IEC 60870-5-104 (often shortened to IEC 104) is a telecontrol protocol used widely in electrical utilities and infrastructure SCADA, especially across Europe and much of Asia. It carries the IEC 60870-5-101 application data over standard TCP/IP networks, giving power grids and pipelines a standardized way to move telemetry and commands between control centers and remote stations.
IEC 60870-5-104 in one line: IEC 60870-5-104 is an international telecontrol standard that transports IEC 60870-5-101 application messages (ASDUs) over TCP/IP, enabling utility and infrastructure SCADA masters to exchange measurements, status, and control commands with remote RTUs and substations over routable networks.
The IEC 60870-5 series defines companion standards for telecontrol. IEC 60870-5-101 specifies the application layer and message formats for serial links, while IEC 60870-5-104 keeps that same application model but replaces the serial transport with a TCP/IP profile. The data itself is carried in Application Service Data Units (ASDUs), each identified by a type (single-point status, measured value, command, etc.) and a Cause of Transmission that explains why the message was sent - spontaneous change, periodic update, interrogation response, or command confirmation.
This structure gives -104 a rich, self-describing model of telemetry and control that maps naturally onto grid and substation operations: breaker positions, analog measurements, tap-changer commands, and time-tagged events all have defined ASDU types. Time tagging with high resolution supports sequence-of-events analysis after a disturbance.
IEC 104 is the workhorse telecontrol protocol for electricity transmission and distribution SCADA in many regions, and it appears in water, gas, and pipeline infrastructure that shares utility heritage. Control centers act as masters (controlling stations) that poll and command RTUs and gateways at substations and remote sites (controlled stations) over the operator's wide-area network.
Because -104 already runs over TCP/IP, integrating it into a modern SCADA or data platform is largely a matter of protocol support and network design. A gateway or SCADA driver terminates the -104 session and maps ASDUs to internal tags, which can then be historized, visualized, and forwarded. For operators consolidating multi-site data, a cloud platform can ingest values gatewayed out of an IEC 104 system so grid-adjacent oil and gas assets - pipeline cathodic protection, remote pump stations, tie-in metering - share one dashboard and historian with the rest of the estate.
They share the same application layer and message model (ASDUs), but IEC 60870-5-101 runs over serial links while IEC 60870-5-104 runs the same messages over TCP/IP networks. In practice, -104 is used where an IP wide-area network is available, and -101 where legacy serial telecontrol links remain.
It is most common in electrical transmission and distribution SCADA, particularly in Europe and Asia, and in water, gas, and pipeline infrastructure with utility heritage. It links control centers with substation and remote-station RTUs over the operator's wide-area IP network.
Both are telecontrol/SCADA protocols with event reporting, time stamping, and interrogation, serving similar roles. IEC 60870-5-104 dominates European and Asian utilities, while DNP3 is more common in North American electric and water utilities. The choice is usually driven by region, existing installed base, and utility standards.
Primary references from the standards bodies and regulators that define this topic:
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