ISO/TS 81346-101:2025
(Main)Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations — Part 101: Modelling concepts, guidelines and requirements for power supply systems
Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations — Part 101: Modelling concepts, guidelines and requirements for power supply systems
This document gives guidelines to support the application of the ISO 81346 and IEC 81346 series to power supply systems. It also specifies best practice for its use and implementation depending on the user and situation. The application of this document supports harmonization within and between the power supply technical domains and industries. Introductory examples of the use of reference designation systems (RDS) can be found in Annex A and Annex B. Annex C provides an example of a conversion table between an example structuring system and the classes specified in this document and other parts of the ISO 81346 and IEC 81346 series.
Systèmes industriels, installations et appareils et produits industriels — Principes de structuration et désignation de référence — Partie 101: Concepts de modélisation, lignes directrices et exigences pour les systèmes d'alimentation électrique
General Information
Standards Content (Sample)
Technical
Specification
ISO/TS 81346-101
First edition
Industrial systems, installations
2025-01
and equipment and industrial
products — Structuring principles
and reference designations —
Part 101:
Modelling concepts, guidelines
and requirements for power
supply systems
Systèmes industriels, installations et appareils et produits
industriels — Principes de structuration et désignation de
référence —
Partie 101: Concepts de modélisation, lignes directrices et
exigences pour les systèmes d'alimentation électrique
Reference number
© ISO 2025
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Modelling principles . 2
5.1 Design for purpose .2
5.2 Receiver’s ownership principle . .3
5.3 Collector system principle .4
5.4 Classification according to inherent functionality .5
5.5 Immaterial instantiation .5
5.6 Parent system and sub-systems .5
5.7 Limited constituent systems.7
5.7.1 General .7
5.7.2 Lower limit.8
5.7.3 Upper limit .8
5.8 Modelling for the future .9
5.9 Preferred semantics .9
5.10 RDS implemented to multiple domains (RDS-PS and RDS-CW) .9
5.11 Use of the symbol “?” .11
5.12 Structuring guidelines .11
6 Top node .12
6.1 General . 12
6.2 Top nodes identifying large systems (stations, plants and factories) . 13
6.3 Other purpose top nodes — temporary structures . 13
6.3.1 General . 13
6.3.2 Orders and bills of materials .14
6.3.3 Modular tasks and views, temporary structures.14
6.4 Top nodes for cataloguing purposes . 15
6.5 Other purpose top nodes — (%) type aspects top nodes .16
7 Aspects . 17
7.1 Reference designation sets .17
7.1.1 General .17
7.1.2 Semantics .18
7.2 Functional aspect [=] . .18
7.3 Type aspect [%] . 20
7.4 Product aspect [-] . 22
7.4.1 General . 22
7.4.2 Assembly structure . . 22
7.4.3 Bill of material structures.24
7.5 Location aspect [+Host of installation] . 25
7.6 Location aspect [++Site of installation] . 25
7.6.1 General . 25
7.6.2 Levels and floors.27
7.6.3 Syntax . . 29
7.7 Location-type aspect [%%] . 29
8 System associations and relationship classification .30
8.1 Implicit association of the hierarchical structure . 30
8.2 RD-set . 30
8.3 Relationship classification .31
8.4 Relationships between aspects .32
iii
9 Classification guidelines — Power supply systems .33
9.1 Prime systems (main systems) . 33
9.1.1 General . 33
9.1.2 Electric power transporting systems (B-systems) . 33
9.1.3 Supporting systems (D-systems) . 33
9.1.4 Managing systems (F-systems) . 33
9.2 Technical systems . 34
9.2.1 General . 34
9.2.2 Consecutive duplicated classes . 34
9.2.3 AA-AE Structural support classes. 36
9.2.4 Pumping systems (KE) or Liquid matter transport systems (JB) . 36
9.2.5 Electrical power supply (HD) or electrical energy storage system (QD) . 36
9.2.6 Electrical energy flow control system (KL) or electrical power distribution
system (JE) .37
9.2.7 Power system phases .37
9.3 Component systems . 38
9.3.1 General . 38
9.3.2 High voltage systems (WB?/WD?) . 38
9.3.3 QMA/QNA/RNA Valves . 38
9.3.4 System phases . . 38
10 Classification guideline — Construction works .38
10.1 General . 38
10.2 Structure identifier. 38
11 Examples . 41
11.1 Generator Excitation System .41
11.2 High pressure oil supply system . .42
12 Implementation guidelines.43
12.1 A recommended aspect . .43
12.2 Depth and structure complexity . 44
12.3 One object performing multiple functions .45
12.3.1 Multiple functions and Single Source of Truth (SSOT) within one system .45
12.3.2 Strict singular product aspect occurrence . 46
12.3.3 Digital Object Identifier (DOI) .47
12.3.4 Preferred reference designations (PRD). 48
12.4 Simplification/adaptation guideline . 50
12.4.1 General . 50
12.4.2 Function aspect for signal structuring . 50
12.4.3 Omitting full stops “.” in between RDS levels . 50
Annex A (informative) Example of use — The circuit breaker .51
Annex B (informative) Example of use — Creation and evolution of an RD-set .53
Annex C (informative) Example of a class conversion table .59
Bibliography .137
iv
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
ISO and IEC draw attention to the possibility that the implementation of this document may involve the
use of (a) patent(s). ISO and IEC take no position concerning the evidence, validity or applicability of any
claimed patent rights in respect thereof. As of the date of publication of this document, ISO and IEC had not
received notice of (a) patent(s) which may be required to implement this document. However, implementers
are cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents and https://patents.iec.ch. ISO and IEC shall not be held
responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
In the IEC, see www.iec.ch/understanding-standards.
This document was prepared jointly by Technical Committee ISO/TC 10, Technical product documentation,
Subcommittee SC 10, Process plant documentation, and Technical Committee IEC/TC 3, Documentation,
graphical symbols and representations of technical information.
A list of all parts in the ISO/IEC 81346 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
v
Introduction
This document provides guidelines for the understanding and application of the ISO 81346 and IEC 81346
reference designation system (RDS) for power supply systems (PS). It was developed in response to
demands by the power supply sector for guidelines to the application of the ISO 81346 and IEC 81346 series,
in particular ISO 81346-10.
PS, and the target industries of this document, include but are not limited to: wind, photovoltaic, thermal,
nuclear and hydropower production.
The very basics of the RDS are not explained in this document. It is assumed that the user of this document
already is familiar with the major concepts detailed in IEC 81346-1 and IEC 81346-2. These concepts include
the four RDS aspects, the basic RDS semantics and basic RDS classification rules.
vi
Technical Specification ISO/TS 81346-101:2025(en)
Industrial systems, installations and equipment and
industrial products — Structuring principles and reference
designations —
Part 101:
Modelling concepts, guidelines and requirements for power
supply systems
1 Scope
This document gives guidelines to support the application of the ISO 81346 and IEC 81346 series to power
supply systems. It also specifies best practice for its use and implementation depending on the user and
situation. The application of this document supports harmonization within and between the power supply
technical domains and industries.
Introductory examples of the use of reference designation systems (RDS) can be found in Annex A and
Annex B. Annex C provides an example of a conversion table between an example structuring system and
the classes specified in this document and other parts of the ISO 81346 and IEC 81346 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
IEC 81346-1:2022, Industrial systems, installations and equipment and industrial products — Structuring
principles and reference designations — Part 1: Basic rules
IEC 81346-2:2019, Industrial systems, installations and equipment and industrial products — Structuring
principles and reference designations — Part 2: Classification of objects and codes for classes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 81346-1:2022, IEC 81346-2:2019
and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
horizontal system
system which has an impact or supports one or more vertical systems (3.3) without being one
EXAMPLE Managing systems (e.g. =F1) or supporting systems (e.g. =D1)
Note 1 to entry: There can be supporting systems within core process (vertical) systems (e.g. the monitoring system
of the generator =A1.RA1.LE1).
3.2
preferred reference designation
PRD
reference designation (RD) used as the main key to identify an object within a database
3.3
vertical system
system that is a part of the core process of the power production, distribution or transmission for power
supply systems
EXAMPLE Production unit systems (e.g. =A1) or energy transport systems (e.g. =C1).
4 Abbreviated terms
For the purposes of this document, the abbreviated terms listed in Table 1 apply.
Table 1 — List of abbreviations
Abbreviation Meaning
BIM building information modelling
CB circuit breaker
CDD IEC common data dictionary
CID construction identifier
CW construction works
DOI digital object identifier
GIS geographic information system
HSE health security and environment
IOD individual object database
P&ID piping and instrumentation diagram
PRD preferred reference designation
PS power supply systems
RD reference designation
RDS reference designation system
SCADA supervisory control and data acquisition
SSOT single source of truth
5 Modelling principles
5.1 Design for purpose
A system can be a constituent of a large and complex system. If so, it will often have a multi-levelled reference
designation (RD). Or it can be such a simple overall system, and the constituents will be represented by a
single level RD. It is the designer’s responsibility to select the appropriate structure to reflect the complexity
of the system in question.
The depth and complexity of a structured representation will be influenced by the innate complexity of the
overall system in question. A nuclear power plant needs many levels to correctly represent and model all
the functionality within it. Not all systems need that level of detail. The representation of highly complex
systems can often benefit from simplifications. It would likely not make sense to include every single system
down to individual bolts and screws when modelling a complete nuclear power plant.
The purpose of creation of the structure (also called model in this document) should also influence the
complexity and granulation of the representation of the system. A model designed to provide an overview
of a chemical park main processes, for example, does not need to include a detailed overview of the layers in
the roof construction of the gardening equipment shed.
The framework set by the selection of aspect should be considered when designing a structure. When
structuring a system based on the functional aspect, the system functional complexity and process criticality
should be looked at, not physical size or cost. Large or costly objects, or both, are not always complex from
a functional point of view. A transformer can be considered quite simple in the functional aspect, no matter
what physical size, complexity of construction or costs it has. It usually has few functional sub-systems,
and a simple functionality. With an RD-based model, depth and level of details should be influenced by its
intended use. The structure should be a tool to benefit the user, not an absolute mirror of reality and all its
details.
EXAMPLE 1 A component in the lower levels of a complex structure (e.g. a motor within a critical sub-system for the
process, =A1.KA1.KK1.MAA1) can be of such importance to the process that a data collecting system can be required
and of interest to the operating party (e.g. =A1.KA1.KK1.MAA1.KED1). Even the sensors connected can be of interest
and can be represented (e.g. =A1.KA1.KK1.MAA1.KED1.BTA1) if useful.
EXAMPLE 2 A simple gate can be represented by a simple structure e.g. only two levels, all within the component system:
=C1.QQF1 – Gate system
=C1.QQF1.MAA1 – Gate motor
or it can be a complex system with heating system, auxiliary power supply, monitoring systems and so on:
=C1.KA1 – Gate system
=C1.KA1.LE1 – Gate system monitoring system
=C1.KA1.LE1.BPA1 – Upstream pressure monitoring system
=C1.KA1.LE1.BPA1.BPA1 – Upstream pressure monitoring 1
= C1.KA1.LE1.BPA1.BPA2 – Upstream pressure monitoring 2
= C1.KA1.LE1.BPA1.BPA3 – Upstream pressure monitoring 3
=C1.KA1.HE1 – Gate heating system
…
The structure gives the proper representation of the system and lets the user of this document understand
the system complexity through the model complexity.
Throughout this document, the basic semantics and classification rules for reference designation systems in
accordance with IEC 81346-1 and IEC 81346-2 are used.
5.2 Receiver’s ownership principle
According to the receiver’s ownership principle shown in Figure 1 and the example in Figure 2, when a
system is intended to link two other systems on the same hierarchical level, and when it is unclear to which
system it belongs, the linking system should be part of the receiving system (in terms of information, matter
or energy of any kind).
Figure 1 — Receiver’s ownership principle
NOTE A valve is the separating agent between a liquid storage system (=D7.QB1) and a transport system (=D7.
JB1). The valve is a sub-system of the transport system, not the storage system, because the transport system is the
receiving system.
Figure 2 — Example of the receiver’s ownership principle
The receiver’s ownership principle is to be used in situations when doubt arises. Common sense and intuitive
ownership should come first. The main goal is that systems should be where a future user expects them to be.
EXAMPLE The cord between a laptop and its charger constitutes the connecting agent between these two systems,
with the laptop being the receiving system. The charger cord is however still a part of the charger, not the laptop.
The receiver’s ownership principle can be used for all aspects.
5.3 Collector system principle
An exception to the receiver’s ownership principle (see 5.2), in the functional aspect, is where multiple
systems meet in a new system where energy, data or matter is collected. This is called the collector system
principle. Examples are systems where a dominant feature is a busbar (i.e. collecting/distributing power to
multiple other systems), or a liquid collection/distribution system.
For these systems the flow control system separating each supplying system to the collecting system should
belong to the former. This is exemplified in Figure 3.
Figure 3 — Example of the collector system principle
It is useful from a process (or even safety) point of view to know which system is being isolated.
The collector system principle only applies to the functional aspect, not the product aspect, where an array
of valves, such as the ones depicted in Figure 3 can be part of the collecting system -C1 (pointing to the same
object individual as =C1).
This situation will often occur for switchgear systems, where breakers isolating a certain larger system are,
in the product aspect, part of the switchgear system. However, in the functional aspect the breakers will be
part of the systems to which the flow of electrical power is being controlled.
5.4 Classification according to inherent functionality
In accordance with the principles of IEC 81346-2, the object should always be classified according to what it
was designed to do, not what it is being used for in a particular case.
EXAMPLE 1 Even if the overall function of the lubrification oil system is to reduce friction, the system supplying
the lubrification oil does not see the final use of the oil, it just supplies it. It is a liquid matter supply system (JB), not a
friction reduction system (KJ).
EXAMPLE 2 A valve opening the flow of the sprinkler system will have the effect of fighting fire. But the valve is a
valve, it is a controlling device for flow, a QMA.
The overall use of a system will often be reflected by a parent system. In the case of Example 2 above, the
valve (QMA) will most likely be a constituent of a firefighting system (PB).
5.5 Immaterial instantiation
In accordance with the principles of IEC 81346-1, instantiating the occurrences (object reference
designations) should avoid situations where the numbering in itself carries meaning, including leading
zeroes. Such information is considered metadata/properties of the object.
EXAMPLE =RA2, where “=RA2” is not necessarily the second generator (in any sense of the word).
The primary concern is to avoid situations where the instantiation carries technical information about the
object in question that should be covered by the type aspect. Certain exceptions are acceptable for grouping/
clustering purposes (see 5.7) and the type aspect (see 7.3). If a company selects to employ meaningful
numbering, the rule should be well documented.
5.6 Parent system and sub-systems
If a system (e.g. HE) primarily affects a larger system (e.g. =D1.JB3), and only that, the former (HE) should be
a sub-system of the latter (=D1.JB3). See “Distribution system 3”, the lower system in Figure 4.
If a system (HE) affects multiple larger system (e.g. =D1.JB1 and =D1.JB2), that system should be considered
lifted to the same level as the two latter systems (=D1.JB1 and D1.JB2). See “Distribution system 1 and 2”, the
two upper systems in Figure 4.
Key
=D1.JB1 cooling water distribution system 1
=D1.JB1.EQD1 cooling water distribution system 1, cooling system
=D1.JB1.WPA1 cooling water distribution system 1, distribution pipe
=D1.JB2 cooling water distribution system 2
=D1.JB2.EQD1 cooling water distribution system 2, cooling system
=D1.JB2.WPA1 cooling water distribution system 2, distribution pipe
=D1.HE1 cooling water supply (supplying distribution systems 1 and 2)
=D1.JB3 cooling water distribution system 3
=D1.JB3.EQD1 cooling water distribution system 3, cooling system
=D1.JB3.WPA1 cooling water distribution system 3, distribution pipe
=D1.JB3.HE1 cooling water distribution system 3, cooling water supply
Figure 4 — Example of structure showing cooling systems on different levels — P&ID
Figure 5 shows a model of an auxiliary water distribution system with its cooling system. Each of the major
piping systems (=D1.JB1, =D1.JB2 and =D1.JB3) have their own cooling systems (=D1.JBn.EQD1). Each of the
(EQD) cooling systems are sub-systems dedicated solely to their respective (JB) piping systems.
Key
1 supplying cooling water
Figure 5 — Example of structure showing cooling systems on different levels
Cooling water on the other hand is supplied to systems =D1.JB1 and D1.JB2 by a common cooling water
supply system (=D1.HE1). Because this system is common to multiple systems on the second level of the
structure it is also on the second level. The third distribution system (=D1.JB3) is particular in that it has a
dedicated cooling water supply system (=D1.JB3.HE1). It is only supplying cooling water to this particular
distribution system and is therefore a sub-system of it.
This proposed design guideline is not absolute. The second cooling water supply system (=D1.JB3.HE1) can
already at this point be elevated to the second level of the structure (=D1.HE2) if, e.g.:
— it is expected (in the future) to feed a fourth piping system;
— it can be used as auxiliary supply systems to the other distribution systems;
— in similar situations, it is expected to feed multiple distribution systems.
5.7 Limited constituent systems
5.7.1 General
The RDS-structures provide the users with a clear overview of the object/system of interest and its
constituent sub-systems. To ensure readability and use friendliness, the system should contain between 5
and 25 sub-systems; a guideline to the lower and upper limits of that range is given in 5.7.2 and 5.7.3.
5.7.2 Lower limit
In cases with systems that contain less than five sub-systems, it is recommended to review the structure
and consider lifting the few sub-systems up one level; such as illustrated in the examples in Figure 6 and
Figure 7, where the monitoring system (=LE1) was superfluous.
Key
…=JB4 oil distribution system
…=JB4.LE1 oil distribution system, monitoring system
…=JB4.LE1.BTA1 oil distribution system, monitoring system, temperature measurement
…=JB4.LE1.BPA1 oil distribution system, monitoring system, pressure measurement
Figure 6 — Example of a potentially unnecessary system
Key
…=JB4 oil distribution system
…=JB4.LE1.BTA1 oil distribution system, temperature measurement
…=JB4.LE1.BPA1 oil distribution system, pressure measurement
Figure 7 — Example of a simplified and improved structure
This principle is a general recommendation. There are many situations where only a few, or even a single
sub-system should figure in the structure.
EXAMPLE If the oil distribution system 4 (=JB4) only had the one single temperature sensor system (=BTA1) as
a child system, it can still belong there. The placement would indicate that the temperature sensor system is a sub-
system of that particular oil distribution system.
5.7.3 Upper limit
Many industrial systems include extreme numbers of similar systems, such as lithium battery racks, solar
panel arrays, or individual pipes or poles in a large distribution line. In these cases, the proposed upper limit
of 25 can be difficult to follow.
Handling of a potentially extreme number of sibling systems can be done by creating multiple instances of
parent systems and distributing the siblings between them by clusters. This can be done either by using the
existing parent classes, or by creating a new level in the structure.
5.8 Modelling for the future
Modelling the systems should be done in accordance with the principles of the ISO 81346 and IEC 81346
series and this document. Modelling with the intent to retrofit old systems, or simply to appease old habits
which can force a suboptimal solution, should be avoided.
It has often been a norm to group systems according to deliveries which shall be avoided in aspects that do
not take this into account; the grouping shall rather follow the functional aspect.
EXAMPLE 1 Hydropower generator bearings are often grouped with the generator because they are supplied
together.
A reference designation shall not be forcefully shortened to meet outdated requirements of old systems.
EXAMPLE 2 Some older SCADA systems are not able to handle object references (tags) of more than 30 characters.
5.9 Preferred semantics
For multi-level reference designations, full stop “.” can be used between elements with only the first prefix
as lead, as illustrated in Figure 8. This is in accordance with the rules of IEC 81346-1.
Although the readability is unaffected by the selection of one or the other, full stop is more commonly
accepted by IT systems than equal, minus or plus signs.
Figure 8 — Example for preferred syntax
5.10 RDS implemented to multiple domains (RDS-PS and RDS-CW)
When modelling systems using the RDS, some class libraries will be better suited than others depending on
the nature of the system in question. In particular ISO 81346-10:2022 (RDS-PS) and ISO 81346-12 (RDS-CW)
provide different tables for functional (“main”) systems and technical systems, corresponding to the power
supply domain (PS), or the construction works domain (CW), in order. These are called “RDS libraries” in
this subclause.
RDS-CW should be used for all systems belonging to the construction work domain. This includes buildings,
general housing, garages and workshops, roads, access tunnels and so on.
Within the hydropower domain it also includes dams, which should be considered wall systems (“B” CW
systems in accordance with ISO 81346-12). With regards to the water storage system, the reservoir function
(i.e. the body of water behind the dam) and all sub-systems related to water management (even those
located within the dam itself) should be considered part of a power supply storage system (E-systems, the
reservoir system) and should be modelled using RDS-PS.
As illustrated in Figure 9, to distinguish and ensure unambiguity when reading the reference designations,
the top node should reflect what RDS library has been used (see Clause 6).
Key
-B1 dam 1
-B1.AA1 dam 1, top/road
-B1.BD1 dam 1, dam structure
-B2 dam 2
-B2.AA1 dam 2, top/road
-B2.BD1 dam 2, dam structure
-E1 reservoir
-E1.KA1 reservoir, flood gate system
-E1.KB1 reservoir, overflow control system
-D1 auxiliary monitoring
-D1.BTA1 auxiliary monitoring, atmospheric temperature monitoring
-D1.BLA1 auxiliary monitoring, snow depth monitoring
Figure 9 — Example of a reservoir, modelling the constituent power supply systems using
ISO 81346-10:2022 and the constituent construction works systems using ISO 81346-12
In situations where multiple domains/libraries are used, there will often be situations where certain
systems can rightfully belong to both structures or constitute the meeting point, or both, between the two
domains.
Another example is shown in Figure 10.
NOTE The heat-exchanger system in a plant extracts heat from process oil. This is part of the power supply
system domain (RDS-PS). The heat is in turn extracted from the cooling water and used to pre-heat ventilation air in
the building – a system within the construction works domain. The heat exchanger between these two systems, the
water-air heat exchanger, can have two reference designations, one in each domain.
Figure 10 — Example of an object with both a PS and CW reference designation
Methods and principles to handle multiple reference designations to the same object are proposed in 12.2.
5.11 Use of the symbol “?”
In situations where component systems are required and should be added to a model, but details about them
are yet undecided, there can be difficulties in assigning them a class.
EXAMPLE Is a certain temperature sensing object going to be a system with Boolean output (BTB), used to
trigger alarms – or is the temperature sensing object going to be a system with
...
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