PROTECTING A SWITCHGEAR OR PM ?

[jimbo123]

We were having a bull session on different electrical problems and one subject came up about arc flash. One electrician said as long as his switchgear stays in tip top condition by being PM 'ed on a regular time frame and barring human accidents his equiment will last for ever. He does not have any protection except a microversa relay on the main circuit breaker. According to him he has a shut down every summer and the main is serviced then along with the rest of the equipment.
Some people though he should have some type of arc flash protection like a high speed optical relay on atleast the main of the equipment. His answer to this was the cost was too high for a optical relay and uses watching the work being done inside and keeping it PM'ed every year.
Is this the answer for this type of electric equipment or is speeding the money on a new protection design ? Can we get some opinuns either way on this topic ?

 

[petersonra]

I am inclined to agree that well maintained electrical equipment can last a very long time.

That is not what arc flash concerns are about though.

Brand new equipment can experience an arc flash.

You cannot always prevent an arc flash, although you can do things to reduce the chances of one happening. You can do things to minimize the chances of human beings getting hurt by an arc flash.

 

[charlie b]

Here is the key:

According to him he has a shut down every summer and the main is serviced then along with the rest of the equipment.

Electrical equipment that is turned off can never experience an arc flash event. On the other hand, any item of energized electrical equipment has a possibility of experiencing an arc flash event, and all it may take is someone opening an access door.

 

[mayanees]

PM for Swgr

PM for Swgr

The best thing you can do is keep the equipment PM'd per NETA standards. This provides assurance that the equipment will function per published performance criteria, and thus the arc-flash label is accurate as to what PPE will protect you to a 2nd degree burn level in the event of an arc-flash.
As far as the equipment lasting forever, obviously that's an exaggeration, but if measured in terms of our careers, being ~ 40 years, I suppose that's forever.
So I'm in agreement with your electrician friend - PMing the gear is generally what needs to be done.
I think there's too much emphasis by engineering firms to reduce arc-flash levels to Hazard Risk Category 2. There's an informational note in NFPA 70E, 130.7(A) Note 2 that states - it's the collective experience of the Tech Committee on Elec Safety in the Workplace, that properly maintained <600V equipment is not likely to expose the employee to an electrical hazard.
This reinforces to me that a piece of equipment is okay to be in service, even if it's HRC Dangerous, as long as it's being used as intended, and you're not necessarily making a safer working environment by spending money to reduce an HRC level from 4 to HRC 2.
Of course you can't work on it energized if it's HRC Dangerous, but it's pretty tough to rationalize working on anything energized.
John M

 

[barclayd]

Would love to work at a place where they let you schedule yearly PM.
db

 

[petersonra]

Would love to work at a place where they let you schedule yearly PM.
db

It is usually scheduled for 3am on a Sunday morning during a blizzard.

 

[Jraef]

It is usually scheduled for 3am on a Sunday morning during a blizzard.

Murphy rules...

 

[kingpb]

SEL 751 relay with arc flash detection is maybe $2000, pretty cheap life insurance.

The PM is definitely good, but a great time for an arc flash to occur is the two times a year when the breaker is turned off, and then after PM when it is re-energized.

 

[Jraef]

We were having a bull session on different electrical problems and one subject came up about arc flash. One electrician said as long as his switchgear stays in tip top condition by being PM 'ed on a regular time frame and barring human accidents his equiment will last for ever. He does not have any protection except a microversa relay on the main circuit breaker. According to him he has a shut down every summer and the main is serviced then along with the rest of the equipment.
Some people though he should have some type of arc flash protection like a high speed optical relay on atleast the main of the equipment. His answer to this was the cost was too high for a optical relay and uses watching the work being done inside and keeping it PM'ed every year.
Is this the answer for this type of electric equipment or is speeding the money on a new protection design ? Can we get some opinuns either way on this topic ?

I think that your group is mixing issues as if they are somehow related differently than they are.

Arc Flash hazard mitigation has nothing to do with equipment longevity. There is an indirect relation to PM in that with no PM done, EVER, you are increasing the chances of an Arc Flash event to some degree, but how much is not going to be quantifiable. Arc Flash hazard mitigation has to do with protecting PEOPLE that may be working on the equipment or in the vicinity of the equipment. What an optical relay does in that regard is to pick up the beginnings of an Arc Flash event by seeing the LIGHT produced by it, as opposed to waiting those fractions of a second for the current to increase and be seen by a protection relay (i.e. the MicroVersaTrip relay on your main CB in this case). By detecting earlier, the optical relay can reduce the amount of "Incident Energy" that gets to the Arc Flash by telling the main CB to begin opening a fraction of a second earlier. This will reduce the heat, sound pressure and explosive force in the incedent. It does NOT stop the Arc Flash from happening, it just makes it slightly less dangerous for the people around it.

Regular preventive maintenance can increase the usable lifespan of equipment for sure. It is also necessary in order to avoid SOME of the issues that can lead to an Arc Flash event, such as dust build-up, bad components, loose fittings, corrosion etc. But to say it ELIMINATES the risk of an Arc Flash event is false, and a dangerous presumption. LOTS of other things can cause it, and an Optical relay, or some other form of mitigation, can help to make it safer for the people working there.