110 VDC PSU capable of 100 AMP for 1 second repetitive. 1

[k1y9l8e7]

Hi,

I'm looking for information on where i can get a 110VDC PSU that will deliver 100A for a second repetitivley (as required during testing/commissioning?) I am currently pre-commissioning some Hawker Siddeley Switchgear (HSS), the DC Lighning range with NDC 6 circuit breakers, the literature states the closing actuator in the Breakers can demand 100A for up to one second. We have some portable 110VDC batteries on site that arn't really up to the challenge of closing these breakers as much as is required during testing. We are not permitted to use the sub-station UPS batteries for testing/commissioning. These batteries have been used for LV switchgear control circuits and some other HV switchgear control circuits no problem but they are stuggling with these NDC 6 breakers.

After talks with HSS i found the equipment they use but this is £8-9000, i was hoping someone was aware of a cheaper alternative or any purpose designed equipment.

My calcs show a 15kW PSU @ 110V should be able to give 136Amps ish. Please correct me if i am wrong and any suggestions on where i can get this equipmentare greatly appreciated.

Kyle

 

[ScottyUK]

Frankly your cheapest option is probably to replace the tripping battery you're using or buy some cheap car batteries if it's a one-off job.

Nine 12V lead-acid blocs of (say) 20AH or above should be able handle this duty without significant sag. A 110V charger would be able to be trimmed to provide the correct charging voltage. Your charger needn't be especially large - 5A or so output would be more than sufficient to trickle charge the cells.


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If we learn from our mistakes I'm getting a great education!

 

[k1y9l8e7]

Thanks Scotty UK, we were thinking this would work but unfortunatley we are rotating about 3 substations, 2 weeks in each repeating, there are also COSHH restrictions in place regarding open batteries. At the moment we have a set up of 9 12V 7AH, two sets in parrallel, these are relativley portable and we were hoping to obtain something similarly portable. Is this even possible do you think as you mentioned 20AH would probably be required?

PS. these batteries are brand new and worked for a couple of days being trickle charged as you mentioned over-night but they seem to be dying quickly!

 

[itsmoked]

You say 110V 100A for one second. And then how long do you have between those pulses?


With respect to gel cells. They require serious attention to detail or their imminent failure is guaranteed. You must recharge them immediately,(if not sooner), after discharge or they shed permanent capacity rapidly. Like in hours.

Trickle charging is not what cyclically used gel cells need.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[k1y9l8e7]

itsmoked, thanks for this, worse case is usually a few seconds between the pulses a few times and then a minute or so rest while looking at/highlighting the drawing etc. they get the most stick during the functional checking of the control circuit, open/close protection trips etc. Also these are lead acid batteries we are currently using.


Something else i should have said originally is with this being a DC board there are two breakers, one for the positive and one for the negative, per circuit (and per close command). The neg. follows the pos. and the pos is closing almost every time and the neg. is not (although it was originally so is not a fault in the closing circuit). This logic is what has lead me to assume it is the batteries that are struggling.

Thanks you for your input, i wonder if its going to have to be some heavier duty batteries and just lump them around?

 

[davidbeach]

Why would you operate the breakers every time? Why not do an initial trip/close test; open the test switches to disconnect the breakers; connect in breaker simulators; perform all the rest of the commissioning; remove the breaker simulators; close the test switches; and make one more trip/close test? This will greatly minimize the DC requirements, greatly minimize the wear and tear on the breakers, and generally make the whole process easier on the equipment and people involved.

 

[k1y9l8e7]

thanks davidbeach for this suggestion, unfortunatley there is a strict proceedure in place for the testing of these boards generated by the customer. The breakers have several auxillaies that require testing to SCADA and then the breakers also contain mechanical and electrical interlocks with the closing/opening circuits and the control circuit umbilicle requires to be conected to privide one part of the Trip Circuit Supervision, again interlocked with the control circuit. Also during customer witness testing etc. they will want to see the board functioned complete with breakers.

Please can you explain what you meant by breaker simulators and what the Test Switches are you mentioned? having trouble thinking what they are?

Thanks, kyle

 

[davidbeach]

Test Switch - see

http://www.abb.com/product/db0003db004281/c12573e70033041985256ad20066cda8.aspx

for one of many examples.

Breaker simulator is a box with inputs/outputs to simulate the operations of a breaker. At a minimum it will have a trip coil, a close coil, a 52a contact and a 52b contact. Can have multiple aux contacts, breaker speed times, other features. Easier to program a simulator to trip slow or stick than to have the real breaker be slow or stick.

 

[k1y9l8e7]

Thanks will look look into this, not sure it will be an option but maybe for future works, much appreciated.

 

[DTR2011]

Programma makes a B10-E for this purpose. Vanguard makes something similar.

Ever think about a step down transformer and a 100A full wave bridge rectifier, fed by a variac? Thats how it's done sometimes if batteries are unavailable and DC is required. Care should be used if you have sensitive protection, but if its just charging breakers, many have universal charging motors.

 

[itsmoked]

If you had a really low duty cycle I was going to suggest capacitors or capacitor augmentation since they could be much lighter. But it sounds like the duty cycle could be too high.

Capacitors would help with any battery bank used in pulse applications. It allows the chemistry to 'get up to speed', over some time period rather than instantly.

Back to batteries, can you build a small trailer and conveniently tow it to a test site, or are they inside buildings or otherwise spatially constrained?

For small batteries, small flooded batteries are far(vastly) more robust. Small motorcycle batteries can be very tough. Batteries about the same size as the 8Ahr units you're using would deliver more current in pulse applications than gels.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[k1y9l8e7]

Smallgreek, thanks for this, we have a Programma B10-E with us on site but the DC output currnet is <10A @ 110VDC so is a no go for this aplication. Unfortunatley as you mentioned we have Protection Relays and sensitive Breaker Control Modules on the same 110VDC supply circuit in this board and so the rectifier option is out too, thanks though.

itsmoked, we are inside substations and upstairs to make matters worse, i will look into the capacitor theory but the motorcycle batteries were a good call as it is the only thing a can think is small and heavy duty, though i don't have any experience with batteries to be honest.

Can anyone help with this one, we originally had 8 cells @ 12V 7AH (2 sets in parralel) and changed this to 9 cells @ 12V 7AH (2 sets on parralel), this gave us 118V when brand new and worked a treat for the first day and were about 107V by the end of that day (still working). The Charger output is 110V and therefore after a full nights charge the cells only ever reach 110V, have I damaged/changed the charge of the cells in any way by doing this, i was thinking even at 110V 9 cells would be better than 8? Have i made a fundamental error?

 

[ScottyUK]

You have 54 2V cells so you need to be charging at about 124V or so - you can probably tweak the output to accommodate this. Check the charge voltage for your specific battery, but 13.8V is typical for a 12V bloc. The switchgear will be designed for the higher voltage because all nominal 110V batteries float at a higher voltage. Charging at exactly 110V will not get much charge into the battery, which probably explains the poor response you're getting: the battery is well discharged.



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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

Scotty has stated it well.

You are destroying the batteries as you are certainly not quickly recharging them to a fully charged state with less than 124V and possibly you would need more than that.

Can you tell us what exact battery you are using?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[k1y9l8e7]

ScottyUk and itsmoked thanks, this would explain a lot.
The exact battery is "YUASA NP7 - 12, 12V, 7AH, valve regulated, lead acid battery", data sheet attached.

Just to let you know i have changed the set up (again) in a bid to share the load on the batteries. I have made up 3 banks in parralel with each bank containing 8 of the above cells in series (so 24 cells in all), i have not had chance to try these yet, i was thinking it may provide more of a buffer (for want of the correct term) and share the stress across more cells??

The charger output is just under 110V as mentioned previous and I did not know that a 12V cells optimum charging voltage was 13.8 otherwise i would not have changed from 8 cells to 9. The battery data sheet attached shows this ( i should have looked at this ages ago) on the last page bottom left at about 20 degrees it is between about 13.4 and 14.8V. Now that I have an 8 cell set up per bank again and a 110V charger, 110/8 = 13.75, do you think that may be it?

I will be back at site tomorrow so am interested to see if this works now, thanks again, this is helping a lot.

Kyle

 

[k1y9l8e7]

PS i have just realised I should be calling them batteries not cells. I can't seem to see on the data sheet how many cells there are per battery but it does say "charged at 2.275V per cell", so does this mean 6 cells per battery? (6 x 2.275 = 13.65V)

Thanks.

 

[ScottyUK]

Sounds like you are on the right track. Paralleled strings of cells on a common charger are quite normal in UPS applications so no problems there.

Yes, six cells per 12V battery. Each cell is considered as a 2V cell even though under charge its terminal voltage is about 2.25V. That's where the confusion usually arises!

Bear in mind that with 48 cells (8x 6V blocs) your breaker tripping scheme will be running at a lower voltage than normal because most 110V systems contain 54 cells (9x 6V blocs) and float charge at about 124V. That said it should still be within operating tolerances with 48 cells. Does your 110V supply have an adjustment to allow you to trim the output voltage? I'd try to get that ninth 6V bloc in each string so you are testing under the same conditions as it will see in service.


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If we learn from our mistakes I'm getting a great education!

 

[k1y9l8e7]

Scotty UK & itSmoked, we have a working system!!

Found the trim pot you mentioned after ringing the company that made the charger, charger output is now 124VDC. Added the extra battery back in so we now have two strings of 9 x 12V batteries in parallel. Charged them for a few hours and they work a treat. They seem to sit around 118 - 119 VDC, will they ever reach the charger output voltage of 124V? (full charging time is 16 hours i think) not that it matters i suppose just wondering. They have had a bit of stick today and they haven't failed once so I think it's safe to say problem solved!

Thanks again for your help,

Hope I can return the favour one day!

Kyle

 

[itsmoked]

They should get very close to the 124V number given enough time.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Excellent news. Just seen I've managed to describe the 6-cell blocs as 6 volt blocs when they're really 12 volt... ooops! Wonder if anyone else noticed?

Pleased you got it working. From your choice of currency and the hire company you mentioned I guess you're in the UK. If you're up in the north east you can buy me a pint!


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If we learn from our mistakes I'm getting a great education!