What is Arcflash
An Arc flash hazard is the danger of excessive heat exposure and serious burn injury due to arcing faults in electrical power systems. Electric arc’s produce intense heat, sound blast and pressure waves. They have extremely high temperatures; radiate intense heat, ignite clothes, and cause severe burns that can be fatal.
Causes of Electric Arcs
Dust and impurities on insulating surfaces can provide a path for current, allowing it to flashover and create arc discharge across the surface.
Corrosion of equipment parts can provide impurities on insulating surfaces. Corrosion also weakens the contact between conductor terminals, increasing the contact resistance through oxidation or other corrosive contamination.
Condensation of vapor and water dripping on components can cause tracking on the surface of insulating materials. This can create a flashover to ground and potential escalation to phase to phase arc
Accidental touching: Accidental contact with live exposed parts can initiate arc faults.
Dropping tools: Accidental dropping of tools may cause momentary short circuit, produce sparks and initiate arcs.
Over-voltages across narrow gaps: When air gap between conductors of different phases is very narrow (due to poor workmanship or damage of insulating materials), arcs may strike across during over-voltages.
Insulating Materials -Failure
How we can help
To get the arcflash Hazards down on a site as low as reasonably possible normally requires 7 steps outlined below to lower the risk of personal harm on site.
Step 1 –First thing we do is identify all the problem areas and model the distribution system at your site. This usally means collecting data to see what exactly where and if there is any problems. Its Unlikely to have any problems on the 240V side so its basically to the 3 phase switchboard level.
Step 2 – Next step is to calculate the bolted fault currents and a Coordination study on the tripping times using the predicted arcing currents then use these values to work out the resulting arcflash values using IEEE 1584 and clothing required Using NFPA 70E
Step 3- Produce a plan showing the problem areas consult with the client of areas that could be improved
Step 4 – Fix any easy to fix problems (reduce trip times in relays that are wound up to high
Step 5 – Administrative control, Signage on the switchboards etc telling personal the Dangers limits etc (poor control measure)
Step 6- Engineering/Design control measures BDD specializes in transformer fusing and we can get arcfaults tripping time down to the minimum. Some High Impedance transformers may not go to level 1 or lower however in our experience most can be. (best control measure)
Step 7- PPE – Although this is the worst form of protection it will protect the workers from getting hurt like an old college of mine.
Electricity Entities have some of the biggest problem as far as arcflash goes but to the average consumer (house dwelling) the are well protected via HRC Fuses. Mines, Mills and large industry often have there own Distribution Transformers on site but often neglect to properly protect personal from exposure. To Avoid Litigation if someone gets hurt the following must be considered.
Arcflash/Arcfault in the Australian Standards
AS3000- Arc fault protection must be provided for all switchboards with a nominal supply rated above 800 A and should be considered for all other switchboards.
AS2067 –Electrical installations shall be designed and installed so that personnel are protected as far as practical from arc faults.
There are many options availiable to assist see below