IEC 60870-5-101:2003

Overview

IEC 60870-5-101:2003 - “Telecontrol equipment and systems – Part 5-101: Transmission protocols – Companion standard for basic telecontrol tasks” - is an international standard that defines a companion transmission protocol for telecontrol (SCADA) systems using coded bit serial data transmission. It specifies selections from the IEC 60870-5 series (physical, link and application layers) to enable interoperability among telecontrol devices used for geographically distributed monitoring and control. This standard is widely used in power systems and is of high relevance to the Smart Grid.

Key Topics

• Protocol structure: Defined layering (physical, link, application) and selected provisions from the IEC 60870-5 family.
• Physical layer interfaces: Selections include serial interfaces and compatibility with ITU‑T interfaces (e.g., V.24/V.28, X.24/X.27) and switched-network interfaces.
• Link layer: Frame formats and link transmission procedures, state transition diagrams, timeouts and reset behaviors for reliable serial links.
• Application layer & ASDU: Structure and coding of the Application Service Data Unit (ASDU), including type identification, variable structure qualifiers, cause of transmission, common address of ASDUs, and information object addressing.
• Information object types: Standardized data types for process values and control - single/double-point status, measured values (normalized, scaled, floating point), bitstrings, step positions, integrated totals, and events.
• Time-stamping: Use of standardized time tags (e.g., CP56Time2a) for events and measurements.
• Basic application functions: Station interrogation, polling, cyclic transmission, event acquisition, command transmission, parameter loading, clock sync, file transfer and test procedures.
• Interoperability guidance: Recommendations for device roles (station, concentrator), network configuration and conformance to ensure multi-vendor compatibility.

Applications

• Utility SCADA and telecontrol systems for electrical substations, generation sites and distribution networks.
• Remote terminal units (RTUs), protocol converters and master stations implementing serial telecontrol links.
• Smart Grid projects where reliable, standardized telemetry and command exchange are required across legacy serial links or where interoperability with IEC 60870-5 family protocols is required.
• System integrators, device manufacturers and network engineers implementing reliable remote monitoring, event reporting and remote control functions.

Who Should Use It

• Power utilities, substation engineers and operators
• SCADA/RTU manufacturers and firmware developers
• System integrators and consultants for Smart Grid deployments
• Test labs and compliance engineers verifying protocol conformance

Related Standards

• Other parts of the IEC 60870-5 series (physical, link, application definitions and companion standards) - IEC 60870-5-101 defines the serial/companion selection; networked/ TCP‑IP variants and additional parts expand on procedures and services.

Keywords: IEC 60870-5-101, telecontrol, transmission protocols, SCADA, RTU, Smart Grid, ASDU, serial telemetry, interoperability, IEC 60870-5.