3333KVA dry substation question
3333KVA dry substation question
(OP)
We are doing a project here that will have (2) 4,000A 480/277V 3PH 4W dry type indoor substations. The primary voltage is 12,470/7200V 3PH 4W. We are planning an S&C PMH-12 pad mounted switch for the main service switch called "PS-1". The building owner will own this switch. Out local utility distributes in 4W (WYE type configuration).
My question is, would it be appropriate to bring 3 wires (Delta) from the main service switch (PS-1) (leaving the utility Neutral behind at PS-1) and have a Delta-Wye dry type substation transformer connection?
The transformers in the substations would be 2500AA/3333FA KVA VPI-Polyester air cooled. The substation secondary would be 4000A, 100% rated bolted pressure switch with GFI protection at 480/277V 3PH 4W.
Thanks,
Eric
My question is, would it be appropriate to bring 3 wires (Delta) from the main service switch (PS-1) (leaving the utility Neutral behind at PS-1) and have a Delta-Wye dry type substation transformer connection?
The transformers in the substations would be 2500AA/3333FA KVA VPI-Polyester air cooled. The substation secondary would be 4000A, 100% rated bolted pressure switch with GFI protection at 480/277V 3PH 4W.
Thanks,
Eric






RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
Eric
RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
RE: 3333KVA dry substation question
(1) Not quite familer with the term "bolted pressure" anyone care to expand?
(2)David beach; "Can you be assured that the cheap customer will replace all three fuses with a new, matched, set of fuses each time one fuse blows"
I here what you are saying but could the same not be said for breakers? i.e. is there not a finite quantity of fault operations that a breaker can handle before needing to be repalaced or tested. When a breaker trips the electricians I deal with find the problem fix it and then the old breaker goes right back into service...
Regards,
TULUM
RE: 3333KVA dry substation question
I'm not clear enough on the exact internal construction of the BPS to describe it, but it is basically a high amperage fused disconnect that can be tripped by a ground fault unit.
RE: 3333KVA dry substation question
Bolted I think refers to the fact that it is not drawout type, but not sure.
These are some of those popular and normally undestood (in the USA)terms but may or may not make technical sense. (not saying this one does not)
RE: 3333KVA dry substation question
I used a boted pressure switch in a Toshiba JK power cell before... but never knew exactly what the term meant (still a little unsure). The switch was a non-load break (good for 0.4 at 5kV - scary) and was not spring loaded... it was a mechanical marvel that was as slow as schnitzel...
Regards,
TULUM
RE: 3333KVA dry substation question
When one phase of three phase fuse installations blow, one or more of the others may have been exposed to near-melt conditions; not enough to go, but enough to degrade its current capacity. The next time the service goes to peak, or perhaps during the next enerergization inrush event, this fuse pops. The troubleshooters usually then spend time looking for a defect in the system, when the problem was in the protective fuses.
RE: 3333KVA dry substation question
A bolted pressure is a type of knife type disconnect switch.
It may or may not be fast acting.
The mechanism closes the switch blades and then continues farther to turn special threaded bolts to clamp both ends of the switch blade, ensuring a good connection. When the switch is opened, the operating linkage first turns the special bolts to relieve the pressure on the connection and then opens the switch.
The feature described by rbulsara may be incorporated in a bolted pressure switch, but is not the bolted pressure feature.
A non-spring loaded switch as described by TULUM may have the bolted pressure feature.
My experience has been with some that are used unfused (but fusible) for disconnecting 480 volt transformer banks. Mainly for maintainace isolation, but able to open under load. These were manual switches. Very old SquareD. 1600A or 2000A rated current.
respectfully
RE: 3333KVA dry substation question
A bolted pressure siwtch will save intial cost and can be a good choice in a well-maintained facility. Sometimes the increased short circuit capability of the fused BPS makes it a better choice over circuit breaker switchger with current limiting fuses.
RE: 3333KVA dry substation question
However, I don't think I would be impressed by any attempt to automate one. As a manual switch it has excellent current carrying capacity and long life. As an automatic switch, (other than a remote operated isolating switch) I don't think it could match the capabilities of a good breaker. I've opened and closed bolted pressure switches many times under load, but I wouldn't want to open one under a fault.
respectfully