Inproceedings,
Measurement of Damages at Bypass Diodes by Induced Voltages and Currents in PV Modules Caused by Nearby Lightning Currents with Standard Waveform
(2008)
Abstract
In 1990 â 1993 and during an EU project in 1998 â 2000, the PV
laboratory of BFH-TI has carried out tests about sensitivity of PV
modules against lightning currents flowing in or close to the frame
of a PV module 1, 2, 3. For these tests, impulse currents with
imax â? 120kA and di/dtmax â? 40kA/Î?s were used. It could be shown
that even at moderate distances the voltages induced in a module
by such lightning currents may go up to several thousand volts. Such
voltages can easily destroy bypass diodes. Due to increasing cell
dimensions and currents, more and more Schottky diodes are used as
bypass diodes, which have only quite low reverse voltage ratings
between 40 V and 100 V. In practical operation, such damages actually
occur, but usually only at considerably higher peak induced voltages
than the reverse voltage rating of the Schottky diode. In 5 and
7 the problem was analysed theoretically and the results of some
first tests with short impulse currents (about 8Î?s/20Î?s) were shown.
In this paper, the theoretical analysis is extended and results of
many measurements performed in 2007 and 2008 with impulse current
waveforms of about 6Î?s/350Î?s (di/dtmax â? 30kA/Î?s) at different
modules and with different diode types are presented.
