International telecommunication union

Reference Architecture of Smart Grid

Figure 2 represents a logical view of the smart grid system with a focus on communication interactions. The communications cloud represents the communications networks that connect logical devices in the smart grid. These communications networks may reside within a domain or cross-domain boundaries. The communications network may carry grid related data only or may be a general purpose network carrying grid data along with generic data. The choice of what type of network is needed to support a particular smart grid function shall be driven by the requirements of that function.

Figure 2: Reference Architecture of Smart Grid

Functional Architecture

7.1 Functional Model of Smart Grid

- Grid domain: power grid functions

- Smart metering: smart metering functions

- Customer domain: end-user functions

- Communication network: telecommunication, including IP-based, network functions

- Service provider domain: application functions

In addition, management/ security functions are required for all domains. Figure 3 shows relevant functions of Smart Grid and their relations between functions using a line with circles at the both ends.


Figure 3: Functional Model of Smart Grid
The Functional model shown in Figure 3 identifies the principle functional groups for Smart Grid, including the End-User Functions, the Application Functions, the Smart Metering Functions, the Energy Control Functions, the Power Grid Functions, the Network Functions, the Management Functions, and the Security Functions. Key functions within each functional group are shown within each box, and they summarize the Key Elements for Smart Grid discussed in the Overview document. The lines across the function boxes indicate data flows, and interactions between them.

The functions related to end users and end systems (e.g., power system devices) are shown on the left of Figure 3, while the core functions for smart grid, the Application Functions, the Network Functions, and the Energy Control Functions are shown in the middle column. A key focus of the smart grid, the Smart Metering Function is also shown in the middle. Two key function areas: (i) the Management and (ii) Security Functions have interaction with other functions and are shown on the right of Figure 3.

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  Power Grid Functions: This function group performs functions to efficiently and intelligently distribute energy and integrate distributed renewable energy generation and distribution. It interacts with Application and Energy Control Functions through Network Functions, and interacts with End-User Functions for energy transmission.
  
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  Network Functions: This function group interacts with all other function groups to provide functions such as Resilience and Recovery, QoS management, reliable data transport, metering data transfer, data aggregation, real-time data transfer, and others.
  

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  Resilience and Recovery Function: This function provides the capability of effectively preventing and responding to disruptions due to cyber attacks, physical phenomena, software and hardware failures, upgrades and human mistakes.
  

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  QoS Management Function: The QoS Management Function is used to guarantee the performance (e.g., bandwidth, end-to-end delay, jitter, and others). It provides the capabilities to differentiate and prioritize the data sent from a variety of devices (e.g., meters, appliances, substation, and others) thus enabling the delivery of information across the grid for different applications. QoS management differentiates operational data, non-operational data, and asynchronous events generated by the Smart Grid devices in reaction to physical activities. For example, QoS management will differentiate traffic related to DR signals and SCADA control sensing from the meter reading with other data traffic from non-critical applications.
  
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  Core Data Transport Function: This function provides secure and efficient network signalling and data transmission planes over a wide geographical area, enabling functionality related to the interaction, and data and information exchange between different function groups.
  

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  Smart Metering Functions: This function group encompasses the interaction with End-User Functions, Network Functions, Management Functions, and Security Functions groups. It performs functions to control and maintain metering equipment and to read meter data. It interacts with Application Functions group for establishing meter data base and billing information and interacts with Network Functions group for meter data aggregation and transportation; it may interact with End-User Functions through gateways and home networks. This function group also enables the real-time monitoring and protection via effective event or alarm reporting and processing.
  
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  Energy Control Functions: This function group performs functions to monitor and manage distributed energy resources and support services such as Plug-in Electric Vehicle (PEV) charging, and to manage energy capacity planning. It interacts with End-User Functions and Application Functions group through Network Functions.
  
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  End-user Functions: This function group consists of energy demand response, home/ building energy management and automation, local energy generation and storage, and PEV charging functions. It interacts with Demand Response (DR) application for dynamic pricing information, controls energy usage of home appliances and in-building equipments. It also interacts with Energy Control Functions for distribution capacity management and two-way energy transmission.
  
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  Application Functions: This function group consists of functions for application system information management (e.g., data syntax, semantic, and storage), customer information management (e.g., billing, user subscription), energy market and dynamic pricing as well as energy DR management and control. This function group interacts with End-User Functions, Smart-Metering Functions, Energy Control Functions, Management Functions, and Security Functions groups. This function may interact with End-User function, Energy control function and Power grid function to manage environmental parameters.
  

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  Management Functions: This function group consists of functions for management of systems in all function blocks. This function group interacts with all other function groups and covers various system management, including application management, device management, and network management, which are described below.
  

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  Application Management Function: This function provides the functions to help the operator to manage the key aspects of applications. It monitors various applications and helps application providers to ensure that their applications meet end-user’s expectations.
  
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  Device Management Function: This function enables the communication with a vast array of devices in the field and substations, whether heterogeneous or homogeneous. The device management provides an efficient way to normalize and transmit data to and from these devices.
  
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  Network Management Function: This function enables the diagnostics solution of network issues before the system actors are affected. It ensures that the network is available and runs as expected, so that the desired performance of network services can be achieved. Network Management Function is also responsible for keeping track of network resources and how they are assigned, configuring resources in the network to support a given service, and adjusting configuration parameters in the network for better quality. Data for network management is collected through a real-time two ways communication between Network Management Function and other functional groups.
  

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  Security Functions: This function group interacts with all other function groups in terms of physical security, system security, and operation security. This function group covers various security aspects and the examples of applications are described below:
  

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  Identification and Authentication Function: This function is the process of verifying the identity of a user, process, or a device, as a prerequisite for granting access to resources in a smart grid system.
  
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  Audit and Accountability Function: This function enables the review and the examination of the information record and activities related to smart grid to determine the adequacy of security requirements and to ensure compliance with the established security policy and procedures.
  
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  Access Control Function: This function ensures that only authorized personnel or users have access to use various utilities and services in the grid system.
  
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  Data Integrity Function: The function is responsible for data integrity in smart grid via cryptography and validation mechanisms.
  
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  Privacy Preserving Function: This function is designed to provide the privacy considerations with respect to the Smart Grid, including the examination of the rights, values, and interests of individuals, the related characteristics, descriptive information and labels, activities, opinions of individuals, and others.
  

A more detailed requirements and description of Security Functions can be found in NISTIR 7628 - Guidelines for Smart Grid Cyber Security [9].