Figure 106: Positioning Of Core Balance Current Transformers - GE P4A Technical Manual

P54A/B/C/E

Figure 106: 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.
P54xMED-TM-EN-1
Cable gland
Cable box
Cable gland/shealth
earth connection
No operation
SEF
SEF
E00614
Chapter 9 - Current Protection Functions
"Incorrect"
"Correct"
Operation
211