•
L1Dir = Forward
•
L2Dir = Forward
•
L3Dir = Forward
The following will be shown if the load current flows in the reverse direction (importing):
•
L1Dir = Reverse
•
L2Dir = Reverse
•
L3Dir = Reverse
Compare this result with the information given by the external equipment, it must be the
same. If the direction of the three phases is not the same, this is a sign of incorrect
connection of the voltage or current transformers serving the distance protection
function. It is also possible that there is a wrong setting for the earthing point for one or
more of the CTs serving distance protection (the setting name is:
CTStarPoint available
under the HMI menu:Main menu/Configuration/Analog modules).
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 impedance information is available under the same menu. These values are
not affected by the minimum operating current setting of ZDRDIR or ZDMRDIR and the
measured values are shown any time the load current is higher than 3% of the base
current:
•
L1R
•
L1X
•
L2R
•
L2X
•
L3R
•
L3X
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.
Section 13
1MRK 502 067-UEN B
Checking the directionality
234
Commissioning manual
