EWB Engineering wrote:
We have a proposal from a vendor that will deliver a two category system (4&2) that is much less expensive than a full arc flash analysis. How is the assessment for a two category system completed vs a full assessment?
I would like echo others responses based on many years of experience. Is it correct that this vendor is a PPE vendor and not an engineering/safety firm? If a PPE vendor, then they are just selling you PPE without knowing what the incident energy levels are in your facility. This is an easy way to make a sale as it looks like they are doing you a favor by reducing levels. If you do an actual study, you may find that the incident energy levels are low for the equipment that is typically worked on (i.e. not the main switchboard but machine disconnect switches). You may only need actual AR PPE in limited areas.
I would spend the PPE money getting a actual study done. An actual study done properly has huge benefits.
Utilizing a commercial software program (EasyPower, SKM, etc) will provide a number of advantages, such as:
ability to easily run multiple scenarios and compare results for worst case scenario
ability to change protective device settings, particularly instantaneous settings on circuit breakers, to see if the incident energy can be reduced.
ability to change fuse types to see if the incident energy can be reduced. For example replacing a 400A Class RK5 fuse with a 400A A6D fuse.
ability to create one line diagrams as many facilities do not have updated drawings
ability to perform a coordination study at the same time and generate Time Current Curves
ability to perform a short circuit analysis and identify any over dutied equipment
ability to model the utility protective device to determine incident energy at the first connected device on transformer secondary side.
ability to incorporate changes to the facility to generate a new arc flash report
All this will enhance the safety of your facility.