Fast and Effective Technique in Evaluation of Lightning Impulse Voltage Parameters
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ORIGINAL ARTICLE
Fast and Effective Technique in Evaluation of Lightning Impulse Voltage Parameters Peerawut Yutthagowith1 · Krit Kitwattana1 · Anantawat Kunakorn1 Received: 1 March 2020 / Revised: 23 July 2020 / Accepted: 21 September 2020 © The Korean Institute of Electrical Engineers 2020
Abstract This paper presents an approach for the waveform parameter evaluation of lightning impulse voltage in high voltage tests according to the IEC standards. Such waveform parameters are composed of peak voltage (Up), front time (T1), time to half (T2), and the overshoot rate (Be). An artificial neural network with a back-propagation learning algorithm was applied to determine a base curve and its parameters from 14 points along the recorded waveform between 20% of the peak voltage on the wave front part to 40% of the peak voltage on the wave tail part. The 29 waveforms recommended by the standard were used in the training process of the development of the network model, and some experimental cases were also utilized for verification of the proposed method. It is found that the waveform parameters evaluated by the proposed approach are in the tolerances of the standard requirements. Maximum absolute deviations of Up, T1, T2, and Be are 0.06%, 2.00%, 0.12%, and 0.79%, respectively. Due to that no iteration process in the proposed approach is required, the efficiency in calculation process is significantly faster than the standard recommended approach. Keywords Artificial neural network · Curve fitting · Evaluation · Lightning impulse voltage · Waveform parameters
1 Introduction Lightning impulse voltage test is required in order to evaluate electrical power equipment insulation withstand under an overvoltage condition. The test is performed in a testing laboratory with a standard lightning impulse waveform. The international standards [1, 2] specify the standard lightning impulse waveform by waveform parameters with their tolerances, which are defined by the front time (T1) of 1.2 μs ± 30%, the time to half (T2) of 50 μs ± 20%, and the peak voltage depended on the voltage rating of the equipment under test.
* Peerawut Yutthagowith [email protected] Krit Kitwattana [email protected] Anantawat Kunakorn [email protected] 1
An impulse generator with a simple resistor–capacitor circuit can produce the lightning impulse voltage waveform. However, in the actual tests, the testing waveform might often be superimposed of an oscillation and an overshoot due to a parasitic inductance in the generation circuit. Such overshoot and oscillation on the generated voltage waveform have to be take into account in assessing the insulation withstand performance [3–5]. Therefore, the standards [1, 2] introduce the k-factor approach for evaluation of the peak voltage, which is equivalent to the peak voltage of the smooth lightning impulse voltage without oscillation and overshoot on the waveform. In the modern impulse voltage measuring systems, the voltage waveform is recorded by a digital oscilloscope, which has
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