Setting Notes - Siemens SIPROTEC 4 7SD80 Manual

[lo-esd-erd-anr-20101117, 2, en_US]
Figure 2-12
You will find the logic diagram for the general pickup of the differential protection and the differential protec-
tion tripping in Section
2.2.3.2

Setting Notes

General
The operating mode of the ground differential protection depends on the neutral point treatment in the
protected zone. In grounded systems, address 207 SystemStarpoint must be set to Grounded.
The ground differential protection can be switched ON or OFF at address 1221 87N L: Protect.. This
requires the ground differential protection to be set to Enabled at address 112 87 DIFF.PROTEC.. The
setting Alarm only is only relevant for ground fault detection in resonant-grounded or isolated systems.
If a device is switched off or if the ground differential protection is disabled or blocked in a device, calculation
of measured values becomes impossible. The entire ground differential protection system of both ends is
blocked in this case.
Pickup Value Ground Current Differential Protection
The current sensitivity is set at address 1222 87N L: I-DIFF>. It is determined by the entire current flowing
into a protected zone in case of a fault. This is the total fault current regardless of how it is distributed
between the ends of the protected object.
This pickup value must be set to a value that is higher than the total steady-state quadrature-axis component
of current of the protected object. For cables and long overhead lines, the charging current has to be consid-
ered in particular. It is calculated from the operational capacitance (see Section
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
Ground current differential protection pickup, grounded system
2.2.5 Differential Protection Pickup Logic and Tripping
2.2 Phase Comparison Protection and Ground Differential Protection
Functions
Logic.
2.2.2.2 Setting Notes).
57