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Working Live - Testing Transformers

1936 Views 15 Replies 11 Participants Last post by  paulengr
Hi Everyone,

I am working as a tech for a power solutions company. For the last two years the scope of my work consists of connecting power quality analyzers (such as the Hioki 3169 or Fluke) to the load side copper pads of the main distribution transformer. This 3 ph transformer is intended to save energy and is tied to the client's bus bars just below the main breaker (near the CT compartment) before the main bus bars feed the risers so that it can actively effect the client's total consumption. In other words, these energy saving transformers are essentially a jumper cable between the main breaker and the client's main bus bars and it steps the voltage down from 600v to 575v.

I know it sounds dumb but I was young, green and hungry when I joined this company so I didn't think much of it and followed instructions. It has dawned on me recently that this work I'm performing live may not be safe? I always suit up with 1000v insulated tested gloves, balaclava, arc helmet with face shield, 12 cal/cm suite, and insulated boots. However, I have recently attended arc flash training ( a little late considering I'm two years in the field...employer decided it would be good for me as I raised a few concerns) and they taught us about reading the arc flash labels to ensure we choose the right ATPV level of PPE according to the incident energy level. Now that I know this, I have been keeping an eye out lately yet none of the transformers that I've worked on have these labels indicating the incident energy level nor the required ATPV. It only has a danger label stating that their is a shock/arc hazard. Mind you, these transformers are 347/600v and typically range from 500KVA-2500KVA. There was one site that surprisingly actually had this arc flash label on the client's switchgear and I kid you not, the main breaker that this transformer was tied too stated "108cal/cm". Now, the risers beside it were all rated at "3.1cal/cm" I'm guessing due to the C.B's protecting it.

I have received conflicting advice from electricians in the field.... one of our sub contractors stated that it is ok to proceed considering that these transformers are tied below the main breaker, his reasoning was that these main C.Bs or Fused disconnects would trip to stop the arc fault since the transformer is connected to it's load side. Moreover, he guessed that it would be in the vicinity of 3cal/cm if it is connected below the main breaker. This makes me feel comfortable as previously stated I'm wearing a 12 cal/cm suit.

However, another electrician was suggesting that it is actually not safe to proceed unless the incident energy level is known. He argued that due to the various KVA ratings from system to system each transformer would have a different incident energy level (makes sense to me). Also, he insisted that the incident energy level available is also based on the trip time settings of the main C.B or fused disconnects.

Now, I am at a standstill, and unsure if I should proceed with my day-to-day operations to test these live transformers or refuse the work completely. Ideally I would love to continue, considering that what I'm doing is deemed safe.

PS - these power quality analyzers utilize alligator clips and Rogowski CT's so there are no tools required for the connections. All of the work is done by hand with insulated gloves on of course.

I decided I would come here to ask the experts before I speak up to HR and sound like a diva if I'm wrong and over reacting...looking forward to all responses!

Cheers.
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PS - these power quality analyzers utilize alligator clips and Rogowski CT's so there are no tools required for the connections. All of the work is done by hand with insulated gloves on of course.

Cheers.
A few things.
1. This company sounds like snake oil salesman, from what you describe the are installing a buck boost xformer to drop voltage. Voltage goes down current goes down, it could be done with taps on the main transformer.
2.You are correct no two systems are the same.
3. It is not the clip on leads or tools it is the trip, pass out or drop something and reflex's take over that can get you.

@brian john will tell you what is correct he does this all the time.
Cowboy
 

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This is the statement I like best.

Moreover, he guessed that it would be in the vicinity of 3cal/cm if it is connected below the main breaker. .
It's like me saying "I guess I'll make it to retirement working hot."
 

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Bring it up to your HR department or better yet, is there a plant engineer?
Put a bug in the plant engineer's ear that some items are not properly labeled.
Once we told our plant engineer about the issue, the front office was on it quick.
If equipment is not labeled, dress to the max arc flash clothing you have.
Even better would be for you to do an arc flash calculation of your own and let them know you know what you are talking about.
The arc flash class should have shown you how to make the calculation, even if you are not an engineer.
 

· Hackenschmidt
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one of our sub contractors stated that it is ok to proceed considering that these transformers are tied below the main breaker ... guessed that it would be in the vicinity of 3cal/cm if it is connected below the main breaker...

However, another electrician was suggesting that it is actually not safe to proceed unless the incident energy level is known...
It's a lot more dangerous to think you know when you don't, than to know what you don't know. It's just not safe to base the safety precautions for the work you're doing, on some halfassed guessing.

Sometimes taking responsibility for your own safety means refusing work.
 

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The post is confusing as the OP talks about why they are doing a power study which sounds like hot work then later points out they are simply doing a power study which is live front rather than hot work.

Working live front when you had no idea of the power of a arc flash was easy. As long as you was careful about contact everything would be fine.
Now you have been taught about arc flash and the fact it does not require you to touch anything the job just got complicated. It doesn't matter if you have a breaker that set to the lowest settings if you can see the wires/plates going into the breaker then you are exposed to the arc flash potential of the incoming supply.

Brian is asking the important questions
 

· Chief Flunky
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First the product your company is selling is total crap. Buck boost transformers are real. They have been around for over a century. So ask yourself why every transformer doesn’t come with one or it isn’t a standard option that nearly every company installs? Two reasons. First as an energy savings are you trying to say that the core losses don’t undo every bit of energy savings? What a joke. Second why bother when you can just change the tap changer setting on the transformer if you did this job properly in 5 minutes and give the customer a bill for engineering, cutting out your labor and making a lot more money?

The company owners are scam artists. They don’t care about anyone but themselves. Get another job lined up and drop a dime on them. They shouldn’t be in business.

Ok so if you took the training on Z264 or 70E then you know that the only time you would be doing live work is testing, first to verify power is truly off and second to verify voltage after you are done. Doing energized circuit alterations in a non-utility environment is utterly stupid. If your company is doing this one call to OH&S and they won’t be doing that again if they are still in business.

The trigger for arc flash is whether or not there is more than a remote chance of something you are doing causing an arc flash. As an example with the breaker off is there any activity that you are doing where tools, materials, or any part of your body can inadvertently get too close to the top of the breaker? I work on industrial control panels every day and I would say no. As qualified workers we stay away from those areas. However we had a trainee struggling to lift a VFD into place. He instinctively looked for a place to get some leverage and grabbed the top of the breaker before anyone could stop him. That’s just one example. Other than the hassle the utility will disconnect power for free and the risk to you is zero. Why do it any other way?

If a panel is not labeled the same engineering companies that charge typically over $30,000 and take months to generate labels are the same ones saying every panel must have a label or you can’t work on it. That is not what Z264/70E says. Sure your company could refuse to do the job:. But the owners are clearly predatory anyways and don’t give two hoots about sacrificing you so they obviously don’t care about that.

But even if you followed the standard you would use the table in it that says ATPV 40 and if it was labeled 108 Oberon sells a 150 cal suit. You are dressing in 12 cal. That would be like wearing a fall protection harness without the lanyard...it’s not gong to do anything anyways so why bother with the hassle? You either wear the correct PPE needed for the job or find another way to do the job. Don’t waste your time on the PPE if it’s not the right stuff. So realistically you use the table based method in Z264/70E when no information is available.

Finally the incoming bus in most plants is always a guess. The utility uses a network (ties) so the information they supply is not very good. It is OK for breaker sizing but not arc flash. That’s where you are working. It’s an area best treated as if there is no proper PPE so you take extra steps to avoid situations like someone reaching for the top of the breaker. The reason for the crazy high number is because if something did go wrong as the air heats up in the cabinet it ceases to be an insulator. That’s what makes arc flash self sustaining in the first place. Sometimes the heated air allows the arc to jump from the load to the line side of the breaker so the entire breaker cabinet gets the line side rating regardless of if you are on the load side or not. So seeing say 108 on a main breaker and 3 cal on the cabinet next to it is normal. Chances are the line side is only protected by the cutout fuses on the primary side of the utility transformer. Those fuses must be large enough to avoid transformer inrush so they don’t protect against anything except severe faults and only with significant time delay on the secondary side. This applies to ALL the transformer sizes you mentioned. The only thing between you and the burn center is skill and luck. Hint: that is your work site.

I work energized all the time. Got a big breaker job (4160) next week. And I will be doing all of it de-energized except final racking in the breakers.
 

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First the product your company is selling is total crap. Buck boost transformers are real. They have been around for over a century. So ask yourself why every transformer doesn’t come with one or it isn’t a standard option that nearly every company installs? Two reasons. First as an energy savings are you trying to say that the core losses don’t undo every bit of energy savings? What a joke. Second why bother when you can just change the tap changer setting on the transformer if you did this job properly in 5 minutes and give the customer a bill for engineering, cutting out your labor and making a lot more money?

The company owners are scam artists. They don’t care about anyone but themselves. Get another job lined up and drop a dime on them. They shouldn’t be in business.
My first thoughts
 

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there is a lot of fantastic information provided buy the commenters.
You may already know this but then again maybe not.
I have never owned a set of gloves rated for 1000v which are class Zero. Because of what I used to do I started at class 2 and kept a class 4 in the locker. These are tested every 6 months. Since I learned from an old fart that succeed in surviving 50 years in the trade I mark my gloves. I use a colored marker dot near the size. Very small. Once in my career did I get my glove back and only one. Usually just new rubbers. So why bother, just replace every 6 months. Save the expense of testing. But that is another pet peeve about the industry.
I suggest that you may need to look for another location to do the readings. Maybe a different spot that is safer for you. I used to use the RPM a lot on studies. Before the machine was sold to Fluke.
There were times even with a suit I did not feel comfortable with what they wanted done. I forced an outage to install and again to remove a couple of times. There is only one you.

HR is generally not your friend. Everything you say will end up in your bosses in basket.
Ask the boss for training, and the equipment to do the job.
How long have you had your suit? Do you clean it? Do you lay it on the ground to get the pants on? Did they teach you how to take care of it?
Wild ass thoughts from a guy that put a suit on and took it off 10-12 times a day when we were doing switching. Never stand in front of the switch during operation. you know that right? There are plants that have remote switching for any switch operation. Here is one
I have used this one and it does NOT fit every old breaker or handle out there.

Do not share gloves and inspect them before every use.


Working live in my opinion should be done in pairs. Not likely in to days market.
 

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Working on live circuits should only be done as a last resort and not as a normal practice. Your company should ask for a shut down window where you can attach test equipment and then re-energize when you are clear of the Ark Flash zone. I realize it's a total pain in the rear some times but why is it that a persons safety is less important than production.
 

· Chief Flunky
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Working on live circuits should only be done as a last resort and not as a normal practice. Your company should ask for a shut down window where you can attach test equipment and then re-energize when you are clear of the Ark Flash zone. I realize it's a total pain in the rear some times but why is it that a persons safety is less important than production.
Electrical LOTO requires testing for absence of voltage. You assume everything is live until proven dead. That makes LOTO live work.

This statement to not work live is right out of the Codes and utter crap because every electrician except trainees and installers MUST work live just so that they don’t have to work live during the LOTO process.

In addition the discussion is around transformers. How do you determine voltage and/or set the taps if you can’t measure the voltage? How do you measure the output voltage on a de-energized transformer?

Don’t be another dumb A-hole safety department idiot that declares that we can’t do any live work when it must be done every day all the time as part of the exact same procedures that also say no live work unless NECESSARY. That is not the same as “last resort”. The idiots that wrote that safety standard for 20 years gave IEC or UL 61010 as the procedure for testing for dead circuits. Do you know what that standard is for? How to build a meter! It tells the meter manufacturer what the test requirements are for how far apart to make the meter probe connections.

This is a forum for professional electricians, not hacks that are so dangerous on the job site we make them safety managers. Professionals do live work all the time. But there is a time and a place for it and they know that or should such as installing transformers while energized in a non-utility environment.
 

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You have worked for the same idiots I have! Must be a school turning them out
The mine used to preach dead knowing full well that the protective devices are not able to be trouble shot in that condition. Some of out protective devices would shut the shovels off. Out goes the call the 24 shovel lost power. One to the substation feeding it and one to the switch box, then both to the shovel for a complete startup. We got paid buy the hour.
 

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Electrical LOTO requires testing for absence of voltage. You assume everything is live until proven dead. That makes LOTO live work.

This statement to not work live is right out of the Codes and utter crap because every electrician except trainees and installers MUST work live just so that they don’t have to work live during the LOTO process.

In addition the discussion is around transformers. How do you determine voltage and/or set the taps if you can’t measure the voltage? How do you measure the output voltage on a de-energized transformer?

Don’t be another dumb A-hole safety department idiot that declares that we can’t do any live work when it must be done every day all the time as part of the exact same procedures that also say no live work unless NECESSARY. That is not the same as “last resort”. The idiots that wrote that safety standard for 20 years gave IEC or UL 61010 as the procedure for testing for dead circuits. Do you know what that standard is for? How to build a meter! It tells the meter manufacturer what the test requirements are for how far apart to make the meter probe connections.

This is a forum for professional electricians, not hacks that are so dangerous on the job site we make them safety managers. Professionals do live work all the time. But there is a time and a place for it and they know that or should such as installing transformers while energized in a non-utility environment.
Wow! You really slammed me kind of hard with your statement. I thought safety was important to people working in our trade and you must have missed my point on that.

I understand that LOTO could be live work if you had a failure of equipment such as a knife switch stuck in the closed position. That’s what meters are for.

I also know that LOTO is not only for checking for voltage and slamming a lock and tag on a piece of equipment and jumping in to work. Electrical is not the only form of energy and we need to watch out for other things like hydraulic, pneumatic, stored and kinetic energy when working on machinery. Once you have determined all sources of energy have been addressed you are ready to preform service to the equipment.

I realize this discussion is about transformers. Why are they any different than other types of equipment like panel boards? Simply de-energize the circuit dawn your safety gear and test for voltage. Once you have determined there is no voltage present you are ready to place your CT’s and alligator clips. Why do that hot if you don’t have to.

My point was simply this. You are the master of your trade and in control of what you do so don’t let a supervisor or customer dictate your safety.

I’m probably considered an unsafe worker as I do work stuff hot all the time. I just did not want to give bad advice to the new generation of electricians who have to follow safety rules that are so prevalent in our field now days. If you get hurt working something live and you don’t follow the rules you will probably get thrown under the bus if you are injured.
 

· Chief Flunky
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One thing I learned from arc flash training is that even with PPE you'll still get f'ed up when it goes boom.

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Really, how?

I will agree with one thing. If you take a really hard look at the whole arc flash idea it becomes very obvious that the “science” is utter crap. For example the calculated incident energy is 18 inches from the point of origin. The idea is that is roughly the distance to the face/chest area (most vulnerable) if you have your hands on something. So how far away are your hands at that point? What would the incident energy be at your hands? Why do we use the same ATPV rating for the entire body even though it’s obvious this is totally wrong? This is the problem with arc flash as it is practiced today...no self respecting engineer can possibly defend the “science” of arc flash based on theoretical scientific evidence. Any decent electrician can poke wide gaping holes in the “science”. So yes I’d agree that scientifically there is no way you would not expect injuries.

But what about results?

We can look at the DuPont study as well as OSHA and other data. The DuPont study looked at all the incidents they could find data on, about 55 total. Of those that used the IEEE 1584 calculation method (“arc flash study”) and had proper PPE on based on those results, there were no or only minor injuries such as burns on the wrists were the cuffs of gloves didn’t cover them. To date there have been NO hospitalizations following that standard after about 20 years of history. So let’s ignore the dubious way that it is implemented right now. It is clearly working regardless of the science. If anything it says that method is wildly overly protective. But it’s hard to argue with success.

The DuPont study also had situations where the victims followed the 70E table method which at the time gave decreased PPE requirements based on decreased likelihood of an arc flash. Not decreased severity of injuries, only that you might not get injured. The 2015 and later editions finally got rid of this. You either need the full PPE or you don’t. This should have prevented even those cases. It also documented a case where the electrician felt the PPE was too hot to wear so cut the sleeves off for comfort and needless to say was burned on the arms but torso was fine. Of all the cases where they were burned anyway, it’s pretty obvious why.

At a large chemical plant where I worked in the past we had lots of files on arc flash incidents. There are tons of cases where the victims walked away unharmed when wearing the PPE we required.
 
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