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2 Theory of cable fault pre-location
At shown examples the so called test lead is already subtracted. Therefore in the left cursor
(zero cursor) is located at end of test lead (= beginning of cable under test).
2.1 Echometer (Time Domain Reflection)
The IRG sends a low
voltage impulse into the
cable under test.
Cable and or interruption
are reflected positively. A
shortcut results in a
negative reflection.
The positive reflection in this example shows the distance to an interruption of core. The
distance is calculated as follows:
Distance to fault = propagation velocity x time
t×
=
2
v
l
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