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 Post subject: Maintenance of LV components inside HV cabinet
PostPosted: Wed Oct 19, 2016 8:27 am 

Joined: Tue Apr 26, 2016 3:47 pm
Posts: 2
Good Morning All,

I am from the Safety Office and our organization prohibits working on electrical components/systems above 600V. I have a situation that I need advice on. Here is the background:

There is a group of Electronics Technicians/Engineers who believes they are responsible of an electrical system just because it resides in their occupied building. Inside this building is an 15kV CB which disconnects a transformer bank 11.5kV:570V, 540V and an 8.32kV harmonic filter (in a cabinet) from the substation (11.5kV). In this cabinet, there are LV fans and pressure sensors that they guys want to maintain and do housekeeping such as dusting. The management is fully supportive of getting contractors to do this work for them but they are very much adamant that they can do this work since they will be in an electrically safe condition utilizing LOTO (their LOTO procedure was not approved).

Our office has told them they cannot access this cabinet and the lead engineer is very persistent and insisting that they are only working on the LV side inside the HV cabinet. ANY THOUGHTS?


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 Post subject: Re: Maintenance of LV components inside HV cabinet
PostPosted: Wed Oct 19, 2016 7:47 pm 
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Location: North Carolina
glbreakr22 wrote:
Good Morning All,

I am from the Safety Office and our organization prohibits working on electrical components/systems above 600V. I have a situation that I need advice on. Here is the background:

There is a group of Electronics Technicians/Engineers who believes they are responsible of an electrical system just because it resides in their occupied building. Inside this building is an 15kV CB which disconnects a transformer bank 11.5kV:570V, 540V and an 8.32kV harmonic filter (in a cabinet) from the substation (11.5kV). In this cabinet, there are LV fans and pressure sensors that they guys want to maintain and do housekeeping such as dusting. The management is fully supportive of getting contractors to do this work for them but they are very much adamant that they can do this work since they will be in an electrically safe condition utilizing LOTO (their LOTO procedure was not approved).

Our office has told them they cannot access this cabinet and the lead engineer is very persistent and insisting that they are only working on the LV side inside the HV cabinet. ANY THOUGHTS?


1. The basic issue at hand is who is considered qualified. There is no such thing as someone who is qualified to do everything. You may for instance choose to train production employees or mechanics to do a general LOTO. In this context they would need to be qualified to inspect equipment externally and recognize when it is safe to operate disconnects or circuit breakers but most likely not qualified to open the doors and test for absence of voltage. Similarly for electrical workers there is a drastically different technique with drastically different issues in testing <1 kV compared to testing above 1 kV. This video covers exactly what happened when an electrician trained to work on low voltage equipment attempted to test for absence of voltage in a medium voltage starter:
https://www.youtube.com/watch?v=hfnEuRA7-vo

I also don't agree that working in the low voltage cabinet is ALWAYS safe. Never mind troubleshooting (when the condition of the medium voltage side is unknown), as a classic example CT wiring can have extremely high voltage present if handled incorrectly. And once you go down the route of "maintaining" equipment, eventually you will cross the line from preventive maintenance to troubleshooting.

2. You cannot properly maintain electrical equipment without performing energized work. Based on the voltages you mentioned it's not clear what the jurisdiction is but a very basic principal of electrical work is that equipment is considered energized until PROVEN otherwise. That means that in addition to general LOTO procedures, testing for absence of voltage and grounding it is also required. Both of these steps are energized work because...it's not considered an electrically safe working condition (de-energized) until this happens. So having a policy of never doing energized work is utterly crazy. The only practical way to implement it is to contract out ALL electrical work at every voltage. That causes an obvious problem though because ultimately the employer ("owner") is responsible for maintaining their property properly and safely. Without knowledge of how to even accomplish this, its impossible to meet most regulatory requirements.

3. The contractor route though isn't the end of the world. I'm a field service technician. A lot of my customers simply do not have the skills or capability in house to do the work. The second group are those that have say an engineer on staff who knows in general terms what needs to be done but don't have the skills in house. The third case is when they can do it themselves in house but either want confirmation of what their own crew did or else get stuck and need a second set of eyes. And finally sometimes they can easily do it in house but simply lack the manpower or else are under some kind of politically imposed limitation.

4. Finally even though I'm somewhat confirming your point of view, keep in mind that the safety role should not be a road block and simply say no. Instead the role should act as an enabler and explain the specific circumstances under which someone could safely maintain equipment....what specific training is necessary to do medium voltage work and not simply block the effort. With management as well as the local maintenance/engineering group already feeling that they are capable of working on medium voltage equipment when emergencies occur, someone is gong to attempt it. And if they screw it up, bad things can happen. Better to at least set up the chance for them to evaluate the requirements (costs, equipment) themselves to decide if it's worth it.


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