Siemens SIPROTEC 7SK80 - Page 37

Functions
2.1 General
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
37
The following table gives an overview of how the protection functions are assigned to the ground current inputs
for the special connection.
1)
Important! The function „Directional Time Overcurrent Protection Ground 67N“ may only be enabled if the
ground current of the protected line is measured via I
N2
. This is not the case in the example shown in Figure
2-3. Here, the ground current of the protected line is measured via I
N
. The function must be deactivated. A
connection in which the function can be enabled is illustrated in the Appendix A.3 Figure A-10.
The settings for address 251 are only possible with DIGSI at Display Additional Settings.
The Appendix provides some connection examples at A.3.
Note
The settings in address 251 CT Connect. for evaluating the phase currents are only effective if address 250
50/51 2-ph prot was set to OFF.
Voltage Transformer Connection (Power System Data)
Address 213 specifies how the voltage transformers are connected.
VT Connect. 3ph = Van, Vbn, Vcn means that the three phase voltages are wye connected, i.e. the three
phase-to-ground voltages are measured.
VT Connect. 3ph = Vab, Vbc, VGnd means that two phase-to-phase voltages (open-delta-connection)
and the displacement voltage V
gnd
are connected.
VT Connect. 3ph = Vab, Vbc means that two phase-to-phase voltages (open-delta-connection) are con-
nected. The third voltage transformer of the device is not used.
VT Connect. 3ph = Vab, Vbc, Vx means that two phase-to-phase voltages (open-delta-connection) are
connected. Furthermore, any third voltage V
x
is connected that is used exclusively for the flexible protection
functions. The transformer nominal voltages for V
x
are set at address 232 and 233.
The selection of the voltage transformer connection affects the operation of all device functions that require
voltage input.
The settings Vab, Vbc or Vab, Vbc, Vx do not allow determining the zero voltage. The associated protec-
tion functions are inactive in this case.
Function Current input 2
(I
N2
)
Current input 4
(I
N
/ I
Ns
)
Time overcurrent protection ground 50N/51N (Section 2.2) x
Directional time overcurrent protection ground 67N
1)
(Section 2.3). x
Ground fault detection 64, 67N(s), 50N(s), 51N(s) (Section 2.11) x
Operational Measured Values Display IN INs
Track in disturbance record IN INs