ABB Relion 670 series - Setting Guidelines; General; Setting of Zone1

blocked for the short period. The disadvantage is that a local communication is needed
between two protection devices in the neighboring bays of the same substation.
Distance protection used on series compensated lines must have a high overreach to cover
the whole transmission line also when the capacitors are bypassed or out of service. When
the capacitors are in service, the overreach will increase tremendously and the whole
system will be very sensitive for false teleprotection signals. Current reversal difficulties
will be accentuated because the ratio of mutual impedance against self-impedance will be
much higher than for a non-compensated line.
If non-unit protection is to be used in a directional comparison mode, schemes based on
negative sequence quantities offer the advantage that they are insensitive to mutual
coupling. However, they can only be used for phase-to-ground and phase-to-phase faults.
For three-phase faults an additional protection must be provided.
8.1.3 Setting guidelines
8.1.3.1 General
The settings for the distance protection function are done in primary values. The
instrument transformer ratio that has been set for the analog input card is used to
automatically convert the measured secondary input signals to primary values used in the
distance protection function.
The following basics should be considered, depending on application, when doing the
setting calculations:
• Errors introduced by current and voltage instrument transformers, particularly under
transient conditions.
• Inaccuracies in the line zero-sequence impedance data, and their effect on the
calculated value of the ground-return compensation factor.
• The effect of infeed between the IED and the fault location, including the influence
of different Z0/Z1 ratios of the various sources.
• The phase impedance of non transposed lines is not identical for all fault loops. The
difference between the impedances for different phase-to-ground loops can be as
large as 5-10% of the total line impedance.
• The effect of a load transfer between the IEDs of the protected fault resistance is
considerable, the effect must be recognized.
• Zero-sequence mutual coupling from parallel lines.
8.1.3.2 Setting of zone1
The different errors mentioned earlier usually require a limitation of the underreaching
zone (normally zone 1) to 75 - 90% of the protected line.
Section 8 1MRK 506 369-UUS -
Impedance protection
202 Line distance protection REL670 2.2 ANSI
Application manual