Station Service A.C.
Station Service A.C.
(OP)
I am working on a situation that we haven't had to deal with before. I'm installing a Cap bank across the road of one of our switching station. To get station service power to the cap bank, I want to run Quadruplex cable from the switching station 120 V station service AC box to the Cap Bank AC box. This run is 470' and will be ran in PVC conduit the entire way, with exception to 100' span off of two 45-2 poles. The cap bank in question will have four 20 Amp breakers for the Switcher A.C. (Motor, Light, Heaters), Control Cab (Heaters), Battery Cab (charger, Heaters) and Scada. My question is pertaining to sizing this cable for adequate voltage drop. I received some help from system protection that suggested 3/0 cables w/ 3/0 neutral, which works out to about 8.2% voltage drop, using an on-line voltage calculator. I heard you should never go above 8% for AC motors. So, is this acceptable? If I'm missing anything, how big should I size the Quadruplex if this isn't adequate?
Thank you,
Thank you,






RE: Station Service A.C.
What's the voltage on the cap bank?
In most of the situations I've run into, we hung a little pole mounted transformer for the AC supply rather than deal with long runs of large cable.
old field guy
RE: Station Service A.C.
Bill
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"Why not the best?"
Jimmy Carter
RE: Station Service A.C.
RE: Station Service A.C.
Waross: I can't get a real direct answer from our system protection guy, so I have been assuming full load current at 80 amps. I never considered 480 volt transformers, I'm going to dig around on that this afternoon.
RE: Station Service A.C.
RE: Station Service A.C.
Run a 120/240V circuit and split the loads between both legs.
Use the FLA of each load when calculating circuit current. Not the breaker rating or circuit ampacity.
Run the voltage drop calculation again (beware of on-line calculators).
RE: Station Service A.C.
Thanks all.