11
Non discharge signals
With discharge signals
When the discharge signal detected by the switchgear cabinet PD tester is too large, the
display screen data will change into red, the sensor is saturated at this time.
Sensor saturated
4. Background noise
Instantaneous grounding voltage may occur outside of the switchgear cabinet due to the
electromagnetic signal sources. These sources can be overhead line insulators,
transformer tubing, strong radio signal even near highway traffic. These sources can
produce instantaneous earth voltage signals to the metals such as substation doors or
fences without touching or connecting. Therefore, the background noise on these
surfaces shall be measured before conducting switchgear cabinet detection.
Measure the background noise of the metal door ,fence which are not part of the
switchgear cabinet. Record down three continuous values of these metal parts, take the
intermediate amplitude as the reading for the background measurements.
5. Measurement precautions
After the main tester starts, make sure that the TEV sensor is in the free space away from