Protocol IEC 61850

Protocol description
Communication line configuration
Communication line protocol parameters
Communication station configuration
Station protocol parameters
I/O tag configuration
I/O tag address
Literature
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Protocol description

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

Protocol  IEC 61850 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 IEC 61850 protocol in 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 fields elements of which are simple values
4. Writing to simple types of values (writing to arrays, array items and structures is not implemented yet)
5. Browsing - when a communication is established, 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 processing of GOOSE and GSSE reports.

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

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 host name 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 given address. If the atttempt is unsuccessful, then the process tries to establish a connection to 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 protocol. You can define the following parameters:

Table 1

Note 1

If all debug info are 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 to minimize the amount of debug information.

Communication station configuration

• Communication protocol "IEC 61850".
• Polling parameters are used for reading of I/O tags of "Periodically polled value" type.
• Protocol does not support time synchronization.
• in "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 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. Domain is the name of the logical device values of which we want to read. Multiple statiosn can be on one line. For each station a dedicated TCP connection to defined physical device will be created.

The Browse button enables to get 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 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 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 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 which identifying IEC 61850 object. Maximum size is 64 characters.
Note: if I/O tag's address is specified as %IGNORE, such an I/O tag will be ignored.

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 it spossible to specify an index of 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 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 addresss 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{	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 Structure object

  Example  2:  Communication line log shows an array consisting of two structures that contain structures that contain elements of 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{	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 Offset

For the Structure object type: it is possible to specify offset where IEC 61850 Quality is located. Offset defines a position relative to position of value given by a complex address. Offset 1 means that the IEC 61850 Quality is located directly after the value, offset -1 means that the quality is located directly before the value.
IEC 61850 Quality is of Bitstring type with 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, value in D2000 has a Weak attribute.
See the example in Time Offset. 

Time Offset

For the Structure object type: it is possible to specify offset where timestamp is located. Offset defines a position relative to position of value given by a complex address. Offset 1 means that the timestamp is located directly after the value, offset -1 means that the timestamp is located directly before the value.

If the Time Offset is not defined (or is equal to 0), 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 which contains a Bitstring value followed by qualit and timestamp. Therefore the object's address has Array Index = 0, Quality Offset = 1 and Time Offset = 2.

Integrity Period

This parameter is enabled for the I/O tags of "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 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 number of objects and speed of the device. These cached lists are sent to CNF process(es), so that consecutive filling of the Browse window is fast.

Filtering in the list of objects

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

Note

In addition to objects with supported data types (Boolean, Integer32 ...), the object list can contain objects with Structure type. These are the 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.

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

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Document revisions

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