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Communication infrastructure is the backbone of the communication system upon which various broadcasting and telecommunication services are operated. The infrastructure is the core component that connects upstream production, such as voice, data, and audiovisual services, with downstream consumers. In basic terms, communication infrastructure involves technology, products, and network connections that allow for the transmission of communications over large distances. According to [P2030 2011], the facilitation of Smart Grid consists of these following aspects: power engineering, communication technology, and information technology. A Smart Grid is characterized by the bidirectional connection of electricity and information flows to create an automated, widely distributed delivery network.

A communication infrastructure is an essential part to the success of the emerging Smart Grid [Yan 2013]. Through a communication infrastructure, a Smart Grid can improve power reliability and quality to eliminate electricity blackout.

As described in [Chen 2010], Smart Grid supports two‐way power flow and information flow to reach optimal electric power operation. Smart Grid shall consequently collect all kinds of information of electricity generation (centralized or distributed), consumption (instantaneous or predictive), storage (or conversion to energy in other forms), and distribution through the communication infrastructure. Then, the optimization of electricity utilization can be realized through appropriate information technology such as grid or cloud computing to allow appropriate actions in the entire Smart Grid through communication infrastructure again.

Communication infrastructure is a complex ecosystem of separate yet interconnected systems. It consists of a variety of networks, including the broader Internet, cellular networks, optical backhaul networks, and local area networks. A scalable and pervasive communication infrastructure is crucial in both construction and operation of a Smart Grid [Yan 2013].

For the purpose of planning and organization of the diverse, expanding collection of interconnected networks that will compose the Smart Grid, NIST adopted the approach of dividing the Smart Grid into seven logical domains, known as Smart Grid Conceptual Reference Model. The model includes the following domains [NIST SP1108r1]:

 Generation – Includes traditional generation sources and DERs; may also store energy for later distribution; generation includes coal, nuclear, and large‐scale hydrogeneration usually attached to transmission; DERs are associated with customer and distribution domains providing generation and storage and with service provider aggregated energy resources.

 Transmission – Carriers of bulk electricity over long distances; may also store and generate electricity.

 Distribution – Distributors of electricity to and from customers; may also store and generate electricity.

 Customers – End users of electricity (residential, commercial, and industrial); may also generate, store, and manage the use of energy.

 Operations – Managers of the movement of electricity.

 Markets – Operators and participants in electricity markets.

 Service providers – Organizations providing services to electrical customers and to utilities.

Figure 1.8 illustrates the interaction of roles in different Smart Grid domains through secure communication. It shows communications (blue lines) and energy/electricity flows (yellow lines) connecting each domain and how they are interrelated. Each individual conceptual domain is itself composed of important Smart Grid elements that are connected to each other through two‐ way communications and energy/electricity paths. These connections are the basis of the future, intelligent and dynamic power electricity grid.

Figure 1.8 NIST conceptual reference model.

Source: [NIST SP1108r1].

Public Domain.

Each domain and its subdomains encompass Smart Grid actors and applications (see description in Table 1.1). Actors include devices, systems, or programs that make decisions and exchange information necessary for performing applications; smart meters, solar generators, and control systems represent examples of devices and systems. Applications, on the other hand, are tasks performed by one or more actors within a domain. For example, corresponding applications may be home automation, solar energy generation and energy storage, and energy management (see more information in [NIST SP1108r3]). Appendix D includes more information about each domain including graphical representation of interactions with other domains.

Table 1.1 Domains and actors in the Smart Grid conceptual model.

Source: [NIST SP1108r1]. Public Domain.

	Domain	Roles/services in the domain
1	Customer	The end users of electricity. May also generate, store, and manage the use of energy. Traditionally, three customer types are discussed, each with its own domain: residential, commercial, and industrial
2	Markets	The operators and participants in electricity markets
3	Service providers	The organizations providing services to electrical customers and to utilities
4	Operations	The managers of the movement of electricity
5	Generation	The generators of electricity. May also store energy for later distribution. This domain includes traditional generation sources (traditionally referred to as generation) and distributed energy resources (DER). At a logical level, generation includes coal, nuclear, and large‐scale hydrogeneration usually attached to transmission. DER (at a logical level) is associated with customer and distribution domain provided generation and storage and with service provider aggregated energy resources
6	Transmission	The carriers of bulk electricity over long distances. May also store and generate electricity
7	Distribution	The distributors of electricity to and from customers. May also store and generate electricity

The Smart Grid Roadmap [NIST SP1108r1] describes the conceptual reference model as a tool for discussing the characteristics, uses, behavior, and other elements of Smart Grid domains and the relationships among these elements. The model is a tool for identifying the standards and protocols needed to ensure interoperability and cybersecurity and defining and developing architectures for systems and subsystems within the Smart Grid.

Interoperability of a Smart Grid is the ability of diverse systems to work together, use the compatible parts, exchange information or equipment from each other, and work cooperatively to perform tasks. It enables integration, effective cooperation, and two‐way communications among the many interconnected elements of the Smart Grid.

The viewpoint depicted in the diagram provides a high‐level, overarching logical architecture representation of a few major relationships that existing applications have to Smart Grid domains. This diagram suggests what their possible communication paths could be in a Smart Grid. It is also a useful way to identify potential intra‐ and inter‐domain interactions between existing and new applications, along with capabilities enabled by these interactions.

To enable the Smart Grid functionality, the actors in a particular domain often interact with actors in other domains. Actors are devices, systems, or programs that make decisions and exchange information necessary for executing applications within the Smart Grid. Actors have the capability to make decisions and to exchange information with other actors. Organizations may have actors in more than one domain. Figure 1.9 illustrates a composite view of actors within domains of the conceptual reference model.

Figure 1.9 View of the actors within domains of NIST conceptual reference model.

Source: [NISTIR 7628r1].

Public Domain.

Information about the actors associated with the NIST conceptual reference model is provided in [NISTIR 7628r1], [NIST SP1108r3]. Table 1.2 includes a list of selected actors and their description.

Table 1.2 Actor descriptions for the logical reference model.

Source: [NISTIR 7628r1]. Public Domain.

Actor no	Acronym	Actor	Actor description
1	DCS	Plant control system – distributed control system	A local control system at a bulk generation plant. This is sometimes called a distributed control system (DCS)
2		Customer	An entity that pays for electrical goods or services. A customer of a utility, including customers who provide more power than they consume
3		Customer appliances and equipment	A device or instrument designed to perform a specific function, especially an electrical device, such as a toaster, for household use. An electric appliance or machinery that may have the ability to be monitored, controlled, and/or displayed
4	DER	Distributed energy resources (customer generation and storage)	Energy generation resources, such as solar or wind, used to generate and store energy (located on a customer site) to interface to the controller (home area network/business area network [HAN/BAN]) to perform an energy‐related activity
5	EMS	Energy management system	An application service or device that communicates with devices in the home. The application service or device may have interfaces to the meter to read usage data or to the operations domain to get pricing or other information to make automated or manual decisions to control energy consumption more efficiently. The EMS may be a utility subscription service, a third‐party offered service, a consumer‐specified policy, a consumer‐owned device, or a manual control by the utility or consumer
6	PEV/EVSE	Plug‐in electric vehicle/electric vehicle service element	PEV is a vehicle propelled by an electric motor and powered by a rechargeable battery. It can be recharged using an external power source. When the external power source is the power grid, the EV is connected through the EVSE that provides power and communication
7	HAN Gateway	Home Area Network Gateway	An interface between the distribution, operations, service provider, and customer domains and the devices within the customer domain
8		Meter	Point‐of‐sale device used for the transfer of product and measuring usage from one domain/system to another
9		Customer Premise Display	A device that displays usage and cost data to the customer on location
11		Water/gas metering	A point‐of‐sale device used for the transfer of product (water and gas) and measuring usage from one domain/system to another
12		Distribution data collector	A data concentrator collecting data from multiple sources and modifying/transforming it
13		Distributed intelligence capabilities	Advanced automated/intelligence application that operates in a normally autonomous mode from the centralized control system to increase reliability and responsiveness
15	RTU/IED	Distribution remote terminal unit/intelligent electronic device	Receives data from sensors and power equipment and can issue control commands, such as tripping circuit breakers, if voltage, current, or frequency anomalies are identified, RTUs and/or IEDs can raise/lower voltage levels to maintain the desired voltage range
17	GIS	Geographic information system	A spatial asset management system that provides utilities with asset information and network connectivity for advanced applications
18		Distribution sensor	A device that measures a physical process and converts it into a signal that can be read by an observer or by an instrument
19		Energy Market Clearinghouse	Wide area energy market operation system providing high‐level market signals for distribution companies (ISO/RTO and utility operations)
21	AMI	Advanced metering infrastructure headend	This system manages the information exchanges between third‐party systems or systems not considered headend, such as the meter data management system (MDMS) and the AMI network
22		Bulk storage management	Provides management for energy storage connected to the bulk power system
23	CIS	Customer Information System	Enterprise‐wide software applications that allow companies to manage aspects of their relationship with a customer
25		Distributed generation and storage management	Distributed generation is the process of generating electricity from many small local energy sources. Storage management enables the efficient integration of distributed generation sources into the grid
27	DMS	Distribution management systems	A suite of application software that supports electric system operations. Example applications include topology processor, online three‐phase unbalanced distribution power flow, contingency analysis, study mode analysis, switch order management, short‐circuit analysis, Volt/VAR management, and loss analysis. These applications provide operations staff and engineering personnel additional information and tools to help accomplish their objectives
29	SCADA	Supervisory control and data acquisition	A supervisory computerized system that that gathers and processes data and applies operational controls for distribution side systems used to control dispersed assets
30	EMS	Energy management system	A system used by electric grid operators to monitor, control, and optimize the performance of the generation and/or transmission system
32	LMS/DRMS	Load management systems/demand response management system	An LMS issues load management commands to appliances or equipment at customer locations in order to decrease load during peak or emergency situations. The DRMS issues pricing or other signals to appliances and equipment at customer locations in order to request customers (or their preprogrammed systems) to decrease or increase their loads in response to the signals
33	MDMS	Meter data management system	System that stores meter data (e.g. energy usage, energy generation, meter logs, meter test results) and makes data available to authorized systems. This system is a component of the customer communication system. This may also be referred to as a billing meter
34		Metering/billing/utility back office	Back office utility systems for metering and billing
36		Outage management system	An OMS is a computer system used by operators of electric distribution systems to assist in outage identification and restoration of power. Major functions usually found in an OMS include: Listing all customers who have outages Prediction of location of fuse or breaker that opened upon failure Prioritizing restoration efforts and managing resources based upon criteria such as location of emergency facilities, size of outages, and duration of outages Providing information on extent of outages and number of customers impacted to management, media, and regulators Estimation of restoration time Management of crews assisting in restoration Calculation of crews required for restoration
39	WAMS	Wide area measurement system	Communication system that monitors all phase measurements and substation equipment over a large geographical base that can use visual modeling and other techniques to provide system information to power system operators
41		Aggregator/retail energy provider	Any marketer, broker, public agency, city, county, or special district that combines the loads of multiple end‐use customers in facilitating the sale and purchase of electric energy, transmission, and other services on behalf of these customers
42		Billing	An entity that performs the function of generating an invoice to obtain payment from the customer
43	ESP	Energy service provider	Provides retail electricity, natural gas, and clean energy options, along with energy efficiency products and services
44		Third party	A third party providing a business function outside of the utility
45	PMU	Phasor measurement unit	A device that measures the electrical parameters of an electricity grid with respect to universal time (UTC) such as phase angle, amplitude, and frequency to determine the state of the system
48		Security/network/system management	An entity that monitors and configure the security, network, and system devices

Figure 1.10 shows a high‐level view of information network and existing applications mapped to Smart Grid domains. An information network is a collection, or aggregation, of interconnected computers, communication devices, and other information and communication technologies. Technologies in a network exchange information and share resources.

Figure 1.10 Legacy application types within NIST conceptual domains.

Source: [NISTIR 7628].

Public Domain.

Smart Grid consists of many different types of networks, not all of which are shown in the diagram. The Smart Grid is a network of many systems and subsystems, as well as a network of networks. That is, many systems with various ownership and management boundaries are interconnected to provide end‐to‐end services between and among stakeholders as well as between and among intelligent devices.

The communication infrastructure includes different types of networks, technologies, and services that are organized based on criteria such as geography, topology, business purpose, technology, ownership, etc. Understanding these networks is crucial to perform analysis of requirements for security and quality of service considerations.

The networks include the enterprise bus that connects control center applications to markets and generators and with each other; wide area networks that connect geographically distant sites; field area networks that connect devices, such as intelligent electronic devices (IEDs) that control circuit breakers and transformers; and premises networks that include customer networks as well as utility networks within the customer domain. These networks may be implemented using public (e.g. the Internet) and nonpublic networks in combination. Both public and nonpublic networks require implementation and maintenance of appropriate security and access control to support the Smart Grid.

Given that the Smart Grid will not only be a system of systems but also a network of information networks, a thorough analysis of network and communications requirements for each network is needed. This analysis should differentiate among the requirements pertinent to different Smart Grid applications, actors, and domains.

Figure 1.11 illustrates a general architecture for Smart Grid communication infrastructure, which includes home area networks (HAN), business area networks (BAN), neighborhood area networks (NAN), data centers, and substation automation integration systems.

Figure 1.11 Smart Grid communication infrastructure.

Source: [Baimel 2016]. Licensed under CC BY 4.0.

As illustrated in this pictorial view, the authors of this work [Baimel 2016] summarize the communication infrastructure of the Smart Grid as based on three types of networks to include HAN, NAN, and WAN described as follows: