ABB Relion 670 series - Fault Infeed from Remote End

0 1
X 3 X< ×
EQUATION2122 V1 EN (Equation 337)
0 1
R R£
EQUATION2123 V1 EN (Equation 338)
Where
R
0
is the resistive zero sequence of the source
X
0
is the reactive zero sequence of the source
R
1
is the resistive positive sequence of the source
X
1
is the reactive positive sequence of the source
The magnitude of the ground-fault current in effectively grounded networks is high
enough for impedance measuring elements to detect ground faults. However, in the same
way as for solidly grounded networks, distance protection has limited possibilities to
detect high resistance faults and should therefore always be complemented with other
protection function(s) that can carry out the fault clearance in this case.
High impedance grounded networks
In this type of network, it is mostly not possible to use distance protection for detection and
clearance of ground faults. The low magnitude of the ground fault current might not give
pickup of the zero-sequence measurement elements or the sensitivity will be too low for
acceptance. For this reason a separate high sensitive ground fault protection is necessary
to carry out the fault clearance for single phase-to-ground fault.
8.13.2.2 Fault infeed from remote end
All transmission and most sub-transmission networks are operated meshed. Typical for
this type of network is that fault infeed from remote end will happen when fault occurs on
the protected line. The fault current infeed will enlarge the fault impedance seen by the
distance protection. This effect is very important to keep in mind when both planning the
protection system and making the settings.
The equation for the bus voltage V
A
at A side is:
( )A A L A B fV I p Z I I R= × × + + ×
EQUATION1273 V1 EN (Equation 339)
If we divide V
A
by I
A
we get Z present to the IED at A side:
Section 8 1MRK 506 369-UUS -
Impedance protection
386 Line distance protection REL670 2.2 ANSI
Application manual