What is IEC 60870?

IEC 60870 is a family of communication standards used in telecontrol systems. Its primary purpose is to provide reliable communication of process information and control commands between devices located at remote sites and a central control system.

For example, in an electrical distribution center, a SCADA system can receive circuit breaker statuses, measurement values, alarm information, and other process data from RTU or IED devices located at different substations. Control commands can also be sent from the central system to the remote site over the same communication infrastructure.

For this reason, IEC 60870 has an important role, particularly in SCADA and telecontrol applications in the energy sector.

The IEC 60870-5 series defines transmission protocols used for telecontrol. IEC 60870-5-101 defines serial data communication for basic telecontrol tasks, while IEC 60870-5-104 defines the use of the IEC 60870-5-101 application structure over standardized TCP/IP transport profiles.

Key Features of IEC 60870

Designed for the Energy Sector

Provides a telecontrol approach particularly suited to power grids and energy automation.

Bidirectional Communication

Supports both the transmission of information from the field to the control center and the transmission of control commands from the center to the field.

Timestamped Events

Supports the transmission of status changes and events together with their time information.

Standardized Data Structure

Provides a common communication model between devices through standardized structures such as ASDU, Type Identification, COT, Common Address, and IOA.

SCADA Integration

Can be used in telecontrol applications between RTUs, IEDs, PLCs, and SCADA systems.

IP-Based Communication

IEC 60870-5-104 can make use of existing Ethernet and TCP/IP network infrastructures.

IEC 60870-5-101 and IEC 60870-5-104

IEC 60870-5-101

IEC 60870-5-101 is a serial communication standard used for basic telecontrol tasks. It is particularly used in telecontrol applications between remote stations and control centers.

  • Serial communication
  • RTU and SCADA communication
  • Status and measurement information
  • Alarm and event transmission
  • Remote control
  • Timestamped information

IEC 60870-5-104

IEC 60870-5-104 uses the telecontrol application structure of IEC 60870-5-101 over standard TCP/IP network infrastructure. It is widely encountered today in Ethernet and IP-based SCADA communication.

  • TCP/IP-based communication
  • Ethernet networks
  • SCADA and RTU communication
  • Remote station connections
  • Measurement and status information
  • Remote control

How Does IEC 60870 Work?

In IEC 60870 communication, there is generally a control center on one side and a remote station on the other. The remote station may contain an RTU, IED, PLC, or similar device.

The remote station collects information from field devices and sends it to the control center within IEC 60870 messages. The control center displays and records the received information in SCADA screens and can send commands to the remote station when necessary.

Field Devices

Circuit breakers, disconnectors, protection relays, measurement devices, PLCs, and other IEDs provide process information.

RTU / Remote Station

Collects field information and transfers it to the control center using IEC 60870 messages.

SCADA Center

Receives information from remote stations, displays and records it, and sends control commands when necessary.

Telecontrol Communication

Enables the bidirectional exchange of status, measurement, alarm, event, and control information.

IEC 60870 Data Addressing for EOS Software (I#)

In the EOS SCADA IEC 60870 client, the data address is composed of the Common Address, ASDU Type Identification, and IOA information.

I#COMMON_ADDRESS:ASDU_TYPE:IOA

Here, COMMON_ADDRESS specifies the device's Common Address value, ASDU_TYPE specifies the data type, and IOA specifies the Information Object Address value.

For example:

I#1:M_ME_TF_1:1209

In this structure, 1 is the Common Address, M_ME_TF_1 is the ASDU Type, and 1209 is the IOA value.

Different ASDU types can be used for IEC 60870 data, including single point, double point, measured value, integrated total, and various time-tagged data types.

What Data Can Be Transmitted with IEC 60870?

IEC 60870 is not limited to the transmission of numerical measurement values. Different types of process information can be transmitted, including status information, measurements, control information, and timestamped events.

Single Point Information

Used to transmit two-state information such as open/closed, running/stopped, or similar binary states of a device.

Double Point Information

Can be used in applications where more detailed state information, such as circuit breaker states, needs to be represented.

Measurement Values

Analog process values such as voltage, current, power, frequency, temperature, and similar measurements can be transmitted using different measurement formats.

Timestamped Data

The time at which an event occurred can be transmitted together with the process data using appropriate IEC 60870 time formats.

What is ASDU?

One of the fundamental structures used to carry application information in IEC 60870 communication is the ASDU. ASDU stands for Application Service Data Unit.

In simple terms, an ASDU can be thought of as a data packet that defines how the transmitted process information should be interpreted. An ASDU may contain fields such as information type, cause of transmission, common address, and information object address.

For example, when a SCADA system receives the status of a circuit breaker, the information contained in the ASDU allows the system to determine the type of data, the station from which it originated, and the information object it represents.

IOA – Information Object Address

In IEC 60870 systems, the Information Object Address (IOA) is used to identify which information object a particular process value belongs to.

We can think of an IOA as an address in everyday life. For example, an RTU may contain different circuit breakers, measurement points, and alarm information. The SCADA system can determine which information object is being transmitted through a specific IOA.

Therefore, correctly configuring values such as Type ID, Common Address, and IOA is important for reliable communication in IEC 60870 projects.

Cause of Transmission – COT

One of the important features of IEC 60870 is its ability to indicate why a piece of information is being transmitted. This information is called the Cause of Transmission (COT).

For example, data may be transmitted during normal cyclic transmission, or it may be sent spontaneously because a state has changed in the field. It may also be transmitted as a response to a query from a SCADA system.

  • Spontaneous: Information is transmitted automatically as a result of a change in the field.
  • Interrogated: Information is transmitted as a result of an interrogation or general interrogation.
  • Requested: Information is transmitted in response to a specific request.
  • Activation: A control or command operation is initiated.
  • Activation Confirmation: Confirmation that the initiated operation has been accepted.
  • Activation Termination: Notification that the command operation has been completed.

Timestamps and Event Recording

In power automation, it is important not only to know that an event occurred, but also when the event occurred.

IEC 60870 allows time information to be transmitted together with process data for appropriate information types. This is particularly important when analyzing circuit breaker operations, protection relay events, alarms, and status changes.

  • CP24Time2a
  • Short time information
  • Can be used for event information
  • CP56Time2a
  • More comprehensive time information
  • Widely used for timestamped events

Timestamped data is particularly useful in SOE (Sequence of Events) analysis, helping engineers examine the sequence and timing of events.

Control Operations with IEC 60870

IEC 60870 is not intended only for monitoring. With appropriate configuration and authorization, control information can be sent from the control center to remote stations.

Single Point Command

Can be used for two-state control operations such as opening or closing.

Double Point Command

Can be used in control applications where more detailed state information is required.

Setpoint Commands

Setpoint values can be transmitted using normalized, scaled, or floating-point values.

Control Operation Management

Appropriate messaging mechanisms can be used to initiate, confirm, and complete control operations.

General Interrogation – GI

One of the important operations in communication between SCADA systems and remote stations is General Interrogation (GI).

When a SCADA center establishes a connection with a remote station, it can initiate a general interrogation to obtain the current status of the station. In response, the remote station transmits the relevant current process information to the control center.

This mechanism allows the SCADA system to obtain the current state of a remote station after establishing communication. This feature is particularly important after communication interruptions and reconnections.

IEC 60870-5-104 Communication

IEC 60870-5-104 uses the telecontrol application structure of IEC 60870-5-101 over standardized TCP/IP transport profiles. Therefore, Ethernet and IP-based network infrastructures can be used in IEC 104 systems.

In IEC 104 communication, different frame types are used not only for application data but also for connection management and control of data transmission.

Connection Management

Control mechanisms are used to establish, manage, and terminate the communication connection.

Data Transmission

Process information, measurements, status changes, and commands are transmitted using ASDU structures.

Transmission Control

Protocol-level mechanisms are available to control data transmission and monitor the state of the remote communication partner.

TCP/IP Networks

Enables remote SCADA and RTU systems to communicate over standard IP-based network infrastructures.

Where is IEC 60870 Used?

IEC 60870 is one of the important standards used in telecontrol solutions, particularly in power systems distributed over large geographical areas.

Power Generation Facilities

Can be used to transmit measurement, status, alarm, and control information from power plants to control centers.

Substations

Widely used to transmit circuit breaker, disconnector, protection relay, and measurement information to SCADA centers.

Power Transmission and Distribution

Enables centralized monitoring and control of remote stations in power networks distributed across large geographical areas.

Energy Management Systems

Can be used for telecontrol communication between SCADA, EMS, and other energy management systems and field equipment.

Important Concepts When Learning IEC 60870

Understanding the following basic concepts is useful when starting to learn IEC 60870 systems:

  • RTU: Remote Terminal Unit.
  • SCADA: Central monitoring and control system.
  • ASDU: Application Service Data Unit.
  • Type Identification: Defines the type of information contained in the ASDU.
  • Common Address: Identifies the station or common address to which the ASDU belongs.
  • IOA: Address of the information object.
  • COT: Specifies the reason why the information is being transmitted.
  • CP24Time2a / CP56Time2a: Timestamp formats.
  • GI: General Interrogation operation.
  • Spontaneous: Information is transmitted automatically when a change occurs.

IEC 60870 Tools

Various auxiliary tools can be used to test, monitor, develop, and troubleshoot IEC 60870 communication.

In the future, this section will include free software, test tools, simulators, analysis tools, and developer utilities related to IEC 60870-5-101 and IEC 60870-5-104.

🔧 IEC 60870 Testing and Development Tools

This section is reserved for IEC 60870 tools that will be added in the future.

  • IEC 60870-5-104 Client / Server tools
  • IEC 60870-5-101 testing tools
  • IEC 104 simulators
  • ASDU and IOA analysis tools
  • IEC 60870 communication testing tools
  • Developer utilities

Summary

IEC 60870 is an important family of telecontrol standards designed primarily for monitoring and controlling remote devices in power systems from central control systems.

IEC 60870-5-101 uses serial communication infrastructures, while IEC 60870-5-104 uses TCP/IP-based network infrastructures. Both approaches are designed to transmit status, measurement, alarm, event, and control information using standardized structures.

To understand IEC 60870, it is particularly important to understand the concepts of ASDU, Type Identification, Common Address, IOA, Cause of Transmission, and timestamps.