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ANSI / IEEE C37.1-1987
definition, specification, and analysis of
systems used for supervisory control,
data acquisition, and automatic control
SHlW17
JuIy 6
987
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ANSI/IEEE C37.1-1987
C37.1-1979)
(Revision of ANSI/IEEE
An American National Standard
IEEE Standard Definition, Specification, and
Analysis of Systems Used for
Supervisory Control, Data Acquisition, and
Automatic Control
Sponsor
Substations Committee
of
the
IEEE Power Engineering Society
Secretariat
Institute of Electrical and Electronics Engineers
National Electrical Manufacturers Association
Approved March 22,1984
IEEE Standards Board
Approved December 2 ,1986
American National Standards Institute
o Copyright 1987
by
The Institute
of
Electrical and Electronics Engineers, Inc
345 East 47th Street, New York, NY
10017,
USA
No p a r t of th is pu b l icat ion may be reprodu ced in an y f o rm ,
in an electronic retrieval system or o therwise ,
wi th ou t th e p r io r wr i t t en permiss ion
of
the publisher.
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IEEE Standards documents are developed within the Technical Com-
mittees of the IEEE Societies and the Standards Coordinating Commit-
tees of the IEEE Standards Board. Members of the committees serve
voluntarily and without compensation. They are no t necessarily mem-
bers of the Institute. The standards developed within IEEE represent
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as well as those activities outside of IEEE which have expressed an in-
terest in participating in the development of the standard.
Use of an IEEE Standard is wholly voluntary. The existence of an
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to change brought about through developments in the state of the art
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or reaffirmation. When a document is more than five years old, and has
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ing of portions of standards as they relate t o specific applications. When
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to
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Comments on standards and requests for interpretations should be ad-
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Foreword
(This Foreword is not a part of ANSUIEEE C37.1 1987 , IEEE Standard Definition, Specification, and Analysis of
Systems Used for Supervisory Contro l, Data Acquisition, and Automatic Control.)
This standard applies to systems used for monitoring, switching, and controlling electric apparatus
in unattended or attended substations, generating stations, and power utilization and conversion
facilities. It does not apply to equipment designed for the automatic protection of power system
apparatus o r for switching of communication circuits. The requirements of this standard are in addi-
tion t o those contained in standards relating to the individual devices.
This significantly revised standard was originally a section of ANSI C37.2-1970 which also con-
tained device function numbers. ANSI C37.2-1970 was revised into two standards: ANSI/IEEE
C37 .l-1979, Standard Definition, Specification, and Analysis of Manual, Automatic, and Super-
visory Station Control and Data Acquisition, and ANSI/IEEE C37.2-1979, Electrical Power System
Device Function Numbers. Previous editions were approved by the Standards Institute in 1962,
1956 , 1945, and 1937. The original work on this subject was done by the American Institute of
Electrical Engineers (now the Inst itute of Electrical and Electronics Engineers) and published in
1928 as AIEE No 26.
The standard applies to a rapidly changing technology. It is anticipated therefore that frequent
revision may be desirable. Electrical Power System Device Function Numbers on the other hand
have changed very little over the years. This revision, prepared by the Automatic and Supervisory
System Subcommittee of the IEEE Substat ion Committee, was
an
attempt to bring the standard up
to date and further broaden it s applicability with respect to control, supervisory, and telemetering,
for greater use in many industries.
IEEE Tutorial Course Text 81 EH0 1883-PWR1
is recommended for those not familiar with
Supervisory Control Systems.
The Standards Committee on Power Switchgear, C37, which reviewed and approved this standard,
had the following personnel at the time of approval:
C . L.
Wagner,
Chairman
John D. Hopkins,
Secretary
W. N.
Etothenbuhler,
Executive Vice-chairman o fHigh-Voltage Switchgear Standards
W.
E. Laubach,
Executive Vice-chairman
o f
Low -Vo ltage Switchgear Standards
S.
H. Telander,
Executive Vice-chairman
of IEC
Activ i t ies
Organization Represented Name of Representative
Association of Iron and Steel Engineers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J
M.
Tillman
Electric Light and Power Grou p.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.0.
Craghead
R. L. Capra
K. D. Hendrix
R.
L.
Lindsey
J. P. Markey A l t )
D. . Weston
Institute of Electrical and Electronics Engineers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H. W. Mikulecky
M.
J
Beachy A l t )
G. Hanks
C. A. Mathews AZt)
E.
W.
Schmunk
C. A. Schwalbe
G. W.Walsh
C. E. Zanzie
A l t )
National Electrical Manufactu rers Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. A. Wilson
T. L. Fromm
R. A. McMaster
R . 0.
D.
Whitt
Tennessee Valley Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R. C. St. Clair
Testing Laboratory Grou p . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
L.
Frier
E.
J.
Huber
R.
W.
eelbach
A l t )
U S
Department
of
the Army.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
John S. Robertson
US Department of the Interior, Bureau of Reclamation
. . . . . . . . . . . . . . . . . . . . . . . . R. H. Auerbach
US Department of the Navy, Naval Facilities Engineering Command.
. . . . . . . . . . . . . . .
R. L. Clark
Western Area Power Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. D. imey
This publication is available
from
the Institute of Electrical and Electronics Engineers Service Center,
445 Hoes
Lane, PO
Box
1331,
Piscataway, NJ
088551331.
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The membership of working group 77.1 of the Automatic and Supervisory Systems Subcommittee
which prepared this revised standard had the following personnel at the time this standard was sub-
mitted for approval:
Donald F. Koenig, Chairman
W. J. Ackerman R. Hayner A. Matthey
J.
D. Betz J. Holladay J. OHara
W.
R. Block D. E. Johannson D. G. Rishworth
G. Crask L. W. urtz, J r B. D. Russell
W. Frisbie K. P. Lau
J.
M. Thorson
D. J. Gaushell C. T. Lindeberg G. L. Unzicker
A. Haban M.
S.
Wadkins
The members of the IEEE Automatic and Supervisory Systems Subcommittees who reviewed and
approved this standard were as follows:
A. Matthey,
Chairman
W. J. Ackerman H. Hales C. T. Lindeberg
J. D. Betz D. . Johannson
J.
OHara
W. R. Block D. F. Koenig D. G. Rishworth
G. Crask L. W. Kurt z, Jr B. D. Russell
D. J. Gaushell K. P. Lau J. M. Thorson
A. Haban M. S.Wadkins
When the IEEE Standards Board approved this standard on March
22, 1984,
it had the following
membership:
James H. Beall,
Chairman
John E. May,
Vice Chairman
Sava I. Sherr, Secretary
J. J. Archambault
John T. Boettger
J . V. Bonucchi
Rene Castenschiold
Edward Chelotti
Edward J. &hen
Len S. Gxeyt
Donald C. Fleckenstein
Jay Forster
Daniel L. Goldberg
Donald N. Heirman
Irvin
N.
Howell
Jack Kinn
Joseph L. Koepfinger;
Irving Kolodny
George Konomos
R. F. Lawrence
Donald
T.
Michael;
John
P.
Riganati
Frank L. Rose
Robert W. Seelbach
Jay A. Stewart
Clifford0. Swanson
W. B. Wilkens
Charles J. Wylie
Member emeritus
t Deceased
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Contents
SECTION
PAGE
1
Scope
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
2
.
References
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
3
.
Definitions
..............................................................
3
4
.
Functional Characteristics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
4.1 Typical Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
4.2 System Functional Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5
.
Interfaces
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
5.1 Mechanical
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
5.2 Electrical Power and Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.3 Data and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.4 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6. Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1 Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.2 Vibrationandshock
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32
6.4 Lightning Protection
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
6.5 Acoustic Interference Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
7
.
Characteristics
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35
7.1 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.2 Maintainability
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35
7.3 Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.4 System Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.5 Expandability
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
38
7.6 Changeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
38
8. Marking
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
8.3
Warning
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
9
.
Tests and Inspections 39
Stages of Tests and Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Interface Tests and Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.3 Environmental Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
9.4 Functional Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
System Performance Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Bum-In Tests (Optional)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
Availability Test (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Acceptance Test (Optional)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
9.9 Documentation Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
1 0 Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.2 Installation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
10.3 Operating Instructions and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.4 Maintenance Instructions and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
10.5 Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.5 ManIMachine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.3
SeismicEnvironment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32
6.6 Electromagnetic Interference (emi) and Electromagnetic Compatibility (emc)
. . . . . . .
33
8.1 Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.2 Nameplates
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1
9.2
9.5
9.6
9.7
9.8
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FIGURES PAGE
Fig 1 Scada System Data/Control Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Fig 2 Master-Station Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Fig
3
Remote-Station Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Interface Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Data Communication Equipment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
Communication Channel
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
Fig 7 Noise Criteria (NC) Curves for Speech Communication ........................... 34
Fig
8
Typical Surge Withstand Capability (SWC) Test Points
. . . . . . . . . . . . . . . . . . . . . . . . . . .
41
Fig 4 Manual. Automatic. and Supervisory Control Equipment
Fig 5 Signal Interfaces Between Equipment Governed by this Standard and
Fig 6 Signal Interfaces Between Equipment Governed by this Standard and
TABLES
Table
1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table
8
Table 9
Table 10
Table 11
Analog Input Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Analog Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Digital Electronic Input Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Digital Electronic Output Signals
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
Digital Electromechanical Inputs (Status)
..................................
25
Digital Electromechanical Inputs (Accumulator) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Digital Electromechanical Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Operating Temperature and Humidity by Location . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
Test Stages and Classes of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
SystemInputScenario
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
43
Recommended Electrical Graphic Symbols and Meanings
. . . . . . . . . . . . . . . . . . . . . .
30
APPENDIX
Appendix A Master/Remote Station Interconnections ................................
47
Appendix B Bibliography
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
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A n Am er ican Nationa l S tandard
IEEE Standard Definition, Specification, and
Analysis of Systems Used for
Supervisory Control, Data Acquisition, and
Automatic Control
1. Scope
[ 2 ] ANSI X3.1-1976, American National Stan-
dard Synchronous Signaling Rates for Data
Transmission.
[
31 ANSI X3.4-1977, American National Stan-
This standard applies to, and provides the
basis for, the definition, specification, perfor-
mance analysis, and application of systems dard Code for Information Interchange.
used for supervisory control, data acquisition
or automatic control, or both: in attended or
unattended electric substations, including those
associated with generating stations, and power
[4] ANSI X3.5-1970, American National Stan-
dard Flowchart Symbols and Their Usage in
Information Processing.
utilization and conversion facilities.
[ 5 ] ANSI Y14.15-1966 (R 1973), American
National Standard Electrical and Electronics
his standard does not apply to electomech-
anical or static, protective-relaying equipment. Diagrams (Including Supplements ANSI
(See ANSI/IEEE C37.90-1978 (R 1982) [ l l ] 3
ANSI/IEEE C37.90.1-1974 (R 1979) [1 2] ,
Y14-15a-1970 and ANSI Y14.15b-1973).
ANSI/IEEE C37.91-1985
E131
, ANSI/IEEE [6 ] ANSI 224.21-1957 (R 197 1), American
C37.93-1976 [141, ANSI/IEEE C37.95-1973, National Standard Method for Measurement
(R 1980) [
151
, ANSI/IEEE C37.96-1976 Specifying the Characteristics of Pickups for
(R 1981) [161, and ANSI/IEEE C37.97-1979
(R 1984) [17].
Shock and Vibration.
[7] ANSI/EIA RS-310-C-1977 (R 1983),
Racks, Panels, and Associated Equipment.
2.
References
When the American National Standards
referred t o in this standard are superseded by a
revision approved by the American National
Standards Institute, the revision shall apply.
[ l ] ANSI X3 TR-1-1983, American National
Standard Dictionary for Information Proces-
sing.4
?Syst ems covered by this standard typically use co m-
puters in the master station and at times in the remote
stations. Such computers provide facilities for incorpo-
rating automatic control functions either by the sup-
plier or by the user after the system is installed.
3The numbers in brackets correspond to those of the
[8 ] ANSI/EIA RS-334-1968, Signal Quality at
Interface Between Data Processing Terminal
Equipment and Synchronous Data Communi-
cation Equipment for Serial Data Transmission.
[9 ] ANSI/EIA RS-404-1978, Start-Stop Signal
Quality Between Data Terminal Equipment
and Non-Synchronous Data Communication
Equipment.
[ l o ]
ANSI/IEEE C37.2-1979, IEEE Standard
Electrical Power System Device Function Num-
bers.
[111 ANSI/IEEE C37.90-1978 (R 198 2), IEEE
Standard Relays and Relay Systems Associated
with Electric Power Apparatus.
[12] ANSI/IEEE C37.90.1-1974 (R 1979),
eferences listed in Section 2 of thi; standard.
DeDartment. American National Standards Institute.
IEEE Guide for Surge Withstand Capability
4 . 4 publications are available from the Sales
14iO
Broadway, New York, NY
10018.
(SWC) Tests.
7
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ANSI/IEEE
C37.1-1987
DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR
[13] ANSI/IEEE C37.91.1985, IEEE Guide
for Protective Relay Applications to Power
Transformers.
[141 ANSI/IEEE C37.93-1976, IEEE Guide
for Protective Relay Applications of Audio
Tones over Telephone Channels.
[15] ANSI/IEEE C37.95-1973 (R 1980) , IEEE
Guide for Protective Relaying of Utility-Con-
sumer Interconnections.
[16] ANSI/IEEE C37.96-1976 (R 1981), IEEE
Guide for AC Motor Protection.
[17] ANSI/IEEE C37.97-1979 (R 1984), IEEE
Guide for Protective Relay Applications to
Power System Buses.
[
181 ANSI/IEEE C37.100-1981, IEEE Stan-
dard Definitions for Power Switchgear.
[19] ANSI/IEEE Std 91-1984, IEEE Standard
Graphic Symbols for Logic Functions.
[
201 ANSI/IEEE Std 100-1984,IEEE Standard
Dictionary for Electrical and Electronics Terms.
[21]
ANSI/IEEE Std 200-1975, IEEE Stand-
ard Reference Designations for Electronics
Parts and Equipment.
[22 ANSI/IEEE Std 280-1985, IEEE Standard
Letter Symbols for Quantities Used in Elec-
trical Science and Electrical Engineering.
[23] ANSI/IEEE Std 315-1975, IEEE Standard
Graphic Symbols for Electrical and Electronics
Diagrams.
IEEE Recommended Practice for Seismic Qual-
ification of Class 1E Equipment for Nuclear
Power Generating Stations.
[25] ANSI/IEEE Std 422-1986, IEEE Guide
for t he Design and Installation of Cable Sys-
tems in Power Generating Stations.
[26] ANSI/NEMA ICs 6-1978, Enclosures for
Industrial Control and Systems.
[27] EIA EMC B1-1968, Introduction t o EMC
Designers Guide.
[24] ANSI/IEEE Std 344-1975 (R 1980) ,
5EIA publications are available from Electronic In-
dustries Association, 2001 Eye Street, NW, Washington,
DC
20006.
[28] EIA EMC B2-1968, EMC Specifications,
Standards and Bibiliography
.
[2 9] EIA EMC B3-1968, Testing and Measure-
ment Techniques for Electronic Equipment.
[30] EIA EMC B4-1965, Designers Guide on
Electromagnetic System Design of Electric
Equipment.
[311
EIA EMC B5-1964, Bonding of Electronic
Equipment.
[32] EIA EMC B6-1967, Grounding of Elec-
tronic Equipment.
[33] EIA EMC B7-1966, Enclosures of Elec-
tronic Equipment.
[34] EIA EMC B8-1965, Cabling of Electronic
Equipment.
[35] EIA EMC B9-1966, Filteringof Electronic
Equipment.
[36 ] EIA EMC B1 0- 19 67 , Electromagnetic
Susceptibility.
[37] EIA IE B12-1977, Application Notes on
Interconnection Between Interface Circuits
1969 (R 1981).
Using EIA RS-449-1980 and EIA RS-232C-
[381
EIA RS-232-C-1969 (R 1981) , Interface
Between Data Terminal Equipment Employing
Serial Binary Data Interchange.
[
391 EIA RS-363-1969, Standard for Specify-
ing Signal Quality for Transmitting and Receiv-
ing Data Processing Terminal Equipments
Using Serial Data Transmission at the Interface
with Non-Synchronous Data Communication
Equipment
.
[
401 EIA RS-422-A-1978, Electical Character-
istics of Balanced Voltage Digital Interface
Circuits.
[41]EIA RS-423-A-1978, Electrical Character-
istics of Unbalanced Voltage Digital Interface
Circuits.
[4 2] EIA RS-449-1977, General Purpose 37-
Position and 9-Position Interface for Data
Terminal Equipment and Data Circuit-Termi-
nating Equipment Employing Serial Binary
Data Interchange.
8
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SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL
ANSIlIEEE
C37.1-1987
[43] IEC TC 65-1976, Safety Requirements
for Mains Operated and Related Apparatus for
Household and Similar General Use.6
[44] IEEE Std 525-1978, IEEE Guide for
Selection and Installation of Control and Low-
Voltage Cable Systems in
substation^.^
[45] MIL-HDBK 217D-1982, Reliability Pre-
diction of Electronic Equipment.8
[46] MIL-STD 471A-1973, Maintainability
Demonstration.
[47] MIL-STD 1472C-1981, Human Engineer-
ing Design Criteria for Military System Equip-
ment and Facilities.
[48 ] GAUSHELL, D. J., FRISBIE,
W.
L., and
KUCHEFSKI, M. H. Analysis
of
Analog Data
Dynamics
for
Supervisory Control and Data
Acquis i tion Sys tem , IEEE Paper 82
SM
304-4.
[49] LLOYD AND LIPOW.
Reliability, Man-
agement, Methods, and Mathematics.
Engle-
wood Cliffs, N J : Prentice-Hall, 1962.
3.
Definitions
The definitions of terms contained in this
standard, or in other American National Stan-
dards referred to in this standard, are not in-
tended to embrace all legitimate meanings of
the terms. They are applicable only to the sub-
ject treated in this American National Standard.
Supervisory control and data acquisition sys-
tems may use computers. For standard defini-
tion of computer terms refer to ANSI X3 TR-
1-1983 [ l ] .
6IEC publications are available from American
National Standards Institute, 14 30 Broadway, New
York, NY 10018.
IEEE publications are available from the Institute of
Electrical and Electronics Engineers Service Center, 445
Hoes
Lane, PO Box 1331, Piscataway, NJ 08855-1331.
*MIL publications are available from the Director,
US Navy Publications and Printing Service, Eastern
Division, 700 Robbins Avenue, Philadelphia, PA 191 11.
Definitions in this standard may also be listed
Definitions in ANSI/IEEE Std 100-1984 [201
are used whenever possible; however, sometimes
such definitions do not include the meaning
associated with the equipment governed by
this standard.
alarm condition. A predefined change in the
condition of equipment or the failure of equip-
ment to respond correctly. Indication may be
audible or visual, or both.
analog device. A device that operates with
variables represented by continuously mea-
sured quantities such as voltages, resistances,
rotations, and pressures.
in ANSI/IEEE C37.100-1981 [18].
analog-to-digital (a/d) conversion. Production
of a digital ou tput corresponding to the value
of an analog input quantity.
analog quantity.
A
continuous variable that is
typically digitized and represented as a scalar
value.
automatic. Pertaining to a process or device
that, under specified conditions, functions
without intervention by a human operator.
automatic circuit recloser. A self-controlled
device for automatically interrupting and
reclosing
an
alternating-current circuit, with
a predetermined sequence of opening and re-
closing followed by resetting, hold-closed, or
lockout operation.
automatic control. See: control, (1) utomatic.
automatic line sectionalizer. A self-contained
circuit-opening device that automatically opens
the main electrical circuit through it after sens-
ing and responding to a predetermined number
of successive main current impulses equal to o r
greater than a predetermined magnitude. It
opens while the main electrical circuit is de-
energized. It may also have provision to be
manually operated to interrupt loads.
automatic load throwover equipment (transfer
or switchover). An equipment that automatic-
ally transfers a load t o another source of power
when the original source to which it has been
connected fails, and tha t automatically restores
the load to the original source under desired
conditions.
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C37.1-1987
Modem One
DEFINITION, SPECIFICATION. AND ANALYSIS OF SYSTEMS USED FOR
Modem
Two
NOTE: The restoration of the load t o the preferred
source from the emergency source upon re-energization
of the preferred source after an outage may be
of
the
contin uous circuit restoration type or interrupted cir-
cuit restoration type.
(1)
quipment of the Nonpreferential Type.
Equipment tha t automatically restores the load
to the original source only when the other
source, t o which i t has been connected, fails.
(2)
Fixed Preferential Type.
Equipment in
which the original source always serves as the
preferred source and other source as the emer-
gency source. The automatic transfer equip-
ment will restore the load to the preferred
source upon its re-energization.
3 )
Selective Preferential Typ e.
Equipment in
which either source may serve as the preferred
or the emergency source of preselection as
desired, and which will restore the load to the
preferred source upon its re-energization.
(4)
Semiautomat ic Load Throwover Equip -
m e n t .
An equipment that automatically trans-
fers a load to another (emergency) source of
power when the original (preferred) source to
which it has been connected fails, but requires
manual restoration of the load to the original
source.
automatic reclosing equipment. Equipment
which initiates automatic closing of a switching
device under predetermined conditions without
operator intervention.
automatic opening (tripping). The opening of a
switching device under predetermined condi-
tions without operator intervention.
availability. The ratio of uptime and uptime
plus downtime.
Se e :
7 . 3 , Availability.)
backup. Provision for
an
alternate means of
operation if the primary system is not available.
backup, degraded. A backup capability that
does not perform all of the functions of the
primary system.
baud. The term
baud
defines the signaling
speed, that is, keying rate of the modem.
The signaling speed in baud is equal to the
reciprocal of the shortest element duration in
seconds to be transmitted.
For example, in the following table, th e sig-
naling speed is calculated from the signaling
element duration. In addition, the distinction
between bit rate and baud for two different
types of modems is illustrated.
Signaling
element
duration
Signaling
speed
0.833
ms
1200 Bd
Information
transmitted
per element 1bit
duration
Bit rate 1200 bits
per second
2 bits
2400 bits
per second
The bit rate and baud are not synonymous
and shall not be interchanged in usage. Prefer-
red usage is bit rate, with baud used only when
the details of a communication modem or
channel are specified.
bit.
(1)
east significant. In an
n
bit binary word
its contribution is
(0
or 1) oward the maxi-
mum word value of (2 -1).
2)
most significant. In an
n
bit binary word
its contribution is
(0
or 1 imes 2'
-I))
toward
the maximum word value of (2 -1).
bit rate. The number of bits transferred in a
given time interval. Bits per second is a measure
of the rate at which bits are transmitted.
buffer (buffer storage).
(1)A device in which data are stored tempo-
rarily, in the course of transmission from one
point to another; used to compensate for a dif-
ference
in
the flow of data, or time of occur-
rence of events, when transmitting data from
one device to another.
(2 ) An isolating circuit used to prevent a
driven circuit from influencing a driving circuit.
bum in. A period, usually prior to on-line oper-
ation, during which equipment is continuously
energized for the purpose of forcing infant
mortality failures.
calibration. Adjustment of a device so that the
output is within a specific range for particular
values of t he input.
cathode ray tube (crt). A display device in
which controlled electron beams are used to
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SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL
present alphanumeric or graphical data on an
electroluminescent screen.
channel load factor.
See : 5.4.4
channel, scada. The communication path be-
tween master and remote stations.
See:
Sec-
tion
4,
ig
1.)
checkback message. The response from the
re-
ceiving end to the initiating end of a coded
signal or message.
(1)
artial.
Message from the initiating end is
mirrored by the receiving end back to the
initiating end to verify error-free transmission
of the message.
2)
Comple te .
Message from the initiating
end is interpreted by the receiving end. A new
message is sent to the initiating end to verify
error-free transmission and proper interpreta-
tion of the message.
See : 7.4,
ystem Security.)
common equipment. That complement of
either the master or remote station supervisory
equipment that interfaces with the intercon-
necting channel and is otherwise basic to the
operation of the supervisory system, but is
exclusive of those elements that are peculiar
to and required for the particular applications
and uses of the equipment.
console. That component of the system which
provides facilities for control and observation
of the system. Examples include operators
console, maintenance console.
See :
panel,
control
)
contention.
An
operational condition on a data
communication channel in which no station is
-designated a master station. In contention,
each station on the channel shall monitor the
signals on the channel and wait for a quiescent
condition before initiating a bid for circuit con-
trol.
control. The execution of a system change by
manual means, remote means, automatic
means, or partially automatic means.
(1) utomatic. An arrangement of electrical
controls that provides for switching or control-
ling, or both, of equipment in an automatic
sequence and under predetermined conditions.
(2) closed loop. A type of automatic control
in which control actions are based on signals
fed back from the controlled equipment or sys-
11
ANSI/IEEE
C37.1-1987
tem. For example, remote stations can manage
local voltage conditions by control of load tap
changers and volt amperes reactive
(VAR)
con-
trol compensation equipment.
(3)open loop. A form of control without
feedback.
4)
anual. Control in which the system or
main device, whether direct or power-aided in
operation, is directly controlled by an attend-
ant.
5 )
partial automatic. Control which is a
combination of manual and automatic control.
For example, to cause a voltage reduction the
local automatic load tap changing closed-loop
control may be biased by way of a supervisory
control command.
(6)
remote. Control of a device from a distant
point.
data. Any representation of a digital or analog
quantity to which meaning has been assigned.
data acquisition. The collection of data .
data acquisition system. A centralized system
which receives data from one or more remote
points. A telemetering system. Data may be
transported by either analog or digital tele-
metering.
See ;
teleme ering )
data rate. The rate at which a data path (for
example, channel) carries data, measured in
bits per second (b/s).
data logging. The recording of selected data on
suitable media.
dead band. The range through which an input
can be varied without initiating response.
device (electrical equipment).
An
operating
element such as a relay, contactor, circuit
breaker, switch, valve, or governor used to per-
form a given function in the operation of elec-
trical equipment.
digital quantity. A variable represented by a
number of discrete units.
digital-to-analog (d/a) coversion. Production
of an analog signal whose magnitude is propor-
tional t o the value of a digital input .
disable. A command or condition which pro-
hibits some specific event from proceeding.
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C37.1-1987
DEFINITION, SPECIFICATION, AND ANALYSIS O F SYSTEMS USED
FO R
display, graphic. A hardware device (crt,
plasma panel, arrays of lamps, or light emitting
diodes) used to present pictorial information.
distributed processing. A design in which all
dat a is not processed in one processor. Multiple
processors in the master station or in the re-
mote stations, or both, share the functions.
downtime. The time during which a device or
system is not capable of meeting performance
requirements.
echo.
A
communication technique assuring
that a word received at the termination point
in a system is the same as the word originally
transmitted. The received word is retransmitted
to the sending device and matched to ensure
that the original message was received properly.
electromagnetic compatibility (emc). A mea-
sure of equipment tolerance to external elec-
tromagnetic fields.
electromagnetic interference (emi). A measure
of electromagnetic radiation from equipment.
enable. A command or condition which permits
some specific event to proceed.
engineering units. A unit of measure for use by
operatinglmaintenance personnel usually pro -
vided by scaling the input quantity for display
(meter, stripchart, or crt).
expandability. The capability of a system to be
increased in capacity
or
provided with addi-
tional functions.
See :
7.5.)
event.
A
discrete change of state (status) of a
system or device.
failure. An event that may limit the capability
of an equipment or system to perform its
function(s).
(1)
Critical. Causes a false or undesired opera-
tion of apparatus under control.
2)
Major.
Loss
of control or apparatus which
does not involve a false operation.
3)
Minor.
Loss of data relative to power flow
or equipment status.
failure distribution. The manner in which fail-
ures occur as a function of time; generally ex-
pressed in the form of a curve with the abscissa
being time.
failures. (1) nfant mortality. A characteristic
pattern of failure, sometimes experienced with
new equipment which may contain marginal
components, wherein the number of failures
per unit of time decrease rapidly as the number
of operating hours increase. A burn-in period
may be utilized t o age (or mature) an equip-
ment to reduce the number of marginal com-
ponents.
(2)
random. The pattern of failures for equip-
ment that has passed out of its infant mortality
period and has not reached the wear-out phase
of its operating lifetime. The reliability of an
equipment in this period may be computed by
the equation
where
R
= e-ht
X =
failure rate
t
=
time period of interest
(3) wear out. The pattern of failures experi-
enced when equipment reaches its period of
deterioration. Wear-out failure profiles may be
approximated by a Gaussian (bell curve) dis-
tribution centered on the nominal life of the
equipment.
firmware. Hardware used for the nonvolatile
storage of instructions or data that can be read
only by the computer. Stored information is
not alterable by any computer program.
See :
station, remote.)
function check. A check of master and remote
station equipment by exercising a predefined
component or capability.
(1)
nalog.
Monitor a reference quantity
(2)
Control . Control and indication from a
control-check relay
3) Scan. Accomplished when control func-
tion check has been performed with all remotes
4) oll.
Accomplished when analog function
is performed with all remotes
(5)
Logging. Accomplished when results of
the control function check are logged
hard copy. A permanent record of information
in readable form for human use, for example,
reports, listings, displays, logs, and charts.
hardwired. The implementation of processing
steps within a device by way of the placement
of conductors between components within the
device. The processing steps are not alterable
except by modifying the conducting paths
between components.
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ANSI/IEEE
C37.1-1987
indication.
A
light or other signal (audio or
visual) provided by the man/machine interface
that signifies a particular condit ion.
inhibit. To prevent a specific event from oc-
curring.
log. A printed record of data.
master terminal unit
(MTU).
Refers to the
master station of a supervisory control system
See: station, master).
mean time between failure
(MTBF).
The time
interval (hours) that may be expected between
failures of an operating equipment.
mean time to repair
(MTTR).
The time interval
(hours) that may be expected to return a failed
equipment t o proper operation.
modem. A MOdulator/DEModulator device
which converts serial binary digital data to and
from the signal form appropriate for the respec-
tive communication channel.
multiplexer. (1)A device that allows the inter-
leaving of two or more signals to a single line or
terminal.
( 2 ) A device for selecting one of a number of
inputs and switching its information to the out-
put.
offset.
A
predetermined value modifying the
actual value
so
as to improve the integrity of the
system, for example, the use of a
4
mA signal
to represent zero in a 4 mA to 20 mA system.
panel, control. An assembly of man machine
interface devices. See: 5.5.)
point equipment (poin t). Elements of a super-
visory system, exclusive of the basic common
equipment, which are peculiar to and required
for the performance of a discrete supervisory
function. (See: supervisory control functions.)
(1) larm Point . Station (remote or master,
or both) equipment(s) that inputs a signal to
the alarm function.
(2)
Accumulator Point . Station (remote or
master, or both) equipment(s) that accepts a
pulsing digital input signal to accumulate a
total of pulse counts.
3)Analog Point . Station (remote or master,
or both) equipment(s) that inputs
an
analog
quantity to the analog function.
(4 )
Control Point. Station (remote or master,
or both) equipment(s) that operates to perform
the control function.
5 )
ndicat ion Status)Point .
Station (remote
or master, or both) equipment(s) that accepts a
digital input signal for the function of indica-
tion.
(6)
Sequence
of
Events Point .
Station (re-
mote or master, or both) equipment(s) that
accepts a digital input signal to perform the
function of registering sequence of events.
(7)
Telemetering S election Point . Station (re-
mote or master, or both) equipment(s) for the
selective connection of telemetering transmit-
ting equipment to appropriate telemetering re-
ceiving equipment over an interconnect ing
communication channel. This type of point is
more commonly used in electromechanical or
stand-alone type of supervisory control.
8 )
pare Point. Point equipment that is not
being utilized but is fully wired and equipped.
(9) Wired Poin t.
Point for which all common
equipment, wiring, and space are provided.
To
activate the point requires only the addition of
plug-in hardware.
(10)
Space O nly Point .
Point for which cabi-
net space only is provided for future addition
or wiring and other necessary plug-in equip-
ment.
NOTE: A point may serve for one
or
more
of
the pur-
poses described above, for example, when a supervisory
system is used for combined control and supervision of
remotely operated equipment, a point for supervisory
control and point for supervisory indication may be
combined into a single control and indication point.
polling (data request). The process by which a
data acquisition system selectively requests
data from one or more of its remote terminals.
A remote terminal may be requested to re-
spond with all, or a selected portion
of,
the
data available.
primary.
An
equipment or subsystem which
normally contributes to system operation. See:
backup.
programmable equipment.
A
remote or master
station having one or more of its operations
specified by a program contained in a memory
device.
protocol.
A
strict procedure required to initiate
and maintain communication.
quantization error. The amount that the digital
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DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR
quantity differs from the analog quantity.
Se e :
analog-to-digital (a/d) conversion.)
quiescent supervisory system.
See:
supervisory
system, quiescent.)
refresh rate. The number of times in each
second that the information displayed on a
nonpermanent display, for example, a crt, is
rewritten or re-energized.
relay, interposing. A device which enables the
energy in a high-power circuit t o be switched
by a low-power control signal.
remote terminal unit (RTU). Refers to a re-
mote station equipment of a supervisory sys-
tem. See: station, remote.)
repeatability. The measure of agreement among
multiple readings of an output for the same
value of input, made under the same operating
conditions, approaching from the same direc-
tion, using full-range traverses.
reproducibility. The measure of agreement
among multiple readings of the output for the
same value of input, made under the same
operating conditions, approaching from either
direction, using full-range traverses.
resolution. The least value of the measured
quanti ty which can be distinguished.
scan (interrogation). The process by which a
data acquisition system interrogates remote
stations of points for data.
scan cycle. The time in seconds required to ob-
tain a collection of data (for example, all data
from one remote, all data from all remotes, and
all data of a particular type from all remotes).
serial communication.
A
method of transmitting
information between devices by sending all
bits serially over a single communication chan-
nel.
station, automatic.
A
station that operates in
automatic control mode.
NOTE: An automatic station may go in and out of
operation in response to predetermined voltage, load,
time, or other conditions, or in response to a remote
o r
locally manually operated control device.
station check (supervisory check, status up-
date). The automatic selection, in a definite
order, of all the supervisory
alarm
and indi-
cation points associated with one remote
station or all remote stations of a system, and
the transmission of all the indications to the
master station.
station identification.
A
sequence of signal
elements used to identify a station.
station.
1)
master (of a supervisory system).
The entire complement of devices, functional
modules, and assemblies which are electrically
interconnected to effect the master station
supervisory functions. The equipment includes
the interface with the communication channel
but does not include the interconnecting chan-
nel.
During communication with one or more
remote stations the master station is the supe-
rior in t he communication hierarchy.
(2)remote (of a supervisory system). The
entire complement of devices, functional
modules, and assemblies which are electrically
interconnected
to
effect the remote station
supervisory functions. The equipment includes
the interface with the communication channel
but does not include the interconnecting chan-
nel.
During communication with a master station
the remote station is the subordinate in the
communication hierarchy.
NOTES: Examples of station equipments include
(1) Hardwi red .
Station supervisory equipment which
is comprised entirely o f wired-logic elements.
2 )
Firm ware.
Station supervisory equipment which
uses hardware logic programmed routines in a manner
similar to a computer. The routines can only be modi-
fied by physically exchanging logic memory elements.
3 )
Programmable.
Station supervisory equipment
which uses software routines.
3) semiautomatic.
A
station that requires
both automatic and manual modes to main-
tain the required character of service.
4)
ubmaster. A station that can perform
as
a master station on one message transaction
and as a remote station on another message
transaction.
sta,tus. Information describing a logical state of
a point or equipment.
supervisory control. An arragement for operator
control and supervision of remotely located
apparatus using multiplexing techniques over a
relatively small number of interconnecting
channels.
supervisory control data acquisition system.
A
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ANSI/IEEE
C37.1-1987
system operating with coded signals over com-
munication channels so as to provide controI
of remote equipment (using typically one
communication channel per remote station).
The supervisory system may be combined with
a data acquisition system, by adding the use of
coded signals over communication channels to
acquire information about the status of the re-
mote equipment for display or for recording
functions.
supervisory control functions. Equipment gov-
erned by this standard comprise one or more of
the following functions:
(1)Alarm Func t ion. The capability of a su-
pervisory system to accomplish a predefined
action in response to an alarm condition. See:
alarm condition.)
(2) Analog Function. The capability of a su-
pervisory system to accept , record or display,
or do all of these, an analog quantity as pre-
sented by a transducer or external device. The
transducer may or may not be a part of the
supervisory control system.
(3) Control Function. The capability of a su-
pervisory system to selectively perform man-
ual or automatic, or both, operation (singularly
or in selected groups) of external devices. Con-
trol may be either analog (magnitude or dura-
tion) or digital.
4) ndicat ion Status ) Func t ion. The capa-
bility of a supervisory system to accept, record,
or display, or d o all of these, the status of a
device. The status of a device may be derived
from one or more inputs giving two or more
states of indication.
(a)
Two -State Indicat ion.
Only one of the
two possible positions of the supervised device
is displayed at one time. Such display may be
derived from a single set of contacts.
(b) Three-State Indication. One in which
the transitional state or security indication as
well as the terminal positions of the supervised
device is displayed. Such a display is derived
from at least two sets of initiating contacts.
(c) Multistate Indication. Only one of the
predefined states (transi tional or discrete, or
both) is indicated at a time. Such a display is
derived from multiple inputs.
(d)
Indication with Memory.
An indication
function with the additional capability of stor-
ing single or multiple change(s) of status that
occur between scans.
5 )
Accumulator Func t ion. The capability of
a supervisory system to accept and totalize
digital pulses and make them available for dis-
play or recording, or both.
(6)
Sequence
of
Events Fun c t ion. The capa-
bility of a supervisory system to recognize each
predefined event, associate a time of occurrence
with each event, and present the event data in
order of occurrence of the events.
supervisory system. All control indicating and
associated with telemetering equipment at the
master station and all of the complementary
devices at the remote station, or stations.
(1) ontinuous update. A system in which
the remote station continuously updates indi-
cation and telemetering to the master station
regardless of action taken by the master station.
The remote station may interrupt the continu-
ous data updating to perform a control opera-
tion.
(2)polling. A system in which the master
interrogates each remote to ascertain if there
has been a change since the last interrogation.
Upon detection of a change the master may
request data immediately.
(3)quiescent. A system which is normally
alert but inactive and transmits information
only when a change in indication occurs at the
remote station or when a command operation
is initiated at the master station.
4)
canning. A system in which the master
controls all information exchange. The normal
state is usually one of repetitive communication
with the remote stations.
system time.
A
coordinated value of time main-
tained a t stations throughout the power system.
tag. A visual indication, usually a t the master
station, to indicate that a device has been
cleared for field maintenance/construction
purposes and is not available for control or
data acquisition.
telemetering. (1 Transmission of measurable
quantities using telecommunication techniques.
(a ) Current-Type Telemeter. A telemeter
that employs the magnitude of a single current
as the translating means.
(b) Frequen cy-npe Telemeter. A telemeter
that employs the frequency of a periodically
recurring electric signal
as
the translatingmeans.
(c ) Pulse-Type Telemeter. A telemeter that
employs characteristics of intermittent electric
signals, other than their frequency, as the trans-
lating means.
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C37.1-1987
DEFINITION, SPECIFICATION, AND ANALYSIS
OF
SYSTEMS USED
FOR
(d ) Ratio-Type Telemeter. A telemeter that
employs the relative phase position between, or
the magnitude relation between, two or more
electrical quantit ies as the translating means.
NOTE: Examples
of
ratio-type telemeters include ac or
dc position matching systems.
(e) Voltage-Type Telemeter. A telemeter
that employs the magnitude of a single voltage
as the translating means.
(2) analog. Telemetering in which some char-
acteristic of the transmitter signal
is
propor-
tional t o the quantity being measured.
(3) digital. Telemetering in which a numerical
representation is generated and transmitted; the
number being representative of the quantity
being measured.
terminal. (1)A point in a system or communi-
cation network at which data can either enter
or leave.
(2) An
input/output device capable of trans-
mitting entries to and obtaining output from
the system of which i t is a part, for example,
cathode ray tube (crt) terminal.
test. (1) ertified design. A test performed on a
production model specimen of a generic type of
equipment to establish a specific performance
parameter of that genre of equipment. The
condition and results of the test are described
in a document that
is
signed and attested to by
the testing engineer and other appropriate,
responsible individuals.
(2)
data
(a) The recorded results of test.
(b ) A set of data developed specifically to
test the adequacy of a computer run or system.
They may be actual data taken from previous
operations or artificial data created for this
purpose.
3)point. A predefined location within equip-
ment or routines at which a known result
should be present if the equipment or routine
is operating properly.
time.
(1)
esponse. The time between initiating
some operat ion and obtaining results.
(2)
settling. Time required by channel or ter-
minal equipment t o reach an acceptable opera-
ting condition.
timer, watchdog. A form of interval timer which
is used t o detect a possible malfunction.
transaction. That sequence of messages between
master and remote stations required to perform
a specific function (for example, acquire spe-
cific data or control a selected device).
troubleshoot. Action taken by operating or
maintenance personnel, or both, to isolate a
malfunctioned component of a system. Actions
may be supported by printed procedures, diag-
nostic circuits, test points, and diagnostic rou-
tines.
update. The process of modifying or reestablish-
ing data with more recent information.
uptime. The time during which a device or sys-
tem is capable of meeting performance require-
ments.
4.
Functional Characteristics
The equipment governed by this standard
may be arranged in various configurations and
be required
to
perform some or all of the func-
tions identified in this section.
Typically, equipment governed by this stan-
dard compose a system with at least one master
station and one (typically several) remote
sta-
tion. Figure
1
illustrates the data and control
flow from field sensors and actuators to and
from an operator by way of a master station
and remote-station system.
4.1
Typical Diagrams. Diagrams of typical
equipment and configurations of equipment
governed by this standard are illustrated within
this section.
The media between the stations could be any
suitable communication channel or channels.
The communication protocol typically used
requires a master station to initiate message
transactions.
For brevity, t he terms master and remote de-
note master station and remote station.
The functional components of a master sta-
tion are illustrated in Fig
2.
A dual computer
station is illustrated, however, a single computer
master station may be adequate for some appli-
cations. The functional components of aremote
station are illustrated in Fig
3.
Various inter-
connections of master and remote stations are
illustrated in Appendix A.
The computer system illustrated in Fig
2
as a
single box typically includes mass memory and
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SUPERVISORY CONTROL, DAT A ACQUISITION. AND AUTOMATIC CONTROL
-
M
M
ANSI/IEEE
C37.1-1987
r
R E M O T E
-
T A T I O N-
PULSE
C O U N T E R
P O I N T S
B I N A R Y
D A T A
P O I N T S
D A T A D I S PL A Y S
I N D I C A T I O N
r
C O N T R O L A N D
I N D I C A T I O N
D E V I C E S
~
D A
C O N V E R T E R
I
1
I
N D C A T I O N
P O I N T S
S T A T I O N C H E CK
TR IP-CLOSE
L O W E R R A I S E
CLOSE-OPEN
S T O P -S T A R T
4
r
A N A L O G D A T A
C O U N T E D D A T A
B I N A R Y D A T A
L A R M S A N D
L
T A T U S
I N D I C A T I O N S 1
IP l
P O I N T S
Fig
1
Scada System Data/Control Flow
C O M P U T E R
S U B S Y S T E M
C O M P U T E R C O M P U T E R
S Y S T E M
C O M M U N I C A T I O N S
I N T E R F A C E
A N A L O G R E C O R D E RS
D I G I T A L D I S P L A Y S
I
I LRTUUNCTIONS
I i
Fig 2
Master-Station Block Diagram
various peripherals. It is common practice to interface remote station communication chan-
switch the complete computer system in the
nels to the primary computer system. The
event of a peripherial or computer failure rather man/machine subsystem is that equipment
than attempt to reconfigure a system by switch- used to present information to the operator(s)
ing peripherials. The communication interface and to accept inputs from the operator@).
subsystem of Fig
2
is that equipment used to
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ANSI/IEEE
C37.1-1987
INTERFACE
I
I
1
DEFINITION, SPECIFICATION, A ND ANALYSIS OF SYSTEMS USED FOR
I
I
I
I
I
I LOGIC
I
COMMON
( 1 ) STATUS AND ALA RM PULSE
INPUTS INPUTS FROM
( 2 )
SWITCH POSITIONS ACCUM ULATO R'
F R O M M A N U A L E N T R Y (W A T T H O UR
PANELS METERS, ETC)
I
*
I POWER
OWER
SUPPLY
TRANSDUCERS RELAYS
D/A CONVER
I
TERS, ETC
I
I
I POINT INPUTiOUTPUT LOGIC
(1 CONTACT OUTPUTS
TO CIRCUIT BREAKERS,
ANA LOG OUTPUTS DISCONNECT SWITCHES, ETC
TO SETPOINT ( 2 ) CONTACT OUTPUTS
CONTROLLERS TO DIG ITAL SETPOINT
CONTROLLERS
Fig
3
Remote-Station Block Diagram
4.2
System Functional Characteristics. This
section provides guidance for helping both sup-
pliers and users define the functional capabili-
ties that may be required in a system. Not all
of the capabilities discussed below are required
in every system. When a function or capability
is
not required, tha t fact shall be noted.
Each generic function is addressed in a sub-
section that follows in terms
of
the minimum
features or characteristics that should be ad-
dressed to adequately define the function.
Definition of the system functions is a joint
responsibility of the user and supplier . The sub-
paragraphs that follow provide a checklist that
will help ensure adequate communication be-
tween the user and supplier of equipment
governed by this standard.
When the feature or characteristic is fixed by
the design of the equipment the burden of defi-
nition rests on the supplier (for example, num-
ber of inputs/ou tputs per card). However,
variable features (for example, scaling resistors,
switch settings, firmware, and software) should
be jointly defined by the user and the supplier.
4.2.1 Communication Management. The capa-
bilities to manage communication between the
master station and the remote station shall be
well defined. The topics to be defined include
(1)
Message protocol
(2 ) Number of channels
(3) Bit rate
4)
rror detection techniques
5)
Channel switching
(6)
Number of remotes per channel
( 7 )
Number of retries each at tempt
(8)
Number of attempts per hour
(9) Time out value(s)
(10)
Communication error reporting
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SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL
ANSI/IEEE
C37 . 1 - 1 9 8 7
(11)Channel quality monitoring (normal and
(12)
Loop-back provisions
4.2.2
Data Acquisition. (See
5.3).
When data
acquisition is a function to be performed, the
characteristics for each data type shall be
defined. Ranges of data input, scale factors,
rates, and accuracy shall be defined for
backup)
(1)
Analog inputs
(2)
Indication inputs-single bit
(3)
Indication inputs-multibit
(4)
Indication inputs-with memory
5 )
Accumulator inputs
(6)
Sequence of events inputs
The data acquisition capability for each data
type shall be defined in terms of the following
characteristics.
Scan Groups.
How many scan groups, size of
group, inputs in each group.
Scan Cyc le .
Each group (seconds to complete
an
acquisition from all remotes).
NOTE: The communication hardware related perform-
ance capabilities used in the calculation of scan cycle
shall
be
defined.
4.2.2.1 Remote- Station Data Acquisition.
When the remote station locally acquires data
between master-station data requests, the
capacity (total inputs) and rate of acquisition
(inputs per second) for field data interfaced to
remote-station equipment shall be defined for
each of the above data types.
The modularity (for example, number of in-
puts per card) of each data type shall also be
specified.
4.2.2.2
Master-Station Data Acquisition.
The capacity (total inputs) and rate of acquisi-
tion (inputs per second) for local or remote-
station data interfaced to master-station
equipment shall be defined for all applicable
data types.
4.2.3
Data Processing. Data processing capa-
bilities shall be defined for each equipment and
data type. Systems with report-by-exception
functions shall have the capability to report all
data for initialization and periodic update
purposes.
4.2.3.1
Analog Data Processing. Analog
change detection may be a function included
as
an alternative to processing every input on
every scan. Analog change detection is accom-
plished by testing to see if the new value for
each input is within N digital counts (for exam-
ple, dead band) of the last stored value for that
input. The new value shall replace the last stored
value only if the dead band was exceeded and
then the input will be further processed
as
de-
fined below. When the analog change detection
function is included, the following characteris-
tics shall be defined:
(1)Location of processing, remote or master,
or both
(2)
Range of N- remo te or master, or both
(3)
Applicability of N-re mote, card, or point
4) echnique for changing value of N
When the analog change detection is imple-
mented
in the remote stat ion,
its output may
be used by an analog data report-by-exception
function to save communication of unchanged
data from the remote station to the master
station. When the analog data report-by-excep-
tion function is included the following charac-
teristics shall be defined.
(1)Percent of analog changes per scan that
results in the channel load associated with
reporting all analog points from the remote
terminal unit (RTU).
(2)
Description of logic in the master station
that can be used to select between using the
Analog Data Report-by-Exception function or
the Report All Analog Data Functions when
acquiring analog data from each remote station.
Filtering of analog data may be provided to
smooth such data before it is used by other
functions. When this function is included, de-
fine the equation used and the time delay
introduced by the filtering.
Analog data conversion to engineering units
is typically required before analog data
is
used
by the operator, other software, or printed in
an alarm message. The mathematical equa-
tion(s) used to convert analog values repre-
sented
by
digital counts into the corresponding
engineering units shall be defined. Specific
attention shall be given to sensor and trans-
ducer scale factors that may be provided by the
user.
Scaling of analog inputs should give adequate
consideration to off-normal operation of the
power system (for example, over voltage,
emergency load limits).
Techniques that are used to
(1)Detect an open input to an analog chan-
2) Identify reasonable values, or
(3) Automatically calibrate an analog chan-
nel, or a combination of these three shall be
defined.
nel, or
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ANSI/IEEE
C37 . 1 -1987 DEFINITION, SPEC
Analog data limit checking is typically in-
cluded to determine if other downstream func-
tions such as alarm management or further pro-
cessing
is
required. The number of high or low
limits accommodated and associated dead-band
processing, shall be defined. Specific attention
shall be given to the procedure for user speci-
fication and revision of limit and dead-band
values.
4.2.3.2
Indication Data Processing. Indica-
tion input change detection may be a function
included as an alternative to processing every
input on every scan. Indication input change
detection is performed by testing to see if the
current indication is the same as the last stored
indication for that input. Changed indications
shall replace the last stored value and the point
or group of inputs shall be routed for other
downstream functions such as indication data
report by exception, or alarm management, or
both.
When the Indication Input Change Detection
function is included, the following characteris-
tics shall be defined:
(1)Location of processing (remote or master)
(2)
Quanti ty of da ta reported when a single
(3)Minimum signal duration
When the indication input change detection
function is implemented in
the remote
station,
its output may be used by an indication data
report-byexc ept ion function to save communi-
cation of unchanged data from the remote
station to the master station. When the indica-
tion data repor t-byexception function is in-
cluded, the following characteristics shall be
defined:
(1)Percent of indication point changes per
scan that results in the channel load associated
with reporting all indication points from the
remote.
(2)
Description of logic in the master or re-
mote station tha t can be used to select between
using the indication data report-by-exception
or t he report all indication data function when
acquiring indication data from each remote.
Indication with memory may be a function
implemented in th e remote. When this function
is
included, define the number of status changes
accommodated, and legal bit combinations
supported by the design.
Define the sta tus data processing options sup-
ported. Particular attention shall be given to
input changes
'IFICATION, AND ANALYSIS OF SYSTEMS USED
FOR
input validity processing and to the interface
between the supervisory control function and
the status data processing function.
4.2.3.3
Accumulator Data Processing. When
pulse accumulation and pulse accumulator data
processing is included the following character-
istics shall be defined:
(1)
nput circuit
(2
or
3
connections)
(2)
Sources of freeze command (internal/
3)
Ranges of values (remote and master
4)
ominal and maximum counting rates
5 )
Source of memory power
external)
station)
4.2.3.4
Sequence of Events (SOE) Data.
When a sequence of events data acquistion ca-
pability is included the following characteris-
tics shall be defined:
(1)Time resolution (at and between remotes)
(2)
Method of system time synchronization
3) Time accuracy between any two remote
4) umber of
SOE
inputs
5 ) Size of buffers (number of SOE messages
which can be stored)
(6)
Time (Minimum/Maximum) between suc-
cessive change of an input
(7 ) Method of indicating tha t SOE data is
available
(8) Data filter time constant (for example,
contact de-bounce)
(9)
Data time skew (introduced by de-bounce
filters)
4.2.3.5
Computed Data Points. When the
capability of computing data or results (that
are not directly measured) is included the fol-
lowing characteristics shall be defined:
stations
(1)Location (remote or master)
(2)Equations supported
(3)
Resulting data types (numeric or logical,
or both)
4) ownstream functions (for example,
limit checking)
4.2.3.6 Alarm Management. When the capa-
bility to manage and report alarm conditions is
included the following characteristics shall be
defined:
(1)Conditions reported as alarms
(2)Methods of acknowledgement (single or
3)Methods of highlighting reports (flash,
4)
nformation in alarm messages
5 )
Hierarchy of alarms (priority level)
groups )
tone, etc)
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SUPERVISORY CONTROL, DATA ACQUISITION, AN D AUTOMATIC CONTROL
ANSI/IEEE
C37.1-1987
(6)
Size of alarm queue(s)
(7)
Queue management (for example, time
(8)
Alarm limit@)
4.2.4 Supervisory Control Characteristics
Se e : 5.3) . When the capability to remotely
control external apparatus is provided, the
characteristics of such a control capability shall
be defined.
Definition of characteristics common to all
control interfaces shall include
(1)Control sequence description
(2)Type
of
checkback message (partial or
complete)
(3) Security of control sequences
4)mmediate operate controls
(5) Broadcast controls
ordered)
4.2.4.1 Apparatus Control with Relay In-
terface. Control using a relay output shall be
described as follows:
(1) Dwell time of relay contacts
(2)
Number of relays that can be simultane-
ously energized in each type of remote
3)Processing actions (for example, logging,
and alarm suppression)
4.2.4.2 Apparatus Control with Setpoint
Interface. Control using a setpoint out put shall
be defined for
(1)Resolution of setpoint value
(2) Duration of outpu t value
(3) Processing actions (for example, limit
check, equation, and alarms)
4.2.4.3 Apparatus Control with Electronic
Interface. Control using a solid-state interface
shall be described as follows:
(1)
Timing diagram of signals
(2 ) Interface communication protocol
3) Processing actions associated with control
4.2.5 Automatic Control. When the capability
to automatically control external apparatus is
provided the characteristics of such control
capabilities shall be defined
1) ocation of automatic control logic (re-
mote or master)
(2) Control equation@)
3)
Frequency of execution
4) ield alterable control criteria
(5) Associated logging or alarming
4.2.6 Operator Interface Characteristics. The
capability to support data or control interfaces
to operating or maintenance personnel at either
the master or remote station shall be described.
4.2.6.1 Control of Equipment Functions.
When operator controllable functions are in-
cluded the applicable characteristics shall be
defined:
(1)
Control outpu t interfaces
(a) Enable/disable
(b ) Tagging (types and uses)
(c) Local/remote
2) Control of data acquisition
(a) Enable/disable scan (inputs o r stations)
(b ) Enable/disable processing
(c) Manual entry of data
(d ) Change scan frequency by group
(e) Assign/reassign data to a group
3) Control of data processing
(a) Setting date and time
(b) Setting input change limits
(c) Defining formats
(d) Defining conversiondata
(e) Defining operator override values
4)
ontrol of alarm processing
(a) Enable/disable individual alarms
(b) Enterledit alarm limits
(c) Enter/edit alarm dead-band
(d) Edit alarm to operator assignment
(e) Acknowledge alarms (individual/page)
(f) Silence audible alarm
(g) Inhibit alarms
(h) Override invalid alarms
5)
Control of function checks
(a) Enable/disable
(b ) Change frequency
(a) Enable/disable
(b) Modify criteria
(c) Add/delete control functions
(d) Reset to reference level or position
(6)Control of automatic control functions
4.2.6.2 CRT Display Capabilities. When
crt formats are supported the applicable char-
acteristics shall be defined
(1)Generation of display formats
(a) Format definition capabilities
(b ) Symbols supported
(c) Memory per format
(d ) Use of colors
(e ) Use of special features (flash, inverse
(f) Control level of detail
(2)
Standard formats
(a) Index formats
(b) System formats
(c) Communication channel format
(d ) Summary of inhibited alarms
video, etc)
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C37.1-1987
DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR
(e) Input point profile formats
( f ) Alarmsummary
(h) Station notes format
(3) Control of crt and cursor
(a ) Cursor operation
(b) Selection of formats
(c) Response time
(d) Update cycle (from data base)
(e) Paging of multipage formats
4.2.6.3
Digital and Analog Displays. When
such display devices are supported theapplic-
able characteristics shall be defined
(a) Numeric range with decimal
(b) Update frequency
(c) Maximum number supported
(a) Ranges
(b) Update frequency
(c) Maximum number supported
4.2.6.4
Hardcopy Devices. When support of
hardcopy devices is required such as loggers,
strip chart recorders, and crt video-copiers
the applicable characteristics shall be defined
as
follows:
(g) Tag summary
(1)Digital displays
(2) Analog displays
(1)Device assignments
(a) Initial
(b ) Automatic re-assignment
(c ) Manual re-assignment
(2)
Generation of log formats
(a) On-line/batch capabilities
(b) Symbols supported
(c) Spooling capabilities
(a) Standard formats
(b) Time for response
(a) Standard events (for example, operator
and actions)
(b) System events (for example, computer
failover and communication failure)
4.2.7
Computer Backup and Switchover.
When primary and backup facilities are provided
the applicable characteristics shall be defined as
follows:
(3)
Demand logs
4) ogged activities
(1)
Data base backup
(a) Data residency (bulk or main memory)
(b ) Frequency of update (by data type)
(c) Other uses of backup facilities
(a) Method of failure detection
(b) Response time for detection
(2)
Failure monitoring
(3)
Switchover
(a) Method of switchover
(b ) Time required for switchover
(c) Operator interface response following
(d ) Operator actions following switchover
4.2.8
History Data. When a capability for
history data acquisition, archiving and retrieval
is provided, the appropriate characteristics
shall be defined as follows:
switch over
(1)
Number of history files supported
(2)
Data quantities per file
3) Data intervals per file
4) umber of data intervals per file
(5)
Method of file management
(6)Method of data archiving
( 7 )
Method of data retrieval
5.
Interfaces
The equipment governed by this standard
shall have interfaces as described in this section.
The interfaces described consist of those illus-
trated in Fig 4.
Fig 4
Manual, Automatic, and Supervisory
Control Equipment Interface Block Diagram
POWER SOURCE
AN0 GROUNDING
INTERFACES
(REFER TO SECTION 5 2)
I
AUTOMATIC
CONTROL
EOUIPMENT
I
ATA AN0 CONTRX
INTERFACES
(REFER TO SECTION
531
5.1
Mechanical
5.1.1
Enclosures. Equipment located
in
an
outdoor environment shall utilize enclosures
which satisfy t he requirements defined for the
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SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL
specified environment by ANSI/IEEE ICs
6-
1978 [26] .
Equipment which is housed in a building or
other suitable enclosure in which it is protected
from the weather shall utilize enclosures meet-
ing the requirements of ANSI/EIA RS-310-C-
1977
(R
1983) [7].
5.1.2
Special Requirements. The location of
access doors, enclosure mounting requirements,
cooling requirements, terminal-block type and
location, cable entry locations, and special
cabling and connector requirements should be
specified for individual applications.
When required, electromagnetic shielding
characteristics of en