Simple manual transfer switch at Medium Voltage

[vanskat]

I have been trying to locate a 13.8kV on-load (Make before break) transfer switch for the last two days that would allow me to swap feeds from two reclosers being fed from the same transformer. The problem is that one is a dedicated feed and the other shared with some other folks.

However, all found so far is a bit of overkill for this simple application. Anyone has any suggestion?

 

[davidbeach]

I doubt that you'll ever find a medium voltage manual transfer switch, and if you did who in their right mind would operate the thing? Two breakers, a PLC, and some good protective relays are what you need. And don't skimp on the commissioning.

 

[slavag]

Hi Vanskat.
1. Simple solution it's operator hand with procedure list.
2. You can build some logik with repeater relays.
3. Add PLC
4 And best solution, used,as say David, good relay with control(PLC) functionality.
Please take in account is not so simple, you need only one push button and system will decide what CB closed, what open, you need some switch for this mode, you need double feeding logik, etc.
Regards,
Slava

 

[ScottyUK]

vanskat,

At the risk of misinterpreting your application, would a 'ring main unit' be a suitable device? RMU's are pretty common on the UK utility distribution network at 'Tee' points where a a distribution transformer is connected to into an MV ring system. They usually incorporate one circuit breaker and two or more switches. RMU's aren't things I have had much to do with because I work in generation, not distribution, and all our gear is circuit breaker based.

Have a look at, for example, Schneider's Ringmaster C or their RM6 for examples.



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Sometimes I only open my mouth to swap feet...

 

[vanskat]

ok.. Guess I have to go with my gut on this one...Was really trying to avoid double breakers and logic.

Was hoping there was some old school device that could work. This assumption was based on an old Westinghouse 'versarupter' that i had glimpsed in a similar sort of configuration some time ago.

Thanks all

 

[apowerengr]

Pad-mounted switchgear? S&C (or others) PMH or PME say a 10 model w/ 4 - 600 amp switches and a common bus? I'm not clear on the configuration you are looking for but there's many options available including auto-transfer.

 

[davidbeach]

I'd be comfortable with the PHM (or PME) as break before make, but not the other way around. The fact that the two sources come from the same transformer removes much of the risk, but there are still too many things that can go wrong to have someone in that close to the equipment. Utility applications are one thing, but given the nature of the question I doubt this is utility. If it isn't utility what are the qualifications of the personnel doing the switching? What prevents closing a good line into a faulted line?

 

[jraef]

I agree. Lots of possibilities out there, but just how "manual" do you want it?

http://www.gwelec.com/product_padmount/pad_pvi.cfm

 

[davidbeach]

I'd want, at an absolute minimum, a sync check relay that could block the operation of the transfer switch. Open transition would be much less of a problem, though a bad open transition (fast, out of phase) could cause all sorts of problems with motor loads. Cheap is for small low voltage stuff; MV is too unforgiving to try to go cheap. Utilities will regularly do things that end users should never try; training, practice, and much better tools have a lot to do with the differences.

 

[vanskat]

Concerns noted. Not a utility application. This transfer may take place a few times per year. Operating personnel are electricians who would wear level 4 PPE.

In thinking about it, I may be forced to use some logic or interlocking mechanism to prevent closing into a fault which would be highly unlikely since both sources are off the same transformer.

Actually looked at some S&C products and pad mounted swgr. Will take all of the above into consideration. Was even thining about a bus tie arrangement!!!