Derived Earth Fault (50N,51N) - Siemens 7SR242 Duobias Technical Manual

2.2

Derived Earth fault (50N,51N)

Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
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.
©2015 Siemens Protection Devices Limited
Chapter 6) 7SR242 Duobias Commissioning & Maintenance Guide
Figure 2-4 Measured Earth Fault
None
W1-I (I ), W1-I (I ), W1-I
L1 A L2 B
50BF, 50, 51, 49, 37
51N-n/50N-n - Self Reset
(I ), or W2-I (I ), W2-I
L3 C L1 A L2
(I ), W2-I (I ),
B L3 C
Chapter 6 Page 24 of 62