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• Conventional visual fatigue assessments cannot detect dynamic fatigue changes. • Dynamic visual fatigue assessment is proposed to measure fatigue changes. • Results are validated using SSQ analysis and video content features. • Video content features predict visual fatigue changes efficiently. • Dynamic visual fatigue significantly correlates with objective video features. People watching video displays for long durations experience visual fatigue and other symptoms associated with visual discomfort. Fatigue-reduction techniques are often applied but may potentially degrade the immersive experience. To appropriately adjust fatigue-reduction techniques, the changes in visual fatigue over time should be analyzed which is crucial for the appropriate adjustment of fatigue-reduction techniques. However, conventional methods used for assessing visual fatigue are inadequate because they rely entirely on post-task surveys, which cannot easily determine dynamic changes. This study employed a dynamic assessment method for evaluating visual fatigue in real-time. Using a joystick, participants continuously evaluated subjective fatigue whenever they perceived changes. A Simulator Sickness Questionnaire (SSQ) validated the results, which indicated significant correlations between dynamic assessments and the SSQ across five items associated with symptoms associated with visual discomfort. Furthermore, we explored the potential relationship between dynamic visual fatigue and objective video features, e.g., optical flow and the V-values of the hue/saturation value (HSV) color space, which represent the motion and brightness of the video. The results revealed that dynamic visual fatigue significantly correlated with both the optical flow and the V-value. Moreover, based on machine learning models, we determined that the changes in visual fatigue can be predicted based on the optical flow and V-value. Overall, the results validate that dynamic assessment methods can form a reliable baseline for real-time prediction of visual fatigue. [ABSTRACT FROM AUTHOR]

Highlights • This paper presents a comparison between distributed temperature sensing system (DTS) and spot temperature measurements to estimate the conductor temperature of overhead power lines in order to be used in dynamic rating operation. • The results are validated with the real-time monitoring of a 220 kV line placed in the north-east of Spain with a LA-455 conductor. • In the case studied, spot measurements are enough to obtain a good approximation of the temperature of the line conductor. • Further analysis should be done to check a broader range of load and weather conditions in order to be used in dynamic rating operation. Abstract The increase of global energy demand and new ways of electricity production are two of the main challenges for the power sector. The electric market has to address the addition of new and renewable sources of energy to the energy mix and to be able to integrate them into the grid, while maintaining the principles of robustness, security and reliability [1]. All of these changes point to the creation of smart grids, in which advanced generation, information and communication technologies are needed. An accurate knowledge of the electric grid state is crucial for operating the line as efficiently as possible and one of the most important grid parameters to be measured and controlled is the temperature of the overhead conductors due to their relation with the maximum allowable sag of the line and its thermal limit (annealing). This paper presents the results of real-time monitoring of an overhead power line using a distributed temperature sensing system (DTS) and compares these results with spot temperature measurements in order to estimate the loss of accuracy of having less thermal information. This comparison has been carried out in a 30 km long distributed temperature sensing system with fiber optic inside a LA-455 conductor and 6 weather stations placed along the line. An area of influence is defined for each weather station corresponding to the orography of the surroundings. The spot temperatures are obtained from the DTS in the nearest point from the weather stations assuming these six locations to be the ones where the spot temperature measurement equipment would be located. The main conclusion is that, in the case of study, spot measurements are enough to obtain a good approximation of the average temperature of the line conductor. [ABSTRACT FROM AUTHOR]

It is anticipated that with the thrust towards use of clean energy resources such as electric vehicles, future distribution grids will face a steep increase in power demand, forcing the utility operators to invest in enhancing the power delivering capacity of the grid infrastructure. It is identified that the critical 5–20 km medium voltage (MV) underground ac distribution cable link, responsible for bulk power delivery to the inner urban city substation, can benefit the most with capacity and efficiency enhancement, if the existing infrastructure is reused and operated under dc. Quantification of the same is offered in this paper by incorporating all influencing factors like voltage regulation, dc voltage rating enhancement, capacitive leakage currents, skin and magnetic proximity effect, thermal proximity effect and load power factor. Results are presented for three different ac and dc system topologies for varying cable lengths and conductor cross-sections. The computed system efficiency is enhanced with use of modular multilevel converters that have lower losses due to lower switching frequency. A justified expectation of 50–60% capacity gains is proved along with a generalized insight on its variations that can be extrapolated for different network parameters and configurations. Conditions for achieving payback time of 5 years or lower due to energy savings are identified, while the socio-economic benefits of avoiding digging and installing new cable infrastructure are highlighted. The technical implications of refurbishing cables designed for ac to operate under dc conditions is discussed in terms of imposed electric fields, thermal profile and lifetime. A novel opportunity of temperature dependent dynamic dc voltage rating to achieve additional capacity and efficiency gains is presented. [ABSTRACT FROM AUTHOR]

The recent push for renewable electrical energy sources has resulted in a significant increase in the installation of the offshore wind farms. These farms become much bigger than their earlier counterparts and the generated power is much larger. This puts additional performance requirements on the export cables. Long submarine export cables are not only subjected to changing laying conditions along the route, including depth and seabed material variations, but also the loading patterns vary significantly over time. Additionally, applied reactive power compensation measures and the time-dependent grid situation change the distribution of the current along the route. These unique features of long submarine power cables necessitate a new type of approach to their design and construction optimization. This paper introduces a new approach for ampacity calculations of long submarine power cables. As the ampacity calculations form a basis for the design of a cable route, it is of paramount importance that they are performed as accurately as possible. The approach can be applied to general-purpose circuit solvers, and this paper describes how to implement it using the ATP-EMTP software, which is extended to the consideration of concurrent electrical and thermal effects. The approach permits considering all the important local and time-dependent parameters of the analysis simultaneously. In particular, the approach allows simultaneous analysis of the varying laying conditions along the route including changes in the depth of burial and thermal resistivity of the soil together with the temporal variations of the cable loading. Additionally, current characteristics in long AC cable conductors are strongly affected by the reactive power flow, which in turn depends on the location of the reactive power compensation, the reactive power demand for grid operation, and the wind farm voltage reactive power control strategy. Such analysis cannot be performed with any existing analytical tool. Also, numerical tools cannot handle such problems because a 3-dimensional time-dependent analysis of a cable route which is 100 km long would encounter convergence problems as the size of such model would be prohibitive. Hence, at present, the proposed approach is the only one available to solve this complex electro-thermal problem. Several numerical examples illustrate an application of the proposed methodology. • Larger and more remote wind farms result in a need for larger and longer export cables. • Sound submarine cable design criteria should be established. • Long submarine power cables are subjected to locally and temporally varying electrical and thermal conditions on the route. • New calculation methods require new specialized computer tools taking into account the reactive compensation. • The proposed approach considers local parameters together with temporal variations of the load and reactive compensation. [ABSTRACT FROM AUTHOR]

Power system components usually have standard static ratings that determine the load constraints. Load constraints are designed for extreme conditions and are one of the reasons, why power systems do not use all of their potential transmission capacity. In the 21 st century, efficiency and the cost of energy production and distribution have become a very popular topic, because the energy production and its transmission cost has a direct influence on sustainability. Dynamic Rating is a smart grid application, which allows using more of the system capacity by monitoring system conditions. This paper presents a literature review on the topic of Dynamic Rating. We focus on Dynamic Rating of overhead lines. Overhead lines are of great interest for Dynamic Rating applications, because of their high cost and high potential for further improvement. Different tools for analysis of real time data and ways of application of Dynamic Rating to the power system are taken into consideration. [ABSTRACT FROM AUTHOR]

With the increasing deployment of solar power, high photovoltaic (PV) penetration is expected to adversely impact the distribution grid. One of the challenges relates to the power flow and transfer capacity of the distribution transformers. Transformers might not have sufficient capacity to accommodate for all the downstream PV to feed back to a higher voltage level during sunny periods with low consumption. In this paper, we estimate the transformer hosting capacity considering dynamic thermal rating for residential consumption with increasing amounts of PV penetration. This paper analyzes the impact of PV integration and increased consumption on the aging of a transformer. The potential of dynamic rating to enhance transformer hosting capacity is studied under varying environmental conditions. [Display omitted] • Quantified impact of PV and consumption on the transformer thermal characteristics. • Using thermal characteristics to define transformer hosting-capacity. • Existing consumption has a big impact on transformer hosting capacity or solar power. • DTR allows up to 60% extra growth in production or consumption for a transformer. [ABSTRACT FROM AUTHOR]