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Cable route and joint position tracing
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What is the route of my underground cable? Where are the joints located? As part of its diagnostics services, KEMA performs route tracing by means of the magnetic method and joint position tracing by means of the “echo-method” (low voltage impulse reflection method). Determination of joint position is also performed as part of VLF partial discharge cable diagnostics.
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Cable length and joint position determination
Cable length and joint position may be determined by using the "echo-method”. A low voltage impulse signal is injected into the cable conductor and its reflection is measured over time. Joints produce weak reflections, whereas the cable end produces a strong reflection. By making use of the pulse propagation velocity of the specific underground cables and the composition of the cable circuit, the cable length and joint positions may be determined with an accuracy better than 0.5% up to 1,500 m.
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Cable route tracing
A high frequency ac current is circulated in the cable conductor
and the magnetic field around the cable, induced by this ac
current, can be measured at the surface and used to locate the
position of the underground cable. After tracing the cable route,
the route may be “wheeled” to measure the actual length and to
pinpoint the position of the joints relative to the surface.
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Experience
Cable length and joint position determination is a regular part
of KEMA's partial discharge diagnostics and is performed on a
routine basis.
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KEMA services
KEMA offers cable-consulting services for CBM on power cables including the following:- Diagnostic measurements such as partial discharge diagnostics on all types of MV cable circuits
- Water tree diagnostics on MV polymeric circuits
- Partial discharge diagnostics on MV and HV cable accessories
- Outer sheath testing and voltage withstand testing of the cable insulation
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