Wrong Voltage - When Transformers Replaced at a College (1-27-2K)
Dear Mike: Here's an unbelievable but true story about how each person in an electrical installation team MUST take responsibility to CHECK IT OUT and STOP WORK if things don't add up.
Our campus was built in two major increments;
1947, a 120/208v distribution system for our "shop area"
1969, a 480/277v distribution system for our "new campus buildings"
The new campus ushered in primary metering at 12.47kv, with dual high voltage feeders servicing all campus buildings. New buildings were tapped to the primary backbone with transformers added as needed. In 1991 two transformers were tested and found to be PCB type and were scheduled to be replaced; both of these were 500kVA. About five others were okay and not replaced.
The campus hired a "design construct" electrical firm to replace the two transformers, connect them, and seal and ship the transformers to a disposal site. The design construct people refused to meet with campus maintenance personnel to tour the site and learn the details of installation; they conducted their own inspection and data gathering. A pattern begins to emerge: one transformer was 12.47kv to 480/277v; the other (for the shops) was 12.47kv to 120/208v.
The "experts" ordered TWO 12.47kv to 480/277v 500kva transformers (delivery time about 3 months)! A two-day campus shutdown was scheduled, old transformers removed & sealed, new ones installed, system fired up, and the electricians drove away WITHOUT EVEN CHECKING OUTPUT VOLTAGE ON THE SWITCHGEAR!
I drove by campus an hour after power was to be back on, and noticed that not all time clocks had been reset, so I stopped by my building (electrical shop) to fix the night-lights. The first light switch inside the building literally exploded when I turned it on (but true to UL testing contained the arc within itself); I thought for about 3-5 seconds and said, "They couldn't have!" I grabbed my car flashlight and went to the nearest incandescent light which lasted 2 seconds before destroying itself; very worried, I got my tester from the car (always carry it around), and sure enough, every duplex outlet was showing 277 volts!
The night-light timers didn't need to be reset, they had burned out! A 500kva 120/208v transformer had
been replaced by a 500 kVA 480/277v one AND NOBODY CHECKED! I contacted security, the campus head,
the maintenance dept head, and got that transformer shut down within the hour. Fortunately, we have
a policy of disconnecting all computers and sensitive devices when scheduled outages are planned.
We borrowed a transformer from the local utility for a few months until the new one came in, and SEVEN
inspectors watched the electricians install the new one. The total bill for damages was around $80,000,
fortunately, no one was seriously injured. My nerves were restored by a couple of shots of Crown Royal when I got home!
The moral of the story? Before doing any work on an electrical system, first follow these three rules:
1) Check the nameplates!
2) CHECK the nameplates!
3) CHECK THE NAMEPLATES!
All people who were "responsible" in some way for this dangerous situation have refused to talk about it.........and in my view that's part of the problem.