We have seen this in two 6.6KV cables that feed two circulating water pump. This is not present in the other cables that feed different motors in our power plant. The effect remains in all the cable lenght. Have you seen a similar efect?
Possible causes?
asymetric load?
Any idea?

Regards

The answer you received was correct, candy stripe or barber pole effect.
Can you tell us if the three cables are feeding the same phase or is each cable an individual phase?
One of the cables is carrying more than it's share of current causing it to be warmer. So in theory if the cables are ABC phase, one of the phases is overloaded.
If the cables all feed the same phase then I would suspect a loose connection on the warmer cable.
If one of the cables is considerably longer than the others this would cause possible heating. If the motor were starting to short, breaker contacts, fuses, contactor contacts, over load assembly, auto transformer are all other possible causes.
I see the image was taken a year ago, does the problem still exist?
Dave

The effect is still present, it is a 3-phase (ABC) cable, the phase currents are similar. The problem appears only in this 2 cables that feed CWP 1 & 2, the rest of the motors (18 in total) have similar cables but this problem is not present. It is strange to me that the problems you mentioned are present in 2 cables that feed similar equipments, don't you think it could ve asociated with the load?
The effect is present in all the cable length (it is mounted on trails), if we have a hot spot, I think that the temp dif sould locate in a cable area and become uniform with the cable length. I will cut a piece of similar cable to know about its design.
Sorry for my english and thanks for your help!

Could anyone post some information about candy stripe and barber pole effect?