Just curious. How many utility people use a lower level of PPE than the calculations require? We have pretty hot summers and use the NESC exception of PPE creating an addtional hazard quite often.

We feel heat exhaustion and heat stroke are a more likely hazard than the remote possibilty of an arc flash. Everyone's thoughts?

For the high voltage overhead line work we have found 8 cal clothing to be more than adequate for most all cases. How does yours calculate? I also still believe for the line work portion, contact is still the most prevalent hazard.

For the 208 and 480 work, specifically padmounted or transclosure work, you can certainly have some extremely high IE available. We recommend no live work at this level whenever possible. No doubt that at 90 degree + temps the 20 cal or greater PPE with hard hat, face sheild, and gloves could easily create a greater opportunity for mistakes in a tight work area as well as the health issues you mentioned.

While taking the exception is an option, I would document the experience/reasoning (and the need to work it hot) well and hope for the best.

It is extremely difficult to determine, which is the worst hazard, arc flash or heat exhaustion/heat stroke. My recommendation would be to require all workers to wear a minimum of 8 cals/cm2 with long sleeve shirts and face shields minimum....no matter how hot it is.

Wearing anything else other than Arc Rated clothing is extremely dangerous. When wearing this clothing and an arc flash occurs, their clothing will not burst into flames, it will shred and rip apart, but the clothing will not burn. The worker may receive burns, but it will be less than if they were wearing cotton or polyester blends clothing, and it catches on fire.

Thanks! We work in the desert SW and temperatures are usually above 100 degrees and often reach 115 or more in the summer. Heat exhaustion happens on a regular basis but arc flash is a pretty rare event. So we have to weigh our different hazards.

Yes an arc flash could be horrible but if we wear heavier PPE for that rare event, people will be dropping like flies. 8 cal is the best we can do and that is even questionable in mid summer. For pad mounted trfs and other ground work, we are also leaning towards 8 cal even though the calculated Ei is greater. If someone has the full suit on with the sun beating down, you are just about assured someone will be passing out.

We do try to de-energize when we can. The reduced PPE decisions are made with the input of many people.

Reducing PPE for heat stress

While this is the intent of the NESC 2007 clause, you should always look at the arc flash calcs. Most desert SW systems we have looked at clear instantaneous on the primary side because they are set up very radially. If that is the case, you will likely have very little issue on the primary side.

Another thing safety & engineering departments have to take into consideration is the risk and the hazard. If you are working with a hot stick and/or using a hot stick shield meeting ASTM F 2522 some are reducing PPE. NEVER get out of arc rated fabrics. Another way to raise protection easily is to use an arc rated t-shirt. Several companies sell these now and some are VERY lightweight. Always get one with data when worn underneath your long sleeved outer shirt. Two layers may make only a little difference but many can make protection up to 20 cal/cm2 or more which meets about any primary system.

Hope this helps. There are some layered data systems produced by utilities and shared for free on our website. Additionally many clothing companies have data of their systems and some even have data of their t-shirts with other outer shirts.

You can see the free utility produced data at http://arcwear.com/arctest/arctest.php

If the calculations show that the IE is greater than your normal 8 cal/cm² PPE, you should confirm that the working distance is not too conservative. You may be able to restrict use of higher PPE to glove work and wear the normal PPE for all hotstick work.

When we have done studies for utilities, we have given two values of IE, one with 15" of clearance which matches the NESC MV tables and another with 60" clearance for hotstick use.

Arcflash mitigation to reduce PPE

Reducing the Incident Energy level through optical mitigation of the Arcflash would lower the PPE requirement. There are also many techniques available to help identify and locate ground faults which can lead to Arcflash incidents.