Smart Grid Telecommunications. Ramon Ferrús

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СКАЧАТЬ the likely exception of the meter locations construction, street‐cabinets and fuse boxes were never probably understood prone to host telecommunications. Meter rooms, as the result of the effort to avoid the installation of meters inside homes, are presented as built‐in wall enclosures or conditioned rooms for meters, depending on the house‐type. Thus, meter rooms and such spaces may have the capability (and the utilities the right) to host telecommunication equipment, as derived from the need to access meters for remote reading purposes. LV grid present a more amiable situation, as LV power supply is always available and there are easy and cheap ways to connect to the cables with piercing devices.

      1.6.5 Telecommunication Services Control

      The impact of telecommunication services on Smart Grid operations is a key aspect of the enablement of telecommunications for the grid. Telecommunications are not a simple add‐on over the grid, but a transformation vector. Whenever grid operations rely on telecommunications, telecommunications become as critical to the utility as any other resource.

      Telecommunications private network design and/or third‐party TSP service selection must be performed to allow the provision of the Smart Grid needed services within the utility license conditions. When the utility operates a private network for this purpose, the performance responsibility is within its decision range. However, when third‐party TSP services are involved, Service‐Level Agreements (SLA) must be clearly defined to govern service delivery conditions.

      ITU‐T E.860 provides a framework for SLAs, defined as “a formal agreement between two or more entities that is reached after a negotiating activity with the scope to assess service characteristics, responsibilities and priorities of every part. An SLA may include statements about performance, tariffing and billing, service delivery and compensations.” SLAs are based in some formal definitions that must be well known to both parties, especially when referred to the service characteristics that need to be expressed in telecommunication technical terms. However, they must also collate (see ITU‐T G.1000 and its reference to ETSI ETR 003) all different service functions (sales, service management, technical quality, billing processes, and network/service management by the customer) and quality criteria with each of them (speed, accuracy, availability, reliability, security, simplicity, and flexibility), to be consistent with the objective.

      Smart Grid needs must be transformed into telecommunication technical parameter requirements that measure network performance. Network performance is defined as in ITU‐T Recommendation E.800, as “the ability of a network or network portion to provide the functions related to communications between users.” Performance is critical for applications to deliver their expected benefits and must be properly planned and controlled in networks that share resources among different users.

      Two of the most important performance parameters in telecommunications are throughput and latency. These general parameters are included in the network performance objectives of different networks (e.g., ITU‐T I.350 and Y.1540 for digital and IP‐based networks):

       Throughput is the maximum data rate where no packet is discarded by a network. Throughput is usually measured as an average quantity, with control over the peak limits.

       Latency is the time it takes for a data packet to get from one point to another. Latency is usually defined as a requirement below a certain limit.

Service performance is assessed in terms of its Quality of Service (QoS). ISO 8402 defines QoS as “the totality of characteristics of an entity that bear on its ability to satisfy stated and implied needs.” ITU‐T E.800 defines it as “the collective effect of service performance which determine the degree of satisfaction of a user of the service.” Beyond QoS, QoE (Quality of Experience as in ITU‐T E.804) enters into the subjective domain of the service users' perception that cannot be neglected as it reflects previous experiences and expectations. Thus, SLA, QoS, and QoE go beyond the pure technical perspective.

      Eventually, telecommunication systems must absorb all these service requirements and integrate them in their complex network structures. These networks will not only deliver them but also control and manage its performance in different circumstances. ITU‐T Study Group 12 “Performance, QoS and QoE” [60] is leading this work, as in ITU‐T E.804 “QoS aspects for popular services in mobile networks” and ITU‐T Y.3106 “Quality of service functional requirements for the IMT‐2020 network.”

      1.6.6 Environmental Conditions

      The harsh conditions of most grid sites are one of the most important aspect that need to be taken into account when designing a telecommunications network for Smart Grids or when using telecommunications services provided by a TSP. It needs to be born in mind that most electric grid premises are neither set up in the way a telecommunications site would be, nor service points are typical residential houses.

      On the contrary, there are many aspects that need to be considered to design telecommunication products for Smart Grids. We will refer to them as non‐functional requirement (“functional” refers to their function within the telecommunications network), and they include electrical, Electromagnetic Compatibility (EMC), and environmental requirements. Most of them prevent a cost‐effective introduction of telecommunication elements in the Smart Grid.

      IEC and IEEE are the two main bodies that tackle the specific requirements for devices to be installed at substations and similar locations.

      IEC has several series of standards setting requirements as a reference for Smart Grid‐related equipment in substations. Technical Committee TC 57 “Power Systems Management and Associated Information Exchange,” dealing with “power systems control equipment and systems including EMS (Energy Management Systems), SCADA (Supervisory Control And Data Acquisition), distribution automation, teleprotection, and associated information exchange for real‐time and non‐real‐time information, used in the planning, operation and maintenance of power systems,” is the most relevant in this context, while TC 95 “Measuring relays and protection equipment” has a certain role for some device types in the grid (their non‐functional requirements might also be considered to the extent where there is not a better reference):

       IEC 60870 “Telecontrol Equipment and Systems”, within TC57. This series has a broad scope in terms of monitoring and control, not just in the substation:IEC 60870‐2‐1 focuses on electromagnetic compatibility.IEC 60870‐2‐2 focuses on environmental conditions (climatic, mechanical, and other nonelectrical influences) and partially supersedes IEC 60870‐2‐1.

       IEC 61850 “Communication Networks and Systems for Power Utility Automation,” also within TC 57, is much more recent than the IEC 60870 series and focuses in substations and power plants:IEC 61850‐3 focuses on environmental aspects of utility communication and automation IEDs and systems.

       IEC 60255 “Measuring relays and protection equipment” and “Electrical Relays” in TC 95 gives requirements specifically for protection devices.

      In IEEE, the Power and Energy Society's Substations Committee produced IEEE 1613 to specify “standard service conditions, standard ratings, environmental performance requirements and testing requirements for communications networking devices installed in electric power substations.” It complements IEC 61850‐3. This standard has broadened its scope with IEEE 1613.1 (in collaboration with the Transmission and Distribution Committee), to cover other devices installed in all electric power facilities, not just substations, specifically applicable for devices used in DA and DG. Interestingly, it explicitly mentions device testing and performance requirements for communications via Radio Frequency (RF), Power Line Communications (PLC), Broadband over Power Line (BPL), or Ethernet cable.

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