Distribution automation takes control beyond the substation, along the medium-voltage feeders. It uses reclosers, sectionalizers, remote-controlled switches and faulted circuit indicators, communicating with SCADA or with each other, to isolate faults, restore service to the healthy sections (FLISR) and regulate voltage and reactive power.
What distribution automation is
Most of the outages customers experience originate in the medium-voltage distribution network, not in the substations. That is why distribution automation, also called feeder automation, places sensors, switching devices with their own controls and communications along the feeders. Its goal is to find faults faster, isolate only the affected section and restore service to the rest without waiting for the line crew.
It complements automation inside the substation: the feeder relay and the bay controller remain the origin of protection, and network automation acts downstream.
The devices on the feeder
| Device | What it does | Reference standard |
|---|---|---|
| Recloser | Interrupts the fault and recloses automatically a programmed number of times before locking out | IEEE C37.60 / IEC 62271-111 |
| Sectionalizer | Counts the operations of the upstream recloser and opens during the dead time, without interrupting fault current | IEEE C37.63 |
| Remote-controlled switch or load-break switch | Opens and closes under load by remote command; isolates sections and closes tie points | Depends on the device |
| Faulted circuit indicator | Shows whether fault current passed through that point, locally or to SCADA | IEEE 495 |
| Voltage regulator and capacitor bank | Hold the feeder voltage and compensate reactive power | Depends on the device |
The recloser is the central device. A faulted circuit indicator, like those in the guide Easergy Flite, Horstmann and SEL AR360 fault indicators, costs much less and, with communications, tells within minutes which section is faulted.
FLISR: isolate and restore
The best-known distribution automation function is FLISR: fault location, isolation and service restoration. On a permanent fault it identifies the section, isolates it by opening the devices that bound it and restores service to the healthy sections, upstream ones from their own source and downstream ones from a neighboring feeder, by closing a tie point.
- 01DetectionThe recloser or the feeder relay opens and uses up its reclosing attempts
- 02LocationIndicators and switching devices report where the fault current passed
- 03IsolationThe devices bounding the faulted section are opened
- 04Upstream restorationThe device that cleared the fault is closed
- 05Downstream restorationThe tie point with the neighboring feeder is closed, if it has capacity
It can be centralized (the control center DMS decides), distributed (the recloser controls decide among themselves) or local (each device acts on voltage and time). Each architecture, its advantages and its limits are covered in FLISR: self-healing distribution networks.
Other functions
- Volt/VAR control. Voltage regulators and capacitor banks with automatic control hold the voltage along the feeder. In centralized systems, the DMS coordinates them to reduce losses.
- Automatic transfer. In networks with two sources, a medium-voltage automatic transfer moves the load to the available source.
- Network monitoring. Load measurements at points along the feeder, device alarms and status that feed the network model at the control center.
- Settings group change. When the network is reconfigured, reclosers may need another settings group to stay coordinated with the new source.
Communications
Distribution automation depends on links that run for miles: radio, cellular networks and fiber optics where available. The most used protocol to SCADA is DNP3 (IEEE 1815), because of its time-stamped event handling and its tolerance of slow links; IEC 60870-5-104 and peer-to-peer IEC 61850 are also used. The limits of each medium and how they affect automation are in radio and cellular links.
A design rule: feeder protection must never depend on communication. If the link drops, each recloser keeps protecting with its own settings; what is lost is the coordination of the restoration.
Where to start
Few utilities automate their whole network at once. The usual path is in stages, starting with the feeders that serve the most customers or perform worst on reliability indices (SAIDI, SAIFI, IEEE 1366):
- First, visibility. Reclosers and faulted circuit indicators communicating with SCADA show where the fault is, so the crew goes to the right section.
- Then, remote control. With remote-controlled switching devices, the operator isolates the section and restores from the control center without waiting for the crew.
- Finally, automation. FLISR logic, centralized or distributed, runs that sequence by itself, in seconds or minutes.
Each stage needs the previous one: automatic logic does not work if the devices do not report their status correctly or accept remote commands.
What fails in practice
- Coordination broken after reconfiguration. The neighboring feeder picks up load and the settings of its reclosers no longer match the new topology. You can check selectivity between two curves with our free relay coordination tool.
- Links that fail right during the fault, when the voltage drops or the radio loses power.
- Reclosers that lock out because of settings or unforeseen conditions; see recloser locked out.
- Different point maps between the device control and SCADA, so a status arrives with another meaning.
- Uncontrolled firmware or settings changes on devices spread across the whole network.
How it is tested
Each device is tested at its commissioning: the recloser and its control with secondary injection and verification of the reclosing sequences, the sectionalizer with its count, and the indicator with its threshold. The FLISR logic is tested first in simulation, with the real settings and the network model, and then in the field with scheduled switching. Every signal and every command is verified point to point up to SCADA.
We configure your reclosers and your automation
At Tiza Group we configure recloser controls of the main brands, their settings, groups, logic and DNP3 or IEC 60870-5-104 communications, for distribution utilities and industry. The fastest way is remote recloser configuration: we work remotely with your technician on site, anywhere in the world. For SCADA integration, see SCADA and gateway integration.
Related guides
- FLISR: self-healing distribution networks
- Recloser: what it is, parts, functions and testing
- Easergy Flite, Horstmann and SEL AR360 fault indicators
- Automatic service restoration
- Medium-voltage automatic transfer
- Radio and cellular links
- DNP3
- IEC 61850, IEC 104, DNP3 and Modbus: which one to use
- Automatic capacitor bank control at MV and HV
References
- IEC/IEEE 62271-111 (IEEE C37.60), automatic circuit reclosers for alternating current systems up to 38 kV.
- IEEE C37.63-2024, Standard Requirements for Overhead, Pad-Mounted, Dry-Vault, and Submersible Automatic Line Sectionalizers for Alternating Current Systems up to and Including 38 kV.
- IEEE 495-2025, Standard for Testing Faulted Circuit Indicators.
- IEEE Std 1366, Guide for Electric Power Distribution Reliability Indices.
- IEEE Std 1815-2012, DNP3.
- IEEE C37.104-2022, Guide for Automatic Reclosing on AC Distribution and Transmission Lines.
Frequently asked questions
What is the difference between substation automation and distribution automation?
Substation automation works inside one fenced site, with IEDs connected by a fast local network. Distribution automation spreads devices over miles of feeder, with radio, cellular or fiber communications, and its main goal is to reduce the duration and extent of outages.
Is a recloser already distribution automation?
It is the first step: it opens on a fault and recloses by itself. It becomes network automation when it communicates with SCADA or with other devices and takes part in an isolation and restoration logic involving several points on the feeder.
Does FLISR work without communications?
There is a local variant in which each device acts on the presence or absence of voltage on either side and on coordinated time delays. It is simpler, but it produces more operations and does not check whether the neighboring feeder can pick up the load. The centralized and distributed variants do need communications.