CHAPTER 2: INSTALLATION ELECTRICAL INSTALLATION
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 2–21
CAUTION:
IMPORTANT: The phase and ground current inputs correctly measure up to 46 times the
current input’s nominal rating. Time overcurrent curves become horizontal lines for
currents above 20 × PKP.
Ground CT Inputs
The ground input (Terminals J7 and J8) is used in conjunction with a Zero Sequence CT as
source, or in the neutral of wye-connected source CTs. The ground current input can be
used to polarize both the neutral and sensitive ground directional elements. When using
the residual connection, set the GROUND
CT PRIMARY setpoint to a value equal to the
PHASE
CT PRIMARY setpoint. The sensitive ground current input is intended for use either
with a CT in a source neutral of a high-impedance grounded system, or on ungrounded
systems. On ungrounded systems it is connected residually with the phase current inputs.
In this case, the SENSTV
GND CT PRIMARY setpoint should be programmed to a value
equal to the PHASE
CT PRIMARY setpoint. The sensitive ground current input can be
connected to a Zero Sequence CT for increased sensitivity and accuracy when physically
possible in the system.
Figure 2-21: Ground Inputs
892773A2.cdr
8 Series
J1
J2
J3
J4
J5
J7
J6
J8J7 J8J8 J7
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