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User Manual LineTroll R400D
The nominal trip setting values listed above are calculated values based on the magnetic field
in
T (micro Tesla) below a horizontal line configuration with phase spacing of 1,5m and
where the indicators are mounted 3 meters below the middle conductor.
In other configurations, such as triangular and vertical etc, the distance between each phase
and the position of the indicator will differ and the magnetic field sensed by the fault indicator
for the same PtG value will in some instances be changed. In networks with relatively high
earth-fault currents (>10A) this effect will be less significant.
NorTroll offers calculations to be executed on all types of line configurations upon request.
Short circuit faults
The indicator requires that two conditions are satisfied in order to detect a short circuit fault:
1.
The relative increase dB
is greater than a certain level (50%, 100% or 200%).
2.
The absolute dB
T
is greater than a pre-set value; 50, 100, 200, 500 or 1000A ref
to an indicator located 3 meters below a horizontal line configuration with 1,5m
conductor spacing. More narrow spacing will increase these values, making the
indicator more sensitive for short circuit faults.
The indicator will indicate short circuit faults the same way as for earth faults and the same
messages (transient or permanent fault) will be reported back to the central unit.
Recommended distances
The fault current which is necessary to
generate a sufficient increase in magnetic
field depends on the;
i)
Indicators distance (d) from the
conductor, -measured from the
lowest conductor.
ii)
Line configuration
Typical distance is 3-4 meters below the
conductors
d
Figure. 8 Distance from conductors
