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

4.3.

Transient faults

Transient faults cleared within the last
automatic reclosing, can be detected by the
green LED. The green 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, then the
voltage of the healthy phase(s) may result in
no indication or a reset of indication.
This is true for indicators placed before a
fuse as well as after it.
When the criterion of automatic voltage
reset is enabled, the LINETROLL-110Tr is
not activated unless the fault causes a three-
phase trip within 5 seconds after the
occurrence of the fault.
If there is only 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
LineTro110Tµr User Guide

4.5. Multiple faults

Multiple faults can sometimes occur.
Defective network components may burn or
break due to the electro-dynamic force of a
fault current and cause a second fault.
Another cause of multiple faults for network
where the neutral is isolated from earth or
earthed via a resistor, is an increase in the
phase to ground voltage on healthy phases
due to an 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 any 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.
June 2011 Page 8 of 16