Meduim Voltage (4160V) Epoxy versus Porcelin Insulators

[natfuelbill]

Any experience with outdoor enclosed Square D HVL load interrupter switches (1985 vintage) epoxy bus bar insulators subject to tracking and flashover? There are sign of tracking. One proposal is to replace the insulators with porcelin...

Thanks,

 

[zog]

Do you have heaters in the switches?

 

[natfuelbill]

yes

 

[zog]

Are they working?

Where are you located? Near the coast?

Normally I would not suspect an issue if they are cleaned every once in a while and the heaters work. Have any photos of the tracking?

 

[natfuelbill]

I don't have monitoring and maintenance/cleaning had not been done prior to seeing tracking.

The installation is inland. No where near the coast.

 

[zog]

Those heater strips fail often and would be the first thing to check, if they fail you will get tracking regardless of materials used. Tracking is caused by surface contamination so moisture from condensation or dirt from lack of cleaning will cause any surface to track.

 

[weressl]

Those heater strips fail often and would be the first thing to check, if they fail you will get tracking regardless of materials used. Tracking is caused by surface contamination so moisture from condensation or dirt from lack of cleaning will cause any surface to track.

...and it will happen with porcellain or epoxy. (The porcellain may take somewhat longer.)

 

[natfuelbill]

Is there a product that would monitor and notify on a failed heater?

 

[kingpb]

...and it will happen with porcellain or epoxy. (The porcellain may take somewhat longer.)

I believe that's what zog said when he stated, "regardless of the material".

Unless of course porcellain is something all together different than porcelain! :grin:

 

[zog]

Is there a product that would monitor and notify on a failed heater?

That is an option on some newer gear but I don't know about any aftermarket products. What some people do is put a light in series with the heater, usually they fail open. But don't forget about cleaning, your best bet is to establish a PM program.

 

[SG-1]

I have seen devices that are basically baby CTs with a relay built in. When the current exceeds a threshhold the relay contact changes.

Ammeters in series with heaters is time tested option if someone is there to read it.

 

[natfuelbill]

I don't have monitoring and maintenance/cleaning had not been done prior to seeing tracking.

The installation is inland. No where near the coast.

 

[John120/240]

Any experience with outdoor enclosed Square D HVL load interrupter switches (1985 vintage) epoxy bus bar ..

Thanks,

I have no experience with these, but what is the expected life span of these

switches ? 26 years is that good or bad ?

 

[zog]

I have no experience with these, but what is the expected life span of these

switches ? 26 years is that good or bad ?

25 years according to IEEE

 

[weressl]

I believe that's what zog said when he stated, "regardless of the material".

From:

Comparative Study on the Properties of Porcelain and Epoxy Resin Insulators, Faculty of Mathematics and Natural Science Bandung Institute of Technology (ITB), Jl. Ganesha No. 10 Bandung 40132 Indonesia​

.....
IV. CONCLUSION
.......

Nevertheless, based on the SEM test results and water droplets, the porcelain insulator specimen surfaces only changed very slightly, or it could be said did not practically change. From the beginning, the water droplet contact angles had been fairly small, around 34 degrees. And then, they only reduced in very small values.​

.........

Based on the SEM test results and water droplet contact angles, the epoxy resin insulator specimen surfaces changed very considerably for the time progressing. On the late withdrawals, the surfaces were seen cracked or damaged. From the beginning, the water droplet contact angles had been very high, around 80 degrees, due to hydrophobic property.
However, on the late withdrawals, the contact angle of water droplets were practically zero, as they were spread out. Thus, the epoxy resin insulators were more degrading as the time progressed rather than the porcelain insulators.​

 

[zog]

Water droplet contact angles??? Sound like transmission line insulators, OP is regarding enclosed equipment and if he has water droplets flying around he has bigger issues than the materials to be used.

If the heaters are working, there will be no condensation and no "water droplets", as I mentioned earlier tracking is from surface contamination and 26 years of dust build up from NEVER being cleaned is likely the cause of the tracking.

 

[weressl]

Water droplet contact angles??? Sound like transmission line insulators, OP is regarding enclosed equipment and if he has water droplets flying around he has bigger issues than the materials to be used.

If the heaters are working, there will be no condensation and no "water droplets", as I mentioned earlier tracking is from surface contamination and 26 years of dust build up from NEVER being cleaned is likely the cause of the tracking.

The issue is material study. Chemical compunds have varying stability. In other words they will break down. When exposed to heat, various chemical attacks and voltage stress the breakdown is acccelerated. My point is that Porcelain is far more stable than Epoxy.

Additional point is that the surface tension of porcellain is much higher than epoxy - as it evidenced by the water droplet experience - so dust accumulation is more difficult on it when compared to epoxy with a lower surface tension.

 

[zog]

Or you can just rub some beaver butter on them

 

[weressl]

Or you can just rub some beaver butter on them

That's a rather nun-substantial response to your 'regardless of material' statement that I challenged.

 

[zog]

That's a rather nun-substantial response to your 'regardless of material' statement that I challenged.

What challange? First you agreed with me, then you posted some part of a study that had little to do with the subject of tracking in enclosed equipment. Sure porcelin might be better in a wet environment, and hard to argue that dirt may not stick to it as easily either, but they also are fragile and when you throw a HVL switch there is a pretty serious shockwave that could shatter a porcelin insulator. Which is why, just maybe, that Square D used the material they did for that application (They do know what they are doing sometimes).

But my point is, and has been throughout this entire thread, that maintaining the heaters working and cleaning the switches every couple of years is a lot more important than the materials used.