De-energizing an Electrical System under load
De-energizing an Electrical System under load
(OP)
I would like to know what the precautions those are necessary in de-energizing electrical systems [medium/ low voltage switchgears and others] in terms of electrical safety. Can some one explain me the dangers involved if correct procedures were not followed?
Thank you in advance.
Thank you in advance.






RE: De-energizing an Electrical System under load
The thing to consider is the load itself and the consumer. If it is for instance a conveyor that is fully loaded, you can have problems to restart it again. It is more difficult for a motor to start under load than starting without load.
It is also uncomfortable for the consumer if the power is suddenly cut without warning.
Regards
Ralph
RE: De-energizing an Electrical System under load
Do you define 'de-energizing' to mean
"removing all active sources of energy"
or to mean
"removing all active sources of energy and solidly grounding the equipment"
RE: De-energizing an Electrical System under load
Sarg
RE: De-energizing an Electrical System under load
If it is a medium voltage substation switch or distribution cutout, be sure it is rated as a load-break device.
Make sure whatever equipment is being de-energized won't cause hazards by stopping.
RE: De-energizing an Electrical System under load
RE: De-energizing an Electrical System under load
The above procedure is w.r.t simple disconnection. Should you require to maintain the system after disconnection please follow the necessary guidelines w.r.t earthing of the equipment and other safety measures as required per local guidelines.
Cheers
RE: De-energizing an Electrical System under load
Yes, if the equipment works as it is designed and it is applied correctly, the danger is minimal. But there are no guarantees in life. Equipment sometimes fails and engineering errors result in applications outside of ratings. When circuit breakers and switches fail, it is nearly always when they are being operated. Available fault current sometimes changes after installation. Also, it is not unusual for a small amount of flash to escape molded case and air circuit breakers when interrupting fault current. I would rather not have that in my face.
RE: De-energizing an Electrical System under load
RE: De-energizing an Electrical System under load
An electrician on an aircraft carrier had a bus bar come disconnected in a 480V switchgear, with the resultant arc causing a fireball and molten metal killing the lad.
An operator at a power plant opened a 345KV (yup, KV) disconnect under load-the disconnect meant as an isolation device, not load interrupting-and drew a VERY impressive arc, but no damage.
So to answer your last, the dangers if procedures are not followed can be severe-arcs, sparks and injuries.
RE: De-energizing an Electrical System under load