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Examoogle • User • info@examoogle.com • EE-2024-8821
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Which angle of degree buchholz relay place in transformer?
3 to 4
5 to 7
4 to 6
7 to 8
5 to 7
The Buchholz relay is a gas-actuated protective device installed in oil-immersed transformers to detect incipient faults. To ensure the smooth collection of gases in the relay chamber and the proper operation of the mercury switches, the pipe connecting the main tank and the conservator is installed at an inclination of 5° to 7° relative to the horizontal.
The Buchholz relay is a gas-actuated protective device installed in oil-immersed transformers to detect incipient faults. To ensure the smooth collection of gases in the relay chamber and the proper operation of the mercury switches, the pipe connecting the main tank and the conservator is installed at an inclination of 5° to 7° relative to the horizontal.
Vgas=∫t1t2Afaultdt — Represents gas accumulation rate during an internal fault
θ∈[5°,7°] — Recommended installation slope for gravity-fed gas movement
The relay acts as a mechanical sensor for internal faults. When gas is generated due to localized overheating or an arc, it rises towards the conservator and gets trapped in the relay's upper chamber. The inclined mounting angle (5° to 7°) ensures that gas bubbles travel predictably toward the relay housing rather than accumulating elsewhere, allowing the float to drop and actuate the alarm or trip circuit effectively.
Installed in the pipe between the transformer main tank and the conservator.
Operates on gas accumulation (slow) and oil surge (fast).
Used exclusively in oil-immersed transformers equipped with a conservator tank.
Prevents major damage by isolating the transformer during incipient faults.
Detects incipient faults before they become catastrophic.
Simple mechanical construction and high reliability.
Only applicable to oil-filled transformers with conservators.
Can trigger false trips due to mechanical vibrations or air trapped during oil refilling.
Power transformers (>500 kVA).
Oil-filled distribution transformers with conservator tanks.
The 5° to 7° tilt is a standard engineering practice to guarantee that any gas generated is captured by the relay's upper float.
If the angle is too shallow, gas may pass by the relay; if too steep, it may create excessive mechanical stress on the pipe connection.
B is correct — The Buchholz relay should be installed at an inclination of 5° to 7° to the horizontal to ensure proper operation of the gas-collecting mechanism.
Always remember that Buchholz relays cannot be used on dry-type transformers, as they rely entirely on the decomposition of insulating oil to generate gas for operation.