SEF
E00614
Cable box
Cable gland
Cable gland/shealth
earth connection
“Incorrect”
No operation
“Correct”
Operation
SEF
Figure 67: Positioning of core balance current transformers
If the cable sheath is terminated at the cable gland and directly earthed at that point, a cable fault (from phase to
sheath) will not result in any unbalanced current in the core balance CT. Therefore, prior to earthing, the
connection must be brought back through the CBCT and earthed on the feeder side. This then ensures correct
relay operation during earth fault conditions.
Chapter 6 - Current Protection Functions P14x
138 P14xEd1-TM-EN-1
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