Use the following block transformer data:
VBase
: 20 kV (low voltage side)
SBase set to 200 MVA
e
k
: 15%
Short circuit power from the external network without infeed from the protected line:
5000 MVA (assumed to a pure reactance).
W
e have all phase voltages and phase currents available and fed to the protection IED.
Therefore it is recommended to set the MeasureMode to positive sequence.
The impedance settings are set in pu with ZBase as reference:
2 2
20
2.0
200
UBase
ZBase ohm
SBase
= = =
EQUATION1969 V1 EN-US (Equation 403)
2 2
20 20
( ) ( ) 0.15 0.38
200 5000
ZA Z transf Zsc network j j j ohm= + = × + =
EQUATION1970 V1 EN-US (Equation 404)
This corresponds to:
0.38
0.19 0.19 90
2.0
j
ZA j pu pu= = = Ð °
EQUATION1971 V1 EN-US (Equation 405)
Set ZA to 0.19
2
20
' 0.25 0.5
200
d
ZB jX j j ohm= = × =
EQUATION1972 V2 EN-US (Equation 406)
This corresponds to:
0.5
0.25 0.25 90
2.0
j
ZB j pu pu= = = Ð °
EQUATION1973 V1 EN-US (Equation 407)
Set ZB to 0.25
Section 8 1MRK 504 163-UUS A
Impedance protection
478 Transformer protection RET670 2.2 ANSI
Application manual
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