zog
Senior Member
- Location
- Charlotte, NC
An electrically safe work condition shall be achieved when verified by performing the following process:
1.Determine all possible sources of electrical supply to the specific equipment. Check applicable up-to-date drawings, diagrams, and identification tags
2.After properly interrupting the load current, open the disconnecting device(s) for each source
3.Where it is possible, visually verify that all blades of the disconnecting devices are fully open or that draw out type circuit breakers are withdrawn to the fully disconnected position
Zogs note: A draw out CB is not designed to be used for isolation unless it is racked out to the disconnected position, just opening the breaker and hangin a lock on it has caused many injuries due to the false sense of security of those not understanding this requirement. Also, the blades of a disconnect must be visually verified open, I have seen many times where 1 phase didnt open. There is a Video about a serious arc flash accident called "the Mark Standifer story" about just that happening.
4.Apply lockout/tagout devices in accordance with a documented and established policy
5.Use an adequately rated voltage detector to test each phase conductor or circuit part to verify they are deenergized. Before and after each test, determine that the voltage detector is operating satisfactorily
Zogs note: Must be rated for the CAT you are working in, usually CAT III for commericial or Industrial. Verify the meter works before and after, commonly called a live-dead-live test.
6.Where the possibility of induced voltages or stored electrical energy exists, ground the phase conductors or circuit parts before touching them. Where it could be reasonably anticipated that the conductors or circuit parts being deenergized could contact other exposed energized conductors or circuit parts, apply ground-connecting devices rated for the available fault duty.
Zogs note: VFD's, MV cables, and PF caps are all common types of stored energy devices that are dangerous and overlooked. The ground need to be rated for the fault current available in the system, "logging chains" and other such devices are not permitted.
Until all these steps are completed the equipment is considered energized, so all the safe work practices and PPE requirements of the NFPA 70E apply until all steps are complete.
(edited to correct CAT rating in item #5)
1.Determine all possible sources of electrical supply to the specific equipment. Check applicable up-to-date drawings, diagrams, and identification tags
2.After properly interrupting the load current, open the disconnecting device(s) for each source
3.Where it is possible, visually verify that all blades of the disconnecting devices are fully open or that draw out type circuit breakers are withdrawn to the fully disconnected position
Zogs note: A draw out CB is not designed to be used for isolation unless it is racked out to the disconnected position, just opening the breaker and hangin a lock on it has caused many injuries due to the false sense of security of those not understanding this requirement. Also, the blades of a disconnect must be visually verified open, I have seen many times where 1 phase didnt open. There is a Video about a serious arc flash accident called "the Mark Standifer story" about just that happening.
4.Apply lockout/tagout devices in accordance with a documented and established policy
5.Use an adequately rated voltage detector to test each phase conductor or circuit part to verify they are deenergized. Before and after each test, determine that the voltage detector is operating satisfactorily
Zogs note: Must be rated for the CAT you are working in, usually CAT III for commericial or Industrial. Verify the meter works before and after, commonly called a live-dead-live test.
6.Where the possibility of induced voltages or stored electrical energy exists, ground the phase conductors or circuit parts before touching them. Where it could be reasonably anticipated that the conductors or circuit parts being deenergized could contact other exposed energized conductors or circuit parts, apply ground-connecting devices rated for the available fault duty.
Zogs note: VFD's, MV cables, and PF caps are all common types of stored energy devices that are dangerous and overlooked. The ground need to be rated for the fault current available in the system, "logging chains" and other such devices are not permitted.
Until all these steps are completed the equipment is considered energized, so all the safe work practices and PPE requirements of the NFPA 70E apply until all steps are complete.
(edited to correct CAT rating in item #5)
