Name of Disconnect Switch

[mbrooke]

We had some 1600A knife switches. The only way I could open one was grab the handle, put my feet against the panel and throw myself backwards. For some reason I always ended up flat on my back.

UK’s health and safety executive threatened to shut our plants down unless we got rid of all the open switchgear.

This is the back of the last one I took out.

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Red White Black? Is that what the UK used to use before Red Yellow Blue? BTW, that is eye candy

 

[Tony S]

It was red, white, blue and black when I started my apprenticeship (that long ago), yellow came later. Now replaced with brown, black, grey and blue for neutral. Trying to sort them out in low light is a nightmare.

One step forward, two steps back springs to mind.

 

[Tony S]

Red White Black? Is that what the UK used to use before Red Yellow Blue? BTW, that is eye candy

Red, white and black was for DC systems.

 

[mbrooke]

Red, white and black was for DC systems.

I see. BTW- I think that should have been used for 3 phase- I like it. At least thats what the Swiss did before the horrendous Brown Black Grey coloring.

 

[kwired]

It was code in the era it was installed,
The building is insured, no OSHA complaints
Procedural wise I have never work on it

I do no they have plans to upgrade the equipment and there is an electrical engineer working on the project

I have to agree with what Jraef said, OSHA won't make them change it, but should someone be electrocuted and they investigate (and they likely will after a death) they will want to know every detail of what the safety procedures are for working in/around that gear.

None of their penalties will bring back the person that was killed either, nor will the civil lawsuits that the surviving family may bring on.

 

[Tony S]

I see. BTW- I think that should have been used for 3 phase- I like it. At least thats what the Swiss did before the horrendous Brown Black Grey coloring.

Blue being reassigned as neutral instead of a phase colour and then black reassigned as a phase colour was a monumental blunder. I don’t know of any deaths caused by it but I know of several close calls due to it.

All done in the name of European harmonisation. Many countries just ignored the ruling and carried on as before. A damned site safer option in my opinion.

Unfortunately Brexit won’t change anything as the UK is tied in to the IEC, more fool us!

 

[mauk]

I saw an interesting variation of these in a late 1920's building. The compartment doors appear to operate as the switching mechanism?

 

[kwired]

I saw an interesting variation of these in a late 1920's building. The compartment doors appear to operate as the switching mechanism?

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Pretty good design considering what else was out there then. You are still exposed to live components when opened, but the fuses (the part you likely need to access) are on the door and are not energized when opened.

 

[steve66]

So what is proper procedure to do anything involving that switchboard?

Turn off the main supply, suit up to check for voltage, possibly on every exposed conductive surface to ensure it is off, then proceed with the task you intended to do?

What allows that to remain in place? If not OSHA, then you would at least think no insurance company will be interested in insuring something like that and would push owner to want to replace with something considered safer.

Actually, that brings up one advantage of the old knife switches. One I didn't think about until I saw the pics of the gear with the fuses on the doors.

One would be able to visually verify that the switch was in the open position and de-energized.

Checking for voltage probably would have seemed silly to the people that operated and worked on these. Something along the lines of "I can see its obviously open with my own eyes. Why would I trust some meter more than my own eyes."

Similar thing with the fuses on the front door. With the door open, you know the fuses are de-energized just by looking.

In effect, the need to check for voltage and the need to verify equipment is de-energized was probably a result of the dead front designs where you couldn't see the mechanism. Of course, circuit breakers would have eventually required the same check even if dead front designs hadn't come along.

 

[Coppersmith]

Of course, circuit breakers would have eventually required the same check even if dead front designs hadn't come along.

I turn off a circuit breaker and then verify the circuit is off with a ticker or meter just in case the mechanism in the breaker stuck closed or I opened the wrong breaker.

 

[cpickett]

Actually, that brings up one advantage of the old knife switches. One I didn't think about until I saw the pics of the gear with the fuses on the doors.

One would be able to visually verify that the switch was in the open position and de-energized.

Checking for voltage probably would have seemed silly to the people that operated and worked on these. Something along the lines of "I can see its obviously open with my own eyes. Why would I trust some meter more than my own eyes."

Similar thing with the fuses on the front door. With the door open, you know the fuses are de-energized just by looking.

In effect, the need to check for voltage and the need to verify equipment is de-energized was probably a result of the dead front designs where you couldn't see the mechanism. Of course, circuit breakers would have eventually required the same check even if dead front designs hadn't come along.

Visual disconnects are required in mining, so power centers and the like have windows where you can look in and verify all three phases are open.

 

[steve66]

I turn off a circuit breaker and then verify the circuit is off with a ticker or meter just in case the mechanism in the breaker stuck closed or I opened the wrong breaker.

Yes, isn't that the standard (required) procedure nowdays?
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Visual disconnects are required in mining, so power centers and the like have windows where you can look in and verify all three phases are open.

That sounds like the best of both worlds. But how does that work with circuit breakers?

 

[cpickett]

That sounds like the best of both worlds. But how does that work with circuit breakers?​

Most of the visual disconnects are for high voltage coming into a power center (skid with transformers, circuit breakers, etc. Basically skid mounted switchgear). That's what you lock out for maintenance. There will be fuses or a circuit breaker after the disconnect.

Additionally, all of the circuit breakers have a solenoid that has to have power in order to set/close the circuit breaker. There are door switches on all the access covers that wire back to that solenoid on the main circuit breaker, so that if a cover is opened power is killed to the entire unit. For all the branch circuits, there is a ground monitoring wire (pilot wire) in each trailing cable that if the EGC is lost to a piece of equipment that breaker will trip.

Also, high voltage underground will be high resistance grounded with a ground fault relay in order to reduce risk of arc flash. Many layers of protection that make sense, but also increase cost and maintenance time. The environment demands the high level of protection though.