# Half a year full in my new job



## Yellow World (Oct 11, 2017)

Don't know if it's the right place to post or if anybody's interested anyway. Usually I'm not writing a lot but I'm a frequent reader here. If my post is in the wrong spot, feel free to move it to a different section. Now here's my story.

Half a year ago I made my dream come true, passed my electrician licence exam and started my first REAL job in the trade as a plant electrician in a small 130-employees company. Work contains anything from changing light bulbs and pulling wires over controls, motors, VFD, PLC to HMI. I even have the chance to design and assemble new control panels or entire controls for our machines. 

Since the last two guys who worked my job before had a rather lousy working attitude (that's at least what everybody here keeps telling me), there's still lots of stuff around for me to fix and rebuild. The company I work for gives me almost no restrictions on how to build and what parts to use, they're just happy if something is getting done. I'm the only full-time electrician here, the guy who's in charge of our department is also electrician and if anything is unclear I can ask him for advice. Our machines are all quite small with motors of up to 5HP, so everything is more or less handy and easy to work with. 

So far I feel like I've won the lottery. First time that I feel I wanna stick with a trade until retirement. Work is interesting here and throws new challenges on me every day. So far, there's still a lot to learn. But I'll do my best and feel I'm improving with every day and every project that's finished. Looking back, the year 2018 was one of or probably THE best year in my life. Now looking forward to what the future brings.


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## Switched (Dec 23, 2012)

Welcome! Glad you're enjoying the ride!


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## stuiec (Sep 25, 2010)

Congratulations, sounds like you found a home. Now make it yours!


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## MikeFL (Apr 16, 2016)

That's a great story.
As we'd say in the US, Bad Ass!
You have a great attitude. +1

Enjoy!


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## jelhill (Nov 11, 2018)

Welcome aboard... and your post was fine. You will learn a lot of good stuff on this forum... a lot tricks of the trade that guys have learned in the school of hard knocks. Sounds like you have a good place to work.


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## just the cowboy (Sep 4, 2013)

Welcome


If you got question just ask. If you do ask give us as much info as you can it helps. Please come back and let us know the outcome of any questions.


As for work think Documentation documentation documentation. It will help you and everyone out in your plant after you.
Good luck
Cowboy


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## micromind (Aug 11, 2007)

Yellow World said:


> Don't know if it's the right place to post or if anybody's interested anyway. Usually I'm not writing a lot but I'm a frequent reader here. If my post is in the wrong spot, feel free to move it to a different section. Now here's my story.
> 
> Half a year ago I made my dream come true, passed my electrician licence exam and started my first REAL job in the trade as a plant electrician in a small 130-employees company. Work contains anything from changing light bulbs and pulling wires over controls, motors, VFD, PLC to HMI. I even have the chance to design and assemble new control panels or entire controls for our machines.
> 
> ...


I'm in sort of the same boat. 

I am the design engineer (no credentials, just common sense and experience.....), panel builder, and installer for the control system. There will be about 400 PLC in/outs when I get done, maybe more......the plant isn't done yet......lol. 

As an example, today I thought up, designed and installed controls for a 4160 switchgear. It has 2 breakers, one for a 1250 HP motor, the other for a 1500 KVA transformer. 

The control power comes from a 4160 - 120 100 VA transformer mounted in the gear and fed from the utility side. The breakers have 120 AC close coils and 125 DC trip coils. The DC is derived from simple bridge rectifiers mounted in the gear. 

There are no drawings of any kind. 

Since the loss of DC power would render the trip coils inoperative and as such the breakers are now switches, incapable of tripping. 

I thought it would be a good idea to alert the plant operator of such a problem so I installed 2 - 110DC relays in the gear and sent their contacts to the PLC. 

This way, if DC power is lost, they can take appropriate action rather than have some sort of explosion and/or meltdown because the breakers cannot trip. 

No drawings, no specs, not even a suggestion, just my idea based on my knowledge and experience. 

I really love my job and the freedom I have in identifying and solving problems before they become problems!


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## paulengr (Oct 8, 2017)

micromind said:


> I'm in sort of the same boat.
> 
> I am the design engineer (no credentials, just common sense and experience.....), panel builder, and installer for the control system. There will be about 400 PLC in/outs when I get done, maybe more......the plant isn't done yet......lol.
> 
> ...


That's pretty typical because the 4160 gear is designed for substations. In the event of even during normal operation, no power outage, etc., if you have a fault as in dead short somewhere, the incoming transformer won't be able to keep up and voltage even control power both AC and DC rectified will drop down to almost nothing. If nothing else think what the voltage is across a dead short...obviously 0 V by definition. And at the switchgear with big power buses where everything is very low impedance, I think you get the picture of what happens. In this situation your protective relays either die too or can't trip anything even if they could! This is not good idea all the way around and very dangerous never mind code violations.

Another hazard is that during startup from power loss if you have a dead short, particularly if the short tripped something upstream you need the breakers to trip instantaneously but they have no power yet and/or the relays are just powering up so basically you have no protection at all. So you really need an external DC source.

This is specifically why the breakers have 125 VDC trip coils and the protective relays generally run on it too. So you need a 125 VDC power supply that does not rely on outside power. And yes, alarming is critical on that system and needs to be treated like a fire alarm. And ideally you monitor the trip coils for failures too but that's more of an advanced feature. Option 1 is to use a string of batteries. Tried and true is open cell lead acid batteries substation grade. This takes up a ton of space nd there's a little monthly maintenance but basically you can do some simple checks, replace jars as needed, nd generally make it last forever. Small ones take up about 3 feet by 2 feet of floor space. Big power plant sets take up a whole room. There are also some small NiCd and NiMH knes that I've heard rave reviews on but the first few of these have been horror stories down the road.

Option 2 is a CTD or capacitive trip device. These are the most economical when you have just a few breakers where the big battery pack doesn't make sense. It's a rectifier with a huge capacitor on it and usually a UV (undervoltage) trip coil. The capacitor stores enough energy for 1 to 2 trips. When voltage (energy) gets too low it sends one last trip out. Otherwise you'd have the problem of no protection when powering up possibly into a fault. It's a hassle when all breakers open about 10 minutes into a power loss and closing them all back in but the consequences are far worse. Coal mines are required to have his by regulation so it's not something general industry uses but common for them. Usually they have just 1 or 2 really big machines anyways and batteries releasing hydrogen fumes which is a fire hazard around a bunch of rocks and dust that can ignite or explode is generally a really bad idea anyways, never mind potential maintenance headaches.

Finally just alarming is also a bad idea. Do you know how many plants IGNORE major alarms like DC bus undervoltage, ground faults on resistance grounds, fire alarms, etc.? All of them. Factory Mutual and most other insurance carriers require TRIP on ground fault and undervoltage for a reason on new installs. Factory Mutual publishes their Code. Make sure you comply with transformer spacing, protective relaying, etc. ahead of time of be prepared for a lot of expensive gotchas later when they first try to get insurance for business loss.


Sent from my SM-T350 using Tapatalk


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## Yellow World (Oct 11, 2017)

Thanks everyone for your replies! I really enjoy this job a lot. Feels like the company appreciates my work as well. Every company has advantages and disadvantages, but so far I think the advantages outweigh the disadvantages.

We have a 11,400V high voltage line coming in as power supply, it goes via some switchgear to a 600kVA transformer, which transforms it down to three phase 220V. But everything on the primary side of the transformer is maintained by an external contractor, so I'll probably be unable to share any kind of experience about this topic in the future.

But there's still lots of other stuff to learn and troubleshoot. Had some issues with VFD lately. But I'm gonna post that in a separate topic later.


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## MechanicalDVR (Dec 29, 2007)

Welcome aboard @Yellow World!

Enjoy your ride here and best of luck in the new endeavor!


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## MikeFL (Apr 16, 2016)

Yellow World said:


> Thanks everyone for your replies! I really enjoy this job a lot. Feels like the company appreciates my work as well. Every company has advantages and disadvantages, but so far I think the advantages outweigh the disadvantages.
> 
> We have a 11,400V high voltage line coming in as power supply, it goes via some switchgear to a 600kVA transformer, which transforms it down to three phase 220V. But everything on the primary side of the transformer is maintained by an external contractor, so I'll probably be unable to share any kind of experience about this topic in the future.
> 
> But there's still lots of other stuff to learn and troubleshoot. Had some issues with VFD lately. But I'm gonna post that in a separate topic later.



Where did you learn such good English? Are you native Taiwan?


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## micromind (Aug 11, 2007)

paulengr said:


> That's pretty typical because the 4160 gear is designed for substations. In the event of even during normal operation, no power outage, etc., if you have a fault as in dead short somewhere, the incoming transformer won't be able to keep up and voltage even control power both AC and DC rectified will drop down to almost nothing. If nothing else think what the voltage is across a dead short...obviously 0 V by definition. And at the switchgear with big power buses where everything is very low impedance, I think you get the picture of what happens. In this situation your protective relays either die too or can't trip anything even if they could! This is not good idea all the way around and very dangerous never mind code violations.
> 
> Another hazard is that during startup from power loss if you have a dead short, particularly if the short tripped something upstream you need the breakers to trip instantaneously but they have no power yet and/or the relays are just powering up so basically you have no protection at all. So you really need an external DC source.
> 
> ...


The majority of MV switchgear I work with does indeed have batteries, sometimes 2 racks with blocking diodes so a fault on one rack cannot discharge the other. 

A lot have cap-trips as well, usually these are arranged so a loss of DC will cause the breaker to trip right away. 

This plant is fairly small, the POCO transformer is 3MVA, 12.5KV - 4160. 

I'm pretty sure that a bolted fault anywhere in the 4160 gear will blow the POCO cutouts but an arcing fault will very likely not. 

Trouble is, a bolted fault is rare once the system has been in operation. They're almost always arcing faults. 

I tried to get cap-trips but they would not go for it........

My next thing will be to treat a loss of DC as an E-Stop via the PLC. No operator input is needed this way.


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## Yellow World (Oct 11, 2017)

MikeFL said:


> Where did you learn such good English? Are you native Taiwan?


No, originally I'm from Germany. Fell in love with a Taiwanese girl and moved here because of her about eight years ago. Looking back, I guess it was the right decision. Changing into a different trade is an almost impossible thing in Germany.


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