ABB Relion 670 series - Series Compensated and Adjacent Lines

covers the overreaching zone, used at the remote line IED for the telecommunication
purposes.
Consider the possible enlarging factor that might exist due to fault infeed from adjacent
lines. The equation can be used to calculate the reach in reverse direction when the zone
is used for blocking scheme, weak-end infeed, and so on.
Zrev 1.2 × (Z2rem - ZL)
>
_
GUID-ABFB1C53-F12A-45D5-90CC-907C9FA0EFC3 V1 EN (Equation 381)
Where:
ZL is the protected line impedance.
Z2rem is the zone 2 setting (zone used in the POTT scheme) at the remote end of the protected line.
In many applications it might be necessary to consider the enlarging factor due to the fault
current infeed from adjacent lines in the reverse direction in order to obtain certain
sensitivity.
8.13.4.5 Series compensated and adjacent lines
Setting of zone 1
A voltage reversal can cause an artificial internal fault (voltage zero) on faulty line as well
as on the adjacent lines. This artificial fault always have a resistive component, this is
however small and can mostly not be used to prevent tripping of a healthy adjacent line.
An independent tripping zone 1 facing a bus which can be exposed to voltage reversal
have to be set with reduced reach with respect to this false fault. When the fault can move
and pass the bus, the zone 1 in this station must be blocked. Protection further out in the
net must be set with respect to this apparent fault as the protection at the bus.
Different settings of the reach for the zone (ZMFCPDIS, 21) characteristic in forward and
reverse direction makes it possible to optimize the settings in order to maximize
dependability and security for independent zone1.
Due to the sub-harmonic oscillation swinging caused by the series capacitor at fault
conditions the reach of the under-reaching zone 1 must be further reduced. Zone 1 can only
be set with a percentage reach to the artificial fault according to the curve in
103
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 423
Application manual