Digital non-electrical protection method for oil-immersed transformers based on pressure characteristics

Abstract

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.

Description

technical field [0001] The invention belongs to the technical field of non-electricity protection of transformers, and in particular relates to a digital non-electricity protection method for oil-immersed transformers based on pressure characteristics. Background technique [0002] As important protection components of power transformers, gas protection and pressure protection have been used in conjunction with differential protection as the main protection of transformers. Compared with electrical quantity protection, traditional gas and pressure protection can more directly reflect non-electrical characteristics such as oil flow surge and pressure rise in faults in the transformer area, and has higher sensitivity and reliability in principle. However, unlike transformer electrical protection, non-electrical protection has not received the attention of the industry for a long time and has always been at the primary and backward level. Compared with transformer electrical p...

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Problems solved by technology

However, unlike transformer electrical quantity protection, non-electrical quantity protection has not received the attention of the industry for a long time and has always been at the primary and backward level

Compared with transformer electrical protection, the correct action rate of non-electrical protection is also at a low level. Due to the external short-circuit impact of the transformer, the gas protection of the main transformer has misoperation and tripped, and the oil injection accidents of the pressure relief valve have occurred frequently, which is harmful to the safe operation of the power grid. cause greater impact

[0003] At present, the main reasons for the low protection performance of non-electrical quantities are as follows: First, as a mechanical relay, its measurement accuracy of non-electrical action quantities reflecting the internal faults of the fuel tank is insufficient, and its performance is affected by the operating environment of the transformer and human factors. At the same time, the wear and aging of mechanical parts also affect its sensitivity; second, the setting calculation of mechanical relays is difficult, and the setting values ​​of gas relays installed on site are selected according to the test results and operating experience provided by the former Soviet Union in the 1950s. The correctness and rationality cannot be judged; thirdly, the transformer is only equipped with one non-electric relay of the same type and the installation position is fixed, but there is great randomness in the location and intensity of the fault inside the oil tank, and the distance between the fault point and the installation position of the relay is opposite to the non-electric relay. The action performance of the relay has a great influence; finally, the change process of the non-electrical fault characteristics before and after the internal fault of the fuel tank is extremely complicated, and its in-depth research and analysis is insufficient. is also an important reason

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