The invention discloses a digital non-electric-quantity protection method for an oil-immersed
transformer based on pressure characteristics. The method comprises the following steps: firstly, when theoil-immersed
transformer runs, acquiring a pressure instantaneous value P(t) at an installation position of a
pressure sensor of the protected oil-immersed
transformer in real time, and starting a pressure
relay when the pressure instantaneous value P(t) is greater than a pressure
relay starting threshold value Pst; secondly, adopting different action strategies according to the pressure instantaneous value P(t): when the pressure instantaneous value P(t) is greater than a protection action No. 2 threshold value Pth_2, determining that a serious fault occurs in the oil-immersed transformer, instantaneously performing pressure protection, and
tripping off a
circuit breaker; when the pressure instantaneous value P(t) is greater than a protection action No.1 threshold value Pth_1 and less than the protection action No.2 threshold value Pth_2, continuing to judge whether P(t+
delta(t)) is still greater than the Pth_1 or not after time
delay delta(t), determining that the fault is an internal fault if the requirement is met, performing the pressure protection and
tripping off the
circuit breaker; otherwise, performing no operation of the pressure protection. The method can effectively distinguish the internal fault and the external disturbance state of the transformer, and improves the pressure protection reliability.