Is there a way to test post insulators? Is there an expected life

[bdn2004]

We have some post insulators on site that we are considering to re-using. Others that were installed at the same time seem to work with no problems. But these things are likely 20+ years old. Is there a way to test them? Or is there a longevity chart on stuff like this? Or is this in general, just a bad idea to re-use something this old?

Attached is a picture of one of them.

 

[stevenal]

Replace em. The two parts are cemented together, and the cement can fail over time. After some close calls where they failed on switches where the cable end came loose and fell, we began changing these out for solid post insulators.

 

[rterickson]

Those insulators look to be closer to 50 years old than 20.

I think you got your money's worth.

 

[jghrist]

I agree with Stevenal. These are not post insulators, they are cap and pin insulators. They have a reputation of failing after being in-service for a long time because of cement growth.

 

[cuky2000]

The test of insulator may cost more than the unit. If there are not visible degradation of the insulator there is a good possibility that this unit will work with similar performance as the existing insulators in the station.

 

[oldfieldguy]

The utility company I used to work for (a big one in the southern US) was undergoing a concerted effort to get rid of the cap and pin insulators, replacing them with posts.

Some of ours were quite old. Mechanical integrity was beginning to deteriorate in too many of them. the cement between the various cap elements and the cap to pin junction starts failing. When this happens you get some interesting electrical effects in the gaps.

We never tested them, just replaced them wholesale.

old field guy

 

[cuky2000]

1) Find Basic info such as : How many years in service, voltage, short circuit level, how critical is this facility, redundancy, etc.
2)How many pin insulators are in the substation?
3) History of total failure and how many associated with insulators?
4) There is a plan for modernize this facility any time soon? Any estimate capital available at this time?
5) if the target insulator is replaced with new post insulator that will improve the overall reliability of this substation?

Judging by the picture provided, I do not see how changing a single insulator by a new post type or pin type insulator will make any significant difference in the overall reliability of the substation.

 

[jghrist]

Judging by the picture provided, I do not see how changing a single insulator by a new post type or pin type insulator will make any significant difference in the overall reliability of the substation.

The original question was not to replace the cap & pin insulators with posts, but to re-use salvaged insulators.

 

[stevenal]

Maybe I wasn't clear above; this is a safety issue. None of Cuky's points 1 through 5 make the least bit of difference where safety is concerned.

 

[Massoud1]

No need to guess anything, just take a few samples and send them to a test lab in order to perform routine tests according to IEC standard.

 

[cuky2000]

Hi Stevenal,
I am disagree with you regarding that questions above are not safety related.
For example, failure, redundancy, level of SC vs. mechanical withstand of insulator, history of failure and consequences among others are indirectly related with safety to me.

My main concern is changing a few insulators leving other old insulators in operation may not change the overall facility reliability or safety related issues.

Assuming that all insulators are replaced by post type insulators, how this will resolve all safety related issues in the substation?

 

[stevenal]

Nothing indirect about it, history of failure (poor history with this insulator) and the consequences (arcing faults) are directly related to safety. Never claimed it would resolve all safety issues, I'm not even aware of what all those issues may be. I do know of one, however.

Who said anything about guessing? I'm not familiar with IEC testing, but if the tests are electrical in nature I doubt they would catch every pending mechanical failure. But even if they could be proved mechanically sound doesn't mean I would put a device with a such a poor record back in service.

 

[bdn2004]

I happened onto some more surplus parts. They look newer but this is the same pin cap design.
The second picture in the attached .pdf is of the cement that holds the two bells together, that is apparently per this thread and vendor's info - the potential point of failure. By inspection it doesn't look like this would give way and these insulators have a good track record at this plant.

But the advice here will be heeded. There is no sense in risking it to save relatively speaking little $. Thanks for the answers.