Hitachi RET670 Commissioning Manual page 292

Section 13
Checking the directionality
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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:
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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.
286
L1Dir = Reverse
L2Dir = Reverse
L3Dir = Reverse
L1R
L1X
L2R
L2X
L3R
L3X
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Transformer protection RET670
Commissioning manual