ATSman
ATSman
- Location
- San Francisco Bay Area
- Occupation
- Electrical Engineer/ Electrical Testing & Controls
There are many stories out there about Bus Duct (Busway) failures. This is just one of them.
This occurred yesterday at one of our customer's sites. Someone walking by the building saw smoke coming from an underground vault. The FD was called, they came, looked around and called in the POCO. The lineman came, he looked around and checked the primary fuses on the padmount (12KV - 480V, 1500KVA) above the vault feeding the bldg. He replaces the 3 fuses, turns on the primary switch with his hot stick... then BOOM!!!!!!!
By this time all bldg load had switched over to their emer gen.
Turns out the vault had POCO switches that fed loads from other customers and the engineering/ transformer/ bus repair/ engineering could not be started until the MV is LOTO and the vault water pumped out. Bldg on gen for how many weeks?
A side note to this event: This transformer had the same fuses blow 5 years ago and the transformer was replaced.
By the looks of this pic it appears that this failure was a result of loose connections, water intrusion that produced heat and the degradation of insulation over a long period of time and finally developed into a phase to phase fault. Did this problem exist back then and was mis-diagnosed by the POCO? No inspection or meggering was done at that time. The system voltage was measured and found stable. Question: Can this problem exist for 5 yrs before showing it's ugly face?
Any comments?
This occurred yesterday at one of our customer's sites. Someone walking by the building saw smoke coming from an underground vault. The FD was called, they came, looked around and called in the POCO. The lineman came, he looked around and checked the primary fuses on the padmount (12KV - 480V, 1500KVA) above the vault feeding the bldg. He replaces the 3 fuses, turns on the primary switch with his hot stick... then BOOM!!!!!!!
By this time all bldg load had switched over to their emer gen.
Turns out the vault had POCO switches that fed loads from other customers and the engineering/ transformer/ bus repair/ engineering could not be started until the MV is LOTO and the vault water pumped out. Bldg on gen for how many weeks?
A side note to this event: This transformer had the same fuses blow 5 years ago and the transformer was replaced.
By the looks of this pic it appears that this failure was a result of loose connections, water intrusion that produced heat and the degradation of insulation over a long period of time and finally developed into a phase to phase fault. Did this problem exist back then and was mis-diagnosed by the POCO? No inspection or meggering was done at that time. The system voltage was measured and found stable. Question: Can this problem exist for 5 yrs before showing it's ugly face?
Any comments?