International audienceThis paper presents an overview of the state of the art on the research on Dynamic Line Rating forecasting. It is directed at researchers and decision-makers in the renewable energy and smart grids domain, and in particular at members of both the power system and meteorological community. Its aim is to explain the details of one aspect of the complex interconnection between the environment and power systems. The ampacity of a conductor is defined as the maximum constant current which will meet the design, security and safety criteria of a particular line on which the conductor is used. Dynamic Line Rating (DLR) is a technology used to dynamically increase the ampacity of electric overhead transmission lines. It is based on the observation that the ampacity of an overhead line is determined by its ability to dissipate into the environment the heat produced by Joule effect. This in turn is dependent on environmental conditions such as the value of ambient temperature, solar radiation, and wind speed and direction. Currently, conservative static seasonal estimations of meteorological values are used to determine ampacity. In a DLR framework, the ampacity is estimated in real time or quasi-real time using sensors on the line that measure conductor temperature, tension, sag or environmental parameters such as wind speed and air temperature. Because of the conservative assumptions used to calculate static seasonal ampacity limits and the variability of weather parameters, DLRs are considerably higher than static seasonal ratings. The latent transmission capacity made available by DLRs means the operation time of equipment can be extended, especially in the current power system scenario, where power injections from Intermittent Renewable Sources (IRS) put stress on the existing infrastructure. DLR can represent a solution for accommodating higher renewable production whilst minimizing or postponing network reinforcements. On the other hand, the variability of DLR with respect to static seasonal ratings makes it particularly difficult to exploit, which explains the slow take-up rate of this technology. In order to facilitate the integration of DLR into power system operations, research has been launched into DLR forecasting, following a similar avenue to IRS production forecasting, i.e. based on a mix of statistical methods and meteorological forecasts. The development of reliable DLR forecasts will no doubt be seen as a necessary step for integrating DLR into power system management and reaping the expected benefits
Microgrids can be used for securing the supply of power during network outages. Underground cabling of distribution networks is another effective but conventional and expensive alternative to enhance the reliability of the power supply. This paper first presents an analysis method for the determination of microgrid power supply adequacy during islanded operation and, second, presents a comparison method for the overall cost calculation of microgrids versus underground cabling. The microgrid power adequacy during a rather long network outage is required in order to indicate high level of reliability of the supply. The overall cost calculation considers the economic benefits and costs incurred, combined for both the distribution network company and the consumer. Whereas the microgrid setup determines the islanded-operation power adequacy and thus the reliability of the supply, the economic feasibility results from the normal operations and services. The methods are illustrated by two typical, and even critical, case studies in rural distribution networks: an electric-heated detached house and a dairy farm. These case studies show that even in the case of a single consumer, a microgrid option could be more economical than network renovation by underground cabling of a branch in order to increase the reliability.The profitability possibilities of residential microgrids as an aggregator-based solution to the perspective of different stakeholders, for example, utilities, aggregators, and prosumers, were analyzed in [6]. The feasibility and profitability of microgrids participating in the primary frequency control reserve (FCR) market through an aggregator were assessed in [7]. Furthermore, battery energy storage system (BESS) usage on the frequency regulation market was analyzed in [8].According to [9], underground cabling of the network is an effective way for distribution system operators (DSOs) to increase the reliability of power supply. However, underground cabling is expensive.Today, farming is highly automated and electricity-dependent [10], and even short power interruptions are very detrimental. Farming is an energy-intensive industry [11], and thus farmers value the reliability of the electricity supply more so than most of the other customer groups.Farms are located naturally in rural areas, possibly on the long distribution network radial branches with low electricity customer density. The majority of farmers have backup generators (e.g., [11]). Farmers having their own power production to cover a portion of their electricity need is gaining popularity.Several recent studies have focused on microgrid islanded-mode operation, microgrid energy management systems, and power supply adequacy and forecasting (e.g., [12][13][14]). The power supply capability in islanded-mode operation was assessed in [12] over a few hours by using a simulation maximum time step of 1 min. Electro-technical aspects of an unexpected microgrid islanded operation were also analyzed in [14] while considering optimal energy management of...
Microgrids could be utilized to improve the distribution network resiliency against weather-related network outages and increase the security of power supply of rural electricity consumers. Whereas underground cabling is expensive for the distribution system operator (DSO), an alternative microgrid investment could benefit the DSO and consumer, provided the necessary changes were made in the network regulation. A rural detached house customer microgrid is analysed in comparison to underground cabling, considering the uncertainties in the calculation parameters through a sensitivity analysis. Adequacy of the microgrid power supply during unexpected network outage for a reasonably long duration is assessed, as well as the economics of the feasible microgrid setup consisting of variable generation, controllable generation, and electric storage. The total costs and benefits for the DSO and consumer/prosumer are considered. A microgrid would likely be a more cost-efficient option overall, but not as-is for the consumer. The battery energy storage system (BESS)-related cost-sharing strategies are suggested in this paper in order to assess possible break-even investment solutions for the related parties. The sensitivities of the microgrid and cabling investments were considered in particular. Cost-sharing strategies under network regulatory framework would need to be developed further in order for both the consumer and DSO to benefit from the solution as a whole.
Microgrids can be used for securing power supply during network outages. Underground 42 storage system (BESS) usage on the frequency regulation market.43 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 25According to [9] underground cabling of the network is an effective way for distribution system 44 operators (DSOs) to increase the reliability of power supply. However, underground cabling is 45 expensive. 46Today, farming is highly automated and electricity dependent [10] and even short power 47 interruptions are very detrimental. Farming is an energy intensive industry [11], and thus farmers 48 value reliability of electricity supply more than most of the other customer groups. 49Farms are located naturally in rural areas, possibly on the long distribution network radial 50 branches with low electricity customer density. The majority of farmers have back-up generators (e.g. 51[11]). Farmers having own power production to cover a portion of their electricity need is gaining 52 popularity. 53Several recent studies have focused on microgrid islanded mode operation, microgrid energy 54 management system, and power supply adequacy and forecast, e.g. [12][13][14]. Ref.[12] assessed power 55 supply capability in islanded mode operation within a couple of hours by using a simulation time 56 step of maximum 1 minute. Electro-technical aspects of an unexpected microgrid islanded operation 57 were also analyzed in [14] while considering optimal energy management of the microgrid and 58 anticipating an outage at any hour. Grid-connected microgrid economic operating strategy was 59 proposed in [15] to minimize the operating cost for the operating period of 24 hours-ahead. 60Characteristics of, e.g. the Finnish rural medium voltage (MV) networks are long distances and 61 low loads, and thus, underground cabling to increase reliability is not an economical option as-is for 62 the distribution network development. However, the legislation steers towards underground cabling 63 and cabling is incentivized by the regulation framework. 64 Ref. [16] posed a question, on which reliability indices the network development actions actually 65 should be based on, optimizing the number of faults, duration of faults, outages cost, or yet on some 66 other index. The indices in several Finnish studies considering the economics of cabling and 67 increasing reliability of power supply, are based on the results and data of a study from 2005, and the 68 regulation model framework, e.g., [16-19]. The studies evaluate the DSO investment profitability 69 only compared to the outage costs (or cost of energy not supplied, CENS). The customer-side and 70 possible co-operative technical and shared economic alternatives have not been considered. 71Studies have shown other alternatives' feasibility potential instead of underground cabling, e.g., 72BESS as back-up to cope with short interruptions up to a couple of hours, [19,20]. BESS sizing methods 73 in different microgrid application have been reviewed in [21], and [22] presented an a...
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