GE Multilin 565 - Page 62

5-18
Location Message Line Description
S 3.1
SETPOINTS
GROUND CURRENT
The setpoints page 3 header. In this page the setpoints which determine
the ground current protection are entered.
S 3.2
GROUND CURRENT
SENSING ENABLED
This message allows the user to enable or disable the Ground Current
protection.
Only message S 3.19 will appear if DISABLED is selected in message S 3.2.
S 3.3
SENSING SYSTEM
RESIDUAL
This message is asking if your system uses a separate zero sequence CT
or if the phase CT’s are connected in a residual sensing configuration to
detect ground currents. Either RESIDUAL or ZERO SEQ can be selected.
Select the one corresponding to your sensing system.
Message S 3.4 will only appear if ZERO SEQ was selected in Message S 3.3.
S 3.4
CT RATIO PRIMARY
100 A
This message asks for the primary ratio of the zero sequence transformer
being used in your application. The range of values for this setpoint is 10 to
5000 in steps of 5 Amp. This value will be on the transformer nameplate.
S 3.5
GROUND TIMED O/C
PICKUP 40% CT
The ground overcurrent pickup level is entered here as a percentage of the
CT rating. The range of values allowed is 5% to 150% in steps of 1%. This
setpoint sets the level of current at which the 565 Relay initiates a timed
trip of the feeder breaker according to the curve selected in message S
3.6.
For example, if 50% is entered here, then the 565/575 Relay will initiate a
programmed trip of the feeder breaker when the ground current reaches
50% of the full CT rating. The CT rating used will be either:
1) The phase CT primary rating entered in message S 2.2, if residual
current sensing is chosen in message S 3.3.
2) The zero sequence CT primary rating, if zero sequence sensing is
chosen in message S 3.3.
If the ground current exceeds the limits of the Time/Overcurrent curve in
use, a feeder breaker trip will occur. Determine the ground current pickup
level for your application according to the grounding system used.
S 3.6
GND O/C CURVE
SHAPE:EXTREM INV
The shape of the required ground current protection curve must be
entered here. The available curves are shown below, together with the
shortened form of the name which is displayed in the message.
CURVE DISPLAYED
NAME NAME
1. Moderately Inverse MOD INV.
2. Normal Inverse NORMAL INV.
3. Very Inverse VERY INV.
4. Extremely Inverse EXTREM INV.
5. Custom Curve CUSTOM.
6. IEC IEC A
7. IEC IEC B
8. IEC IEC C
SETPOINTS MODE - GROUND CURRENT