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 Post subject: Troubleshooting switchgear
PostPosted: Sat Mar 27, 2010 10:59 am 
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Joined: Thu Mar 25, 2010 1:09 pm
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In our 15 kV metal-clad distribution systems we have several types of circuit breakers. (SF6, DST-2, Vacuum)

If I have to troubleshoot or check wire numbers or ??? on the 120 vdc control circuits, I have to open the breaker's cubicle door to access the terminal strips, fuses, or rear portions of the protective relays.

When I look through Z462-08, table 4, on page 46 I believe it says the Hazard/risk category is "2", with rubber gloves and insulated or insulating hand tools required.

Others believe that when I open the cubicle doors I'm automatically a "4" Hazard/risk category.

With the cubicle doors open, there is no open & exposed equipment, other than the 120 vdc control.

Any comments would be much appreciated.


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PostPosted: Sat Mar 27, 2010 12:18 pm 
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Location: Western Canada
lightfl wrote:
In our 15 kV metal-clad distribution systems we have several types of circuit breakers. (SF6, DST-2, Vacuum)

If I have to troubleshoot or check wire numbers or ??? on the 120 vdc control circuits, I have to open the breaker's cubicle door to access the terminal strips, fuses, or rear portions of the protective relays.

When I look through Z462-08, table 4, on page 46 I believe it says the Hazard/risk category is "2", with rubber gloves and insulated or insulating hand tools required.

Others believe that when I open the cubicle doors I'm automatically a "4" Hazard/risk category.

With the cubicle doors open, there is no open & exposed equipment, other than the 120 vdc control.

Any comments would be much appreciated.


I would go with the lower rating although this should be covered by an Energised Work Permit. The hazardous voltage is guarded by the switchgear design but the control voltage exposure exceeds 50 volts so you definitely need something. Table 4 is the most mis-used and abused part of the the standard so be sure you read the notes to ensure the system characteristics apply. A safe compromise would be to gear up for shock hazard and definitely DO A PRE-JOB ASSESSMENT. There is no reason to apply a cat 4 level of PPE when you open the cubicle door but there is a high risk of a shock hazard so voltage rated tools and gloves must be worn. Your company policy will determine PPE levels through the Energised Work Permit process.


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PostPosted: Mon Mar 29, 2010 5:20 am 
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Canuck01 wrote:
I would go with the lower rating although this should be covered by an Energised Work Permit. The hazardous voltage is guarded by the switchgear design but the control voltage exposure exceeds 50 volts so you definitely need something. Table 4 is the most mis-used and abused part of the the standard so be sure you read the notes to ensure the system characteristics apply. A safe compromise would be to gear up for shock hazard and definitely DO A PRE-JOB ASSESSMENT. There is no reason to apply a cat 4 level of PPE when you open the cubicle door but there is a high risk of a shock hazard so voltage rated tools and gloves must be worn. Your company policy will determine PPE levels through the Energised Work Permit process.


The bad thing with wearing "too much" PPE (even leather gloves) is you lose your snese of feeling and perception. With a small wire (#14 and smaller) it can be tough to get it into the terminals you are working on. If there are two wires under the same terminal, without gloves on, you know that you are working with one wire.. With the gloves on, that would be tougher to "feel"...


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