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
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
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
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
RE: Buchholz / Sudden Pressure Relay
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
Regards
Marmite
RE: Buchholz / Sudden Pressure Relay
RE: Buchholz / Sudden Pressure 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
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
RE: Buchholz / Sudden Pressure Relay
RE: Buchholz / Sudden Pressure Relay
Regards
Marmite
RE: Buchholz / Sudden Pressure Relay
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
Regards
Marmite.
RE: Buchholz / Sudden Pressure Relay
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
RE: Buchholz / Sudden Pressure Relay
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
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!
RE: Buchholz / Sudden Pressure Relay
Is that common practice?
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(2B)+(2B)' ?
RE: Buchholz / Sudden Pressure Relay
Pete, that is the correct practice.
RE: Buchholz / Sudden Pressure Relay
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
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
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
Having seen that I'd fit two PRDs with flow directors rather than a single one without.
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If we learn from our mistakes I'm getting a great education!
RE: Buchholz / Sudden Pressure Relay
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
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
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!
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If we learn from our mistakes I'm getting a great education!
RE: Buchholz / Sudden Pressure Relay
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
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
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
RE: Buchholz / Sudden Pressure Relay
RE: Buchholz / Sudden Pressure Relay
RE: Buchholz / Sudden Pressure Relay
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
RE: Buchholz / Sudden Pressure Relay
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
RE: Buchholz / Sudden Pressure Relay
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
Archaic system is not equivalent to bad system
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.