IEC 61850 protocol

Protocol description
Communication line configuration
Communication line protocol parameters
Communication station configuration
Station protocol parameters
I/O tag configuration
I/O tag address
Comments on ABB Substation management unit COM600
Tell commands
Literature
Changes and modifications
Document revisions

Protocol description

The IEC 61850 protocol is an IEC standard designed for communication with Intelligent Electronic Devices (IED) at electrical substations (breakers, protections, transformers, switches, etc).

The IEC 61850 protocol is - like IEC 60870-6 ICCP/TASE.2 - based on the Manufacturing Message Specification (MMS) and therefore the implementation in the D2000 KOM process uses a common MMS framework.

Implementation of the IEC 61850 protocol in the D2000 system supports this functionality:

1. Periodic reading of values (polling)
2. Reading of values from predefined Datasets made available in predefined Information Reports - both buffered and unbuffered
3. Reading of array elements of which are simple values
4. Writing to simple types of values (writing to structures is not implemented yet)
5. Writing to array elements of which are simple values
6. Browsing - when communication is established, the following items can be browsed:

• • logical devices within a physical device (in the station address configuration)
  • objects located within the logical device (in the I/O tag configuration)
  • reports located within the logical device (in the I/O tag configuration)

There is no support for the processing of GOOSE and GSSE reports.

The ISO over TCP/IP transmission layer is implemented according to the RFC 1006 specification.

The protocol was tested with software simulators and with ABB Substation management unit COM600.

Communication line configuration

• Communication line category: TCP/IP-TCP.
• TCP Parameters:
  • Host: string max. 80 characters – server name in INET format (a name or numerical address a.b.c.d) 
  • Port: TCP port number (0 to 65535), port 102 is used by default.
  • Line number: not used, set to 1

A valid hostname or IP address of the device must be entered according to the rules above.

The port number where the device is listening must also be entered. The ISO over TCP/IP standard uses port 102.

In the case of redundant systems, it is also possible to enter multiple comma-separated names/addresses. When the connection is broken, the communication process will again attempt to establish a connection to the device at the specified address. If the attempt is unsuccessful, then the process tries to establish a connection to the next address. This is repeated cyclically until the connection with one server is established.

Communication line protocol parameters

Communication lines - configuration dialog box - tab Protocol parameters.
These parameters influence some optional parameters of the protocol. You can define the following parameters:

Table 1

Note 1

If all debug info is enabled, it could cause an overload of communication workstation and decrease of data transfer rate from IED to D2000. After the communication is tuned and debugged, we recommend minimizing the amount of debugging information.

Communication station configuration

• Communication protocol "IEC 61850".
• Polling parameters are used for reading I/O tags of the "Periodically polled value" type.
• The protocol does not support time synchronization.
• in the Time parameters tab, monotonic UTC time (with offset 0) should be set, as IEC 61850 uses UTC-based timestamps (unless a specific implementation is non-compliant with this part of the standard).

Station address

Img. No. 1, Station address

The station corresponds to one logical device. In one physical device, one or more logical devices can be defined. The domain is the name of the logical device values of which we want to read. Multiple stations can be on one line. For each station, a dedicated TCP connection to a defined physical device will be created.

The Browse button enables getting a list of logical devices (if the KOM process is running and communication is established). For Browsing functionality, the device must implement support for getNameList request with parameter ObjectClass = DOMAIN.

Station protocol parameters

Communication station - configuration dialog box - tab Protocol parameters.
These parameters influence some optional parameters of the protocol. You can set the following station parameters:

Table 2

I/O tag configuration

Permitted I/O tag types: Ai, Ao, Ci, Co, Di, Dout, TiA, ToA, TiR, ToR, Qi, TxtI, TxtO

I/O tag address

Img. No. 2, I/O tag address (Data Value)

The configuration of the I/O tag address requires the following data:

I/O Tag Type 

Type of I/O tag:

• Buffered/unbuffered report value - the I/O tag represents the value obtained from a buffered or unbuffered report. Such values are sent by the device spontaneously after they are changed.
• Periodically polled value - the I/O tag represents the periodically read value (polling). The reading period is configured in the station parameters. 
  Note: Periodic reading may result in loss of values as a result of rapid changes, so it should only be used for slowly changing values or if the value can not be retrieved from the report.
• Buffered/unbuffered report - the I/O tag represents a buffered or unbuffered report. It is important that all reports that are used (i.e. which contain the requested data) are configured as I/O tags. Based on these I/O tags, a report is activated when a communication is established (write is performed to its attributes $TrgOps, $RptEna, $GI and if the parameter Integrity period is specified, also to the attribute $IntgPd).

If the I/O tag representing the report has a text value, the value will be set to the name of the Dataset (the $DatSet attribute) that the report publishes.
If the I/O tag representing the report has an integer or a real value, the value will be

• • 0 - when a communication has been established - after receiving the initiate-Response message and requesting the reading of the Dataset name ($DatSet attribute) that the report publishes
  • 1 - after reading the Dataset name (receiving the device response to the Dataset name read request)
  • 2 - after reading report parameters
  • 3 - after reading a list of objects that are contained in Dataset
  • 4 - after successful report activation
  • 5 and more - with the arrival of each additional Information Report, the value of the object that represents it will be increased
  • invalid - if any of the communication steps fails

This mechanism can be used to define "watchdogs" guarding, for example, a communication failure, connection failure, or non-working sending of Information Reports.

Name

A unique text string that identifies the IEC 61850 object or its attribute (a reference). The maximum size is 64 characters.
Note: if the I/O tag's address is specified as %IGNORE, such an I/O tag will be ignored.

According to the standard ISO/IEC IEC 61850-8-1 the reference is in form
<LNVariableName>$<FC>$<LNDataName>$<AttributeName> (napr. XCBR1$ST$Pos$stVal)
respectively - if subattributes are used - in form
<LNVariableName>$<FC>$<LNDataName>$<AttributeName>$<subDataAttributeName> (napr. XBCR1$ST$Pos$origin$orCat)
where:

• LNVariableName is a name of a Logical Node. The name can be arbitrary, e.g. LLN0, Obj1XCBR1, Obj2XSWI1
• FC is a Functional Constraint. Table of defined functional constraints can be seen below.
• LNDataName is the name of a DataObject. The name can be arbitrary, the standard contains recommended rules concerning naming conventions.
• AttributeName is the name of Attribute of a DataObject. A table of frequently used attributes can be seen below.
• subDataAttributeName is the name of the Attribute of a SubDataObject. A table of frequently used attributes can be seen below.

The standard defines the following naming conventions for individual components of a reference:

Defined Functional Constraints according to ISO/IEC IEC 61850-8-1:

Names of DataObject Attributes and SubDataObject Attributes are defined in ISO/IEC IEC 61850-7-3 and the following table contains only the most common ones:

Data Type

The list of permitted data types:

Note * - types marked with asterisk (*) are used in IEC 60870-6 ICCP/TASE.2 protocol (which uses a common MMS framework). For IEC 61850, we recommend not using these types.

Array Index

• For the Autodetect object type and for arrays of elementary types (Array of): it is possible to specify an index of an element within an array. The arrays in the IEC 61850 protocol are indexed from 0. Not specifying the index results in accessing the 0-th element.

Note:  For arrays of elementary types (Array of), the IEC61850 supports writing the received values to a target column of a structured variable. 
If the Destination tab in the configuration of the I/O tag has a Destination column set to a column of a structured variable, the corresponding array items will be written into it. This only works if the Array Index is not entered or is equal to 0.

• For the Structure object type: it is necessary to specify a complex address of element (of simple type) within a structure.
  The complex address is in form x.y.z.. e.g. 0.2. Individual indices indicate order within a structure or field, a dot indicates a descend deeper.
  Example 1: Communication line log shows a structure consisting of VisibleString elements. Individual elements will be accessed by complex addresses 0.0, 0.1 and 0.2

  Log line	Note	Simple element
  08:08:14.322 29-06-2018|D|MMS> [1] STRUCTURE{	The object of Structure type
  08:08:14.323 29-06-2018|D|MMS> [1]   Structure{	Level 0
  08:08:14.325 29-06-2018|D|MMS> [1]     VisibleString=INFO TECH	Level 0.0	yes
  08:08:14.327 29-06-2018|D|MMS> [1]     VisibleString=1.0	Level 0.1	yes
  08:08:14.329 29-06-2018|D|MMS> [1]     VisibleString=Current harmonics measurement	Level 0.2	yes
  08:08:14.332 29-06-2018|D|MMS> [1]   }	End of structure
  08:08:14.334 29-06-2018|D|MMS> [1] }	End of the Structure object

  Example  2:  Communication line log shows an array consisting of two structures that contain structures that contain elements of the Float32 type. Individual elements will be accessed by complex addresses 0.0.0 and 1.0.0

  Log line	Note	Simple element
  08:08:14.169 29-06-2018|D|MMS> [1] ARRAY{	The object of Array type
  08:08:14.172 29-06-2018|D|MMS> [1]   Structure{	Level 0
  08:08:14.173 29-06-2018|D|MMS> [1]     Structure{	Level 0.0
  08:08:14.175 29-06-2018|D|MMS> [1]       Float32= 0.00000E+00	Level 0.0.0	yes
  08:08:14.177 29-06-2018|D|MMS> [1]     }	End of structure
  08:08:14.179 29-06-2018|D|MMS> [1]   }	End of structure
  08:08:14.181 29-06-2018|D|MMS> [1]   Structure{	Level 1
  08:08:14.183 29-06-2018|D|MMS> [1]     Structure{	Level 1.0
  08:08:14.185 29-06-2018|D|MMS> [1]       Float32= 1.00000E+02	Level 1.0.0	yes
  08:08:14.186 29-06-2018|D|MMS> [1]     }	End of structure
  08:08:14.188 29-06-2018|D|MMS> [1]   }	End of structure
  08:08:14.188 29-06-2018|D|MMS> [1] }	End of Array

Quality Index

For the Structure object type: it is possible to specify the index where IEC 61850 Quality is located. The format of the Quality Index is the same as a complex address.
IEC 61850 Quality is of Bitstring type with a length of 2 bytes. 13 quality bits are defined as follows (the standard numbers the bits so that the highest bit is 0 and the lowest is 15):

If at least one of bits number 2-12 is set, the value in D2000 has a Weak attribute.
See the example in Time Index. 

Time Index

For the Structure object type: it is possible to specify the index where the timestamp is located. The format of the Time Index is the same as a complex address.

If the Time Index is not specified, the timestamp of the information report (for I/O Tag Type=Buffered/unbuffered report value) or the current time (for  I/O Tag Type=Periodically polled value) will be used.

Example: information report contains a structure that contains a Bitstring value followed by quality and timestamp. Therefore the object's address has Array Index = 0, Quality Index = 1 and Time Index = 2.

Integrity Period

This parameter is enabled for the I/O tags of the "Buffered/unbuffered Report" type and it specifies a period (in ms) after which a report containing the values of all objects in the given datasheet is generated. Therefore, if a loss of value has occurred in some way, this Integrity Report will periodically restore the integrity of the data. Value 0 turns off the generation of the Integrity Report. The non-zero value causes a write to the $IntgPd report attribute during the report activation. 
Note: Not all IEC 61850 servers support this parameter.

Browse

For the I/O tags, it is possible to find a list of objects and their data types, as long as the KOM process is running and communication is established. 
When a Browse button is clicked, the IEC61850 Browser window opens, and the KOM process begins to query the list of objects with the GetNameList-Request message and then their data types with the GetVariableAccessAttributes-Request message.

Img. no. 3, the IEC 61850 Item Browser window

Meaning of individual choices and buttons:

Auto

If this choice is active, the Data Type will be set to Autodetect, otherwise to value discovered during browsing, e.g. Boolean or Integer32.

Copy all to clipboard

Copies the displayed objects and their respective data types into the Windows Clipboard.

Refresh

By pressing the Refresh button it is possible to enforce re-querying of the list of objects from the device. By default, the KOM process reads the list of objects and their respective data types only during the first browse request and stores them in memory. This reading can take a longer time, depending on the number of objects and speed of the device. These cached lists are sent to the CNF process(es), so that consecutive filling of the Browse window is fast.

Filtering in the list of objects

The browse window enables filtering by the object name and data type. It is not necessary to enter the full text in the filter field. The notation "*FILTERED EXPRESSION*" is supported. The symbol * represents any text before and after the expression (e.g. *momen*).

Note 1

In addition to objects with supported data types (Boolean, Integer32 ...), the object list can contain objects with Structure type. These are structured objects that can not be directly read. The implementation only supports work with simple types and fields whose elements are simple types, therefore individual items of structured objects need to be communicated.

Note 2

In D2000 versions from 20th December 2018 and newer, the recycling of browser dialog has been implemented. If the dialog is closed by the Cancel button or after selecting an object, it is actually only hidden and it is available for browsing by another I/O tag within the same station so that the tree structure of the browsed objects is preserved. Clicking on the close icon at the top right corner will cause the dialog to be really closed.

Note 3

Writing to I/O tag with the Array data type (Array of *) is supported for text I/O tags (TxtO).  When writing, individual values must be separated by commas, e.g. "1, 2, 3, 7".

Comments on ABB Substation management unit COM600

During the testing of the ABB Substation Management Unit COM600 the following facts were found:

• The device contained several configurable logical names, so it required configuration of several stations on the line (addresses e.g. RF_TS3CTRL, RF_TS3DR, RF_TS3LD0).
• The device has implemented buffered reports. For each report, it supported several instances differing by number (e.g., LLN0$BR$rcbStatUrg01 .. LLN0$BR$rcbStatUrg05, LLN0$BR$rcbMeasReg01 .. LLN0$BR$rcbMeasReg05). For multiple clients, each one had to subscribe to a specific instance of the report in order to avoid conflict.
• Value of Report Trigger Options parameter had to be 64 (hexadecimal). That means, the device did not support bit 3 - data-update during activation of buffered reports.
• The value of the Additional Browse Items parameter had to be LLN0 so that multiple objects and information reports are found during browsing.
  
• The buffered reports supported the Integrity Period parameter.
• The individual items of the information reports were of different structure:
  Booleans with quality flags and a timestamp (Array Index = 0, Quality Index = 1, Time Index = 2):
  

  15:59:54.444 07-12-2018|D|MMS>  [1]     STRUCTURE{
  15:59:54.446 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  15:59:54.448 07-12-2018|D|MMS>  [1]       Bitstring=<00><03>
  15:59:54.450 07-12-2018|D|MMS>  [1]       seconds= 1544108937 fraction= 3898870784 (06-12-2018 16:08:57.908) quality 1 (Accuracy of fraction: 1 bits)
  15:59:54.452 07-12-2018|D|MMS>  [1]     }

  Integers with quality flags and a timestamp (Array Index = 0, Quality Index = 1, Time Index = 2):
  

  15:59:54.432 07-12-2018|D|MMS>  [1]     STRUCTURE{
  15:59:54.434 07-12-2018|D|MMS>  [1]       Integer8= 1
  15:59:54.436 07-12-2018|D|MMS>  [1]       Bitstring=<00><03>
  15:59:54.438 07-12-2018|D|MMS>  [1]       seconds= 1544108937 fraction= 3834446336 (06-12-2018 16:08:57.893) quality 1 (Accuracy of fraction: 1 bits)
  15:59:54.440 07-12-2018|D|MMS>  [1]     }

  Floats (inside a structure) with quality flags and a timestamp (Array Index = 0.0, Quality Index = 1, Time Index = 2):
  

  16:00:03.979 07-12-2018|D|MMS>  [1]     STRUCTURE{
  16:00:03.980 07-12-2018|D|MMS>  [1]       Structure{
  16:00:03.981 07-12-2018|D|MMS>  [1]        Float32= 3.11465E+01
  16:00:03.982 07-12-2018|D|MMS>  [1]       }
  16:00:03.982 07-12-2018|D|MMS>  [1]       Bitstring=<00><03>
  16:00:03.984 07-12-2018|D|MMS>  [1]       seconds= 1544184591 fraction= 1623978240 (07-12-2018 13:09:51.378) quality 0 (Accuracy of fraction: 0 bits)
  16:00:03.984 07-12-2018|D|MMS>  [1]     }

  More complicated structures - e.g. multiple Booleans with common quality flags and a timestamp:

  16:00:04.118 07-12-2018|D|MMS>  [1]     STRUCTURE{
  16:00:04.119 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.120 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.120 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.121 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.122 07-12-2018|D|MMS>  [1]       Bitstring=<00><03>
  16:00:04.123 07-12-2018|D|MMS>  [1]       seconds= 1544108877 fraction= 3564805632 (06-12-2018 16:07:57.830) quality 0 (Accuracy of fraction: 0 bits)
  16:00:04.124 07-12-2018|D|MMS>  [1]     }

  or multiple Booleans and Integers with common quality flags and a timestamp:

  16:00:04.107 07-12-2018|D|MMS>  [1]     STRUCTURE{
  16:00:04.108 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.109 07-12-2018|D|MMS>  [1]       Integer8= 0
  16:00:04.110 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.111 07-12-2018|D|MMS>  [1]       Integer8= 0
  16:00:04.112 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.112 07-12-2018|D|MMS>  [1]       Integer8= 0
  16:00:04.113 07-12-2018|D|MMS>  [1]       Boolean=FALSE
  16:00:04.114 07-12-2018|D|MMS>  [1]       Integer8= 0
  16:00:04.115 07-12-2018|D|MMS>  [1]       Bitstring=<00><03>
  16:00:04.116 07-12-2018|D|MMS>  [1]       seconds= 1544184591 fraction= 2075243776 (07-12-2018 13:09:51.483) quality 0 (Accuracy of fraction: 0 bits)
  16:00:04.117 07-12-2018|D|MMS>  [1]     }

  
  

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Literature

• RFC 1006 (ISO Transport Service on top of the TCP, Version: 3)
• International Standard ISO/IEC 8073 (Open Systems Interconnection — Protocol for providing the connection-mode transport service)
• International Standard ISO/IEC 8327-1 (Open Systems Interconnection — Connection-oriented Session protocol: Protocol Specification)
• International Standard ISO/IEC 8823-1 (Open Systems Interconnection — Connection-oriented Presentation protocol: Protocol Specification)
• International Standard ISO/IEC 8650-1 (Open Systems Interconnection — Connection-oriented protocol for the Association Control Service Element: Protocol Specification)
• International Standard ISO/IEC IEC 61850-1 (Communication networks and systems in substations – Part 1: Introduction and overview)
• International Standard ISO/IEC IEC 61850-2 (Communication networks and systems in substations – Part 2: Glossary)
• International Standard ISO/IEC IEC 61850-3 (Communication networks and systems in substations – Part 3: General requirements)
• International Standard ISO/IEC IEC 61850-4 (Communication networks and systems in substations – Part 4: System and project management)
• International Standard ISO/IEC IEC 61850-5 (Communication networks and systems in substations – Part 5: Communication requirements for functions and device models)
• International Standard ISO/IEC IEC 61850-6 (Communication networks and systems in substations – Part 6: Configuration description language for communication in electrical substations related to IEDs)
• International Standard ISO/IEC IEC 61850-7-1 (Communication networks and systems in substations – Part 7-1: Basic communication structure for substation and feeder equipment – Principles and models)
• International Standard ISO/IEC IEC 61850-7-2 (Communication networks and systems in substations – Part 7-2: Basic communication structure for substation and feeder equipment – Abstract communication service interface (ACSI))
• International Standard ISO/IEC IEC 61850-8-1 (Communication networks and systems in substations – Part 8-1: Specific Communication Service Mapping (SCSM) – Mappings to MMS (ISO 9506-1 and ISO 9506-2) and to ISO/IEC  8802-3)
• International Standard ISO/IEC IEC 61850-9-1 (Communication networks and systems in substations – Part 9-1: Specific Communication Service Mapping (SCSM) – Sampled values over serial unidirectional multidrop point to point link)
• International Standard ISO/IEC IEC 61850-9-2 (Communication networks and systems in substations – Part 9-2: Specific Communication Service Mapping (SCSM) – Sampled values over ISO/IEC 8802-3)

Changes and modifications

-

Document revisions

• Ver. 1.0 - June 20, 2018 - Creation of document.