The call> deli workers getting bit off meat slicer
initial findings> energized grounding conductor, but not tripping breaker....
the RX> simply unplugging one of the 'suicide adapters' which someone had plugged into a receptacle outlet in the dark, and missed. One prong was in the hot, the other lightly touching the metal receptacle cover (TP anyone ?)
Did you check the EGC impedance? (Sure test, Ecos or similar tester) I see the reason why this happened, objectionable current on the grounding conductors but it also points to a high resistance ground path.
Back in my IBM days I was in a computer room with a raised floor. The customer was complaining that they had a machine people were getting shocked on. I figured out it was served by a surface raceway coming up the wall to a 5-15 that had obvious damage and checked the receptacle. Yup, 120v on the EGC compared to the bonded floor grid. It was a bolted fault in the raceway. The resistance of the EGC was high enough that it did not operate the OC device. You could cook a hot dog on the box under the floor that had the bad connection tho (loose EMT locknut, no green wire ground). If we had been happy just repairing the bolted fault we would have only fixed half the problem.
Customer: "When I unplugged my clothes dryer to move it the plug sparked and all my lights went out"
Finding: The "service" was some surface mount porcelain fuse holders on the porch (yes, outdoors but with a roof over it). The neutral was fused and that fuse was blown.
The dryer had (like they all used to) its neutral bonded directly to the frame of the machine. Some well-intentioned person had attached a ground wire from the frame of the dryer to the cold water pipe feeding the adjacent washer.
This gave the electrical system a path to ground as long as the dryer was plugged in.
Of course, when we first got there my boss (I was a helper at the time) was sure they had to be wrong and was he ever surprised when he pulled the 30 Amp plug out and it drew an arc and the lights went out!
My favorite would have to be the infamous "Every third Computer is fried" issue, where a Commercial Building's Service is derived from a 240/120V 3 Phase 4 Wire Delta system.
One particularly odd head-scratcher was back in 1989, on a new "Ground-Up" project (multi unit Commercial Warehouse complex). Services were 208Y/120V 3 Phase 4 Wire, ranging from 800 Amps to 1200 Amps. Gear consisted of UGPS, Main Disconnect section, with Three or Four Meter Sections attached.
Went to shoot trouble per a Tenant's complaint of very dim Fluorescent lights, and some equipment's power supplies losing smoke.
Issue was Open Common Grounded Conductor (aka "Neutral").
After close to an hour of searching, the problem was not poor make-up in J Boxes or at Outlets - it was at the Meter Sections!
Culprite: "someone" forgot to tighten the Bolts for the Bus Jumpers between the Main Section and the first Meter Section. That "someone" happened to be the guy I was working for at that time.
Found out later that He was a major Pot Head, who also decided to start using Methamphetamine. This, along with keeping His Head inside of His own A$$, may have been the reason for not tightening those Bolts!
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!