2. 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 actuated
protection 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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4. 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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5. 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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11. BUCHHOLZ RELAY
PRINCIPLE
• Based on Mechanical phenomenon(Mechanically
actuated).
• Minor Internal Fault.
• Severe or Major types of Fault.
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12. MINOR INTERNAL FAULT
• Insulation fault between turns.
• Breakdown of core of transformer.
• Core heating.
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13. MAJOR OR SEVERE FAULT
• Short-circuit between phases.
• Short-circuit between phases to earth.
• Fault in tap changing equipment.
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14. 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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15. 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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16. OIL LEAKAGE
• Oil Air Float Mercury Alarm
• leakage bubbles switch energized
• Lower the Tilting the Alarm
• float switch contact
• closed
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17. 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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18. 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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19. 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
JULIUSALOWONLE
20. 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.
JULIUSALOWONLE
