3–14 469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUALCHAPTER 3: INSTALLATIONFIGURE 3–14: Residual Ground CT ConnectionThe 469 measures up to 5 A secondary current if the 1 A / 5 A tap is used. Since theconversion range is relatively small, the 1 A or 5 A option is field programmable. Properselection of this settings ensures proper reading of primary ground current. The 1 A / 5 Aground CT chosen must be capable of driving the 469 ground CT burden (see Specificationson page 2–6). The 469 measures up to 25 A of primary ground current if this tap is used inconjunction with the GE Multilin core balance CT.NoteThe zero-sequence connection is recommended. Unequal saturation of CTs, size andlocation of motor, resistance of power system and motor core saturation density, etc.,may cause false readings in the residually connected GF circuit.NoteOnly one ground input should be wired – the other input should be unconnected.The exact placement of a zero-sequence CT to detect only ground fault current is shownbelow. If the core balance CT is placed over shielded cable, capacitive coupling of phasecurrent into the cable shield during motor starts may be detected as ground current unlessthe shield wire is also passed through the CT window. Twisted pair cabling on the zero-sequence CT is recommended.
