Accelerated lifetime / thermal ageing of power cables

[Casper Hansen]

Hi PF

Is it possible to perform accelerated lifetime test of thermal ageing on power cables?

Let's assume that the cable manufacturer guarantees a service life time of 20 years at max operation temperature 90 [degC]. Is it possible to estimate the expected life time of a cable if I choose to operate my cable above the 90 [degC] let's say 100 [degC]. Maybe the expected life time could be calculated using Arrhenius equation?

Are there any IEC standards that deal with this? That i can use to estimate the life time of a cable

I know that the cable manufacturer do accelerated lifetime voltage test on cables where they test breakdown at 4xU0 (4 times rated voltage) at 4 hours. Does they perform similar tests for thermal degradation of the insulation material?

 

[.Scott]

I would contact the cable manufacturer. They are the ones with the expertise and know all of what goes into an age estimate.

 

[gmax137]

Maybe the expected life time could be calculated using Arrhenius equation?

I think that's the way it is usually done. You need an appropriate value for the activation energy.

 

[CWatters]

Google found...

https://ieeexplore.ieee.org/document/4111066/

But I haven't read it. Bit dated perhaps.

 

[Casper Hansen]

I found this standard IEC 60216 series anyone have been working with it?

I would contact the cable manufacturer. They are the ones with the expertise and know all of what goes into an age estimate.

I have tried that they could not tell.

I think that's the way it is usually done. You need an appropriate value for the activation energy.

If i have two temperature points i can estimate the activation energy?

lets say:
operation temperature: 90 [degC] @ 20 years (631 138 519 s)
Short circuit temperature 250 [degC] @ 5 s
​

Google found...

https://ieeexplore.ieee.org/document/4111066/

But I haven't read it. Bit dated perhaps.

Thanks I'll look into that.

 

[Borek]

If i have two temperature points i can estimate the activation energy?

Technically, yes.

lets say:
operation temperature: 90 [degC] @ 20 years (631 138 519 s)
Short circuit temperature 250 [degC] @ 5 s

Nope, not from this data. One temperature refers to slow degradation, the other to fast thermal decomposition, these are different (chemically) processes, so they have different activation energies (actually thermal decomposition is a mixture of competing, parallel processes, which makes it even more complicated).

If you had data for - say - 50°C and 90°C, that would make sense.

 

[magoo]

What type of cable are you interested in? Medium voltage, high voltage or low voltage?

A number of labs around the world have performed accelerated aging on medium voltage cables (mostly 15 kV to 34.5 kV). The temperature and applied voltage are usually set higher than normal to permit meaningful results in approximately 3 years or so.

You might check NEETRAC, an independent testing facility that is part of Georgia Tech in Atlanta. CTL (Cable Technologies Lab) in New Jersey has done aging tests for different clients. Finally, General Cable has done quite a bit of testing in their lab in Texas.

IREC in Montreal has done some of this testing too, and CESI in Italy has done some.

 

[.Scott]

I would contact the cable manufacturer. They are the ones with the expertise and know all of what goes into an age estimate.

I have tried that they could not tell.​

Then my next question would be: What would the consequences be of premature failure of this power cable? More specifically, is it life-critical, mission-critical, or just a nuisance?​

 

[Babadag]

An increase of the operating temperature by 8 to 10°C reduces the service life by half.
See:
BRUGG CABLES HIGH VOLTAGE XLPE CABLES SYSTEMS Technical User Guide
1.3 Service life
http://nepa-ru.com/brugg_files/02_hv_cable_xlpe/03_web_xlpe_guide_en.pdf

 

[Borek]

An increase of the operating temperature by 8 to 10°C reduces the service life by half.

Which nicely fits the old rule of thumb "raising the temperature by 10°C makes the reaction twice faster". This is based on the observation activation energies of many reactions fall in the same range of tens of kJ.

 

[jsgruszynski]

Hi PF

Is it possible to perform accelerated lifetime test of thermal ageing on power cables?

Let's assume that the cable manufacturer guarantees a service life time of 20 years at max operation temperature 90 [degC]. Is it possible to estimate the expected life time of a cable if I choose to operate my cable above the 90 [degC] let's say 100 [degC]. Maybe the expected life time could be calculated using Arrhenius equation?

Are there any IEC standards that deal with this? That i can use to estimate the life time of a cable

I know that the cable manufacturer do accelerated lifetime voltage test on cables where they test breakdown at 4xU0 (4 times rated voltage) at 4 hours. Does they perform similar tests for thermal degradation of the insulation material?

You can do accelerated lifetime studies on pretty much ANYTHING. NOTHING in this universe is actually static and unchanging - it's only the limitations of human perception that create the illusion of static qualities.

To know if a cable will have problems, contacting the manufacturer probably save a lot of time. Doing your own studies are absolutely possible but to get them right they will take time and it very much helps to know a lot about how the thing was manufactured to do that correctly.