ABB RET670 Commissioning Manual

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.
1MRK 504 165-UUS - Section 13
Checking the directionality
Transformer protection RET670 2.2 ANSI 295
Commissioning manual

ABB RET670 Specifications

General

Rated Frequency	50/60 Hz
Inputs	Analog and binary inputs
Application	Protection of power systems
Communication Protocols	IEC 61850, DNP3, Modbus
Operating Temperature Range	-25°C to +55°C
Mounting	Rack mounted
Number of Binary Inputs	Up to 48
Number of Binary Outputs	32
Protection Functions	Overcurrent Protection
Outputs	Binary outputs
Enclosure	IP 54
Type	Line Differential Protection
Number of Analog Inputs	24