EA Technology
CableData Collector Operating Manual
1365/L/01/1
Page 45 of 54
11
Using the CableData Collector
Using the RFCT for online Partial Discharge (PD) tests on medium voltage power cables is
relatively straightforward and very safe, as the current transformer is simply clamped around
the earth cable using its split core as illustrated in Figure 67. This method can be used on-
line without disconnecting cables or switching off supplies to customers.
11.1
Connecting the RFCTs
11.1.1
Practical RFCT Connection Requirements
When completing an online PD test, the plant item must allow access to the earth strap and
there must be insulation between the switchgear earth and the cable earth.
With XLPE cable installations the user can normally get access to the cable earth strap or
the core of the cables. The earth strap can be looped out of the termination box to give
better access.
With PILC (Paper Insulated Lead Covered) cables difficulty may arise attaching the RFCT
unit as the cable earth and switchgear earth can be bonded together. This is more usual on
older PILC cables using compound filled cable boxes. The placement of the RFCT is then
not possible until an insulated gland has been installed with an earth strap bridging the gland
in order to earth the cable and the switchgear earth together, so as to allow a PD test.
11.1.2
Testing Three Phase Cables
When using the CableData Collector to test thr
ee phase cables with three RFCT’s, the
arrows on the RFCT must all point in the same direction. This ensures that the polarity of the
RFCT’s are all the same which means that any PD pulses captured which are common
across the three cables will all be in the same polarity aiding in detection and classification of
the discharge.
Figure 67 - RFCT Connection
RFCT
RFCT
Insulation
Lug
Earth Cable
Earth Cable
Bottom View
Side View
Switch Gear
Housing
Power Cable
