油浸式变压器绕组热点温度计算的热路模型

Thermal Model for Hot Spot Temperature Calculation in Oil-immersed Transformers

油浸式变压器是电力系统中的核心设备之一。变压器在温升过程中温度分布不均,热点温度是其中具有代表性的确定变压器最优化负载的重要参数。热点温度可由GB/T15164-1994中提出的基于变压器顶层油温的计算方法计算求出,但该方法在变压器暂态过载状态下的计算结果不够准确,因此根据IEEEStdC57.91的An-nexG中提出的可改进该计算精度的热点温度组成关系,建立了一个基于底层油温的等效热路模型。此模型由3个简化的能够分别表征热点温度与特征点油温的子模型组成。该热路模型的有效性通过与自行设计的ONAN,100kVA/5kV试验变压器的温升试验数据对比得到了验证,其计算结果与负载导则提出的热点温度计算公式的结果进行了比较,能够得到较好的计算结果。说明基于底层油温的变压器热点热路模型的有效可行。

Oil-immersed transformers are key components in power systems. The inordinate temperature rise in oil- immersed transformers, is featured by hot spot temperature （HST）. HST is an important parameter to determine the optimum load ability of transformers. A procedure to calculate HST is recommended by GB/T 15164-94 as an easy approach, yet it is not accurate in predicting the HST in the transient state and overload State. We put forward an equivalent bottom oil temperature （BOT） thermal circuit model based on the IEEE Std C57.91 Annex G that improves the transient state and overload state prediction. The model is composed of three thermal circuits revealing the relationship between HST and featured oil temperatures. The model is proved to be effective by comparing the calculation results of the thermal model and measured data obtained from heat run tests of an ONAN, 100kVA/5kV test transformer. Finally, the results from this model are comfared with GB/T 15164-1994 loading guide method resuits. The comparison proves the model presented is adequate and the method of using bottom oil temperature in thermal circuit is effective.