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    Dielectric performance analysis of laboratory aged power cable under harmonic voltages
    (Springer, 2022) Uydur, Cihat Cagdas; Arikan, Oktay
    In recent years, due to the increasing use of nonlinear loads, the level of harmonics deteriorating the power quality has also increased in the distribution system. The harmonics have a negative effect on the behavior of equipment and materials, as they distort voltage and current waveforms of the system it is connected to. This leads to heating problems due to additional losses for the distribution system components. Due to the multitude of technical, environmental and social causes, the use of power cables, especially cross-linked polyethylene (XLPE) power cables, is increasing rapidly. In this context the problem of power system harmonics and using of XLPE power cables in distribution systems are spreading simultaneously. In this study, 60 kV overvoltage (5 center dot U-0) aging process was performed on 12/20.8 kV XLPE power cable samples at Yildiz Technical University High Voltage Laboratory. The dielectric parameters (P-K, tan delta and C) of the aged cable samples were measured. By using OMICRON CPC100/CP-TD1 measuring device, the effects of harmonics with different measurement voltages have been examined on underground cables. The performance of aged cables is analyzed under harmonic voltages and the results are presented. The disruptive effects created by the 3rd-5th and 7th order harmonics have been revealed.
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    The Effect of Insulation Defects on Electric and Magnetic Field Distributions in Power Cables
    (Univ Osijek, Tech Fac, 2021) Uydur, Cihat Cagdas; Arikan, Oktay; Kalenderli, Ozcan
    In this article, electrical and magnetic field analysis in XLPE insulated power cables is performed. The defects that may occur in the insulation material have been tried to be realized considering different conditions. A lot of variations have been obtained by changing the location of the defect in the insulation material, the shape of the defect, the size of the defect and the type of the defect. The effect of all the factors that make up the defect on the distribution of the electric field and magnetic field is shown and the causes of malfunction in the cable are examined. The electric field analysis for 1 x 240/25 mm(2) was performed by using different forms with equal areas. The magnetic field analysis was performed for balanced and unbalanced load cases to 3 x (1 x 240/25) mm(2) and 3 x 240/25 mm(2) cable with XLPE insulation.
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    The Effect of Insulation Defects on Electric Field Distribution of Power Cables
    (IEEE, 2018) Uydur, Cihat Cagdas; Arikan, Oktay; Kalenderli, Ozcan
    Electricity transmission with high voltage is usually done with overhead lines by using bare conductors. Population growth in settlements makes it necessary to transmit and distribute electric energy from underground. Insulation is the most important factor in ensuring that electrical energy transmission and distribution with underground cables safely. The insulation problems that may occur in the production of underground cables cause rapidly aging and failures due to partial discharges. In this study, the effect of defects that may occur in the insulation of XLPE insulated cables to electric field distributions in the cable is investigated. In the XLPE insulated cables with 20.3/35 kV, 240 mm(2) and 400 mm(2) conductor cross-sections; electrical field distributions have been investigated by considering problems such as air bubble, water droplets and fiber-like solid particles. Cases of these defects on the surface of the conductor, in the insulator and on the surface of the insulator were considered. The Finite Element Method Magnetics (FEMM) program was used in the analyses.
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    The Effects of Overvoltage Aging on 20 kV XLPE Power Cable
    (IEEE, 2019) Uydur, Cihat Cagdas; Arikan, Oktay; Kucukaydin, Baris; Dursun, Bekir; Kumru, Celal Fadil
    XLPE power cables have been widely used with the development of city power grid because of their obvious advantages. To improve the reliability of power supplies and meet the requirements of urban landscaping, however, faults in the electricity distribution grid and load/demand imbalance cause degradation in underground cables. This degradation leads the cable to be aged and reduce its lifetime. Therefore, it is important to examine the behavior of the XLPE insulated cable dielectric parameters. In this study, a 12/20 kV XLPE cable was aged using 60 kV overvoltage and this voltage was applied to the test samples for 15 minutes intervals. 80 cycles of aging were carried out and dissipation factor (tan delta), dielectric losses (P-k) and partial discharge (PD) measurements were performed after each aging cycle. OMICRON CPC100/CPTD1 was used to measure dissipation factor (tans), dielectric losses (Pk) and OMICRON MPD600 was used to measure partial discharge.
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    Insulation evaluation of MV underground cable with partial discharge and dielectric dissipation factor measurements
    (Elsevier Science Sa, 2023) Arikan, Oktay; Uydur, Cihat Cagdas; Kumru, Celal Fadil
    As it is known overvoltage and impulse voltage are the most common stresses that cables are exposed to in practice. Since the occurrence frequency, duration and amplitude of these two stresses are different, their deteriorating effects on the cable insulation also differ. At this point, it is necessary to know how sensitively the preferred dielectric diagnosis method can detect the deteriorations on cable insulation. Since it is not technically possible to detect all isolation errors with a single preferred diagnostic method, the methods must be used together in a certain procedure. In this study, 12/20.8 kV, XLPE insulated Cable Samples were artificially aged using 50 aging cycles of overvoltage (36 kV and 60 kV) and 50 kV, standard positive impulse voltage. After each aging cycle, dielectric performance of cable insulation was measured using partial discharge (PD) and dielectric dissipation factor (DDF) methods. The accuracy of dielectric diagnosis methods due to overvoltage and impulse voltage are analyzed and discussed based on the measurement results. In order to analyze dielectric diagnostic performances of the methods, both individual trends and the correlation between PD and DDF parameters during overvoltage and impulse voltage aging processes were shared. As a result, it was found that diagnostic perfor-mances of PD and DDF methods differ according to the amplitude and waveform of the applied electrical stress. Therefore, a dielectric diagnosis procedure for MV cables including both PD and DDF methods to improve diagnostic process in field applications was proposed. In this context, the use of the proposed diagnosis procedure will contribute to the evaluation of the findings resulting from the diagnostic methods during the operation of MV cables.
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    Prediction of dielectric parameters of an aged mv cable: A comparison of curve fitting, decision tree and artificial neural network methods
    (Elsevier Science Sa, 2022) Arikan, Oktay; Uydur, Cihat Cagdas; Kumru, Celal Fadil
    In most dielectric diagnosis studies on medium voltage cables, aging methods, which requires quite long measurement durations, are preferred and dielectric performance of cable is generally measured at the end of the test period. In addition, changes that occur during the aging cycle should be investigated. Predicting the future performance of a cable by using dielectric parameters measured during the aging cycle is quite important in terms of estimating possible failures. In this regard, the effectiveness of interpolation and extrapolation methods commonly used in the literature should be investigated in order to shorten aging durations and to predict future insulation performance. In this study, 12/20.8 kV rated voltage and XLPE insulated medium voltage cable was aged with 60 kV (5 center dot U-0) overvoltage for 80 cycles of 15 min. After each aging cycle, dielectric parameters (dissipation factor (tan delta), dielectric losses (P-k) and capacitance (C) were measured at rated voltage and mains frequency. Following the measurements, interpolation and extrapolation analyses were performed using artificial neural network (ANN), decision tree (DT) and curve fitting (CF) methods. As a result, interpolation and extrapolation performances of methods are comparatively discussed and introduced. It has been determined that ANN algorithm is the most successful method.
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    Use of Tan? and Partial Discharge for Evaluating the Cable Termination Assembly
    (Mdpi, 2020) Uydur, Cihat Cagdas; Arikan, Oktay
    It is known that the failure of cable terminations causes power outages and impairs system quality and continuity. Besides, serious economic losses on both the distribution and consumer sides occur. In this study, the dielectric behavior of the cable and the faults caused by the defects in the cable termination under overvoltage has been examined. As test samples, 12 kV XLPE insulated cable is used and they were aged at three (3*U-0) and five (5*U-0) times the rated voltage. After each aging cycle, dielectric parameters of the cable were measured by an OMIRCRON CPC100/CPTD1 device, and the partial discharge (PD) was measured by an OMICRON MPD600 device. In the measurements, it was observed that the cable was broken down at different aging cycle numbers as a result of defects in the cable termination due to weak workmanship. As a result of the measurements, it is concluded that defects in the cable termination give information about the increase in the probability of failure and the decrease of the cable lifetime. Consequently, it is concluded that fine workmanship and timely maintenance of cable terminations prevent the system from unwanted power outages and economic losses.