IEC 61482-2 Second Edition Just Released!

IEC 61482-2As the International Chair of IEC TC78 Live Working Committee, I am excited to announce the recent publication of the second edition of IEC Standard 61482-2 Live working – Protective clothing against the thermal hazards of an electric arc – Part 2: Requirements.

This revised standard is applicable to protective clothing used in work where there is the risk of exposure to an electric arc hazard.  The document specifies requirements and test methods applicable to materials and garments for protective clothing for electrical workers against the thermal hazards of an electric arc. Continue reading

Non-melting clothing

Our company in the past 2 years has implemented an electrical safety and control of hazardous energy program for employees world-wide. Our daily work-wear clothing minimum requirement is non-melting clothing, except in US and Canada for which our AFHA’s determine minimum PPE requirements. Unfortunately, many countries have yet to recognize arc flash is a real threat to people and arc flash isn’t isolated to just North America. (Good news is they are beginning to wake up!)

As the implementation project manager I have not been able to find non-melting clothing for our Chinese colleagues that can be sourced in China. We can get clothing items from other countries but at a higher costs, shipping delays, etc.

Anyone have any experience in this area or have any suggestions? READ MORE

Behavior of Apparel Fabrics During Convective and Radiant Heating

Personal protective equipment (PPE) recommended for arc flash is not always designed for arc flash exposure. The purpose of this paper is to warn of the dangers posed by using the improper materials in arc flash exposures until standards have caught up on this issue.

The table below shows a representative range of everyday textiles along with some of the measurements of importance in establishing their response towards convective and radiant heating[1]:

Properties of Fabric Table

 

Times to ignition or melting of the 20 fabrics in Table above were reported by Wulff[2], [3] for different incident heat fluxes. The Wulff’s data have been used to develop a methodology by which ignition and melting times may be forecast. A semi-empirical relationship between ignition/melting time and radiative heat flux has been derived[1]:

[NF0] = -1 / NBi * ln(1 – NBi / [qxrad]) + a * [qxrad]^b * (1 – NBi / [qxrad])^-1, Equation 1
where [NF0] is the non-dimensional destruction time of the fabric (that is, time to ignition or melting) and is given by:

[NF0] = (k/l) * t / (pl * c), Equation 2

 

where:

(k/l) – average thermal conductance, W / (m^2 * C);
t – ignition/melting time, sec;
pl – mass/unit area, kg / m^2;
c – average specific heat, W * sec / (kg * C).

NBi is the Biot number which is defined as the ratio of the average convective heat transfer coefficient of the fabric to the average thermal conductance of the fabric. It is obtained experimentally for each fabric.

The non-dimensional radiative heat flux [qxrad] is given by:

[qxrad] = ads * W0 / (k/l) / (Tim – T0), Equation 3 READ MORE

Racking in medium voltage breakers – does this exist?

The question of the week on racking in medium voltage breakers got me thinking about this video: https://www.youtube.com/watch?v=rdQR7-Ap6YQ

and what else could be done to prevent it from happening again. Yes, I know the guy was wearing insufficient PPE and should have had the door closed. I also know that in our newer gear where I work we have remote remote racking operators, fiber optic flash detection and tripping and the gear is designed differently to contain or re-direct an arcing fault.

All that said, I expect events like this mostly occur while racking the breakers in and out. What if there was a quick connect gas hose port in each cubicle with a nozzle inside to flood the stabs with SF6 or some other gas while racking? If there were a fault the gas should help knock it way down I would think and help to save the equipment even if you were using remote racking.

Maybe it already exists and I’m not aware or maybe it’s not feasible due to not being enclosed would keep you from achieving a high enough concentration of gas, or the EPA wouldn’t like it, or it would be too expensive. It is just a thought I had if there are any manufacturers reading this.

I also thought about compressed bottled gasses inside the gear with quick acting firing could possible serve a similar function but those would likely never fire fast enough and never be tested or maintained. READ MORE.

PPE Selection when Interacting with non-labeled Equipment

Hi All, To put my question in context, I train Industrial Maintenance and Construction Electricians at a Community College. Some of the students are new to the field and are receiving training to gain employment. Many of the students are already employed and are taking classes to enhance their skill set. Many of these folks are involved with service work that takes them to a variety of locations from 7-11s to industrial sites. Where I am troubled is how to advise them about what PPE to wear in READ MORE