Arc Flash - Transformer Neutral Reactor
Arc Flash - Transformer Neutral Reactor
(OP)
I have a strange question for those familiar with IEEE 1584 and NFPA 70E. A big boss at a big A&E company recently made the following statement. He said that he recommends neutral reactors on service entrance transformers (480Y/277V) because it will limit the arc flash exposure.
It is true that the netral reactor will limit line-to-ground fault current, but how does this lower the arc flash hazard, when the three-phase bolted fault produces the worstcase fault current and highest incident energy.
Does anyone have any thoughts on this? I rarely see neutral reactors on commercial service entrance transformers, and if this statement was true, I would suspect to see a lot more.
It is true that the netral reactor will limit line-to-ground fault current, but how does this lower the arc flash hazard, when the three-phase bolted fault produces the worstcase fault current and highest incident energy.
Does anyone have any thoughts on this? I rarely see neutral reactors on commercial service entrance transformers, and if this statement was true, I would suspect to see a lot more.






RE: Arc Flash - Transformer Neutral Reactor
RE: Arc Flash - Transformer Neutral Reactor
RE: Arc Flash - Transformer Neutral Reactor
Advantages: Ground-fault currents touch, and step voltages are reduced; overvoltages are smaller compared to ungrounded systems; and intermittent arc voltages are avoided.
Disadvantages: Use of neutral reactance increases neutral voltages during ground faults and requires higher insulation of the transformer neutral and high level of ground-fault current is required (~25 to 60% of 3 phase-fault) to minimize the risk of high transient overvoltage.
I personally do not see the advantage of specifying neutral reactance to lower the risk of arc flash hazard.
RE: Arc Flash - Transformer Neutral Reactor
RE: Arc Flash - Transformer Neutral Reactor
RE: Arc Flash - Transformer Neutral Reactor
Having said that, any reactor large enough to make a difference is going to screw up the use of single phase loads. But this might make sense if all of the loads are phase/phase connected, or are balanced 3-phase.
RE: Arc Flash - Transformer Neutral Reactor
RE: Arc Flash - Transformer Neutral Reactor