djohns6 said:
What the heck is " high current density " ? Is that the same as " Available fault current " , or is the station just operating at near capacity ?
I was wondering the same thing....:grin:
I think he meant that the station had all circuits loaded to near it's maximum allowable capacity....with no reserve margin. A common POCO (POwer COmpany) practice, especially with distribution transformers (A lot of which operate at over 120% of capacity for several hours a day.)
As a footnote, I used to work at an amusement park here in So Cal. Thier 12kv metalclad switchgear for the entire park was located in the service yard for our department. When they added the big water attraction to the park I asked the EE on site if the gear had the capacity to handle the extra load. He said it would be loaded to about 98% of capacity,
calculated.
Obviously it was bad practice to load HV gear that heavily without leaving a buffer of capacity. (Another EE told me that "industry standard" is to try not to load above 75-85% cont. duty).
Six months later I watched on the news as the switchgear exploded into flames and that EE and the park's engineering head tried to shoo the cameras away.
The cause of the explosion? A momentary sag from the POCO caused all the load in the park to drop then abruptly come back on, all at the same time. The inrush of all the transformers and ride motors, etc. overstressed the gear.
Can we say oops?
