Discharge detection under noisy conditions

The smallest discharge which may be detected during partial discharge tests on electrical equipment is usually determined by the levels of background interference. To improve the signal/noise ratio the real-time computational technique known as signal recovery has been used. This has the additional advantage that the end result is a permanent record which will allow the user to reliably compare discharge characteristics throughout a component's life. While the approach is applicable to any component, the experimental evaluation programme was based on 11 kV polymer-insulated cable. This was tested in various situations, namely, as a short length in the laboratory, as drum lengths in several factories, and lengths (together with associated switchgear) installed in a number of power stations. In these conditions, discharges of 1 pC and less could be detected, even where the noise levels on conventional display-only equipment were tens of picocoulombs.