Medium voltage safety before handling.

De-energised is a claim, not a condition

Cable is de-energised when it has been isolated, locked out and proved dead at the point of work. A cable disconnected at one end may still be connected at the other, may still be backfed from a generator, or may be part of a ring that was never opened. The only statement worth trusting is the one made by the person who proved it.

If the cable came out of a plant or a substation, the removal should have run under a switching procedure and there should be a record of it. Ask for that record. A reel with no history is treated as possibly energised until somebody qualified says otherwise, and that caution is not a formality to be talked past on a loading day.

Ask the question before the reel is touched, not after it is loaded. Who isolated it, when, and what proved it dead. If the answer is that somebody pulled the plugs and it has been sitting since, the reel is not ready to move and the visit ends there. That is a short conversation and a cheap one.

Paperwork is part of the material. A reel with a switching record and a tag is easier to review and safer to collect than one without.

Discharge and ground before anything touches it

Shielded cable stores charge in the capacitance between conductor and shield. After isolation, the conductor is discharged to ground and then grounded, using the site procedure and the site equipment, before ends are handled or the cable is cut. One discharge is not always enough on a long length, because the charge can recover within minutes of the first contact.

Grounding is what keeps it safe while work continues. A cable that has been discharged and left floating can pick up charge again from induced voltage in a shared tray, from a storm overhead, or from contact with another conductor in the same pull. Treat an ungrounded MV cable as live until it has been proven dead again.

Test equipment matters as much as procedure. A proving unit, a suitable detector and a set of grounds are not things to borrow at the last minute from a truck that may not carry them. Where the site supplies the equipment and the trained people to use it, use theirs. Improvised grounding is how a good job goes wrong.

Damaged jackets and exposed semicon

MV cable is built in layers, and the layers are what make it safe to be near. A jacket cut through exposes the metallic shield. A shield torn back exposes the insulation shield, the semi-conductive layer that grades electrical stress at the end of a cable. Both are defects, and both change how the reel is handled and how the lot is graded.

An exposed semicon concentrates stress if the cable is ever energised again, which is why terminations are engineered rather than improvised on site. For handling, the concerns are cuts, penetration by nails or staples through a coil, and crushed sections where the insulation may have been deformed underneath a jacket that still looks intact from the outside.

• Jacket cuts exposing the metallic shield
• Semicon torn back or left ragged at a cut end
• Deep gouges, crush marks and flattened sections
• Water inside the shield, showing as corrosion or staining
• Broken reel flanges with fasteners into the cable

On the yard, before the reel moves

Plan the move before touching the cable. A full reel of 15 kV feeder is heavy, and a reel that shifts on a forklift can crush a foot or roll off a truck bed. Check the flanges and the lagging, confirm the reel will not rotate on its tread, and use equipment rated for the load rather than the nearest thing with wheels and a willing operator.

Keep the ends out of reach and out of puddles while the reel is staged. Do not cut an MV cable to see what is inside it, and do not run a knife along a jacket to read the print. If a cable has to be cut to fit a truck, that decision belongs to the buyer and to the site, not to whoever happens to be holding the saw.

• Whether the switching record and proof of isolation exist
• What equipment can lift the reel and hold it
• Where the reel will sit, and whether that ground floods
• Who on site is qualified to handle MV cable

If those four answers are not available, the collection waits. That is a normal outcome for medium voltage cable, and it is the safer course.