Destressing the Medium-Voltage Grid

Distribution system failures account for 92% of all electric service interruptions in the U.S. according to the American Society of Civil Engineers (ASCE), who explained that electricity delivery in the U.S. depends on an aging and complex patchwork of power generation facilities, 600,000 miles (about 965606.4 km) of backbone transmission lines (240,000 miles (about 386242.56 km) of which are considered high-voltage lines or ≥ 230 Kilovolts), and around 5.5 million miles (about 8851392 km) of local distribution lines. What is more, the infrastructure depends on aging assets––many well beyond their projected usable lifespan.

The distribution grid carries an average of 13kV of energy and is one of the energy infrastructure’s weakest links. This medium-voltage grid carries power from high-voltage transmission systems to the low voltage grid edge via both overhead and underground lines. Stresses from increased interconnection of distributed energy resources (DER), electric vehicles (EV), the increased frequency of intense storms and extreme temperatures , and rapid population growth are pushing the grid to its limits and causing increases in faults and outages. Costs to consumers and businesses from these failures continue to rise. According to 2020 research nationwide, residential and business customers will experience $85 billion (about $260 per person in the US) in annual losses from unreliable electricity. 

Utilities are under extreme pressure to effectively manage distribution grid realities while also meeting mandates for improved System Average Interruption Duration Index (SAIDI) scores. So much so that the Federal Energy Regulatory Committee ruling #881 requires that utilities “...use ambient-adjusted ratings as the basis for evaluating near-term transmission service to increase the accuracy of near-term line ratings”.

Dynamic Line Rating (DLR) Sensors Deliver Grid Reliability and Reduce Costs

Line sensors give utilities immediate and tangible reliability improvements by alerting operators about potential failures before they occur, pinpointing distribution grid failures and maximizing repair crew efficiency while reducing time to restoration of service for customers. Using intelligent line sensors on the distribution grid, utilities can achieve impressive, money saving results. A recent survey of Ampacimon customers world-wide found that using DLR sensors, they achieved:

• Feeder Restoration Case Mix Index (CMI) reduction of 20% - 37%.
• Related Annual SAIDI reductions of 7% - 15% 
• Reduced SAIDI minutes, saving between $200k - $1m per minute of outage. 

Accelerated Fault Resolution

Dynamic Line Ratings provide a granular view of the grid, narrowing patrol areas and enabling crews to quickly locate and focus on problem areas. Line sensors are a proven method to improve utility reliability and cost metrics system average interruption duration index (SAIDI), and operations and maintenance (O&M) costs in four key areas. 

1. Accelerated Fault Response:
   • Faults are identified and addressed swiftly, minimizing downtime.
   • Precision in fault pinpointing ensures targeted responses.

2. Proactive Asset Condition Assessment:
   • Potential failures are identified before they occur.
   • Timely maintenance prevents costly disruptions.

3. Enhanced Situational Awareness:
   • Risks from the surrounding environment are comprehensively assessed in real-time.
   • This allows for proactive measures against potential grid issues.

4. Dynamic Power Flow Optimization:
   • Visibility into dynamic limits ensures efficient power flow.
   • Optimal utilization and loading insights lead to enhanced grid performance.

Distribution System Fault Detection Enables Proactive Maintenance

DLR sensors can indicate and pinpoint potential problems before faults or outages occur. Collecting and analyzing sensor data shows system anomalies, which can be used in conjunction with advanced distribution management systems (ADMS) to avoid potential outages from faulty or failing assets. With DLRs in place, a baseline of power flow can be established. Anomalies to the baseline indicate potential problems from vegetation contact, high winds, line sag, and other sources of equipment failure. Real-time alerts and reports provide operators with insight into grid segments with high levels of anomalies and enable them to make informed maintenance decisions. 

Preempting outages due to vegetation contact and equipment failure provides significant system average interruption frequency index (SAIFI) improvements and O&M savings. And by preventing future outages utilities also improve long term SAIDI metrics.

Intelligent line sensing improves overall grid performance, reduces operations and maintenance costs, and minimizes power interruptions for better overall reliability. Using sensors to monitor high probability areas of failure helps operations and planning teams focus on the most critical areas of grid management, improving efficiency. Finally, reliability improvements and customer satisfaction improvements not only save money for the utility, but also reduced costs related to downtime for the customer––who counts on the utility to provide reliable power. 

The use of DLR sensors is one grid modernization initiative that provides increased reliability and reduced O&M costs quickly, improving overall ROI (return on investment). DLRs combined with analytics can balance long-term grid modernization goals with shorter-term improvements in cost and gains in reliability

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(Originally ran in Utility Dive)

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