Arc Flash Labels for Substation Equipment (115kV)

[ish1284]

It is my understanding that arc-flash labels are not typically applied for substation equipment at transmission level voltages because they're out of the range of IEEE1584.

While I know Lee's method can be used to calculate arc-flash incident energy for voltages out of this range, it makes sense to me to not typically apply labels because who really wants to be working on high voltage (i.e. 115kV) substation equipment (think substation transformer, SF-6 breaker, or MOAB) while it's energized?

Does anyone have differing experiences or opinions?

 

[wbdvt]

In the US at this voltage and equipment, you are under OSHA 1920.269 regulations which required an arc flash assessment done by March 2015. Appendix E Table 3 lists reasonable incident energy calculation methods acceptable to OSHA. For voltages greater than 15kV, ArcPro is the only acceptable method.

In the forward to the 1910.269, OSHA discusses labels. OSHA does not believe that providing labels on transmission and distribution installations is feasible or effective. They believe other measures are more effective such as pre-job briefings before the employee arrives at the substation.

As far as working at 115kV, when opening a GOAB to isolate a breaker or transformer, the breaker may be open but switch is still energized. Also, many utilities will do live line work at 115kV.

 

[Bugman1400]

Not sure AF applies to HV. Not sure how it could. You'd never be able to even walk in a suit built for that level of IE. Obvious ways to mitigate the risk are to use remote switching via MODs.

 

[mbrooke]

My understanding is that faults on open air bus bar above workers presents a limited hazard due to everything being out in the open.


Distribution is often 12,500 amps and under.

Transmission can go up to 63,000; but its usually cleared in 4 cycles provided communications assisted tripping is in place and no BF failure.

 

[wbdvt]

Not sure AF applies to HV. Not sure how it could. You'd never be able to even walk in a suit built for that level of IE. Obvious ways to mitigate the risk are to use remote switching via MODs.

It most certainly does, see OSHA 1910.269. Granted at those voltages the spacing is such that it usually considered a line to ground arc fault as it will not usually go to a 3 phase fault. That is why OSHA has ArcPro listed as the preferred analysis method at voltages greater than 15kV and the input is line to ground fault current and clearing time.

At the distances worked, one is usually outside of the minimum approach distance working with hotsticks, so the incident energy level is typically low. It is a fallacy that the incident energy is very high at high voltages at working distances and that it is a single line to ground fault not three phase. Typically an arc flash is way, way worst at 460V than at 115kV.

 

[zog]

It most certainly does, see OSHA 1910.269. Granted at those voltages the spacing is such that it usually considered a line to ground arc fault as it will not usually go to a 3 phase fault. That is why OSHA has ArcPro listed as the preferred analysis method at voltages greater than 15kV and the input is line to ground fault current and clearing time.

At the distances worked, one is usually outside of the minimum approach distance working with hotsticks, so the incident energy level is typically low. It is a fallacy that the incident energy is very high at high voltages at working distances and that it is a single line to ground fault not three phase. Typically an arc flash is way, way worst at 460V than at 115kV.

Not to mention open air vs in a box

 

[mbrooke]

It most certainly does, see OSHA 1910.269. Granted at those voltages the spacing is such that it usually considered a line to ground arc fault as it will not usually go to a 3 phase fault. That is why OSHA has ArcPro listed as the preferred analysis method at voltages greater than 15kV and the input is line to ground fault current and clearing time.

At the distances worked, one is usually outside of the minimum approach distance working with hotsticks, so the incident energy level is typically low. It is a fallacy that the incident energy is very high at high voltages at working distances and that it is a single line to ground fault not three phase. Typically an arc flash is way, way worst at 460V than at 115kV.

Not to mention open air vs in a box

^^^ These two :happyyes::thumbsup:

 

[Bugman1400]

It most certainly does, see OSHA 1910.269. Granted at those voltages the spacing is such that it usually considered a line to ground arc fault as it will not usually go to a 3 phase fault. That is why OSHA has ArcPro listed as the preferred analysis method at voltages greater than 15kV and the input is line to ground fault current and clearing time.

At the distances worked, one is usually outside of the minimum approach distance working with hotsticks, so the incident energy level is typically low. It is a fallacy that the incident energy is very high at high voltages at working distances and that it is a single line to ground fault not three phase. Typically an arc flash is way, way worst at 460V than at 115kV.

Its not uncommon to have ground faults on a HV system that turn into 3PH due to air ionization in just a few cycles. I am unfamiliar with ARCPRO but, am surprised OSHA would make companies purchase that specific software to determine the IE for the AF labels to put on HV equipment. I guess I just haven't seen AF labels at any subs that I've been to. I've seen them on the dist panels in the control house or MV equipment in the yard but not on the transmission side. Would like to see a photo or a printed label of what others have seen at the HV level. Perhaps I am just missing the obvious.....wouldn't be the first time.

 

[wbdvt]

OSHA in the Preamble to 1910.269 has a discussion on labels on T&D equipment. They are not in favor of labels as they believe that the information on the arc flash hazard is better communicated by other means such as Tailboard briefs before heading to the jobsite. This way the employees arrive at the jobsite with the correct PPE for the hazard.

A lot of people were surprised that OSHA referenced a specific commercial product. See Table 3 in Appendix E to 1910.269.