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 Post subject: Power Logger Install
PostPosted: Wed Feb 05, 2014 6:04 pm 

Joined: Tue Feb 17, 2009 11:04 am
Posts: 37
What is the most efficient and safest procedure to utilize, when you install a power logger at a Motor Control Center? In this scenario, the logger cannot be installed downstream of the MCC. Thanks for any help.


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PostPosted: Thu Feb 06, 2014 2:22 pm 
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Location: Rutland, VT
So you are installing the logger on the conductors coming into the MCC. De-energize and do the work dead. That is the safest way....lock out/tag out, verify de-energized and do the work....wear proper PPE for LOTO and testing dead.
Have you done an arc flash hazard analysis?

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PostPosted: Mon Feb 10, 2014 6:04 am 

Joined: Tue Feb 17, 2009 11:04 am
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wbd wrote:
So you are installing the logger on the conductors coming into the MCC. De-energize and do the work dead. That is the safest way....lock out/tag out, verify de-energized and do the work....wear proper PPE for LOTO and testing dead.
Have you done an arc flash hazard analysis?

We are outside contractors, and usually there has been no arc flash analysis done on the equipment. The logger is usually installed on the load side terminals of a starter in a bucket.


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PostPosted: Mon Feb 10, 2014 11:40 am 
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Working dead is hands down the safest approach.

If you absolutely must work live then the best approach is to have an arc flash study done. The calculated success rate with IEEE 1584 is 95% of the time, any injuries from an arc flash will be less than 2nd degree. So far no cases that I'm aware of have happened where IEEE 1584 success rate was less than 100%.

If no arc flash study then your only alternative is either to use the tables (so far one study of admittedly only about 30 "tests") showed about a 50% success rate using the tables in 70E, if an arc flash occurs.

Or do nothing. Note that OSHA has fined at least one major manufacturer for taking the "do nothing" aproach.


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PostPosted: Mon Mar 03, 2014 9:33 am 

Joined: Tue Dec 10, 2013 11:20 am
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I recommend always doing this work de-energized. I worked for a testing company several years ago, we had a worker short out a split core CT to the case of the MCC. As a result it caused an arc flash event. Due to improper maintenance and testing on the equipment, the main breaker never tripped, the feeder breaker never tripped, and the main to the substation didn't trip until the long time took it out after 1 minute. The MCC burned the entire time and eventually all the copper bus, starters, and breakers completely melted.

Too dangerous a job to just trust your PPE, always de-energize!


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PostPosted: Mon Mar 03, 2014 3:18 pm 
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To that I would say, OSHA case #201859295, dated 1/29/2008 with switchgear, they were actually trying to de-energize when an arc flash occurred requiring hospitalization of 3 workers due to improper use of a meter on the line side where it initiated an arc flash.

In case #202554218, dated 9/28/2011, the activity was inserting/removing a meter in a meter socket at which point a flashover occurred resulting in a minor injury.

In case #200784999, dated 5/2/2010, the activity was operating a medium voltage load break switch to de-energize and it flashed over. 3 injuries requiring hospitalization.

In case #201186061, dated 7/18/2011, again switching was pretty much all that the investigation uncovered. Voltage was not mentioned. Minor injury this time.

Although working while de-energized sounds like the right thing to do and is so simple to say that it gets repeated over and over again, remember that the act of actually de-energizing in order to work while de-enerigized in itself requires a substantial amount of risk. There is little to no risk involved with de-energizing IF the equipment is properly designed, installed, and maintained, and if proper precautions are taken during the de-energizing activity. In some cases such as some work on 120 V controls being used in higher voltage (480 V typically) gear, de-energizing the entire compartment can entail a much greater risk. This is where the concept of greater risks can come into play.


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 Post subject: Re: Power Logger Install
PostPosted: Tue Dec 23, 2014 6:46 am 

Joined: Mon Jun 09, 2014 9:19 am
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My recommendation would be to always install it de-energized! I was involved in a very dangerous arc flash event several years ago that could have turned out very bad. We were disconnecting a data logger that had been installed for a month or so to diagnose a power quality issue at a plant. We had used 3000A split core CT's in a 480 switchgear with 2000A buss. When George took the CT off he lost his balance the CT fell against the frame of the cabinet and was making contact with the buss. The initial arc only lasted for a brief period of time and threw George out of the gear and onto the floor. The problem was that nothing cleared the fault and it continued to grow. No breaker tripped, at the equipment or in the substation that fed the system. The fire ball grew for over 2 minutes and the gear completely melted down until one of the plants maintenance personel could get to the substation and trip the main for the plant.
During our investigation we found that the plant had not performed any maintenance to the equipment for several years due to budget cuts (big surprise!). There had not been an Arc Flash analysis done so our staff were all working in their HRC 4 PPE.
Now with the company I work for, when we need to use our power quality testing equipment, we de-energize when we install and uninstall on the equipment. I have made that the policy across the company and do not get any resistance from our technicians. It is inconvenient at times, but 70E says that is not justification to work it energized!


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