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  • 1.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Amalanathan, A. J.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Babu, Myneni Sukesh
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Sarathi, R.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Kumar, Ganesh
    Indian Inst Technol Madras IIT Madras, Dept Ocean Engn, Chennai 600036, Tamil Nadu, India..
    Sangwai, Jitendra S.
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Experimental Study and ANN Analysis of Rheological Behavior of Mineral Oil-Based SiO2 Nanofluids2022In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 29, no 3, p. 956-964Article in journal (Refereed)
    Abstract [en]

    This work reports an experimental and theoretical analysis of the rheological properties of mineral oil-based SiO2 nanofluid for their potential applications in transformer insulation. The flow electrification mechanism on the nanofluids with different surfactants such as cetyl trimethyl ammonium bromide (CTAB), oleic acid, and Span 80 is studied using a spinning disk technique. The results show a higher streaming current for the nanofluids with CTAB as a surfactant compared to oleic acid and Span 80. The rheological behavior of nanofluids is explored with the double gap concentric cylinder geometry. The variation of shear stress with shear rate follows a power law relationship along with a yield stress observed for all the nanofluids. A transition is seen from storage modulus to dominant loss modulus for the nanofluids during the frequency sweep analysis, whereas no transition is observed in the case of mineral oil. In addition, regression analysis using artificial neural network (ANN) algorithms are performed on the experimentally measured viscosity of the nanofluids in order to estimate theoretical parameters and provide insights into the streaming current formation. The desirable rheological characteristics of nanofluids are identified for achieving enhanced insulation performance in transformers.

  • 2.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Amalanathan, A. J.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Sarathi, R.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of Magnetic Field on Corona Discharge Behavior of Mineral Oil Under AC Voltage2022In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 29, no 4, p. 1417-1424Article in journal (Refereed)
    Abstract [en]

    This article reports an experimental investigation of the impact of magnetic field on corona discharge activity in mineral oil, using both ultrahigh-frequency (UHF) and fluorescence techniques under ac voltage. The results show that corona inception voltage (CIV) increased under ac voltage with varying harmonic frequencies without considering any phase shift and reduced marginally under magnetic field. In addition, the impact of the magnetic field shifted the dominating frequency of the UHF signal (0.9 GHz) obtained under ac voltage toward lower frequencies (0.3 and 0.6 GHz). Under high magnetic fields, the parameters such as rise time, fall time, and pulsewidth of the fluorescence signal increased in its magnitude compared to its effect without a magnetic field. Also, using both the UHF sensor and the fluorescence sensor, there was no clear difference in the phase-resolved partial discharge (PRPD) pattern caused by corona discharge (with and without magnetic field). Furthermore, the number of discharges is observed to be high under the impact of harmonic ac voltages with third- and seventh-order containing total harmonic distortions (THDs) of 4% and 40%.

  • 3.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Amalanathan, A. J.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Sarathi, R.
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Srinivasan, Balaji
    Indian Inst Technol Madras, Dept Elect Engn, Chennai 600036, Tamil Nadu, India..
    Gardas, Ramesh L.
    Indian Inst Technol Madras, Dept Chem, Chennai 600036, Tamil Nadu, India..
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of Surfactants on the Electrical and Rheological Aspects of Silica Based Synthetic Ester Nanofluids2022In: IEEE Access, E-ISSN 2169-3536, Vol. 10, p. 18192-18200Article in journal (Refereed)
    Abstract [en]

    This study reports experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica based synthetic ester nanofluids. The positive and negative potential observed for the ionic (CTAB) and non-ionic surfactant (Span 80) from zeta potential analysis indicates an improved stability. The optimization of nanofillers and surfactants is performed considering the corona inception voltage measured using ultra high frequency (UHF) technique and fluorescent fiber. Rheological analysis shows no significant variation of properties with shear rate, implying Newtonian behavior even with the addition of surfactant. In addition, the permittivity of the nanofluid is not much affected by adding surfactant but a marginal variation is noticed in the loss tangent with the effect of temperature. The fluorescence spectroscopy shows no change in the emission wavelength with the addition of silica nanofiller and surfactants. Flow electrification studies indicate an increase in the streaming current with the rotation speed and temperature, with a higher current magnitude observed in the case of nanofluids.

  • 4.
    Amizhtan, S. K.
    et al.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, India..
    Sarathi, R.
    Indian Inst Technol Madras IIT Madras, Dept Elect Engn, Chennai 600036, India..
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Study on Conduction Mechanism in Corrosive Transformer Oil and its Reclamation Properties2023In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 30, no 5, p. 2232-2239Article in journal (Refereed)
    Abstract [en]

    This work deals with the effect of oil reclamation on the conduction mechanism and dielectric aspects of accelerated thermally aged transformer mineral oil. The reclamation is a treatment with Fuller's earth (FE) adsorbent to remove corrosive sulfur compounds and other contaminants formed during thermal aging. The properties of the oil are compared between different stages of the treatment. Corona (partial discharge) inception is identified by the optical fluorescent fiber technique. The results show an increased corona inception voltage after treatment. Dielectric response spectroscopy (DRS) showed a lower loss factor and electrical conductivity after treatment. The conduction mechanism is measured under uniform and nonuniform electric fields with variations in applied voltage magnitude. The conduction mechanism at a uniform electric field (low E) is studied using the polarity reversal technique to estimate the respective ionic motilities in the fluid. The apparent mobility of ions, conductivity, ionic radius, and concentration from the oil are found to reduce on reclamation. In addition, the conduction mechanism for a higher electric field is simulated by the current-voltage characteristic in nonuniform conditions and the slope determines the ionic mobility of the fluid.

  • 5.
    Amizhtan, S. K.
    et al.
    Indian Institute of Technology Madras, Department of Electrical Engineering, Chennai, India, 600036.
    Sarathi, R.
    Indian Institute of Technology Madras, Department of Electrical Engineering, Chennai, India, 600036.
    Vinu, R.
    Indian Institute of Technology Madras, Department of Chemical Engineering, Chennai, India, 600036.
    Edin, Hans Ezz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Investigation on Carbon particle formation with Electro-Thermal ageing of Transformer oil2023In: ICDL 2023 - 22nd IEEE International Conference on Dielectric Liquids, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper (Refereed)
    Abstract [en]

    Present work deals with accelerated electrical and thermal stress on transformer oil and its characteristic variation on Fuller's earth (FE) reclamation. The influence of carbon particles in the fluid, its role on thermal ageing characteristics can be understood by electrical characterization. Reclamation of insulation fluid extends the lifetime and reliability of the transformer over the year of operation. The average particle size of carbon particles on electrical breakdown are in the range of 644 nm. Dielectric response spectroscopy (DRS) which identifies the conductivity and relative permittivity variation with the effect multi-stress ageing. Conduction mechanism with higher electric field is simulated by current-voltage (IV) characteristics using non-uniform field configuration to derive the ionic mobility of the liquid. Dissolved decayed products and turbidity showed drastic enhancement with multi-stress ageing than the thermally aged specimen. Reclamation with fuller earth treatment removes the carbon traces and ageing by-products in the fluid regaining its relative dielectric performances. Rheological aspects with viscosity indicates the ageing by-products build and also its characteristic variation on the reclamation process.

  • 6. Castro, L. C.
    et al.
    Oslinger, J. L.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES).
    Wåhlander, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dielectric and Physico-chemical Properties of Epoxy-Mica Insulation During Thermoelectric Aging2015In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 22, no 6, p. 3107-3117Article in journal (Refereed)
    Abstract [en]

    Three stator bars were subjected to 1142 hours of thermoelectric aging. At intervals during this time, the aging of the insulation was investigated by capacitance (C) and dissipation factor (DF) measurements and by the physicochemical techniques of infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). Results indicated different degradation paths under discharge conditions, where the volume of voids within the insulation played a major role. Postcuring reactions were predominant during the first aging cycles. Such reactions were detected as reductions in capacitance and dissipation factor parameters, as a depletion of the chemical group epoxide at the absorption band 909 cm(-1) as measured by FTIR, and as an increase of the glass transition temperature (T-g) of the epoxy resin. Since the postcuring reactions occur globally in the insulation, they were detected by both dielectric and physicochemical techniques. With the advance of the aging program the epoxy resin underwent structural changes, seen as modifications of functional groups CH2, CH3 and C=O. The air atmosphere where partial discharges occurred also promoted the formation of reactive species. When the air volume was high enough, the findings of FTIR measurements suggested a local degradation mechanism of mica involving cation exchange reactions between partial discharge byproducts and potassium layers in the mica.

  • 7.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic application of the Inductive Power Transfer (IPT) systems in an electrified road: Dielectric power loss due to pavement materials2017In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 147, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Inductive Power Transfer (IPT) technology is seen as a promising solution to be applied in an electrified road (eRoad) to charge Electric Vehicles (EVs) dynamically, i.e. while they are in motion. Focus in this study was placed on the dielectric loss effect of pavement surfacing materials on the inductive power transfer efficiency, induced after the integration of the technology into the physical road structure. A combined experimental and model prediction analysis was carried out to calculate this dielectric loss magnitude, based on which some preliminary conclusions as well as a prioritization of future focus needs were summarized in detail.

  • 8.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic application of the Inductive Power Transfer (IPT) systems in an electrified road: Dielectric power loss due to pavement materials2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526Article in journal (Other academic)
    Abstract [en]

    It is well-known that the high cost and limited performance of existing energy storage systems have significantly constrained the commercialization of the Electric Vehicle (EV) at large scale. In recent years, attention has been given not only to the improved energy storage systems but also to develop appropriate charging infrastructures that would allow the EVs to be powered in an easier way. Inductive Power Transfer (IPT) technology, also known as a near-field wireless power transfer technology, is capable of delivering electricity wirelessly with large power and high efficiency at a given gap distance. It is therefore seen as a promising solution to be applied in an electrified road (eRoad) to charge EVs dynamically, i.e. while they are moving. Various technical aspects of this contactless charging solution have been studied actively by system developers, such as the charging power, its efficiency, the optimum gap distance as well safety issues. Focus in this study is placed on the effect of pavement surfacing materials on the wireless power transfer efficiency, after the integration of the technology into the physical road structures. Specifically, a combined experimental and model prediction analysis has been carried out to investigate this potential energy loss in a quantitative way, based on which some preliminary conclusions as well as a prioritization of future focus needs are summarized in detail. This work provides thus an important beginning for understanding the pavement materials’ influence on the IPT systems that may be used for dynamic applications in an eRoad.

  • 9.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Electrification of Roads: Opportunities and Challenges2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 150, p. 109-119Article in journal (Refereed)
    Abstract [en]

    The Electrical Vehicle (EV) has become a potential solution for enhancing the sustainability of our road transportation, in view of the environmental impacts traditional vehicles have regarding emissions and use of fossil fuel dependence. However, the widespread use of EVs is still restrained by the energy storage technologies, and the electrification of road transportation is still in its early stages. This paper focuses on the technical aspects related to the ‘electrification of roads’ (called ‘eRoads’) infrastructure that aims to diminish the limitations for using EVs. A historical overview of the technology development towards the electrification of road transportation is presented, along with an overview of prospective technologies for implementing an eRoad charging infrastructure. Of these, the Inductive Power Transfer (IPT) technology is examined in further details. The main objective of this paper is to explore the potential knowledge gaps that need to be filled for a successful integration of IPT technology within actual road infrastructure. As such, this paper can be used as an overview of the current state-of-the-art of eRoad infrastructure and also as guidance towards future research directions in this domain.  

  • 10.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    A study on dielectric response of bitumen in the low-frequency range2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 16, p. 153-169Article in journal (Refereed)
    Abstract [en]

    From the current state of literature, the dielectric property of bitumen has not been understood extensively, nor its relation with other properties such as polarity and rheology. In this study, dielectric spectroscopy measurement in a low-frequency range (10−2–106 Hz) was performed on both pure bitumen in different grades and wax-modified bitumen (WMB). From the performed tests we found the following: (i) the dielectric response of base bitumen is strongly temperature and frequency dependent, which is also highly linked to the rheology of the system. (ii) No remarkable differences in the dielectric constant (Formula presented.) among different grades of bitumen from the same crude oil source can be seen. (iii) Regular changes of dielectric loss tangent (tan δ) among the different grades of bitumen can be observed, which can be a good indicator for the linkage between the dielectric and rheological responses. In addition, it can also be perceived that the dielectric spectroscopy may have the potential to become a new approach for the multi-scale characterisation of road infrastructure materials.

  • 11.
    Cheng, Jialu
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of Advanced Bushing Diagnostic Techniques on Operation Reliability and Maintenance Strategy2022In: Proceedings 2022 IEEE International Conference on High Voltage Engineering and Applications, ICHVE 2022, Institute of Electrical and Electronics Engineers (IEEE) , 2022Conference paper (Refereed)
    Abstract [en]

    The reliability of power transformers is crucial for the safety operation of the power system. Detection of incipient faults, as well as natural aging, is the key to reduce the failure risk, which gives the operators adequate margin to perform maintenance before reaching a critical failure. Routine maintenance consists of a few testing techniques to check whether mechanical and electrical components fulfill the minimum threshold requirement. In addition, there are various advanced diagnostic testings that are capable of giving more precise condition indications of a transformer in thermal, electrical, and mechanical aspects. The reliability of transformers can thus be enhanced with the help of advanced diagnostic testings. However, in practice, it is often costly to perform the advanced testings and the effectiveness is hard to verify due to the lack of relevant cases and case studies. According to the published statistics, the failure rate is only around 0.1% - 0.2% per year. In this project, a widely accepted insulation condition diagnostic method, Dielectric Frequency Response, DFR was investigated in aspects of cost and return. Testing objects were a group of transformer bushings in three HVDC substations. Reliability is enhanced by identifying incipient bushing defects that cannot be detected by other routine testing techniques. By analyzing the cost and return of the DFR testing, the transition of the current maintenance strategy towards reliability-centered is in position.

  • 12.
    Cheng, Jialu
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Werelius, Peter
    Megger Sweden AB, Engn Dept, S-18236 Danderyd, Sweden..
    Nonlinear Dielectric Properties of the Stator and Transformer Insulation Systems2022In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 29, no 1, p. 240-246Article in journal (Refereed)
    Abstract [en]

    Composite insulation systems usually exhibit nonlinear phenomena, such as voltage-dependent dielectric response and high-order current harmonics. In this article, a high-voltage system capable of performing both dielectric frequency response (DFR) and polarization/depolarization current (PDC) measurements up to 20 kV is devised. The nonlinear properties of the motor stator and power transformer insulation systems are studied. Experimental results show that the voltage-dependent effect becomes significant as the voltage magnitude approaches the nominal and frequency decreases. The third current harmonic component is found to be dominant over the other components and has a strong correlation with the decrease in the dissipation factor. By taking both the fundamental and third-harmonic components into account, more consistent voltage-dependent characteristics are revealed. These features are important indications of insulation defects that are often neglected in field diagnostic testings. The investigation of the nonlinear properties helps to enhance the condition diagnosis reliability.

  • 13.
    Cheng, Jialu
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Werelius, Peter
    Abideen, Amar
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Hao, Jing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Influence of Nonlinear Stress Grading Material on Dielectric Frequency Response of Stator Insulation2020In: 7th IEEE International Conference on High Voltage Engineering and Application, ICHVE 2020 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2020Conference paper (Refereed)
    Abstract [en]

    Aging of high voltage generators and motors lead to changes in the dielectric properties of the stator winding insulation system. Research on the relation between aging and dielectric response has been going on for decades. A particular challenge is that the coil insulation consists of several materials: two that strongly affect the dielectric response are the ground-wall insulation and the stress grading shield (end-corona protection, ECP), which exhibit quite different properties. The influence of the ECP on the overall dielectric response of the insulation system might dwarf the condition change of the ground-wall insulation. In this paper, we introduce a test system that can measure the dielectric response in both time and frequency domain from low to rated voltage. Measurement results of two types of custom-designed, commercial standard stator winding coils are presented, and the influence of the ECP can be observed. The validity of time-frequency domain transformation of this nonlinear system is discussed. This paper acts as a basis for the application of dielectric diagnostic testing in the field.

  • 14.
    Cheng, Jialu
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Werelius, Peter
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Temperature Influence on Dielectric Response of Rotating Machine Insulation and Its Correction2019In: Proceedings of the 26th Nordic Insulation Symposium, 2019, p. 145-149Conference paper (Refereed)
    Abstract [en]

    Insulation condition is an essential aspect for the operational reliability of high voltage rotating machines in power plants and industrial applications. Insulation resistance (IR) and line-frequency dissipation-factor / power-factor (tanδ) measurement are often performed for the assessment of stator insulation condition. These measured values need to be normalized to a reference temperature (e.g. 40 °C) for comparison and trending and this is traditionally achieved by multiplying the results with a certain factor. However, this correction could be subject to error for an individual devicesince the correction factors recommended by various standards are average values of a certain number of machines at different conditions. In addition to that, insulation condition also has some influence on the temperature dependent property. With the introduction of Dielectric Frequency Response, DFR and Polarization/Depolarization Current, PDC as more advanced insulation diagnostic methods, with proper modelling, temperature correction can be done based on the insulation condition of an individual device and thus accuracy is considerably improved. In this paper, the background of DFR and its superiority in temperature correction are introduced. After that, the numerical Fourier and Inverse Fourier Transformation algorithm is applied to correct the time domain measurement (IR and PDC).

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  • 15.
    Cheng, Jialu
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Yizhou, Zhang
    China Nuclear Power Operation Technology Co., Ltd., Minzu Road 1021, Wuhan 430073, China.
    Yun, Hao
    China Nuclear Power Operation Technology Co., Ltd., Minzu Road 1021, Wuhan 430073, China.
    Wang, Liang
    China Nuclear Power Operation Technology Co., Ltd., Minzu Road 1021, Wuhan 430073, China.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    A Study of Frequency Domain Reflectometry Technique for High-Voltage Rotating Machine Winding Condition Assessment2023In: Machines, E-ISSN 2075-1702, Vol. 11, no 883Article in journal (Refereed)
    Abstract [en]

    Detecting and locating local degradations at an incipient stage is very important for mission-critical high-voltage rotating machines. One particular challenge in the existing testing techniques is that the characteristic of a local incipient defect is not prominent due to various factors such as averaging with the healthy remainder, attenuation in signal propagation, interference, and varied operating conditions. This paper proposes and investigates the frequency domain reflectometry (FDR) technique based on the scattering parameter measurement. The FDR result presents the object length, wave impedance, and reflections due to impedance discontinuity along the measured windings. Experiments were performed on two commercial coils with artificially created defects. These defects include turn-to-turn short, surface creepage, loose coils, insufficient end-winding spacing, and local overheating, which are commonly seen in practice. Two practical water pumps in the field were also selected for investigation. The study outcome shows that FDR can identify and locate structural and insulation degradation in both shielded and unshielded objects with good sensitivity. This makes FDR a complementary technique for machine fault diagnosis and aging assessment.

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  • 16.
    Ghaffarian Niasar, Mohamad
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kiiza, Respicius Clemence
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Effect of Partial Discharges on Thermal Breakdown of Oil Impregnated Paper2015In: IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, ISSN 1931-4973, E-ISSN 1931-4981, Vol. 10, p. S14-S18Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the effect of partial discharges (PDs) on the thermal breakdown voltage of oil-impregnated paper (OIP). A disk-shaped cavity in a stack of paper sheets formed the PD source. The paper sample was exposed to PDs for 18 h. Dielectric spectroscopy measurements were performed on the samples before and after exposure to PD activity. The dielectric spectroscopy results showed a big change in the real and imaginary part of the permittivity. These results were used to calculate the activation energy and heat losses inside the insulation. In order to investigate the possibility of thermal breakdown in the system, the OIP system was simulated by using the FEM software COMSOL Multiphysics. The heat produced by PD pulses and dielectric losses was considered in the simulation. The results show that for the OIP insulation, PD activity can reduce the thermal breakdown voltage by a factor up to 4 times.

  • 17.
    Ghaffarian Niasar, Mohamad
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kiiza, Respicius Clemence
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wang, Xiaolei
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Tenbohlen, Stefan
    Effect of Partial Discharges on Thermal Breakdown of Oil Impregnated Paper2014In: Conference Proceedings of ISEIM 2014, IEEE conference proceedings, 2014, p. -199Conference paper (Refereed)
    Abstract [en]

    In this paper the effect of partial discharges on the thermal breakdown voltage of oil-impregnated paper is investigated. A disc shaped cavity in a stack of paper sheets formed a PD source. The paper sample was exposed to partial discharges for 18 hours. Dielectric spectroscopy measurements were performed on the samples before and after exposure to PD activity. The dielectric spectroscopy results showed a big change in the real and imaginary part of the permittivity. These results were used to calculate activation energy and heat losses inside the insulation. In order to investigate the possibility of thermal breakdown in the system, the oil-impregnated paper system was simulated by using the FEM software Comsol Multiphysics. The heat produced by PD pulses and dielectric losses was considered in the simulation. The results show that for the oil-impregnated paper insulation, the PD activity can reduce the thermal breakdown voltage by a factor up to 4 times.

  • 18.
    Ghaffarian Niasar, Mohamad
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Janus, Patrick
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wang, Xiaolei
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kiiza, Respicius Clemence
    DIT Dar Es Salaam Institute of Technology, Tanzania .
    Partial Discharges in a Cavity Embedded in Oil-Impregnated Paper: Effect of Electrical and Thermal Aging2015In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 22, no 2, p. 1071-1079, article id 7076808Article in journal (Refereed)
    Abstract [en]

    In this paper, the rapid aging due to Partial Discharge (PD) activity was investigated in unaged and thermally aged oil-impregnated paper with a disk-shaped cavity between the sheets of paper. The PD inception voltage and the voltage for instantaneous breakdown were measured, and the time to breakdown was measured by applying voltages less than the instantaneous breakdown voltage. A comparison between time to breakdown of unaged and thermally aged paper shows no significant difference between thermally aged and unaged paper at sustaining PD activity. The time to breakdown as a function of applied electric field was plotted and compared for both cases showing points scattered around a line in log-log scale. Changes of the PD parameters, such as PD magnitude and PD repetition rate were analyzed from the beginning of PD activity up to the moment of breakdown. The results show that the number and magnitude of PD increase at the beginning of aging until they reach to a maximum value, then both quantities decrease slowly over time until the final puncture breakdown occurs. The results emphasize the importance of PD monitoring on real equipment with oil-impregnated paper as insulation system, such as power transformers, since a focus on the number and magnitude of PD at just the present time may mislead the interpretation. Dielectric spectroscopy measurements performed on unaged and thermally aged paper showed an increasing trend of epsilon '' after the sheets of paper were exposed to thermal aging for longer time. Dielectric spectroscopy measurements performed on samples before and after exposure to PD activity showed a big change of epsilon '', This change can be attributed to byproducts and ions produced by PD activity.

  • 19.
    Ghaffarian Niasar, Mohamad
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kiiza, Respicius Clemence
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dielectric Frequency Response of Oil-impregnated paper: the Effect of Partial Discharges Compared to other InfluencesManuscript (preprint) (Other academic)
  • 20.
    Gomes Guerreiro, Gabriel Miguel
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS). Hitachi ABB Power Grids, Natverksgatan 3, S-72136 Västerås, Sweden..
    Gajic, Z.
    Hitachi ABB Power Grids, Natverksgatan 3, S-72136 Västerås, Sweden..
    Zubic, S.
    Hitachi ABB Power Grids, Natverksgatan 3, S-72136 Västerås, Sweden..
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Habib, Md Zakaria
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Cross-Country faults in resonant-grounded networks: Mathematical modelling, simulations and field recordings2021In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 196, article id 107240Article in journal (Refereed)
    Abstract [en]

    Cross-Country Faults (CCFs) are defined by the occurrence of two Single Phase-to-Ground faults taking place simultaneously in different phases and at different locations of the galvanically connected network. Few studies about these faults in MV systems have been done so far, particularly with real fault data and simulations. In this work, first a mathematical model is derived to understand basic properties of CCFs. Then, simulations in RSCAD/RTDS (R) using real data obtained from an utility in Scandinavia are discussed and validated with two real faults measured in the field for resonant-grounded networks in Sweden and Norway. The mathematical calculations proved to have a good accuracy and showed important properties of CCFs such as the dependency of both faults of each others fault resistance and location. Furthermore, it was observed that such faults can be very different from more common types of faults in the power system. Interesting behaviors can appear particularly when feeders are connected in ring, where an extra current with smaller magnitude and 180 degrees appears on the measurement point, as well as in lines with double infeed where a very large difference is detected depending on the fault location which influences directly both ends of the line.

  • 21.
    Gomes Guerreiro, Gabriel Miguel
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS). Hitachi ABB Power Grids, Västerås, Sweden.
    Gajić, Zoran
    Hitachi ABB Power Grids, Västerås, Sweden.
    Zubić, Siniša
    Hitachi ABB Power Grids, Västerås, Sweden.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Habib, Md Zakaria
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    CROSS-COUNTRY FAULTS IN RESONANT-EARTHED NETWORKS: FAULT ANALYSIS AND DISTANCE PROTECTION2021In: :, p. 1226-1230Article in journal (Other academic)
    Abstract [en]

    Cross-Country faults (CCFs) are characterized by the situation when two phase-to-earth faults are simultaneously active on different phases at different locations in a network. Specially for resonant-earthed systems the current through the earth during a CCF becomes many times higher than during a single phase-to-earth fault. So far, few studies have been carried about these faults on resonant-earthed networks, specially evaluating the performance of distance protection. In this paper, simulations in RSCAD/RTDS® using real data obtained from a resonant-earthed network in Scandinavia are performed and different effects on distance protection are simulated. Four types of CCFs showing different patterns are defined and explained. Phase-to-phase loops of distance protection proved to be quite ineffective to protect against CCF faults since the fault outside the protected line/cable increases the impedance path. Phase-to-earth loops are accurate for low-resistance faults in a conductor with single infeed (Types I and II). However, when the line/cable is fed from both ends, some challenges can appear (Types III and IV). For Type III, the non-faulted Ph-E loop can be measured inside the protection zone due to the high residual current while for Type IV Ph-E loops will have problems to operate at all due to the lack of residual current.

  • 22.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Swedish Energy Agency (SWEGRIDS).
    Duvnjak Zarkovic, Sanja
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Distributed fault-passage indicators versus central fault location: comparison for reliability centered planning of resonant-earthed distribution systemsManuscript (preprint) (Other academic)
    Abstract [en]

    Fault location methods are crucial for reducing fault restoration time, and thus improving a network's system average interruption duration index (SAIDI) and customer outage cost. Resonant-earthed systems pose problems for traditional fault location methods, leading to poor accuracy and a need for additional complexity. In this context, methods that detect fault direction (fault-passage indicators, FPI) at multiple points in the network may show advantages over a central distance-estimation method using fault locators (FL) of poor accuracy. This paper includes a comparative study of these two major fault location methods, comparing the reliability benefit from a varied number of FPIs or a central method. The optimal placement of the fault locating devices is found by formulating a mixed-integer linear programming (MILP) optimization approach that minimizes both outage and investment costs and assesses SAIDI. This approach has been tested on an example distribution system. However, to justify the universality of the algorithm, the RBTS reliability test system has also been analysed. The comparison of location methods and placement method of FPIs are useful for reliability centred planning of resonant-earthed distribution systems where fault location is to be used. Results show that a small number of FPIs that give accurate identification of direction may give more cost effective increase in reliability than a distance estimate by FL with typical levels of inaccuracy.

  • 23.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Duvnjak Zarkovic, Sanja
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Shayesteh, Ebrahim
    Swedish Natl Grid Svenska Kraftnät, Sundbyberg, Sweden..
    Distributed fault-passage indicators versus central fault location: Comparison for reliability centred planning of resonant-earthed distribution systems2023In: Energy Reports, E-ISSN 2352-4847, Vol. 9, p. 1731-1742Article in journal (Refereed)
    Abstract [en]

    Fault location methods are crucial for reducing fault restoration time, and thus improving a network's system average interruption duration index (SAIDI) and customer outage cost. Resonant-earthed systems pose problems for traditional fault location methods, leading to poor accuracy and a need for additional complexity. In this context, methods that detect fault direction (fault-passage indicators, FPI) at multiple points in the network may show advantages over a central distance-estimation method using fault locators (FL) of poor accuracy. This paper includes a comparative study of these two major fault location methods, comparing the reliability benefit from a varied number of FPIs or a central method. The optimal placement of the fault locating devices is found by formulating a mixed-integer linear programming (MILP) optimization approach that minimizes both outage and investment costs and assesses SAIDI. This approach has been tested on an example distribution system. However, to justify the universality of the algorithm, the RBTS reliability test system has also been analysed. The comparison of location methods and placement method of FPIs are useful for reliability centred planning of resonant-earthed distribution systems where fault location is to be used. Results show that a small number of FPIs that give accurate identification of direction may give more cost effective increase in reliability than a distance estimate by FL with typical levels of inaccuracy.

  • 24.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Duvnjak Zarkovic, Sanja
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. KTH Royal Institute of Technology.
    Taylor, Nathaniel
    KTH, Superseded Departments (pre-2005), Electrical Systems. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. KTH Royal Institute of Technology.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. KTH Royal Institute of Technology.
    Reliability Centered Planning of a Resonant-earthed Distribution System with Focus on the Fault Location MethodsManuscript (preprint) (Other academic)
    Abstract [en]

    Fault location methods help to reduce the restoration time and thus improve the SAIDI (System average interruption duration index) of the network. Besides that, restoration time has a direct impact on customer outage cost. Traditional fault location methods struggle to perform adequately and need additional features for a resonant-earthed system. This paper assists in the reliability centred planning of such a system with the focus on fault location methods. Two major fault location methods are modelled for the study. The optimal placement of the fault locating devices is found by formulating a MILP optimization approach that minimizes both outage and investment cost and asses SAIDI. Moreover, a comparative study among the fault location methods is done to find the best case for an actual resonant-earthed distribution system.

  • 25.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    F. Abdel-Fattah, Mohamed
    Reykjavik University, Iceland.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    A Current-based Solution for Earth-fault Location in Resonant-earthed Medium-voltage Distribution Systems2020In: IET Conference Publications, Liverpool, United Kingdom, 2020Conference paper (Refereed)
    Abstract [en]

    This paper proposes a novel approach to locate earth-faults in resonant-earthed distribution systems. It uses the fundamental-frequency current measurements to determine the direction of the fault current and thereby to locate the faulted section. It sets the current-angle of the faulty phase as the reference for measuring the angles of the remaining two phase-currents. These three phasor quantities are then processed to determine the direction of the fault from the measurement point. The proposed method requires an adequate resistive current from the neutral for successfully determining the faulted section. The validity of the method has been tested by PSCAD simulations for a small-scale overhead distribution system.

  • 26.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Hoq, Md Tanbhir
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Duvnjak Zarkovic, Sanja
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of the fault location methods on SAIDI of a resonant-earthed distribution system2020In: 2020 IEEE International Conference on Power Systems Technology, POWERCON 2020, Institute of Electrical and Electronics Engineers Inc. , 2020Conference paper (Refereed)
    Abstract [en]

    Reliability indices of a distribution system can be improved by reducing failure rate and restoration time. A resonant-earthed distribution system has a low failure rate because numerous transient faults become self-extinguishing. However, in such networks, it can be difficult and time-consuming to locate nontransient faults resulting in aggravating the restoration time. This paper analyzes how different fault location methods affect the restoration time and SAIDI. Two major fault location methods are modeled for the calculation of the reliability indices and then applied to a radial feeder of a medium-voltage distribution system. The results show that SAIDI varies depending on the applied fault location method and its accuracy. The influence of fault location methods on labour costs is also discussed.

  • 27.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Swedish Energy Agency (SWEGRIDS).
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Incremental Phase-Current Based Fault Passage Indication for Earth Faults in Resonant Earthed NetworksManuscript (preprint) (Other academic)
    Abstract [en]

    We propose a current-based method for fault passage indication of earth faults in resonant-earthed networks. This type of network is commonly found in electricity distribution systems at medium-voltage levels. The proposed method is based on the magnitude of the changes in the phase currents due to the fault, and can therefore be implemented using just current sensors. It is implemented in MATLAB and tested on data from simulations in PSCAD for various network types and operation configurations. In over-compensated networks the method shows reliable detection of the fault passage, with good selectivity and sensitivity for both homogeneous and mixed (cable and overhead line) feeders. However, for under-compensated systems it has limitations that are described further in this study. The method has good potential for being cost-effective since it requires only current measurements, from a single location, at a moderate sampling rate.

  • 28.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Incremental Phase-Current Based Fault Passage Indication for Earth Faults in Resonant Earthed Networks2023In: Electricity, E-ISSN 2673-4826, Vol. 4, no 2, p. 96-113Article in journal (Refereed)
    Abstract [en]

    We propose a method for the fault passage indication of earth faults in resonant-earthed networks, based on phase current measurements alone. This is particularly relevant for electricity distribution systems at medium-voltage levels. The method is based on the relative magnitudes of the phasor changes in the phase currents due to the fault. It is tested for various network types and operation configurations by simulating the network in pscad and using the simulated currents as the input for an implementation of the method in matlab. In over-compensated networks, the method shows reliable detection of the fault passage, with good selectivity and sensitivity for both homogeneous and mixed (cable and overhead line) feeders. However, for the less common under-compensated systems, it has limitations that are described further in this study. The method has good potential for being cost effective since it requires only current measurements, from a single location, at a moderate sampling rate.

  • 29.
    Habib, Md Zakaria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    Li, YouYi
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Phase Shift Compensation Method for the Line Differential Protection on UHV-AC Transmission Lines2018Conference paper (Refereed)
    Abstract [en]

    Line differential protection is popular for its good selectivity and simplicity as long as there is a dependable communication system between the two ends of the line. However, the sensitivity needs to be compromised when traditional line differential scheme is applied for UHV-AC lines because of the large charging current. This paper presents a study of the impact of UHV transmission line characteristics on line differential protection and a proposed solution based on compensation of the phase shift that exists between the sending and receiving end currents.

  • 30.
    Hao, Jing
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Xie, Yiming
    Wuhan Univ, Sch Elect Engn & Automat, Wuhan 430072, Peoples R China..
    Frequency-Domain Spectroscopy of Oil and Oil-Impregnated Pressboard With DC Bias2022In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 29, no 2, p. 370-377Article in journal (Refereed)
    Abstract [en]

    Dielectric response measurement is widely used to characterize oil/oil-impregnated pressboards in order to evaluate the condition of transformer insulation. Insulation systems with oil can exhibit voltage dependence at low frequencies. This is due to the limited number of mobile charges in the liquid, rather than to the dielectric relaxation processes that may, in some cases, be of more interest to study. This work investigates the voltage-dependent properties of oil/oil-impregnated pressboards under ac voltages with regard to the complex permittivities. Frequency-domain spectroscopy (FDS) measurements are made with a dc voltage added to the ac voltage stimulus. Considered influences are the voltage amplitudes and polarity as well as the dependence on temperature. Properties of the space-charge polarization in the oil and oil-impregnated pressboard are calculated and discussed based on the dc-biased measurements. It is seen that using the dc bias in the FDS measurements of oil/oil-impregnated pressboard can significantly decrease the voltage dependence of the results that are caused by ion drift and consequent depletion of ions from the bulk liquid. Based on the dc-biased measurements, the complex permittivity due to the linear and nonlinear polarization can be separated.

  • 31.
    Hao, Jing
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Xiangdong, Xu
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    An Electrode Setup for Non-contact Dielectric Response Measurement2019In: Proceedings of the 26th Nordic Insulation Symposium, Tampere, June 2019, Norwegian University of Science and Technology (NTNU) Library , 2019Conference paper (Refereed)
    Abstract [en]

    The dielectric response measurement is a widely used technique for characterizing dielectric materials. However, the contact problems between samples and electrodes existing in the use of conventional electrode setup limit the accuracy of the measurement. In this paper, a type of electrode arrangement is introduced for avoiding direct contacts of the sample with both the bottom and the top electrode. The edge effect of this arrangement is calculated by the FEM model. The equations to derive the complex permittivity is presented. The measurement instrument is described and the influence of the potential difference between two terminals of the IDAX input is analyzed. Furthermore, the error sensitivities are compared between the non-contact and contact methods. The results show that this electrode arrangement can be used to perform non-contact measurements, and the edge effect of it is not significant. The potential between the two terminals of the IDAX is not an obstacle to obtain results with high accuracy. Overall, the non-contact electrode arrangement combined with the IDAX 300 can potentially improve the accuracy of dielectric response measurements although the non-contact methods can increase the sensitivities to errors.

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  • 32.
    Hao, Jing
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Xiangdong, Xu
    Chalmers Univ Technol, Elect Power Engn, S-41296 Gothenburg, Sweden.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Non-contact method to reduce contact problems between sample and electrode in dielectric measurements2020In: High Voltage, ISSN 2397-7264, Vol. 5, no 6, p. 753-761Article in journal (Refereed)
    Abstract [en]

    Dielectric response measurement is a widely used technique for characterising dielectric materials in terms of theircapacitance and dielectric loss. However, the widely used approach with contact between samples and electrodes can in somecases limit the accuracy of the measurement. The authors introduce an easily realised electrode arrangement for non-contactmeasurements, which avoids these contact problems. The performance of the electrode arrangement in terms of the edge effectis assessed. The non-contact and contact methods are compared based on error-sensitivity analysis and experimental results.Differences are studied further, with attention to contact pressure. The non-contact method is also compared experimentally withthe one-sided non-contact method. Air-reference measurements, comparing the sample to an air-gap for improved calibration,are used for all measurements. The results show that the non-contact method can be an alternative to reduce contact problemsbetween the sample and electrodes, although error sensitivity can be higher when the non-contact method is used. The non-contact method can decrease the influence of the pressure applied to the sample compared to the contact method, and can alsoreduce the problem of poor contact that can arise from the absence of pressure in the one-sided non-contact method

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  • 33.
    Hao, Jing
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Xu, X.
    Cheng, Jialu
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Non-contact Method for Dielectric Response Measurements2020In: 7th IEEE International Conference on High Voltage Engineering and Application, ICHVE 2020 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2020Conference paper (Refereed)
    Abstract [en]

    The dielectric response measurement is an important technique to assess the properties of insulation materials. However, the widely used approach with contact between samples and electrodes can in some cases limit the accuracy of the measurement. In this paper, an easily fabricated design is introduced and used to perform non-contact measurements. Air-reference measurements, comparing the sample to an air-gap for improved calibration, are used for all measurements. Results obtained by contact and non-contact methods, and with the feedback of electrometer locked and unlocked are compared. The effect of the pressure applied by the electrode is also investigated for both non-contact and contact measurements. Results show that the non-contact method can be an alternative to reduce contact problems between the sample and electrodes. For air-reference measurements, the impedance measurement instrument should be forced to use the same reference component for the air and sample measurements. Results obtained by the non-contact measurements are less sensitive to the pressure compared to that by contact measurements. 

  • 34.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Habib, Md Zakaria
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Reliability Assessment of Protection Schemes for Series Compensated Transmission Lines2019In: 4th International Conference on System Reliability and Safety (ICSRS), Rome, Italy, Institute of Electrical and Electronics Engineers (IEEE) , 2019Conference paper (Refereed)
    Abstract [en]

    Series capacitors are used in transmission lines for enhancing power transmission limit. However, they complicate the line’s protection due to impedance change of the line, voltage inversion, current inversion and sub-synchronous oscillation. Distance and differential protections are used in different arrangements in transmission line protection. Often they are used together as main and backup protection. In this paper, the fault tree method is used to compare the reliability of three common transmission line protection schemes. The schemes considered here are distance (main)-distance (backup)(Z; Z), differential (main)-distance (backup) (delta;Z) and differential (main)-differential (backup) (delta;delta). Fault trees are used to calculate the reliability of protection schemes in terms of both unavailability and failure rate. The analyses show that, for series compensated lines, using distance protection reduces protection system reliability. Differential protection performs best in terms of reliability despite depending entirely on communication.

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    Reliability Assessment of Protection Schemes for Series Compensated Transmission Lines
  • 35.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Distance Protection of Series Capacitor Compensated Lines: Practical Considerations, Industrial Status and Development2021In: Electricity, E-ISSN 2673-4826, Vol. 2, no 2, p. 168-186Article in journal (Refereed)
    Abstract [en]

    The introduction of series capacitors in transmission lines causes problems in terms of reliability and the security of distance protection relays. As distance protection is widely used in the transmission network, the challenge of applying it to series compensated lines has been taken up by utilities and relay manufacturers in various ways. In the field of power system protection, developments are largely driven by relay manufacturers, and are often not published in the academic literature; the status and trend of the relay manufacturer’s development are better found in their product manuals and patent activity. Further insight into specific implementations by transmission utilities can be found from publications in industry-led forums and some academic journals. This article surveys the status and development of distance protection for series compensated lines, with a focus on industrial implementation and practical considerations. Factors that influence the protection of series compensated lines are presented. Implementation examples reported by utilities are summarized as examples of the different situations encountered and the methods used to deal with them. It is observed that many utilities use communication-aided protection in series compensated lines, and distance protection is used with reduced reach. Solutions described in relay manuals are presented to demonstrate the manufacturers’ approaches to problems associated with series capacitor protection. While there are methods to counter voltage inversion, current inversion seems to represent a more serious challenge. A patent overview indicates the trends in this domain to be moving towards time-domain-based faster protection methods.

  • 36.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    An Incremental Quantity Based Distance Protection with Capacitor Voltage Estimation for Series Compensated Transmission Lines2021In: IEEE Access, E-ISSN 2169-3536, Vol. 9, p. 164493-164502Article in journal (Refereed)
    Abstract [en]

    Series capacitors increase the power transfer limit of transmission lines. However, the protection of series compensated lines using only local measurement is challenging. Phasor based distance protection experiences delay and directional problems in the presence of a series capacitor. This paper presents an incremental quantity based distance protection algorithm for series compensated lines. The algorithm uses instantaneous voltage and current measurement from the local bus. It consists of capacitor voltage estimation, fault detection, phase selection, directional discrimination and distance estimation. The algorithm is extensively tested based on simulations with a line-end series capacitor, considering different source impedance ratios, fault inception angle, compensation levels, and fault resistance, location and type. This time-domain method is shown to work well, with fast decision time.

  • 37.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    Hitachi Energy Research, Hitachi Energy, Västerås, Sweden.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    An Incremental Quantity Based Protection with Capacitor Voltage Estimation for Mid-Line Series Compensation2022Conference paper (Refereed)
    Abstract [en]

    Series capacitors are installed in transmission lines to increase power transfer capacity. However, their addition creates challenges for the line protection. Security and speed of phasor based protection schemes that work with local measurements (communication independent) are severely affected in the presence of series capacitors. Therefore, time-domain based protection methods may be considered as a potential solution for communication independent protection of series compensated lines. In this paper, an incremental quantity based protection scheme is presented for series compensated lines with the capacitor in the middle of the line. The method involves estimating the voltage across the capacitor bank, based on the current in the capacitor bank and metal oxide varistor during faults. Then this capacitor voltage estimation is used to implement the incremental quantity protection. The incremental quantity method consists of fault detection, phase selection, directional discrimination and distance estimation. A PSCAD model of a 500 kV, 200 km transmission line is used to simulate fault cases for evaluating the method. The proposed method is tested with different compensation levels, fault types, fault positions, inception angles, fault resistances and source impedance ratios. The results show that the proposed method can meet the dependability and security demands for the protection of series compensated lines.

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  • 38.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Wang, Jianping
    Hitachi Energy Research, Hitachi Energy, Västerås, Sweden.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    An Incremental Quantity Based Protection With Capacitor Voltage Estimation For Mid-Line Series Compensation2022Conference paper (Other academic)
    Abstract [en]

    Series capacitors are installed in transmission lines to increase power transfer capacity. However, their addition creates challenges for the line protection. Security and speed of phasor based protection schemes that work with local measurements (communication independent) are severely affected in the presence of series capacitors. Therefore, time-domain based protection methods may be considered as a potential solution for communication independent protection of series compensated lines. In this paper, an incremental quantity based protection scheme is presented for series compensated lines with the capacitor in the middle of the line. The method involves estimating the voltage across the capacitor bank, based on the current in the capacitor bank and metal oxide varistor during faults. Then this capacitor voltage estimation is used to implement the incremental quantity protection. The incremental quantity method consists of fault detection, phase selection, directional discrimination and distance estimation. A PSCAD model of a 500 kV, 200 km transmission line is used to simulate fault cases for evaluating the method. The proposed method is tested with different compensation levels, fault types, fault positions, inception angles, fault resistances and source impedance ratios. The results show that the proposed method can meet the dependability and security demands for the protection of series compensated lines.

  • 39.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Assessing Distance Protection Methods for Series Compensated Transmission LinesManuscript (preprint) (Other academic)
    Abstract [en]

    Series capacitors create challenges for traditional phasor-based distance relays in power transmission lines. Phasor based distance relays experience directional problems and delays.This paper compares the performance of phasor-based distance protection in series compensated line protection with three other distance protection methods. The first method is based on incremental quantities in the time domain, the second is based on Lissajous curves and conic section general equation, and the third is based on the RL and RLC model of the transmission line.The performance of these methods is evaluated in different fault conditions that create problems for phasor-based distance protection.Their relative advantages and disadvantages are outlined and discussed to identify their suitability for series compensated line protection. It is observed that the incremental quantity and model-based protections give fast and secure protection in series compensated lines. The conic section general equation based method can help avoid inversion, but the operating speed is slower than the other methods.

  • 40.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Distance Protection of Series Compensated Transmission Line using Lissajous Curves and Conic Section General EquationManuscript (preprint) (Other academic)
    Abstract [en]

    We demonstrate a time-domain estimation of impedance, based on the conic-section general equation and Lissajous curves, applied to protection of transmission lines that have series-capacitor compensation. This method helps to avoid the problems experienced by phasor-based distance relays when series compensation leads to voltage inversion or current inversion. Validation is performed using data from simulations of series compensated lines with a wide range of parameters such as sampling frequency, source impedance ratio, compensation level, fault inception angle,fault resistance, and fault location. It is seen that this method works well for series compensated lines, with operating times in the range of one and a half cycles.

  • 41.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Impact of High Levels of Series Compensation on Line Distance Protection2020In: IET Conference Publications, 2020Conference paper (Refereed)
    Abstract [en]

    Series compensation of transmission lines creates several challenges for distance protection, particularly at the high compensation levels that have recently become more common. In this paper, the effect of high levels of series compensation on distance protection is evaluated, using a PSCAD simulation model of a 500 kV, 200 km transmission line with a series capacitor bank. The capacitor bank model includes overvoltage protection using a metal oxide varistor (MOV) and bypass circuit breaker. Compensation levels of 70%, 100% and 140% are simulated and phase to ground faults are simulated at several positions along the line, with fault resistance of 0 Ω and 30 Ω and fault inception angle of 0 ° and 90 °. It is observed from the simulation results that traditional distance protection experiences severe challenges at high levels of series compensation. With increasing compensation level, an increased length of line experiences voltage inversion and current inversion during a fault. The fault trajectories in the R-X plane show that voltage and current inversion during a fault can cause directional problems and delay for the distance relay. Sub-synchronous oscillation (SSO) is observed for faults in series compensated lines, causing over-reach and under-reach problems as well as delayed relay operation.

    Download full text (pdf)
    Impact of High Levels of Series Compensation on Line Distance Protection
  • 42.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    ABB Power Grids Sweden AB, Power Grids Research, Västerås 722 26, Sweden.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Review of recent developments in distance protection of series capacitor compensated lines2021In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 190, article id 106831Article in journal (Refereed)
    Abstract [en]

    Introduction of series capacitors in transmission lines can cause problems with reliability and security of distance protection, due to problems such as current inversion, voltage inversion and sub-synchronous oscillation. Distance protection is widely used for transmission lines and has desirable features not available from traditional alternatives, which has motivated attempts to adapt it to work better with series capacitors. Research and development in overcoming the challenges using distance protection in series compensated lines have also been actively pursued during this period. Thus there is a need to summarize and systematically categorize developments, to show recent trends and highlight further research opportunities. This paper aims to fill that gap by a thorough literature survey of distance protection of series compensated lines, including a clear background of the problems that need to be solved. The scope of this work is limited to distance protection schemes that work with local measurements only. It is observed that the developments in this domain are largely concentrated on voltage drop estimation across capacitor bank, phasor estimation and adaptive protection schemes. This work will provide an overview of the latest developments for experienced researchers and will be a reference for new researchers interested in this domain.

  • 43.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    The Impact of Current Inversion on Line Protection in High Voltage Transmission Lines with Series Compensation2019Conference paper (Refereed)
    Abstract [en]

    Series capacitors are used in some transmission lines to raise the power transfer limit. If a fault occurs at a location behind which the total reactance is capacitive, the result is current inversion, also known as current reversal. In a current inversion, current leads the voltage instead of lagging it. The probability of current inversion increases with higher levels of compensation. In this paper, the effect of current inversion is studied in distance and differential protection of transmission lines. A 500 kV transmission line is modelled, with compensation levels of 70%, 100% and 140%. Phase to ground faults are applied with fault inception angles of 0, 60 and 90. It is shown that current inversion can cause serious problems with distance protection. Differential protection is not severely affected by current inversion. The protection schemes are significantly influenced by parameters of the capacitor bank overvoltage protection components, particularly the metal-oxide varistor.

    Download full text (pdf)
    The Impact of Current Inversion on Line Protection in High Voltage Transmission Lines with Series Compensation
  • 44.
    Hoq, Md Tanbhir
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Wang, Jianping
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Time Domain Distance Protection for Series Compensated Transmission Lines  Using RL and RLC Line ModelsManuscript (preprint) (Other academic)
    Abstract [en]

    Fast time-domain distance protection using RL and RLC models of a transmission line is presented in this paper for application to series compensated transmission lines. The proposed method is suited to both line-terminal andmid-line series compensation. It avoids classic limitations of delays and directional problems that phasor-based distance protection exhibits in series compensated transmission lines in the presence of voltage or current inversion sand subsynchronous oscillations. The method is validated with different system parameters such as compensation levels, source impedance ratio, fault inception angle, and fault resistance. The proposed method works well, with operating times in the range of a half cycle.

  • 45. Kande, M.
    et al.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Automation system generic security key manager2018In: Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 2867-2871Conference paper (Refereed)
    Abstract [en]

    The security research interest in industrial automation domain has gained importance due to the increased severity of cyber threats towards existing and future industrial systems. Secure communication between the devices is vital for creating a secure environment in the industrial plant. The keys used for secure communication must be protected against unauthorized disclosure, misuse, alteration or loss. In addition to that, industrial automation deployment has unique and strict demands on Quality Of Service (QOS). Conventional security architectures may not meet these requirements without substantial addition of cost and complexity. From a system level perspective, a flexible, easy to integrate and scalable key management architecture is essential for successful security deployment. This paper addresses interoperability and ease of integration using a centralized generic key management infrastructure designed for industrial automation systems. 

  • 46.
    Kande, Mallikarjun
    et al.
    KTH, School of Electrical Engineering (EES). ABB .
    Isaksson, Alf J.
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Rotating Electrical Machine Condition Monitoring Automation-A Review2017In: Machines, E-ISSN 2075-1702, Vol. 5, no 4, article id 24Article, review/survey (Refereed)
    Abstract [en]

    We review existing machine condition monitoring techniques and industrial automation for plant-wide condition monitoring of rotating electrical machines. Cost and complexity of a condition monitoring system increase with the number of measurements, so extensive condition monitoring is currently mainly restricted to the situations where the consequences of poor availability, yield or quality are so severe that they clearly justify the investment in monitoring. There are challenges to obtaining plant-wide monitoring that includes even small machines and non-critical applications. One of the major inhibiting factors is the ratio of condition monitoring cost to equipment cost, which is crucial to the acceptance of using monitoring to guide maintenance for a large fleet of electrical machinery. Ongoing developments in sensing, communication and computation for industrial automation may greatly extend the set of machines for which extensive monitoring is viable.

  • 47.
    Kane, Makarand
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Månsson, Daniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Characterization of Parasitic Impedances of PV Panels from Common Mode Perspective2022In: 2022 International Symposium on Electromagnetic Compatibility – EMC Europe, 2022, Institute of Electrical and Electronics Engineers (IEEE), 2022Conference paper (Refereed)
    Abstract [en]

    Parasitic impedances of PV panels play an important role in the common mode circuit. This work has investigated parasitic impedance model including capacitances and inductances, against the one with only capacitances considered in the literature. Further, the effects of geometrical and environmental factors on the parasitic capacitances are analysed using Finite Element Method (FEM) and Design of Experiments (DoE). The analysis has revealed that the water layer above panels is significant for cell-to-frame capacitance and not for cell-to-ground capacitance. Frequency domain analysis of total parasitic impedances is presented which shows that the total impedance exhibits resonances and inductive behaviour in the MHz range. These features are not captured if only capacitive model is considered.

  • 48.
    Kane, Makarand
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Månsson, Daniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Experimental Investigations into Common Mode Impedance of PV Panels2023In: Proceedings IET Renewable Power Generation and Future Power Systems Conference 2023, Glasgow, UK: Institution of Engineering and Technology (IET) , 2023Conference paper (Refereed)
    Abstract [en]

    The nature of common mode (CM) parasitic impedance (ZPV) of photovoltaic (PV) panels is investigated by experimentation. Measurements are done by two methods: (a) time domain signal recording using a signal generator and an oscilloscope (b) frequency sweep using an LCR meter. It is shown that ZPV is not purely capacitive for the frequency range from 50 Hz to 1 MHz.  It is also shown that the total common mode impedance in a PV installation is affected by the nature of ZPV.  The frequency spectrum of CM current would be different if ZPV is not purely capacitive. This would affect the design of CM filters on the DC and AC side and also equipment like PV emulators, DC line impedance stabilization network, etc.

    Download full text (pdf)
    ZPV_Kane
  • 49.
    Kane, Makarand
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Månsson, Daniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Investigations Into Conducted Emissions of A 10 kW Photovoltaic Plant2024In: IEEE Letters on Electromagnetic Compatibility Practice and Applications, E-ISSN 2637-6423, Vol. 6, no 1, p. 16-21Article in journal (Refereed)
    Abstract [en]

    Considering inverter as the source of electromagnetic emission signals in a photovoltaic (PV) plant, a comprehensive set of measurements of conducted emissions at the input and output of the inverter in a 10 kW PV plant are presented. These are particularly relevant on the backdrop of (a) ban of products in the EU market due to non-compliance and (b) the increased switching frequency in the inverters ( 100s of kHz) in near future. Specifically, the common mode (CM) and differential mode (DM) currents and voltages are measured, and their frequency domain behavior is studied. It is suggested that conducted emissions from PV can be classified into three zones: viz., extremely low frequency (ELF) zone, power frequency zone, and switching frequency zone. Important observations from this exercise are measurement of harmonic contents of current with total rated current distortion (TRD), imbalance in the output voltage and low frequency ripples in the DC voltage. Frequency domain behavior of the CM quantities is studied which throws light on important points like relation between input and output CM quantities, relation between CM voltage and CM current.

  • 50.
    Laurell Lyne, Åsa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jäverberg, Nadejda
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Low Frequency Dielectric Spectroscopy of Bitumen Binders.Manuscript (preprint) (Other academic)
12 1 - 50 of 97
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