Generation of Impulse Voltage Waveforms for Tesing of UHV Transformer: A Study

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 (L-s) in impulse generator (IG) circuit, the level of test object capacitance (C-2), and the level of test object inductance (L-t). Thus, a new procedure is proposed for identifying the limit of wavefront resistance (R-1) to generate required impulse waveforms (i.e., rise time (t(r) <= 1.56 mu s) and overshoot rate (beta' <= 5%)) when the parameters L-s, C-2, and L-t 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 R-t and load inductance L-t 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 ultrahigh voltage (UHV) transformer. (C) 2019 Elsevier Ltd. All rights reserved.