Functions
2.3 Directional Overcurrent Protection Ground 67, 67N
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
97
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-3 Element address 1627 67N-3 MEASUREM.
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 Forward or Reverse can be set separately for each element. Moreover, each
element can also be operated Non-Directional.
• Address 1626 67N-3 Direction
• Address 1623 67N-2 Direction
• Address 1624 67N-1 Direction
• Address 1625 67N-TOC Direct.
The directional overcurrent protection usually works in direction towards the protected object (line, transform-
er).
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 or 67N-3Element lies within the parameterized directional range without direction-
al indication.
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