# Substation Batteries



## Andy Robson (Mar 8, 2009)

Substation batteries are required to supply both a running load, and a short duration tripping load. During the tripping load cycle, how low can the battery voltage drop in practice ? And generally how long would it take for a battery charger to cut in to restore the voltage ?


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## frank (Feb 6, 2007)

Andy

In answer to the second part of your query - instantaneous. As for the first part. Can you give more detail.I think you may be talking about a monitoring current but could be something else. Better description please.

Frank


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## sparkie (Apr 2, 2008)

Are you asking how it works in theory or are you involved in servicing these systems?
nice piece about capacity and testing is here


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## Andy Robson (Mar 8, 2009)

Thanks guys.

What I'm trying to obtain is a voltage profile for the battery during the tripping cycle. When the extra tripping load is applied, the voltage will obviously dip (and stay dipped unless the battery charger takes over the demand). But will the profile follow a simple U shape, or will there be a spike at the instant the tripping load is applied - perhaps for tens of miliseconds ? And although I agree that the battery charger will cut in pretty quickly, presumably there will be some delay ? Perhaps a few miliseconds ?

I work in the protection industry and I'm trying to assess the ride-through requirements of the protection PSU. The IEC 'brown-out' standard simply specifies that the protection must withstand a 40% dip for 200ms. The 200ms looks like the expected fault clearance time but I've no idea how relevant the 40% is. We also need to ensure that the PSU will withstand a large but very short dip in the voltage - hence my concerns about the 'switch-on' spike or the battery charger delay.


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## frank (Feb 6, 2007)

Andy

The voltage will spike but you can easily smooth this out.You are at the mercy of the mechanics of your tripping device in regard to trip time . Have you thought of having the trip load voltage applied at all times as a // circuit which is IC monitored.
Anyway. Why are you making such a thing. There are companies out there that will sell you the safety function devices you want.

Frank

Frank


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