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EA Technology
CableData Collector Operating Manual
1365/L/01/1
11.1.3
Cable Partial Discharge (PD)
The power cables being tested for a PD event must be earthed via an earth strap to allow
measurements to be made of PD between phase and earth. Once a PD event has occurred
through the electrical insulation of a cable, a set of pulses both equal in magnitude but
opposite in polarity are seen on the line conductors and the earth conductor. In addition, if a
PD event occurs between two phases, the effect of equal magnitude and opposite polarity is
seen on the phase conductors that the PD event occurred.
It should also be noted that on XLPE cables, the PD event will normally take place on the
cable terminations and it is unlikely that a phase-to-phase PD will occur within the cable
itself. Conversely, on PILC cables the PD effect can occur more often (than on XLPE types)
between phase and phase, and the PD events can also be seen on the cables terminations.
The illustration below shows the effect of a partial discharge. However, the PD effect has
been exaggerated for the purpose of this explanation.
Figure 68 - Effect of Partial Discharge on a cable
Page 47 of 54
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