Stepwise investment plan optimization for large scale and multi-zonal transmission system expansion

This paper develops a long term transmission expansion optimization methodology taking the probabilistic nature of generation and demand, spatial aspects of transmission investments and different technologies into account. The developed methodology delivers a stepwise investment plan to achieve the optimal grid expansion for additional transmission capacity between different zones. In this paper, the optimization methodology is applied to the Spanish and French transmission systems for long term optimization of investments in interconnection capacity

Long term investment optimization methodology for multi-zonal transmission expansion

This paper introduces a stepwise investment optimization methodology for transmission system expansion planning. The objective of the developed methodology is to determine transmission expansion plans to realize a desired interconnection capacity between multiple zones minimizing investment and operational costs. The methodology uses MILP optimization and a modified A∗ shortest path algorithm sequentially in order to determine the optimal investment time point, transmission topology, technology and routing. Spatial constraints and their effects on the installation cost are taken into account in the technology and route optimization. A possible application of the methodology is demonstrated on a stepwise investment plan for the North Sea region

Recording behaviour of indoor-housed farm animals automatically using machine vision technology: a systematic review

Large-scale phenotyping of animal behaviour traits is time consuming and has led to increased demand for technologies that can automate these procedures. Automated tracking of animals has been successful in controlled laboratory settings, but recording from animals in large groups in highly variable farm settings presents challenges. The aim of this review is to provide a systematic overview of the advances that have occurred in automated, high throughput image detection of farm animal behavioural traits with welfare and production implications. Peer-reviewed publications written in English were reviewed systematically following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. After identification, screening, and assessment for eligibility, 108 publications met these specifications and were included for qualitative synthesis. Data collected from the papers included camera specifications, housing conditions, group size, algorithm details, procedures, and results. Most studies utilized standard digital colour video cameras for data collection, with increasing use of 3D cameras in papers published after 2013. Papers including pigs (across production stages) were the most common (n = 63). The most common behaviours recorded included activity level, area occupancy, aggression, gait scores, resource use, and posture. Our review revealed many overlaps in methods applied to analysing behaviour, and most studies started from scratch instead of building upon previous work. Training and validation sample sizes were generally small (mean±s.d. groups = 3.8±5.8) and in data collection and testing took place in relatively controlled environments. To advance our ability to automatically phenotype behaviour, future research should build upon existing knowledge and validate technology under commercial settings and publications should explicitly describe recording conditions in detail to allow studies to be reproduced

Use of Extended Characteristics of Locomotion and Feeding Behavior for Automated Identification of Lame Dairy Cows.

This study was carried out to detect differences in locomotion and feeding behavior in lame (group L; n = 41; gait score ≥ 2.5) and non-lame (group C; n = 12; gait score ≤ 2) multiparous Holstein cows in a cross-sectional study design. A model for automatic lameness detection was created, using data from accelerometers attached to the hind limbs and noseband sensors attached to the head. Each cow's gait was videotaped and scored on a 5-point scale before and after a period of 3 consecutive days of behavioral data recording. The mean value of 3 independent experienced observers was taken as a definite gait score and considered to be the gold standard. For statistical analysis, data from the noseband sensor and one of two accelerometers per cow (randomly selected) of 2 out of 3 randomly selected days was used. For comparison between group L and group C, the T-test, the Aspin-Welch Test and the Wilcoxon Test were used. The sensitivity and specificity for lameness detection was determined with logistic regression and ROC-analysis. Group L compared to group C had significantly lower eating and ruminating time, fewer eating chews, ruminating chews and ruminating boluses, longer lying time and lying bout duration, lower standing time, fewer standing and walking bouts, fewer, slower and shorter strides and a lower walking speed. The model considering the number of standing bouts and walking speed was the best predictor of cows being lame with a sensitivity of 90.2% and specificity of 91.7%. Sensitivity and specificity of the lameness detection model were considered to be very high, even without the use of halter data. It was concluded that under the conditions of the study farm, accelerometer data were suitable for accurately distinguishing between lame and non-lame dairy cows, even in cases of slight lameness with a gait score of 2.5

Optimal DC reference voltage in HVDC grids

In a HVDC grid, power energy equilibrium must be guaranteed at every moment to prevent DC voltage to increase or decrease to unacceptable values. Contrary to the frequency in an AC power system, the DC voltage cannot be assumed to be the same throughout the system, since a DC voltage difference is necessary to have a current flow. To operate HVDC grids as far as possible from DC voltage stability limits, the selection of the DC reference voltage and DC reference node are crucial factors. This paper introduces a method to find the optimal DC voltage in a HVDC grid based on power flow and line resistances. The method is implemented in the open-source software MatACDC and the results are verified by dynamic simulations in DIgSILENT, using a one area DC voltage restoration controller.status: publishe

Transmission system topology optimization for large-scale offshore wind integration

A method to determine the optimal transmission system topology for multiple offshore wind farms is introduced using a rule-based generic algorithm. The methodology is implemented as a software tool determining the best economical and technically feasible offshore transmission solution. The optimization algorithm takes radial, ring shaped, and meshed transmission topologies into consideration. Besides the investments for the offshore grid also new connections or reinforcements in the existing onshore grid are proposed by the algorithm. The developed tool delivers a set of transmission system topologies ranked after their life cycle system costs with their corresponding transmission voltage and technology (HVAC or HVDC), the necessary transmission equipment, and its rating. The optimization results are based on publicly available data. The achieved results are compared with other studies and validated. The developed tool can be used in the planning phase as a guidance for offshore developers with investment decisions and for long-term offshore grid planning, e.g., towards an offshore supergrid

Needed investments in the power system to bring wind energy to shore in Belgium

Renewable energy sources, and especially wind, take an increasing fraction of the European electric energy generation and they form an important part of the plans of the European commission towards a more sustainable future. Also for Belgium, wind power offers the most important renewable energy potential. Especially offshore wind power projects are booming and more than 2 GW is announced to be installed in the Belgian coastal waters. Of course, this energy needs to be transported to the mainland. At this moment however, the power system near to the coast is not ready to absorb such large amounts of electric power. New investments in transmission lines will be needed but these have been difficult in the densely populated country and further public opposition out of social, environmental and political concern is expected. For this paper, the Belgian situation is examined considering different investment options. A novel optimal investment model based on [1] is used to determine the techno-economic optimal investment policy

Robustness evaluation of fast breaker failure backup protection in bipolar HVDC grids

To ensure a reliable fault clearing, a backup protection scheme is required for selective HVDC grid protection. One way to achieve this is to use both voltage and current measurements to distinguish uncleared faults from cleared ones during the fault clearing process of the primary protection. This paper studies the applicability of such a backup protection algorithm in meshed bipolar HVDC grids and evaluates the robustness of the algorithm against system operating conditions and breaker opening delays. The influence of different operating conditions on the fault waveforms is analysed using a three-terminal bipolar test system. The robustness of the fast breaker failure backup protection algorithm is evaluated via simulation studies on the bipolar test system in PSCAD. The simulation results show that the fast breaker failure backup protection algorithm can distinguish between uncleared and cleared faults with sufficient margin for all considered operating conditions.status: publishe

Technology and topology optimization for multizonal transmission systems

This paper presents a method to optimize equipment investments in multizonal transmission systems, considering spatial properties of the areas of focus. Together with a probabilistic technique for assessing nodal injection capability, the method in the paper completes the methodology of a long term transmission system planning tool. Transmission topology, line route and technology are optimized through iterative application of linear integer programming and Dijkstra's shortest path algorithm. By optimizing the transmission route, the spatial properties of the area of focus are taken into account, which in turn can significantly influence the installation costs of transmission equipment. The optimization method considers both AC and DC technology and takes the N-1 security criterion into account

Fair reliability management: Comparing deterministic and probabilistic short-term reliability management

Fairness is considered important in various contexts. Although electricity is an essential public good in modern societies that should be affordable and accessible on a fair, nondiscriminatory basis, there is no assessment of fairness in a power system reliability context. Nevertheless, fairness might become an issue with probabilistic short-term reliability management approaches that enable system operators to differentiate between consumers based on their value of lost load. This paper focuses on equality between consumers in terms of energy not supplied. A transparent assessment of inequality in short-term power system reliability management is illustrated that uses an inequality ratio and inequality index to quantify the level of inequality between entities, such as nodes, consumer groups or individual consumers. Inequality resulting from short-term probabilistic reliability management and reliability management based on a deterministic N-1 criterion are assessed in a case study for a five-node and 24-node test system. The proposed inequality assessment enables system operators and regulating bodies to verify the social acceptability of reliability management approaches and criteria