I.L. 40-201.9
Power Automation and Protection Division
5-6
REL 352 Version 1.00
4.15
Low Set Ground Unit (IGL)
The ground unit supervises the phase comparison logic for the ground subsystem. Since the
effect of charging current is minimum for the ground subsystem, the setting should only allow
for inherent unbalance under normal operation. A minimum setting of 0.5 A is recommended.
4.16
High Set Ground Overcurrent Unit (IGH)
The high set ground unit should follow the same guidelines as the high set phase units.
The IGH unit is directional only when the optional distance back-up is included. IGH is super-
vised by FDOG.
5.
FAULT LOCATOR, BLINDERS AND DISTANCE PROTECTION COMMON
SETTINGS
5.1
Ohms per Unit Distance (XPUD)
This setting is used by the fault locator algorithm to estimate a calculated distance to the fault.
The units of XPUD will be in primary ohms per mile or ohms per kilometer, depending on the
setting of DTYP.
For Example:
Set XPUD = 0.8 if DTYP = miles and the line reactance is 0.8 Primary Ohms/mile.
5.2
Distance Unit Type for XPUD (DTYP)
Either miles (MI) or kilometers (km) should be selected. This setting should match the units
used in XPUD.
5.3
Line Positive sequence impedance setting angle (PANG)
This setting relates directly to the assumed positive sequence impedance angle of the line. It
defines the Zone 2 and Zone 3 phase impedance unit maximum torque angle in degrees. This
setting is also the complement of ZP (Phase reach) and is also used for defining the slope of
the blinders for OST and OSB and for the fault locator algorithm.
For example, if the assumed positive sequence impedance of the line is Z1 = 3.0 ohms at 75
°
,
then set PANG = 5
5.4
Line zero sequence impedance angle setting (GANG)
This setting defines the assumed impedance angle of the zero sequence (Zl0) impedance of
the transmission line. Zone 2 and Zone 3 ground impedance units use this parameter for their
operation.
For Example:
If the assumed zero sequence impedance of the line is Zl0 = 15 ohms at 80
°
then set
GANG = 80.
