Overhead Distribution Recloser Maintenance...

[potteryshard]

Does anyone know of economic studies performed regarding the desireability of implementing a scheduled maintenance/replacement program for in-line overhead (mostly oil-filled, oil-interrupting) distribution reclosers?

Because a maintenance program will require replacement of the field unit assembly and contract shop refurbishment, and because the manufacturer's recommended overhaul intervals are unreasonably frequent, any maintenance program will likely be costly.

On the other hand, failure of the reclosers usually amounts to failure to perform rather than catastrophic events. A failure to perform would usually seem to result in upstream protective devices (substation feeder breaker) operation resulting in a larger-than-necessary outage. Such events would however, seem to be reasonably uncommon and relatively easy to quickly bypass and restore.

These factors leave me with a gut feeling that it may be more economical to operate the reclosers until failure, and that doing so would not significantly affect system reliability. My gut is notoriously unreliable, however.

Does anyone have realistic information regarding recloser failure rates, refurbishment program benefits, or cost/benefit analyses?

Thanks!

 

[ichrist]

If you plan to avoid maintenance on overhead reclosers, there are a couple items you need to look at to 'cya'. I presume you (like myself) are working for a utility and your reclosers protect lines in public areas.

1. Can the substation breaker clear faults right to the end of the line? If a line is sitting on a car and the substation doesn't clear it, lawyers will make a lot of money off of you.
2. Can it clear faults within an acceptable time frame?
3. Do your SAIDI & SAIFI stats matter to you?
4. If you can meet criteria 1 & 2 and don't care about 3, why not remove the recloser all together? It might work if your utility also uses fuses at strategic locations which then means other customers are only subjected to momentary outages during reclose cycles. I'm also assuming your substation breaker also goes through reclose cycles.
4. Don't forget that the labour cost of replacing them at failure is a lot higher than planned maintenance. That includes overtime, driving from home, gathering materials and likely missing part of work the next day because you're on 'rest' time.

Where I work we've started replacing oil reclosers with vacuum on the justification that the future maintenance costs saved outweigh the initial cost of the more expensive technology. Vacuum units are typically good for 2500 operations. Plus we get more accurate tripping as well as event data etc. We can also reduce inventory because one vacuum can be programmed and therefore replace several different ocr stock codes.

 

[ichrist]

I thought of one more thing:

Presumably your field staff will need to operate these occasionally. If you ask a field guy to operate a device that is 5 or 6 times past it's due maintenance time, they might refuse to operate it live (ie open the substation breaker first). Personally I'd consider it a legitimate concern.

Regards,
Ian