The design of all-electric aircraft (AEA) electrical distribution systems requires a balance between fault tolerance, protection selectivity, and powertrain mass. Existing studies commonly evaluate predefined architectures, which limits the number of alternative configurations that can be compared consistently. This thesis develops a parameterised, graph-based framework for systematically generating, evaluating, and ranking fault-tolerant AEA electrical distribution architectures.

The investigated propulsion system consists of eight 1.5 MW motors with a nominal propulsion demand of 12 MW. Candidate architectures vary the number of battery packs, connectors, busbars, and motor feeders, together with their protection arrangements. Following an imposed failure, a capacitated maximum-flow model determines the propulsion power that can still be delivered through the surviving network. Catastrophic minimal cut sets (MCSs) are evaluated up to second order and combined using a rare-event approximation. The same architecture is subsequently assessed using topology-dependent component-mass, cable-sizing, and physical-routing models. A configuration is considered feasible when at least 9.0 MW of propulsion power remains available, all relevant faults are successfully contained, Pcat ≤ 10⁻⁹ fh⁻¹, and the total powertrain mass remains below 42,000 kg.

Four custom architecture families are evaluated: 4B–4C–2Bus, 4B–4C–3Bus, 4B–4C–4Bus, and 8B–8C–4Bus. The results show that selective individual motor-feeder protection is required in the highest-ranked feasible configuration of every architecture family. The lowest-mass feasible configuration is the 4B–4C–4Bus one-phase architecture, with a total powertrain mass of 41,422.6 kg and Pcat = 9.038 × 10⁻¹¹ fh⁻¹. The 4B–4C–2Bus two-phase architecture provides the largest evaluated reliability margin, with Pcat = 3.169 × 10⁻¹¹ fh⁻¹ and a mass of 41,425.7 kg. The mass difference between these configurations is only 3.1 kg, while the latter achieves an approximately 2.85-times lower catastrophic failure probability.

The results demonstrate that increasing redundancy alone does not necessarily improve the architecture. Fault tolerance depends strongly on where redundant paths are introduced and whether protection can selectively isolate failed feeders while retaining healthy alternatives. The developed framework therefore provides a systematic method for comparing reliability–mass trade-offs during early-stage AEA architecture design, rather than a certification-level safety prediction or a unique globally optimal architecture. ... Read more

The increased integration of renewable energy sources and power electronic converters has transformed conventional power systems into hybrid AC-DC systems, introducing faster and more complex fault dynamics that challenge existing protection schemes. While data-driven approaches have demonstrated high accuracy in fault detection and classification, their lack of prediction validation limits their reliability in critical protection systems. This thesis proposes a real-time data-driven framework for event classification and validation for Hybrid AC-DC systems. A comprehensive dataset of AC and DC faults was generated from an RTDS based grid model, with transient measurements acquired using a Python-based communication interface and processed to extract time domain and dynamic fault features. Independent machine learning classifiers were developed for the AC and DC subsystems. An additional waveform signature validation layer that uses representative transient signatures of event classes and similarity analysis was introduced to verify classifier predictions. Performance evaluation demonstrated that the proposed framework achieves accurate and robust event classification under varying operating conditions and moderate signal degradation, while providing additional confidence assessment for machine learning-based classifier predictions. The proposed approach offers a practical and reliable solution for real-time monitoring, event identification, and supervisory protection in future converter-dominated power systems. ... Read more

In the coming years, a large portion of the 110 and 150 kV substations in the Netherlands will be replaced. For this, the Dutch TSO TenneT has introduced the Bay Replacement Program (BRP), in which the old bays are being replaced completely by standard, modular, and compact skid-mounted bays. These bays are, in principle, plug-and-play, except for the busbar disconnector, for which the pantograph has to be aligned to the overhead busbar. To make substations even more compact in the future, this thesis aims to investigate the switching impulse breakdown strength of short air gaps relevant to maintenance of the 110 kV BRP busbar disconnector, in order to determine the minimum safety clearances.

The validity of the Schneider and Weck method for simulating the gap factor of short gaps (gap distance smaller than 2 meters) is investigated. Electric field simulations in COMSOL were compared with the original results from Schneider and Weck. The simulations reproduce the original results with deviations below 5% for gaps larger than 2 meters. For gaps smaller than 2 meters, the results show irregular behaviour. Experiments on a rod-plane and conductor-rod gap show that the simulated gap factor deviates significantly from the experimentally found gap factor, and the Schneider and Weck model is therefore considered to be invalid for air gaps smaller than 2 meters. The experiments on a rod-plane and needle-plane show that the Feser equation best describes the breakdown strength of short rod-plane gaps, while the CRIEPI equation provides a conservative value suitable for clearance determination.

Experiments on the BRP busbar disconnector were conducted in the TU Delft high voltage laboratory to investigate the gap factor that may occur during maintenance. Four different gaps were tested: conductor-rod, pantograph-rod, pantograph-needle, and earthing contact-needle. The results show that the earthing contact-needle gap has the lowest gap factor of 1.20, and hence is the determining gap for the critical clearance. This critical clearance is found to be 45.6 cm, based on a worst-case risk evaluation. The currently enforced critical clearance by TenneT of 47.9 cm is considered to be adequate. A simulation is performed to study the minimum clearances related to the electric field. ... Read more

Shipboard microgrids are inherently weak systems due to their limited inertia and high impedance, making them prone to voltage and frequency fluctuations during faults and load changes. These challenges are further intensified by highly dynamic load conditions and the ongoing hybridization of shipboard power systems, where conventional diesel generators, functioning as synchronous generators, are increasingly being replaced by renewable energy sources (RES) and energy storage systems (ESS). As a result, the overall rotational inertia of the system is reduced, degrading its frequency stability.

This thesis proposes a method to emulate inertia using an ESS by implementing a virtual synchronous generator (VSG) control scheme. The ESS, interfaced through a power converter connected to the microgrid, replicates the kinetic energy behavior of a synchronous generator, providing both frequency and voltage support. A detailed Simulink model of a shipboard microgrid was developed, including converters, loads, synchronous generators, and grid-connected and islanded configurations. The VSG control scheme was designed and tuned based on system parameters, and its performance was evaluated through simulations and experimental testing.

Results demonstrate that a VSG control scheme based on the swing equation successfully provides virtual inertia, improving frequency stability by improving the frequency nadir and reducing the rate of change of frequency (RoCoF) by 85\%. In addition, the integration of integral Q–U droop control effectively regulates voltage, ensuring deviations remain within acceptable limits. The proposed control strategy is particularly beneficial for load variations exceeding 1 kVA/s and maintains stable operation even in islanded mode when synchronous generators are disconnected.

The study also identifies key design trade-offs, including the balance between frequency settling time and nadir, as well as between RoCoF reduction and power oscillations, which are influenced by the damping and inertia parameters. Similarly, voltage performance depends on the tuning of reactive power droop parameters, affecting both voltage deviation and dynamic response.

In conclusion, the use of VSG-based virtual inertia significantly enhances the stability of low-inertia shipboard microgrids, particularly in the context of increasing system hybridization. Future work should focus on optimal ESS selection, higher-level energy management strategies, and adaptive tuning of control parameters. ... Read more

Co-locating photovoltaic (PV) arrays and wind turbines can improve land-use efficiency, increase utilisation of grid infrastructure, and exploit complementary renewable energy resources. However, rotating wind turbine blades and yawing nacelles cast dynamic shadows on nearby PV modules, producing transient irradiance distributions that are difficult to capture with conventional static shading models.

This thesis presents a dynamic wind turbine shading framework developed within the PVMD Toolbox. The method extends the existing sensitivity-map workflow by introducing time-varying turbine orientations and a lookup-table approach for blade rotation. To reduce computational cost, a Spherical Half-Space Test is introduced, which transforms the shading calculation from a ray–geometry intersection problem into an angular containment problem on a unit sphere. Validation against the original ray-tracing implementation showed an annual energy-yield deviation of 0.09%, while reducing total simulation runtime by approximately 59×.

The framework was applied to a 240-module PV array at the Westermeerdijk PV–wind co-location case study in the Netherlands. Dynamic turbine shading generated rapidly varying irradiance distributions, repeated bypass-diode activation, changing module and string I–V characteristics, and multi-peak P–V curves. Nevertheless, the annual array-level impact remained limited: the total dynamic shading loss was approximately 2.0%.

The results show that dynamic modelling is essential for resolving transient operating conditions and spatial loss patterns, even when annual array-level yield losses are modest. ... Read more

This thesis details the design, implementation, and optimization of a single-switch circuit topology to drive a solid-state Tesla coil (SSTC). The goal of this project is to maximize the lengths of the discharges from the secondary coil given this switching topology. To achieve this, the thesis will look at the impact of a qausi-continuous wave (QCW) input on the discharges of the Tesla coil and compare these to the discharges of a staccato-ramped Tesla coil. A bus modulator approach was used to generate the QCW input, using a buck converter driven by a PWM signal with linearly increasing duty cycle to modulate a bus capacitor to create the QCW input signal. Additionally, this thesis analyzes and characterizes different high-power switch protection methodologies. These design optimizations combine to successfully generate discharges in excess of 40 cm with a 30 cm tall secondary coil. Experimental results revealed that there were no major differences in discharge length when comparing the QCW input to the staccato input when corrected to the same voltage. However, the results revealed that the duration of the QCW input did have a significant effect on the thickness and shape of the resulting discharges and the likeliness of internal discharges to take place. ... Read more

This work investigates whether the use of a ferrite core can improve the performance of a Slayer Exciter Solid State Tesla Coil. The main objective was to design, simulate, construct, and test a ferrite-core Tesla coil capable of producing long and straight discharges. COMSOL Multiphysics was used to calcu- late key electrical parameters, including inductance, capacitance, coupling factor, and AC resistance. These parameters were then used in an optimization routine to compare different coil geometries and determine a suitable final design.
The results show that increasing the inductance of the secondary coil with a ferrite core, allows smaller coil geometries to operate at suitable resonant frequencies; while keeping the resistance rela- tively low. Since the resonant frequency is directly affected by the increased inductance, the influence of operating frequency on discharge behavior was also investigated. Lower frequencies generally pro- duced longer sparks, but these discharges were often more branched. Frequencies around 350 kHz produced slightly shorter, but more stable and mostly unbranched sparks. The number of primary turns, coupling factor, and top-load size were also found to significantly affect the output performance.
An optimized ferrite-core design was constructed and compared with both air-core and alterna- tive ferrite-core coil designs. Experimental testing showed that the optimized design produced longer sparks than the comparable air-core design and performed better than the other tested ferrite-core con- figurations. The coil was able to produce sparks exceeding the target distance while operating within the required frequency range.
Overall, this work demonstrates that ferrite cores can be used effectively to improve compact Slayer Exciter Tesla coil designs and validates the usefulness of COMSOL-based optimization for high-voltage resonant systems. ... Read more

With the ever increasing global energy consumption, modern power electronics need to be more energy efficient, have a smaller form factor and have better thermal performance. To achieve this goal, Wide-Bandgap (WBG) semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN), are increasingly used instead of silicon (Si) in power applications such as electric vehicles and chargers. In particular GaN-based devices have a new breakthrough in the form of a vertically stacked GaN-Si cascode, which combines a normally-on GaN High-Electron-Mobility Transistor (HEMT) device with a normally-off Si Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) device stacked on top of the GaN HEMT device. Although the new configuration brought benefits to the table, it brought drawbacks to the thermal management of it: two heat sources stacked on top of each other. This causes both self-heating, but also coupled heating and combined with non-uniform heat dissipation across the device, the thermal behaviour becomes difficult to predict, which leads to suboptimal or over-engineered cooling solutions, reducing reliability and performance or increasing cost.

This thesis aimed to create insight and understanding of the heat dissipation and thermal behaviour inside a vertically stacked GaN-Si cascode. This was achieved by performing FEM simulations on the thermal behaviour in a vertically stacked GaN-Si cascode under different heat dissipation distributions, electrical characterisation of individual GaN HEMT and individual Si MOSFET dies to derive I-V and Ron characteristics, modelling of the heat dissipation and distribution using these electrical characteristics and thermal characterisation of a packaged vertically stacked GaN-Si cascode device using a Temperature-Sensitive Electrical Parameter (TSEP) and the Transient Dual Interface Method (TDIM) to derive Rthj-c under different operating conditions. It was found that the thermal performance was greatly influenced by the heat dissipation distribution and in turn the operating conditions (forward or reverse bias/conduction mode and how much current flows through the device). Based on these findings, recommendations were made to improve and extend the study on this topic, but also recommendations for future studies to improve packaging and cooling solutions. ... Read more

Modern DC power systems consist of a large number of power electronic converters and associated
equipment. On a ship, this power system is typically divided into two identical parts on the port and
starboard sides. These duplicated power systems are often isolated from each other to prevent a fault on one side from propagating to the other side and affecting the entire system, avoiding a total blackout on the ship. A major drawback of this two-split configuration, though, is that it is impossible to share power between both sides, reducing the functionality of the system. Therefore, to connect both sides while maintaining the safety of an isolated system, a solid-state circuit breaker (SSCB) can be used, which is reusable, unlike a fuse, and is able to interrupt the current much faster than a standard mechanical circuit breaker. However, due to the relative novelty of this component, the impact of mission profile variation and electrical disturbance on the SSCB lifetime is unknown.

To obtain the SSCB lifetime, mission profile analysis was performed, resulting in a lifetime as a consequence of wear-out failure mechanisms due to thermomechanical fatigue that would be used as the base case. Based on the mission profile, an SSCB model was designed following considerations for: Current interrupter topology, rated voltage/current of the components, peak voltage/current of the components, voltage clamping circuit, and the cooling. After choosing suitable components, their junction temperature profiles were obtained via iterative calculations with the power loss and the junction temperature using a Cauer model without thermal capacitance. With the rainflow counting algorithm, information regarding the cycle count, temperature swing, mean temperature, minimum temperature and the power-on-time per class was obtained. These were used in the CIPS with correction lifetime model, which obtained the cycle-to-failure of each relevant component. Transforming them into a reliability curve per component and multiplying them together resulted in the reliability curve of the SSCB. To estimate the impact on the lifetime of the electrical noise through the SSCB in comparison to the mission profile, a dynamic model was designed to take thermal capacitance into account, unlike the iterative model.

To quantify the impact of different stressors on the SSCB lifetime, changes in the mission profile, SSCB configuration and operational parameters compared to the base case are made. It was seen that the charging current, corresponding to changes in the maximum stress within the mission profile, has the most significant impact on the SSCB lifetime, while having a relatively minor drawback of a varying charging period. Bi-directional charging and changes in the coolant temperature were shown to have a relatively low impact on the lifetime. Load sharing between parallel components in a module significantly increased the lifetime, but at a cost of practically investing in a second SSCB. Concerning the impact of noise on SSCB lifetime with respect to the damage done by the mission profile, it can be concluded that high-frequency noise, such as the common-mode and differential-mode noise, has a negligible effect on the lifetime of the SSCB when solely focusing on wear-out mechanisms due to thermomechanical fatigue. ... Read more

This thesis presents the design of an AC bidirectional charger for automotive applications. Bidirectional charging technology has been introduced in the automobile market for a long time; however, the major reason for its low usage is the impact of this technology on the overall life of the battery pack. Therefore, this thesis proposes designing a power electronics optimized to minimize the impact on the battery life during V2L/V2G operations. To make an automotive AC charger, the ISO 5474-2:2024 standard is referred to get the requirements for this charger during forward power transfer to the battery and reverse power transfer from the battery. Based on these requirements and the input-output charger requirements, a simulation model of a 22kW charger is developed in MATLAB Simulink. This charger consists of a two-stage architecture, the first stage being a three-leg full bridge converter which acts as a power factor correction (PFC) converter during charging operation and an inverter during the discharging operation. The second stage consists of a DAB converter that allows bidirectional power flow while meeting the isolation requirement. To control the power flow during different modes of operation, closed-loop controls are developed for each mode. Depending on the mode of operation, different control loops are selected. The simulation model is run in different scenarios to check if it meets the requirements during all case scenarios, or not. Further, in order to validate the converter design, a 5kW hardware prototype is developed to validate the converter’s functionality and the closed-loop controls developed to meet the user requirements. The hardware prototype includes sizing of the components, designing the PCB, assembling the magnetic components, and integrating with PLECS-RT Box for measurement and control. ... Read more

The increasing integration of renewable energy sources and power electronic devices is changing the electricity grid, leading to widespread harmonic and supraharmonic distortions. Accurate measurement and calibration of current transformers (CTs) up to the 150 kHz range are essential for reliable power quality assessment and grid monitoring. However, traditional calibration approaches are limited in both bandwidth and practicality, particularly for high-current and high-frequency conditions.

This thesis develops and validates a broadband calibration methodology for CTs, enabling ratio and phase error characterization from 50 Hz to 150 kHz using a high-precision digital sampling ammeter (from a power analyser) as the core measurement instrument. The proposed system eliminates the need for auxiliary equipment and thus reduces component count, ultimately allowing for simplified broadband calibrations. An uncertainty budget is established with combined expanded uncertainties (k=2) for the measurement system of less than 10 ppm up to 10 kHz, and less than 100 ppm at 150 kHz for the secondary-to-secondary comparison method. This is an improvement over the previous state of the art for this setup, which had an uncertainty of 50 ppm and a maximum frequency of 10 kHz. For primary-to-secondary calibration, uncertainties remain below 110 ppm at the highest frequency, allowing for the further development of a reference current transformer.

The thesis systematically examines the influence of critical experimental factors, such as grounding configuration, shunt selection, conductor positioning, cabling, and measurement duration, on overall calibration accuracy and repeatability. Key findings include the importance of instrument warm-up, the impact of earth-loop currents, and practical considerations for shunt and cable selection for high-frequency application. The demonstrated approach provides a metrological foundation for future implementation of wideband CT accuracy classes and supports ongoing international efforts to establish traceable measurement infrastructure for power quality applications.

This work, carried out at the Dutch national metrology institute (VSL), aims to contribute to the goals of the European ADMIT project. ... Read more

This thesis develops a mathematical optimization model to optimize charging schedules and energy management for electrified aircraft at Rotterdam The Hague Airport (RTHA), addressing research gaps in adapting airport infrastructure for electric aviation. Based on a real-life flight schedule from 2019, the model determines a Battery Energy Storage System (BESS) size while minimizing operational costs, such as grid electricity, photovoltaic (PV) use, BESS degradation, and flight delay/cancellation penalties, while trying to maintain the schedule as closely as possible. Five electric aircraft types, ranging from a 2-seater flight school aircraft, to a 90-seater commercial aviation model, were considered with a Constant Power - Constant Voltage (CPCV) charging profile, alongside a detailed mission energy analysis. Seasonal simulation for January, April, July, and October 2019 showed delays averaging from 2 minutes in July while peaking at 45 in January, alongside three flight cancellations due to high energy demands. Optimized BESS sizes range from 7 MWh to 12 MWh. Optimization of the model showed a reduction of up to €500,000 weekly when compared to a baseline case. Sensitivity analysis showed that increasing the grid import limits from 3.5 MW to 5 MW gave better grid reliability, with less delays and cancellations, while a decrease to 2 MW showed increases in delay times and cancellations. When the export limit was reduced from 7.5 MW to 5 MW, the delays increased due to constrained energy offloading, while increasing it to 10 MW decreased the delays and cancellations by one. A 1 MWh BESS increase reduced cancellations by one and total delay time by up to 5 hours. Adjusting the turnaround times by ± 15 minutes demonstrated the model’s resilience to stricter turnaround times, but a 4-hour delay increase was present with extensions. The findings of the thesis show the critical role that BESS capacity and grid limits play in ensuring operational efficiency for the electric aviation infrastructures of the future, but also the cost and delay reduction by optimizing charging schedules. ... Read more

State estimation (SE) plays a critical role as a prerequisite for grid control and operation. However, the increasing penetration of distributed energy resources (DERs) and integrated energy systems (IES) introduces new challenges—such as unreliable pseudo-measurements and time-varying slack bus conditions—which make traditional methods like weighted least squares (WLS) increasingly difficult to apply. Moreover, DER integration leads to more frequent topological changes due to safety requirements and economic considerations. Yet, most existing machine learning methods for SE do not explicitly consider the topological changes. Therefore, this study evaluates three GNN-based models—GCN, GAT, and EvolveGCN—for state estimation in power grids under topological changes.

First, in the scenario without topological changes, where only the phase angle of the slack bus is fixed and noisy measurements are used, WLS performs worse than the three GNNs, indicating its susceptibility to interference under non-ideal conditions. Second, among the static GNNs, GAT performs best when topological changes are visible during training, but it cannot fully predict the voltage drops of unseen topological changes. GCN, on the other hand, demonstrates better generalization to unseen topologies and effectively suppress overfitting caused by noise. Third, although EvolveGCN is less accurate overall, it shows greater stability on nodes near PV buses, highlighting its potential to use historical information to enhance the time dimension when dealing with problems such as weak spatial correlation or local information loss.

These results suggest that GCN and GAT are potentially more suitable than WLS for SE in distribution grids with high DER penetration or IES. However, PV buses pose unique modeling challenges: they are physically but not numerically correlated with neighboring nodes, which make static GNNs hard to model their value change. Accurate estimation at PV buses is crucial, as they inject power into the system; in this context, EvolveGCN shows promise due to its stable predictions at these nodes. ... Read more

This thesis explores the integration of hydrogen ( H2) into a residential hybrid energy hub and presents results based on a case study of such an energy hub located at The Green Village, an open-field lab environment at Delft university of Technology. The study focusses on analysing real operational data from the energy hub to assess the performance, behaviour, and integration of the system. The energy hub combines photovoltaic (PV) power generation, battery storage, and hydrogen-based components including an AEM electrolyser, hydrogen storage, and a PEM fuel cell.
First, a detailed data analysis of the energy hub components is performed which lays a basis for the model of the energy hub. Particular attention was paid to the ramp-up and ramp-down dynamics, the power consumption and generation capabilities, and hydrogen consumption and generation of the electrolyser and fuel cell, as these affect the overall efficiency and responsiveness of the system. In addition, insights are given into the real capacity of the energy hub, and a comparison between the intended operation of the energy hub and the real operation is given. Following insights gained from the data analysis, a first step toward integrating machine learning into the Energy Management System (EMS) was taken. One potential improvement identified was the use of a machine learning algorithm that uses weather forecasts into EMS decision-making for the electrolyser. This study explores both binary classification and regression models using outside temperature and PV inverter power as inputs. Since inverter power correlates strongly with solar irradiance, these inputs were considered sufficient for developing a preliminary machine learning model aimed at enabling smarter control of the electrolyser.
A data-driven Simulink model of the energy hub was developed to simulate various operational scenarios, sizes, and edge cases. These simulations revealed how the behaviour of the system changes under different profiles of PV generation and residential demand, even when total energy consumption remains constant.
The data results create a solid foundation for the development of the Simulink model to run experiments with. The model has successfully demonstrated that the integration of hydrogen into the energy hub facilitates the coverage of seasonal energy demands, adding flexibility, and flattening the energy demands of the grid. However, it also showed that the system performance is highly sensitive to operating conditions and system sizing. Recommendations for future energy hub upgrades are provided through control optimisation and system sizing.
... Read more

This thesis explores how accurate state estimation can support Distribution System Operators (DSO) in managing MV grids. As the energy transition drives increasing complexity in electricity networks, more precise and reliable data is necessary for planning and operational decisions. Although state estimation offers a way to enhance data, DSOs struggle to implement it. The main objective of this thesis is to develop a general strategy for placing measurements to achieve accurate state estimation using as few measurements as possible.

Multiple cases were designed to assess the impact of specific measurement placement. A reference ”perfect case” network load scenario was created, and the values were corrupted using normally distributed noise, with standard deviations reflecting the expected accuracy of each measurement type. These noisy measurements were fed into the PandaPower Weighted Least Squares (WLS) state estimation algorithm, implemented in Python. The resulting state estimates were compared to the perfect case values to evaluate the state estimator’s accuracy and the placement strategy’s effect.

The results show that Power Injection Measurements (PIMs) primarily improve accuracy at the node where they are placed. In contrast, Medium Voltage Measurement Units (MVMUs) offer broader improvements across the entire feeder where they are installed. One strategic measurement location was identified based on financial grounds. Results also indicate that improving the accuracy of an inaccurate node is possible without improving its measurement, but requires widespread deployment elsewhere, which is rarely justifiable economically. Retrofitting stations solely for measurement purposes is generally not considered worthwhile.

The main focus should be on identifying the substations with the poorest measurement accuracy, typically pseudo-measurements. As a consequence, overall pseudo-measurement accuracy will also improve. This makes it more likely that the state estimates will fall within predetermined limits. The number of measurements that need to be placed depends on this predetermined limit.
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This thesis proposes an automated method for generating, executing, and assessing an interlocking test in a digital substation using a Python script designed for that specific purpose.

The goal is to expedite the process of performing the factory acceptance test (FAT) and the site acceptance test (SAT) of a substation automation system (SAS). This work requires a good understanding of the IEC 61850 standard, which is the international standard applicable to protection, automation and control systems (PACS). An account of the relevant parts from this series is therefore given, in addition to an overview of the benefits of digital substations in general.

The workflow for automatically generating a test case is based on previous work that made it possible to execute and assess an interlocking test automatically but not to generate a test case automatically for this purpose. Therefore, that is the main intention of the thesis.

It is done by having knowledge of the underlying interlocking logic of the system subject to test. From this logic, a test sequence can be created, where the position of the various switchgear is changed sequentially. This and the signal addresses for these devices are needed to generate a test case.

For additional robustness, the script can cross-check the signal addresses provided with the signal addresses in the substation configuration description (SCD) file and validate the final test case generated using a suitable schema. It is furthermore capable of generating a test case irrespective of the number of test steps, switching devices, and bays present in the substation.

A test file generated using this script is further validated by executing the test it describes in the SAS laboratory at the Norwegian University of Science and Technology (NTNU). This test was carried out remotely to showcase the possibilities of IEC 61850, which can be valuable for distant or offshore substations. Another benefit of this workflow is that it allows for the simulation of all devices of the test except for the device under test (DUT). This is particularly useful during commissioning if all devices have not yet been delivered or installed. In this case, the missing equipment can be compensated for by simulating the signals expected from these devices.

The final assessment of a test case relies upon the presence of the IEC 61850 LN (Logical Node) CILO (Control Interlocking). The output of this LN controls the interlock status of the DUT. If the DUT is allowed to operate, it sends a release signal or, alternatively, a blocking signal. In addition to this, information is gained based on the position of the switchgear under test to check that the CILO signal is consistent with the actual switchgear control command. This control command is known as the AddCause in IEC 61850 and will provide additional information on whether or not the DUT is interlocked.

Finally, the thesis will describe ongoing work in the IEC 61850 that could lead to a more streamlined approach and touch on the utilities' attitude towards SAS.

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This thesis investigates the impact of geometric, material, and operational parameters on the electromagnetic fields (EMFs) emitted by submarine power cables, particularly those used for offshore wind power transmission. The study is essential due to the growing deployment of offshore wind farms and the corresponding need for efficient submarine power transmission systems, combined with ecological concerns. The primary focus is on high-voltage alternating current (HVAC) cables, commonly used to connect offshore wind farms to the onshore grid. The rapid expansion of offshore wind power has highlighted significant ecological and environmental concerns, especially the effects of EMFs on marine life. Species such as elasmobranchs (sharks, rays, and skates) are highly sensitive to EMFs, making this an important area of research. The objective of this thesis is to develop guidelines for modeling EMFs from submarine power cables to aid ecological research, focusing on establishing effective parameters for EMF emission models. A literature review has shown that EMFs can impact marine animals’ navigation, predator-prey relationships, and embryo- genic development. Elasmobranchs, in particular, are vulnerable due to their sensitivity to EMFs. The review highlights the necessary accuracy levels for EMF models, focusing on HVAC cables. Starting with the basic physics including Maxwell’s equations, the Biot-Savart law, and the Lorentz force, followed by an outline of HVAC cable and transmission system design parameters, an understanding was created of the electromagnetic phenomena occurring in a submarine power cable. It was concluded that modeling EMFs requires considering current distribution along the conductor and metallic sheath, and the local interactions between cable components that result in shielding of the EMFs. A method from literature was used for predicting the longitudinal distribution of current along the conductor. The current distribution was affected by voltage and current transmission requirements, impedance, and the capacitive and inductive properties of the phases as well as reactive power compensation. Analyzing these parameters showed that all are crucial for accurate EMF modeling, as parameter changes within realistic ranges could result in differences over 10%. A significant part of this thesis examines the intensity of the metallic sheath currents. Modern HVAC cable designs use conductive polyethylene layers around the metallic sheaths, creating an electrical interface between them. This was conventionally assumed to dissipate circulating currents in the sheath, but this thesis questioned this belief. It was proven that some circulating currents remain and that induced currents were even unaffected by the conductive interface. The induced currents in the metallic sheath are shown to only be influenced by the conduction current and its design parameters, inductance, and resistance per unit length. Testing on the Borssele Alpha cable showed that sheath current for all standard operations was more than 12% of the conduction current. An analysis of the local impact of various design and operational parameters on EMF emissions was conducted using COMSOL Multiphysics. The Borssele Alpha 1 cable design served as a standard test case. The analysis highlighted the importance of the metallic sheath and even more so, the armor layer. The steel armor layer created a path of low reluctance, with geometric parameters and permeability playing significant roles. The effect of twist in the phases and armor wires on field emissions was also shown. The lay-length of the phases played a large role due to its effect on destructive interference between emissions of different phases. The armor lay-length had a considerable impact as well, possibly affecting the reluctance of the armor layer. The parameter analysis also confirmed the validity of an ultra-shortened section length in COMSOL, greatly reducing simulation time without impacting results. This research provides insights for developing accurate EMF emission predictions, aiding biologists and ecologists in evaluating the environmental impacts of offshore wind power infrastructure. This can guide the development of mitigation strategies and support sustainable expansion of renewable energy sources. Recommendations for future research include experimental testing of the sheath current model, further development of the transmission line method for the metallic sheath and developing better mitigation strategies. Unrelated to the main question is that in thermal analysis of comparable submarine power cable designs, the induced current must be incorporated, as it was unclear if this is the case. The findings of this thesis can significantly contribute to the sustainable growth of offshore wind power by addressing ecological concerns and improving the understanding of EMF effects on marine life. ... Read more

This thesis explores a Travelling Wave (TW) parameter fitting-based approach for both fault location and protection in a multi-terminal High Voltage Direct Current (HVDC) network. Utilizing a three terminal HVDC network model within a Real-Time Digital Simulator (RTDS) environment, a custom parameter fitting control component is developed using the Adaptive Multi-step Levenberg-Marquardt (AMLM) algorithm. For fault location, the methodology analyzes the line-mode backwards travelling voltage wave (Vb1) following an internal DC cable fault. Despite the successful integration of the AMLM parameter fitting algorithm into the real time environment, the achieved average absolute error of 9.80% (29.4 km) for faults spaced 50 km along a 300 km cable was above the acceptable threshold, rendering the proposed
method impractical for precise fault location. Improvements through specific signal truncation and optimal cable parameter selection reduced the error to 5.15% (15.45 km), which remains insufficient for practical applications. In contrast, the TW parameter fitting method proves highly effective for fast and fully selective protection. The protection scheme accurately discriminates between internal and external faults using the Vb1 signal and determines fault types through Vb0 signal analysis. Extensive testing revealed a fault detection rate of 100%, with an overall accuracy of 99.91% for fault resistances up to 200Ω. Severe internal faults are isolated in 1.68 milliseconds, while non-severe internal faults are typically isolated in 3.84 milliseconds. The method completely eliminates relay deadzone, providing robust performance even under noisy conditions with an accuracy of 99.85% for faults with an impedance up to 50Ω. These findings highlight the potential of the TW parameter fitting approach to significantly enhance the reliability and promptness of fault isolation in HVDC systems, while offering insights into the challenges and limitations of fault location accuracy on a real time platform. ... Read more

Unwanted breakdown of insulation is one of the primary challenges affecting the reliability of power systems. Liquid insulation is commonly used in power grids and subsea installations due to its preferred qualities, such as heat transfer and safety. Some insulating liquids have been available since the earliest times, and some have been proven to be harmful to humans, animals, and the environment. Consequently, the search for better candidates has always been ongoing. Unfortunately, the knowledge of the quality of the insulating liquids is insufficient since numerous phenomena related to electrical discharge and breakdown in insulating liquids happen unexpectedly, often surprising the personnel involved. Therefore, gaining a deep understanding of the breakdown physics of these liquids and mechanisms leading to the degradation of their dielectric properties is crucial. This understanding ensures that the new replacements are suitable for specific equipment. Partial discharge (PD), as one of the initial stages before breakdown and a major player in ageing the insulators, is the main focus of this work. One way to monitor a liquid’s insulation quality is through the Partial Discharge Inception Voltage (PDIV)
level. Based on PDIV measurements, there are defined standards, such as IEC 61294. This work is focused on investigating the behavior of different types of liquids under the AC voltage stress above and below the PDIV level to determine if the defined standards reflect the dielectric characteristics of each liquid properly. Three liquids have been examined, including two candidates from commonly used insulating liquids in electrical installations. Tests are performed in a needle-plane geometry under high-voltage AC stress. The same liquids and geometry have been used multiple times in previous studies under lower frequency AC voltage, yielding unexpected results. Therefore, this study aims to investigate deeper by testing the liquids at higher frequencies and comparing observations with previous results. The experimental setup used for this work includes a 20 kV resonance voltage source, and the needle-plane gap distance is 20 mm. The current flow from the plane to the needle is mostly capacitive in the range up to 100 nA, but space charges are proved to play a major role in the conductive component of the current. PD behavior has been found to relate to molecular structure and, in some cases, to the previous stresses, likely due to residual ions remaining from previous cycles. The presence and nature of space charges have been investigated carefully by testing liquids at higher frequencies below and above the PDIV level. Further, the test setup was facilitated, and half-cycle voltages were applied to involve only one polarity of space charges, and the differences were observed. Another part of this work involved the optical PD measurement method, which utilized two photomultiplier tubes (PMTs) and a coincidence circuit to filter out ambient dark noise. This method was employed alongside the well-known charge acquisition method to detect the initial PD pulses in the liquid. The results demonstrated a noteworthy difference between the two methods, prompting further investigation.
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Drones -- small (or not so small) remotely controlled flying devices -- are seeing rapidly increasing use in many fields of application and human activities ranging from recreation, competitive sports, last-mile logistics, espionage, exploration, to media production, and even warfare. The abundance of these devices brings with it the risk of them becoming an audible nuisance due to the high pitched noise produced by their surface-mount (SM) PMSMs.
The acoustic noise produced in these motors is the product of multiple factors, but chief among them is the vibration of the motor's external shell, which is the stator for internal rotor type motors and the rotor for external rotor type. This shell vibrates in various oscillation modes as a result of the magnetic forces acting on it, which are an inevitable result of the motor's internal magnetic field and the armature currents that produce them.
This motivates research effort into reducing this noise through modulation or control strategies employed by the inverter powering the motor. In order to develop a control model, first the motor itself must be understood. In this thesis, the electromagnetic aspect of surface-mount-PMSMs will be developed, i.e. an analytical model will be established of the air gap magnetic field in SM-PMSMs.
First, the armature reaction field for arbitrary winding types will be derived, followed by a detailed derivation of equations typically used to model the rotor magnets in SM-PMSMs. A derivation of the effect of stator slotting on the air gap magnetc field will be provided, and concluded with a combination of the three previously mentioned aspects, and the dimension of time will be incorporated in the model.
Accompanying this thesis will be a set of MATLAB code that will be made publicly available for research and instruction in academia. ... Read more