Functions
2.3 Directional Gound Overcurrent Protection 67N
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
89
Measurement methods
In the tabs for each element you can specify the references values used by the corresponding element.
• Measurement of the fundamental harmonic (standard method):
This measurement method processes the sampled values of the current and filters in numerical order the
fundamental harmonic so that the higher harmonics or transient peak currents are rejected.
• Measurement of the r.m.s value
The current amplitude is derived from the sampled values in accordance with the definition equation of the
r.m.s value. This measurement method should be selected when higher harmonics are to be considered by
the function (e.g. in capacitor banks).
The type of the reference values can be set in the following addresses:
67N-2 Element Address 1620 50N-2 measurem.
67N-1 Element Address 1621 50N-1 measurem.
67N-TOC Element Address 1622 51N measurem.
Directional characteristic
The directional characteristic, i.e. the position of the ranges „forward“ and „reverse“, is set in address 1619
ROTATION ANGLE. The short-circuit angle is generally inductive in a range of 30° to 60°. This means that the
default setting of -45° for adjusting the reference voltage can usually be retained because it guarantees a safe
direction result.
With the ground directional element, the reference voltage is the short-circuit voltage itself. The resulting setting
of the angle of rotation is then:
Angle of rotation ref.voltage = -ϕ
k
directional ground element, phase-to-ground fault
Please note that for an angle of rotation of 30° the setting must be -30°.
Directional orientation
The directional orientation for the directional ground element can set to either Forward or Reverse or Non-
Directional at address 1616 67N Direction. Directional overcurrent protection normally operates in the
direction of the protected object (line, transformer, etc.).
Note
If the 67N-1 Element picks up, the phase-specific directional indications „forward“ or „reverse“ are issued (mes-
sage 2635 or 2636).
Pickup of the 67N-2 Element lies within the parameterized directional range without directional indication.
Setting the parameters for direction determination
Parameter 1617 67N POLARIZAT. can be set to specify whether direction determination is accomplished
from the zero sequence quantities, the ground quantities (with VN and IN) or the negative sequence quan-
tities (with V2 and I2) in the ground directional element. The first option is the preferential setting; the latter
is selected if there is a risk of the zero voltage becoming too small due to unfavorable zero impedance or a
parallel line influencing the zero sequence system.
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