200-square-kilometer area in the southeastern part of the Brazilian state of Minas Gerais.
It provides electricity to 438,600 customers through 21,000 kilometers of 11.4-kV and 2,000 kilometers of 22-kV distribution lines. Approximately 90% of the utility’s medium-voltage distribution lines serve the rural areas of the service territory.
In a study, the utility found that on average, 76% of the faults that occurred in 2012 were temporary in nature.
These temporary faults caused fuse-cutout operations resulting in a permanent outage for customers on the affected section of line.
The temporary faults also resulted in a 17% increase in the System Average Interruption Duration Index (SAIDI) rating and a 7% increase in the System Average Interruption Frequency Index (SAIFI) rating.
The study also determined that 55% of all truck rolls were dispatched to fix permanent outages caused by fuse-cutout operations that resulted from temporary faults.
In addition, 30% of all crew work hours were spent restoring service when temporary faults caused outages in rural areas.
Based on the findings, the utility decided something had to be done because it was facing growing pressure to significantly reduce its SAIDI and SAIFI ratings to meet government regulations and to avoid financial penalties.
Improving reliability for rural distribution
Energisa Minas Gerais studied various solutions to improve its reliability indices and developed plans to implement various solutions focused on protection schemes, three-phase reclosers, and fault indicators.
The utility also determined that another solution to the outage problem was to install single-phase reclosers on its single-phase rural laterals as an alternative to traditional fuse cutouts.
After analysing various single-phase reclosers, Energisa Minas Gerais decided on the S&C TripSaver II Cutout-Mounted Recloser.
In the year before the installation of the 10 TripSaver II reclosers, Energisa Minas Gerais paid out $1,300 in penalties to customers on those laterals because of poor reliability and performance indices.
In the year after the installation of the reclosers, the payout totaled only $24, resulting in a penalty-cost reduction exceeding 98%.
To find out more potential savings from safeguarding rural distribution lines, download S&C's case study.