module 3BSE004172R1

module 3BSE004172R1

module 3BSE004172R1

The zone 1 distance elements must be set to underreach a protected circuit to ensure external fault security. The different errors mentioned earlier usually require a limitation of the underreaching zone (normally zone 1) to 75 – 90% of the protected line.

In case of parallel lines, consider the influence of the mutual coupling according to section “Setting of zones for parallel line application” and select the case(s) / options that are valid in the particular application.

By proper setting it is possible to compensate for the cases when the parallel line is in operation, out of service and not earthed and out of service and earthed in both ends. 7.4.3.3 Setting of zone 2 Zone 2 distance elements must be set according to the following criteria:

• Zone 2 should overreach all terminals of the protected circuit by an acceptable margin (typically 20% of highest impedance seen) for all fault conditions and for all intended modes of system operation

• As far as possible, zone 2 reach should be less than zone 1 coverage of all adjacent lines to minimize the required zone 2 time delay setting. It is necessary to consider the underreaching effects of zero sequence mutual coupling on earth-fault impedance measurement when setting the reach of zone 2 distance protection to meet the primary reach criterion for parallel circuits.