Tripping Main Breaker in a controlled fashion

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mull982

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I am performing a controlled plant power shutdown tomorrow on my system which is typically running at about 10MVA. To do this I am going to open our main 5kV Siemens GMI breaker rated for 3000A. This breaker feeds several 1500kVA transformers which will typically be in service during opening of the breaker.

My question is after we are done with the power outage what is the proper procedure for picking back up load with the main breaker. In other words when I go to rack my main breaker back in, can I have other various loads in the plant (transformers, etc...) connected or do I have to close the main breaker with no load connected at all? I guess what it boils down to, is what or where can I look at on the breaker to find out what load its rated to pick up.

In the past I've only been concerned that the inrush of the transformers all at once would trip the main, but is there anything elese to factor in here?
 
ron

ron

Senior Member
Location
New York, 40.7514,-73.9925
To help the longevity of the main and avoiding trip on inrush, shut down the downstream loads one at a time before shutting off the main, then for restore, turn the main on first and then one at a time turn on the down stream transformers.
 
zog

zog

Senior Member
Location
Charlotte, NC
Good engineering practice to alway de-energize a system from load to source and renergize from source to load. Minimizes waer and tear on your system, GMI breakers cant take much abuse.
 
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petersonra

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Location
Northern illinois
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engineer
personally, since it is a controlled shutdown, I would be inclined to have the users shut off their loads downstream before opening the main breaker, and then have them turn them back on after the main breaker is closed again.

i suspect it does not make all that much difference to the breaker on a one time basis, but if you do it many times it just might.

does this breaker trip after the power comes back on after a power failure? if not, what reason would you have to believe it will trip in this case?
 
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VinceS

Senior Member
Slightly off topic, but...

Slightly off topic, but...

Have you considered integrating static switch's and a timed restore function. Each major load on the main could be restored on some programed critical to non-critical basis. ie.... lights & fire protection, then critical equipment, ect... There are various manufactures. I have used these on 480VAC in a Government ( Unlimited Funding ) application. There is a cost issue which may be prohibitive.
 
zog

zog

Senior Member
Location
Charlotte, NC
brian john said:
Every week we shut down at least one facilirty for maintenance I am taking Vinces suggestion, I finally get that new Rolls.
Click to expand...

Dont see you as a man RR Brian, get a M3 for you and one for the missus and take a long vacation instead.
 
mayanees

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
process for re-energization

process for re-energization

mull...

Restoration of power should be tailored to your system architecture.

That is to say that if you have a situation where your substations are fed through old fused switches, avoid operation of those switches since they could be problematic, and instead perhaps pull them in with a medium voltage breaker.

That advice is based on mis-operation of 15kV fused switches after PM operations, where the switch hangs up - because it's old.

JM
 
mdshunk

mdshunk

Senior Member
Location
Right here.
mayanees said:
That advice is based on mis-operation of 15kV fused switches after PM operations, where the switch hangs up - because it's old.
Click to expand...
I have a feeling that there's more to that story! Mis-operation sounds like code for "the damn thing blew up". :smile:
 
mayanees

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
operators wouldn't operate....

operators wouldn't operate....

zog said:
No. it is code for it wasnt maintained correctly.
Click to expand...
I forget the manufactuer for the switches, maybe Westinghouse, but they were 15kV, 600A, with a cable operator. Pull out the 30" 1/2" diameter prybar and torque the switch into position with a bang from the spring/cocked operator. Sometimes the cable would jump out of it's slots or snap.

Yes a story.. but lucky for me a boring one!

John M
 
zog

zog

Senior Member
Location
Charlotte, NC
mayanees said:
I forget the manufactuer for the switches, maybe Westinghouse, but they were 15kV, 600A, with a cable operator. Pull out the 30" 1/2" diameter prybar and torque the switch into position with a bang from the spring/cocked operator. Sometimes the cable would jump out of it's slots or snap.

Yes a story.. but lucky for me a boring one!

John M
Click to expand...

We carry those cables on out service vans, along with replacement chains for the ITE ones.
 
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