on-line emergency lighting

[antonino]

hi
for a local hydroelectric facility, we have supplied several on-line inverters (15kva, 277) for emergency lighting. Four years after the start-up, the real 125V dc load has reached a value greater than the design and the problem is that these inverters are feeded by the 125vdc substation control voltage. Actually, this 125 vdc is splited in two systems(A,B, each one with BC and batteries) with a tie breaker, but the tie breaker can not be closed (if required) at this dc load current level without overloading one of the battery chargers.

After several meetings, the tech comitee have proposed
to change the operation mode of inverters from on-line to off-line in order to reduce the dc current load.

Any suggestions on why this is not best solution. References or standards to support it are appreciated.

By the way, all the lamps are HID.
thanks

 

[waross]

I am surprised that a utility would use the control batteries for emergency lighting in the first place. Suggest dedicated battery banks and chargers for the inverters.
respectfully

 

[itsmoked]

antonino; I am not real clear on your question.

on-line = charger always running the batteries while they run the loads.

off-line = something else runs the loads, batteries are kept charged. If a power failure occurs then a contactor is closed so the batteries can supply the load.

off-line also means the power will 'blink'! You will need something to sense and control the contactor. Bringing it in on PF and dropping it out on return. Will your loads tolerate the blink? Your HIDs certainly won't!!! They will all go out for 15 minutes.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[antonino]

thanks for your replies
Keith:
Sorry it was my fault, I did not give full details.
Each inverter have two static switches, one on the inverter output (always running)and one on the bypass line
(480 vac from a transformer feeding an electromech. voltage regulator).
On-line means loads always supplied from the inverter; on PF transfer to bypass line
Off-line means loads supplied from the emergency line;on PF transfer to inverter output.

waross: very important your comment. do you know of any design practice or specs for this application.

 

[waross]

My thought was that during a power failure would be the last time that you would want an extra load on the station control batteries.
We have some people on this forum who have a better knowledge than I concerning station batteries. Let's hope that one of our friends with first-hand experience in power stations will jump in with some more information, and specific information regarding applicable standards.
respectfully