Reference Designation System for Power Plants

Reference designation is a highly modern, future-oriented method of plant classification. The Reference Designation System for Power Plants (RDS-PP) provides the basis for object-oriented identification of the individual plant components with any number of relations with other objects.

The new classification system has many advantages, especially, when it is applied to modern organization systems, e.g. plant management or maintenance systems.

Please note: In the text below, the term “alphanumeric” is only used to describe letter characters.

Application especially in the wind energy sector

RDS-PP is mainly used in plants in the wind energy industry – i.e. in wind power plants or wind turbines. Here in the form of the RDS-PP application guideline part 32: wind power plants of the professional association VGB PowerTech.

However, the system is also applicable to all types of power plants and is therefore not explicitly limited to wind power plants.

Reference standard and regulations

The Reference Designation System for Power Plants is a standard-based system developed by the professional association VGB PowerTech for the identification of power plants. It is a further development of the power plant classification system (KKS), which is not specific to any particular language, power plant type, or field.

The evolution of RDS-PP

With the development of the new system a reference standard should be established. The DIN standard 6779 entitled “Structuring principles for technical products and technical product documentation,” contains the most important general conditions for RDS-PP. Based on this series of standards, a standard DIN 6779-10 was developed especially for power plants by the VGBPowerTech e.V.

The national standard was accepted by the ISO (International Organization for Standardization) in early 2008 and published as an international standard under the name ISO/TS 16952-10. The IEC (International Electrotechnical Commission) had already published the international series of standards IEC 61346 on the structuring principles and reference designations of industrial systems, installations and equipment and industrial products.The ISO/TS 16952-10 was integrated in 2015 one to one into the series IEC 81346 with the name IEC 81346-10.

To unify the standards for reference designation, the organizations agreed on a future generic series of standards with the name DIN EN 81346. Moreover, the standard Reference Designation System for Power Plants (RDS-PP) includes rules for the reference designation of signals (IEC 81175), for identification of terminals (IEC 81666), and for the classification and identification of documents (IEC 81355).

With its reference to these international series of standards, the RDS-PP is an internationally recognized standard for identifying power plants.

Guideline B101 and application explanations B116 developed by the working panels of the professional association VGB PowerTech e.V. are also part of the RDS-PP code. They contain the code letters for the system classification for power plants and assistance and examples for applying the classification system.

General Description

The main tasks of a classification system for power plants are:

  • A transparent identification of technical objects and documents.
  • classification according to purpose, task, and composition.
  • representation of the technical structures.
  • representation of networked relationships.

The basic structuring principles include three different aspects for structuring the various plants. In this context, it is important to clarify three important questions for each individual object:

  • Functional: Which function possesses or manipulates the object?
  • Location-related: Where is the object located?
  • Product-related: What type of object is it?

In a plant identified according to RDS-PP, four different but hierarchically related structure trees therefore result.

  • the function,
  • the product
  • and the location

of technical objects. In addition to a structure tree of functional relationships.

As a designation system with “functional allocation” the RDS-PP has the possibility of establishing a connection between two functions. The shared aspects of the structures or relationships between the different trees are referred to as role relationships.

These relationships between the different aspects of a designated object under consideration are the core of the reference designation system. They can provide information about the components in the various types of document and products involved in the system.

In addition to the reference designation according to function, location, and product aspects, according to the IEC 81346-1 the Reference Designation System for Power Plants (RDS-PP) also contains a specific designation for signals, terminals, and documents, which is derived from the function of the object and a higher-level conjoint designation.

The identifier of an object to be identified can therefore consist of three different partsat maximum:

  • the conjoint designation,
  • the reference designation,
  • and a specific designation.

Different combinations of these three components are possible in the composition of the identifier:

Conjoint designation
Conjoint designation Reference designation
Conjoint designation Reference designation Specific designation
Conjoint designation Specific designation
Reference designation
Reference designation Specific designation

Each of the three sections of the identifier can consist of one or more so-called designation blocks with different structures.

A designation block is subdivided into different levels that contain different combinations of letters and numerals.

The smallest unit of information of the reference designation are the data characters. These are grouped together into alphanumeric and numeric sections at the relevant levels.

The individual blocks can be identified by a defined prefix character. The following table shows the various designation blocks with the relevant prefixes and sources:

Prefix Designation Designation tasks / aspects Prefix origin, basic principles specified in
# Number Conjoint designation ISO/TS 16952-1
= Equals Function-oriented designation IEC 81346-1
== Equals Equals Functional allocation ISO/TS 16952-1
+ Plus Point of installation IEC 81346-1
++ Plus-Plus Location ISO/TS 16952-1
Minus Product-oriented designation IEC 81346-1
: Colon Terminal designation IEC 81666
; Semicolon Signal designation IEC 81175
& And Document designation IEC 61355

In addition, different designation blocks can also be combined with one another. The prefix that is furthest right always determines the aspect of the entire reference designation.


Conjoint designation

For the conjoint designation section, RDS-PP provides a designation block of the same name with a fixed structure. For the conjoint designation, the IEC 81346-10 provides two levels separated by a period, each with up to twelve alphanumeric or numeric data characters.

The block therefore makes it possible to differentiate, for example, different locations or control centers with common aspects.

The designation block is introduced by the hash sign. The conjoint designation is an independent block because it is neither aspect-oriented nor assignable to the specific designation.

For this reason, it provides a separate section:

Breakdown level   1   3
Section   1….4   5
Data character # A….N . A….N
Example # KW01 . E10

Reference designation

The section reference designation has the task of identifying the object to be described according to the three different aspects that have already been mentioned

  • Function
  • Location
  • and Type

In total, one distinguishes between five different types of designation blocks.


1. The function block

This is one of two function-oriented designation blocks. It structures the technical objects of a plant from the viewpoint of the task and purpose of the components. This designation block is structured according to 3 different breakdown levels. For the higher-level distinction, a maximum of one alphanumeric and two numeric data characters are available at the breakdown level 0. The other two breakdown levels each consist of combinations of five with three or two alphanumeric and two or three numeric data characters. The classification of the alphanumeric data characters is defined at breakdown level 1 by the VGB code B101 and at breakdown level 2 by the IEC 81346-2.

Breakdown level   0 1 2
Section   0 1 2 3 4
Data character = AN(N) AAA NN AA NNN
Example = D0 LAC 10 GP 010

2. The function-orientated designation

This has the task of grouping together technical facilities of different types under a common function. For example, the mechanical parts of a pump and its electrical controls are assigned to the same function. A distinction is made between two types of functional assignment:

  1. The group level for identifying function areas and function groups. This only comprises of the system designation with the breakdown levels zero and one.
  2. At the individual level technical facilities are more specifically functionally grouped.

This designation block consists of all three breakdown levels. Both at the group level and at the individual level, a third breakdown level can be appended, separated by a period. This represents an I&C function for the functional allocation. In this block, too, the classification of the alphanumeric data characters of breakdown levels 1, 2, and 3 must be made by the defined code B101 and IEC 81346-2.

Breakdown level   0 1 2   3
Section     1 2 3 4   5
Data character == AN(N) AAA NN AA NNN . AANN
Example == D0 MKV 10 GA 010 . AA01
Code letter Designation
AA Signaling, monitoring
CA Individual closed-loop control
CB Pilot control
HA Operation control and monitoring
MA Direct measurement
MB Measured quantity calculation
SA Individual open-loop control
SB Group control
ZA Equipment unit protection
ZB Plant protection

3. The product designation

Its purpose is to identify the product aspects or the type of an object. It groups together all objects of one type and establishes the connection to the manufacturer or supplier by the product reference. The simple product designation for acquiring devices and modules contains 2 alphanumeric and up to 3 numeric data characters. In this case, the classification is made exclusively according to the Norm IEC 81346-2 standard. The product-oriented designation is preceded by a minus sign. In the identification of the constituent parts of a product, the nested product designation can be used. It enables multiple designation blocks to be concatenated, and the prefix only has to be written in front of the first block. The combination of the designation blocks function and product is called the component designation. It is therefore possible to move from the function aspect to the product aspect.

Breakdown level   1 2
Section   1 2 3 4
Data character AA (N)NN AA (N)NN
Example MA 01 XD 02

4. The point of installation and the location designation

These serve to provide a designation regarding location. Both have very similar structures. The point of installation designation block describes the physical location of a technical object with respect to its task. The code of the RDS-PP reference designation system makes a distinction between the following tasks:

  • Point of installation in installation units of the electrical and I&C engineering
  • System-oriented installation units of the electrical and I&C engineering
  • Location-oriented installation units of the electrical and I&C engineering
  • Points of installation in mechanical and civil engineering equipment

The point of installation designation contains all or parts of the designation of the function block. Depending on which task it is assigned to, the point of installation can have up to 3 or 4 breakdown levels. It is also possible to relate the points of installation to their location. This can be done by taking over the first breakdown level of the location block.

Breakdown level   0 1 2   3
Section     1 2 3 4   5
Data character + AN(N) AAA NN AA NNN . A../..N
Example + D0 LAC 10 GP 010 . Outlet

The system-oriented and location-oriented installation units of the electrical engineering and I&C and the points of installation of the mechanical engineering and civil engineering have the structure shown in the table below.

In the case of points of installation in installation units of the electrical engineering and I&C, the second breakdown level can be omitted. In that case, only the system level (breakdown level 1) of the function designation is taken over. Breakdown level 3 can contain up to twelve freely selectable data characters. The point of installation identification is recognizable by a preceding plus sign.

The reference designation of the location has the same structure as the “point of installation” in installation units of the electrical and I&C engineering. It has the task of describing locations. Takeover of the function reference designation establishes the building reference of the technical equipment.

Breakdown level   0 1   3
Section   0 1 2   5
Data character ++ AN(N) AAA NN . A../..N
Example ++ D0 ULA 10 . R 010


Specific designation

Alongside the function-oriented, product-oriented, and location-oriented designations, the specific designations are an important function in the Reference Designation System for Power Plants according to RDS-PP. These allow an unambiguous identification of signals, terminals, and documents.

Combined with the function reference designation, the signal block provides unequivocal signal identification.

Breakdown level   1   3
Section   1 2 3 5
Data character ; AA NNN . A…..N
Example ; XQ 001 .  

The individual signals are classified according to IEC 81175. The first data character of the breakdown level 1 distinguishes between the main classes signal origin (code letter: X) and signal application (code letter: Y).

Both the subclasses and the count numbers of the signal classes are defined in the power-plant-specific standard IEC 81346-10. The prefix for the identification of signals is a semicolon.

Similar to the signals, the identification of terminals of technical objects is composed of a reference designation and a terminal designation. In classification of the terminals, it is possible to use the existing terminal identifiers of the components. In components without designated terminals, the code letters can be taken from the standards for mechanical engineering and electrical engineering.

Unlike the other designation blocks, the sections of the terminal designation can contain lowercase letters and special characters.

Breakdown level   1   3
Section   1   5
Data character : A../..N . A../..N
Example : PE1 .

Identification of documents with RDS-PP

The identification of documents is implemented in the RDS-PP with a combination of three different designation blocks.

The object designation usually consists of the function block. In this case, the depth of the structure can be determined by the user. Depending on the document, it is possible to use only the system level or the entire component designation as the object designation. The generally valid DCC (document class code) of the series of standards DIN EN 61355 is used to identify the document type. This series of standards both defines the code letters and contains the various numbering specifications.

The last part of the document designation is used for counting different pages of a document.

Applying the designation system

According to the ways of combining the individual sections of an indicator stated above, various concatenations and assignments of the individual designation blocks result. Concatenating one or more blocks always results in a new unique designation with a defined aspect.

The following table summarizes all permissible concatenations of the classification system.

Concatenations of designation blocks
= Function Product    
= Function Product : Terminal
= Function Product & Document class
= Function ; Signal name    
= Funktion & Document class    
== Functional allocation ; Signal name    
== Functional allocation & Document class    
+ Point of installation & Document class    
++ Location & Document class    

The core of this new type of reference designation system RDS-PP is based on the interrelations between the individual designation blocks. In this way, both one-to-one identification of the technical objects according to various aspects and the referencing of the designations to designation blocks that have been identified in another aspect are possible.

This option gives the reference designation system an object-oriented character, unlike its predecessors, which is a major advantage in organization systems. In this context, assignment refers to the role relations between the unique designations of different aspects.

With the application of the reference designation system RDS-PP, the VGB guideline B101 and the IEC 81346-2 are the most important codes and standards. B101 was elaborated by a working panel of the professional association VGB PowerTech e.V. and contains the letter code of the breakdown level 1 for the designation blocks function, functional allocation, point of installation and location. In the so-called system key, the letter combinations consisting of three letters are defined with all the systems and system boundaries of a power plant.

Since the B101 guideline is based on a classification scheme for infrastructure objects (DIN EN 81346-2), this standard has a standardizing character. Breakdown level 2 in the blocks function, functional allocation, location, and point of installation, or both breakdown levels of the product designation are defined in national and international standards (national:DIN 81346-2; international:IEC 81346-2).

To help with the correct application of RDS-PP in practice, in December 2007 the VGB working panel published a collection of application explanations (VGB-B116). It contains various application scenarios and solutions for the identification of systems in power plants.