IEC TR 61850-1:2003

TECHNICAL IEC
REPORT
TR 61850-1
First edition
2003-04
Communication networks and systems
in substations –
Part 1:
Introduction and overview
Réseaux et systèmes de communication dans les postes –
Partie 1:
Introduction et vue d’ensemble
Reference number
IEC/TR 61850-1:2003(E)
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TECHNICAL IEC
REPORT
TR 61850-1
First edition
2003-04
Communication networks and systems
in substations –
Part 1:
Introduction and overview
Réseaux et systèmes de communication dans les postes –
Partie 1:
Introduction et vue d’ensemble
 IEC 2003  Copyright - all rights reserved
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– 2 – TR 61850-1  IEC:2003(E)
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Reference documents . 6
3 Terms, definitions and abbreviations. 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 9
4 Objectives. 9
5 History.11
6 Approach to the elaboration of an applicable standard.12
6.1 General .12
6.2 Functions and logical nodes .12
6.3 Substation topologies .16
6.4 Dynamic scenarios .17
6.5 Requirements for a physical communication system .17
7 How to cope with fast innovation of communication technology.18
7.1 Independence of communication from application .18
7.2 Data modelling and services .19
8 General system aspects.20
8.1 Motivation.20
8.2 Engineering-tools and parameters .20
8.3 Substation automation system configuration language.21
8.4 Quality and life-cycle management .22
8.5 General requirements .22
9 Conformance testing.23
10 Structure and contents of the standard series .23
Annex A (informative) Types of substations and communication bus structures.26
Annex B (informative) Documents which have been considered in the IEC 61850
series .36
Figure 1 – Logical interfaces of an SAS.11
Figure 2 – Interface model of a substation automation system .13
Figure 3 – Relationship between functions, logical nodes, and physical nodes
(examples) .14
Figure 4 – Types of MV and HV substations.16
Figure 5 – Mapping of logical interfaces to physical interfaces; mapping of logical
interface 8 to the station bus .17
Figure 6 – Mapping of logical interfaces to physical interfaces; mapping of logical
interface 8 to the process bus .18
Figure 7 – Basic reference model.19
Figure 8 – The modelling approach of the IEC 61850 series.20
Figure 9 – Exchange of system parameters.21
Figure 10 – Periods for delivery obligations (example) .22
Figure A.1 – Examples of typical single line diagram for type D1.27

TR 61850-1  IEC:2003(E) – 3 –
Figure A.2 – Examples of typical single line diagrams for type D2 .27
Figure A.3 – Example of typical single line diagram for type D3.28
Figure A.4 – Examples of typical single line diagrams for type T1 .28
Figure A.5 – Example of typical single line diagram for type T2.29
Figure A.6 – Possible locations of current and voltage transformers in substation D2-2.32
Figure A.7 – Assignment of bay units (example).32
Figure A.8 – Typical protection zones .33
Figure A.9 – Alternative solutions for the process level communication bus.34
Table 1 – Types of messages.15
Table 2 – Calculated information flow at logical interfaces (example) .17
Table A.1 – Types of substations and interfaces used .30
Table A.2 – Types of substations and functions used .31

– 4 – TR 61850-1  IEC:2003(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
COMMUNICATION NETWORKS AND SYSTEMS
IN SUBSTATIONS –
Part 1: Introduction and overview
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this technical report may be the subject of
patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However,
a technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard,
for example “state of the art”.
IEC 61850-1, which is a technical report, has been prepared by IEC technical committee 57:
Power system control and associated communications
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
57/524/CDV 57/561/RVC
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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

TR 61850-1  IEC:2003(E) – 5 –
IEC 61850 consists of the following parts, under the general title Communication networks
and systems in substations .
Part 1: Introduction and overview
Part 2: Glossary
Part 3: General requirements
Part 4: System and project management
Part 5: Communication requirements for functions and device models
Part 6: Configuration description language for communication in electrical substations
related to IEDs
Part 7-1: Basic communication structure for substation and feeder equipment – Principles
and models
Part 7-2: Basic communication structure for substation and feeder equipment – Abstract
communication service interface (ACSI)
Part 7-3: Basic communication structure for substation and feeder equipment – Common
data classes
Part 7-4: Basic communication structure for substation and feeder equipment – Compatible
logical node classes and data classes
Part 8-1: Specific communication service mapping (SCSM) – Mappings to MMS (ISO/IEC
9506-1 and ISO/IEC 9506-2) and to ISO/IEC 8802-3
Part 9-1: Specific communication service mapping (SCSM) – Sampled values over serial
unidirectional multidrop point to point link
Part 9-2: Specific communication service mapping (SCSM) – Sampled values over
ISO/IEC 8802-3
Part 10: Conformance testing
This part is an introduction and overview of the IEC 61850 standard series. It describes the
philosophy, the work approach, the contents of the other parts, and documents of other
bodies which have been reviewed.
The committee has decided that the contents of this publication will remain unchanged until
2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
___________
For more details, see Clause 10.
Under consideration.
To be published.
– 6 – TR 61850-1  IEC:2003(E)
COMMUNICATION NETWORKS AND SYSTEMS
IN SUBSTATIONS –
Part 1: Introduction and overview
1 Scope
This technical report is applicable to substation automation systems (SAS). It defines the
communication between intelligent electronic devices (IEDs) in the substation and the related
system requirements.
This part gives an introduction and overview of the IEC 61850 standard series. It refers to and
includes text and Figures from other parts of the IEC 61850 standard series.
2 Reference documents
IEC 60870-5-103:1997, Telecontrol equipment and systems – Part 5-103: Transmission
protocols – Companion standard for the informative interface of protection equipment
IEC 61850-3: Communication networks and systems in substations – Part 3: General
requirements
IEC 61850-5: Communication networks and systems in substations – Part 5: Communication
requirements for functions and device models
IEC 61850-7-1: Communication networks and systems in substations – Part 7-1: Basic
communication structure for substation and feeder equipment – Principles and models
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)
IEC 61850-7-3: Communication networks and systems in substations – Part 7-3: Basic
communication structure for substation and feeder equipment – Common data classes
IEC 61850-7-4: Communication networks and systems in substations – Part 7-4: Basic
communication structure for substation and feeder equipment – Compatible logical node
classes and data classes
ISO 9001, 2001: Quality management systems – Requirements
IEEE C37.2,1996 IEEE Standard Electrical Power System Device Function Numbers and
Contact Designations
IEEE 100,1996, IEEE Standard Dictionary of Electrical and Electronic Terms
IEEE-SA TR 1550,1999: Utility Communications Architecture (UCA) Version 2.0 – Part 4: UCA
Generic Object Models for Substation and Feeder Equipment (GOMSFE)

TR 61850-1 © IEC:2003(E) – 7 –
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this Technical Report, the following terms and definitions apply:
3.1.1
Abstract Communication Service Interface
ACSI
virtual interface to an IED providing abstract communication services, for example connection,
variable access, unsolicited data transfer, device control and file transfer services,
independent of the actual communication stack and profiles used
3.1.2
bay
a substation consists of closely connected subparts with some common functionality.
Examples are the switchgear between an incoming or outgoing line and the busbar, the bus
coupler with its circuit breaker and related isolators and earthing switches, the transformer
with its related switchgear between the two busbars representing the two voltage levels. The
bay concept may be applied to one and a half breaker and ring bus substation arrangements
by grouping the primary circuit breakers and associated equipment into a virtual bay. These
bays comprise a power system subset to be protected such as a transformer or a line end,
and the control of its switchgear has some common restrictions such as mutual interlocking or
well-defined operation sequences. The identification of such subparts is important for
maintenance purposes (which parts may be switched off at the same time with a minimum
impact on the rest of the substation) or for extension plans (what has to be added if a new line
is to be linked in). These subparts are called bays and may be managed by devices with the
generic name “bay controller” and have protection systems called “bay protection”.
The concept of a bay is not commonly used all over the world. The bay level represents an
additional control level below the overall station level.
3.1.3
data object
part of a logical node object representing specific information, for example, status or
measurement. From an object-oriented point of view, a data object is an instance of
a data object class. Data objects are normally used as transaction objects; i.e., they are
data structures.
3.1.4
device
mechanism or piece of equipment designed to serve a purpose or perform a function, for
example, breaker, relay, or substation computer
[IEEE 100,1996]
3.1.5
functions
tasks, which are performed by the substation automation system, i.e. by application functions.
Generally, functions exchange data with other functions. The details are dependent on the
functions in consideration. Functions are performed by IEDs (physical devices). Functions
may be split in parts residing in different IEDs but communicating with each other (distributed
function) and with parts of other functions. These communicating function parts are called
logical nodes.
In the context of this standard, the decomposition of functions or their granularity is ruled by
the communication behaviour only. Therefore, all functions considered consist of logical
nodes that exchange data.
– 8 – TR 61850-1  IEC:2003(E)
3.1.6
Intelligent Electronic Device
IED
any device incorporating one or more processors with the capability of receiving or sending
data/control from or to an external source (for example, electronic multifunction meters, digital
relays, controllers)
3.1.7
interchangeability
ability to replace a device supplied by one manufacturer with a device supplied by another
manufacturer, without making changes to the other elements in the system
3.1.8
interoperability
ability of two or more IEDs from the same vendor, or from different vendors, to exchange
information and use that information for correct execution of specified functions
3.1.9
Logical Node
LN
smallest part of a function that exchanges data. A LN is an object defined by its data and
methods.
3.1.10
open protocol
protocol whose stack is either standardised or publicly available
3.1.11
Physical Device
PD
equivalent to an IED as used in the context of this standard
3.1.12
PICOM
description of an information transfer on a given logical connection with given communication
attributes between two logical nodes (Piece of Information for COMmunication). It also
contains the information to be transmitted and, in addition, requirement attributes such as
performance. It does not represent the actual structure and format for data that is exchanged
over the communication network. The PICOM approach was adopted from CIGRE working
group 34.03.
3.1.13
protocol
set of rules that determines the behaviour of functional units in achieving and performing
communication
3.1.14
self-description
a device contains information on its configuration. The representation of this information has
to be standardised and has to be accessible via communication (in the context of this
standard series).
3.1.15
system
within the scope of this standard, system always refers to substation automation systems
unless otherwise stated
TR 61850-1  IEC:2003(E) – 9 –
3.1.16
Specific Communication Service Mapping
SCSM
standardised procedure which provides the concrete mapping of ACSI services and objects
onto a particular protocol stack/communication profile.
To facilitate interoperability it is intended to have a minimum number of standardized
mappings (SCSM). Special application subdomains such as “station bus” and “process bus”
may result in more than one mapping. However, for a specific protocol stack selected only
one single SCSM and one single profile should be specified.
A SCSM should detail the instantiation of abstract services into protocol specific single
service or sequence of services which achieve the service as specified in ACSI. Additionally,
a SCSM should detail the mapping of ACSI objects into object supported by the application
protocol.
SCSMs are specified in the parts 8-x and 9-x of this standard series.
3.2 Abbreviated terms
ACSI Abstract Communication Service Interface
AIS Air Insulated Switchgear
CB Circuit Breaker
CDC Common Data Class
DO Data Object
EMC Electromagnetic Compatibility
GOMSFE Generic Object Models for Substation and Feeder Equipment
IED Intelligent Electronic Device
GIS Gas Insulated Switchgear
LN Logical Node
PD Physical Device
PICOM Piece of Information for COMmunication
SA Substation Automation
SAS Substation Automation System
SCSM Specific Communication Service Mapping
4 Objectives
The possibility to build SAS rests on the strong technological development of large-scale
integrated circuits, leading to the present availability of advanced, fast, and powerful
microprocessors. The result was an evolution of substation secondary equipment, from
electro-mechanical devices to digital devices. This in turn provided the possibility of
implementing SAS using several intelligent electronic devices (IEDs) to perform the required
functions (protection, local and remote monitoring and control, etc.). As a consequence, the
need arose for efficient communication among the IEDs, especially for a standard protocol.
Up to now, specific proprietary communication protocols developed by each manufacturer
have been used, requiring complicated and costly protocol converters when using IEDs from
different vendors.
The industry’s experiences have demonstrated the need and the opportunity for developing
standard communication protocols, which would support interoperability of IEDs from different
manufacturers. Interoperability in this case is the ability to operate on the same network or
communication path sharing information and commands. There is also a desire to have IED
interchangeability, i.e. the ability to replace a device supplied by one manufacturer with a
device supplied by another manufacturer, without making changes to the other elements in
the system. Interchangeability is beyond this communication standard. Interoperability is a

– 10 – TR 61850-1  IEC:2003(E)
common goal for electric utilities, equipment vendors and standardisation bodies. In fact, in
recent years several National and International institutions started activities to achieve this
goal (see Annex B).
The objective of SA standardisation is to develop a communication standard that will meet
functional and performance requirements, while supporting future technological develop-
ments. To be truly beneficial, a consensus must be found between IED manufacturers and
users on the way such devices can freely exchange information.
The communication standard must support the operation functions of the substation.
Therefore, the standard has to consider the operational requirements, but the purpose of the
standard is neither to standardise (nor limit in any way) the functions involved in substation
operation nor their allocation within the SAS. The application functions will be identified and
described in order to define their communication requirements (for example, amount of data to
be exchanged, exchange time constraints, etc.). The communication protocol standard, to the
maximum possible extent, should make use of existing standards and commonly accepted
communication principles.
The standard should ensure, among others, the following features:
• That the complete communication profile is based on existing IEC/IEEE/ISO/OSI
communication standards, if available.
• That the protocols used will be open and will support self descriptive devices. It should be
possible to add new a functionality.
• That the standard is based on data objects related to the needs of the electric power
industry.
• That the communication syntax and semantics are based on the use of common data
objects related to the power system.
• That the communication standard considers the implications of the substation being one
node in the power grid, i.e. of the SAS being one element in the overall power control
system.
TR 61850-1  IEC:2003(E) – 11 –
5 History
Starting in 1994, an ad-hoc working group “Substation Control and Protection Interfaces” of
IEC Technical Committee 57 elaborated proposals for a standardisation of communication in
substation automation systems. The following proposals have been presented to and
accepted by the National Committees:
• Elaboration of a standard on functional architecture, communication structure and general
requirements;
• Elaboration of a standard on communication within and between unit and substation
levels;
• Elaboration of a standard on communication within and between process and unit levels;
• Elaboration of a companion standard for the informative interface of protection equipment.
The companion standard for the informative interface of protection equipment has been
elaborated by the ad-hoc working group and has been published as IEC 60870-5-103.
The communication interfaces within the substation automation system may be represented
by the general structure shown in Figure 1.
Remote control (NCC) 7 Technical services
Station level functions Level 2
TC57
Level 1
Bay unit
• Control
• Protection
• Metering
Protection
• Disturbance recorder
• Disturbance recorder
3 2
• Misc. Functions
TC57 TC95 TC95
5 5
4 4
Instrumental Switchgear and Instrumental Switchgear and
Level 0
transformers transformer transformers transformer
TC38 TC14, TC17 TC38 TC14, TC17
IEC  1374/03
NOTE Logical interface 2 (teleprotection) and the interface to the remote control centre (NCC) are beyond the
scope of the IEC 61850 series.
Figure 1 – Logical interfaces of an SAS
The interfaces between the functional blocks do not represent physical interfaces of physical
devices – they are “logical interfaces”, i.e. they are independent from real communication
systems.
Figure 1 shows the IEC Technical Committees that are responsible for standards related to
devices; a close co-operation with these committees was considered to be mandatory. To
guarantee a close co-operation, all the mentioned committees have delegated specialists to
the working groups responsible for elaboration of the IEC 61850 series.

– 12 – TR 61850-1  IEC:2003(E)
6 Approach to the elaboration of an applicable standard
6.1 General
The approach is to blend the strengths of the following three methods: functional
decomposition, data flow, and information modelling.
Functional decomposition is used to understand the logical relationship between components
of a distributed function, and is presented in terms of logical nodes that describe the
functions, subfunctions and functional interfaces.
Data flow is used to understand the communication interfaces that must support the exchange
of information between distributed functional components and the functional performance
requirements.
Information modelling is used to define the abstract syntax and semantics of the information
exchanged, and is presented in terms of data object classes and types, attributes, abstract
object methods (services), and their relationships.
6.2 Functions and logical nodes
The objective of the standard is to specify requirements and to provide a framework to
achieve interoperability between the IEDs supplied from different suppliers.
The allocation of functions to devices (IEDs) and control levels is not fixed. The allocation
normally depends on availability requirements, performance requirements, cost constraints,
the state of the art of technology, utilities’ philosophies etc. Therefore, the standard should
support any allocation of functions.
In order to allow a free allocation of functions to IEDs, interoperability should be provided
between functions to be performed in a substation but residing in equipment (physical
devices) from different suppliers. The functions may be split in parts performed in different
IEDs but communicating with each other (distributed function). Therefore, the communication
behaviour of such parts called logical nodes (LN) has to support the requested interoperability
of the IEDs.
The functions (application functions) of an SAS are control and supervision, as well as
protection and monitoring of the primary equipment and of the grid. Other functions (system
functions) are related to the system itself, for example supervision of the communication.
Functions can be assigned to three levels: the station level, the bay level and the process
level.
Early on it was realised the logical interfaces shown in Figure 1 were not sufficient; logical
interfaces between functions at station level and between functions located in different bays
were missing. Therefore a new structure was designed, containing the additional logical
interfaces. The diagram shown in Figure 2 is the basis for the IEC 61850 series.

TR 61850-1  IEC:2003(E) – 13 –
Remote control (NCC) Technical services

FCT. A
FCT. B
STATION LEVEL
1,6 1,6
3 3
BAY/UNIT LEVEL
PROT.
PROT.
CONTR. CONTR.
Remote 2 Remote
protection protection
4,5 4,5
PROCESS LEVEL
Remote Process Interface Sensors Actuators
Remote Pr ocess Interface
HV equipment
IEC  1375/03
NOTE Interface numbers are for notational use in other parts of the IEC 61850 series and have no other
significance.
Figure 2 – Interface model of a substation automation system
The meanings of the interfaces are as follows:
IF1: protection-data exchange between bay and station level.
IF2: protection-data exchange between bay level and remote protection (beyond the
scope of this standard).
IF3: data exchange within bay level.
IF4: CT and VT instantaneous data exchange (especially samples) between process and
bay level.
IF5: control-data exchange between process and bay level.
IF6: control-data exchange between bay and station level.
IF7: data exchange between substation (level) and a remote engineer’s workplace.
IF8: direct data exchange between the bays especially for fast functions such as interlocking.
IF9: data exchange within station level.
IF10: control-data exchange between substation (devices) and a remote control centre
(beyond the scope of this standard).
The devices of a substation automation system may be physically installed on different
functional levels (station, bay, and process). This refers to the physical interpretation of
Figure 2.
NOTE The distribution of the functions in a communication environment may occur through the use of wide area
network, local area network, and process bus technologies. The functions are not constrained to be deployed
within/over any single communication technology.
Process level devices are typically remote I/Os, intelligent sensors and actuators (see
examples in Figure 2).
[---------Physical Devices-------]
– 14 – TR 61850-1  IEC:2003(E)
Bay level devices consist of control, protection or monitoring units per bay.
Station level devices consist of the station computer with a database, the operator’s
workplace, interfaces for remote communication, etc.
To reach the standardisation goals mentioned above, all known functions in a substation
automation system have been identified and split into subfunctions (logical nodes). Logical
nodes may reside in different devices and at different levels. Figure 3 shows examples to
explain the relationship between functions, logical nodes, and physical nodes (devices).
A function is called distributed when it is performed by two or more logical nodes that are
located in different physical devices. Since all functions communicate in some way, the
definition of a local or a distributed function is not unambiguous but depends on the definition
of the functional steps to be performed until the function is completed.
When a distributed function is implemented, proper reactions on the loss of a LN or an
included communication link have to be provided, for example the function may be blocked
completely or shows a graceful degradation if applicable.
NOTE The implementation is beyond the scope of the standard series.
[--------------------Functions----------------]
Synchronised
Logical
Distance
Overcurrent
CB switching
Nodes
protection
protection
HMI
X X X
Sy.Switch.
X
Dist.Prot.
X
X
O/C Prot.
Breaker 4
X X X
Bay CT
X X
Bay VT
X X 6
BB VT 7
X
IEC  1376/03
Figure 3 – Relationship between functions, logical nodes, and physical nodes
(examples)
Examples in Figure 3: Physical device 1: Station computer, 2: Synchronised switching device,
3: Distance protection unit with integrated overcurrent function, 4: Bay control unit, 5 and 6:
Current and voltage instrument transformers, 7: Busbar voltage instrument transformers.

TR 61850-1  IEC:2003(E) – 15 –
All known functions have been described in IEC 61850-5 by:
• task of the function;
• starting criteria for the function;
• result or impact of the function;
• performance of the function;
• function decomposition;
• interaction with other functions.
NOTE Standardising functions is not the intention of the IEC 61850 series.
All related logical nodes have been described in IEC 61850-5 by:
• grouping according to their most common application area;
• short textual description of the functionality;
• IEEE device function number if applicable (for protection and some protection related
logical nodes only, refer to IEEE C.37.2,1996);
• relationship between functions and logical nodes in tables and in the functional
description;
• exchanged PICOMs described in tables.
‘Dynamic’ requirements on transmission of explicit PICOMs including their attributes such as
the required data integrity have been elaborated by Working Group 03 of CIGRE Study
Committee 34; the result has been published in a report and has been used in the IEC 61850
series.
However, to simplify the approach, the PICOMs have been assigned to different message
types according to SAS requirements (see Table 1).
Table 1 – Types of messages
Type Name Examples
1a Fast messages – trip Trips
1b Fast messages – others Commands, simple messages
2 Medium speed messages Measurands
3 Low speed messages Parameters
Output data from transducers and instrument
4 Raw data messages
transformers
5 File transfer functions Large files
Time synchronisation;
6a Time synchronisation messages a
station bus
Time synchronisation;
6b Time synchronisation messages b
process bus
7 Command messages with access control Commands from station HMI

– 16 – TR 61850-1  IEC:2003(E)
6.3 Substation topologies
As stated earlier, functional requirements should be independent of substation sizes. Thus, it
is necessary to determine, for the complete range of performance requirements, the resulting
data flow (bus load) for different types and sizes of substations. Therefore, representative
types of worldwide substations have been analysed and the resulting data flow is documented
(see IEC 61850-5). Figure 4 shows typical MV and HV substations. All types of substations
that have been considered are described in Annex B.
20 kV
34,5 kV
13,8 kV
D1-1 D1-2
220 kV 110 kV
132 kV
T1-2
T1-1
IEC  1377/03
Figure 4 – Types of MV and HV substations
The identification of the types of substations, for example D1-2, is used as follows: Letter D is
used for distribution substations, letter T is used for transmission substations. The first
number represents the size of the substation (small, medium, large : the bigger the number,
the bigger the size), the second number identifies variants.

TR 61850-1  IEC:2003(E) – 17 –
6.4 Dynamic scenarios
The data-flow at logical interfaces has been calculated for normal and worst-case conditions
for typical substations. Table 2 gives an example for the substation type T1-1. The data flow
contains the information bits only and no protocol or message overhead.
Table 2 – Calculated information flow at logical interfaces (example)
Interface State of operation Maximum busload Remarks
number [Kilobytes/s]
Single network Normal 244
Single network Worst-case 442
1, 3, 6 " 123 Station bus
8 " 24 Station bus
4, 5 " 295 Process bus, all feeders
4, 5 " 65 Process bus, one feeder only
NOTE The worst-case scenario includes normal, emergency, abnormal and post-fault state of operations and is
assuming the strongest transmission time requirement per signal for all signals (see IEC 61850-5, Clause 12).
6.5 Requirements for a physical communication system
Logical interfaces may be mapped to physical interfaces in several different ways. A station
bus normally implements the logical interfaces 1, 3, 6, and 9; a process bus may cover the
logical interfaces 4 and 5. The logical interface 8 (‘inter-bay-communication’) may be mapped
to either or to both. This mapping will have a major impact on the resulting required
performance of the selected communication system (See Figures 5 and 6).
Mapping of all logical interfaces to one single bus is possible, if this satisfies the performance
requirements.
1,3,6,9
4,5 4,5
Logical interfaces Physical interfaces
IEC  1378/03
Figure 5 – Mapping of logical interfaces to physical interfaces;
mapping of logical interface 8 to the station bus

– 18 – TR 61850-1  IEC:2003(E)
1,3,6,9
4,5 4,5
Logical interfaces Physical interfaces
IEC  1379/03
Figure 6 – Mapping of logical interfaces to physical interfaces;
mapping of logical interface 8 to the process bus
7 How to cope with fast innovation of communication technology
7.1 Independence of communication from application
This standard specifies a set of abstract services and objects which may allow applications to
be written in a manner which is independent from a specific protocol. This abstraction allows
both vendors and utilities to maintain application functionality and to optimise this functionality
when appropriate. The application model specified in this standard consists of:
A vendor/user generated application written to invoke or respond to the appropriate set of
Abstract Communication Service Interface (ACSI) services.
This standard standardises the set of abstract services to be used between applications and
“application objects” allowing for compatible exchange of information among components of a
substation automation system. However, these abstract services/objects must be instantiated
through the use of concrete application protocols and communication profiles.
The concrete implementation of the device internal interface to the ACSI services is a local
issue and is beyond the scope of this standard.
The local ACSI is then mapped onto the appropriate set of concrete application
protocol/communication profile services as specified within a given Specific Communication
Service Mapping (SCSM). The state or changes of data objects are transmitted as concrete
data.
The IEC 61850 series provides an assortment of mappings which can be used for
communication within the substation; the selection of an appropriate mapping depends on the
functional and performance requirements.
NOTE Only application components that implement the same SCSM will be interoperable.

TR 61850-1  IEC:2003(E) – 19 –
Application
Abstract communication
ACSI
service interface
Specific communication
SCSM 1 SCSM 2 SCSM n
service mapping
Specific
interfaces
AL 1 AL 2 AL n
Application layer 7
Layers 1 . 6
Communication stacks
AL = Application layer
IEC  1380/03
Figure 7 – Basic reference model
This mapping is shown in Figure 7 as “SCSM“. According to the facilities of the related
application layer, the effort for the mapping can be different.
7.2 Data modelling and services
Logical nodes can only interoperate with each other if they are able to interpret and to
process the data received (syntax and semantics) and the communication services used.
Thus it is necessary to standardise data objects assigned to logical nodes and their
identification within the logical nodes.
Data and services of an application can be modelled in three levels (see Figure 8). The first
level describes abstract models and communication services used to exchange information
between logical nodes. Levels 2 and 3 define the application domain specific object model.
This includes a specification of data classes with attributes and their relation to logical nodes.
Level 1: Abstract Communication Service Interface (ACSI)
The ACSI specifies the models and services used for access to the elements of the domain
(substation automation) specific object model. Communication services provide mechanisms
not only for reading and writing of object values, but also for other operations, for example for
controlling primary equipment.
Level 2: Common Data Classes
The second level defines “Common Data Classes” (CDC). A common data class defines
structured information consisting of one or more attributes. The data type of an attribute may
be a foundation type (for example INTEGER) as defined in IEC 61850-7-1. More data types
are defined as common data attribute types in level 2. Data classes as defined in level 3 are
specialisations of CDCs according to their specific use in the application context.
Level 3: Compatible logical node classes and data classes
This level defines a compatible object model specifying logical node classes and data
classes. No additional specification is required as the identification and meaning (semantics)
of the logical node and data classes are defined. An example for a data class is ’switch
position with quality and time stamp’.

– 20 – TR 61850-1  IEC:2003(E)
Data classes of this level are similar to ‘objects’ defined in IEC 60870-5-103. Logical nodes of
this level are similar to ‘bricks’ defined in Utility Communications Architecture (UCA)
Version 2.0 (see reference in Annex B, point 12)).
Compatible
Objects with non- Objects based on
Objects standardized new data classes
semantics
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