Control Level 3
2.6 Smart Grids
2.6.5 Interoperability and Standards
The goal of a secure, reliable and efficient electric grid is directly associated with the communications infrastructure. In SGs the integration of different elements and components requires a syntactic and semantic interoperability approach besides the interoperability at the communication network level. The use of standards enables a common semantic (data model), a common syntax (protocol) and a common network concept [22].
Given the considerable amount of standards applicable to the smart grids concept and others being crafted specifically for SG applications, a classification of standards according to their domain and purpose is necessary. The Grid Wise Architecture Council (GWAC) defined eight interoperability categories, known as GWAC interoperability layer model, relevant for generation, transmission and distribution segments. These layers are distributed over three main categories: organizational, informational and technical, as depicted in Fig. 2.8 from [23].
Within the technical category it is possible to match communications standards to different interop-erability layers as proposed in Table 2.4 for smart grid applications. In terms of basic connectivity the identified standards span from wired power lines to wireless license and unlicensed alternatives, somehow anticipating the support for different applications and communications network segments.
In 2011 the European Standards Organizations (ESOs), composed of CEN, CENELEC and ETSI, issued a set of recommendations concerning the standardization for smart grids in Europe [24] involving several areas. Standards are recognized as an efficient mechanism to promote EU industry cooperation
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Figure 2.8: GWAC Interoperability Layer Model
and interoperability by allowing the accommodation of existing and novel solutions; general recommen-dations identified the need to focus on product requirements and promote standardization activities on interfaces instead of applications and solutions. The need for a reference architecture is highlighted and recommendations are made concerning: a conceptual model to define the interaction between stakehold-ers; a functional architecture based on the IEC/TC57 model to tackle both general and specific aspect of European smart grids; a communications architecture that defines the different connectivity scenarios and networks. Recommendations are further detailed considering communications interfaces with suggestions for: an interaction between different domains, particularly between AMI systems and other SG subsys-tems; a harmonization at data transport level; and further development of power line communications.
The IEEE 1901 is pointed out as the broadband standard to be considered as an alternative to existing similar European standards.
The European Commission has issued a mandate to ESOs, the M/490, related with standards to support the deployment of a European smart grid. As defined in [25] the objective is to address standards for SG within the European framework toward the integration of communications technologies with electrical architectures, considering the associated processes and services. The expected deliverables include a technical reference architecture, with the functional information data flows between domains and systems, and a set of standards, which include communications protocols and data models. One particular aspect raised by the mandate is the large scope of smart grids and it emphasizes the risks of inconsistencies since too many standardization bodies will address related SG topics.
Recently, the ESOs have released the first set of standards along with a reference architecture as the initial work of the objectives established for the M/490. This list [26] is a general selection guide of stan-dards targeting different systems (domain, function and other) and layers (component, communications and information) considering the Smart Grid Architecture Model (SGAM). This reference model was de-fined over the GWAC interoperability categories. The methodology used to present the smart grid related standards consists of mapping them into the SGAM reference architecture, where some cross-cutting
do-Table 2.4: GWAC Technical Layers Description
Layer Purpose Examples of Standards
Syntactic Interoperability
Understanding of data structure in messages exchanged between systems
IEC Family (61850, 62056, 61970, etc.)
Network Interoperability
Exchange messages between systems across different networks
IP Suite
Basic Connectivity Mechanisms to enable physical and logical connectivity between systems
IEEE 802.x Family (802.3, 802.11, 802.16, 802.15.4, etc.) Powerline (HomePlug, Prime, IEEE 1901 Family)
mains are defined separately. A rank is established wherein standards from European Organizations are considered first; then, if no standards from these institutions are available, ISO, IEC and ITU standards are considered. If still there are no standards to address particular aspects of SGs, then they are con-sidered in an open basis. Communications technologies and standards are addressed considering wired and wireless media, with a particular reference of powerline, and matched with SGAM sub-networks as presented in Table 2.5, adapted from [26]. In term of the last-mile it is noticeable the different networks that are associated with it namely the subscriber access network, neighborhood network and the field area network.
Eurelectric and the European Distribution System Operators (EDSO) association have jointly defined the priorities in terms of standardization for smart grids. In [27] standards are approached according to three main categories: network management; integration of DG and EV; and market and customers. No recommendation in terms of communications technologies is made by these associations since different applications, scenarios and performance related issues need to be addressed. All technologies should be considered, either wired or wireless. They recognize the convenience of PLC related technologies in ensuring a low invasive connectivity infrastructure, especially in locations without radio coverage, but they also raise concerns associated with electromagnetic interference phenomena. A general recommendation is made about the possibility of using PLC in MV and LV networks along with complementary standards and regulation efforts to address interference. The use of PLC for mission-critical functions is recommended to be further addressed namely at the technology level. In terms of data models several IEC standards are identified considering the data models for electric devices, the structures and semantics of Common Information Model (CIM), Internet based web services, cyber-security, among others.
The International Electrotechnical Commission (IEC) is one of the standardization bodies most com-mitted to developing standards for smart grids. It is well known the extensive work developed by IEC, namely for the electric industry, and a strategy group was recently created with the objective of defin-ing a smart grid standardization roadmap [22]. This document incorporates IEC standards envisagdefin-ing the enhancement of monitoring and control systems and components of SGs by means of semantic and syntactic interoperability. With this respect, one of the most significant contributions is the Seamless Integration Architecture (SIA) defined by the Technical Committee 57 (TC 57). This interoperability model is part of the IEC 62357-1 standard [28] and is reproduced in Fig. 2.9. It combines IEC standards with application and business layers at the top and middle, electric power systems at the bottom and security and data management in the left [9].
Table 2.5: ESOs Communications Technologies and Standards for SG sub-networks
Standard/Technology SubscriberAccessNetwork NeighbourhoodNetwork FieldArea Low-endintrasubstation Intra-substation Inter-substation Intracontrolcentre Intradatacentre Enterprise Balancing Interchange Transregional TransNational WAN IndustrialFieldbus Narrowband PLC (LV & MV) x x x
Narrowband PLC (HV & VHV) x x
Broadband PLC x x
EN 14908 x x
EN 50090 x x
IEEE 802.15.4 x x x
IEEE 802.11 x x x x
IEEE 802.3/1 x x x x x x
IEEE 802.16 x x x
ETSI TS 102 887 x x
IPv4 x x x x x x x x x x x x x x
IPv6 x x x x x x x x x x x x x x
RPL/6LowPan x x x
IEC 61850 x x x x x x
IEC 60870-5 x x x x
GSM/GPRS/EDGE x x x
3G/WDCMA/UMTS/HSPA x x x x x x x x x x
LTE/LTE-A x x x x x x x x x x x x x
SDH/OTN x x x x x x x x x x x x x x
IP MPLS/MPLS TP x x x x x x x x x x x x x x
EN 13757 x
DSL/PON x x x x
Last-Mile
Table 2.6 only summarizes the IEC core of SG family standards3 and respective target applications, given the extensive listing of IEC SG related standards.