HV AC Cable

You will find one end will be earthed. To earth both ends causes circulating currents. Use the search button at the top right of you screen and you will find lots of threads on this subject.

Well first your using the British spelling but a review of the definition of the word "armor" will help you understand what it does and why its called armor. Now one reason why the armor is not connected to earth involves the concept of ground loops. Another reason involves the mathematics of transmission line theory which is even more complicated than ground loops.

Thank a lot for the reply! However what could be the function of this armor in such case? Also there is stress reliever is installed to reduce the stress on the insulation due to over voltages induced in the armor.

I understood the Lead / Aluminium sheathing is performing the function of fault current carrying, switching voltage dissipation, mechanical protection and also water sealent. Kindly comment!

Earthed armour (or grounded armor, depending on the side of the pond) is there to operate the circuit protective device in the event of a fault.

A typical example of a fault is some silly sod individual putting a spade through the buried cable. Instead of blowing the individual to smithereens, the circuit protective device operates, minimising the damage, and requiring only a fresh set of underwear for the individual concerned for full service to be resumed.

According to codes/regulations the minimum cross section of metal conduit or armour/sheath should be satisfied to effectively carry the fault current to trip the protective device.

Armour of Single core cables is earthed at one end directly and the other end through a surge arrester. The surge arrester helps control the over voltage induced in the armour when there is a through fault etc.

The earthing of armour only at one end is basically due to economic reasons as earthing at both ends will mean reduction in the cable ampacity to accommodate the additional heat due to the circulating currents in the armour.

Trust the above is helpful.

There are two threads of thought on this topic. Generally in the UK, the cable armour is earthed at both ends even if only as a supplementary bond rather than straight to earth. Again this is to protect As PW Slack mentions. However on a military installation a separate earth cable is also run to reduce the risk of loose connections in the cable termination glands. However, the armour itself is there to protect the cable and to provide added strength when the cable is laid in ducting, trenching or externally to provide an added protection to prevent personnel from damaging the cable in day to day use. It will not stop the big yellow cable finder (JCB) from damaging the cable should it do so, but if earthed, may trip the protection circuit or prevent the cores from being struck.