The threshold value of, r1/ r2 so that partial breakdown can be avoided in a cylindrical geometry.
Figure 6 shows the variation of g using coaxial cylinder geometry for various inner conductor diameters with a fixed outer conductor diameter and constant voltage of 11 kV between inner and outer cylinders.
When r1/r2 is equal to or less than 0.368 an increase in r1 increases the electrical field. If r1/r2 > 0.368, then corona
forms [20].
Two primary conductor diameters, namely dl and dh, are chosen to study the effect of the primary conductor diameter on the frequency response of the PFCT.
Primary conductor diameter dl lies below the threshold and dh lies above the threshold in such a way that the breakdown strength of air is not reached at the specified voltage level.
From the inner radius of PFCT, r2 = 37.5 mm, two primary conductor radii namely (rl = 13.8mm, dl=27.6mm) and (rh =
22.9mm, dh =45.8mm) are chosen to study the effect of the primary conductor diameter on the frequency response of the PFCT obtained from Figure 6.