Good Old Daze

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What are the PPE & other safety requirements to work in that room?
 
My fist impression was a 48VDC plant in a typical Telco central office. Hence no insulating barriers for
personal safety due to the low voltage. Then I noticed the type of insulators and the POCO metering indicating AC utility service.
I have seen a similar setup on an old cargo ship.....very scarey!!!
One slip when walking thru and it's all over.
What is the system voltage?
 
Smart $ said:
There are fuses below the rear side bus bars (second thumbnail from left; links to full-size picture).
Click to expand...

Yeah, but they look like control fuses or feeder fuses of some sort; not power fuses for that size bus bar. :happysad:

Was the NEC in existence at that time?
 
ATSman said:
Yeah, but they look like control fuses or feeder fuses of some sort; not power fuses for that size bus bar. :happysad:

Was the NEC in existence at that time?
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The conductors connected to the bus are likely tap conductors for whatever loads they supply... and the fuses are sized for the conductor and/or loads.

Don't know when the gear was installed, but I'll guess the NEC existed at that point in time... but it'd fit in your back pocket quite easily. :D
 
Nice post.

That board looked like it was made of slate. I've seen several like it. I saw one in Philadelphia about twice as long and made of beautiful marble. It would have made nice countertops for all of our kitchens with some left over for the bathroom.
 
Old Breakers

Old Breakers

I think those large black switches with the horizontal handles are actually circuit breakers. There are three dash pot trip units under each breaker with a linkage up to the trip element. The dash pot provides the time overcurrent time delay and a solenoid does the instantaneous trip. It's been about 30 years since I had a chance to work on one of those. The arc chutes are very rudimentary which makes it interesting when the breaker trips as you are standing in front of it.

The last ones I worked on were at a steel mill feeding a bank of parallel 250VDC rectifiers for bridge crane power. The instantaneous trips would drop all the breakers open when multiple cranes started lifting. Maintenance had to run to the switchyard and reset the breakers. This happened 2-3 times a month.

The owner requested we defeat the instantaneous trips, assuming they were worn out. All feeders to the rectifiers were short, open bus runs terminating on the rectifier input fuses and the upstream protection looked adequate for protection, so we complied and tye-wrapped the armature flappers in place. Next time the cranes' heavy loads coincided, all the input fuses blew and the cranes were down for a day while they searched for enough replacement fuses. They cut the tye-wraps on the instantaneous trips and went back to five minute outages. (If I knew then what I know now?.)

So the old breakers did work. Just wear ear protection when in the area.
 
250VDVC

250VDVC

rcwilson said:
I think those large black switches with the horizontal handles are actually circuit breakers. There are three dash pot trip units under each breaker with a linkage up to the trip element. The dash pot provides the time overcurrent time delay and a solenoid does the instantaneous trip. It's been about 30 years since I had a chance to work on one of those. The arc chutes are very rudimentary which makes it interesting when the breaker trips as you are standing in front of it.

The last ones I worked on were at a steel mill feeding a bank of parallel 250VDC rectifiers for bridge crane power.
We have some older steel mills in town that have similar setups where 250VDC is utilized for all the crane feeders, there is a central 250VDC-10,000A substation with multiply rectifiers connected, that feeds multiple smaller crane substations in different buildings utilized to power up the overhead cranes, they utilize the slate vertical boards with overhead exposed bus, etc. and switches and relays on one side. At one location I recall there is an open knife blade switch on a section of overhead bus that had wood blocks around the knife blades so it could not be energized one way for LOTO I guess..
Click to expand...
Click to expand...
 
Dashpots

Dashpots

rcwilson said:
I think those large black switches with the horizontal handles are actually circuit breakers. There are three dash pot trip units under each breaker with a linkage up to the trip element. The dash pot provides the time overcurrent time delay and a solenoid does the instantaneous trip. It's been about 30 years since I had a chance to work on one of those. The arc chutes are very rudimentary which makes it interesting when the breaker trips as you are standing in front of it.

The last ones I worked on were at a steel mill feeding a bank of parallel 250VDC rectifiers for bridge crane power. The instantaneous trips would drop all the breakers open when multiple cranes started lifting. Maintenance had to run to the switchyard and reset the breakers. This happened 2-3 times a month.

The owner requested we defeat the instantaneous trips, assuming they were worn out. All feeders to the rectifiers were short, open bus runs terminating on the rectifier input fuses and the upstream protection looked adequate for protection, so we complied and tye-wrapped the armature flappers in place. Next time the cranes' heavy loads coincided, all the input fuses blew and the cranes were down for a day while they searched for enough replacement fuses. They cut the tye-wraps on the instantaneous trips and went back to five minute outages. (If I knew then what I know now?.)

So the old breakers did work. Just wear ear protection when in the area.
Click to expand...

After a closer look, I believe you are correct about the dashpots, RC. The last dashpots I worked on many years ago were part of a motor starter for a Joy compressor. I remember it because the oil had dried up and the plungers were so corroded they would not budge. The next morning the plant supervisor came to me and complained that there was a problem with the dashpots because they kept tripping on start. Turned out the compressor stages were overloading; the dashpots were now operating correctly and just doing their job! :slaphead:
What is strange is in the pic I do not see dashpots on the one to the right of the main.
 
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