Oil-immersed transformer hot spot temperature evaluation method based on multi-parameter fusion

Abstract

The invention discloses an oil-immersed transformer hot spot temperature evaluation method based on multi-parameter fusion. The oil-immersed transformer hot spot temperature evaluation method includes the following steps of (1) according to the process of heat transfer inside the transformer, clarifying the definition and calculation method of the hot spot heat source and hot oil area of the transformer, and reducing the calculation bias caused by taking the overall winding as the hot spot heat source; (2) correcting the algorithm of the hot oil area thermal capacitance Cwo and the hot spot thermal capacitance Chs, and improving the accuracy of the time constant tau wo and the winding time constant tau hs and the dynamic response capability of the calculation model; and (3) establishing the dynamic calculation equation of hot spot temperature by considering the influence of time-varying ambient temperature and time-varying load on the hot spot temperature. When the dynamic equation of the model is deduced, the temperature characteristics of the load loss and oil viscosity are further considered, and the calculation result can more accurately reflect the temperature rise inside the transformer. The method can dynamically reflect the characteristics of the temperature change inside the transformer, and the calculation is simple and the accuracy is high.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of power transformer fault diagnosis, and in particular relates to a method for estimating the hot spot temperature of an oil-immersed transformer based on multi-parameter fusion. [0003] Background technique: [0004] The remaining life and load capacity of a transformer depend largely on its insulation characteristics. Excessively high winding hot spot temperature will accelerate the thermal aging of the transformer and the deterioration of winding insulation. Accurately obtaining the winding hot spot temperature is crucial to improving the economical efficiency of transformer operation and the safe operation of the power grid. level is important. [0005] At present, the mainstream methods to obtain the internal temperature of the transformer are direct measurement method and indirect calculation method. The direct measurement method requires pre-embedded sensors in the transformer. The advantage...

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Problems solved by technology

The direct measurement method requires pre-embedded sensors in the transformer. The advantage is that it can accurately measure the internal temperature of the transformer. However, the introduction of built-in sensors will cause problems such as difficult insulation treatment, complex fault maintenance and high cost, so it is rarely used in actual engineering.

The indirect calculation method generally adopts the calculation formula recommended by IEEE and IEC guidelines. This method is simple to calculate, but it does not consider the temperature characteristics of load loss and oil viscosity, as well as the dynamic influence of time-varying ambient temperature and time-varying load on hot spot temperature, and the calculation error bigger

In recent years, by introducing concepts such as lumped thermal resistance and thermal capacity, many foreign scholars have used the concept of thermal circuit to describe the internal heat transfer process of transformers and proposed a solution model for top oil temperature and hot spot temperature based on thermoelectric analogy. This method is simple and fast. Fast, but the existing methods do not subdivide the internal heat transfer process of the transformer, and the calculation results cannot reflect the actual temperature rise inside the transformer

Domestic scholars have optimized on this basis and established a hot spot temperature calculation model based on the bottom oil temperature, which has improved the calculation accuracy of the model to a certain extent, but did not consider the actual range of heat capacity in each model, resulting in heat capacity and time constants The calculated result is too large

Looking at the existing hot spot temperature calculation methods, there are still the following problems: (1) There is no clear definition of the hot oil area and the hot spot heat source, but the winding as a whole is directly regarded as the hot spot heat source, which leads to deviations in the calculated hot spot temperature rise ; (2) The actual range of heat capacity in each model is not considered, resulting in large calculation results of heat capacity and time constant; (3) The time-varying ambient temperature, time-varying load, oil viscosity and load loss in the actual operation of the transformer are not considered The dynamic influence of parameters on hot spot temperature leads to large errors in calculation results

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