5.5 Low insulation and Water ingress
These faults are due to contamination of the insulation medium by moisture ingress through a cable.
This gives a reflection like short conductor fault pulse, where the moisture starts, followed by a small
open-type fault pulse where the moisture ends. In some cases, where the moisture increases gradually
with distance, these fault pulses broaden out into a gentle shell or dip in the horizontal trace, Fig 5.
Caused the amplitude of next event curve in display right-side of this water ingress point become
lower. Water in jelly-filled cable may produce only very small fault pulses due to the restricted volume
of water. Besides, a transition from low impedance to high impedance cable also cause same
reflection.
Fig. 5
5.6 Low /Water at Cable joint
This fault is similar to item 5.5 but happen at Cable joint which contaminated by wet environment.
Fault trace is as Fig. 6 which after splice be followed by small sine or square that decreasing gradually.
Fig. 6
5.7 Bridge tap
Bridge taps occur when another pair of conductors is connected to a pair in the main cable to form a branch or
party line. At the branch or bridge junction, a short conductor downward reflection will occur due to the
characteristic impedance haft sharing at that point and follow by upward reflection caused by end of the tap as
shown in Fig 7.
Fig. 7
