Fault location, isolation, and service restoration (FLISR) is quickly becoming one of the hottest applications in distribution automation.

Utilities including Southern California Edison, Southern Company, and San Diego Gas and Electric are transitioning FLISR projects from pilots to large-scale rollouts. FLISR is a distribution automation application that networks groups of switches on a feeder to vastly improve the reliability of utility delivered power by “localizing” outages. Localizing restores power to the majority of an affected circuit, minimizing interruptions to the customers on the faulted portion of the line between the two most local automated switches.

FLISR applications can utilize decentralized, substation, or control center intelligence to locate, isolate, reconfigure, and restore power to healthy sections of a circuit. Each FLISR approach has benefits and drawbacks.




Decentralized (peer to peer


Fastest restoration

Low integration cost

Requires least bandwidth


Cannot balance system interests during major events (storms).

Should still report status on backhaul communications systems



Greater consideration for system stability

Processed information requires lower bandwidth backhaul communication

Requires purchase of intelligent devices for substation

Should still report status on backhaul communications systems

Control Center

Full system view for restoration

Integration with DMS can simplify OMS information transfer

Slowest restoration times

Requires the most bandwidth

Requires a DMS

Source: GTM Research

One Size Does Not Fit All

It is unlikely that any one of these approaches will be the sole preferred technique for utilities. There are too many differences between various utilities -- and even within an individual utility -- to justify a universal solution. Some utilities will determine whether a limited deployment of intelligent switches in a decentralized or substation organization will be sufficient to improve the worst-performing feeders without complicated integration efforts, while other utilities will look toward a distribution management system (DMS) to implement FLISR service-area wide.

Customer Classes

Different customer needs within a particular service area warrant different FLISR approaches. All utility customers would appreciate improved reliability from fewer and shorter interruptions, but only select commercial and industrial (C&I) customers experience major losses during an interruption. For these customers, a simple FLISR restoration isn’t fast enough. According to IEEE, an interruption of 10 cycles can cause production and motors at some factories to halt and require restarting. Just one of these interruptions can cost a C&I customer hundreds of thousands or even millions of dollars in lost production or revenue.

Cost of a One Hour Interruption in Electrical Service (by Industry)


Average Cost of the 1-Hour Interruption

Cellular Communications


Telephone Ticket Sales


Airline Reservation System


Semiconductor Manufacturer


Credit Card Operation


Brokerage Operation


Source: Galvin Electricity Initiative


The Hybrid Approach

Over the next two decades, individual utilities will use various combinations of FLISR approaches across their service area to create reliability tiers to maximize customer and utility value. C&I customers would be able to pay to have their local switches organized into a peer-to-peer, ultra-fast decentralized system utilizing deterministic communications, while consumers could opt to save money with a slower reconfiguration plan that runs through the control center DMS or substation. San Diego Gas and Electric plans to implement a variant of a tiered reliability program for its C&I customers by 2020.

The creation of reliability tiers could introduce new utility revenue models and allow various C&I ventures to scale down uninterruptable power systems and back-up generators to lower consumers' overall energy costs.



Ben Kellison is an analyst with GTM Research who is working on a broader distribution automation report.  If you have any additional insights on this topic, please contact [email protected].