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| Temporary Protective Grounding Equipment https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=3879 |
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| Author: | Jim Phillips (brainfiller) [ Sat Feb 27, 2016 10:30 am ] |
| Post subject: | Temporary Protective Grounding Equipment |
The 2015 Edition of NFPA 70E Article 120.3 addresses the use of temporary protective grounding equipment. This week's question: Have you ever used temporary protective grounding equipment? Yes No |
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| Author: | 3rd Career Electricity [ Mon Feb 29, 2016 7:55 am ] |
| Post subject: | Re: Temporary Protective Grounding Equipment |
This comes up every time we test and clean our substations and switchgear. I work in a large manufacturing plant. Everyone is onboard with temp grounds on the medium voltage side. No one sees the point in placing them on the 480v side. I know 70E does not limit the requirement to medium voltage. To follow the way 120.3 states you would ground every repair. Also, the device pictured in photo 120.5 does not fit well in most of our switchgear. Anyone have a set of ground straps that you would recommend. Thanks |
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| Author: | JKlessig [ Mon Feb 29, 2016 9:20 am ] |
| Post subject: | Re: Temporary Protective Grounding Equipment |
Twice in my life, grounds have protected against inadvertent energization, and potentially at least, saved my life. Both were MV, but that is rather irrelevant to what they did. "3rd", 120.1(6) gives you the leeway you seem to want. 120.3 (in my mind) is only telling you how. The Photo you refer to is not in my copy of the standard, so perhaps you are looking at the handbook? |
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| Author: | PaulEngr [ Mon Feb 29, 2016 9:12 pm ] |
| Post subject: | Re: Temporary Protective Grounding Equipment |
Temporary grounds are always where a potential exists. There are two conditions. The first is stored energy in capacitive fields. Other than outright capacitors, MV shielding and electrostatic precipitators are the most common. High voltage testing such as insulation resistance testing can charge even LV cabling. Once grounded this source is gone. The second source is from induced currents. This is a big issue with overhead lines and again electrostatic precipitators as well as CTs but not many other cases. Another case is where unloaded vacuum breakers impart substantial voltage on the load side. Thus LV is typically not grounded because the conditions are less common. OSHA is clear that grounding is applied where necessary. Many operations just do it everywhere without understanding the purpose, sort of like applying general lockouts incorrectly to electrical or vice versa, or applying permit requirements to all confined spaces. |
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