buchholz relay on transformer
TRANSCRIPT
BUCHHOLZ RELAY ON TRANSFORMER
BY
JULIUS TEMITOPE ALOWONLE
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INTRODUCTION• Buchholz relay in transformer is an oil container
housed the connecting pipe from the main tank to the conservator tank….www.electrical4u.com
• Buchholz relay is a type of oil and gas actuatedprotection relay mainly used on all oil immersed insulation transformer more than 500KVA...www.owlcation.com
• Buchholz relay is a gas-actuated relay installed in oil immersed transformers for protection against all kinds of fault…V.K MEHTA
• Buchholz relay is an oil immersed protective relay located between the connecting pipe of the conservator tank to the main tank, which energized an alarm circuit or trip circuit during transformer faulty conditions.
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BUCHHOLZ RELAY( INVENTED BY MAX BUCHHOLZ IN 1921)
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ELEMENTS OF BUCHHOLZ RELAY• UPPER ELEMENT-A hinged float i.e. moving up
and down depending upon the oil level in the Buchholz relay container.
• LOWER ELEMENT-A hinged float or A baffle plate i.e. in front of inlet (main tank side) of the transformer. Movement by oil pressure.
• MAIN ELEMENT-Gas release pockets or cocks (on top).
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ELEMENTS OF BUCHHOLZ RELAY• MERCURY SWITCH-Depends on the position of
the float(attached to the float).
• OIL SURGE DETECTOR OR FLAP -Detect an oil surge from the main tank to the conservator tank.
• ALARM-Initiate sound for fault attention.
• TRIP CIRCUIT-Actuate Circuit breaker isolation.
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INTERNAL DIAGRAM
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INTERNAL DIAGRAM
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INTERNAL DIAGRAM
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BUCHHOLZ RELAY
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BUCHHOLZ RELAY LOCATION
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BUCHHOLZ RELAY PRINCIPLE• Based on Mechanical phenomenon(Mechanically
actuated).
• Minor Internal Fault.
• Severe or Major types of Fault.
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MINOR INTERNAL FAULT
• Insulation fault between turns.
• Breakdown of core of transformer.
• Core heating.
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MAJOR OR SEVERE FAULT
• Short-circuit between phases.
• Short-circuit between phases to earth.
• Fault in tap changing equipment.
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MINOR FAULT
• Minor
• fault Gas Float Mercury Alarm
• switch energized
• Decomposition Lower the Tilting the Alarm
• of transformer float switch contact
• oil (hydrocarbon) closed
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MAJOR FAULT
• Major Baffle Mercury Trip Circuit
• fault plate switch circuit breaker
• Surge of Oil Tilting the Energized Opened
• the oil pressure switch LV & HV
• side
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OIL LEAKAGE
• Oil Air Float Mercury Alarm
• leakage bubbles switch energized
• Lower the Tilting the Alarm
• float switch contact
• closed
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FALSE OPERATIONS OF BUCHHOLZ RELAY• Buchholz relay operation may be actuated
without any fault in the transformer.
• OIL TOPPAGE-When oil is added to a transformer, air may get in together with oil, accumulate under the relay cover and thus cause false buchholz relay operation.
• Mechanical lock-is provided in the relay so that one can lock the movement of mercury switch when oil is topping up in the transformer and also during transportation of transformer.
• EXTERNAL FAULT-Over currents flowing through the winding cause over heated the copper and causes oil to expand. It increase the oil velocity which is sufficient to trip over the lower float.
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ADVANTAGES OF BUCHHOLZ RELAY• Buchholz relay prevent accidents during major
fault (isolate the transformer).
• Severity of the fault can be determined without dismantling the transformer (DGA).
• It trapped gases for bleeding.
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LIMITATIONS
• It can sense the fault occurring below oil level only. Therefore separate protection is needed for connecting cables.
• it is a time delay operating device (0.1 seconds and average of 0.2 operating range).
• it can only be used with oil immersed transformers equipped with conservator tanks
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REFERENCES
• 33/11KV 15MVA, Mangoro Injection Substation –IKEJAELECTRIC LAGOS.
• www.electrical4u.com
• www.wikipedia.org
• www.owlcation.com
• PRINCIPLE OF POWER SYSTEM BY V.K. MEHTA.
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