Working on Stored Energy devices (UPS)

[Walter349]

Can anyone advise on whether there is a need for a specific electrical qualification to work on the internals of UPS devices, or if a 16th edition qualified electrical engineer can do so, without impacting safety, H&S and insurance concerns.

 

[ScottyUK]

Nothing in legislation that I'm aware of, but I'd expect a reasonable understanding of power electronics from anyone working with the internal circuitry. Are you considering an electrician or a qualified technician / engineer? The 16th Edition reference suggests an electrician backgound, but since the (now superceded) 16th Ed. relates to wiring for electrical installations I don't really see why that would be any basis for working on a fairly complex piece of electronics. If you're looking for a specific qualification I'd suggest an HNC or HND in electrical / electronic engineering with some on-the-job training from a UPS manufacturer would a reasonable expectation. That allied to a familiarity with the 16th Ed. or 17th Ed. and electrical safe working procedures would be even better.

If you expand a little on your original post maybe we could help a bit more.


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If we learn from our mistakes I'm getting a great education!

 

[dpc]

Can you enlighten us colonials on the reference to "16th Edition" and "17th Edition"?

Thanks,

Dave

 

[Walter349]

Ahh the poor benighted souls living in the backwaters across the pond.

The 16th Edition and 17th Edition are the IEEE Wiring regulations, 17th being the most recent.

We have some emergent issues with UPS modules. The corrective action is a technical intervention in the modules, requiring the replacement of a fusing element as it is incorrectly rated. I won't go into the problems it has caused. Bad is a good general description.

It has taken some months to identify the root cause and devise a resolution.

Problem: I am stating that it is inappropriate for an electrician to carry out the technical intervention, unless they are qualified to work on stored energy equipment.

This impacts future safe operation. Personnel insurance cover. Validation of the work carried out to any sort of standard. Etc.

Opinion, conjecture, outright lies appreciated.

Seriously, this presents a serious problem.

 

[davidbeach]

My guess is that they are really IEE rather than IEEE.

 

[ScottyUK]

I don't know what environment you work in or what safe working procedures are in place, but I'll give an opinion from the power generation industry where pretty much every task is carried out under a permit-to-work system.

[ul disc]
[li]The Electricity At Work Regulations are very specific about the circumstances under which live working is permitted. From the sound of this job those circumstances probably don't apply here. Inconvenience of shutting down the equipment isn't a valid reason for live working in the eyes of the EAW Regs.[/li]

[li]Isolating the equipment prior to work, proving the isolation is effective, and ensuring any stored energy within the unit is discharged prior commencing the task should be done by a competent person. The 'Competent Person' must have enough sufficient experience and training relating to the work in progress to be able to recognise and mitigate any hazard present. Most electricians will not have the requisite level of expertise to do this safely in a complex piece of equipment such as a UPS in a manner which does not cause a risk to both themselves and the equipment.[/li]

[li]Isolations are locked and the keys are held by the Senior Authorised Person issuing the permit-to-work. Sites without a PTW system may allow the keys to be held by the working party.[/li]

[li]Once the equipment is isolated and proven electrically dead the task becomes what we know as 'General Cold Work' or GCW. Hazards such as stored energy aren't a problem because they have either been isolated (batteries) or isolated and discharged (capacitors) and that state has been proven prior to work commencing.[/li]

[li]If the unit is isolated and proven dead and the task is GCW then I see no reason why an electrician can not work on components which are reasonably familiar to him, such as the fuse arrangement in your example. Equally I wouldn't normally expect to see an electrician replacing circuit boards or working on the power semiconductors because working on those items requires additional training and awareness which is typically possessed by a technician or engineer.[/li]

[li]Once the electrician has completed the task it should be inspected and signed off by the competent person. That's just good practice, whatever the task is.[/li]
[/ul disc]

The long and short... no reason why an electrician can't do the work on the fusing arrangement, provided that someone with adequate knowledge of the equipment has made it safe for him to do so.

If components are being substituted then the selection of the replacement part should be made by someone with sufficient experience, qualifications and knowledge of the specific application to make that substitution.


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If we learn from our mistakes I'm getting a great education!

 

[Walter349]

I remember the permit for work system, as I worked on Nuclear power station for a few years.

Won't work in this case. for whole host of reasons.

My main concern is get the work done by a demonstrably competent person, to anything like a standard.

That means if anything goes 'Sputz!' later, we are covered. My difficulty is trying to get some European cousins to understand that letting anyone have a go at it, does not really meet the need.

Oh! and you'll love this one, there was no manual isolation fitted.

 

[ScottyUK]

Even if you don't have a PTW system the principles still hold: lock the isolation points, control the keys to the locks, prove the system is dead and discharged.

Competent person - absolutely necessary. Competence needs to be assessed in relation to the equipment being worked upon - familiarity, training, experience, etc.

No lockable isolation point? Sounds like a marvellous installation! Maybe provision of that should be one of the first problems to address? Out of curiousity, where is this installation?


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If we learn from our mistakes I'm getting a great education!

 

[Walter349]

Its being corrected, but trying to get a proper corrective action plan in being is proving..... Difficult.

The Isolation issue, secondary by-pass etc is also on the list.

I have yet to see anything, even vaguely resembling a wiring diagram and the original design called for redundant incomers, that have never been fitted.

And telling people that they should not be messing around inside the UPS cabinet with screwdrivers and stuff because

a. They are not qualified
b. They have no idea what they are doing
c. It will automatically invalidate any accident insurance cover.

Has not been well received.

 

[SteveFehr]

If you're talking about a UPS on a US military installation in Europe, there is no hard and fast requirement on what training is required, and certainly no licensing. All the documentation is vague and subjective, but boils down to a judgment call on whether the personnel are trained and knowledgeable enough to accomplish the work. But even that can be waived by the responsible CO.

What model UPS is this? Powerware and Liebert have formal 3-5 day training classes that will certainly qualify anyone with an electrical background to service and repair the UPS. MGE doesn't; I'm not sure about Toshiba, GE and the others. It's honestly not that difficult to accomplish- servicing a big UPS is just like working on a car, you break out the ratchet and socket set and go to work. They're designed to be worked on while certain sections are energized- every UPS I'm familiar with actually requires it for PMS. But you'd have to find out from the manufacturer if what you intend to do is safe.

We send our personnel to UPS school to get smart on it to operate it and fix it in an emergency, but still prefer they not enact repairs when it breaks, because it's very easy to mess something up that will send bad power to the critical load and it's much less risk just to suck it up and fly in an expert who does this day in and day out, knows all the little ramifications and how to configure it, and is less prone to making mistakes. Considering you don't have diagrams and aren't familiar with the unit and can't completely isolate power to it, I'd recommend not doing it in-house... but that's not to say it can't be done. Do you have any tech reps in your parent command you might be able to call in to help?

I've been through Powerware 9315 school, if by an amazing coincidence this happens to be a mid-sized 9315.

 

[AECproject]

Can you give some more info on the UPS?

Some UPS's have an internal bypass switch that can be operated to isolate parts of the machine to enable maintenance without diconnection of the supply.

All installations I deal with have an external bypass switch also...not sure if yours does?

By operating the Bypass the UPS will be taken out of the ciruit routing raw mains to the load instead of throught the UPS rectifier. This will in effect isolate the UPS to allow maintenance to take place.

NOTE: Incorrect operation of the bypasses will cause loss of load...

We offer UPS purchase, installation, repair & maintenance, we have numerous engineers all of which must have an Electrical & Electronic qualification (C&G/HND/BTEC/NVQ). On top of this all must have the 17th Edition and received training from the manufacturer (normally at least 1 week).

Hope that helps a little,

AEC Power Control - Uninteruptable Power Supply Solutions, backup power specialists...for more information see our website -

http://www.aeceuro.co.uk

 

[ausgen]

Isolation is fairly straight forward as long as you know where the sources (rectifier, bypass, battery, output if paralleling) are switched. ScottyUK mentioned a critical point though, large UPS can carry significant energy in filter caps once isolated so best to isolate then wait a while before diving in. As caps are a relatively common failure point in an UPS, an electrician without specific training may quite easily turn the relevant CBs off and be across a set of 500 V DC terminals with his tools before they've had a chance to dissipate.

 

[ruggedscot]

UPS systems need to have some specific knowledge and understanding. Anyone working on such a system needs to be fully aware of the set up and of the operation of the unit. Ive worked on some UPS installations where the load can not be left without protection so there are several units in parallel aswell as another source configured in the same way giving two supply sources both UPS'ed to the critical load.

Maintaining one set doesnt involve putting into system into bypass but simply taking it out of service and putting it down. This is done through isolation and locking off then proving that the unit is dead. Large battery setup supplying around 570vdc to a motor that turns a generator the generator supplying the load, that sort of set up.

So it requires a full understanding of the system and its layout. A grounding in electrical works and a fear of dropping the load !

Rugged

 

[SteveFehr]

The shut-down procedure for many large UPS systems involves bleeding the DC bus prior to shut-down. You generally secure the rectifier input and battery breakers, and watch the DC voltage diminish to nothing before securing it completely for maintenance.