untitled INTERNATIONAL STANDARD IEC 61400 25 1 First edition 2006 12 Wind turbines – Part 25 1 Communications for monitoring and control of wind power plants – Overall description of principles and mo[.]
General
The IEC 61400-25 series aims to establish a standardized framework for manufacturer-independent communication in the monitoring and control of wind power plants It is essential for manufacturers and suppliers of wind power plant components to integrate the IEC 61400-25 series into their devices and systems.
Clause 5 provides a general overview of the context, models, modelling approach, and application possibilities of the IEC 61400-25 series
Subclause 5.2 offers an overview of wind power plants, detailing the applicability of the IEC 61400-25 series It clarifies the definition of a 'wind power plant,' distinguishes various operational concepts, and identifies the components essential for their operation.
Subclause 5.3 outlines the communication requirements essential for the monitoring and control of wind power plants It specifies the general communication capabilities that these plants must have, along with the necessary content and functions for effective communication.
Subclause 5.4 provides an overview of the communication model defined by the IEC 61400-
The IEC 61400-25 series establishes a foundational server-client communication environment for wind power plant monitoring and control This article briefly introduces three server-client application topologies, showcasing various possible communication architectures through examples Additionally, it outlines the three key areas defined by the IEC 61400-25 series, aimed at standardizing the monitoring and control processes in wind power plants for better understanding.
Top-down view on wind power plants
5.2.1 Definition of wind power plants
Wind power plants are comprehensive systems made up of various technical subsystems, each with distinct functions These subsystems, known as wind power plant components, will be detailed in section 5.2.2.
Wind power plant components are essential technical systems used in the operation of wind power plants, comprising various sub-components All these components are categorized under the IEC 61400 application area.
The information modelled in the IEC 61400-25 series covers the following corresponding components:
− meteorological conditions of the wind power plant
Wind power plant management system
− wind power plant grid connection
The wind turbine, along with its various sub-components, serves as the core element of a wind power plant, playing a crucial role in energy generation It harnesses the wind potential of a specific location to effectively convert wind energy into electrical power.
Wind turbine vendors typically provide guarantees regarding power curves and technical availability for energy production To allow operators and owners to validate the promised performance of their wind turbines, it is essential to have reliable data on the wind conditions specific to the installation site.
The IEC 61400-12-1 standard mandates the use of a reference met mast, or meteorological system, to measure wind conditions, such as wind speed, at specific locations This system provides essential data to correlate the power output of individual wind turbines with the available wind potential, enabling accurate assessments of a wind turbine's actual performance.
Integrated operation of wind energy systems involves not only multiple wind turbines but also additional components The energy generated at decentralized feeders and substations must be efficiently collected and delivered to end users through appropriate power networks, a responsibility managed by the electrical system.
NOTE All electrical system issues concerning substations are targeted in the scope of the IEC 61850 series
The wind power plant management system is essential for adapting the entire system to both static and dynamic conditions, as well as the requirements of the electrical power connection, including substations and utility networks.
Generic requirements on communication
Wind power plants are monitored and controlled by various external actors, such as local or remote SCADA systems, local real time build-in control systems, energy dispatch centres etc
The monitoring of wind power plants aims to provide essential information about the entire system and its components, serving as a crucial knowledge base for effective control For instance, a SCADA system must identify specific wind turbines within the integrated operation and understand their current status to halt their operation when necessary Additionally, the SCADA system needs to know which commands to send to the appropriate devices to ensure proper control of the components To verify the execution of these commands, feedback from the wind power plant is also required.
Wind power plants and external entities must fulfill a crucial requirement for effective monitoring and control: the ability to communicate with external systems.
Typically, any wind power plant component, which needs to exchange information with other components and actors, is therefore equipped with a so-called intelligent electronic device
An Intelligent Electronic Device (IED) facilitates data transmission to external receivers and receives data from external senders Typically, a wind turbine is equipped with a wind turbine controller that oversees the internal monitoring and control of the wind power plant components while also enabling external monitoring and control capabilities.
Information serves as the core of communication in monitoring and control systems It is derived from raw data collected from wind power plant components, which is then processed into specific information in accordance with IEC 61400 standards.
25 series There are five types of information that can be differentiated and are important for the monitoring and control of wind power plants:
Monitoring and controlling wind power plants relies on essential process, statistical, and historical information communicated by the plants themselves Process information reveals the behavior and current states of complete systems and their components Statistical data is valuable for assessing the operational efficiency of wind power plants, while historical information enables the tracking of operational trends through logs and reports.
Control information is essential for managing wind power plants, encompassing access profiles, set points, parameters, and commands This information is initially communicated to the plants by designated actors Wind power plants are responsible for storing this control information and facilitating its communication to sub-processes.
Descriptive information is the type and the accuracy of the information, as well as the time and the data description
Effective communication among stakeholders for monitoring and controlling wind power plants necessitates specialized functions to configure, execute, and oversee information exchange These functions can be categorized into two primary groups.
Operational functions, whether manual or automatic, enable users to gather information about wind power plants and transmit control instructions to them These functions play a crucial role in the management and optimization of wind energy systems.
Table 1 provides an overview of the ranges of application of the operational functions
Operational functions Range of application (practical use)
Monitoring operational functions enable local or remote observation of systems or processes to detect any changes over time This term also encompasses the observation of the behavior of individual data values or groups of data values.
Control Changing and modifying, intervening, switching, controlling, parameterisation, optimising of wind power plants
Data retrieval Collecting of wind power plant data
Logging Logging is a function intended for sequential recording of data and events in chronological order The result of the logging is a log
Reporting The reporting is a function intended to transfer data from a server to a client, initiated by a server application process
Management functions are essential for overseeing information exchange at higher levels They enable stakeholders to maintain the integrity of monitoring and control processes Key management functions play a crucial role in this framework.
Table 2 provides an overview of the ranges of application of the management functions
Management functions Range of application (practical use)
User/access management Setting up, modifying, deleting users (administratively), assigning access rights (administratively), monitoring access Time synchronisation Synchronisation of devices within a communication system
Diagnostics (self-monitoring) This function is used to set up and provide for self-monitoring of the communication system
System setup functions Defining how the information exchange will take place; setting, changing and receiving (retrieval) of system setup data.
Communication model of the IEC 61400-25 series
The IEC 61400-25 series establishes a communication model for effectively monitoring and controlling wind power plants, addressing all communication-related requirements at an abstract level This model is divided into three distinct areas, each defined separately.
– mapping of the information model and the information exchange model to standard communication profiles
The communication model operates within an abstract environment where two entities, the server and the client, interact through a shared communication channel The server acts as the provider of information and services, delivering the necessary content and functions to the client Meanwhile, the client serves as the user, holding specific rights to utilize and manage the server's resources.
The IEC 61400-25 series provides flexibility in the implementation of servers within physical devices Its primary goal is to ensure that information related to individual components of a wind power plant, such as wind turbines, is accessible via a designated logical device Additionally, the series does not dictate the distribution of objects within the wind power plant information model across servers.
The wind power plant information model facilitates essential data exchange for monitoring and control between the client and server, as illustrated in Figure 2.
Figure 2 – Data processing by the server (conceptual)
The model serves as a standard framework for interpreting data from wind power plants, enabling the server to process this information for external monitoring and control It transforms the data into relevant, semantically standardized information and provides clients with access to this data in a component-oriented format.
In creating the information model for wind power plants, an object-oriented paradigm has been utilized, enabling the representation of wind power plants as information objects and facilitating the design of a suitable information architecture.
Clause 6 describes in detail the logical structure of the wind power plant information model and the method by which wind power plants shall be modelled as information objects
The IEC 61400-25 series employs object modeling to effectively represent the systems and components of wind power plants for communication purposes This approach identifies real-world components as objects that encompass data, including analog values, binary statuses, commands, and set points These objects and their associated data are then mapped into a generic, logical representation, forming a comprehensive information model for wind power plants.
To create a model of a real-world component, it is essential to decompose it into individual objects, each representing specific data and functionality Every piece of data is assigned a name and categorized as either a simple or complex type (class), reflecting the information within the device that can be accessed or modified.
An object-modelling approach allows for the organization and definition of standard names for equipment features, such as a shaft's rotational speed, regardless of the manufacturer This standardization ensures that the same terminology is used across different vendors, enabling any client program familiar with the information model to access and interpret the data consistently.
The device offers various functionalities beyond reading and updating process information, including historical logs, report by exception capabilities, and actions triggered by both internal and external command and control inputs.
Information exchange model (get, set, report, log, control, publish / subscribe, …) defined in IEC 61400-25-4
Information exchange model (get, set, report, log, control, publish / subscribe, etc.) defined in IEC 61400-25-3
Wind power plant information model (roto speed, break status, total power production, …) defined in IEC 6140-25-200/300
Wind power plant information model ( rotor speed, break status, total power production, etc.) defined in IEC 61400-25-2
Wind power plant component e.g wind turbine
Information and services according to the IEC 61400-25 series
All of these items imply some type of information exchange between the outside world and the real world device represented by the wind power plant information model
5.4.3 Information exchange model and relation to wind power plant information models
The information exchange mechanisms rely on standardised wind power information models
The IEC 61400-25 series is centered around information models and modeling methods that accurately represent real components, as illustrated in the conceptual overview This series defines all information available for exchange between components, offering a comprehensive model that reflects the actual wind power plant automation system, including elements such as the power system process and generators.
Hi d es/ e n ca p s u lat es real w o rl d
IEC 61400-25 logical node (Rotor) IEC 61400-25
Real component in wind turbine
The IEC 61400-25 series outlines information exchange standards that are independent of specific implementations, utilizing abstract models It incorporates the concept of virtualization, which highlights the relevant aspects of real devices necessary for effective communication with other devices The series specifies only the essential details required to ensure interoperability among devices.
The IEC 61400-25 series adopts a method of breaking down functions into the smallest entities for effective information exchange This granularity is achieved through a thoughtful distribution of these entities to dedicated devices known as Intelligent Electronic Devices (IEDs) These entities are referred to as logical nodes, exemplified by a virtual representation of a rotor class, which is identified by a standardized class name.
WROT) The logical nodes are modelled and defined from the conceptual application point of view Logical nodes are collected in a logical device representing for example a complete wind turbine
The real components depicted on the right side of Figure 3 are integrated into a virtual model at the center of the figure The logical nodes in this model correspond to the functions of actual physical devices, with the logical node WROT specifically representing a rotor of the turbine shown to the right.
A logical node in wind power plant systems comprises a structured list of data, such as rotor speed, along with specific information This data is semantically defined, ensuring clarity in its context The information is exchanged through services that adhere to established information exchange protocols.
The logical nodes and the data contained are crucial for the information model and the information exchange services for wind turbines to reach interoperability
The logical nodes and the data contained are configured by the control information, for example parameters, commands to be accepted, set point ranges, etc
General
This clause provides a detailed description regarding the wind power plant information model Common wind power plant relevant information is defined, structured and described unambiguously from viewpoint of object orientation
Subclause 6.2 describes the modelling methodology used to represent and structure relevant information
IEC 61400-25-2 establishes logical nodes for organizing related information and outlines common data classes that serve as foundational elements containing specific properties relevant to wind power plants Additionally, this section includes common data classes derived from IEC 61850-7-3.
Information modelling methodology
For modeling purposes, information can include LNs, data, or data attributes Data comprises various attributes such as the value of a measurand, state, or setpoint, along with accompanying details like name, time, quality, accuracy, and unit.
A wind power plant generates various types of information, including source data and additional insights derived from wind turbine controllers, such as 10-minute averages, alarms, logs, counters, and timers This valuable data is stored locally for future analysis The relationships between these information categories are outlined in Table 3, with definitions aligned with the IEC 61400-25 series.
Table 3 – Wind power plant information categories
State information refers to discrete details about the current condition or behavior of a component or system The status indicates the specific condition of a component or system, represented as st1, st2, , stn An alarm signifies a safety intervention, often initiated by the turbine control system An event represents a state transition, which can include changes in status, alarms, or commands.
Analogue information refers to continuous data that reflects the current state or behavior of a component or system Sampled data represents the measured value of a specific process quantity Processed data is the measured value that has undergone processing, such as a 10-minute average Additionally, three-phase data pertains to the measured value of a three-phase electric power quantity.
Control information refers to discrete data about the current state or behavior of a component or system Command indicates the controllable status of system behavior, such as enabling or disabling functions A set point is the reference value for a specific process quantity.
Parameter Controllable value for system behaviour (adjustment)
Statistical information The result of applying a statistical algorithm to a set of data
Timing data refers to the total duration of a specific state, while counting data indicates the total number of occurrences of a particular event Characteristic data encompasses the properties of the observed information, including minimum, maximum, average, and standard deviation Additionally, historical information provides insights into the time elapsed.
Log Chronological list of events for a specific period of time
Transient log Event triggered chronological list of high resolution source information for a short period of time
Report Periodical notification comprising the information that represent the state and data requested in the report control block
The IEC 61400-25 series establishes a comprehensive information model for wind power plants, accommodating various formats and properties as outlined in Table 3 This hierarchical model follows the top-down approach defined in IEC 61850-7-1 Clause 6, with foundational principles described in IEC 61850-7-2:2003, Clause 5 The hierarchical structure categorizes common information into distinct classes, allowing lower-level classes to inherit properties from their upper-level counterparts A concise representation of the wind power plant information model is illustrated in Figure 4, with each level to be explored in greater detail.
Logical Device (LD) Logical Device (LD)
Logical node (LN) Data class
Figure 4 – Structure of wind power plant information model
The highest level is called Logical Device (LD), which is decomposed into Logical Nodes (LN)
A logical node is made up of related data, known as data classes (DC), which inherit properties from a designated Common Data Class (CDC) Each common data class comprises a set of data records, and the fundamental details of the data are defined by the type-definition of the common data class.
A server hosts at least one logical device, which can be assigned to a specific wind turbine in a wind power plant using the IEC 61400-25 series Each logical device comprises a collection of logical nodes associated with that wind turbine The logical node zero (LLN0) provides essential information about the logical device, such as its nameplate and health, while the logical node physical device (LPHD) conveys common data regarding the physical device hosting the logical device, including its nameplate and health status.
In a logical device, wind turbine information is organized into distinct 'containers' known as logical nodes The IEC 61400-25 series outlines specific logical node classes for wind power plants, as detailed in IEC 61400-25-2, with certain classes designated as mandatory (marked with an 'M') and others as optional (marked with an 'O') The fundamental guidelines for utilizing Logical Nodes and Data classes, along with their extensions, are specified in the Annex.
IEC 61850-7-4 and Clause 14 of IEC 61850-7-1 define specific logical nodes (LNs) that are derived from the physical components of a turbine, such as the rotor, transmission, generator, and yaw system Additionally, common information collections, like alarm and event logs, can also be represented as specific LNs It is essential that the names of these wind power plant-specific logical nodes are unique and start with the letter 'W', followed by three capital letters that indicate their content.
The Logical Node data is characterized by named attributes that can be either simple types, like a 32-bit integer, or complex structures composed of various named simple and complex components In early wind power plant communications, this data was represented in a linear, memory-mapped address space with uniform data types However, the current model allows for named data with appropriate types that accurately reflect the underlying information, while the internal organization and implementation of data storage remain independent of external perspectives.
In a logical node (LN), information is organized through data classes, all of which share a standardized table structure, as illustrated in Table 4 This table effectively represents and visualizes the various attributes of data classes within a logical node.
Table 4 – General table structure of a logical node (LN)
Attribute name Attribute type Explanation M/O
Data class name CDC Description and range
Data class name CDC Description and range
Data class name CDC Description and range
Data class name CDC Description and range
For the sake of convenience, all information in a logical node is categorised in compliance with the wind power plant information decomposition of Table 3
In Table 5 all data class attributes inside a logical node are explained briefly
Table 5 – Data class attributes in a logical node
Attribute Name Name of the data class
Attribute Type Common data class that defines common data properties The CDCs are defined in IEC 61400-25-3 Explanation Short explanation of the content of the data class Mandate M: Mandatory, O: Optional
If an optional logical node is used, its mandatory (M) data class attributes shall also be used
Optional (O) defined data class attributes are instantiated as needed by the user
7 Wind power plant information exchange model
General
Clause 7 outlines the information exchange models that clients and servers can utilize to access the content and structure of the wind power plant information model specified in Clause 6.
Information exchange modelling methodology
7.2.1 Wind power plant information exchange
The wind power plant information exchange model outlined in IEC 61400-25-3 aims to facilitate the exchange of information from the instantiated information model across various classes, including Logical Nodes, Data, DataAttributes, and control blocks This model defines a server that delivers essential information for effective communication and management within wind power systems.
– an instance of the wind power plant information model, and
– required functions including the associated services (Get, Set, Control, Query, Report, etc.) which enable a client to access the instantiated information model
The IEC 61400-25 series defines the server role only A client issues service requests to the server, by sending request messages, and receives response messages or reports from the server
A server provides access to its wind power plant information model instance for multiple clients, as illustrated in Figure 5 Each client can, independently of other clients, communicate with the server
Figure 5 – Client and server role
As shown in Figure 5, physical devices may implement the client, the server role, or both roles
The client plays the complementary role of the server with regard to the services
The IEC 61400-25 series does not specify any application program interface for either the server or the client Instead, it outlines the externally visible representation of the information stored in the server and details the methods for transmitting and receiving this information.
The wind power plant information model in the server supports the access services as depicted in Figure 6
Reporting/Logging Get/Set responses
The server is dedicated to delivering data that constitutes the wind power plant information model, with data attributes that facilitate information exchange The Information Exchange Model (IEM) offers essential services for this purpose.
– control of external operational devices or internal device functions,
– monitoring of both process and processed data, and
– management of devices as well as retrieving the wind power plant information model
The server hosts data instances of the wind power plant information model, which can be accessed through the Get, Set, and Control services for prompt actions, including retrieving information, setting data values, and controlling devices or functions.
Reporting and logging enable the automatic transmission of information from the server to the client in response to internal server events (reporting) and facilitate the storage of this information on the server for future access (logging).
The Abstract Communication Service Interface (ACSI) encompasses the fundamental services utilized by the communications interface to facilitate information exchange between external sources and various components of real-world devices Detailed methodologies for these services are outlined in IEC 61850-7-1 and 61850-7-2, with Table 6 of IEC 61850-7-1 specifically detailing the ACSI models and services This article further explores the application of these services within the context of wind power plants.
Figure 7 visually represents the different elements of the ACSI models, offering a narrative that describes the interaction of a typical device with external services.
Report control block values on change, event, periodic
Subscribe values on change, event, periodic
Report bidirectional information exchange unidirectional information exchange
Figure 7 – Conceptual information exchange model for a wind power plant
A server is a physical device equipped with a communications interface, identifiable by its network address, and accessible to external clients over a network It can handle connections from multiple clients, authenticate them, and deliver various services to provide information Within the server, there are one or more logical devices, each containing logical nodes that serve as fundamental building blocks for different functionalities These logical nodes manage data that can be individually or collectively accessed, respond to control inputs, generate both solicited and unsolicited reports, and maintain queryable logs This versatile representation effectively models any real-world physical device with a communications interface, showcasing its powerful service capabilities.
Get/Set and Control services enable the reading (get) and writing (set) of data within the Logical Node Typically, analogue and status information is read-only, while control and configuration data can be both read and written These services support concepts like "select before operate" for control applications.
Data Sets allow for the organization of individually named data into defined collections, which can be created, deleted, and listed through various services This functionality enables client applications to group commonly needed data attributes, facilitating retrieval with a single get operation using a unique name.
Data Sets play a crucial role in the information exchange mechanisms of a Logical Node, specifically in reporting and logging Most physical devices incorporate internal logging systems that capture periodic data recordings, changes in data values, or instances when values exceed certain thresholds Additionally, these devices can send reports to subscribed clients under similar conditions as those used for logging In ACSI models, the information logged or reported is encapsulated within a Data Set, allowing for a more compact and efficient definition of logging and reporting rules.
The Log Control Block (LCB) and Report Control Block (RCB) establish the rules for logging and reporting, respectively Each log is linked to an LCB, while each report corresponds to an RCB, which specifies the criteria for data inclusion This system allows for a robust and adaptable method of managing logging and reporting information.
Logs play a crucial role in physical devices, serving either as the primary function, such as in condition monitoring devices, or for diagnostic purposes They consist of time-ordered data collections organized into specific Data Sets External clients can access this information through services that allow them to query the logs using filters to define a relevant time range and select specific attributes for retrieval.
Clients can subscribe to predefined reports through our services, ensuring that even if communication is temporarily interrupted, all reports will be sent once the connection is restored.
This overview highlights the essential information exchange functionalities of a physical device through the ACSI approach For a comprehensive understanding of ACSI, please consult IEC 61850-7-1 and IEC 61850-7-2.
The services are generally defined by:
– a set of rules for the definition of messages so that receivers can unambiguously understand messages sent from a peer,
– the service request parameters as well as results and errors that may be returned to the service caller, and
– an agreed-on action to be executed by the service (which may or may not have an impact on process)
This basic concept of the IEM is depicted in Figure 8
(e.g., ‘rotor speed’) that can be retrieved
‘enable reporting’) that can be set action action t
Get.req
Set.req
Figure 8 – IEM service model with examples
General
The Specific Communication Service Mapping (SCSM) outlines the relationship between various services and models—such as servers, logical devices, logical nodes, data sets, report controls, log controls, and setting groups—and their corresponding communication stacks, ultimately creating a comprehensive profile.
The mappings and the used application layer define the syntax (concrete encoding) for the data exchanged over the network
NOTE The concept of the SCSM has been introduced to be independent from communication stacks including application protocols
The SCSM effectively translates abstract communication services, objects, and parameters into specific application layers that deliver concrete coding The complexity of these mappings varies based on the communication network technology, and not all ACSI services may be supported across every mapping However, when a service is available in a mapping, it retains the same meaning as in the benchmark mapping Additionally, an application layer can utilize one or multiple stacks, ranging from layer 1 to layer 6.
The service 'GetDataSetValues' allows for the retrieval of multiple values in a single request, and its mappings can vary from AL1 to ALn For instance, one specific AL may directly support this service, while another may have a different level of support.
Get of single values or many values of the same type only In this case, the mapping has to issue several Gets
Network independent interface (ACSI, Abstract Communication Service Interface)
Figure 10 – ACSI mapping to communication stacks/profiles
Architecture of the mappings
Multiple mappings may be supported by the IEC 61400-25 series The conceptual architecture of the mappings is shown in Figure 11
Presentation Session Transport Network Data Link Physical
Mapping 3 Mapping n out of scope out of scope
C om m un ic at io n pr of ile A
C om m un ic at io n pr of ile B
C om m un ic at io n pr of ile C
C om m un ic at io n pr of ile X
Mapping to communication profile: IEC 61400-25-4
The mapping of information models and information exchange models to suitable protocols is outlined in IEC 61400-25-4 It specifies that TCP and IP must serve as the foundational lower layer protocols for all mappings, while details regarding specific data link and physical layers are not covered within the IEC 61400-25 series.
Mapping of the wind power plant information model
The mapping of the wind power plant information models to a hierarchical structure as defined in Clause 6 and Clause 7 of IEC 61400-25-2, shall be applied for all SCSMs of the IEC 61400-
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