jonesy29847
Member
- Location
- Monroe, Michigan, Monroe
Thanks.
Due diligence
- Thread starter jonesy29847
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zog
Senior Member
- Location
- Charlotte, NC
You are doing arc flash studies for "several manufacturing plants" by hand? That is going to take years, I have to ask, how did you get this contract?
jonesy29847
Member
- Location
- Monroe, Michigan, Monroe
I am direct, and I am just starting to gather the geographical data, so I don't have any idea about time.
In the first plant I have had a look at, uses tray cable from the MDP panel, then transitions to bus-duct, then back to tray cable. This leads me to ponder dealing with impedance, add them together, use worst case, or what.
The thought here is most equipment should be very close in terms of fault current, like a Black and Decker drill, and a Milwaukee drill. This is borne out by the fact that when our suppliers took the time to calculate the rms SCC Ratings are close.
I get the impression that most of the members in this forum are MV and HV specialist.
At the end of the day, we just want to provide proper PPE, we don't want to suit up to plug in a laptop, and we don't want to force heavier protection than needed. If you don't make safety easy, people tend to find short cuts.
In the first plant I have had a look at, uses tray cable from the MDP panel, then transitions to bus-duct, then back to tray cable. This leads me to ponder dealing with impedance, add them together, use worst case, or what.
The thought here is most equipment should be very close in terms of fault current, like a Black and Decker drill, and a Milwaukee drill. This is borne out by the fact that when our suppliers took the time to calculate the rms SCC Ratings are close.
I get the impression that most of the members in this forum are MV and HV specialist.
At the end of the day, we just want to provide proper PPE, we don't want to suit up to plug in a laptop, and we don't want to force heavier protection than needed. If you don't make safety easy, people tend to find short cuts.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Fault current is not dependent on the load, it is a function of the available sources of current and the impedances connecting them.
SCCR ratings from manufacturers deal with their ability to tolerate short circuit fault current. This rating has nothing to do with Arc Flash Incident Energy other than to determine if the equipment is 'overdutied' (applied beyond its limits).
I would guess the vast majority of our forum members spend the majority of their time involved with <600V systems.
wbdvt
Senior Member
- Location
- Rutland, VT, USA
- Occupation
- Electrical Engineer, PE
Reading all the posts, I would like to offer several observations based on over 10 years of electrical studies primarily arc flash and in industrial/commercial environments.
First off, the best way to do them is to have an experienced person performing the studies. There are many nuances to building a model, determining the scenarios needed to run and analyzing the results.
Utilizing a commercial software program (EasyPower, SKM, etc) will provide a number of advantages, such as:
Another critical component that I did not see mentioned is the data collection aspect. This is extremely important to get the information on breakers, fuses, conductors (including if they are in metallic or non-metallic conduit), transformers, motors, variable speed drives, bus duct, etc.
You did need to obtain from the utility the available fault current and X/R.
Some manufacturing facilities are large enough that they own the substation and as such may have utility like voltages. If this is the case, then incident energy in the substation may need to be determined by using ArcPro (OSHA 1910.269 Appendix E)
It may be worth your companies time to obtain some proposals to perform an electrical study at the facilities. Some of smaller firms, like mine, can be quite competitive and reasonably priced due to low overheads.
First off, the best way to do them is to have an experienced person performing the studies. There are many nuances to building a model, determining the scenarios needed to run and analyzing the results.
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
Another critical component that I did not see mentioned is the data collection aspect. This is extremely important to get the information on breakers, fuses, conductors (including if they are in metallic or non-metallic conduit), transformers, motors, variable speed drives, bus duct, etc.
You did need to obtain from the utility the available fault current and X/R.
Some manufacturing facilities are large enough that they own the substation and as such may have utility like voltages. If this is the case, then incident energy in the substation may need to be determined by using ArcPro (OSHA 1910.269 Appendix E)
It may be worth your companies time to obtain some proposals to perform an electrical study at the facilities. Some of smaller firms, like mine, can be quite competitive and reasonably priced due to low overheads.
zog
Senior Member
- Location
- Charlotte, NC
Great post WBDTV! Could not agree more.
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