PD characteristics and mechanisms in artificial air-filled voids at room and liquid nitrogen temperatures [comment and reply]

For original paper see Tsuru et al, ibid., vol.6, p.43 (1999). Tsuru et al. studied discharge mechanisms in cavities in some specific test samples at room and liquid nitrogen temperatures. They claimed that the sensitivity of their partial discharge (PD) measurements was 3 pC, while that of the phase-resolved measurement was 10 pC. Danikas thinks that such sensitivities are rather low if one wants to investigate in detail the mechanisms of PD in air-filled cavities. Tsuru et al reply to the comments.