Fault passage indicators: locate faults faster on MV networks.

On a medium-voltage distribution network, every minute of outage has a cost: customer satisfaction, utility performance indicators, crews mobilised. When a fault hits a feeder, everything comes down to one question: where? Fault passage indicators (FPIs) — also known as fault circuit indicators (FCIs) — answer it in seconds instead of hours of patrolling.

This article explains what a fault passage indicator is, why fault location is so difficult on medium-voltage networks, how these devices work, and what they concretely bring to utilities across West Africa.

01 — DefinitionWhat is a fault passage indicator?

A fault passage indicator is a device installed on an MV overhead line or an underground cable. Its function is simple but decisive: detect the passage of a fault current at a specific point of the network and signal it. By comparing the points that "saw" the fault pass with those that did not, the operator immediately narrows down the faulted section.

Modern models detect short circuits and earth faults, provide local and remote signalling, and communicate with a supervision system.

02 — The problemWhy fault location is difficult

Locating a fault on an MV overhead network runs into several field realities:

• Very long feeders. Feeders often extend over tens of kilometres, especially in rural areas: patrolling without instrumentation takes hours.
• Complex topology. Multiple branches and interconnections make isolating the faulted segment harder.
• Limited visibility. Conventional protection tells you a fault exists, but rarely where it is exactly.
• High outage cost. Every interruption weighs on service quality and operating expenses.

03 — How it worksInside a fault passage indicator

The principle relies on continuous monitoring of the line current.

In normal operation

The indicator measures load current and stays idle, with no signalling.

When a fault occurs

When the current exceeds a predefined threshold, the device recognises the abnormal condition and records the event — phase-to-phase short circuit, phase-to-ground fault or three-phase short circuit.

Fault indication

Once the fault is detected, the indicator announces it: highly visible flashing LED, mechanical flag, remote alarm and event report to the control centre. Crews immediately know whether the fault passed through this point of the feeder.

04 — BenefitsWhat faster location changes

• Shorter outage duration. Quickly identifying the faulted section lets crews isolate and re-energise healthy segments faster: SAIDI and SAIFI improve.
• Lower operating costs. Fewer patrols and manual inspections: less labour, fewer vehicle deployments, less maintenance.
• Better customer satisfaction. Shorter outages mean fewer complaints.
• A more resilient network. Faster fault response strengthens overall distribution reliability.

05 — Smart GridIntegration with network operation

Connected to a communication network, modern indicators automatically transmit fault information to supervision (SCADA), distribution management (DMS) and outage management (OMS) systems. The operator monitors fault conditions in real time, without sending a crew on site.

The most advanced indicators also provide GPS location, fault direction, event logging, remote configuration and cloud monitoring. Combined with distribution automation, they sharply increase situational awareness and operational efficiency. These building blocks form the foundation of the Smart Grid and feeder-automation solutions that operators deploy.

06 — The offerFour-Faith indicators distributed by Synch Power

Synch Power supplies across West Africa the full range of Four-Faith fault indicators, for overhead lines and underground cables:

• Accurate detection of short circuits and single-phase earth faults to target the affected section.
• Local and remote signalling: ultra-bright LEDs or mechanical flags, reporting to the control centre over cellular networks.
• SCADA integration and automation platforms: real-time supervision, remote diagnostics, centralised asset management.
• Robustness and long life: line-current powered with backup battery, built for harsh outdoor environments, over 10 years maintenance-free.
• Flexible communication: 4G, 3G, LoRa — reliable connectivity across large territories.

Typical applications: 5–38 kV overhead networks, underground cables, Smart Grid modernisation projects, rural electrification, distribution automation and FLISR, fault location and outage management. Explore the detailed product catalogue.