Sensitive Earth-Fault And Restricted Earth-Fault - Siemens 7SG11 Manual

2.4

Sensitive Earth-fault and Restricted Earth-fault

This element can be used for either sensitive earth-fault or high-impedance restricted earth-fault protection
schemes. The two applications are not possible simultaneously – the user must select which is required. The
restricted earth-fault scheme is described in section 2.4.1 below.
The element includes a software filter for rejection of second, third and higher harmonics of the power system
frequency. The instantaneous element, set using Protection:SEF/REF Current Setting, provides a starter output. Two
sequential DTL follower timers (Protection:SEF/REF 1st Time Delay and Protection:SEF/REF 2nd Time Delay) plus an
additional timer (Protection:SEF/REF Lowset Delay) are provided; all use the same Protection:SEF/REF Current Setting. The
delayed reset function (section 2.3.3) is applied on each of the two DTL timers.
Each of the three timing elements has an output, mapped by a setting. Each timing element can be inhibited from
a status input, mapped by a setting, see Figure 2.4-1.
In multi-pole directional Argus models the SEF element is non-directional. In single-pole directional SEF models
the directional control setting applies to all the SEF Protection elements.
Ise
*
Dir'n SEF Fwd
SEF Lowset Inhib
SEF Delay 1 Inhib
SEF Delay 2 Inhib
Figure 2.4-1
Table 2-13 Sensitive Earth-fault / Restricted Earth-fault Settings
Sub-menu: Protection
Setting name
Gn SEF Dir Control
Gn SEF/REF Current Setting
Gn SEF/REF 1st Time Delay
Gn SEF/REF 2nd Time Delay
Gn SEF/REF Lowset Delay
Sub-menu: O/P Relay Config.
Setting name
©2013 Siemens Protection Devices Limited
SEF/REF Dir Control *
SEF Current Setting
>
c
Functional Diagram – Sensitive Earth-fault/Restricted Earth-fault Elements
Range (bold = default)
OFF, FWD, REV, TRI
0.005, 0.010...0.050...0.960
0.00, 0.01...5.00...20.00, 20.5
...100, 101 ... 300 s
OFF, 0.00, 0.01...5.00...20.00,
20.5 ...100, 101 ... 300 s
0.00, 0.01...20.00, 20.5 ...100,
101 ... 300 s
Range (bold = default)
7SG11 Argus Technical Reference
In most models the SEF element is non-directional, in which case
*
the directional settings and control inputs can be ignored.
A single pole directional SEF model is available, for which the
diagram shows the logic for elements in the forward direction;
reverse is identical.
SEF/REF Lowset Delay
c
SEF/REF 1st Time Delay
c
SEF/REF 2nd Time Delay
c
Units Notes
Argus 2 Single-pole dir'n. SEF
only.
xIn
sec
see note 1 below
sec
sec
Units Notes – see note 1 below
SEF/REF starter
Event SEF/REF Starter
SEF/REF lowset trip
Event SEF Lowset
SEF/REF stage 1 trip
Event
SEF/REF Delay 1
SEF/REF stage 2 trip
Event
SEF/REF Delay 2
P300008 Protection Functions / SEF/REF
P20007 Page 30 of 71