GE t60 Instruction Manual page 175

5 SETTINGS
and polarizing signal simultaneously. Therefore, "Voltage" is the only applicable selection for the polarizing mode under
the "Measured IG" selection of this setting.
• NEUTRAL DIR OC1 OFFSET: This setting specifies the offset impedance used by this protection. The primary appli-
cation for the offset impedance is to guarantee correct identification of fault direction on series compensated lines. See
the Chapter 9 for information on how to calculate this setting. In regular applications, the offset impedance ensures
proper operation even if the zero-sequence voltage at the relaying point is very small. If this is the intent, the offset
impedance shall not be larger than the zero-sequence impedance of the protected circuit. Practically, it shall be several
times smaller. See Chapter 8 for additional details. The offset impedance shall be entered in secondary ohms.
• NEUTRAL DIR OC1 FWD ECA: This setting defines the characteristic angle (ECA) for the forward direction in the
"Voltage" polarizing mode. The "Current" polarizing mode uses a fixed ECA of 0°. The ECA in the reverse direction is
the angle set for the forward direction shifted by 180°.
• NEUTRAL DIR OC1 FWD LIMIT ANGLE: This setting defines a symmetrical (in both directions from the ECA) limit
angle for the forward direction.
• NEUTRAL DIR OC1 FWD PICKUP: This setting defines the pickup level for the overcurrent unit of the element in the
forward direction. When selecting this setting it must be kept in mind that the design uses a "positive-sequence
restraint" technique for the "Calculated 3I0" mode of operation.
• NEUTRAL DIR OC1 REV LIMIT ANGLE: This setting defines a symmetrical (in both directions from the ECA) limit
angle for the reverse direction.
• NEUTRAL DIR OC1 REV PICKUP: This setting defines the pickup level for the overcurrent unit of the element in the
reverse direction. When selecting this setting it must be kept in mind that the design uses a "positive-sequence
restraint" technique for the "Calculated 3I0" mode of operation.
SETTING
NEUTRAL DIR OC1
FUNCTION:
Disabled=0
Enabled=1
SETTING
AND
NEUTRAL DIR OC1 BLK:
Off=0
SETTING
NEUTRAL DIR OC1
SOURCE:
NEUTRAL DIR OC1 POL
VOLT:
NEUTRAL DIR OC1 OP
CURR:
Measured VX
Calculated V_0
Zero Seq Crt (I_0)
Ground Crt (IG)
SETTING
IG 0.05 pu
NEUTRAL DIR OC1
POLARIZING:
Voltage
OR
Current
Dual
OR
NOTE:
1) CURRENT POLARIZING IS POSSIBLE ONLY IN RELAYS WITH
THE GROUND CURRENT INPUTS CONNECTED TO
AN ADEQUATE CURRENT POLARIZING SOURCE
2) GROUND CURRENT CAN NOT BE USED FOR POLARIZATION
AND OPERATION SIMULTANEOUSLY
3) POSITIVE SEQUENCE RESTRAINT IS NOT APPLIED WHEN
I _1 IS BELOW 0.8pu
Figure 5–52: NEUTRAL DIRECTIONAL OC1 SCHEME LOGIC
GE Multilin
SETTING
NEUTRAL DIR OC1 FWD
PICKUP:
NEUTRAL DIR OC1 OP
CURR:
RUN
3( _0 - K _1 ) PICKUP I I
OR
IG PICKUP
SETTINGS
AND
NEUTRAL DIR OC1 FWD
ECA:
NEUTRAL DIR OC1 FWD
LIMIT ANGLE:
NEUTRAL DIR OC1 REV
LIMIT ANGLE:
NEUTRAL DIR OC1
OFFSET:
RUN
FWD
FWD
-3V_0
REV
3I_0
REV
Voltage Polarization
AND RUN
FWD
Current Polarization
REV
SETTING
NEUTRAL DIR OC1 REV
PICKUP:
NEUTRAL DIR OC1 OP
CURR:
RUN
3( _0 - K _1 ) PICKUP I I
OR
IG PICKUP
T60 Transformer Management Relay
5.5 GROUPED ELEMENTS
AND
OR
1.25 cy
AND
1.5 cy
OR
AND
5
FLEXLOGIC OPERAND
AND NEUTRAL DIR OC1 FWD
FLEXLOGIC OPERAND
NEUTRAL DIR OC1 REV
827077AA.CDR
5-97