GE Multilin 565 Instruction Manual page 62

SETPOINTS MODE - GROUND CURRENT
Location Message Line
S 3.1
SETPOINTS
GROUND CURRENT
S 3.2
GROUND CURRENT
SENSING
Only message S 3.19 will appear if DISABLED is selected in message S 3.2.
S 3.3
SENSING SYSTEM
RESIDUAL
Message S 3.4 will only appear if ZERO SEQ was selected in Message S 3.3.
S 3.4
CT RATIO PRIMARY
S 3.5
GROUND TIMED O/C
PICKUP
S 3.6
GND O/C CURVE
SHAPE:EXTREM INV
5-18
Description
The setpoints page 3 header. In this page the setpoints which determine
the ground current protection are entered.
This message allows the user to enable or disable the Ground Current
protection.
ENABLED
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.
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
100 A
5000 in steps of 5 Amp. This value will be on the transformer nameplate.
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
40% CT
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
2) The zero sequence CT primary rating, if zero sequence sensing is
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.
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
NAME
1. Moderately Inverse
2. Normal Inverse
3. Very Inverse
4. Extremely Inverse
5. Custom Curve
6. IEC
7. IEC
8. IEC
current sensing is chosen in message S 3.3.
chosen in message S 3.3.
DISPLAYED
NAME
MOD INV.
NORMAL INV.
VERY INV.
EXTREM INV.
CUSTOM.
IEC A
IEC B
IEC C