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![Fig 1. Lightning impulse voltage time parameters [1]](profile/Bozidar-Filipovic-Grcic/publication/268390314/figure/fig1/AS:392034948009994@1470479823863/Lightning-impulse-voltage-time-parameters-1_Q320.jpg)
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Context 1
... usually occurs when the connecting leads from impulse generator to test object are very long and the inductance is comparably high. In case of a test object with high capacitance, low values of the impulse generator front resistors are used which in some cases can lead to oscillations occurrence. Fig. 2 shows the overshoot β which represents the increase of amplitude of an impulse voltage due to a damped oscillation (frequency range usually 0.1 MHz to 2 MHz) at the peak caused by the inductance of the test circuit and the load capacitance. According to [1], the relative overshoot magnitude shall not exceed 10 ...
Citations
According to IEC 60060-1, 2010 and IEEE 4-2013 standards, the standard lightning impulse (LI) voltage waveforms are needed for testing the insulation of large equipment. The generation of these impulse waveforms sometimes difficult due to presence of internal inductance (Ls) in impulse generator (IG) circuit, the level of test object capacitance (C2), and the level of test object inductance (Lt). Thus, a new procedure is proposed for identifying the limit of wavefront resistance (R1) to generate required impulse waveforms (i.e., rise time (tr ≤ 1.56 µs) and overshoot rate (β'≤5%)) when the parameters Ls, C2, and Lt of fourth order IG circuit are systematically varies. Another attempt has also made in this paper to determine the limit values of the test object parameters such as load resistance Rt and load inductance Lt for matching the response of fourth order to third order IG circuit. Further, the analysis performed in this paper will be helpful in generating the test impulse voltage waveforms for testing ultra-high voltage (UHV) transformer.
The lightning impulse withstand voltage test is a test item that must be carried out for type testing, factory test or even field test of electrical equipment such as gas insulated metal-enclosed switchgear (GIS).However, the factors affecting the lightning impulse test waveform are complex and diverse. In this paper, the discharge principle of the impulse voltage generator is studied. Combined with simulation, the influence of different factors on the waveform parameters of lightning impulse test of UHV GIS equipment is obtained. The common methods and improvement measures of waveform debugging are pointed out, and the main factors affecting the parameters of lightning waves are studied.
An effective technique for determination of the circuit parameters in the air core inductor lightning impulse test is presented. The air core inductor is a specific test object affecting the test waveform of which the time to half is often shorter than the standard requirement. To increase the time to half, Glaninger's circuit was introduced by connecting the additional circuit parameters, i.e. the additional inductor and resistor. In order to select the additional circuit parameters and obtain the lightning impulse voltage waveform according to the standard requirement, it is necessary to precisely determine the other test circuit parameters, i.e. the front time resistance, the tail time resistance, parasitic series inductance, and load impedance composing of load resistance, load capacitance, and load inductance. In this paper, the matrix pencil method is employed to determine the circuit parameters by using the recorded waveform from the preliminary experiment. With the known circuit parameters, the additional circuit parameters can be searched to obtain the standard lightning impulse voltage waveform. The proposed method has been verified by some simulation and experimental cases successfully. The proposed technique is very useful in the lightning impulse voltage test of an air core inductor and helps test engineers in design appropriate circuit impedance without a trial and error approach.
