The present invention relates to a Buchholz relay (1) for the protection of oil insulated power electrical equipment, comprising: - a support frame (2) suitable to be in contact with the oil; - floating means (3) coupled with said support frame (2) and movable relative thereto; - switching means (4) operatively connected with said floating means (3) and suitable to enable/disable an alarm circuit and/or a trip circuit of said electrical equipment; - at least one flow vent device (5) coupled with said support frame (2) and operatively connected to said trip circuit, suitable to be affected by the oil flow and movable between a first position, in which the flow vent device (5) maintains said trip circuit disabled, and a second position, in which the flow vent device (5) enables said trip circuit; - contrast means (6) suitable to exert on the flow vent device (5) a contrast force suitable to maintain the flow vent device (5) in the first position until the oil flow speed does not exceed a predetermined oil flow speed threshold value, and to release the flow vent device (5) such that it reaches the second position when the oil flow speed exceeds said predetermined oil flow speed threshold value, The Buchholz relay (1) comprises a regulation device (19) suitable to act on the contrast means (6) and/or on the flow vent device (5) so to modify said contrast force.