High Voltage
Volume 2, Issue 4, December 2017
Volumes & issues:
Volume 2, Issue 4
December 2017
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- Author(s): Bin Chang ; Oliver Cwikowski ; Mike Barnes ; Roger Shuttleworth ; Antony Beddard ; Paul Coventry
- Source: High Voltage, Volume 2, Issue 4, p. 211 –219
- DOI: 10.1049/hve.2017.0024
- Type: Article
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Multi-terminal voltage-sourced converters (VSC) high-voltage direct current (HVDC) transmission system is expected to play a vital role in future power systems. Compared with ac power transmission, dc transmission is more vulnerable to faults due to low dc-side impedances and sensitive power electronics in the converters. Dc protection issues must be tackled before any multi-terminal VSC-HVDC grid can be built. The multi-terminal VSC-HVDC system is studied in detail using switching models for two-level converters, detailed equivalent models for the modular multi-level converters, detailed hybrid circuit breaker switching models and frequency-dependent phase models for dc cables. Using such high-fidelity system models, a systematic study of HVDC fault protection methodologies in more detail than previous studies is conducted. This is the first comprehensive study that includes pre-emptive circuit breaker operation. The results presented in this study underline the benefits of such a detailed treatment of the breaker, and of considering it as part of a fast power electronics system rather than isolated dc equipment. The study identifies the best existing fault detection method and tests it extensively. In order to further improve post-fault system recovery response, which is a key but often neglected part of previous studies, a novel bump-less transfer control has been implemented in the converters.
- Author(s): Zili Zhang ; Ping He ; Jinyan Zhang ; Yikui Li ; Qiuliang Wang
- Source: High Voltage, Volume 2, Issue 4, p. 220 –232
- DOI: 10.1049/hve.2017.0082
- Type: Article
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220
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In the past few decades, the multifunctional magnetic drug carrier based on the magnetic nanoparticles and high magnetic field has been intensively researched. The magnetic drug carrier can be targeted to the tumour area not only by the chemical protocol but also by the physical one (external field). In this review, the authors first briefly discuss the fabrication process of magnetic drug carriers, which includes the synthesis of magnetic nanoparticles, fabrication of magnetic drug carriers and conjugation of anti-tumour agents. Then different targeted protocols have been summarised, including passive targeting, biochemical active targeting and biophysical active targeting namely magnetic targeting (MT). Multiple MT results both in vitro and in vivo are introduced, in which two unconventional cases are emphasised and described. The first MT clinical research with 14 peoples was performed in the last century. A 0.5–0.8 T permanent magnet was attached to the tumour area when magnetic particles conjugated with epirubicin were injected. The side effect of epirubicin had been decreased, and the four patients showed the decreasing of a tumour which proved the feasibility of MT. Different from other targeting protocols, MT needs an extra external magnetic field. So various types of MT instruments have been shown in the final part of this review, including a single strong magnetic field, homemade electronic solenoid coil assay and commercial magnetic resonance imaging.
Review of different fault detection methods and their impact on pre-emptive VSC-HVDC dc protection performance
Recent advances in magnetic targeting based on high magnetic field and magnetic particles
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- Author(s): Thomas Lagier ; Philippe Ladoux ; Piotr Dworakowski
- Source: High Voltage, Volume 2, Issue 4, p. 233 –243
- DOI: 10.1049/hve.2017.0070
- Type: Article
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High-voltage direct current (HVDC) is more and more often implemented for long distance electrical energy transmission, especially for off-shore wind farms. In this study, a full DC off-shore wind farm, which requires a high-power and high-voltage DC/DC converter, is considered. In order to reduce the size of the converter, the trend is to increase operating frequency. Silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) are becoming industrially available and give scope for the realisation of high-performance DC/DC converters based on modular architectures. This study presents a prospective analysis of the potential of such devices in HVDC power systems. Considering the characteristics of Si insulated-gate bipolar transistor and SiC MOSFET power modules, two DC/DC converter topologies are compared in terms of losses and number of components. In conclusion, a study of the efficiency based on converter energy loss is presented.
- Author(s): Mahmoud Dhimish ; Violeta Holmes ; Bruce Mehrdadi ; Mark Dales
- Source: High Voltage, Volume 2, Issue 4, p. 244 –252
- DOI: 10.1049/hve.2017.0044
- Type: Article
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244
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This study proposes a fault detection algorithm based on the analysis of the theoretical curves which describe the behaviour of an existing grid-connected photovoltaic (GCPV) system. For a given set of working conditions, a number of attributes such as voltage ratio (VR) and power ratio (PR) are simulated using virtual instrumentation LabVIEW software. Furthermore, a third-order polynomial function is used to generate two detection limits (high and low limits) for the VR and PR ratios. The high and low detection limits are compared with real-time long-term data measurements from a 1.1 kWp GCPV system installed at the University of Huddersfield, United Kingdom. Furthermore, samples that lie out of the detecting limits are processed by a fuzzy logic classification system which consists of two inputs (VR and PR) and one output membership function. The obtained results show that the fault detection algorithm accurately detects different faults occurring in the PV system. The maximum detection accuracy (DA) of the proposed algorithm before considering the fuzzy logic system is equal to 95.27%; however, the fault DA is increased up to a minimum value of 98.8% after considering the fuzzy logic system.
- Author(s): Gbah Kone ; Christophe Volat ; Hassan Ezzaidi
- Source: High Voltage, Volume 2, Issue 4, p. 253 –260
- DOI: 10.1049/hve.2016.0096
- Type: Article
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253
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This paper presents an exhaustive study of numerical investigations based on three-dimensional finite-element method modelling of several non-ceramic insulators of 69, 110 and 230 kV having different internal semi-conductive defects in terms of size and position. The internal defects were positioned close to the high-voltage electrode, the ground electrode and at floating potential. The simulations effected on the distortion of the axial and radial E-field components close to the insulator shank between sheds. The results obtained showed that the radial E-field component is more sensitive to the presence of an internal defect as it shows a greater distortion in presence of the defect. It was also observed that the E-field component distortion increases with longer internal defect and that this increase is particularly important for a defect at floating potential. Moreover, it was demonstrated that the length of the insulator, for a defect of constant length, has no significant influence on the E-field component distortion. Finally, the results demonstrated that the presence of a grading ring, as used on the 230 kV insulator, does not have any influence on the E-field component distortion, independently of the defect position.
- Author(s): Xiaolan Gu ; Yong Cui ; Qiusheng Wang ; Haiwen Yuan ; Luxing Zhao ; Guifang Wu
- Source: High Voltage, Volume 2, Issue 4, p. 261 –266
- DOI: 10.1049/hve.2017.0085
- Type: Article
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261
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The electric field environment under high-voltage direct current (HVDC) transmission lines is an important design consideration. In the wireless sensor networks for electric field measurement system under the HVDC transmission lines, it is necessary to obtain the electric field distribution with multiple sensors. The accurate localisation of sensing nodes is essential to the analysis of measurement results. However, most current techniques are limited to constant measurement environment with fixed and known path-loss exponent. Here, the authors report a localisation method based on received signal strength indication with unknown path-loss exponent for the localisation of one-dimensional linear topology wireless networks in the electric field measurement system. The optimisation method is utilised to obtain the optimal pass-loss parameter without involving the previous environment parameters. Afterwards, simulations are employed to demonstrate the feasibility and the effectiveness of the proposed method by comparing with other methods.
- Author(s): Sujana Dasara and Vineet Prakash Mishra
- Source: High Voltage, Volume 2, Issue 4, p. 267 –273
- DOI: 10.1049/hve.2016.0090
- Type: Article
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267
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Leakage flux generated in the power transformers cause stray losses in metallic parts of the transformer. Stray losses largely affect the transformer hot spot which leads to thermal failure. It is necessary to mitigate the impact of leakage flux on metallic parts by employing magnetic shunts and eddy current shields. Preeminently clamping structures like flitch plate and end frames experience substantial losses, hence combinations of shielding can be used for better loss reduction. In this study, a case study is performed on a 315 MVA, 420/27 kV single-phase generator power transformer. This work is based on coupled three-dimensional (3D) finite-element analysis (FEA) of the transformer model. A new type of magnetic shunt is explored; also different design combinations of shielding are specified in this work for efficient mitigation of hot spots as well as tank walls.
- Author(s): Seyedreza Aali
- Source: High Voltage, Volume 2, Issue 4, p. 274 –279
- DOI: 10.1049/hve.2016.0026
- Type: Article
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p.
274
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A shunt active DC filter (ADF) with current injection suppresses current harmonics from high-voltage DC (HVDC) transmission systems. This paper proposes an ADF based on artificial neural networks (ANNs). The ANNs are very generic, accurate and convenient statistical models. They can emulate numerical model components, which are of complicated non-linear input/output relationships. The neural network in the control system of the ADF estimates the harmonic components of the load current and voltage. The ANN is trained offline using databases from the conventional controller. The simulation is carried out by MATLAB/Simulink and its results confirm that the proposed controller can offer better performance such as suppression of the current variations (current harmonics) in the DC-transmission line.
Potential of silicon carbide MOSFETs in the DC/DC converters for future HVDC offshore wind farms
Multi-layer photovoltaic fault detection algorithm
Numerical investigation of electric field distortion induced by internal defects in composite insulators
Received signal strength indication-based localisation method with unknown path-loss exponent for HVDC electric field measurement
Shielding measures of power transformer to mitigate stray loss and hot spot through coupled 3D FEA
Shunt active DC filter based on intelligence controller for HVDC link
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