| 1. |
- Espín-Delgado, Ángela, et al.
(author)
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Failure of MV Cable Terminations due to Supraharmonic Voltages : A Risk Indicator
- 2020
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In: IEEE Open Journal of Industry Applications. - : IEEE. - 2644-1241. ; 1, s. 42-51
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Journal article (peer-reviewed)abstract
- This paper addresses the accelerated aging of medium-voltage (MV) cable terminations with resistive stress-grading due to supraharmonics. The paper introduces a simple and quick way to relate the risk of cable termination failure to the characteristics of supraharmonic distortion in the system. The motivation is to give practical recommendations and guidelines to evaluate the risk of failure of cable terminations under the presence of supraharmonics in MV networks. The underlying model relates the heating in the cable termination linearly with the frequency of the voltage applied and proportionally with the square of the magnitude of the voltage. The indicator can be used to decide whether given levels and frequencies of supraharmonics in the MV network represent a risk to cable terminations. The parameters of the cable termination design are not needed for that decision. However, the decision criterion is based on one sample data (Eagle Pass) and more field information is crucial to improve the approach.
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| 2. |
- Felicetti, Roberto, 1972-, et al.
(author)
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An alternative Run-Up Strategy for Salient Pole Wound Field Synchronous Machines
- 2024
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In: IEEE Open Journal of Industrial Applications. - : Institute of Electrical and Electronics Engineers (IEEE). - 2644-1241. ; 5, s. 15-28
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Journal article (peer-reviewed)abstract
- Salient pole wound field synchronous motors find many industrial applications thanks to their favorable characteristics: reactive power regulation, stiff mechanical characteristic and overall outstanding efficiency. Nevertheless, their competitiveness towards the induction motors, especially for medium and small power sizes, depends crucially on their capability to be asynchronously started as well. Regrettably, the asynchronous run-up of a synchronous motor can be sometimes very problematic because of thermal issues, torsional vibrations and grid voltage disturbances. This paper presents an alternative method of starting salient pole wound field synchronous machines by activating the field winding in a special manner, which makes it possible to mitigate the three problems at once. The suggested method is validated through a 2D finite elements simulation and by starting a 60 kVA prototype generator. The requirements for the application of the proposed run-up strategy are critically discussed together with related pros and cons.
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| 3. |
- Sutaria, Jil, et al.
(author)
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Summation of Supraharmonics in Neutral for Three-Phase Four-Wire System
- 2020
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In: IEEE Open Journal of Industry Applications. - : IEEE. - 2644-1241. ; 1, s. 148-156
-
Journal article (peer-reviewed)abstract
- Due to the increase in electronic loads such as LED lamps, power supply units for computing loads, voltage frequency drives in industries; high-frequency distortion is introduced into the power system. These high-frequency components appear due to the switching components of different power electronic converters present in the mentioned loads. The switching frequency components are most often in the range of 2 kHz to 150 kHz referred to as supraharmonics. The paper aims to show, with simulations and measurements, how supraharmonics sum in neutral and to quantify the neutral supraharmonic current as a ratio of single-phase current. This paper defines characteristics of supraharmonic emission that influence their summation in the neutral conductor through studies of devices connected in a balanced three-phase four-wire system. The paper further defines the relation of the supraharmonics emission with the number of devices connected at each phase. A mathematical model to predict the supraharmonics in a neutral conductor based on single-phase current and the number of devices further proposed.
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