where Ic and Ir are the capacitive and resistive components of the total leakage current It .It was shown [167] that the instantaneous resistive current magnitude at two instants t1 and t2 corresponding to the same level of voltage on the cycle can be expressed as:
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This equation allows the calculation of the resistive current around the cycle for any waveshape. If the voltage is sinusoidal with no harmonic content or with only odd harmonics without phase shift, it can be shown that:
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Figure 5.26 shows typical examples obtained with this discrimination technique on
a 15 kV surge arrester in the low and high conduction regimes. As can be seen, both the resistive and capacitive components show non-linearities.