Cable fault

Basic conditions, causes, and types

Cable routes are influenced by a variety of ambient parameters. A cable route can consist of many cable sections, often with different types of cable construction. Depending on the voltage level, the required load capacity, and available accessory and installation technology, cables with plastic insulation or mass-impregnated paper insulation are used.

Types of cable insulation

Cables with

mass-impregnated paper insulation

Cables with plastic insulation

Causes of cable faults

Cable damage can be due to various causes. The most common sources of faults include end of service life and external influences as well as improper assembly. When these types of cable faults occur, the defective spot needs to be detected as quickly as possible and the fault rectified in order to minimise the duration of the failure.

It is helpful if the cable fault location equipment can be used for all voltage levels right across the network. In practice, cable faults must be located on all voltage levels – from low voltage through medium voltage to high voltage.

Common types of cable fault

Short-circuit

Damaged insulation leads to a low-resistance connection of two or more conductors at the fault location.

Cable breaks

Mechanical damage and ground movements can lead to breakage of individual or multiple conductors.

Cable sheath faults

Damage to the outer cable sheath does not always lead directly to faults. However, it can cause long-term cable faults, among other things, as a result of moisture penetration and insulation damage.

Short-circuit to earth

Earth faults or short-circuits to earth are low-resistive connections to the earth potential. The double earth fault is another type of fault; this fault shows two earth faults on different phases with separated bases.

Intermittent faults

Frequently, faults do not occur constantly, but rather occasionally depending on the load on the cable. One reason for this can be drying out of oil-isolated cables with a low load. Another is partial discharge through ageing or electrical trees in cables.

Further information on cable fault location

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Solutionfolder: long submarine and land cables Solutionfolder: long submarine and land cables

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