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Buchholz / Sudden Pressure Relay
6

Buchholz / Sudden Pressure Relay

Buchholz / Sudden Pressure Relay

(OP)
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

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

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).  

RE: Buchholz / Sudden Pressure Relay

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.
 

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

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

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

2
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.

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

(OP)
OK, thank you all for your replies.

RE: Buchholz / Sudden Pressure Relay

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

RE: Buchholz / Sudden Pressure Relay

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

RE: Buchholz / Sudden Pressure Relay

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.  

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

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

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

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?

RE: Buchholz / Sudden Pressure Relay

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.
  

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

RE: Buchholz / Sudden Pressure Relay

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

=====================================
(2B)+(2B)'  ?

RE: Buchholz / Sudden Pressure Relay

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.

RE: Buchholz / Sudden Pressure Relay

prc, the selection of SPR vs Buchholz depends on the tank and ventilation configuration. Like Scotty said, SPR is used where you have a sealed tank. Buchholz is used with a conservator tank. The presence of the conservator tank reduces the overpressure caused by an internal fault by giving the oil someplace to go. This desensitizes the SPR, in some cases making it useless. The Buchholz detects the fault event by monitoring oil movement into the conservator.

One can work out the hydrodynamics and figure out which system would be quicker. But the selection is dictated by the tank ventilation system. There might be a high energy fault condition where adding an SPR to a conservator/Buchholz configuration would react to HE faults faster. But in most cases, the fault conditions are covered by the Buchholz. In sealed tanks, its SPR only as there is no place to put a Buchholz.

RE: Buchholz / Sudden Pressure Relay

I'm coming late to the party just to say thanks for the interesting and educational discussion on this topic.  I ran into a new transformer with a conservator that had both a Buchholz as well as a SPR, and I did not understand why this was done except that the transformer was built by a US manufacturer who does very few conservator units.

The explanation by PHovnanian makes sense to me, so now I won't worry too much about the SPR in this unit.  

FWIW, we specify that SPR or Buchholz relays be provided with a separate latching relay that must be reset at the transformer.  The latching relay contact is used to trip an electromechanical lockout relay directly.  

Cheers,

Dave

David Castor
www.cvoes.com

RE: Buchholz / Sudden Pressure Relay

Phovnanian,

Although I am an EE not a mechanical engineer I tried an online flow calculator for a 5 cm diameter 2 meter long conservator pipe. At 1400 kPA (200 PSI) the flow is only 100 liters/second.  With tank volumes ranging from 20,000 to 80,000 liters, I don't see how it would make much difference on the overall tank pressure.  At 1400 kPA, an SPR would react in approximately 1 cycle.  Is the advantage is the low energy fault detection where arcing might take multiple seconds?


We have also been installing pipes for directing the output of the pressure relief devices.  Now I see that might not be such a good idea after seeing it cut the flow from 6000 l/s to 1200 l/s just by adding 3 meters of pipe.
 

RE: Buchholz / Sudden Pressure Relay

Re. PRD shields and flow directors: if you have ever seen a PRD operate in anger you'll find it makes a reasonably effective atomising nozzle, like a giant diesel injector. I'm fairly sure that the fine spray generated by the PRD contributed to the flash fire immediately after a transformer explosion which killed three friends in 2001.

Having seen that I'd fit two PRDs with flow directors rather than a single one without.
  

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

RE: Buchholz / Sudden Pressure Relay

PHvonanian, my views are same as yours. Iam talking about only transformers with conservator where SPR makers are pushing it as an additional accessory.

When we provide SPR in open breathing transformmer, its response will be similar to PRD ie if the internal fault is nearer to SPR or PRD,it will pick up.So I consider Buchholz more reliable than SPR.Of course there are cases where Buchholz did not pick up with serious internal fault as the tank opened out releasing pressure and gas

Scotty,normally two PRDs are provided when oil content in transforer is more than 35-40 KL. It is provided on  opposite sides/corners to get maximum coverage.PRD shall be provided directly on tank or at end of short,direct pipe with out bends otherwise massive pressure wave will rupture tank before actuating PRD.But providing directing pipe on the outlet  of PRD is not going to affect the PRD operation.

RE: Buchholz / Sudden Pressure Relay

bacon4life, that's correct. An SPR will react quickly for a fault capable of producing on the order of 100 liters/second of gas. But if I recall correctly, Buchholz relays are sensitive to oil flow velocities on the order of cm/sec which will result from much lower rates of gas generation. At the low end of the scale, a Buchholz will trip for a slow oil leak (eventually).

Its probably true that an SPR will beat a Buchholz for a high energy fault, so if you've got one, you might as well hook it up.

RE: Buchholz / Sudden Pressure Relay

Hi prc,

There's a good photo somewhere on the Qualitrol website which shows how different the behaviour of the oil is when it vents directly as compared to through an oil director. The discharge from the director was turbulent liquid, where the direct venting was a fairly fine mist.

I'll have a look for it later - I'm off to beat the traffic I hope!
  

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

RE: Buchholz / Sudden Pressure Relay

Scotty,I believe oil director will not affect the flower like flow from PRD.Director pipe normally starts from the collection box covering the PRD outlet.

bacon4life,the pressure buildup is not uniform or slow.Recently I came across a failure in a 400Kv winding at site. An arc started at line end creeped over pressboard to neutral end.Since the transformer reactance was not in circuit a very high current -14 kA RMS as per recorder-flowed.At 400kV,it was very high energy release,The pressure wave with gas blasted the outer winding and came out hitting tank,causing tank side wall distortion/weld  rupture and PRD operation,but not Buchholz.Speed of response of SPR depends on how near to it is the actual fault point.

RE: Buchholz / Sudden Pressure Relay

@Peter: Buchholz Relay has two connections coming out from two different Mercury switches:
1. Buchholz Relay Alarm connection to ring the alarm in case of early detection of an incipient fault. This alarm connection comprises of two terminals which are connected to two terminals of a control cable. The two terminals of the control cable go into a control panel inside the Control room and gets connected to a Supervision Relay for Buchholz alarm. Once there is accumulation of gas inside the Buchholz relay (Due to a fault), the float of the mercury bulb switch goes down and so the mercury level inside the bulb rises in one end due to the slant. This mercury reaches a level where it can make contact for both the terminals of the Buchholz Alarm and so the circuit to ring the alarm is completed and the 36V DC (Generally in Asia) juice flows into the Supervision Alarm Relay which actuates the Master Supervision Relay for Alarm, which in turn supplies direct DC Volt or makes a contact to supply AC voltage to the Buzzer depending upon whether the Buzzer is DC operated or AC Operated.

2. Buchholz Relay Trip connection works exactly the same manner except that instead of connecting to the Buzzer the 36 V DC juice is fed into the Tripping coil of the circuit breaker, which operates the circuit breaker once the contact in the lower mercury bulb is made which activates the Supervision Buchholz Trip Relay which in turn actuates the Master Supervision Trip Relay which makes the DC juice to flow into the Tripping coil of the CB.

I have made a simplified diagram of the cicuit. Hope you can grasp it well from it. It is an attachment file.
 

RE: Buchholz / Sudden Pressure Relay

@Peter: Yes the above applies to the Marshal's Box as well... Marshal's Box has Two Indicators
1. OTI (Oil Temperature Indicator)
2. WTI (Winding Temperature Indicator)

Once the Temperature of the transformer oil increase beyond a certain pre-specified upper limit, contacts are made which completes the contact circuit for the same Supervision Alarm and Trip Relays in which Buchholz Unit is also installed and it operates in the same manner as Supervision Buchhol Relay operates because all these units are mounted in parallel on the same Relay i.e Supervision Alarm or Trip Relay which actuates a Master Alarm or Trip Relay...  

RE: Buchholz / Sudden Pressure Relay

@Peter: Buchholz Relay is always used to Isolate the transformer from the incoming supply.

RE: Buchholz / Sudden Pressure Relay

@Slavag: It depends upon the situation you are in... Generally Buchholz relay is used to operate the circuit breaker of the incoming line rather than "all CB's". If you want to trip all the circuit breakers that is fine, You need additional circuitry but that way the risk factor increases. Electrical Equipments can malfunction anytime even if they are from the best company. If the CB on the incoming side shows a sluggish response than the CB's on the load side, the load-side CB's will operate on full load resulting in a severe flash-over inside the Arc-Quenchers resulting in damage in the arc-quenchers or the CB contacts. So its better to operate one CB i.e on the Incoming line.

RE: Buchholz / Sudden Pressure Relay

@prc: Why is it necessary for the Temperature Indicators to operate LV only??? Can you please explain??

RE: Buchholz / Sudden Pressure Relay

Buchholz relays need to isolate faulty transformers from all points of infeed. I'm not going to comment on the twaddle about "flashover of arc quenchers".
Winding temperature trip operates the LV breaker because once you have shed the load on the winding you remove the cause of the overtemperature.
One of the design priniples of protection is that you only trip what is necessary to isolate the fault.
Regards
Marmite

RE: Buchholz / Sudden Pressure Relay

@Marmite: How about the rise in winding temperature being due to the internal fault i.e Inter-turn fault??? If you shed the load, the cause of the fault persists.  

RE: Buchholz / Sudden Pressure Relay

Hello.

As I saied before, our practic disconnect transformer from all sides in case of any "mechanical protection" ( Buchholtz, PRD, thermal, etc).
In additioanl, practic of lot of companies desconnect LV side by HV sided circuit breaker contact, its a wiring interlock/trip, but not via some LOR.

Buchholtz relay is protection (or special electrical protection)aginst inter-turn faults,a temperature monitor is very slow.

RE: Buchholz / Sudden Pressure Relay

Thanks Slavag... I must tell you that i belong to a very remote region of the World and we have a very classical system of Electric substations based of very archaic system of measurement, control and protection. So, not much exposure to latest equipments being used. I like the idea of tripping the CB's of outgoing feeders by the electromechanical mechanism of the tripping system of the incoming line CB. I can imagine what that could be like.

RE: Buchholz / Sudden Pressure Relay

Mubeenkhankashi,mercury switches are being phased out due to environmental concerns of mercury pollution.

Frankly high temperature trip is rarely or never used in practice.Internal faults will be cleared by fast acting relays rather than slow acting tempearture indicators.Remember time constant of oil temperature is 2-4 hours and that of winding is 4-10 minutes. Overload trip will be taken care by overcurrent relays rather than sluggish oil or winding temperature indicators.

RE: Buchholz / Sudden Pressure Relay

Hi Mubeenkhankashi.

Archaic system is not equivalent to bad system smile.
I was involved to few projects in few regions of the world: different logic of protection and control schemes, its some historical, expirience,etc issue.

 

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