Fighting Power Outages with FLISR: How it Works

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Although power outage worries will always loom over electricity companies, especially as blackouts grow more frequent in many parts of the world, these risks can be mitigated using grid modernization technology applied to FLISR (fault location, isolation, and service restoration). It is one of the major processes in distribution network management for mitigating faults to improve grid reliability and manage outages.

Even short power outages can cause costly chaos for both electricity companies and customers. By reducing outages’ frequency and duration, electricity companies can prevent productivity and financial losses. Over a one-year period, FLISR processes reduced the number of customers interrupted (CI) by 55 percent and reduced customer minutes of interruption (CMI) by 53% per outage event, according to a U.S. report.

See how to bounce back from outages with FLISR

The first step in FLISR is detecting faults and identifying their location. There are three main types of outages:

  • Unplanned outages: These are the most common types of outages and can happen for many reasons, including equipment failure, human error, and wildlife.
  • Planned outages: Planned outages are necessary for tasks like maintenance, system upgrades, or replacing old or damaged equipment.
  • Outages caused by major events like natural disasters or severe weather: These types of outages, for example, flooding and wildfire, can cause severe, widespread damage to the grid. This damage often affects a large geographical area, as occurred recently during wildfires in California and Australia and a tsunami in Japan.

Accurately locating the fault is a prerequisite for fixing it. Electricity companies are often dependent on customers for fault detection and localization. However, using improved FLISR processes built on connected technology, electricity companies can significantly reduce the time needed to locate outages. Advanced distribution management systems’ (ADMS) FLISR functionalities immediately identify faults and then troubleshoot these faults to drastically reduce the outage duration and the number of impacted customers.

ADMS functionalities for FLISR processes minimize the duration of faults and the outages’ impact by automatically isolating faults from the rest of the power system. They also reconfigure the system to quickly re-energize the grid by supplying power to the de-energized parts of the distribution network.

Isolation and service restoration both focus on minimizing outages’ effect by restoring power quickly. Additional ADMS functionalities like OMS (outage management system) and CM (crew management) make this possible by optimizing resource mobilization to rapidly and accurately direct maintenance crews to the outage location.

The “improved” FLISR process coordinates the automatic operations of equipment like reclosers, sectionalizers, and RMUs and the manual operations by field crews. It is a functionality of the smart grid and dependent upon intelligent devices like sensors, relays, and smart meters, which can be connected to advanced analytics and management tools like ADMS.

Two of the main use cases are:

  • Underground ring type networks: These networks use ring main units (RMUs) as electrical distribution switching devices. Their loop architecture allows for faster restoration and fault identification and can automatically reconfigure the network after an outage. They are most often used in urban areas, although in some cases electricity companies use a combination of underground and overhead networks.
  • Overhead radial networks: This type of network topology uses reclosers and sectionalizers as electrical distribution switching devices. Overhead radial distribution networks are the simplest topology for widely distributed loads over a large area, for example rural MV networks, but they are particularly vulnerable to outages, and use a single path for loads. A single fault can result in the complete loss of supply to the load. Using outage management technology, such as smart reclosers, can clear faults near where they occur and communicate a fault occurrence to the outage management center for faster restoration.

The use of distributed energy resources (DERs) is putting additional stress on the power grid and a decentralized grid makes network management more complex. This means that more than ever, electricity companies must prioritize power reliability and restoration using “improved” FLISR processes.

Learn more in our use case on grid reliability and fault management.


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  • John Mueller

    3 years ago

    Your paper does not deal with the much more widespread outages that are caused by sudden swings in loads when one generating unit suffers a fault and goes off-line. The resultant sudden surge in load to other generating units in a region or across grids tied together has caused outages affecting hundreds of million customers.
    The required resilience comes from de-coupling the grids or segments of the grid and using HV DC interties between them. These have proven to be safe and very successful. The intertie voltage may drop below its normal range but the lock-step requirement to maintain the frequency is compartmentalized without a severe disruption beyond the single compartment. When major generating units go off-line, restart and reconnection to the grid can take hours or even days.

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