11 kV Spur Shutdown with a Consumer DG on the Line: Permit, Earthing and Fall Emergency

Violations: treating an open breaker as 'dead' although a DG can back-feed the spur; no earths at the work site, 2.4 km from the substation where induced and capacitive charge is significant; climbing before proving dead; an aluminium ladder near 11 kV conductors (conductive, never permitted); a frayed safety belt, i.e. no fall protection; and continuing work in drizzle on an unearthed line.

Correct sequence:

1. List every source, including the mill's DG: open the changeover, lock and tag it, and get written confirmation, or physically disconnect the tee-off.
2. Open and isolate the feeder breaker, rack out, lock and tag, close the substation earth switch.
3. At the work site, test all three phases and all conductors with a voltage detector proved on a known live source both before and after the test.
4. Apply portable earths on both sides of the work point, on all three phases, to a driven electrode; connect to earth first, then to the conductor; the earth lead must be rated for the prospective fault current.
5. Only then hand over the permit. If the work party, scope or isolation changes, the permit must be cancelled and reissued.
6. Use a fibreglass ladder or an elevated platform, a double-lanyard full-body harness, helmet and insulating gloves. Stop work in rain.

If the 100 kVA DG at 415 V is connected through the changeover while the 11 kV is isolated, it energises the LT winding of the 63 kVA transformer, which steps the voltage up to about 11 kV and back-feeds the spur. Anyone working on the 'dead' 11 kV line, or touching a conductor at the pole, would receive a fatal shock - and the site earth would then have to carry the generator fault current.

Precautions at the mill:

1. Open the changeover to the 'off' position (not 'auto'), lock it with the utility's lock and tag it; where the changeover is not a reliable break-before-make device, physically disconnect the DG output terminals or links.
2. Prove the LT side of the transformer dead and, where practicable, apply an earth on the LT side at the mill.
3. Obtain a written undertaking from the owner that the DG will not be started until the permit is returned, and record the DG rating, its earthing arrangement and the interlock condition.
4. Check whether other consumers on the spur have DGs or inverters and treat the whole spur as a back-feed risk; size the site earth for the largest source on the section.

1. Do not touch the casualty while he may be in contact with the conductor - the rescuer becomes the second victim. Shout for help and keep bystanders back.
2. Call the control room immediately to isolate the LT line/transformer, and call the ambulance.
3. If isolation will take time, use a dry wooden or bamboo pole or an insulated rod to move the conductor clear, standing on a dry insulating surface and wearing gloves. Never use metal or a wet object.
4. Once he is clear, check response and breathing. If he is not breathing, start CPR at once - 30 compressions to 2 breaths, 100–120 compressions per minute - and continue until medical help arrives. Do not give water and do not delay for other rituals.
5. Control bleeding, keep him warm, and suspect spinal and limb injuries from the fall; do not move him unnecessarily and immobilise the neck if trained.
6. Preserve the scene, record the time and the isolation, report the accident to the control room and to the Electrical Inspector in the prescribed form, cancel the permit and hold an enquiry before work resumes - including testing the belt and ladder that were in use.