5-52 F650 Digital Bay Controller GE Multilin
5.4 PROTECTION ELEMENTS 5 SETPOINTS
5
Neutral directional element is an independent Protection unit that provides block and Operation signals. These signals can
be monitored both through the relay HMI or using EnerVista 650 Setup at “Actual > Status > Protection > Neutral
Current”
67N Block (NEUTRAL DIR BLOCK): It indicates that the unit is blocked by digital input or because the Operation magnitude
(In current), or the Polarization magnitude (Vn voltage and/or Ip current) level is too low.
67N Operation (NEUTRAL DIR OP): It indicates that the directional unit is giving permission, that the angle
relations between the operation magnitude and the polarization magnitude are met, according to the set
conditions, or in case of having selected Permission in the Block Logic setpoint, it indicates that the unit allows
operation under block conditions.
a) VOLTAGE POLARIZATION OPERATION PRINCIPLES:
Operation Magnitude: In = 3·Io, calculated from the phase currents.
Polarization Magnitude
: -3V
0
. Calculated from the phase voltages or measured at the input terminals (A11, A12).The
relay measures 3V
0
and rotates 180º internally to obtain -3V
0
.
Figure 2–12: shows the operation of the zero sequence polarization, 3V
0
, in case of an AG fault. In this case, the
polarization magnitude 3V
0
can be calculated from the three phase voltage values, or measured through the fourth voltage
input (Vx). In this last case, voltage transformer must be wye connected, and the Auxiliary Voltage setpoint in General
setpoints must be configured as VX. The operation magnitude 3I
0
, is calculated from the phase currents.
When Ip Polarization is selected, the Polarization magnitude is Ip, the current value measured at the fifth current input
(terminals B11-B12). This polarization current must usually come from a CT metering the current that flows from the ground
to the neutral of the neutral fault current source, which will mainly be a transformer. The direction is considered to be
Forward when the neutral current 3I
0
is inside a ±90º arc at both sides of the polarization current. In any other case, the
direction will be Reverse. If the polarization current is lower than 5 mA, the unit output takes the value of the Block Logic
setpoint.VOLTAGE POLARIZATION
NEUTRAL DIRECTIONAL
NEUTRAL DIR1 BLOCK
NEUTRAL DIR1 OP
NEUTRAL DIR2 BLOCK
NEUTRAL DIR2 OP
NEUTRAL DIR3 BLOCK
NEUTRAL DIR3 OP
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