Setting Guidelines; General - ABB RELION 670 SERIES Applications Manual

Line distance protection

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Impedance protection

ANSIEQUATION-1750 V1 EN

is the line impedance from the A respective C station to the T point.

is fault current from A respective C station for fault between T and B.

Transformation ratio for transformation of impedance at V1 side of the transformer to the

measuring side V2 (it is assumed that current and voltage distance function is taken

from V2 side of the transformer).

For this example with a fault between T and B, the measured impedance from the T point

to the fault will be increased by a factor defined as the sum of the currents from T point to

the fault divided by the IED current. For the IED at C, the impedance on the high voltage

side V1 has to be transferred to the measuring voltage level by the transformer ratio.

Another complication that might occur depending on the topology is that the current from

one end can have a reverse direction for fault on the protected line. For example, for faults

at T the current from B might go in reverse direction from B to C depending on the system

parameters (see the dotted line in figure 130), given that the distance protection in B to T

will measure wrong direction.

In three-end application, depending on the source impedance behind the IEDs, the

impedances of the protected object and the fault location, it might be necessary to accept

zone 2 trip in one end or sequential trip in one end.

Generally for this type of application it is difficult to select settings of zone 1 that both

gives overlapping of the zones with enough sensitivity without interference with other

zone 1 settings, that is, without selectivity conflicts. Careful fault calculations are

necessary to determine suitable settings and selection of proper scheme communication.

Setting guidelines

The settings for Full-scheme distance protection, mho characteristic function

(ZMHPDIS) 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 ZMHPDIS.

The following basics should be considered, depending on application, when doing the

setting calculations:

1MRK 506 369-UUS -

(Equation 170)

Line distance protection REL670 2.2 ANSI

Application manual