Circuit Breaker Replacement Ranking

Because of the older demographic distributions common in many utilities, improvements are needed to provide more effective management of aging high-voltage circuit breaker fleets. Operating such equipment reliably and with a low risk of failure at or beyond typically assumed design lives is a subject of interest for many utilities. Consequently, developing and justifying a repair/replace (R/R) management strategy for these populations, and the rational basis for it, are increasingly important.

A rigorous repair versus replacement decision analysis would be mathematically quite complex and require many assumptions. However, an understanding of common utility asset management decision processes has allowed EPRI to develop a methodology to help identify candidate breakers for replacement and to rank a group of candidates in a rational and defensible fashion.

The circuit breaker replacement ranking methodology uses a risk-based approach designed to help utilities identify replacement candidates. It provides an analytical basis that is consistent and repeatable, objective and documented, risk based, and addresses regulatory concerns.

Using existing data, the methodology infers the relative costs and risks of keeping a breaker in service. Input parameters for applying this method are selected based on understanding how circuit breakers are built, operate, and wear and the selection and utilization of these parameter has been informed by review and analysis of circuit breaker IDB data.

The circuit breaker replacement rank (CBRR) is a function combining three major indices:

• Functionality Index: How likely will the breaker be fit to continue operation?
• O&M Index: What is the anticipated O&M cost that the breaker might incur?
• Consequence Index: What are the consequences if the breaker fails to perform its function?

The method employs a relative ranking concept. The worst performer is assigned a maximum value of 100 and all remaining breakers are scaled proportionally. Figure 2-21 highlights the raw data curation, loading, consolidation and replacement ranking application process.

The CBRR algorithms utilize various weightings and thresholds. Analyses of circuit breaker IDB data using some of the metrics described earlier has informed and improved the selection of these values. Member utilities can work with EPRI to adapt the replacement ranking methodology and implement it to suit their unique situation and requirements.

EPRI releases a new version of the circuit breaker replacement software every year, which is available to funders of Program 34 or 34.002.