shutting down switchgear for winter 1

[krbernier]

We had a pump station rebuilt last fall. The Plant manager decided to shut power to the building off during the winter.
Two circuit breakers in the mcc had problems upon start up last week. One of the breakers started working after the handle was operated many times. The other breaker was replaced.i opened up the bad breaker to find lots of corrosion inside as well as evidence of a nice arc flash.
We are located in New Hampshire so the temp in that building got down to around zero.

This pump station is critical during the dry summer months.My concern is the other breakers in the mcc being corroded also.
My report to the plant manager is going to state that we need to keep this building heated during the winter months and i am suggesting that a tech from the mcc manufacturer come look at the remaining breakers. This is 1600a 480v switchgear and i am concerned that this gear will not be reliable when needed and that the danger of arc flash is increased because of internal corrosion of the breakers.

any thoughts?

this breaker was NEW 6 months ago. the picture is bad but you can see the arc burn and the corrosion

 

[Zogzog]

I would expect to find more issues, hopefully the plant manager will understand why this was a bad idea and not do it again next winter. If he insists you will want to install heaters in the gear to stop the condensation from destroying your equipment.

I suggest you get an NETA testing company in there to give you a independent 3rd party view of the situation. The OEM is just going to see this as a sales oppurtunity.

http://www.netaworld.org

has a list of certified companies in your area. They will be able to do all the testing and provide recommendations.

Breakers that have corrosion or fail testing can be remanufactured at a fraction of the cost of replacement, depending on thier size (Small ones are better to just replace), that is my speciality.

 

[rbulsara]

Looks pretty bad. If the 'corrosion' is due to condensation, heating will help. Space heaters is always a good idea for de-energized electrical equipment.

It is not clear from you post if the 'arc' occurred when you operated the breaker or was already there. So not sure there is something else in play.

What is being pumped? What type of environment? Expanding the review of elements beyond electrical may be necessary.

Rafiq Bulsara

http://www.srengineersct.com

 

[krbernier]

this station pumps water from the merrimack river to our supply ponds at the water treatment plant.
Im guessing the arc occurred when the main breaker was closed this spring.The load bang of the 1600 amp main breaker closing probably caused the operator to not hear the bad breaker arc.

 

[TurbineGen]

We used to put dessicant bags in our sealed switchgear. That usually controlled the moisture within reason. It even worked for units inside an unheated switch house. However with the switch house we needed to replace the dessicant frequently.

Are breakers rated for outside applications possible for your installation? That might fix the problem as well.

------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[krbernier]

i am suggesting building a wall to enclose the area with the gear in it and to keep it heated during the winter. My main concern now is how to inspect the other breakers in the mcc without opening the breakers up and breaking the warranty seal. So far i haven't heard back from the manufacturer and they didn't even want to discuss sending someone out to inspect them. Their response was " Well if its running now its fine." So i said well from the amount of corossion inside this breaker i would be surprised if other breakers weren't affected. I again told them of the importance of this station and sent pictures of the breaker to them. If this station has a major failure in mid-summer the entire city will run out of water.

 

[krbernier]

to clarify this breaker feeds a traveling screen for the intake. the breaker was on but the screen was not put into operation. No load was put through this breaker. The other breaker that had an issue but is now operating properly feeds a transformer for the plc panel. 480to 120v.

 

[rbulsara]

krbernier:

Your thinking may be valid, but asking mfrs is not going to help in this situation. You need to hire a testing company to go through (check and test) all affected equipment and breakers. Perhaps a second opinion of a professional engineer, if this site is so important.

Policy of turning off power may also need to be reviewed. It is electrically helpful to keep the lines, switchboard and transformers energized, so if there is a developing fault, you catch it sooner than later and it is keeps some heat up too. I hope this policy of turning power off is not related to saving energy somehow.



Rafiq Bulsara

http://www.srengineersct.com

 

[jraef]

First off, read this with regards to re-energizing that gear.
faq237-1157

As to testing, a NETA testing agency is a great idea, but I would also investigate whether or not the MCC mfr has their own service group that can re-certify that gear with regards to warranty. I know the majors such as Siemens, Eaton, and Square D do have their own service groups, not sure about A-B (because they don't sell switchgear, which is where the money is). Most of these groups are NETA certified as well. If they won't re-warranty it, then I would go with an independent NETA company for the reason Zogzog gave.

Strip heater in the bottoms of each MCC section is the way it is usually done, no need to build extra walls and heaters etc. All you have to do is keep the temperature above the dew point. Just make sure whatever is feeding power to the strip heaters is getting power too!


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[krbernier]

I honestly don't know what they were thinking. This company pays me good money then doesn't ask me simple questions concerning the electrical equipment. Power will remain on next winter and we are working on a way to heat at least the part of the building that houses the switchgear, plc and soft-starts. The main reason for having the oem look at them is for warranty but since i think the issue was condensation warranty is probably out of the question.

 

[Fraser21]

If you need help on the testing end, let me know. I run a group out of Boston, all we do is acceptance and maintenance testing in the MA, CT & NH area. We follow all NETA standards.

-Brad

 

[rbulsara]

fraser21, blatant/direct marketing is not encouraged on this site.

Rafiq Bulsara

http://www.srengineersct.com

 

[fsck]

I'm sorta curious why the %RH was so high in the winter. My experience in NE winters was it was so %$^&$%& dry your skin cracked.

I agree a few strip heaters could help prevent the issue. In the pipeline industry, we had dozens of Art500 EP boxes & found a small heater and a bottom EP vent was sufficient to keep the boxes dry.

Could you also tape heavy plastic over the panel face to reduce air leakage; then remove in the spring?

 

[TurbineGen]

Cycling your breakers every once in a while can also help. It doesn't do much for the moisture, but it can help keep corrosion from building up to the point of seizing the mechanism.

------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[krbernier]

i think the moisture came from the spring thaw actually. the operators tell me that ice actually forms on the walls in there during the winter.under the floor is a large area open to the river making it almost impossible to heat. i think the problem arose when condensation on the concrete ceiling and walls froze then thawed in the spring running into the gear.

I'm having the gear inspected and cleaned. we are going to wall off the area that houses the mcc, softstarts and plc and keep it heated for next year

 

[Zogzog]

Jraef, none of the OEM's service groups are NETA certified, they do not meet the requirements of a independant 3rd party company.

Another note, being NETA certified company and following NETA standards are not the same thing.

Now to be clear about both of the above statements, I am not saying a non NETA testing company (OEM attached or not) cannot do the job right, but take a look at the requirements of a NETA testing company and you can see some advantages to using one (I am currently not a NETA company for the record, but was a level IV)

 

[oldfieldguy]

Your plant manager MIGHT have learned a valuable lesson. Or not.

In the past I've provided support for several clients who had to deal with moth-balled gear in various voltage ranges.

Some of the equipment was kept "live" with very reduced load, such as a medium voltage lineup kept hot through at 10 MVA transformer to provide power to a 300 kVA transformer feeding some environmentally sensitive equipment.

Others were, as you said, completely dead, but future use was expected.

It was fun explaining to management that even though you didn't USE the capability for years, it still needed considerable care and maintenance to keep it from becoming expensive junk.

As for service groups, I've worked for and with both NETA and non-NETA and OEM groups, and your level of service can be equally good (or poor) with both. I too held NETA level IV certification. I know a bit about the electrical testing and maintenance business.

You need to develop a good relationship with a company that will provide you with the services you need. This is not an easy task, because there are some real "snake-oil" salesmen out there who will take you to the cleaners, and there are a lot of people in the field who "go through the motions" in their work without understanding why they do what they do. It's a tough business to manage, and it makes our job as users more difficult.

old field guy

 

[fsck]

>condensation on the concrete ceiling and walls froze then thawed in the spring running into the gear.

Maybe you also need some drip protection on this panel.