Siemens 7SR242 Duobias - 2.2 Derived Earth fault (50 N,51 N)

7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 21 of 57
2.2 Derived Earth fault (50N,51N)
Figure 2-4 Measured Earth Fault
Voltage Inputs: None
Current Inputs: W1-I
L1
(I
A
), W1-I
L2
(I
B
), W1-I
L3
(I
C
), or W2-I
L1
(I
A
), W2-I
L2
(I
B
), W2-I
L3
(I
C
),
Disable: 50BF, 50, 51, 49, 37
Map Pickup LED: 51N-n/50N-n - Self Reset
Other protection functions may overlap with these functions during testing, it may be useful to disable some
functions to avoid ambiguity. Measured EF & Restricted EF protections can be Enabled/Disabled individually or
as groups in the ‘Function Config’ menu.
These elements can be allocated to W1 or W2 current inputs by relay settings, ensure that current is injected on
the correct input.
Derived EF elements can be separated from Measured EF by secondary injection of current through the phase
input circuit only.