Corrosion on 15kv concentric neutral

There are various reasons for corrosion in the neutral path of transmission lines. In shortest I suggest go for lower galvanising series metal anode at various places in the circuit of neutral conductor. It will reduce the existing problem.

Have you considered the use of an impressed current system to overcome the problem?

Hi,

I am a corrosion engineer and willing to profer solution to your corrosion problems; i'm not too sure the configuration of your electric cabling; i suspect your neutral underground cable is experiencing stray current corrosion if they are in spots on the cable; or you need to check the soil resistivity.

If you can give more detail picture of the problem, this might help to give a very definite approach.

Kayode Aremu (Nigeria)

Kayode_aremu@yahoo.com

1. The material & FINISH of the cable ??

2. points of corrisiuon? Jionts , Throu-out length or spots on the length.

I have encountered this problem in domestic-Distribution, with bare-Aluminum cables;

Aluminum has the tendency to be corroded in open-air & bad contacts.

There is on special-Protective-Jelly like to apply for protection.

I know the problem but not the answer.

In the early 1970s the UK used aluminium underground distribution cables where the outer layer was aluminium conductors. These wires were laid in a wave formation along length of the cable so the excess could be gathered for tee jointing without cutting the conductors. On the LV distribution the outer aluminium conductors were the combined Neutral and Earth conductor for use on CNE systems, thereby guaranteeing a a very low earth loop impedance path for the consumer. This was allowed under a special licence as the Installation Regulations prohibited aluminium in any form as part of an earthing system.

The consumers distribution cables which teed of teed off the main distributor however consisted of an aluminium centre phase conductor but the concentric outer layer was copper conductors. In this case there was a copper to aluminium joint at the distributor. A special paste was supposed to be applied to the joint to eliminate electrolytic action, but this appears to have been a limited success.

Both cables had an outer layer of PVC or XLPE covering

Many of the aluminium conductors have now failed as the aluminium is sacrificed at the joint in favour of the copper as would happen with the application of Sacrificial Anodization.

Unfortunately aluminium is a relatively unstable metal considering its position in the Periodic Table and its use must be limited to favourable environmental and compatibility conditions. Non insulated buried aluminium would not be recommended in any case.

I can't understand why your HV cables have a neutral conductor at all as the neutral is only derived at the the LV step down transformer. Is the concentric layer not just an earthed sheath to provide protective device operation in the event of a cable puncture fault.