ABB Relion 650 Series Commissioning Manual page 160

Section 10
Checking the directionality
If the directional function shows forward when it should show reverse (or vice-versa) for all the
three phases, this probably means a wrong connection of CTs and/or VTs serving the distance
protection, or it can mean a wrong setting of earthing point (the setting name is : CTStarPoint)
for all the three CTs, or it could mean a wrong setting for the pre-processing blocks
(3PhaseAnalogGroup under the HMI menu: Main menu /Configuration /Analog modules )
connected to the CTs/VTs and serving the distance protection (verify that no wrong negation has
been set; the setting name is: Negation).
If the directional function shows "No direction" for all the three phases it can mean that the load
current is below the minimum operating current or that the load impedance has an angle which
is outside the above given valid angles for determining forward or reverse direction.
If the directional function shows "No direction" for only some of the three phases, this probably
means a wrong CTs/VTs connection.
4. The measured values are shown any time the load current is higher than 3% of the base
current:
•
•
•
•
•
•
The measured impedance information can still be used to determine the direction of the load. A
positive resistance measured in all phases indicates a forward (exporting) resistive load (active
power), while a negative sign indicates a reverse (importing) resistive load (active power).
Usually it is enough to look at the resistive values to get information of the load direction, that
must anyway be compared with the indication given by external equipment measuring the same
power flow.
154
L1R
L1X
L2R
L2X
L3R
L3X
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1MRK 505 395-UEN Rev. G
Line differential protection RED650
Commissioning manual