IEC 60870-5 is the European family of telecontrol protocols that carry SCADA data between control centres and substations. IEC 60870-5-101 runs over serial links; IEC 60870-5-104 carries the same application layer over TCP/IP. It is the power-grid counterpart to DNP3 (IEEE 1815), and it gains security from the IEC 62351 series.
IEC 60870-5-101 The companion standard for basic telecontrol over serial links between a control centre and an outstation (RTU). Defines the application data — measurements, status, commands — independent of the transport.
IEC 60870-5-104 Carries the same 101 application layer over standard TCP/IP transport. The protocol of choice for modern wide-area SCADA, often shortened to IEC 104.
IEC 60870-5-103 A companion standard for the informative interface to protection relays in substations.
IEC 60870-6 (TASE.2 / ICCP) The inter-control-centre communications protocol (ICCP), for data exchange between utility control centres.
A grid control centre may oversee hundreds of substations spread across a region. It needs to read their measurements, see their status and send commands — reliably, over whatever link is available. IEC 60870-5 is the European family of telecontrol protocols built for exactly that conversation, and in modern networks its member IEC 60870-5-104 is everywhere.
The clever part of the family is the split between what is sent and how. IEC 60870-5-101 defines the application data — measured values, single and double points, commands — as typed information objects carried in ASDUs, each with an address and a cause of transmission. That data definition is transport-independent. 60870-5-101 carries it over serial links; 60870-5-104 wraps the identical application layer in TCP/IP, so the same SCADA logic runs over routed wide-area networks. Inside substations, 60870-5-103 interfaces to protection relays, and IEC 60870-6 (ICCP/TASE.2) handles centre-to-centre exchange.
60870-5 is not alone. DNP3 (IEEE 1815) shares a common origin and does the same job; 60870-5 dominates in Europe, DNP3 in North America, and many devices speak both. The family’s weakness is age: 60870-5-104 was specified without security, so authentication and encryption are added by the IEC 62351 series — now mandatory thinking given how exposed a routed telecontrol link is. This is the same control-system security discipline as IEC 62443.
It is easy to confuse 60870-5 with IEC 61850, but they solve different problems. 61850 is the fast, model-rich communication inside a substation; 60870-5-104 is the wide-area link reporting that substation upward to the control centre. A modern station typically runs 61850 internally and 60870-5-104 to the centre, with OPC UA (IEC 62541) bridging to enterprise and analytics systems.