# Importance of CAT ratings



## RIVETER (Sep 26, 2009)

Zog said:


> I have seen so many people say that they are safe and have so many years experience that they think they are qualified, well so did this guy. This artice covers the importance of CAT ratings and updating your companies safety training. The victim here was an experienced IBEW electrician that believed he was safe.
> 
> http://ecmweb.com/ops_maintenance/defective-test-equipment-20100101/


That was sad, but great information. Has anyone figured out what the supposedly, transient voltage was? If it was there on the center lug in the first place and was still there when he went to check it again it seems that it would be something that was more than transient.
Zog, that is great information. A lot of younger tradesmen may not really understand the fact that a HIGH ENERGY source has more to do with things than just VOLTAGE, and your test equipment must be able to react swiftly enough.


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## Grimlock (Aug 4, 2009)

I read that article in the ECM I got in the mail. It seemed to me that the meter he used was defective in some way and actually may have cause the problem.


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## electricalperson (Jan 11, 2008)

the clowns i used to work for would use non cat rated meters to test 480v panels located right next to the 480 volt switchgear. i tried to tell them to use a cat 3 or 4 rated meter but they wouldnt listen. they got used meters from people that would test electronic devices and use them on those panels. they all knew more than i did i guess.


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## RIVETER (Sep 26, 2009)

Grimlock said:


> I read that article in the ECM I got in the mail. It seemed to me that the meter he used was defective in some way and actually may have cause the problem.


I may be wrong but the way I intepreted it was that he thought something was wierd about what he had read on the center leg; Then, returning his meter to the center leg, it blew up. The meter was not tested for whatever the abarrent voltage was and did not react quickly enough when an arc was drawn between the meter lead and the center leg. As the arc flash event grew it involved the other two phases as well. Tell us, Zog...what happened?


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## MDShunk (Jan 7, 2007)

Pictures of a Fluke 87III after incidental contact with 5,000 volts. Incidental is what you call it when you don't like to admit you made a mistake.


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## RIVETER (Sep 26, 2009)

MDShunk said:


> Pictures of a Fluke 87 after incidental contact with 5,000 volts. Incidental is what you call it when you don't like to admit you made a mistake.


Wow!!! That's ABERRANT.


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## slickvic277 (Feb 5, 2009)

RIVETER said:


> I may be wrong but the way I intepreted it was that he thought something was wierd about what he had read on the center leg; Then, returning his meter to the center leg, it blew up. The meter was not tested for whatever the abarrent voltage was and did not react quickly enough when an arc was drawn between the meter lead and the center leg. As the arc flash event grew it involved the other two phases as well. Tell us, Zog...what happened?


This was my interpretation as well.


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## RIVETER (Sep 26, 2009)

slickvic277 said:


> This was my interpretation as well.


This really brings ,FRONT AND CENTER, the fact that when we are testing for voltages, we really do not know 100% what that voltage will be. Proper PPE is essential.


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## MDShunk (Jan 7, 2007)

RIVETER said:


> This really brings ,FRONT AND CENTER, the fact that when we are testing for voltages, we really do not know 100% what that voltage will be. Proper PPE is essential.


Particularly when there's a transformer fire up the street. Hindsight's 20/20, but I think I also just learned that if I'm presented with a similar situation, I'll wait until the transformer fire is under control before I troubleshoot someone's gear. Hell, there could have been primary (or something close to it) coming in on that phase.


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## RIVETER (Sep 26, 2009)

MDShunk said:


> Particularly when there's a transformer fire up the street. Hindsight's 20/20, but I think I just learned that if I'm presented with a similar situation, I'll wait until the transformer fire is under control before I troubleshoot someone's gear.


Me too.


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## Mike_586 (Mar 24, 2009)

Zog said:


> I have seen so many people say that they are safe and have so many years experience that they think they are qualified, well so did this guy. This artice covers the importance of CAT ratings and updating your companies safety training. The victim here was an experienced IBEW electrician that believed he was safe.
> 
> http://ecmweb.com/ops_maintenance/defective-test-equipment-20100101/


I have a print out of a picture similar to this in a safety manual that I bring in from time to time when I see guys using older testers. It along with the supporting documentation helps drive the point home.


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## RIVETER (Sep 26, 2009)

Mike_586 said:


> I have a print out of a picture similar to this in a safety manual that I bring in from time to time when I see guys using older testers. It along with the supporting documentation helps drive the point home.


That is a great chart. Most of us older guys probably know what the transient voltage test means, but explain to the newer guys what it means.


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## Zog (Apr 15, 2009)

The IEC 61010 is the new standard for low voltage “test, measurement and control equipment”. The IEC 61010 provides much improved protection against over voltage impulse transients (voltage spikes) and is the basis for:

• ANSI/ISA-S82.01-94 (US)
• CAN C22.2 No. 1010.1-92 (CAN)
• EN61010-1:1993 (EUR)

IEC 61010 defines four locations or categories: 

CAT I - Protected electronic circuits
CAT II - Receptacle outlet circuit; plug-in loads.
CAT III - Distribution wiring, including “mains” bus, feeders and branch circuits; permanently installed loads.
CAT IV - “Origin of installation” Utility level and any outside cable run
The level and energy of voltage impulses is dependent on the location. The closer the location is to the power source, the higher the available fault current, the higher the category.


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## Zog (Apr 15, 2009)

RIVETER said:


> I may be wrong but the way I intepreted it was that he thought something was wierd about what he had read on the center leg; Then, returning his meter to the center leg, it blew up. The meter was not tested for whatever the abarrent voltage was and did not react quickly enough when an arc was drawn between the meter lead and the center leg. As the arc flash event grew it involved the other two phases as well. Tell us, Zog...what happened?


More or less yes. Chances are there were transient voltages on the system, most likely caused by switching over at the scene of the transformer fire. Switching transients can be 5x system voltage and can cause flash overs. Add the transient voltages with him poking around in there with his probes and it is even more likely. 

If a transient causes an flashover, the high current can sustain the arc, producing a plasma breakdown or explosion, which occurs when the surrounding air becomes ionized and conductive. The result is an arc blast.​


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## s.kelly (Mar 20, 2009)

Great initial post and follow up from everyone. Thanks for a great reminder and good discussion.


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