ABB RELION 670 SERIES Applications Manual page 194

Section 8
Impedance protection
188
10
5
0 0.02 0.04
5
10
IEC06000610 V1 EN
Figure 86: Short circuit currents for the fault at the end of 500 km long 500 kV line
without and with SC
Location of instrument transformers
Location of instrument transformers relative to the line end series capacitors plays an
important role regarding the dependability and security of a complete protection scheme.
It is on the other hand necessary to point out the particular dependence of those protection
schemes, which need for their operation information on voltage in IED point.
Protection schemes with their operating principle depending on current measurement
only, like line current differential protection are relatively independent on CT location.
Figure 87 shows schematically the possible locations of instrument transformers related
to the position of line-end series capacitor.
- jX
C
CT 1
VT1
ANSI06000611 V1 EN
Figure 87: Possible positions of instrument transformers relative to line end series
capacitor
0.06 0.08 0.1 0.12
t[ms ]
CT 2
VT 2
en06000611_ansi.vsd
1MRK 506 369-UUS -
0.14 0.16 0.18 0.2
en06000610.vsd
Line distance protection REL670 2.2 ANSI
Application manual