Functions
2.31 100-%-Stator Earth Fault Protection with 20 Hz Voltage Injection (ANSI 64G - 100%)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
226
2.31.2 Setting Notes
General
The 100 % stator earth fault protection is only effective and available if address 153 100% SEF-PROT. is set
to Enabled during configuration.
In addition, the function requires the following settings to be made in Power System Data 1:
• Address 275: FACTOR R SEF; Sets the resistance transformation ratio (see margin title "Fault Resistances")
• Address 223: UE CONNECTION should be set to Load. resistor for the application. The 20 Hz voltage
is in this case measured at the U
E
input, and the displacement voltage for the 90 % stator earth fault protec-
tion (SEF) is calculated from the phase-to-earth voltages. If the measured voltage is to be used for the
90 % SEF as well, set either neutr. transf. or broken delta.
Address 5301 100% SEF-PROT. serves to switch the function ON or OFF or to block only the trip command
(Block relay).
Fault Resistances
The final setting values are determined in the primary test as described in Section 3 Subsection „Commission-
ing“.
Please note that the protection calculates the earth resistance from the secondary values USEF and ISEF
which are present at the device terminals. Allocation between this calculated value and the actual (primary)
stator earth resistance is determined by the transformation ratio of the earthing and the neutral transformer. For
the overall transformation, the following formula applies:
Definitions:
The conversion factor of the earth resistance is set as FACTOR R SEF at address 275 in Power System Data
1. The general formula for calculation (R
Eprim
/ R
Esec
) is:
R
Esec
Earth resistance, converted to the device side
R
Eprim
Primary earth resistance of the stator winding (= fault resistance)
Tr
Ratio
Transformation ratio of the earthing or neutral transformer
Earthing transformer (leg transformation divided by 3):
Neutral transformer:
CT
Ratio
Transformation ratio of the miniature CT
VD
Ratio
Division Ratio of the Voltage Divider
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