Integrating Modbus RTU Calorimeter into IEC 61850 System

About ELES d.o.o.

ELES d.o.o. (Elektro-Slovenija) is the state-owned electricity transmission (and distribution) system operator in Slovenia. As the legal and technical backbone of the national grid, ELES is responsible for ensuring safe, reliable, and uninterrupted power transmission across Slovenia’s high-voltage network, operating at 400 kV, 220 kV, and parts of 110 kV. The company’s mission also encompasses innovation and digitalisation in energy systems to support smart grid evolution and increased operational efficiency.

The Challenge

ELES deployed a calorimeter (a field instrument measuring thermal energy or related parameters) in a part of their grid infrastructure that communicated over Modbus RTU, a widely-used serial protocol in industrial automation. However, ELES’s central operational system — Siemens SICAM PAS — relies on the modern IEC 61850 communication standard for substation automation and power system integration.

This created a protocol mismatch:

• Calorimeter: Modbus RTU interface
• SICAM PAS: IEC 61850 substation system

Without a conversion layer, the calorimeter’s data could not be natively recognised or processed by Siemens SICAM PAS.

Elseta WCC Lite as Protocol Converter

To bridge this gap, ELES selected Elseta’s WCC Lite — a compact remote terminal unit and protocol converter — to act as the intermediary between the Modbus RTU device and the IEC 61850-based automation system.

How It Works Technically

1. Connection to Field Device
   The calorimeter communicates its measurement values over Modbus RTU (serial).
   The WCC Lite interfaces directly with this device, acting as a Modbus master and collecting process data.
2. Protocol Conversion at the Edge
   WCC Lite translates Modbus registers and statuses into IEC 61850 data models, including appropriate data objects and reporting attributes that the SICAM PAS system can interpret.
   This involves mapping modular Modbus tags to standardized IEC 61850 datasets.
3. Communication to SICAM PAS
   Using its built-in IEC 61850 client/server stacks, WCC Lite publishes the converted data to the Siemens SICAM PAS system (or another IEC 61850 SCADA client) over the substation IP network.
4. Data Integration and Operations
   The calorimeter’s readings (e.g., energy flow, temperatures, diagnostics) now appear seamlessly within the Siemens automation environment — usable for monitoring, historical logging, alarms, and model-based control logic.

Benefits and Value Delivered

Leveraging Existing Infrastructure

Instead of replacing the existing calorimeter or deploying full IEC 61850-ready hardware, ELES used the WCC Lite as a fit-for-purpose gateway, extending the life of legacy field equipment. This approach avoided unnecessary device retrofits —saving capital expenditure and avoiding system downtime tied to hardware replacement.

Cost savings:

• Eliminate the need for expensive new hardware deployments.
• Avoid engineering redesign costs to convert the entire installation to IEC 61850.
• Leverage WCC Lite’s combined RTU + protocol conversion capability for a minimal footprint.

Future-Proofing and Scalability

With WCC Lite supporting both Modbus and IEC 61850 (among other protocols), ELES has a scalable integration layer that can easily integrate additional legacy devices if needed. With the WCC Lite already present, ELES has the ability to integrate additional new devices in the future with any of the industry’s common protocols without the IEC 61850 compatibility issues.

Conclusion

By choosing Elseta’s WCC Lite as the protocol converter, ELES successfully integrated a Modbus-based calorimeter into its IEC 61850 Siemens SICAM PAS environment — achieving seamless interoperability, operational efficiency, and cost savings. This use case exemplifies how utilities can modernise substation automation and asset communication without discarding legacy equipment, leveraging modular, multi-protocol field devices to bridge industry communication standards.