Electrical isolation required for mechanical work?

[BIGEYE]

Mechanical repairs required to a 3 MW, 11 KV standby generator engine. Then
genset also operates on a triad system.
The control side will be isolated to ensure that the prime mover does not
start during repairs.
Is there a need for electrical isolation of the HV alternator & busbar
breaker during repairs? No work will be carried out on the electrical side.
TIA

 

[Louis Bybee]

Mechanical repairs required to a 3 MW, 11 KV standby generator engine. Then
genset also operates on a triad system.
The control side will be isolated to ensure that the prime mover does not
start during repairs.
Is there a need for electrical isolation of the HV alternator & busbar
breaker during repairs? No work will be carried out on the electrical side.
TIA

Wow! The potential for a disaster here is enormous! I can't recommend
strongly enough that you have a competent high voltage electrician, and/or
an electrical engineer evaluate your installation, and the purposed work
before you commence!

Your company, and/or the facility where the work is to be performed should
have an effective and clearly defined high voltage safety procedure in place
for work of this nature before a cover screw is removed. Things such as
racking out switches (not just turning off and locking out), and the
installation of bonding straps between the phase conductors and ground,
multiple locks (one for each individual involved in the process) to be
installed and removed only by the person placing it, working in teams with a
clear chain of command, will be considered and implemented as required.

This is one area where redundancy, and pre work planning is good. You might
not get a second chance!

Louis

 

[daestrom]

Wow! The potential for a disaster here is enormous! I can't recommend
strongly enough that you have a competent high voltage electrician, and/or
an electrical engineer evaluate your installation, and the purposed work
before you commence!

Your company, and/or the facility where the work is to be performed should
have an effective and clearly defined high voltage safety procedure in place
for work of this nature before a cover screw is removed. Things such as
racking out switches (not just turning off and locking out), and the
installation of bonding straps between the phase conductors and ground,
multiple locks (one for each individual involved in the process) to be
installed and removed only by the person placing it, working in teams with a
clear chain of command, will be considered and implemented as required.

This is one area where redundancy, and pre work planning is good. You might
not get a second chance!

He's talking about some mechanics working on the engine, not the HV
generator.

The control circuits should be locked out. The starting mechanism
(something this size is probably started with compressed air) should be
isolated and locked out. Maybe even the fuel supply should be isolated
Don't trust just the control circuit to not start the unit.. And I would
have the output breaker open, racked out and locked to prevent accidental
closure motorizing the unit.

If no one is opening any generator components, the big concern is rolling
the engine over while someone has their hands in it. The generator covers
and wiring are not to be touched in any way. If the work will be extensive
or dusty, cover the generator ventilation with canvas or plastic to prevent
dust getting into unit.

daestrom

 

[BIGEYE]

Thanks guys for your replies. Although no work will be done on the HV
system, electrically it will be made safe with carefully thought out
switching schedule.
It was the mechanical side I was not sure about. But you have put my mind at
ease with your suggestions.