Neutral Dir Oc1 Pol Volt; Neutral Dir Oc1 Op Curr; Neutral Dir Oc1 Pos-Seq Restraint; Neutral Dir Oc1 Fwd Eca - GE T60 Instruction Manual

5.6 GROUPED ELEMENTS
– If "Dual-V" polarizing is selected, "Voltage" polarizing is performed and "Current" polarizing is ignored if the voltage
polarizing signal is valid; otherwise "Current" polarizing is performed if the current polarizing signal is valid. If nei-
ther of them is valid, neither forward nor reverse indication is given.
– If "Dual-I" polarizing is selected, "Current" polarizing is performed and "Voltage" polarizing is ignored if the current
polarizing signal is valid; otherwise "Voltage" polarizing is performed if the voltage polarizing signal is valid. If nei-
ther of them is valid, neither forward nor reverse indication is given.
• NEUTRAL DIR OC1 POL VOLT: Selects the polarizing voltage used by the directional unit when "Voltage," "Dual,"
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"Dual-V," or "Dual-I" polarizing mode is set. The polarizing voltage can be programmed to be either the zero-sequence
voltage calculated from the phase voltages ("Calculated V0") or supplied externally as an auxiliary voltage ("Measured
VX").
• NEUTRAL DIR OC1 OP CURR: This setting indicates whether the 3I_0 current calculated from the phase currents, or
the ground current shall be used by this protection. This setting acts as a switch between the neutral and ground
modes of operation (67N and 67G). If set to "Calculated 3I0" the element uses the phase currents and applies the pos-
itive-sequence restraint; if set to "Measured IG" the element uses ground current supplied to the ground CT of the CT
bank configured as
setting must be "Voltage", as it is not possible to use the ground current as an operating and polarizing signal simulta-
neously. IG current has to be above 0.05 ps to be used as operate quantity.
• NEUTRAL DIR OC1 POS-SEQ RESTRAINT: This setting controls the amount of the positive-sequence restraint. Set
to 0.063 for backward compatibility with firmware revision 3.40 and older. Set to zero to remove the restraint. Set
higher if large system unbalances or poor CT performance are expected.
• 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. 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. 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.
5-240
. If this setting is "Measured IG", then the
NEUTRAL DIR OC1 SOURCE
T60 Transformer Protection System
5 SETTINGS
NEUTRAL DIR OC1 POLARIZING
GE Multilin