Oil-immersed transformer digital non-electric quantity protection method based on pressure change quantity

Abstract

The invention discloses an oil-immersed transformer digital non-electric quantity protection method based on pressure change quantity; the method comprises the following steps that a relay starting threshold value Pst and a protection action threshold value Pth of a protected oil-immersed transformer are set before electrification; next, a signal acquisition device collects the pressure waveform on the wall of an oil tank in real time through a pressure sensor to obtain a pressure instantaneous value P(t) at a measuring point, and whether a pressure relay is started or not is judged by makingcomparison between the pressure instantaneous value P(t) and the relay starting threshold value Pst; if the pressure relay is started, the pressure waveform of data window length when T is equal to 10ms is intercepted from the start moment, and the pressure change quantity delta P is calculated; and finally, by making comparison between the pressure change quantity delta P and the protection action threshold value Pth, the internal state of the oil-immersed transformer is accurately identified. By adoption of the method, the internal faults and external disturbance of the oil-immersed transformer can be accurately distinguished, and misoperation or rejection of the pressure protection device is effectively avoided.

Description

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

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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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