Siemens siprotec 7SA522 - Page 99

2.2 Distance protection
99
7SA522 Manual
C53000-G1176-C155-3
For the first zone, a setting of 85 % of the line length should be applied, which results
in primary
:
X1
prim
= 0.85 · X
L
= 0.85 · 14.70 Ω= 12.49 Ω
or secondary
:
Independent Zones
Z1 up to Z5
Each zone can be set using the parameter MODE )RUZDUG or 5HYHUVH (address
 2SPRGH=,  2SPRGH=,  2SPRGH=,  2SPRGH
= and  2SPRGH=). This allows any combination of forward or reverse
graded zones. Zones that are not required, are set ,QDFWLYH.
The values derived from the grading coordination chart are set for each of the required
zones. The setting parameters are grouped for each zone. For the first zone these are
the parameters =5= (address ) specifying the impedance of the upper zenith
of the MHO circle from the origin (reach), as well as the relevant delay time settings.
For the first zone the delay times for single-phase and multiple-phase faults can be set
separately: 7SKDVH (address ) and 7PXOWLSKDVH (address ). The
first zone is typically set to operate without additional time delay.
For the remaining zones the following correspondingly applies:
=5= (address );
=5= (address );
=5= (address );
=5= (address );
For the second zone it is also possible to set separate delay times for single- and multi-
phase faults. In general the delay times are set the same. If stability problems are ex-
pected during multiple-phase faults a shorter delay time can be considered for 7
PXOWLSKDVH (address ) while a higher setting for single phase faults may be
tolerated 7SKDVH (address ).
The zone timers for the remaining zones are set with the parameters 7'(/$< (ad-
dress ), 7'(/$< (address ) and 7'(/$< (address ).
If the device is provided with the capability to trip single-pole, single-pole tripping is
then possible in the zones Z1 and Z2. While single-pole tripping usually applies to
single-phase faults in Z1 (if the remaining conditions for single-pole tripping are satis-
fied), this may also be selected for the second zone with address  7ULSSROH
=. Single pole tripping in zone 2 is only possible if this address is set to <HV. The pre-
setting is 1R.