Distribution Automation Applications

Fault Location, Isolation, and Service Restoration (FLISR)

Automatically minimize the impact of outages—within seconds.


How Does FLISR Work?

Permanent faults are de-energized by protective relays that open and lock out breakers or reclosers. This lockout creates an outage for the faulted zone, any customers downline of the faulted zone, and—if any kind of miscoordination occurs—customers upline of the faulted zone, as well. FLISR’s purpose is to locate that fault, isolate it by opening bounding switching devices, and restore as much load as possible by closing one or more open points between the faulted feeder and neighboring feeders. FLISR solutions can most simply be divided into the following three categories:


Many distribution feeders are protected by recloser controls that are not augmented with a communications system. It is possible to implement FLISR functionality using local sensing of voltage and current, coupled with close-onto-fault relay logic. This noncommunication FLISR solution allows reclosers and switches located on a two-feeder radial loop to take restoration action after a permanent fault has resulted in lockout. This solution is best paired with a noncommunication high-density coordination scheme, which automatically resolves planned or unplanned miscoordinations.

Peer-to-Peer With Communications

The peer-to-peer FLISR solution is designed for similar system topologies as the noncommunication solution (a two-feeder radial loop), but the addition of a communications system eliminates the necessity of close-onto-fault logic, and if the communications system is protection-speed, the restoration time can be drastically improved. This relay-to-relay solution, often called high-speed loop sectionalizing, is a simple solution that places no limits on the number of switches or reclosers in series on a radial loop.

Regional and Centralized

More centralized FLISR solutions utilize software and computing platforms capable of communicating with breakers, reclosers, and switches to gain wide-area system visibility. Designed to scale to hundreds or thousands of switching devices, these FLISR solutions are generally deployed in either the substation or distribution control center. Software-based FLISR solutions make it possible to rapidly and economically deploy FLISR across a wide area containing complex and unique distribution feeder topologies.

FLISR Without Communication

Consider the following event: a permanent fault occurs between Recloser 1 (R1) and Recloser 2 (R2) on a two-feeder radial loop. R1 will observe this fault, attempt to clear the fault according to its reclose settings, and eventually lock out when those reclose attempts are unsuccessful.

The open tie point recloser (R3) will sense the loss of voltage caused by the opening of R1, and after sufficient time has passed, it will automatically close, re-energizing the line in the direction of R2. The closing of R3 re-energizes the permanent fault location. This is known as close-onto-fault logic.

Once R3 closes, R2 will observe fault current and will immediately trip and lock out. This results in an isolated permanent fault zone between R1 and R2, and restored load between R3 and R3.

Without this FLISR implementation, the outage created by this permanent fault is larger than it needs to be and could take hours to detect and mitigate. Enabling switching devices to detect the outage using local sensing and logic reduces the outage reaction time to minutes.

Related Products

Recloser Controls

SEL FLISR Solutions

Distribution Management System (DMS)

Our secure, container-based platform for operational technology environments, SEL Blueframe, provides several application suites. The DMS application suite includes a FLISR software package that allows utilities to clearly visualize their distribution system, monitor the status of field devices, issue commands and access reports. This wide-area system visibility and software-based FLISR deployment enable simple scalability for up to thousands of feeders on both overhead and underground systems.

Automation Controllers and Communication

SEL automation controllers and computing platforms make it possible to collect IED data across a wide area using many different protocols. Distribution automation solutions running on these platforms make that data visible and actionable, capable of taking automated action to improve the efficiency and reliability of the distribution system.

SEL Distribution automation solutions are designed to support many different communications technologies, including the SEL-3061 Cellular Router and SEL-3031 Serial Radio Transceiver. SEL’s wireless products make it possible to access the large quantity of data available in modern IEDs quickly and efficiently, employing that data in solutions like DMS FLISR.

Recloser Controls

Our recloser controls improve system reliability by clearing faults and isolating outages to the smallest possible section of the system. Combined with additional protection and/or communication devices, this FLISR solution can cut response time down to milliseconds.

SEL recloser controls offer single- and three-phase tripping and are compatible with many recloser models.

Proven Reliability and Lifetime Support

Every SEL solution comes with the most reliable devices and best warranty in the electric power industry—plus free technical support for SEL products and systems.

We've collaborated closely with our customers since the company was founded nearly 40 years ago. And it’s a major reason why we’re North America’s most trusted provider of protective relays and ranked #1 by international utilities in price, service, and support.

SEL devices are designed for a working life of at least 20 years. Every SEL-manufactured device comes with a 10-year warranty—the best in the industry. If it fails under warranty, repair and replacement are free.

Our products are designed to withstand the world’s most challenging environments, exceeding all industry standards for temperature, shock, and electric stress. An optional conformal coating gives electronic components an extra level of protection against contaminants in extreme environments.

All SEL electronic products are designed, tested, and manufactured in North America, in facilities that we own and operate. We practice secure supply chain management, and our quality management system is certified to ISO 9001 requirements .

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SEL support teams are stationed in regional offices around the world and staffed with application engineers who are experts in our products and in power system applications.

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