Chapter 6 Role of PLC Technology in Smart Grid Communication Networks

Although the demand for electric power is increasingly changing, the dimensioning and specifications of electric power systems are greatly influenced by statistical studies and historical profiles of energy demand. The biggest part of the power grid was engineered several decades ago based on the operational conditions and the technological options of that time. Since then, decisive changes in both the size and profile of electricity demand have taken place that necessitate the upgrading of major operational modules or parts of the equipment and, also, changes in the switching functionalities of the power grid with regard to load redistribution and balancing. These important issues can be addressed either by applying proper strategies to manage power demand or by appropriately incorporating distributed energy resources (DERs). Furthermore, the mandatory use of smart energy meters combined with flexible pricing tools can mitigate the cost of congestion by limiting the peak load where the electric energy is delivered. At the same time, demand control from the consumption side should be enabled. According to the European Union’s 20-20-20 smart grid (SG) target toward the low-carbon economy, a 20% reduction in CO₂emissions, an increase of the share of renewable sources to 20%, and 20% lower energy consumption are the targets for 2020 [1].

Thus, a major challenge for utilities is to provide reliable and efficient SG services that will enable seamless integration of DERs and support of smart metering applications, while enhancing power quality through sophisticated distribution automation (DA) services. The SG constitutes the modern approach to monitoring and controlling the power grid. As such, the SG can be regarded as an information and communication technology (ICT)-enhanced electric power network, which can intelligently integrate/incorporate the actions of all related stakeholders, namely, the generators, distributors, and consumers of energy. As the main target of the SG is to deliver electrical power in a sustainable, economical, and secure way, the development of reliable and efficient data transmission schemes is imperative.

Recent developments in SG communications (SGCs) technologies address the crucial objectives of reliability, state awareness, and financial viability of the SG stakeholders, producers/operators/customers, and society as a whole. These technologies employ wireless and wired options that are usually integrated and operate interchangeably to form hybrid communications platforms that serve the SG. The SGC networks (SGNs) support the two-way transfer of SG data employing a wide range of telecommunication technologies. Indicative examples encountered in SG implementations are cellular technologies [2], power line communication (PLC) options [3], Wi-Fi [4], and optical technology [5]. The resulting hybrid communications platform, usually consisting of multiple, sometimes superposed, networks, should have sufficient capacity to accommodate the quality of service (QoS)-enabled SG traffic and guarantee an all-Internet protocol (IP), secure, two-way, end-to-end transfer of the SG data.

A critical question concerning SGCs is which transmission medium should be employed each time. As the SG is composed of a variety of constituent networks, namely, high-speed enterprise networks, field area networks (FANs), substation networks (SNs), and customer premises networks (CPNs), the answer is not unique. The present chapter explores the role of the PLC transmission medium in the hybrid communications platform employed by SGNs and proposes relevant techniques. The recently standardized broadband over power lines (BB-PLC) networks [6,7] aim at effectively serving QoS-enabled traffic. The ubiquitous presence of the power grid, along with the easy and scalable deployment of the PLC SGNs over the power grid [8], renders BB-PLC the only broadband access technology readily available to remote or rural areas [9]. The above considerations, together with the independence of utilities from a third-party communications provider, render PLC technology a very promising SG option, especially in the medium-voltage (MV) grid.

The rest of the chapter is organized as follows. In Section 6.2, SG networks are outlined, considering the relevant energy, communications, and information technology (IT) aspects. In Section 6.3, the perspectives of SGCs are analyzed and the role of the PLC is examined in the framework of the various networking options arising in SGNs. In Section 6.4, PLC transmission techniques are examined in their attempt to handle QoS-enabled SG data. The relevant design guidelines are given in Section 6.5. Finally, conclusions are drawn in Section 6.6.

6.2 OVERVIEW OF SMART GRID NETWORKS

There have been several attempts in the literature to present the fundamental elements of SGs from various aspects. The authors in [10] present the systems constituting the SG, namely, the smart infrastructure system, the smart management system, and the smart protection system. The authors in [11,12,13] follow the National Institute of Standards and Technology (NIST) conceptual model [14], depicted in Figure 6.1. Also, the authors in [15] consider SGs from the IT perspective, presenting reference models related to the application layer. Finally, a layered approach is proposed in [16,17]. This section adopts the Institute of Electrical and Electronics Engineers (IEEE) 2030 [18] interoperability reference model to classify the SGs under three perspectives, namely, (i) the energy perspective, (ii) the communications perspective, and (iii) the IT perspective, and presents the related fundamental applications/services.

FIGURE 6.1 NIST conceptual model of the smart grid. (National Institute of Standards and Technology, NIST framework and roadmap for smart grid interoperability standards, release 1.0, January 2010. Available at: http://www.nist.gov/public_affairs/releases/upload/smartgrid_interoperability_final.pdf [accessed March 2013.)

6.2.1 ENERGY-RELATED APPLICATIONS/SERVICES

As depicted in Figure 6.1, systems interconnected over the power grid include bulk generation, the transmission and distribution networks, and the customer premises. The seamless integration of such entities requires a reliable, two-way flow of both electric power and information. The following challenges should be addressed:

• Bulk generation: A successful power grid operation depends strongly on the equilibrium between energy production and energy consumption. The main challenge on the power generation side is to incorporate intermittent DERs to increase microgrid penetration and enhance the sustainability of the power grid. However, the generation of DERs exhibits severe fluctuations that prohibit their seamless integration into the power grid [19] and disrupt the equilibrium between energy generation and consumption. It is expected that the formulation of appropriate prediction models will significantly increase the reliability of DERs and, consequently, their use in generation.

• Transmission and DA: To increase power quality and redundancy, the smart infrastructure should enable DA services employing sensors and actuators throughout the grid to monitor power production and energy demand and detect faults and component failures. Also, though the substations are already supported by supervisory control and data acquisition (SCADA) automation services, there is still the need to incorporate digital devices that monitor and control the operation of the power grid in an autonomous way.

• Customer premises: The end users can interact with the SG in various ways. First, real-time monitoring of power consumption is enabled through automatic meter reading/advanced metering infrastructure (AMR/AMI) systems. The operator of the power grid provides demand-response (DR) applications for both direct and indirect load control, where demand-side management (DSM) applications notify the customers about excessive energy demand and provide incentives to reduce consumption in an attempt to reduce peak load. Moreover, SG customers are potential prosumers; that is, they not only consume but may also produce energy. In addition to DERs, new load paradigms such as plug-in hybrid electric vehicles (PHEVs) [20] are present in the SG, as PHEVs consume energy while charging and return energy to the power grid when they are fully charged [10].

6.2.2 APPLICATIONS/SERVICES RELATED TO SMART GRID COMMUNICATIONS

From the SGC point of view, a variety of access technologies and protocols should be engaged to support a two-way information flow to/from the entities appearing in Figure 6.1. In Figure 6.2, the reference communications model for the SG defined in the IEEE 2030 standard [18] shows how SGNs act as an intermediate layer between the power grid and the network management layer. As shown in Figure 6.2, multiple networks are employed to support the various QoS requirements of SG services. Specifically, the SG services are associated with the following types of networks:

FIGURE 6.2 The IEEE 2030-2011 smart grid communication layered model. (IEEE guide for smart grid interoperability of energy technology and information technology operation with the electric power system [EPS], end-use applications, and loads, IEEE Std 2030-2011, pp. 1–126, 10 September 2011.)

• CPNs: CPNs vary according to their size and to the number of serving devices and can be classified into home area networks (HANs), building area networks (BANs), and industrial area networks (IANs). Regardless of the CPN type, local area network (LAN) technologies are used to provide connectivity within CPNs that are employed to support applications such as AMR, remote load control, monitoring and control of DERs, energy consumption management through DSM, and charging of PHEVs.

• Neighborhood area networks (NANs): NANs are employed to collect information generated by CPNs. Usually, a NAN comprises the AMI installed to collect the AMR data. NANs constitute the last mile of the SGNs, as they are intermediate between the customer and the distribution grid. The significant components of NANs are their distribution access points (DAPs) operating as gateways for the traffic collected via the AMI. The DAPs decide on data aggregation and routing, based on the type and significance of the transferred SG traffic.

• FANs: FANs are deployed over the distribution grid to monitor and control various field devices, such as insulators, feeders, and transformers. These devices are dispersed over the grid to enable DA services and services related to the seamless integration and management of DERs. As FANs cover the whole distribution grid, they may also serve for utilities communications, offering communication and monitoring services to the technical personnel responsible for grid maintenance and day-to-day operation.

• SNs: SNs are highly reliable enterprise LANs used for protection, monitoring, and automation services. Among them, SG protection and SCADA services require a maximum delay of 10 ms [21]. Hence, to meet the QoS requirements of teleprotection services, SNs must usually have a one-hop point-to-point link to the utility operations and control center.

Table 6.1 provides an overview of the available transmission media along with their advantages and disadvantages. The options tabulated in Table 6.1 may be employed in different segments of SGNs.

6.2.3 IT APPLICATIONS/SERVICES

The IT applications involved in the SG primarily support the management and control of various procedures and devices dispersed over the grid. The data related to SG operation come from a plethora of sources either internal or external to the grid. Internal sources include: (i) devices for substation monitoring, (ii) smart units attached to various grid nodes such as AMR devices and smart sensors, and (iii) databases employed by the utilities as well as information originating from human intervention. Next, the applications and services supported by various segments of the grid are presented:

• Bulk generation: Applications related to the management of DER generation are supported. Also, generation scheduling is enabled and relevant data are sent to the various stakeholders of the electric energy market.

• Transmission and distribution grids: Data acquisition and collection from devices installed both in the field and in substations are supported all over the SG. An overview of various QoS requirements for SCADA automation applications can be found in [21,22,23] and in the IEEE standard for substation automation, IEEE 1646 [24]. Also, maintenance and day-to-day activities that process data collected by geographic information services are performed to guarantee power availability. Regarding the distribution grid, applications related to DER management and integration are offered. Finally, parts of the grid that connect end users should support data aggregation for better collection and management of billing data.

• Customer applications/services: Applications related to the seamless integration of DERs must be provided. Also, various energy management systems and home automation applications may offer real-time monitoring of energy consumption. Finally, applications accessed through portals may provide data and services related to energy usage, billing, and customer authorizations.

TABLE 6.1
Smart Grid communications Media overview

Network Access Technology	Data Rates (Maximum Values)	Advantages	Disadvantages
Cellular networks	GPRS	Widely adopted for	Offers only periodic
(GPRS/3G/4G)	56–115 Kbps	certain types of smart	service monitoring
	3G	grid applications	Dependence on third
	2 Mbps		parties
	4G
	50–100 Mbps
Wi-Fi (IEEE	~100 Mbps	Easy installation	Limited scalability and
802.11)		Reduced cost	reliability
Ethernet	100 Mbps-10 Gbps	Easy installation	Limited scalability
		Reduced cost
WiMAX (IEEE	WiMAX (8062.16 m)	Wide coverage	Cost related to leasing
802.16) and LTE	300 Mbps	Scalability	spectrum
	LTE
	100 Mbps
Fiber optics	40–1600 Gbps (when	High capacity	High cost
(SONET/SDH	WDM is employed)	Reliability	Not available in rural
E/GPON)		Security	areas
DSL	20 Mbps	Easy installation	Public access network
		Scalability
PLC (NB/BB/	BB-PLC	The transmission medium	Nonuniversal legislation
BPL)	500 Mbps on CPNs	already exists	Adverse transmission
		Third-party independence	medium
WSN/WPAN	ZigBee	Reliability	Short coverage
(IEEE 802.15.4	250 Kbps	Low delay
ZigBee,	DASH7
DASH7)	200 Kbps

6.3 ROLE OF PLC IN THE SMART GRID COMMUNICATIONS INFRASTRUCTURE

Although various communication options are available to support SGC, PLC is preferable on many occasions for the following reasons:

• The deployment of the PLC segments of hybrid SGC solutions is immediate, simple, and scalable.

• As far as the PLC segments of SGNs are concerned, data security officers (DSOs) do not have to procure telecommunication services from third parties.

• The privacy and independent processing of SG data are guaranteed, as the DSOs are the owners of the PLC part of SGNs.

• As PLC technology employs the power lines themselves as the physical transmission medium, it is the only SGC option that offers monitoring of the operational status of the electric grid by appropriately processing inherent noise patterns and spurious signals collected by the PLC nodes.

• Alternative technologies to PLC can serve only part of the desired applications, especially in the MV SG. In any case, the PLC nodes may usually embed any related technology in order to (i) increase their functional and communication capabilities and (ii) provide compatibility with alternative communication options or existing or future automation technologies.

• Direct and selective scalable integration of all application requirements of the SG can be implemented at the level of the grid nodes.

The rest of the section explores the role of the PLC in SGNs of the SG.

6.3.1 PLC IN CPNS

The CPNs constitute a multiprotocol, multivendor environment [18], in which many technologies are involved, with PLC and Wi-Fi being the most mature. Other solutions intended for the SG employ Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS) and ZigBee technologies. An overview of the communication technologies used in CPNs, along with their respective level of maturity, is presented in Table 6.2 [25].

In most cases, BB-PLC seems preferable to narrowband (NB)-PLC as it may provide a variety of broadband applications requiring fast Internet access. NB-PLC may be the solution for transferring low-rate data over large distances along the MV grid in remote areas. The main efforts to standardize BB-PLC access resulted in the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) G.hn [7] and IEEE 1901 [6] protocols summarized in Table 6.3. The operational principles of the two standards are presented in [26,27,28,29,30]. The large amount of traffic moving through an SGN, along with the necessity to prioritize data with regard to their importance and/or bandwidth requirements, renders the time division multiple access (TDMA) contention-free medium access control (MAC) option preferable to the carrier sense multiple access (CSMA) contention-based option when reliable SG services are required. On the other hand, noncritical broadband services employ contention-based access.

TABLE 6.2
Communication Technologies Employed in cPNs

Communication Technologies	HAN	IAN	AMR	PHEV
PLC	√	√	√	Δ
ZigBee	√	√	√	Δ
Wi-Fi	√	√	√	Δ
WiMax	~	~	Δ	~
GSM/GPRS	√	√	√	√
DASH7	Δ	Δ	Δ	Δ

Source: Usman, A. and Shami, S.D., Renewable and Sustainable Energy Reviews, 19, 191–199, 2013.

Notes: √, in use, some mature solutions available; Δ, not currently in use, solutions can be developed; ~, ongoing research, some solutions available but under testing.

TABLE 6.3
BB-PLC Technologies Employed in CPNs

		IEEE 1901
	ITU-T G.hn	FFT-PHY	Wavelet-PHY
Frequency band	2–25 MHz	2–30 MHz	2–28 MHz
	2–50 MHz	2–48 MHz	2–60 MHz
	2-100 MHz	2-60 MHz
Maximum supported	1 Gbps	545 Mbps	544 Mbps
data rate
OFDM	Windowed	FFT	Wavelet
	2048, 4096 carriers	3072, 6144	512, 1024
		carriers	carriers
FEC	QC-LDPC	Turbo	RS, RS-CC,
		convolutional	LDPC
		code
Modulation	BPSK, QPSK, 8-, 16-,	BPSK, QPSK,	BPSK, 4-, 8-,
	64-, 256-, 1024-,	8-, 16-, 64-,	16-, 32-PAM
	4096-QAM	256-, 1024-,
		4096-QAM
Contention-based	CSMA/CA (4 priority	CSMA/CA (4	CSMA/CA (8
MAC scheme	levels)	priority levels)	priority levels)
Contention-free	TDMA	TDMA	TDMA
MAC scheme

Source: Rahman, M.M., Hong, C.S., Lee, S., Lee, J., Razzaque, M.A., and Kim, J.H., IEEE Communications Magazine, 49, 183–191, 2011.

6.3.2 PLC IN NANS

NANs incorporate the AMI components to collect the traffic generated in CPNs. Figure 6.3 shows an indicative network architecture, where the NANs employ PLC links. The traffic generated in the CPNs is routed to the network gateways, namely, the NAN DAPs, which may also serve for data aggregation. Specifically, critical data are usually routed to the utility premises without being aggregated, whereas data aggregation is usually applied to noncritical data. Even though only the PLC option is employed to implement the NANs in Figure 6.3, strict QoS constraints may necessitate a redundant SGC infrastructure in order to support time-critical applications.

The PLC links encountered in CPNs are short, so that BB-PLC may be effectively used. This is not the case in NANs, where longer links are encountered. Therefore, due to the lower attenuation in lower frequencies and the low-rate requirements in NANs, NB-PLC is preferable for NANs, especially to support DR applications, as argued in [31], where the PLC options available are compared with regard to their applicability in NANs. As to the standardization of PLC access networks, there is an ongoing process by the IEEE P1901.2 Task Group to standardize NB-PLC [32].

FIGURE 6.3 Indicative heterogeneous SGN architecture.

With regard to BB-PLC, although many PLC options are currently available for CPNs, this is not the case for NANs, since the only broadband option supporting access networks is IEEE 1901. The BB-PLC NANs may effectively support scalability and redundancy, and, when combined with node clustering approaches [33,34], they may successfully meet the various QoS constraints of SG applications. Also, the use of repeaters and the proper design of BB-PLC networks may render the BB-PLC option capable of supporting the traffic moving through the NANs [9].

In addition to PLC, other options may be employed to support the NAN infrastructure, provided that they guarantee reliable and secure data transmission. As to private wide area network (WAN) solutions, there is active research on licensed wireless solutions in an attempt to serve delay-sensitive applications [35,36,37]. Other mature solutions include Wi-Fi and GPRS/GSM infrastructures [38].

6.3.3 PLC IN FANS

FANs are usually incorporated into NANs, since they are both SGNs deployed over the MV grid. However, while NANs usually interface with metering devices dispersed over CPNs, FANs interface with wireless mesh options, that is, IEEE 802.15.4 protocol, necessitating a different communications platform. The authors in [39] classify FANs as typical cases of low-power and lossy networks (LLNs), since they exhibit connection losses and unpredictable errors caused by the severe voltage fluctuations and noise caused by the operation of field devices. Thus, FANs usually require different QoS handling, employing network layer protocols such as IPv6 over wireless personal area networks [40,41] to address the issues of end-to-end connectivity and reliability.

The low-rate applications supported by FANs render NB-PLC appropriate for FAN transmission, as claimed by the upcoming IEEE P1901.2 standard. Also, interoperability with the wireless IEEE 802.15.4 parts is imperative. Relevant key applications that require sophisticated network approaches to handle the heterogeneous nature of FANs are related to DA [31]. Also, PLC may effectively be used to support the detection and localization of faults by monitoring the signal-to-noise ratio (SNR) of the PLC signals [42].

6.3.4 PLC IN SNS

The SNs are usually the first SGNs to implement, since they support the most critical applications realized in the SG. Substation automation services include the remote monitoring and control of SCADA systems, phase measurement units (PMUs), remote terminal units (RTUs), and intelligent electronic devices (IEDs). The common characteristic of all these devices is that they generate SG information that needs to be collected via the backhaul networks, that is, the SN, in real-time synchronized mode of operation. Since synchronization is a critical issue, global positioning system (GPS) enabling is usually proposed in the literature [24]. As to PLC transmission, both BB-PLC and NB-PLC seem appropriate to serve SN communications, taking into account that the former option supports low whereas the latter supports high transmission rates. Other options may include wireless and optical media [43].

6.4 AGGREGATION AND POWER CONTROL IN SGC NETWORKS EMPLOYING PLC

The extended ICT infrastructure that enhances the traditional power grid with artificial intelligence gives rise to the generation of SG information. That is, as power generators generate power, SG entities, either AMR or other SG devices at the customer premises, act as generators of SG information, which, in the framework of PLC-enabled SGNs, is transferred via the power lines. The huge amount of data produced by the SG information generators necessitates proper management to optimize their exploitation. Moreover, as the number of SG information generators scales up, so does the need for proper handling of the resulting data traffic; the pursued facilitation of power grid monitoring comes at the cost of the growing complexity of the underlying communications architecture. The extreme heterogeneity of SG information generators and the necessity to support a variety of SG information services increase the need to optimize the SGN operation.

6.4.1 AGGREGATION OF PLC TRAFFIC

Depending on the type of traffic produced by the smart devices and on the associated services and business-to-business (B2B) or business-to-customer (B2C) service level agreements (SLAs), the SG data traffic may be categorized into several classes. Certain applications, such as substation automation, require extremely low transmission delay and are classified as time-critical applications. Other applications, such as the transmission of AMR data generated in CPNs, which do not require an immediate response fall into the class of delay-tolerant services. From the data accuracy point of view, applications such as AMR or voice over IP (VoIP) may tolerate a certain degree of data loss, allowing the application of lossy aggregation techniques, whereas applications such as substation automation require highly accurate data transmission from the SG data source to the utility’s back office, and vice versa.

The various QoS constraints explicitly imposed by the requirements of the services and applications supported may be properly traded off in the attempt to increase the efficiency of an SGN and, in certain cases, to increase its service capacity to accommodate more services or applications. In any case, imposing QoS constraints for satisfactory data services provisioning critically affects the operational characteristics of NANs, FANs, and SNs.

Data aggregation has been considered in the recent literature as a mechanism to manage the trade-off between communications efficiency and data accuracy [44,45]. Moreover, several recent studies have highlighted data aggregation as a way to preserve anonymity, without reducing the contextual information of the data reported to the utilities [46]. Since security and privacy are of primary importance for SG applications, data aggregation seems appealing for application in SGNs.

Although originally employed in the framework of wireless sensor networks (WSNs), the principles of data aggregation are also valid in the case of SGNs [47]. As the topology of the distribution grid may be modeled as a tree structure, and WSNs usually form tree-like structures for the routing of information, many data aggregation protocols destined for WSNs can be adapted to serve SGNs as well.

The design targets determining the application of data aggregation to QoS-constrained SGNs are primarily related to determining (i) which data flows can or should be aggregated, (ii) where the aggregation points should be located, and (iii) which aggregation procedure guarantees conformity with the delay-related QoS constraints of certain SG service classes. Notably, as delay reduction comes at the cost of bit error rate (BER) deterioration, the above design targets are not easy to achieve. Indicatively, determining the optimal aggregation tree in WSNs and SGNs may be reduced to the solution of the well-known minimum spanning tree (MST) problem, which is known to be NP-complete [48]. Also, proper scheduling of data transmission reporting by the SG devices, which is related to serving time-critical applications, has been widely studied and has been proven to be NP-hard [49]. Taking into account the above considerations, determining the appropriate parameters for SGN operation is a difficult task, reflecting the computational complexity that comes as a side effect of the enhanced monitoring and automation functionality offered by the SG.

6.4.2 POWER CONTROL AT PLC INFORMATION GENERATORS

In line with the need to optimize the transmission schedules of the information generators, the recent IEEE P1901 standard proposes two approaches for proper MAC, one based on the CSMA family of protocols and one implementing TDMA [6]. The latter establishes the necessity for collision-free transmission periods to (i) alleviate the negative effects of restoring information from collided packets received from the SG devices side and (ii) guarantee QoS provisioning for time-critical applications. Although general directions toward exploiting collision-free periods are given, exact scheduling algorithms have not yet been proposed.

To cope with the lack of a standard MAC scheme, several approaches have been recently proposed [50,51]. These approaches apply techniques originally destined for wireless transmission. However, in all the schemes proposed, any similarities of PLC transmission with wireless transmission were not fully exploited; multipath propagation, severe signal attenuation, and background noise drastically aggravate the efficiency of PLC transmission and should be taken into account. To this end, proper control of the injected power spectral density (IPSD) by the SG devices may offer advantages in enabling frequency reuse through transmission-slot reuse. By controlling the IPSD of the SG information generators, the distribution grid may be segmented into independent transmission areas, where simultaneous transmissions are allowed, increasing SGN throughput while reducing the transmission delay. The merits expected from the employment of power control combined with data aggregation in the context of tree-like PLC SG structures are presented in [49,50,51,52]. Interestingly, apart from the documented communications-related benefits, power control may also yield significant energy savings, which, considering the large numbers of SG information generators employed in SGNs, may prove nontrivial.

In conclusion, the introduction of ICT technologies enables full monitoring and control of the distribution grid at the cost of increased complexity and reduced efficiency of the necessary communication schemes. However, data aggregation alone or combined with proper IPSD control of the SG information generators may alleviate the negative effects of increased data traffic, simultaneously guaranteeing proper QoS provisioning and preserving end-user information anonymity, a feature of great importance to DSOs.

6.5 DESIGN GUIDELINES FOR SMART GRID IMPLEMENTATIONS

This section presents several basic guidelines that should be followed when designing SG networks. The design steps that should be followed are:

• Proper definition of the SG requirements: The first step when implementing SGs is to define the relevant requirements according to the DSO specifications. Many DSOs have deployed backbone fiber communication networks to monitor their crucial operations, especially in the high-voltage grid [53]; hence, in many cases, SNs are already deployed. On the other hand, DSOs have not yet deployed last-mile communication networks to exchange information with the various nodes of the transmission and distribution grids as well as with the end users. In these cases, the deployment of NANs and FANs is imperative. Therefore, the current stage of SG penetration in each case will determine the priorities in SGN deployment.

Despite the specific needs of DSOs, all SGNs should enable end users’ connectivity with the utilities’ premises through a reliable, secure, highly available, cost-effective, and resilient infrastructure. The need for reliability and security may lead to the selection of wired options for SGN implementation, whereas the necessity for optimal management of the cost–resilience trade-off may lead to the installation of redundant infrastructures or sophisticated PLC transmission schemes and optimal network planning, as indicated in [54].

• SG services: After the requirements imposed by the DSOs have been specified and the SGN type has been selected, the SG services must be defined. There are many reviews on QoS requirements of various SG services deployed over NANs, FANs, or SNs. As previously discussed in this chapter, SNs incorporate delay-sensitive applications. However, most of these networks have already been deployed and are properly managed. As far as DA is considered, the service requirements might vary significantly, since protection services impose strict delay constraints, whereas, on the other hand, metering services might be more tolerant to delays. In the case of NANs, the need for security, resilience, and anonymity calls for a robust and scalable SGN rather than a high-capacity one.

• Communications network support: Directly related to the SG services is the selection of the SGN transmission medium. To support mission-critical applications, the implementation of one-hop communication technologies is imperative; hence, wireless cognitive approaches are preferable. On the other hand, PLC seems preferable for delay-tolerant applications. The services QoS specified in the previous step usually leads to the deployment of hybrid networks. Techniques that offer interoperability or handle the performance trade-offs of the various transmission options are necessary. The SG interoperability standard [18] defines the interfaces between various SG entities, but does not handle issues related to data aggregation techniques or to the interoperability of various communications schemes.

• Design of IT applications: Last but not least is the design of IT applications that constitute the interface of the SG nodes with the SG. As far as utilities are concerned, these applications should address the issue of big data; that is, they should effectively handle the data generated by the SG devices. In this context, many application-based platforms employing semantic repositories [55] or cloud-based approaches [56] are considered in the literature. Regardless of the application platform employed, the introduction of novel aggregation schemes leads to a significant reduction of unnecessary network traffic, enhancing the SGN performance.

6.6 CONCLUSIONS

The transition toward smart power grids that support two-way flows of energy and information is imperative. In this framework, new services are introduced related to energy systems, communications platforms, and IT applications. The PLC transmission option is a strong candidate to support the various types of SGNs that should interoperate to offer reliable, end-to-end SG services:

1. BB-PLC gives rise to a high-capacity infrastructure capable of efficiently handling the traffic generated by CPNs.

2. Both NB-PLC and BB-PLC options may collect the traffic generated by CPNs and route this to the utilities’ back offices, thus supporting NANs’ communication. When combined with data aggregation techniques, PLC may satisfy an essential prerequisite of the SG, namely, preserving information anonymity. Also, when combined with injected power control, slot reuse in TDMA-based PLC transmission enhances network performance to meet the QoS constraints of time-critical applications.

3. NB-PLC seems appropriate to handle the low-rate traffic generated in heterogeneous FANs, especially when transmission of SG information from remote SGC nodes on the MV grid is required. When combined with the use of efficient network layer protocols, FANs may support the seamless integration of wireless and wired segments, increasing network availability.

In conclusion, there is no specific approach to designing SGNs. SG applications of variable QoS responding to different DSOs’ requirements may lead to different SG implementations. The need for resilience, security, reliability, and scalability, combined with the need for a cost-effective design, will determine how the various communications networks supporting the SG will be implemented.

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Table of Contents for Chapter 6 Role of PLC Technology in Smart Grid Communication Networks

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Table of Contents for
Chapter 6 Role of PLC Technology in Smart Grid Communication Networks