13.2 kV switch maintenance

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Volta

Senior Member
Location
Columbus, Ohio
Assuming the service disconnects (two) have not been operated in decades, once the source has been disconnected by the POCO, what should be considered for minimal maintainence to assure that the disconnect can be reliably operated in the future? For better than minimum maintenance?

Arc-flash calcs, PPE, and even remote switching can be in the safety list, but even with remote switching apparatus and personell safety assured we don't want damage to the exterior switchgear. :)

The info provided by the POCO in December is:
1. voltage --- 13.2Y/7.62KV
2. available fault current at that point in the system / at this point in time, --- 3285 Amps (LLL), 2320 Amps (LG)
3. wire size, --- #2 ACSR conductors
4. fuse types at pole, --- Kearney T
5. fuse sizes. - - - 100 Amps T

Each switch feeds a pad mounted transformer, perhaps 10 and 25 MVA or so.

Very possibly will contract someone specializing in this, but need to know what methods to expect anyhow.
 
zog

zog

Senior Member
Location
Charlotte, NC
The key for these switches is mechanical operation, the linkages and operating mech needs to be inspected and lubricated properly. As far as the electrical tests the following will be done:

Megger test
Hi-pot test (All cables removed)
Bolted connections all checked with a microhmeter with an output of at least 10A
Fuse resistances are verified per manufactures tollerances

Those are the basics, check your email for a present.
 
T

TxEngr

Senior Member
Location
North Florida
If the switches haven't been operated in decades, then the grease is most likely solidified and will need to be replaced. That will take extra time so allow for it. After testing and cleaning, make sure everything is fully lubricated. I would apply conductive grease to the stabs and blades as well. Finally, consider adding some well placed infrared viewing windows to allow performing infrared inspections on the equipment while it's in operation. A great preventive maintenance tool.

TxEngr
 
zog

zog

Senior Member
Location
Charlotte, NC
TxEngr said:
If the switches haven't been operated in decades, then the grease is most likely solidified and will need to be replaced. That will take extra time so allow for it. After testing and cleaning, make sure everything is fully lubricated. I would apply conductive grease to the stabs and blades as well. Finally, consider adding some well placed infrared viewing windows to allow performing infrared inspections on the equipment while it's in operation. A great preventive maintenance tool.

TxEngr
Click to expand...

IR is not very effective for 15kV equipment, PD monitoring will find issues much sooner and does not require any modifications the the gear.
 
V

Volta

Senior Member
Location
Columbus, Ohio
TxEngr said:
If the switches haven't been operated in decades, then the grease is most likely solidified and will need to be replaced. That will take extra time so allow for it. After testing and cleaning, make sure everything is fully lubricated. I would apply conductive grease to the stabs and blades as well. Finally, consider adding some well placed infrared viewing windows to allow performing infrared inspections on the equipment while it's in operation. A great preventive maintenance tool.

TxEngr
Click to expand...

Are IR viewing windows a special material? There are small viewing ports in the doors, but pretty dirty these days. Don't know what material it is.

zog said:
IR is not very effective for 15kV equipment, PD monitoring will find issues much sooner and does not require any modifications the the gear.
Click to expand...

What is PD?

There should also be anti-condensation heaters there. Short of testing them in a freezer or in January, is there likely to be an way to test them?
 
T

TxEngr

Senior Member
Location
North Florida
The IR windows are a special material to allow the IR light to be transmitted. A standard window won't work. I'll agree somewhat with Zog about the PD being a better test, but InfraRed is still a good PM tool, even on 5KV and above. The windows cost about $250 -300 so they aren't cheap. But in today's world where you don't open equipment when energized, they are a great tool.

PD is partial discharge testing and is a tool for looking for the high voltage corona and tracking on 5KV and above systems that might not be picked up by other methods. Typically this is farmed out to a contractor since the tools are fairly expensive. Zog, you can probably elaborate on this a bit more.
 
zog

zog

Senior Member
Location
Charlotte, NC
TxEngr said:
The IR windows are a special material to allow the IR light to be transmitted. A standard window won't work. I'll agree somewhat with Zog about the PD being a better test, but InfraRed is still a good PM tool, even on 5KV and above. The windows cost about $250 -300 so they aren't cheap. But in today's world where you don't open equipment when energized, they are a great tool.

PD is partial discharge testing and is a tool for looking for the high voltage corona and tracking on 5KV and above systems that might not be picked up by other methods. Typically this is farmed out to a contractor since the tools are fairly expensive. Zog, you can probably elaborate on this a bit more.
Click to expand...

Yes, PD testing has come a long way and can now be done without opening any doors (So no need for expensive windows) through capacitive sensors, the sensors in a case like this switch pick up TEV, transient earth voltages from the PD (Partial doscharge) activity that is a precoursor to insulation breakdown. Where IR requires breakerdown to already be present to the point where heat is being produced, PD detects the insulation breakedown before the heating occurs. Perhaps an entire new thread on the new PD sensing tecnology is in order, too much to post here.
 
zog

zog

Senior Member
Location
Charlotte, NC
Volta said:
Are IR viewing windows a special material? There are small viewing ports in the doors, but pretty dirty these days. Don't know what material it is.
Click to expand...
Those windows you have are not good for IR scanning because they will not pass the IR waves, the IR wondows are a special material that not only allow the IR waves to pass but are also a prisim to allow for a wide wiewing area of the key points.


Volta said:
What is PD?
Click to expand...

Partila discharge, which is a precoursor to corona, tracking, and insulation breakdown. PD can be sensed several different ways. Maybe I need a while thread on PD sensing that is available today.

Volta said:
There should also be anti-condensation heaters there. Short of testing them in a freezer or in January, is there likely to be an way to test them?
Click to expand...
Yes, turn them on and see if they get hot. These heaters failing in outdoor equipment is the most common cause of MV switch failures, see it every day.
 
V

Volta

Senior Member
Location
Columbus, Ohio
zog said:
Those windows you have are not good for IR scanning because they will not pass the IR waves, the IR wondows are a special material that not only allow the IR waves to pass but are also a prisim to allow for a wide wiewing area of the key points.
Click to expand...
I do like the prism idea. It is hard to see much in there. Having IR ability isn't a bad idea, even if inferior to the PD, but I doubt either will end up happening, honestly.
Partila discharge, which is a precoursor to corona, tracking, and insulation breakdown. PD can be sensed several different ways. Maybe I need a while thread on PD sensing that is available today.
Click to expand...
I'd like to read a general overview of the components and info. that can be gleened.
Yes, turn them on and see if they get hot. These heaters failing in outdoor equipment is the most common cause of MV switch failures, see it every day.
Click to expand...
Haven't seen them, but figured there would simply be a temperature sensor that would be difficult to override. Think the units are likely to have a test mode?
 
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