Corona Q-V characteristics under unipolar-damped oscillating impulses [substations]

Most incoming surges to substations are of the UDOI (unipolar damped oscillating impulse) type, yet there is very little data in the literature on the corona characteristics (q-V curves) of this type of impulse wave. Corona characteristics under unipolar damped oscillating impulse were tested in a corona cage and on a CP (conductor-plane) setup. Effective measures were developed to suppress the interferences which occurred in the test and measurement systems. Features of the q-V curves were obtained using UDOI both in the corona cage and on the CP setup and these features were compared with those under DEI (double exponential impulse). Special features examined include the hysteresis-like q-V curve under UDOI, the average dynamic capacitance of the coronating conductor, the energy dissipated by corona, q-V curves of single and conductor bundles under UDOI on the CP setup and the effect of the number of subconductors on the q-V curve (especially negative polarity). The applicability of the concept of a single conductor equivalent to a conductor bundle is discussed.