For a generator with n stages, one has to apply Ci = Ci/n and R t = n Rt
(Eq. 7.5). The total load Cl = Clb ? Clt is the sum of the basic load and the test
object load. The fixed series inductance Ls replaces the front (damping) resistors.
According to IEC 60060-3:2006, impulse voltages with oscillations f0[ 15 kHz
are considered as ‘‘oscillating lightning impulse (OLI) voltages’’ (Fig. 7.16a), such
with f0 15 kHz as ‘‘oscillating switching impulse (OSI) voltages’’ (Fig. 7.17a).
The damping is determined by the losses in the circuit, for pure capacitive test
objects mainly by the tail resistors Rt of the aperiodic impulse. As these are higher
for OSI than for OLI voltages, OSI voltages show not only a lower frequency, but
also a larger damping (Fig. 7.17a).
Theoretically, the oscillating impulse voltage (OLI or OSI) can reach a peak
value which is twice the peak value of the relevant aperiodic impulse (LI or SI)
voltage. In practice, it reaches about 90 % of that value. The efficiency factors are