SMS as a Resilient Backup Communication Channel for Critical Infrastructure

In modern SCADA and distributed automation systems, communication reliability is fundamental. However, even well-designed infrastructures can experience disruptions – whether due to mobile data network outages, LAN/WAN failures, or cyber incidents. In such scenarios, the ability to maintain minimal yet critical communication becomes essential for operational continuity and grid resilience.

Both the WCC Lite and eRTU remote terminal units are equipped with integrated cellular modems supporting SMS functionality, enabling an independent, low-bandwidth communication channel that operates even when IP-based communication is unavailable.

SMS as a Fallback Communication Layer

SMS communication provides a highly reliable out-of-band control path that is independent of standard TCP/IP-based SCADA communication. While mobile data or LAN connectivity may fail, SMS often remains operational due to its lower network requirements and priority handling in telecom infrastructure.

With Elseta RTUs, operators can:

• Send control commands via SMS to execute predefined actions (e.g., open/close breakers, reset alarms, switch operational modes)
• Request real-time data snapshots such as voltage, current, device status, or fault indicators
• Receive unsolicited alarm notifications triggered by critical events when all primary communication channels are unavailable

This ensures that even in worst-case communication failures, operators retain situational awareness and limited control over remote assets.

Practical Application Scenarios

1. Substation Communication Failure
If a secondary substation loses its fiber or VPN connection to SCADA, the RTU can automatically switch to SMS alarm mode. Upon detecting a fault (e.g., transformer overload or breaker trip), the unit sends an SMS alert directly to operators. The operator can then reply with a command such as “STATUS” to retrieve key measurements or “RESET FAULT” to initiate corrective action.

2. Remote Renewable Energy Site
In solar or wind installations where mobile data coverage is unstable, SMS acts as a backup channel. For example, if the data connection drops, the WCC Lite can still notify operators about inverter faults or production anomalies via SMS, ensuring that maintenance teams are dispatched without delay.

3. Industrial Facility Emergency Control
In industrial environments, loss of LAN connectivity due to network misconfiguration or hardware failure can isolate field equipment. Using SMS, operators can still issue critical commands such as shutting down equipment, restarting systems, or activating backup processes.

4. Cybersecurity Containment Scenario
In the event of a suspected cyberattack, IP-based communication channels may be intentionally disabled. SMS provides a secure, isolated fallback path for diagnostics and controlled recovery actions without exposing the system to further risk.

Intelligent Event-Driven SMS Logic

Thanks to built-in scripting and automation engines, both WCC Lite and eRTU can be configured to:

• Trigger SMS messages based on specific events or thresholds
• Filter and prioritize alarms to avoid unnecessary notifications
• Execute predefined logic when receiving authorized SMS commands

This transforms SMS from a simple notification tool into a fully integrated part of the control strategy.

SMS-Based RTU-to-RTU Communication for Self-Healing Grid Operation

Beyond operator interaction, Elseta RTUs can also utilize SMS as a machine-to-machine communication channel, enabling direct coordination between field devices when all conventional communication paths are unavailable. This approach extends the resilience of the system from human interaction to distributed automation logic.

Under normal conditions, RTUs exchange data over standard protocols such as IEC 60870-5-104 or DNP3 via LAN, fiber, or mobile data networks. However, during major outages—such as simultaneous loss of fiber and cellular data—this communication layer may become unavailable. In such cases, SMS can serve as a last-resort inter-RTU signaling mechanism.

Using configurable logic and scripting, RTUs can:

• Transmit fault indications and feeder status to neighboring RTUs via SMS
• Share critical states such as breaker position, voltage presence, or fault direction
• Exchange simple control signals required for coordinated switching sequences

This enables RTUs to maintain distributed decision-making capabilities even in a fully degraded communication environment.

This functionality becomes particularly important in networks implementing Fault Location, Isolation, and Service Restoration (FLISR) at the SCADA level. While FLISR is typically coordinated centrally, its effectiveness depends on reliable communication between field devices. By introducing SMS-based RTU-to-RTU communication as a fallback layer, Elseta ensures that:

• Fault information can still propagate between substations
• Switching decisions can be executed locally based on shared status
• Faulted sections can be isolated and healthy sections restored

The eRTU platform already supports self-healing network architectures with automatic reconfiguration following faults. By extending this logic over SMS, the system preserves core self-healing capabilities even when SCADA and IP-based communication are completely unavailable.

In practical terms, this means that during a large-scale communication failure:

• A fault detected by one RTU can be communicated via SMS to adjacent RTUs
• Neighboring devices can validate network conditions and execute coordinated switching
• Service restoration can proceed automatically, maintaining supply to unaffected areas

Summary

By integrating SMS not only as a human interface but also as a fallback machine-to-machine communication layer, Elseta’s WCC Lite and eRTU provide a uniquely resilient approach to grid automation. Even in the complete absence of LAN, WAN, or mobile data connectivity, critical information exchange, control actions, and self-healing grid functionality can continue—ensuring maximum reliability of modern distribution networks.