HV Cable Real Time Conductor Temp Measurement 1

[Marmite]

Does anyone have any experience with the use of fibre optics embedded with the screens of HV and EHV polymeric cables for real time measurement of conductor temperature and detection of water ingress? I'm thinking of trialling the technology in the Company I work for and would be interested to hear all comments good or bad.

Regards
Marmite

 

[ausphil]

marmite,

we have been specifying and purchasing 132kV cable with fibre in between the screen wires for a number of years now for temperature measurement, so that we have the options to monitor in the future if requried. however most of these installed cables do not have the measurement box connected to them - probably because of the expense of these monitoring boxes.

our only set of monitored cables are run in a tunnel, so all we are really measuring is the ambient in the tunnel system, so we are not really getting any great information about different soil types and alying arrangements from all the data that comes out.

the system seems to work well overall, however I question the information we are getting back in our situation.

the one problem that we have had is terminating the fibres in joints. we have had to re-excavate a number of joints due to the stainless steel tube that protects the fibres has shorted out the cable sheath, which was found during testing. another problem is that we have had water get into the joint (not the hv section) through the fibre termination box, and cause problems during the sheath tests as well. the cause seems to be a little complacency from the jointing staff, as to how to terminate the fibres in a water-tight fashion - after all, they have just completed a complicated high voltage insulated joint, and this is just a tiny tube with some fibres in it.

this is just one part of the experience that can be problematic if care is not taken. we spent hundreds of thousands of dollars rectifying joints on cables where we are not even utilising the fibre for monitoring purposes. an expense that is very hard to justify if you are not using the fibre.

there seems to be divided opinion around the world as to whether you should put the fibre in the cable screen area or attach it to the outside of the cable. my personal preference from the experience we've had would be to attach it to the outside of the cable, that way the fibre never compromises the integrity if the joint itself - obviously the calculation model will be different to determine the conductor temperature for each method.

ausphil

 

[Marmite]

Thanks for the response, Ausphil.
Regards
Marmite