What is Typical with Back-UP DC Wiring?

[Mbrooke]

Is it ever done, or even doable, to have the backup DC system be able to run the spring charge motors and MOABs for the blackout failure of the primary DC system?

What is typically for your utilities regarding the backup DC wiring- do you keep the all back up wiring dedicated to the back up relay or do you run the backup trip coil into the primary relay?

For those that use Primary and Secondary schemes vs Primary and Backup, what is typical in terms wiring and control?

 

[OffTap100]

Can you please explain your " back up DC system" ? Are you referencing something different then your standard station battery system for a sub?
A bit confused....

 

[Mbrooke]

Basically you have two battery banks. One is the primary battery bank which gives power to the primary relays, primary trip coils, MOABs, spring charge mechanisms, RTUs, HMIs, ect.


Battery bank two is a backup bank which feeds power to the second set of relays and a second set of breaker trip coils.

The idea is if that bank one fails, the second bank will still be able to trip breakers should a fault occur on the system.

 

[Palletjack]

Why would bank one fail?
If bank one failed, what’s stopping bank two from failing? Generally speaking they are maintained the same way at the same time. We have a spare bank at a station. It was purchased with a transformer. The idea was to leave them in there “just in case”. Hasn’t been used in 15 years. Maintained the same as station batteries

BTW, how much is a battery bank and a cabinet? 120VDC or 48 VDC.

Monthly inspections and SCADA generally catch issues before they become problems.

 

[Mbrooke]

The worry is a short circuit- hence why the batteries, panelboard main and branch circuits have OCPDs. An unexpected fault or overheated connection could shut down an entire bank.

The theory is that it is unlikely that both will suffer the same contingency at the exact same time if kept reasonably apart; unless of course something like a serious control house fire or tornado touched down whereby total lack of DC power would be a least concern.

Also sometimes NERC or NPCC standards require it.

The to be built drawings aren't giving a price list, but the bank is 125 volts DC.