Reaccumulation of stored energy definition

[TM519]

Hi everyone. We are following a standard laid out by the station we are performing work at and one of the Work Practices lists that before work is done an equipment evaluation has to be done on whether or not the equipment possesses the ability to re-accumulate energy. I could not find any industry standard definition for what this means and want to make sure we aren't breaking any rules if a definition does exist. Asking the station personnel got us nowhere.

Specifically the standard reads: "Personnel protective grounds are required by OSHA 29 CFR 1910.269 (d) on equipment at generation facilities where there i a potential for the re-accumulation of energy to a hazardous level. When equipment does not possess the ability to re-accumulate energy then grounding is not necessary".

Really appreciate the help here as always.

 

[dkidd]

Found this

https://case.edu/ehs/sites/case.edu.ehs/files/2018-02/LOTO-Written-Program.pdf

▪ Stored energy

• Following the application of lockout or tagout devices to
energy isolating devices, all potentially hazardous stored
or residual energy shall be relieved, disconnected,
restrained and otherwise rendered safe.

• If there is a possibility of reaccumulation of stored energy
to a hazardous level, verification of isolation shall be
continued until the servicing or maintenance is
completed or until the possibility of such accumulation
no longer exists

 

[winnie]

I don't know this in terms of official standards, but my guess as to examples would be systems that can accumulate hazardous levels of energy through capacitance.

For example cables on locked out circuits which can still zap you because of proximity to still energized circuits.

Jon

 

[synchro]

One thing that they may be referring to is the tendency of capacitor voltages to partially build back up after they are discharged because of the phenomena of dielectric absorption in some dielectric materials.
NFPA 70E 360.5(B)(7) states:
"Where recharging can occur due to dielectric absorption or induced voltages, all the capacitor terminals shall be connected together and grounded with a bare or transparent-insulated wire."

It's not due to accumulation of any external energy after the capacitor is discharged, but from energy that is still latent in the polar materials of the dielectric. But perhaps they might consider such an increase in capacitor voltage under a general category of "re-accumulation" in energy because it would be indistiguishable from this external to the capacitor.

 

[TM519]

Thanks for the responses I agree that capacitor discharge seems to be what they were going for since if they are not discharged properly then they could still partially build back up even after the equipment is de-energized. Feel a lot more confident now appreciate the insight.

 

[winnie]

I've also heard of this phenomenon in the parasitic capacitance of motor windings.

Jon