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Yes, this will be a big improvement in electrical safety. Probably cost is the big reason why it isn’t done more. It’s always difficult to convince management people to spend more than they have to for any installation.
One thing we did as a temporary measure with MCC’s and switchgear was install custom-made time delay close/trip switches, to allow personnel time to simply get out of the way while the breaker closes or trips. But the need to withdraw the breaker still presents a hazard. That’s where this new withdrawal solution can make it safer.
Very good point Johan. PPE must be used weather the panel is Arc resistant or not.
If panel is arc resistant PPE requirement may become quite low but it should not be
neglected.@ Steve
Thank you Steve, you have expounded an interesting safety solution for maintenance operators.
Could you tell us more about this system?
Is it only on incomers? (It seems complicated on feeders in low voltage)
Thank you for your interest, Laurent. Our Plant is a Class 4 Wastewater/Sewage Treatment Plant, with two 27.6 kV incoming lines, and 4160 volt distribution across the plant, to 600 volt MCC’s, etc. After a Plant-wide electrical assessment was done two years ago, and an Arc Flash Study completed, we found that some of our arc flash levels were too high for any PPE to protect. So, we talked to Electroswitch, who were beginning to manufacture Close/Trip switches with built-in electronic time delay relays. They feature the usual pistol grip for immediate closing or tripping, with the addition of time-delayed closing and tripping by means of color-coded push buttons, with LED’s that flash as the timer is timing. During the last few seconds of timing, the LED will flash at twice the frequency, as an added warning that closing or tripping is about to occur. These switches also have the feature of allowing you to ‘cancel’ the timing sequence by pressing the other push button. For example, if you are timing out a Closing operation, you can cancel it during the timing by pressing the Trip button. We have a system of Main-Tie-Main breakers on our substation breakers and on our 600 volt switchgear mains, and these are the breakers that we are installing the time-delay switches on, wherever there were existing Close/Trip switches. (So we did not put them on MCC’s, for example). What this does for us is 1) It gives us immediate protection for personnel doing the switching, and 2) It buys us time to have the proper engineering done to mitigate the arc flash hazard levels.
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