Siemens siprotec 7SD5 User Manual page 49

Example:
Phase current transformers 500 A / 5 A
Earth current transformer 60 A / 1 A
• Connection of the I
• Connection of the I
• If the input I
The nominal frequency of the system is set in address 230 Rated Frequency. The
Nominal Frequency
presetting according to the ordering code (MLFB) only needs to be changed if the
device is applied in a region different to the one indicated when ordering. You can set
50 Hz or 60 Hz.
System Starpoint If the distance protection has been configured as the main protection function or in
combination with differential protection, the manner in which the system starpoint is
earthed must be considered for the correct processing of earth faults and double earth
faults. Accordingly, set for address 207 SystemStarpoint = Solid Earthed,
Peterson-Coil or Isolated. For „low-resistant" earthed systems set Solid
Earthed.
Address 236 Distance Unit determines the distance unit (km or Miles) for the
Distance Unit
fault location indications. If the compounding function of the voltage protection is used,
the overall line capacitance is calculated from the line length and the capacitance per
unit length. If compounding is not used and fault location is not available, this param-
eter is of no consequence. Changing the distance unit will not result in an automatic
7SD5 Manual
C53000-G1176-C169-1
input to the earth current of the parallel line (for parallel line
4
compensation of the distance protection and/or fault location):
Address 220 is then set to: I4 transformer = In paral. line and usually
address 221 I4/Iph CT = 1.
If the set of current transformers on the parallel line however has a different trans-
formation ratio to those on the protected line, this must be taken into account in
address 221:
Address 220 is then set to: I4 transformer = In paral. line and address
221 I4/Iph CT = I
N paral. line
Example:
Current transformers on protected line 1200 A
Current transformers on parallel line 1500 A
input to the starpoint current of a transformer; this connection
4
is occasionally used for the polarisation of the directional earth fault protection:
Address 220 is then set to: I4 transformer = IY starpoint, and address 221
I4/Iph CT is according to transformation ratio of the starpoint transformer to the
transformer set of the protected line.
is not required, set:
4
Address 220 I4 transformer = Not connected,
Address 221 I4/Iph CT is then irrelevant.
In this case, the neutral current is calculated from the sum of the phase currents.
/ I
N prot. line
2.1 General
49