Smart Grid Telecommunications. Ramon Ferrús
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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.
In terms of electrical requirements, devices that are to be part of a Smart Grid deployment usually have to respect specific constraints in terms of voltage and frequency levels (admitted tolerances), power supply redundancy, battery lifetime, etc. These constraints are normally specific to the type of equipment and its location. IEC and IEEE differ in the way they fix some of these values.
A group of very relevant requirements refers to EMC. EMC collates different groups of aspects: radiated and conducted emissions, immunity to radiated and conducted disturbances, insulation, electrostatic discharge immunity, electrical fast transient/burst immunity, surge immunity, voltage‐dips/interruption immunity, etc. For conducted or radiated emission limits CISPR 32 is usually considered. Immunity requirements may be taken from tests proposed in IEC 61000‐4 series.
The rest of non‐functional requirements fall in the environmental category. This group refers to climatic and mechanical (vibration, shock, seismic) conditions, to be taken into account in the product lifecycle (storage, transportation, and in normal‐use regime) according to their different environmental conditions (weather‐protected, temperature control; stationary use, mobile use, portable use, etc.). There is a very complete reference in Europe in ETSI 300 019 series. The tests for the different classes are based on IEC 60068‐2 series “Environmental Testing – Part 2: Tests.” Alternatively, a much simpler reference is IEEE 1613.1. IK codes (IEC 62262) and IP codes (IEC 60529) for protection against ingress of solid foreign objects and against ingress of water with harmful effects need also to be taken into consideration, although these are not very different from other fields. Recommended limits for all these aspects can be found in [34].
There is a very important aspect that influences the relationship between telecommunications and the substation environment, and it has to do with earthing/grounding aspects [61]. Substations protect all elements inside them from unexpected HV events such as power faults and lightning strikes (anything that may cause a discharge of large amounts of electrical energy into its surroundings) by providing an equal‐potential zone with its ground grid. The substation ground grid connects all metal parts together to create an equipotential zone, so that everything within the compound is at the same potential. While this creates a safety mechanism for the substation, it will affect any externally connected metallic cable, if it is not properly engineered. This situation has been widely studied for PSs in IEEE 367‐2012, IEEE 487‐2015, and IEEE 1590‐2009, and although HV insulators have been developed to allow for the safe connection of, e.g., copper pairs reaching the substation from TSPs premises, the installation of optical fiber in dielectric cables, or radio‐based solutions, is preferred to connect substations. The situation is similar in SSs; although distances within SSs are much smaller, the MV ground reference is different to the LV ground reference of the neutral wire, and this imposes extra insulation requirements in devices connected to the MV and LV ground references, simultaneously.
1.6.7 Distributed Intelligence
There has been a recurrent discussion in utility industry around the IT and Telecommunication aspects of ICTs, when it comes to the availability of both in grid asset sites.
Computing power and telecommunications have been at large scarce resources. This fact, connected to the evolution of some traditional control system applications (i.e., SCADA), has configured different historical trends when deciding if system intelligence had to be distributed or centralized.
If we take the IT component, processing power has been expensive and bulky in the old times. At the same time, SCADAs started at power plants and PSs to automate operations locally (see Chapter 5) and that long‐distance Telecommunications were not readily accessible in many remote areas. These circumstances created an electric power system control structure that installed part of its computing power in distributed premises (substations).
However, the expansion of telecommunication capabilities, combined with the size reduction of computing power and the enhanced automation capabilities of evolving SCADAs, pushed a wave of SCADA system concentration that leveraged the cost savings produced by synergies in the SCADA operations. Thus, distributed intelligence started to diminish.
SCADA evolution was parallel to remote meter reading systems. The situation of these systems changed the perspective of the telecommunications access to substations. From the need to access a few PSs of early SCADAs, to the need to access many SSs where high‐throughput connectivity was not affordable, changed again the approach. At this point, the idea of “data concentrators” (see Chapter 5) appeared, as a way to downsize central MDM systems with a certain distributed intelligence.
Those two parallel stories of Smart Grid systems embryos, different in the use of ICT components, have reached our days, and numerous initiatives in Smart Grids show the influence of both.
In the telecommunications domain, the availability of high‐throughput connectivity is common today, and telecommunication bottlenecks are not to be expected in urban, suburban, or populated rural areas. Thus, the distributed intelligence concept is no longer generally a must. On the contrary, the general availability of communications to access all SSs leaves the decision on where to place computing power to utilities.
However, telecommunications themselves, and for their purpose of adapting to the various market needs, are witnessing two trends or types of systems in their evolution:
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