IEC/TR 60870-1-4

SLOVENSKI STANDARD
SIST IEC/TR 60870-1-4:1997
01-avgust-1997
Telecontrol equipment and systems - Part 1: General considerations - Section 4:
Basic aspects of telecontrol data transmission and organizationof standards IEC
870-5 and IEC 870-6
Telecontrol equipment and systems - Part 1: General considerations - Section 4: Basic
aspects of telecontrol data transmission and organization of standards IEC 870-5 and
IEC 870-6
Matériels et systèmes de téléconduite - Partie 1: Considérations générales - Section 4:
Aspects fondamentaux de la transmission de données de téléconduite et organisation
des normes CEI 870-5 et CEI 870-6
Ta slovenski standard je istoveten z: IEC/TR 60870-1-4
ICS:
33.200 Daljinsko krmiljenje, daljinske Telecontrol. Telemetering
meritve (telemetrija)
SIST IEC/TR 60870-1-4:1997 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST IEC/TR 60870-1-4:1997

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SIST IEC/TR 60870-1-4:1997
RAPPORT CEI
TECHNIQUE -TYPE 3 IEC
870-1-4
TECHNICAL
Première
REPORT -TYPE 3
First edition
1994-07
Matériels et systèmes de téléconduite —
Partie 1:
Considérations générales —
Section 4: Aspects fondamentaux
de la transmission de données de téléconduite
et organisation des normes CEI 870-5 et CEI 870-6
Telecontrol equipment and systems —
Part 1:
—
General considerations
4: Basic aspects of telecontrol
Section
data transmission and organization
of standards IEC 870-5 and IEC 870-6
de reproduction réservés—Copyright — all rights reserved
© CEI 1994 Droits
No part of this publication may be reproduced or utilized in
Aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
in writing from the publisher.
les microfilms, sans l'accord écrit de l'éditeur.
Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé Genève,
Commission Electrotechnique Internationale
CODE PRIX
International Electrotechnical Commission
PRICE CODE
IEC MeeiyHapoaiaa 3neicrporexHHVecsaa Homuccia
• Pour prix, voir catalogue en vigueur
•
For price, see current catalogue

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SIST IEC/TR 60870-1-4:1997
870-1-4 © IEC:1994 – 3 –
CONTENTS
Page
FOREWORD 5
INTRODUCTION 9
Clause
1 11
Scope and object
11
2 Reference documents
19
3 Definition of technical terms
21
4 Basic communication structures and protocol models
29
5 Data communication principles ,
43 6 Introduction to IEC 870-5 and IEC 870-6

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SIST IEC/TR 60870-1-4:1997
870-1-4 © IEC:1994 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
EQUIPMENT AND SYSTEMS –
TELECONTROL
Part 1: General considerations –
Section 4: Basic aspects of telecontrol data transmission
and organization of standards IEC 870-5 and IEC 870-6
FOREWORD
The IEC (International Electrotechnical Commission) is a world-wide organization for standardization
1)
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation 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, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
reports or guides and they are accepted by the National Committees in that sense.
In order to promote international unification, IEC National Committees undertake to apply IEC International
4)
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.
The main task of IEC technical committees is to prepare International Standards in
exceptional circumstances, a technical committee may propose the publication of a
technical report of one of the following types:
type 1, when the required support cannot be obtained for the publication of an
•
International Standard, despite repeated efforts;
type 2, when the subject is still under technical development or where for any other
•
reason there is the future but not immediate possibility of an agreement on an
International Standard;
type 3, when a technical committee has collected data of a different kind from that
•
which is normally published as an International Standard, for example "state of the art".
Technical reports of types 1 and 2 are subject to review within three years of publication to
decide whether they can be transfomed into International Standards. Technical reports of
type 3 do not necessarily have to be reviewed until the data they provide are considered to
be no longer valid or useful.

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SIST IEC/TR 60870-1-4:1997
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870-1-4 © IEC:1994
IEC 870-1-4, which is a technical report of type 3, 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:
Committee draft Report on voting
57(SEC)162
57(SEC)128
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.

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870-1-4 © I EC:1994
INTRODUCTION
In the area of process control, especially in the area of telecontrol and SCADA systems,
there is an increasing demand for real-time data transmission. Inherent in this type of
application are requirements with respect to data integrity and guaranteed transmission
time.
The applicability of a particular type of communication network with its associated
protocols depends upon its ability to fulfil these requirements. This is a function of a
number of factors, including:
– bandwidth;
– traffic load (normal and avalanche conditions);
– transmission quality;
– coding and encryption schemes;
– computing power of communication front-ends and nodes.
Each candidate system should be evaluated in the light of all of these factors.
In particular, approaches to telecontrol data communication based on the OSI (open-
system interconnection) family of protocols (which were conceived originally for application
to inter-computer communication and not for telecontrol) should be examined very carefully
from this point of view.
IEC 1085 deals with the totality of telecommunications as applied to the administration and
operation of electric power systems. It does not go into detail on the specific needs of
telecontrol.
IEC 870-1-1 describes the general principles of the layout and the functions of telecontrol
systems. Clause 6 of that publication gives already some overviews on the transmission of
telecontrol data, but both the complexity of the data transmission systems, as well as their
numerous applications need a closer look. Due to this fact, a large number of different
publications dealing with standardization of telecontrol protocols will be published.
Therefore, it is necessary to give an overview in this report relating to the basic aspects of
telecontrol data transmission.

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TELECONTROL EQUIPMENT AND SYSTEMS –
Part 1: General considerations –
Section 4: Basic aspects of telecontrol data transmission
and organization of standards IEC 870-5 and IEC 870-6
1 Scope and object
This technical report applies to telecontrol equipment and systems with coded bit serial
data transmission for monitoring and control of geographically widespread processes.
This report is intended as a brief tutorial on transmission techniques, equipment and
protocols in view of their use in telecontrol systems. It is thus intended as a guide to orient
those using the standards defined in the series of IEC 870-5 and IEC 870-6. More
precisely, it gives a frame of reference for evaluating solutions as well as defining and
describing the key technical terms. Terms that are defined in IEC 50(371) and in
IEC 870-1-3 are complemented by further definitions in clause 3 of this repo rt .
It further provides:
– descriptions of applicable basic communication technologies;
– basic rules as to how different system layers (see clause 3) can be used together
(i.e. which combinations of standards in different layers are technically coherent and
which are not).
It is not intended to recommend or impose solutions, this being the role of IEC 870-5 and
IEC 870-6.
2 Reference documents
IEC 50(371): 1984, International Electrotechnical Vocabulary (IEV) – Chapter 371:
Telecontrol
International Electrotechnical Vocabulary (IEV) – Chapter 721:
IEC 50(721): 1991,
Telegraphy, facsimile and data communication
IEC 870-1-1: 1988, Telecontrol equipment and systems – Part 1: General considerations –
Section One: General principles
Telecontrol equipment and systems – Part 1: General considerations –
IEC 870-1-2: 1989,
Section Two: Guide for specifications
IEC 870-1-3: 1990, Telecontrol equipment and systems – Part 1: General considerations –
Section Three: Glossary
IEC 870-5-1: 1990, Telecontroi equipment and systems – Part 5: Transmission protocols –
Section One: Transmission frame formats

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IEC 870-5-2: 1992, Telecontrol equipment and systems – Part 5: Transmission protocols –
Section 2: Link transmission procedures
Telecontro! equipment and systems – Part 5: Transmission protocols –
IEC 870-5-3: 1992,
Section 3: General structure of application data
rt 5: Transmission protocols –
IEC 870-5-4: 1993, Telecontrol equipment and systems – Pa
Section 4: Definition and coding of application information elements
IEC 870-5-5: 199x, Telecontrol equipment and systems – Part 5: Transmission protocols –
Section 5: Basic application functions (under consideration)
5: Transmission protocols –
IEC 870-5-x: 199x, Telecontrol equipment and systems – Part
Section x: Telecontrol companion standards and profiles (under consideration)
IEC 870-6-1: 199x, Telecontrol equipment and systems – Part 6: Telecontrol protocols
compatible with ISO and CCITT standards – Section 1: Application context and
organization of standards (under consideration)
IEC 870-6-2: 199x, Telecontrol equipment and systems – Part 6: Telecontrol protocols
compatible with ISO and CCITT standards – Section 2: Use of base standards (OSI
layers 1-4) (under consideration)
Telecontrol equipment and systems – Part 6: Telecontrol protocols
IEC 870-6-3: 199x,
compatible with ISO and CCITT standards – Section 3: Use of base standards (OSI layers
5-7)
(under consideration)
IEC 870-6-4: 199x, Telecontrol equipment and systems – Part 6: Telecontrol protocols
(under
compatible with ISO and CCITT standards – Section 4: Network management
consideration)
IEC 870-6-x: 199x, Telecontrol equipment and systems – Part 6: Telecontrol protocols
(under
compatible with ISO and CCITT standards – Section x: Functional profiles
consideration)
ISO 2382: Information technology – Vocabulary
ISO 7498: 1984, Information processing systems – Open Systems Interconnection – Basic
reference model
ISO 8072: 1986, Information processing systems – Open Systems Interconnection –
Transport service definition
ISO/IEC 8073: 1992, Information technology – Telecommunications and information
exchange betweeen systems – Open Systems Interconnection – Protocol for providing the
connection-mode transport service
Information processing systems – Open Systems Interconnection – Basic
ISO 8326: 1987,
connection oriented session service definition

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ISO 8327: 1987, Information processing systems – Open Systems Interconnection – Basic
connection oriented session protocol specification
ISO 8509: 1987, Information processing systems – Open Systems Interconnection –
Service conventions
Information processing systems – Open Systems Interconnection –
ISO 8822: 1988,
Connection oriented presentation service definition
ISO 8823: 1988, Information processing systems – Open Systems Interconnection –
Connection oriented presentation protocol specification
Standardization of FMVFT
CCITT Recommendation R 35: 1989, Blue Book, Fascicle VII.1,
systems for a modulation rate of 50 bauds
CCITT Recommendation R 36: 1989, Blue Book, Fascicle VII.1, Coexistence of 50-
baud/120-Hz channels, 100-baud/240-Hz channels, 200-baud/360-Hz or 480-Hz channels
on the same voice-frequency telegraph system
Standardization of FMVFT
CCITT Recommendation R 37: 1989, Blue Book, Fascicle VII.1,
bauds
systems for a modulation rate of 100
A: 1989, Blue Book, Fascicle VII.1, Standardization of
CCITT Recommendation R 38
bauds with channels spaced at 480 Hz
FMVFT systems for a modulation rate of 200
Electrical characteristics
CCITT Recommendation V 11: 1989, Blue Book, Fascicle VIII.1,
for balanced double-current interchange circuits for general use with integrated circuit
equipment in the field of data communications
300 bits per second
CCITT Recommendation V 21: 1989, Blue Book, Fascicle VIII.1,
duplex modem standardized for use in the general switched telephone network
CCITT Recommendation V 22: 1989, Blue Book, Fascicle VIII.1, 1 200 bits per second
duplex modem standardized for use in the general switched telephone network and on
point-to-point 2-wire leased telephone-type circuits
600/1 200-baud modem
CCITT Recommendation V 23: 1989, Blue Book, Fascicle VIII.1,
standardized for use in the general switched telephone network
List of definitions for
CCITT Recommendation V 24: 1989, Blue Book, Fascicle V111.1,
interchange circuits between data terminal equipment (DTE) and data circuit-terminating
equipment (DCE)
2 400 bits per second
CCITT Recommendation V 26: 1989, Blue Book, Fascicle VIII.1,
modem standardized for use on 4-wire leased telephone-type circuits

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CCITT Recommendation V 27: 1989, Blue Book, Fascicle VIII.1, 4 800 bits per second
modem with manual equalizer standardized for use on leased telephone-type circuits
CCITT Recommendation V 28: 1989, Blue Book, Fascicle VIII.1, Electrical characteristics
for unbalanced double-current interchange circuits
CCITT Recommendation V 29: 1989, Blue Book, Fascicle VIII.1, 9 600 bits per second
modem standardized for use on point-to-point 4-wire leased telephone-type circuits
CCITT Recommendation V 32: 1989, Blue Book, Fascicle VIII.1, A family of 2-wire, duplex
modems operating at data signalling rates of up to 9 600 bits/s for use on the general
switched telephone network and on leased telephone-type circuits
CCITT Recommendation X 3: 1989, Blue Book, Fascicle VIII.2, Packet assembly/
disassembly facility (PAD) in a public data network
CCITT Recommendation X 20: 1989, Blue Book, Fascicle VIII.2, Interface between data
terminal equipment (DTE) and data circuit-terminating equipment (DCE) for start-stop
transmission services on public data networks
CCITT Recommendation X 21: 1989, Blue Book, Fascicle VIII.2, Interface between data
terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous
operation on public data networks
CCITT Recommendation X 21bis: 1989, Blue Book, Fascicle VIII.2, Use on public data
networks of data terminal equipment (DTE) which is designed for interfacing to
asynchronous duplex V-series modems
CCITT Recommendation X 22: 1989, Blue Book, Fascicle VllI.2, Multiplex DTE/DCE
interface for user classes 3-6
List of definitions for
CCITT Recommendation X 24: 1989, Blue Book, Fascicle VIII.2,
interchange circuits between data terminal equipment (DTE) and data circuit-terminating
equipment (DCE) on public data networks
CCITT Recommendation X 25: 1989, Blue Book, Fascicle VIII.2, Interface between data
terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals
operating in the packet mode and connected to public data networks by dedicated circuit
CCITT Recommendation X 28: 1989, Blue Book, Fascicle VIII.2, DTE/DCE interface for a
start-stop mode data terminal equipment accessing the packet assembly/disassembly
facility (PAD) in a public data network situated in the same country
CCITT Recommendation X 29: 1989, Blue Book, Fascicle VIII.2, Procedures for the
exchange of control information and user data between a packet assembly/disassembly
facility (PAD) and a packet mode DTE or another PAD

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3 Definition of technical terms
3.1 balanced transmission: Transmission method by which either data terminal
equipment (DTE) of two connected stations may initiate a message transmission at any
time.
3.2 call establishment: Sequence of events for the establishment of a data connection.
[CCITT X.15/1,4]
3.3 call release: Sequence of events for the release of a data connection.
3.4 circuit-switched network: Arrangement of dedicated (time-division or space-division)
switching facilities to provide telecommunication service based on circuit-switching
methods. These could be a circuit-switched data network or switched telephone network.
Process that, on demand, connects two or more data terminal
3.5 circuit switching:
equipments and permits the exclusive use of a data circuit between them until the
connection is released. [ISO 2382/09.05.09]
Group of binary digits formed by an n-byte augmented by a number of
3.6 envelope:
additional bits which are required for the operation of the data network. [IEV 721-19-25]
3.7 node: In a data network, point where one or more functional units interconnect
channels or data circuits. [ISO 2382/09.02.02]
3.8 packet: Sequence of binary digits, including data and control signals, that is
transmitted and switched as a composite whole.
NOTE — The data, control signals and possibly error control information are arranged in a specific format.
[ISO 2382/09.06.26]
3.9 packet assembler/disassembler (PAD): Functional unit that enables data terminal
equipments not equipped for packet switching to access a packet-switched network. [ISO
2382/09.07.20]
3.10 packet-switched network: Arrangement of dedicated switching facilities to provide
telecommunication service based on packet-switching methods.
3.11 packet switching: Process of routing and transferring data by means of addressed
packets so that a channel is occupied only during the transmission of a packet; upon
completion of the transmission, the channel is made available for the transfer of other
packets. [ISO 2382/09.05.08]
3.12 peer-to-peer protocol: Protocol between entities within the same layer of an open
system.
3.13 periodic data transmission: Transmission of sets of data that are repeated at equal
time intervals.

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3.14 service primitive: An abstract, implementation-independent representation of an
interaction between the service user and the se rvice provider. [ISO TR 8509]
Code that provides special symbols for frame synchronization.
3.15 structured code:
Delay time which occurs between the data input to the application
3.16 transit delay T,,:
layer of the sending station and the data output to the application process of the receiving
station. (The transit delay T„ is one component of the overall transfer time.)
Term specifying some quality description of a
3.17 transmission quality:
communication network, e.g. bit error rate, availability of a dedicated channel, probability
of bit error bursts, signal-to-noise ratio, amplitude and phase distortion, non-linearities,
inter-channel interference.
Code without restrictions on bit
transparent code/bit oriented code:
3.18
combinations.
Transmission method by which only the DTE of the
3.19 unbalanced transmission:
primary station may initiate message transfers. The secondary station transmits only after
request from the primary station.
The window size describes how many unterminated se rvices at a
3.20 window size:
rt layers).
time are handled by the protocol (notion used by the data link, network and transpo
4 Basic communication structures and protocol models
The basic classification of functions of a communication system follows that of the ISO
seven-layer OSI model. This model is for descriptive purposes and it is not required that a
given system be actually implemented in this way.
For a detailed description of this model and the functions of the different layers, the reader
is referred to the relevant ISO and CCITT documents (especially ISO 7498).
Description of the components of a transmission network
4.1
Figure 1 shows the general structure of a communication network. The different
components of the network have the following essential features.
Transmission network
The transmission network consists of transmission channels between stations and
nodes that may have packet-switching or circuit-switching facilities.
DCE (data circuit terminating equipment)
The DCE represents the network entrance point. The interface between the DCE that
usually belongs to the network and the DTE (data terminal equipment) is defined, for
example, by CCITT Recommendations V.11, V.24, V.28, X.21 etc.

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These standards offer different options on the interface between DTE and DCE. This
interface may carry, in addition to the data stream, various supervisory and control
signals of the data traffic, such as information on signal element timing (clock
frequency), information on the channel quality, calling indicators, selections of
transmission frequencies, etc.
The DCE can be a modem or a multiplexer and is standardized in the CCITT:
– R series: low-speed telegraph modems and multiplexers e.g. R.35, R.36, R.37,
R.38A;
V series: asynchronous and synchronous modems e.g. V.22, V.26, V.27, V.29,
–
V.32;
– X series: interfaces to digital networks e.g. X.20, X.21.
DTE (data terminal equipment)
In telecontrol applications, this equipment is the telecontrol equipment which can be, for
example, an outstation (RTU), telecontrol equipment in a DCC (district control centre),
RCC (regional control centre) or MCC (main control centre).
4.2 OSI seven-layer model
In the OSI model, the functions of the DTE are divided into seven layers as shown in
figure 2 (this figure shows the standards applicable to each layer but does not give
functional profiles).
The different layers are introduced below. The descriptions present each layer very
succinctly and give the essential functions only. For complete and definitive information,
the reader is referred to ISO 7498.
(1) – concerns the physical, electrical, functional and procedural
Physical layer
characteristics to establish, maintain and disconnect the physical link. It manages the
transmission of bits.
(2) – concerns the reliable sending of blocks of data (frames) over a
Data link layer
physical link. It is concerned with:
– block coding;
– detection of transmission errors;
error recovery;
–
– controlling the access of several stations to a single physical link;
– data link addressing.
Network layer (3) – concerns the transmission of blocks of data (packets) into and
through a transmission network. It manages:
–
network addressing;
– virtual circuits;
– subdividing packets if required by the transmission network;
assuring that packets are delivered in sequence (when requested by an entity in
–
the transport layer);
– packet routing.

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(4) – concerns providing the transparent, reliable and cost-effective
Transport layer
communication of messages between end users. It manages:
– end-to-end control to prevent loss or duplication of messages;
– flow control;
– end-to-end sequence control;
– addressing of transport service user;
– multiplexing transport connections;
– dissassembly and reassembly of messages into packets.
Layer 4 is designed to provide a standard interface to users of the transport service.
(5) – standardizes the process of setting up a communication session
Session layer
between two users. It deals with:
establishing the dialogue rules (who speaks when and for how long);
–
orderly termination;
–
– session restoration without loss of data in case of transmission interruption.
(6) – provides for a common representation of data to be used
Presentation layer
between the local and the remote application. It concerns defining the data elements
and structures as well as carrying out conversions if necessary. It provides rules to
interpret the syntax of the transmitted data.
provides fundamental building blocks (application service
Application layer (7) –
elements – ASE) to facilitate the inter-working of two application programs. These
include:
ACSE association control service element;
FTAM file transfer, access and management;
manufacturing message specification;
MMS
DS directory services;
Specific ASE (for example, for telecontrol);
MHS message handling system.
Telecontrol protocols compatible with ISO standards and CCITT recommendations that
are based on this OSI seven-layer model are defined in the series of IEC 870-6.
4.3 Enhanced performance architecture (EPA)
For real-time process control applications that require particularly short reaction times, an
enhanced performance architecture (EPA) has been designed. This architecture uses only
three layers, namely the physical layer, the link layer and the application layer.
Examples of standard protocols that are based on this reference model are "Mini MAP" and
"Fieldbus" protocols defined for process control applications in local area networks (LANs).

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Telecontrol protocols that are based on the EPA reference model are defined in the series
of I EC 870-5.
4.4 lnterdependance of the layer protocols
Implementations of communication systems do not admit all combinations of standards in
individual protocol layers of the OSI model. The choice of a standard in a given layer is
conditioned by those standards used in the other layers and is influenced by performance
and by implementation complexity.
For example:
the transmission network with the data link configurations used,
–
the line coupler (DCE) used,
–
the synchronization mode used
–
influence the frame formats.
As an other example:
– the window size used,
the initiation mode used,
–
balanced or unbalanced transmission
–
influence the link transmission procedures.
A set of standards necessary to perform a given function is called a functional profile.
4.5 Functional profiles
The basic family of OSI services and protocols provides a set of alternatives for use in a
variety of applications. However, individual- areas of an application require specifically
tailored sets and subsets of the standards. The definition of these specific sets and
subsets is implemented in functional profiles (FP).
The purpose of an FP is to make a recommendation as to how standards should be used
together for a specific communication purpose. An FP defines and makes explicit the
relationships among the sets of standards to be used. It may also specify particular details
of the standards involved. It does not alter the standards to which it refers. An individual
FP is functionally complete, testable and usable.
together with the choice of classes,
An FP consists of one or more base standards
subsets, options and parameters associated therewith necessary for accomplishing a
specific function. Furthermore, it can identify areas in which new standards or addendums
to existing standards are needed when an appropriate standard does not exist.
The scope of an FP is communication between end systems, including the use of a
telecommunication facility and any relays within it. Thus, the FP shall describe the other
systems and subnetworks with which the described OSI system can interwork.

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ISO has developed a classification scheme which identify four main classes of profiles,
namely the following:
F – interchange format and represention profiles specify the structure and/or content of
the information being transferred.
define the choice and manner of use of standards from OSI
A – application profiles
layers 5-7. Usually, an application profile concerns only one kind of information transfer
(f
...