Buchholz / Sudden Pressure Relay 6

[PeterS84]

Hi All,

Can you tell me how do you connect Buchholz/SPR to trip CB - do you connect it directly to the CB or do you connect it via IED's binary inputs (or both - in parallel)?
By the way - is there a difference between Buchholz and SPR?

Regards,
Peter

 

[PHovnanian]

How to connect: It depends on the configuration of your transformer installation. Under some circumstances you may want to trip breakers on both sides of the unit. So, connecting it to 'the CB' is only one possibility.

Buchholz and SPR: These use different methods monitoring a transformer. SPR can measure gas pressure at the top of a tank directly. Buchholz generally measures oil flow and levels between main and conservator tanks. While they overlap in their protection, each catches a somewhat different set of fault conditions.

 

[ThePunisher]

If you have a digital relay, connect it to one of it's input and add that to the trip logic.

In this way, you do not subject the bucholz contact to the trip coil or lockout relay coil inrush. Secondly, the relay will be able to log that trip into the relay and also to a remote monitoring facility (DCS).

 

[jghrist]

Traditionally in the USA, before IEDs, an auxiliary relay such as a GE HAA would be used. See Fig. 2. Schematic for application of HAA16B or HAA16C relay with transformer fault pressure relay in the HAA brochure

http://www.gedigitalenergy.com/products/brochures/haa.pdf.

 

[DTR2011]

Often, a qualitrol spr has form c contacts connected to a target, seal in type device, located in the transformer control cabinet.

I have seen this scheme successfully implemented with IEDs, typically the 87T device. There are definite advantages, as mentioned with SOE , fault reports.

 

[Marmite]

Our practice is to directly trip the transformer trip relay rather than routing via an opto input on a relay. The logic being that for a buchholz trip you want it to act as quickly as possible and as reliably as possible. The indication of buchholz trip goes back via the IED.
Regards
Marmite

 

[mgtrp]

Our practice was generally to trip directly (or via a common tripping relay where multiple outputs are required) on the theory that the Buchholz relay was a partial backup protection to the differential relay, and so should not trip via the protection relay. Trip flagging via optocoupler or similar in conjunction with a blocking diode in the trip circuit.

 

[prc]

Buchholz relay is a gas operated relay used in transformers with a conservator.It operates when gas generated inside transformer ( incipient fault)collects in it during the movement thorough connecting pipe to conservator.When gas generated is high( severe fault) oil surge occurs in the pipe between main tank and conservator actuating the tripping contacts of Buchholz relay.

Sudden pressure relay was developed for use in nitrogen sealed transformers with out conservators.It operates when there is a sudden change of pressure consequent to an inside fault.It can be fitted in gas space or oil space - on the top of tank or side of transformer tank.

 

[slavag]

Its depend on the application, depend on the number of trip coils.
unpossible connect directly to CB, contact of Buh. relay is not sutable for switching 220V DC ( 125V DC too).

its depend how much protective terminals and DC's.
if you have only one terminal and connect to terminal Buh relay ..its all eggs in one bascket...not correct, if you have two terminals and connect to both of them, is not bad solution.
in lot of cases, simple solution, connect "mechanical protections" to some LOR with lot of contacts.

 

[PeterS84]

OK, thank you all for your replies.

 

[PeterS84]

Does everything said above apply to thermostats (internal to the transformer) as well?

 

[Marmite]

You only need to trip the LV circuit breaker for over temperature and the operation is not as critical as for a Buchholz trip, as the risk is gradual loss of life of the transformer rather than rapid destruction of the transformer and potentially catastrophic fire. However if you have an LV trip relay I can't see why you wouldn't want to trip it directly rather than via an IED.
Regards
Marmite

 

[slavag]

Marmite, sorry, but Im not agree with you.
From my point of view, any "mechanical" protection installed on the transformer must trip all CBs.
Overtemperture, SPR, Buchholtz, Oil temperture can opearated without load and with LV CB is opened.

 

[Marmite]

I respect your opinion as always, Slava. UK practice is to trip only the LV circuit breaker for winding over temperature. Buchhholz, yes of course trip both HV & LV.
Regards
Marmite.

 

[rasevskii]

The Buchholz relays that I was familiar with had a tripping contact actuated by a surge flow in the conservator pipe (as prc says) and also an alarm contact actuated by a float which signalled a small flow of gases into the chamber, which could be vented/reset by a test cock.

On thermometers the usual one was made by Kihlstrom and had usually four mercury switches settable for: Fan 1, Fan 2, Alarm, and trip.

rasevskii

 

[westex]

We trip a 86LOR. That way when and if you take the digital relay (SEL-587) out of service you still have sudden pressure protection. We use a QUALITROL 909 Seal-in relay so it more secure tripping (one contact has to open and the other has to close to close the trip contact on the 909). Also the 86LOR can not be reset untill a person goes out to the transformer to hit the reset button on the 909. I sat in a class from SEL and they said your ultimate transformer protection is the SPR not there diff relay!! Thats why we trip the LOR directly and not go into a relay input.

 

[prc]

I agree with marmite. Temperature indictaors need to trip only LV breaker.
What is LOR and 86 LOR? When there is Buchholz Relay, is it necessary to have a SPR additionally? What is the practice in US and Europe?

 

[ScottyUK]

prc,


LOR - lockout relay
86 - ANSI code for trip & lockout function
86 LOR - probably to distinguish it from a software implementation of the 86 function.

Sudden pressure relays are employed on hermetic transformers, normally on the top plate above the gas space. A Buchholz relay is always employed with a conservator type transformer. It is probably possible to use an SPR with a conservator type in addition to a Buchholz relay, but I've never seen it. I wouldn't use one in lieu of a Buchholz relay.


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

 

[electricpete]

Our sudden pressure relays are wired for 1/2 alarm, 2/2 trip.
Is that common practice?

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(2B)+(2B)' ?

 

[prc]

Thank you scotty.My view is SPR has no advantage over time proven Buchholz and there is no purpose in providing it over and above Buchholz.Several years back,one major Indian utility was specifying SPR(under oil) in addition to Buchholz,presumably under the advice of some US consultants.Later they discontinued it.Now I find a new push( from commercial interests)proposing SPR in addition to Buchholz claiming it to be more faster,reliable!

Pete, that is the correct practice.