Aging of the over-voltage protection elements caused by over-voltages
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The aim of this work is examining the influence of the number of the activation-over-voltage pulses to the aging of over-voltage protection elements. Both non-linear (gas-filled surge arresters (GFSA), varistors, over-voltage diodes) and linear (capacitors-constituents of filters) over-voltage protection elements were tested. The instruments employed allow reliable measurements, 1000 consecutive activation were tested. The double-exponential current pulse (amplitude I-1(max) = 13 A, I-2(max) = 16 A, rise time T-1 = 8 mus, fall time T-2 = 20 mus) for non-linear elements and a double-exponential over-voltage pulse (rise time T-1 = 1.2 mus, fall time T-2 = 50 mus) of the amplitude U-1(max) = 320 V, U-2(max) = 480 V and U-3(max) = 640 V for capacitors were used. The experimental results show that the over-voltage diodes are the most reliable elements in view of characteristic modifications that are consequence of aging. However, it was observed that varistors, GFSA and capacitors undergo n...oticeable changes in characteristics. (C) 2002 Elsevier Science Ltd. All rights reserved.