Siemens siprotec 7SA6 User Manual page 406

Functions
6-224
not always correct, as the measured values can be distorted by e.g. intermediate
infeeds.
To calculate the distance to fault in kilometres or miles, the device requires the
reactance per unit length data in Ω/km or Ω/mile. For correct indication of the fault
location in % of line length, the correct line length should also be entered. These
setting parameters were already applied with the plant data (Section 6.1.3 under
"General Line Data").
A prerequisite for the correct indication of the fault location furthermore is that the other
parameters that influence the calculation of the distance to fault have also been set
correctly. These are the addresses (refer also to Sub-section 6.1.3)
 5(5/ = ,
 ;(;/ =
or
 . = ,
 3+, . = .
If the parallel line compensation is used, the address  must be set to
3DUDO/LQH &RPS = <HV; the presetting is 1R. Further prerequisites are that
• the earth current of the parallel line has been connected to the fourth current input
I with the correct polarity and
4
• the parameter for the fourth current input , WUDQVIRUPHU has been set to ,Q
SDUDO OLQH (address ) in the "power system data 1" (refer also to Sub-
section 6.1.1 under "Current Transformer Connection") and
• the current transformer ratio ,,SK &7 (address ) in the "power system data
1" has been set correctly (refer also to Sub-section 6.1.1 under "Current
Transformer Connection") and
• the mutual impedances 505/ 3DUDO/LQH and ;0;/ 3DUDO/LQH (addresses
 and ) have been set correctly in the general protection data ("power
system data 2", refer to Sub-section 6.1.3).
If load compensation is applied to single-phase faults in double-fed lines of an earthed
system, set <HV in address  /RDG &RPSHQVDW. In case high fault resistances
are expected for single-phase faults, e.g. at overhead lines without overhead earth
wire or unfavourable footing of the towers, this will improve the accuracy of the
distance calculation.
If the fault location is required to be output as BCD-code, set the maximum time period
the data should be available at the outputs using address  7PD[ 287387 %&'.
If a new fault occurs, the data are terminated immediately. Allocate the corresponding
output relays as "stored" if a longer time period is desired for the output. Once a fault
occurred the data will be latched until the memory is reset or a new fault is registered.
7SA6 Manual
C53000-G1176-C133-1