Transient Fault; Fused Lines; Multiple Faults - Nortroll LineTroll 110Em User Manual

4.3.

Transient fault

Transient fault cleared within the last
automatic reclosing, will be detected by the
green LED. The LED will flash for 24
hours as extended transient indication.
Line
<5s
I
Green
Indication
LED
Extended transient fault
indication
If a new fault occurs within timeout (24h),
the indicator will reset the green LED and
indicate for the new fault.

4.4. Fused lines

One operation criterion (assuming
automatic voltage reset is enabled) is that,
after a fault, three-phase disconnection of
the line has to be carried out. If, instead of
a three-phase trip, a fuse operates in one or
two phases, the voltage of the healthy
phase(s) may cause no indication or reset
of indication.
This is true for indicators placed before the
fuse as well as after it.
When the criterion of automatic voltage
reset is enabled, LINETROLL-110Er is
not activated unless the fault causes a
three-phase trip in the feeding within 5
seconds after the occurrence of the fault.
If there is one disconnection within 5 sec,
followed by an automatic reclosing causing
a fuse-operation, the indication starts, but
will reset after 30 sec.
If the automatic reset is switched off, the
indicator will continue flashing until it is
reset manually or after the automatic timer
period has elapsed.
24h
LINETROLL 110E /110Eµr User Guide February 2010

4.5. Multiple faults

Multiple faults sometimes occur. Defective
network components may burn or break
due to the electro-dynamic force of the
fault current and cause a second fault.
Another cause of multiple faults is the
increase in the phase to ground voltage on
the healthy phases due to the initial earth
fault.
The phase to ground voltage may reach up
to 1.7 times the nominal voltage,
depending on the total impedance of the
earth loop. If there are weak points in the
line, they may not withstand such a large
voltage increase. This type of fault may be
difficult to find as they often are non-
permanent and only appear in situations
like the ones mentioned here.
Note: In this situation the indicators
may show non-consequent indication.
Page 8 of 16