ABB REG670 Commissioning Manual page 295

1MRK 502 073-UUS A
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Commissioning manual
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 14
Checking the directionality
289