I've seen rods bent into a "U" shape and bolted onto the panel like minature handrails on both sides of the switch.
Another plant used a hinged, clear plastic box over the switch with the hinge at the top. The box could be easily lifted for switch access. The electrician said it was a cheap jewlery box from a discount store.
I have seen L shaped plastic barriers screwed on the switchgear door, on sides of the switches (plastic strips on their 'edges' at right angles to the switchgear door surface).
The best method is to restrict access and have the discipline to not lean on the switchgear. Allow ample working space to walk safely between the line up of switchgear. The guards may end up being an impediment to a ready access in case of an emergency. There must be a reason as to why such gizmos have not been invented in the long history of switchboard designs and use.
I have seen several shipboard switchboards with a wooded handrail mounted on the door that effectively prevents an accidental operation but gives good access for normal operation. I believe Point 8 still provides this as an option, as do some of the other companies marketing to marine and offshore.
They are generally mounted just above and to the outside of the breaker switch, and sometimes other critical switches, like the generator mode control switch, is protected by the same rail.
British transmission substations use a control scheme with two separate 'arm' and 'execute' actions. This forces two distinct operations to open or close a breaker. It is a very secure and reliable system and it is virtually impossible to cause inadvertent operation. The 'arm' function usually cancels itself after a short period, maybe 10 seconds.
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If we learn from our mistakes I'm getting a great education!
Electro-Switch was just in the office. They don't make one.
When sales people ask the switch design engineers, the engineers supposedly said that people who would accidently bump controls should not be allowed around switchgear or relay panels.
"people who would accidently bump controls should not be allowed around switchgear or relay panels"
I agree, but next to hydrogen, idiots are the most common element in the universe. Worse, on occasion non-idiots, people who should KNOW better, have momentary lapses and bump into things.
A good sheet metal fabrication shop can cut, punch and bend what you need. There are several good examples already alluded to in this thread.
Just make sure that the guard does not impede intentional operation of the switch.
The idea of interfering with emergency operation scares me. I think you should consider this issue very carefully. When something is going wrong, it's never a good idea to have a sequence of operations that involves more than one step. Reaching around a "guard" may cause confusion at a critical moment.
As to the comment above regarding wood rails on marine switchgear, the purpose of that is to provide a ready hand-hold as an ALTERNATIVE to the breaker handle if you happen to be walking by when the ship pitches.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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I partly agree about emergency operation, but most times things 'going wrong' on a substation will either happen so quickly that you won't even time to think 'WTF?' before the relays clear the fault. In other instances a few seconds of considered thought before making a decision can often save a mistake being made. Sudden actions often have far-reaching consequences, usually bad ones.
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If we learn from our mistakes I'm getting a great education!
I agree with Scotty. Pistol grips are not emergency trips per se. And even Estops can have covers. That's why I often see pistol grips removed and hung close to the switch and when they are needed they just slide on and can be used.
In a WWII vintage aluminum plant, the recifier station operator's desk sat in front of large duplex panels for four potlines each with 8 rectifer transformers, tap changing auto-transformers, feeders from BPA, and many AC and DC breaker control switches, indicators and alarms. Bell alarm contacts on the 60 + breaker switches sounded a bell above the desk when something tripped. Mounted next to the desk was a pistol grip breaker switch that controlled two lights, nothing else.
Instructions were - "When the bell starts ringing, grab the switch and make the lights flash." That took care of the need to "DO SOMETHING!" and gave the operator a chance to survey the panels and find the real issue while his heartbeat dropped to normal.
I recall two trips from someone bumping a switch and one from a floor polisher bumping the differential relay panel. All were caused by trained personnel with 20+ years experience.
The panels had different shaped handles for different functions- large pistol for AC breakers, small pistol for anode breakers, oblong or diamond for tap changers, etc. Operators told me that helped prevent misoperation several times. Can't do that with an HMI screen.
You can help some on the HMI by requiring select before operate, and then even an execute target if necessary. Some also have an electronic tag that must be removed before operation.
My first week on the job 32 years ago as an engineer for a large motor control equipment mfr had me thrown into a court case to do research on an accident we were being sued over. We made components, but we also assembled them into custom panels (UL508 shop). We had sold power and control components to an OEM of garbage compactors, then he asked us to mount but not wire them in an enclosure for him (of course no UL label either by the way). He then wired up all of the power and control circuits himself.
In the field, an end user got his sleeve caught in the auger that fed the garbage into the compactor ram area. It pulled him in, but someone managed to hit the E-stop and stop the auger. Unfortunately the control circuit was designed wrong and the ram engaged anyway and before he could free himself it tore his arm off. In the midst of that tragedy, a coworker tried to kill power with the main breaker, but the pistol grip handle was hanging on on a chain next to it because people kept using the handle as a hand-hold to hoist themselves up onto the work platform and it kept breaking. By the time he got the handle connected to the shaft, it was too late.
My point is, you never know when "emergency" will apply to even the simplest of devices.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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