IEC TR 61850-7-500:2017

Communication networks and systems for power utility automation - Part 7-500: Basic information and communication structure - Use of logical nodes for modeling application functions and related concepts and guidelines for substations

IEC TR 61850-7-500:2017(E) describes the use of the information model for devices and functions of IEC 61850 in applications in substation automation systems, but it may also be used as informative input for the modeling of any other application domain. In particular, it describes the use of compatible logical node names and data objects names for communication between Intelligent Electronic Devices (IED) for use cases. This includes the relationship between Logical Nodes and Data Objects for the given use cases. If needed for the understanding of the use cases, the application of services is also described informatively. If different options cannot be excluded they are also mentioned.

General Information

• Status: Published
• Publication Date: 25-Jul-2017
• ICS: 33.200 - Telecontrol. Telemetering
• Technical Committee: TC 57 - Power systems management and associated information exchange
• Current Stage: PPUB - Publication issued
• Start Date: 26-Jul-2017
• Completion Date: 25-Jul-2017

Overview

IEC TR 61850-7-500:2017 is a technical report published by the International Electrotechnical Commission (IEC) focusing on the communications networks and systems for power utility automation. Specifically, it addresses the use of the IEC 61850 information model for devices and functions in substation automation systems and provides valuable guidelines for modeling application functions using logical nodes. This report helps align device communication and interoperability within substations, ensuring better integration and management of Intelligent Electronic Devices (IEDs). While its primary focus is substation automation, its methodologies and insights can also inform other application domains within power utility systems.

Key Topics

• Logical Nodes: Describes the use and naming of compatible logical nodes, which represent standardized building blocks for utility automation functions.
• Data Objects: Details the use of standardized data object names to promote coherent communication between devices, supporting consistent interpretation and interoperability.
• Modeling Application Functions: Explores how logical nodes and data objects are used together to model a wide range of substation automation functions, from protection and control to monitoring and supervision.
• Communication Architectures: Addresses the information model's role in various substation communication system architectures-such as station bus, process bus, and their possible interconnections.
• Interoperability Guidelines: Emphasizes achieving interoperability by thoroughly defining data objects and services, and describes the relationship between logical nodes and data objects in different use cases.

Applications

The practical value of IEC TR 61850-7-500:2017 lies in its detailed guidance and examples for applying the IEC 61850 standard in substation automation:

• Substation Automation: Provides techniques for modeling and integrating functions such as control, protection, monitoring, supervision, local and distributed automation within substations.
• Device Interoperability: Aids utilities and equipment manufacturers in implementing IEDs that communicate efficiently using standardized logical node names and data object structures.
• System Configuration: Supports system integrators and engineering teams in designing and configuring substation systems using System/Substation Configuration description Language (SCL).
• Use Case Modeling: Illustrates use cases for common substation functions, enabling system designers to align their solutions with established best practices.
• Extending to Other Domains: Although focused on substations, the methodology can inform automation modeling in other power system domains like distributed energy resources, hydro power, and wind power automation.

Related Standards

This technical report must be viewed in the context of the broader IEC 61850 series, which provides the overarching framework for communication in power utility automation, including:

• IEC 61850-7-1: Principles and models for power utility automation.
• IEC 61850-7-2: Abstract communication service interface (ACSI) for data access and control.
• IEC 61850-7-3: Common data classes and attribute types for modeling.
• IEC 61850-7-4: Definition of logical node classes and data object classes.
• IEC 61850-8-1 & IEC 61850-9-2: Communication service mappings to protocols like MMS and sampled values over Ethernet.
• IEC TS 61850-2: Glossary of relevant terms in communication networks and systems for substations.
• IEC 61588, IEC/IEEE 61850-9-3: Protocols for time synchronization, which are critical for certain automation functions.
• IEC 60255-24/IEEE C37.111: Standards for transient data exchange crucial for protection and disturbance analysis.

Understanding and applying IEC TR 61850-7-500:2017 enables utilities and vendors to achieve high levels of system reliability, scalability, and interoperability in substation automation and beyond, making it a key reference for anyone involved in modern smart grid and utility communication network projects.

Standards Content (Sample)

IEC TR 61850-7-500 ®
Edition 1.0 2017-07
TECHNICAL
REPORT
colour
inside
Communication networks and systems for power utility automation –
Part 7-500: Basic information and communication structure – Use of logical
nodes for modeling application functions and related concepts and guidelines
for substations
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IEC TR 61850-7-500 ®
Edition 1.0 2017-07
TECHNICAL
REPORT
colour
inside
Communication networks and systems for power utility automation –

Part 7-500: Basic information and communication structure – Use of logical

nodes for modeling application functions and related concepts and guidelines

for substations
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.200 ISBN 978-2-8322-4508-8

– 2 – IEC TR 61850-7-500:2017 © IEC 2017
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Abbreviated terms . 11
4 Basics of substation automation with IEC 61850 . 12
4.1 Architecture . 12
4.2 Communication and relevance of bus definitions . 12
5 Summary of substation automation functions . 13
5.1 HMI and related station level functions . 13
5.2 Operational or control functions . 13
5.3 Monitoring and metering functions . 13
5.4 Local automation functions (protection and others) . 13
5.5 Distributed automation functions (protection and others) . 13
5.6 System support functions . 14
6 Basic interaction of control and protection functions modeled by logical nodes . 14
7 Function allocation and logical architecture . 17
7.1 Allocation of functions to IEDs . 17
7.2 Data Model as used in this Technical Report . 17
7.3 Logical architecture . 17
7.3.1 Station level. 17
7.3.2 Bay level . 17
7.3.3 Process level . 17
7.4 Interfaces . 17
7.4.1 Interface to CC and other remote operator places . 17
7.4.2 Interface to neighbouring substation . 18
7.4.3 Interface to the process (switchyard) . 18
7.4.4 Implementation remark . 18
8 Communication system architectures . 18
8.1 Modeling and communication architectures . 18
8.2 Specific modeling aspects of the process interface . 18
8.2.1 Merging unit and data sampling . 18
8.2.2 Breaker IED and switchgear control . 19
8.2.3 Time synchronization . 19
8.3 Use cases . 19
8.3.1 General remarks . 19
8.3.2 Station bus and process bus separated . 20
8.3.3 Station bus and process bus connected by proxy servers. 21
8.3.4 Station bus and process bus interconnected . 23
8.3.5 Common features for all three use case architectures . 23
9 Basic modeling principles . 26
9.1 Protection, measurement and control . 26
9.2 Supervision . 28
10 General modelling issues in substations . 29

10.1 Basic modelling of three-phase systems . 29
10.1.1 Acquisition of position indication . 29
10.1.2 Acquisition of currents and voltages and the trips . 30
10.2 Considering transmission times for GOOSE messages . 31
11 Control . 32
11.1 Bay control without process bus . 32
11.1.1 Basic diagram . 32
11.1.2 General modeling rules . 33
11.1.3 Modeling with process interface nodes and the role of GGIO and GAPC . 33
11.2 Bay control with process bus. 35
11.2.1 Basic diagram . 35
11.3 Control in the three-phase system . 36
11.3.1 Interconnection of logical nodes . 36
11.4 Interlocking, synchrocheck and blocking . 37
11.4.1 General remarks . 37
11.4.2 Interlocking . 39
11.4.3 Blocking . 40
11.4.4 Recommendation . 40
11.4.5 Synchrocheck . 41
11.5 Control authority . 41
11.5.1 Operation 1 out of n . 41
11.5.2 Control authority management . 42
11.5.3 Logical node representation . 45
11.6 Operation of switchgear with process bus . 47
11.6.1 The control service . 47
11.6.2 Extension of the control model by GOOSE messages in tabular form. 47
11.6.3 Extension of the control model by a sequence of GOOSE control
messages . 49
11.6.4 Alignment of the control model in CSWI and XCBR . 51
11.6.5 Behavior “Blocked” and “Testblocked” in case of process bus . 51
12 Protection . 52
12.1 Bay protection without process bus . 52
12.1.1 Basic diagram . 52
12.1.2 Modeling rules . 52
12.2 Bay protection with process bus . 53
12.2.1 Basic diagram . 53
12.2.2 Modeling protection of three-phase system . 54
12.3 Modelling of a protection function by multiple instances . 54
12.3.1 PDIF . 54
12.3.2 PDIS . 55
12.4 Modelling of different stages of a protection function by multiple instances . 55
12.4.1 Different trip levels and curves shown by PTOC as example . 55
12.4.2 PDSC – Phase discrepancy protection . 55
13 Redundant protection and control . 57
13.1 Redundant protection . 57
13.2 Redundant control. 58
13.3 Use of PTRC and testing. 59
14 Circuit breaker modelling by breaker related LNs (XCBR, SCBR and SOPM) . 60
15 Dedicated functions . 61

– 4 – IEC TR 61850-7-500:2017 © IEC 2017
15.1 Disturbance recording . 61
15.2 Point-on-wave switching . 63
15.3 Breaker failure protection . 66
15.4 Line differential protection . 68
15.5 Line distance protection . 69
15.6 Autorecloser (RREC) . 70
15.6.1 Introduction . 70
15.6.2 Autorecloser interconnection . 70
15.6.3 Autorecloser states and transitions . 72
15.7 Switch on to fault . 75
15.7.1 LN: Switch on to fault Name: PSOF . 75
15.8 Reverse blocking . 76
Annex A (normative) Switch-on-to-fault . 78
Annex B (normative) LN PSOF. 79
Annex C (normative) LN RREC: Autoreclosure. 82
Bibliography . 84

Figure 1 – Architecture of a substation automation system . 12
Figure 2 – Interaction of LNs for the application functions in SA focused on XCBR . 15
Figure 3 – Interaction of LNs for the application functions in SA focused on XSWI . 16
Figure 4 – Station bus and process bus separated . 20
Figure 5 – Station bus and process bus connected by proxy servers . 22
Figure 6 – Station bus and process bus interconnected . 22
Figure 7 – Basic LN models for (a) protection, (b) measurement and (c) control . 26
Figure 8 – Basic LN models for supervision of (a) insulation, (b) temperature and (c)
arc . 28
Figure 9 – Relation between the phase-related positions and the common position. 29
Figure 10 – Filtering of phase related position data to a common position . 30
Figure 11 – Acquisition of current and voltage and tripping in the three phase system . 31
Figure 12 – Modelling bay control without process bus (left: ok, right: wrong) . 32
Figure 13 – Bay control with non-defined process object “door” represented by
LN GGIO . 34
Figure 14 – Bay control (left: without process bus, right: with process bus) . 35
Figure 15 – Three-phase (left and middle) and single-phase control (right) with
process bus . 36
Figure 16 – Interlocking, synchrocheck and blocking check in control IED without PB . 38
Figure 17 – Interlocking, synchrocheck and blocking check with process bus PB . 39
Figure 18 – Relation between interlocking, synchrocheck, blocking and control
authority . 41
Figure 19 – Local remote authority switching at bay and process level . 45
Figure 20 – Station level authority switching . 46
Figure 21 – Switch control (SBO with enhanced security) with a sequence of GOOSE
control messages between BCU (“CSWI”) and CBC (“XCBR”) – Part 1 . 49
Figure 22 – Switch control (SBO with enhanced security) with a sequence of GOOSE
control messages between BCU (“CSWI”) and CBC (“XCBR”) – Part 2 . 50
Figure 23 – Bay protection without process bus (left: modeling = ok, right: modeling =
wrong) . 52

Figure 24 – Bay protection (left: without process bus, right: with process bus) . 53
Figure 25 – Three-phase trip (left) and single-phase trip (right) with process bus . 54
Figure 26 – Phase discrepancy protection . 56
Figure 27 – Single phase tripping and supervision by main 1 and main 2 protection . 57
Figure 28 – Single phase redundant control . 58
Figure 29 – Basic use of PTRC for protection tripping . 59
Figure 30 – PTRC used for grouping of closely related LNs . 59
Figure 31 – Two PTRCs for partial testing of the protection functions . 60
Figure 32 – Structure of the disturbance recorder (RDRE, RADR, RBDR) . 62
Figure 33 – Point-on-wave switching with all LNs needed in one IED (IED1) . 64
Figure 34 – Point-on-wave switching with Merging Unit (MU) in IED2 . 64
Figure 35 – Point-on-wave switching with process bus and time synchronization . 65
Figure 36 – Single and three-phase tripping and breaker failure protection . 66
Figure 37 – Single phase tripping and breaker failure protection in a double tripping
coil application . 67
Figure 38 – Three-end line differential protection with LN RMXU . 69
Figure 39 – Distance protection with communication (block, permit, direct trip) . 70
Figure 40 – Interaction of autorecloser (RREC) with other functions . 71
Figure 41 – Autoreclosure (RREC) states and transitions (dashed transitions are
examples for possible alternative transitions – see text) . 72
Figure 42 – Switch-on-to-fault protection function PSOF . 76
Figure 43 – Reverse blocking data flow with one infeed . 77

Table 1 – Short summary of logical nodes names . 15
Table 2 – Mapping of communication services to architectures 1a, 1b, 2a, 2b, 3 . 25
Table 3 – Logical nodes with control authority and related presence conditions . 43
Table 4 – Extension of the control model by GOOSE messages between CSWI and
XCBR . 48

– 6 – IEC TR 61850-7-500:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMMUNICATION NETWORKS AND SYSTEMS
FOR POWER UTILITY AUTOMATION –

Part 7-500: Basic information and communication structure –
Use of logical nodes for modeling application functions
and related concepts and guidelines for substations

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 61850-7-500, which is a technical report, has been prepared by IEC technical
committee 57: Power systems management and associated information exchange.

The text of this technical report is based on the following documents:
Enquiry draft Report on voting
57/1817/DTR 57/1865/RVDTR
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61850 series, published under the general title Communication
networks and systems for power utility automation, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
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– 8 – IEC TR 61850-7-500:2017 © IEC 2017
INTRODUCTION
This part of IEC 61850, which is a technical report, shows the use of Logical Nodes as
defined in IEC 61850-7-4 for application functions in the substation domain. IEC 61850
defines Communication Networks and Systems for Power Utility Automation, and more
specifically the communication architecture for subsystems like substation automation
systems. The sum of all subsystems may also result in the description of the communication
architecture for the overall power system management. The defined architecture provides in
IEC 61850-7-x both a power utility-specific data model and also a substation domain specific
data model with abstract definitions of data objects classes and services independently from
the specific protocol stacks, implementations, and operating systems. The mapping of these
abstract classes and services to communication stacks is outside the scope of IEC 61850-7-x
and may be found in IEC 61850-8-x and in IEC 61850-9-x.
IEC 61850-7-1 gives an overview of the basic communication architecture to be used for all
applications in the power utility domain. IEC 61850-7-3 defines common attribute types and
common data classes related to all applications in the power system domain. The attributes of
the common data classes may be accessed using services defined in IEC 61850-7-2. These
common data classes are used in this part to define the compatible data objects classes.
To reach interoperability, all data objects in the data model (IEC 61850- 7-4, IEC 61850-7-3)
need a strong definition with regard to syntax and semantics. The semantics of the data
objects ar e mainly provided by names assigned to common logical nodes and data objects
they contain as defined in IEC 61850-7-4, and dedicated logical nodes are defined in
domain-specific parts (IEC 61850-7-x) e.g. for hydro power control systems in IEC 61850-7-
410. Interoperability is reached with minimum effort if as many as possible of the data objects
are defined as mandatory. Because of different philosophies and technical features, some
data objects, especially settings, were declared as optional in this edition of the standard.
After some experience has been gained with this standard, this decision may be reviewed in
the next edition of the relevant parts of the standard.
A data object with full semantics is only one of the elements required to achieve
interoperability. Standardized access to the data objects is defined in compatible, power utility
and domain specific services (see IEC 61850-7-2). Since data objects and services are
hosted by devices (IED), a proper device model is also needed. To describe both the device
capabilities and the interaction of the devices in the related system, a configuration language
is also needed as defined in IEC 61850-6 by the System/Substation Configuration description
Language (SCL).
A lot of functions in power systems are complex combinations of local Logical Nodes in one
IED, or distributed Logical Nodes in many IEDs linked by a dedicated data exchange. For
some functions different solution concepts exist resulting in different implementations.
Depending on the kind of differences they may result in increased requirements for system
integration engineering tools or, in the worst case, destroy interoperability. The goal of this
informative document is to show the most common application of Logical Nodes in modelling
simple and complex application functions, to improve common understanding in modelling and
data exchange in general, and finally to stimulate implementations which support in any case
interoperability.
The data model of IEC 61850 i.e. the Logical Nodes (LN) contain only the data provided by
the application functions described but not the source where the data which are needed as
input for the application functions are from. This gap is also closed in this document either
expicitely by naming the input data or implicitely by showing the connections between the
different LNs used.
COMMUNICATION NETWORKS AND SYSTEMS
FOR POWER UTILITY AUTOMATION –

Part 7-500: Basic information and communication structure –
Use of logical nodes for modeling application functions
and related concepts and guidelines for substations

1 Scope
This part of IEC 61850, which is a technical report, describes the use of the information model
for devices and functions of IEC 61850 in applications in substation automation systems, but
it may also be used as informative input for the modeling of any other application domain. In
particular, it describes the use of compatible logical node names and data objects names for
communication between Intelligent Electronic Devices (IED) for use cases. This includes the
relationship between Logical Nodes and Data Objects for the given use cases. If needed for
the understanding of the use cases, the application of services is also described informatively.
If different options cannot be excluded they are also mentioned.
The modelling of the use cases given in this document are based on the class model
introduced in IEC 61850-7-1 and defined in IEC 61850-7-2. The logical node and data names
used in this document are defined in IEC 61850-7-4 and IEC 61850-7-3, the services applied
in IEC 61850-7-2. The naming conventions of IEC 61850-7-2 are also applied in this
document.
If extensions are needed in the use cases, the normative naming rules for multiple instances
and private, compatible extensions of Logical Node (LN) Classes and Data Object Names
defined in IEC 61850-7-1 are considered.
IEC 61850-7-5 describes in examples the use of logical nodes for modeling application
functions and related concepts and guidelines in general, independently from any application
domain respectively valid for all application domains in the electric power system (substation
automation, distributed energy resources, hydro power, wind power, etc.). This document
describes in examples the use of logical nodes for application functions in substation
automation including also line protection between substations. It also implies some tutorial
material where helpful. However it is recommended to read IEC 61850-5 and IEC 61850-7-1
in conjunction with IEC 61850-7-3 and IEC 61850-7-2 first.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60255-24/IEEE C37.111:2013, Measuring relays and protection equipment – Part 24:
Common format for transient data exchange (COMTRADE) for power systems
IEC 61588, Precision clock synchronization protocol for networked measurement and control
systems
IEC TS 61850-2, Communication networks and systems in substations – Part 2: Glossary

– 10 – IEC TR 61850-7-500:2017 © IEC 2017
IEC 61850-5:2013, Communication networks and systems for power utility automation –
Part 5: Communication requirements for functions and device models
IEC 61850-7-1, Communication networks and systems for power utility automation – Part 7-1:
Basic communication structure – Principles and models
IEC 61850-7-2:2010, Communication networks and systems for power utility automation –
Part 7-2: Basic information and communication structure – Abstract communication service
interface (ACSI)
IEC 61850-7-3, Communication networks and systems for power utility automation – Part 7-3:
Basic communication structure – Common data classes
IEC 61850-7-4:2010, Communication networks and systems for power utility automation –
Part 7-4: Basic communication structure – Compatible logical node classes and data object
classes
IEC 61850-8-1, Communication networks and systems for power utility automation – Part 8-1:
Specific communication service mapping (SCSM) – Mappings to MMS (ISO 9506-1 and ISO
9506-2) and to ISO/IEC 8802-3
IEC 61850-9-2, Communication networks and systems for power utility automation – Part 9-2:
Specific communication service mapping (SCSM) – Sampled values over ISO/IEC 8802-3
IEC/IEEE 61850-9-3, Communication networks and systems for power utility automation –
Part 9-3: Precision time protocol profile for power utility automation
IEC 61869-9, Instrument transformers – Part 9: Digital interface for instrument transformers
IEC 62271-3, High-voltage switchgear and controlgear – Part 3: Digital interfaces based on
IEC 61850
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61850-2 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
application functions
functions which perform a dedicated task in the utility automation system to allow the control,
protection, monitoring and supervision of the power system in a given domain such as
substation automation
3.1.2
domains
well-defined areas in the utility automation system respectively in the power system

3.1.3
use cases
samples for application functions or for a set of interacting ones to performing a dedicated
task
3.1.4
1-out-of-n control
state of the substation control when only one of the n switches in the substation is allowed to
be controlled (opened or closed) at the same time
3.2 Abbreviated terms
The abbreviated terms of IEC 61850-7-3 and IEC 61850-7-4 will be used. The following terms
are listed since they need to be highlighted or are missing in the referenced parts.
AIS Air insulated substation
ARC Autoreclosure
BIED Breaker IED means process near circuit breaker controller same as CBC
CC Control Center used as more generic term instead of NCC (Network Control
Center)
DCC Process near disconnector controller IED according to IEC 62271-3
instead of SIED (switch IED)
CBC Process near circuit breaker controller IED according to IEC 62271-3
instead of BIED (breaker IED)
ESC Process near earthing switch controller IED according to IEC 62271-3
instead of SIED (switch IED)
GIS Gas insulated substation
GOOSE Generic Object Oriented Substation Event according to IEC 61850-8-1
GPS Global Positioning System (US)
HMI Human Machine Interface
IED Intelligent Electronic Device
ITL Interlocking
LV Low Voltage
MMS Manufacturing Messaging Specification
MU a) Merging Unit used for process near IED sampling analogue measurement
of current and voltage, performing A/D conversion and merging data from
different measurement points in one or many SV streams as far as
applicable
b) Merging Unit used as LD name containing LNs for analogue data like
TVTR and TCTR
SBO Select before Operate
SCSM Specific Communication Service Mapping
SER Sequence of Event Recording
SIED Switch IED means process near disconnector/earthing switch controller same
as DCC and/or ESC
SV Sampled values data stream according to IEC 61850-9-2

– 12 – IEC TR 61850-7-500:2017 © IEC 2017
4 Basics of substation automation with IEC 61850
4.1 Architecture
Station Level HMI Gateway
Station Bus
Control &
Control Protection Control Protection
Bay Level
Protection
Process Bus Cu wires
Process Level Process Interface Process Interface Process Interface
Switchgear / Switchyard
IEC
Figure 1 – Architecture of a substation automation system
The architecture example given in Figure 1 describes the most common implementation of
substation automation systems with station level, bay level and process level. The boxes
(Intelligent Electronic Device: IED) are the containers for the functions. The communication
between the levels are named station and process bus. The naming refers to the physical
allocation of the communication systems between the levels only and not to a functionality
which is discussed below. Based on the common allocation of functions to station (including
HMI and Gateway), bay and process level IEDs the following definitions apply:
• The station bus is the communication network between station level devices (station
computer, gateway, etc.) and the bay level IEDs (protection, control, monitoring devices
etc).
• The process bus is the communication network between bay level IEDs (protection,
control, monitoring devices etc) and the process level interface for switchyard devices
(breakers, disconnectors, earthing switches, busbars, power transformers, current and
voltage transformers, etc.).
4.2 Communication and relevance of bus definitions
IEC 61850 defines the object model, the communication services to access and to exchange
the data, the engineering process and the mapping of the services onto a protocol.
All services are applicable for communication over both the above-defined station bus and
process bus. Based on the common allocation of functions also a common allocation of
services to the busses is assumed. Some allocations are very intuitive, i.e. the sampled value
(SV) service runs over the process bus since the samples of current and voltage come from
instrument transformers or sensors on the process level. However voltage samples
representing the busbar voltage for the synchrocheck may come over the station bus.
Since the function allocation and, therefore, the allocation of data of the object model is not
the same everywhere and not fixed regarding the evolution of substation automation over
time, the terms “station bus” and “process bus” do not have an implementation-independent
meaning. These terms do not exist in the title of any standard parts. They refer to the defined
services only, i.e.
• IEC 61850-8-1: Specific communication service mapping (SCSM) – Mappings to MMS
(ISO 9506-1 and ISO 9506-2) and to ISO/IEC 8802-3 refers to the Client-Server
communication and the GOOSE messages and
• IEC 61805-9-2: Specific Communication Service Mapping (SCSM) – Sampled values over
ISO/IEC 8802-3 refers the transmission of sampled values.
Therefore, the terms “station bus” and “process bus” will be used only if they are of benefit for
the reader of this document.
5 Summary of substation automation functions
5.1 HMI and related station level functions
Accessing the system
• Access control & access security management
• Access authority and access logging
• Operator access to the system: control, parameter switching, data retrieval
• Display of data and information: single line, alarm list, measurands
• Storage of data in the station computer: historical data, disturbance files
• Log management: archiving, sorting, etc.
5.2 Operational or control functions
Operating and supervising the system
• Operational control: switching devices, tap changer, LV devices
• Indication handling: switchgear position, etc.
• Event (SER) and alarm handling: recording, logging, acknowledgement (for alarms only)
• Parameter setting and parameter set switching: protection, ARC on/off, ITL override, etc.
• Data retrieval: setting, parameters, disturbance records, etc.
5.3 Monitoring and metering functions
Process/status data from the primary and secondary process/system
• Metering: revenue metering, operative measuring, calculation of U, I, P, Q, f, ϕ
• Power equipment and system monitoring: switchgear and transformer load, power quality
• Disturbance recording: Fault recording and fault location
5.4 Local automation functions (protection and others)
Performing local decisions w
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