Pressure change trend-based digital non-electric quantity protection method for oil-immersed transformers

Abstract

The invention discloses a pressure change trend-based digital non-electric quantity protection method for oil-immersed transformers. According to the method, when an oil-immersed transformer is operated, a pressure value P(t) at a measurement point of a protected oil-immersed transformer is acquired in real time, and judgement is carried out to decide whether to start a protection element or not according to the fact that whether the pressure instantaneous value P(t) at the measurement point achieves a protection starting threshold value Pst or not; if the protection element is started, a longpressure waveform of a data window with a T of 10ms is intercepted, and pressure change amounts DeltaPi at N sampling points in the data window are calculated in sequence; and statistical analysis iscarried out to obtain a number n of pressure change amounts DeltaPi which are positive values, and if n / N-1 is greater than 2 / 3, judgement is carried out to determine that the transformer has internal fault and the protection element acts. The method is capable of correctly distinguishing internal faults and external disturbances of oil-immersed transformers, so as to effectively avoid false action or action refuse of pressure protection elements.

Description

technical field [0001] The invention belongs to the technical field of transformer non-electricity protection, and in particular relates to a digital non-electricity protection method for oil-immersed transformers based on pressure variation trends. 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 prot...

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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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