Different to the above procedure, the pulse-shaped noises shown in Fig. 4.47b could also be eliminated after the actual PD measurement has been finished using a ‘‘windowing’’ tool. This is because the phase angle of the noisy pulses received from the converter is very different from those of the PD events. An example for this is shown in Fig. 4.48 using both the 2D and the 3D display modes. In this context, it should be noted that most of digital PD measuring systems are not equipped with the hardware required for an automatic gating of the PD signal but