EA Technology CableData CDC2, Руководство по эксплуатации

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EA Technology CableData Collector Operating Manual 1365/L/01/1
Page 49 of 54
Figure 70 - Overcoming cancellation of discharge currents by looping back earth strap
11.1.5 Cable Type Restrictions
In cable types like the XLPE, the phase cores are separately screened. On belted cables,
there is a common screen around the three phases. This is important because on belted
cables phase-to-phase voltages exist, whereas on XLPE cables this is not the case.
On the 3-phase 6.6kV
– 11kV belted cable types, the RFCT will not see a PD occurring
between phases when placed over the earth strap, as the discharge current flows only in the
phase conductor.
The implications for online PD tests for belted cables is that only phase to ground PD
measurements can be taken, with the phase to phase measurements not being possible
unless access to the individual cores is obtained.