Siemens SIPROTEC 7SD610 User Manual

Functions
2.5 Restricted Earth Fault Protection (optional)
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
87
Figure 2-32 Tripping characteristic of the restricted earth fault protection in dependence on the phase dis-
placement between 3I
0
” and 3I
0
' at 3I
0
” = 3I
0
' (180
o
= external fault)
It is also possible to increase the tripping value proportional to the current sum. In this case the pickup value is
stabilized with the arithmetic sum of all currents, i.e. with „IrestREF=“ Σ | I |=|I
L1
|+|I
L2
|+|I
L3
|+|I
4
|.
The slope of the characteristic curve can be adjusted.
Pickup
Normally, a differential protection does not need a „pickup“, since the fault detection and the trip condition are
identical. But the earth fault differential protection, like all protection functions, has a pickup function which is
required for tripping and serves as the starting point for a number of further activities.
As soon as the fundamental component of the differential current reaches approximately 85 % of the pickup
value, pickup is recognized. In this aspect, the differential current is represented by the sum of all in-flowing
currents.
Figure 2-33 Increasing the pickup value

Siemens SIPROTEC 7SD610 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SD610
Category	Relays
Language	English