· · · Institutional Repository

In the current society, energy is getting more and more important and one of the most important energy carriers is electricity. TenneT TSO b.v, being the Dutch Transmission System Operator and the administrator of the national transmission grid is responsible not only for the continuity of the electricity supply, but also for the reliability and security of the grid. The growing demand for electricity and the liberalisation of the energy market have both contributed to a higher demand for transmission capacity. Energy is being transmitted over longer distances and existing power lines are deemed insufficient. To retain the current reliability and availability, investments have to be made. One of these investments is the project Randstad 380, which aims to ensure the supply and availability of electricity to the most densely populated region in The Netherlands, called the Randstad. In conjunction with government bodies and interest groups, TenneT has decided to implement 20 km of this connection using an underground cable. The study analyses the effect on the local steady-state voltage profile and reactive power balance for a partial implementation of the Randstad 380 project using an EHV AC underground cable system. The study also serves as an introduction to the Randstad 380 project, with a focus on the technical considerations and concerns related to the steady-state operation of underground cables at extra high voltage (EHV) level. The proposed underground cable system is unique in the world compared to existing EHV AC cable systems in terms of power rating and required total cable length.

The concentrated winding is proposed to replace the distributed winding due to the advantages in a manufacturing process. It is easily wounded by a machine in the former and the impregmentation process that can be carried out separately for each individual coil. These advantages can lead to the automation process in winding processes, reduced time and cost in generator manufacturing. One of the problems of the concentrated winding generator is eddy current losses due to the fact that air gap flux in the concentrated winding contains much more harmonics compared to the distributed winding. These losses should be kept in within the acceptable level of heat removing capability of the generator. Otherwise, higher temperature of magnet could influences the remanence flux of the permanent magnet. In this study, two methods of eddy current losses calculation, analytical and finite element (FE), are presented. Finite Element Method has some advantages due its capability to handle the geometric problem and non linear material which is difficult to incorporate in analytical calculation

The HCPS group of Electrical Power Engineering department has a Real-Time Digital Simulator (RTDS) for the study and analysis of power system phenomena. RTDS helps to perform real-time simulations that allow the user to interact with the grid model in real time. During this Master thesis work the existing Noord-Holland grid is implemented in RTDS. This model is verified by other software models of the Noord-Holland grid. The existing grid model is expanded with a large wind power plant. Subsequently the dynamic behaviour of the grid with large wind power input is investigated. For future works this model can be used as a test grid.

This thesis deals with characterization of epoxy nanocomposites with different filler types and filler percentages by performing space charge measurements and DC ramp breakdown tests. The space charge measurements were performed at three field levels (10, 15, and 18 kV/mm) using the PEA method. The results were then analyzed. In addition to this, DC ramp breakdown tests at a rate of rise of 500 V/s were performed on the samples. The Weibull parameters for each sample type were then determined from the breakdown results.

The ambient conditions could influence the breakdown strength of gas insulated substation. It is important to check if this influence will put the GIS into severe condition, especially in the presence of protrusion. A risk assessment is thus important for making decision if the GIS is safe to be operated.

The short circuit arc is the most dominant fault in the power system that leads to single phase to ground fault. South Sumatera 150 kV system in Indonesia consists of two different string insulator types in the transmission line, with and without arching horn. In this study, some fault situations in that system is reconstructed by using ATP Draw – EMTP software. As the main part of the simulation, the fault arc is represented in the MODELS language form. The voltage and current terminal results are compared with the measurements to obtain the primary and secondary arc parameter for two types of string insulator. At the end, the fix arc models are used in different simulation cases to evaluate existing distance protection setting by using impedance extraction in ISA TDMS software and recursive DFS in MODELS.

The thesis describes the modeling of the internal faults in three-phase three-winding power transformer related to the differential relay protection behavior due to those faults. This transformer model is based on the mutually coupled [RL] matrix and entirely compatible with ATP/EMTP software. The model uses the real power transformer and the simulation is based on the real condition in the substation. The results enable one to understand the current waveform when the turn-to-earth and turn-to-turn fault occur at the transformer. The transformer differential relay protection operation and characteristics due to those internal faults are also studied.

In this study, three artificial defects that represent different type of installation defects are observed by electric field simulation and different energizing and PD detection method. Several measurement issues related to the un-conventional PD measurement are also investigated. The investigation of all these important factors is performed to provide a better understanding and performance of PD detection in after-laying test of HV cable system.

This thesis gives a description of diagnosing life consumption and future life estimation of oil-impregnated paper insulated cable by using dielectric loss value. Dielectric loss values were investigated at different temperatures and different electrical field intensities in the laboratory. Based on laboratory measurements, a program was built; it can calculate the life consumption of paper oil-impregnated insulation by on-site dielectric loss measurements. Thermal aging was also taken into account for life consumption calculation in the program as an additional criterion. After that, future life estimation was calculated based on the result of life consumption and thermal aging theory in the program.

The Dutch electricity grid is considered one of the most reliable in the world. However in the near and far future, significant changes will occur, that will endanger its stability, reliability and safety. Introduction of an embedded wireless sensor network, to determine the state of the power system at any time, in order to cope with these changes, is a solution still absent in the actual grid. However, wireless data transfer is vulnerable to any type of electromagnetic radiation. In this thesis work, the effects of interference sources in substations are investigated. A model of the wireless channel for substation’s environments is provided and suggestions are made for robust transmission technologies.

Direct drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered. In the beginning, the thesis discusses the problems of direct drive generators in large wind turbines, introduces a hybrid concept of active magnetic bearings, gives a demonstrator of magnetic bearings used in this project, and presents a basic control system of active magnetic bearings. For the purpose of support such magnetic bearings in wind turbines, this thesis gives a complete control system. This control system includes electrical circuits and decentralized control method. The implementation of the electrical circuits is distributed into two PCBs. The decentralized control method is designed with six PID controllers. Finally, in order to improve the stability of the system, the H-infinity control method is suggested to magnetic bearing system in wind turbine applications.

The principle of Inductive Power Transfer (IPT) is very old but it is rarely used for transferring power from source to load via a medium. This is because normally the medium restricts the power transfer due to losses or the shielding effects. However, for low energy applications, an acceptable amount of power could be transferred from the source to the load. This paper aims at finding the amount of power transferred, the losses and efficiency for a given configuration. First, an analytical model is constructed. This analytical model involves equations governing the mechanism of IPT. Second, the paper deals with experimental validation of the derived analytical model. A set up was made in the laboratory and certain experiments were performed for the comparison with analytical model. Experiments performed at different frequencies validated the analytical model but with few discrepancies, which are due to the assumptions made in the analytical model.

Nowadays, the amount of distributed generation (DG) units is increasing rapidly. Most of them are represented by microturbines, combined heat and power (CHP) plants and synchronous generator. At this moment, IEEE 1547 standard states that DG clearing time should be based on the during-fault voltage range. However, DG units will be required to be still connected to the grid during fault period in the future due to high penetration level. This will influence the behavior of network protection schemes. In this study, the impact of DG on protection schemes in Medium Voltage (MV) networks is investigated. The case study network with DG connected is modeled in Matlab/Simulink. Fault simulations at various locations are investigated. Voltage profiles and protective device performance from several case studies are presented and discussed.

A hybrid power system (HPS) which consists of diesel Genset, PV-arrays and wind turbines with energy storing and power electronic devices is discussed in this paper. An inventory of different connection topologies is made for some of the sources generate AC power and others generate DC power. By comparative study on the system efficiency, the Mixed-coupled HPS is found to be the best layout and this layout is used for further investigation. By considering AC-load demand, solar irradiation and wind speed profiles of a typical site, the sizing approaches of the system elements are developed for the HPS. For the selected layout, eleven innovative Power Management Strategies (PMSs) are defined; and for each PMS Mathematical models are derived based on the power balance between the supply and the demand sides, charging/ discharging control of the battery and switching controls for the Genset. The different HPSs are modeled using MATLAB/Simulink blocks and simulation results are analyzed. The different PMSs result to different sizing of system elements, power sharing, fuel consumption& environmental impacts, and cycles of batteries in the lifetime of the system. Finally, the hybrid system of each PMS is investigated for its cost competitiveness and environmental impacts by taking the economical aspects and fuel consumption into consideration. It is found that RESs and/or HPSs are cost competitive over the system life, in spite of the huge initial capital costs, for the variable costs of the Genset overshadows its low initial capital investment .

The electrical power system generates and supplies electric energy to consumers and it must operate in a safe manner at all times. Despite its good performance, disturbances such as the occurrence of short circuits can always take place. Because short circuits cannot be prevented, the system must be able to recognize them and take corrective action. This is done by the different protective systems, which are implemented throughout the power system. Stedin is a Distribution System Operator (DSO) in the western part of the Netherlands. Stedin experienced that in case of short circuits in certain complex grid structures, the fault is not always detected adequately by the protective system and this results in mal-operation of the protection relays. Firstly, the cause of incorrect operation of the protective system in such network structures is studied in this thesis project. Secondly, there are certain condition strategies studied to try to prevent incorrect operation of the protective system in such networks. These include changes in the network structure, readjustments of protection relay settings and alternative protective schemes.

This thesis is aimed to analyze the effect of test parameters on DRM results from OLTC and its implementation in the condition assessment. Two test parameters were selected to be observed, which are test current and circuit resistance. Their amplitude was varied during the measurements and experiments in the laboratory as well as in the field (substation). To quantify the measurement results, an analytical tool was introduced. Its purpose is to convert the DRM results into 4 parameters. They are plotted as curves, in such a way that particular behaviours of the curves determine the influence of the test parameters. Further on, the influence of test parameters has been utilized to determine an optimum level of test parameter. It is used to conduct the measurement to gain reliable results. Then with the help of three dimensional classification system, the actual condition of OLTC can be identified. It shall simplify the condition assessment of OLTC.

This project is part of the project “GenPowerBox”; this is a project of the company Mastervolt, realized by Whisper Power. The objective of this project is to develop a compact and noiseless energy management system for use on board of yachts. The “GenPowerBox” system is composed of a battery and a generator set; consisting of a diesel engine and a Permanent Magnet Synchronous Generator (PMSG). This MSc project is focused on the Permanent Magnet generator. The generator is integrated in the flywheel of the diesel engine. The main objective of this project is to determinate the most suitable generator for the application on yachts. Another goal is to validate the models of different generators designs. These models represent the induced voltage, different losses and the efficiency of the generator. This is done by performing several tests on different prototypes of both 3kW and 9kW generators. The measurements results are then compared with the simulated results. The distinctions between the designs consist of: - The type of the permanent magnets (ferrite or NdFeB), - The combination of number of poles and slots (2/3 or 8/9), and - The type of the slots (Open or semi-closed slots).

The purpose of this thesis is to present a precise analytical method for modeling the rotor induced eddy current losses in the surface mounted PM machine. First, an analytical insight in to the eddy current loss in each layer of the rotor has been developed. Next, major design parameters that have the most important effects on the rotor losses have been identified.